Geology and Mineral Resources of India

GOVERNMENT OF INDIA

MISCELLANEOUS PUBLICATION NO. 30, PART-XXII GEOLOGY AND MINERAL RESOURCES OF INDIA 2009

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GEOLOGICAL SURVEY OF INDIA Miscellaneous Publication No. 30 Part – XXII CONTENTS

Page No

GEOLOGY OF INDIA

1 1 2 5 5 5 9 10 14 15 19 21 26 27 28 29 32 37 42 43 43 46 47 48 49 50 51 51 54 78 89 130 131 135 137 138 139 140 140 141

COVER PAGE INTRODUCTION PENINSULAR INDIA INTRODUCTION DHARWAR CRATON TRANSITION ZONE SOUTHERN GRANULITE TERRAIN EASTERN GHATS MOBILE BELT EASTERN INDIAN CRATON CENTRAL PRECAMBRIAN SHIELD BASTER CRATON BUNDELKHAND CRATON

WESTERN PRECAMBRIAN SHIELD

BGC ARAVALLI-DELHI MOBILE BELTS

PURANA BASINS GONDWANA BASINS DECCAN TRAP VOLCANISM

INDO-GANGETIC-BRAHMAPUTRA PLAIN EXTRA-PENINSULAR INDIA ARUNACHAL HIMALAYA CENOZOIC FORMATIONS QUATERNARY FORMATIONS Andaman Nicobar Islands Lakshwadeep Islands

MINERAL RESOURCES OF INDIA Introduction DIAMOND GOLD BASE METALS BARYTE PGE and CHROMITE IRON ORE MANGANESE MOLYBDENUM TIN, TUNGSTEN URANIUM BAUXITE NON-METALLIC and INDUSTRIAL MINERALS

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Magnesite Limestone Apatite & Rock Phosphate/Phosphatic Nodules Asbestos

141 142 143 144 144 144 145 147 147 148 148 149

Borax

Stibnite Fossil Fuel Graphite Ilmenite,Rutile, Monazite and Garnet sands Gypsum Apatite Precious and Semi-precious Stones

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GEOLOGY OF INDIA INTRODUCTION India extends for about 3200 km from north to south and 2900 km from west to east and is located between latitudes 6o 45′ North at Indira Point, southernmost tip of the Great Nicobar Island and also the southernmost point of land in the territory of India, to little above 370 North and longitudes 68o East to 97o East. India has a diverse geology with different rock types representing the complete spectrum ranging in age from some of

the oldest Archaean metamorphites/granitoids to the

youngest Quaternary alluvium. Indian sub-continent is tectonically and physiographically divided into three broad domains i.e. the Peninsular India, the Extra-Peninsular India and the Indo-Gangetic Brahmaputra Plains. Indo-Gangetic plain is sandwiched between the Precambrian rocks of the Peninsular India and the highly deformed suites of the Himalaya of Extra-Peninsular India. Physiographically, Peninsular India is constituted of vast plateaus and mountains. The most important mountain ranges of the Peninsula are The Western Ghats (Sahyadri), the Satpura Range, the Aravalli Range, the Vindhyan Range and the Eastern Ghats. The major plateaus of Peninsular India are the Deccan, Malwa, Bundelkhand and Chhotanagpur of which Deccan is the largest. The major rivers that originate in Peninsular India are Chambal and Son in the north, Damodar in the east, Tapti and Narmada in the west and Godavari, Krishna and Cauvery in the south. Except for Tapti and Narmada which flow westerly into Arabian Sea, all rivers drain into the Bay of Bengal. The Plateau of Peninsular India is surrounded by coastal plains of Arabian Sea on the west and Bay of Bengal to the east. The east and west coasts meet at the southern tip of Peninsula bordered by the Indian Ocean. The Indian Republic includes two groups of islands – The Lakshwadeep Islands in Arabian Sea and Andaman Nicobar Islands in the Bay of Bengal. The Himalayan Mountain Ranges-extend for about 2500 km (with an average width of about 240 km) all along the northern borders of the Indian sub-continent from Jammu and Kashmir in the west to Arunachal Pradesh in east-form the Extra-Peninsular Region. Himalaya is broadly divided into (i) Siwaliks (ii) Lesser Himalaya (iii) Higher Himalaya and (iv) Tethyan or Trans-Himalaya across its length. The major rivers originating from the great Himalayan mountain ranges are the Indus, Ganges and Brahmaputra.

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The average elevation of the Indo-Gangetic-Brahmaputra plain lying between Peninsular and Extra-Peninsular India 150 m with a low gradient of almost zero level at the Sunderbans Delta of Bengal to about 300 m in the Upper Ganga plain of Punjab. PENINSULAR INDIA Peninsular India, the main repository of economic minerals, exposes rock units of almost entire spectrum of geological era. Remnants of Archaean sialic crust, preserved only in isolated small patches along with the oldest supracrustals are recorded from south, east, central and western parts of the country.

These Achaean nuclei are later accreted with the fold belt sequence, which

transgresses well within the Proterozoic, and display some tectono- magmatic episodes. The middle to upper part of the Proterozoic era (Meso- to Neo- Proterozoic) is mainly characterized by the development of major intracratonic basins (namely Cuddapah, Godavari, Indravati, Chhattisgarh, Vindhyan etc.).Gondwana rocks spanning between late Paleozoic and Mesozoic period. These litho packages are developed in faulted graben. The evidences of marine transgression during Mezozoic era are well documented both in the East and West Coasts. However, the most spectacular event of this era is the Deccan volcanism which covers vast tracts of western, central and southern India. Temporally comparable volcanic events Rajmahal and Sylhet traps along with oldest volcanic event (Panjal traps) are recorded from the eastern and northren part respectively. Compared to the earlier geological periods, Tertiary era is not well represented. It is preserved only in small isolated basins in Southern, Eastern and North eastern parts of the region. However, both temporal and spatial development of Quaternary sequences are well documented throughout the country including its coastal tracts. INDO – GANGETIC BRAHMAPUTRA PLAIN The tectonic trough sandwiched between peninsular shield in the south and Himalayan Mountains in north formed due to the upliftment of the Himalaya, has been filled up by the sediments derived from both sides, especially from Himalaya by rivers like Ganges, Brahmaputra and Indus and has been termed as Indo-Gangetic-Brahmaputra alluvial plain and stretches across northern India from Assam and Bengal in the east through Bihar and U.P. to Punjab on the west.

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EXTRA-PENINSULAR REGION The Himalayan mountain chain occurring all along northern part of India can be divided into four contrasting longitudinal litho-cum-morphotectonic belts from south to north, viz. i) Foot hill belt ii) Main Himalayan belt iii) Indus-Shyok belt and iv) Karakoram belt. The foothill Himalaya is a 10- to 50- km- wide belt of Miocene to Recent Molasse belt of Siwalik and other foothills comprising the Subathu, Murree with the Siwaliks resting on the Proterozoic component of the Indian Shield. This is followed to the north by Main Himalayan belt, comprising Lesser and Higher Himalaya, represented by sizeable portion of the geological sequences of Proterozoic age with Phanerozoic cover of varying thickness in different parts.The foothill Himalaya is overlain by alluvium and separated from the Lesser Himalaya by the north dipping fault commonly known as the Main Boundary Fault (MBF) or the Main Boundary Thrust (MBT) in Garhwal, Kumaon, Nepal, Darjeeling, Bhutan and Arunachal Pradesh Himalaya and known as the Krol Thrust in eastern Himachal Pradesh and Murree Thrust in Jammu area. This belt is involved in western syntaxial bend of the Himalaya. The Main Frontal Thrust (MFT) limits the margins of the Siwalik Zone against the Ganga Plains. The Lesser Himalaya is 60 to 80 km wide and is a discontinuous belt stretching between the MBT in the south and the Main Central Thrust (MCT) in the north. It consists of autochthonous late Proterozoic sediments, thrust over by three vast nappes that are built up successively of Palaeozoic sediments, Precambrian epi-metamorphics and mesograde metasediments. The epi-metamorphic and meso-metamorphic nappes throughout their extent are characterized by early Proterozoic (≈ 1900 Ma) and Early Palaeozoic granitic bodies of large dimension. The MCT separates the Lesser Himalaya from the Higher Himalaya to its north.The Higher Himalaya marks the region of highest peaks of Himalaya (Nunkun, Leopargial, Kedarnath, Badrinath, Nanda Devi, Api, Dhaulagiri, Everest, Kanchanjunga), made up of 10-15- km- thick Precambrian crystallines exhumed up and intruded by granites, some of which are Tertiary in age. The Indus Shyok belt/the Tethys Himalaya extends to the south of the Trans-Himalayan Karakoram belt and comprises ophiolite mélange (Indus ophiolite and associated formation) and plutonic rocks (Ladakh granitoid complex) of the Indus Shyok belt. These predominantly fossiliferous sediments range in age from late Proterozoic to Eocene. Sporadic occurrence of chromite have been reported from the ultrabasic rocks associated with Dras volcancs from Ophioleite-Melange zone.

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Karakoram belt, the northernmost zone comprises Palaeozoic and Mesozoic sedimentary sequences on a metamorphic basement of unknown age. This Trans-Himalayan belt lies to the north of the Indus Suture Zone in Ladakh region and extends eastward into Tibet. No important mineral occurrence is known from this belt. The different tectonic domains as depicted above are enumerated in detail in the following pages with emphasis mainly on the potential mineral occurrences in India. Keeping mineralization aspect in view, geology of Tertiary and Quaternary Period are not described in detail.

PENINSULAR INDIA The geology of Peninsular India constituting different Archaean cratons- Dharwar, Bastar, Singhbhum, Aravalli and Bundelkhand several mobile belts like Southen Granulite Teranin, Eastern Ghats, Satpura, Delhi etc. Proterozoic sedimentary basins, Gondwana troughs, Deccan Trap and the younger sedimentary basins is discussed below with a brief note on the stratigraphic locales, treated regionwise with major tectonics. Prognastic mineralised sectors are described in detail for future investigation and associated mining. DHARWAR CRATON The Dharwar Craton is essentially covered by the States of Karnataka and Andhra Pradesh. The Dharwar craton is a typical Archaean granite-greenstone terrane with a gneissic basement of tonalite-trondhjemite-granodiorite (TTG) composition known as Peninsular Gneiss. The granitegreenstone terrain exposes rocks older than 2500 Ma. It is bounded by Southern Granulite Terrain (SGT) to the south and Eastern Ghats Mobile Belt (EGMB) to the east, Arabian sea to the west, northwest-southeast trending Godavari Graben to the northeast and to the north with Deccan trap cover. The Dharwar Craton is divided into two sub-provinces – Eastern Dharwar Craton (EDC) and Western Dharwar Craton (WDC) with Chitradurga Boundary Fault located along the eastern margin of the Chitradurga schist belt as the boundary between them (Swami Nath et al., 1976; Drury et al., 1984; Chadwick et al., 2000). Some workers believe that the Closepet Granite, which is located ~50 km east of the Chitradurga Boundary Fault represents the boundary between the EDC and WDC (Naqvi and Rogers, 1987; Gupta et al., 2003; Moyen et al., 2003). Although the actual boundary between the two cratonic blocks remains debatable there are notable differences in lithology and metamorphism of the two blocks. The WDC is dominantly occupied by TTG gneisses (3.0 – 3.4 Ga) with minor schist belts of Sargur age (3.0 – 3.3 Ga), major schist belts of Dharwar age (2.9 – 2.6 Ga)

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containing predominant platformal sediments, and a few late Archaean granitoid plutons dated in the range of 2.60 to 2.65 Ga (Jayananda et al., 2006 and references therein). On the other hand, the EDC is characterised by voluminous late Archaean granitoids (2. 51 – 2.75 Ga) (the “Dharwar batholith” of Chadwick et al., 1996, 2000) with minor TTG gneisses and thin volcanics-dominated schist belts of Dharwar age. The Western Block of the craton comprises large schist belts (Dharwar type) accumulated in distinct sedimentary basins and the Eastern Block is characterized by voluminous juvenile granites and remobilised gneiss with remnants of schist belts (Kolar type). The schist belts in the craton are metamorphosed under greenschist to amphibolite facies conditions. The profusion of granitoids is responsible for low-pressure high Temperature metamorphism (andalusite-sillimanite type) in the EDC in contrast to the intermediate- pressure regional metamorphism (kyanite-sillimanite type) in the WDC. The southern part of the craton exhibits a transition zone from low- to high-grade rocks. The abundance of younger granites in the north and granulites in the south distinguishes the Eastern block as a reactivated zone of mobilized gneisses and granites around the centrally located Archaean nucleus (Western Block). The Chitradurga schist belt of Western Karnataka is one of the longest greenstone belts showing several phases of deformation (Radhakrishna and Vaidyanathan, 1997). The major part of Dharwar craton is covered by an extensive group of grey gneisses designated as “Peninsular Gneiss” which was further divided into older (Peninsular Gneiss-I) and younger (Peninsular Gneiss-II) based on isotopic age data (Beckinsale et al.,1980; Meen et al.,1992; Nutman et al.,1992). These gneisses contain enclaves of deformed and metamorphosed amphibolitic-and granulitic-grade rocks indicating the existence of an older group of sediments and associated igneous intrusives and are referred to as Sargur Group or ancient supracrustals. The lithological types include fuchsite quartzite with layers of chromite and barite, biotite schists with garnet, kyanite, sillimanite, cordierite, corundum, staurolite, marbles and calc-silicate rocks, serpentinised komatiites, banded iron formation and chromite-bearing ultramafic complexes. Peninsular Gneiss-I consists mainly of amphibolite-facies gneisses of tonalitic-trondhjemitic – granodioritic composition (TTG) with four major components, namely, (i) a layered and banded complex consisting of quartzofeldspathic biotite gneiss alternating with amphibolites and ultramafic material, (ii) banded hornblende-biotite migmatitic gneiss, (iii) banded migmatitic garnet-bearing paragneiss and (iv) homogeneous trondhjemitic-granitic plutons. These gneisses act as the basement for a widespread belt of schists.

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Peninsular Gneiss-II is comprised mainly of gneissic rocks with granodioritic and granitic composition, representing remobilised parts of an older crust with abundant younger granites and is found in the eastern parts of the Karnataka State. The prominent schist belts of craton in Karnataka are grouped and describe under the Dharwar Supergroup which is divided into two groups-the older Bababudan Group (2.8GA) compising orthoquartite, metabasalt and magnetite rich Banded Iron Formation. Overlying this is a more extensive Chitradurga Group(2.6GA) composed of schistose rocks, largely sedimentary in character, comprising conglomerates, quartzite, limestone, Ingladal volcanics, greywacke and associated manganiferous and ferruginous chert. The youngest series of sediments, mostly greywackes in composition and intercalated with cherty iron formation is represented by “Ranibennur Formation”, which occupies the topmost formation within the Chitradurga Group (Radhakrishna and Vaidyanathan, 1997). The end of the Dharwar Cycle is marked by“Closepet Granite” represented by granitic intrusion in a narrow belt 50 km wide. This belt of younger potassic granites mark a major geosuture or joining between two distinct crustal blocks, western block with a number of welldeveloped low-grade granite-greenstone belts with iron and manganese ores and eastern block marked mainly by younger gneiss of granitic and granodioritic composition enclosing a number of narrow linear bands of auriferous schist belts. Collision of the two blocks has resulted in the emplacement of granites along the line of junction of the two blocks (Radhakrishna and Vaidyanathan, op.cit). Besides, there are other isolated masses of younger granites outcropping away from these linearly disposed granites like those of Chitradurga, Arsikere and Banawar in the west and Patna, Torangal, Bellary and Raichur in the east. More than 60% of the State of Andhra Pradesh makes up the eastern part of the Dharwar craton and 10% of this cratonic part is covered by rocks of the Proterozoic platformal basins viz., the Cuddapah, Pakhal and Bhima. The major part of Andhra Pradesh is covered by“Peninsular Gneiss”. The different units of the Peninsular Gneissic Complex includes three discrete units based on composition, structure and mutual relations viz. (i) gneissic rocks, (ii) hornblende-bearing granitoids and (iii) younger granites. In the northern part, different units of the Peninsular Gneiss and the younger K-rich granites are described as the ‘Granitoid-Migmatite Complex’ (Naqvi and Rogers, 1987). The supracrustal rocks from Andhra Pradesh occur in the cratonic part and in the marginal zone with marked similarities to the Kolar-type schist belts of the Karnataka State and are composed

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of matabasalt, mata-acid volcanics, volcanicconglomerate and minor BIF. The Nellore Schist Belt is with Subordinate representation of meta sedminents. Three prominent greenstone belts occur in the southern part of the State with discontinuous trace of the belts into the adjoining parts of Karnataka State viz. (i) the Veligallu – Gadwal belt, (ii) the South Kolar or Bisanattam – Kadiri belt and (iii) the Ramagiri –Penakacherla belt. The Dharwar granite-greenstone terrane shows effects of three phases of deformation (Naha et al., 1986). While the earlier two deformations gave rise to the NNW-SSE to NW-SE- trending penetrative fabric marked by the general schistosity, and major faults and shears parallel to it, the third produced broad warps along E-W to ENE-WSW-trending axes. The terrane is affected by NNW-SSE to NW-SE-trending transcrustal faults/shears which are intersected by major ENE-WSW to E-W and NE-SW-trending faults/lineaments. According to a structural model of the Dharwar craton, the WDC represents a major synclinorium, while the EDC represents a major anticlinorium, the limb portion of which is occupied by the Closepet Granite. After granate emplacemena the Craton attained rigidity and later magmatic events like mafic dyke activity and Kimberlite activity is along the deep crustal faults/fractures. The generalized stratigraphic sequence pertaining to the granite-greenstone terrane of Dharwar craton is shown in Table 1. Table 1. Major Rock Types Kimberlite Puranabasans Maficdyke Potassic granites Greywackes Manganese marker horizon,

Group Cuddapah, Kaladgi, Bhima Younger granites

Age 1800MA 2000MA 2600 Ma

Era PROTEROJIC LATE ARCHAEAN

Felsic Complex (Cu) Iron Formation (Au,Fe,Mn) Younger Greenstones ARCHAEAN

Limestone Mafic volcanics Oligomict conglomerate

Mafic – ultramafic rocks Ancient supracrustal rocks Mafic? Felsic rocks

(Cu, Zn, As, Sb) (Au, U) Peninsular Gneiss 3000 Ma (beryl, columbite, tantalite, Li mica) Older Greenstones Kolar Group 3300 – 3000 Ma (Au, Ag, Cu, W) Sargur group Older gneisses 3300 Ma BASE NOT IDENTIFIED

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ARCHAEAN

ARCHAEAN

ARCHAEAN

The linear belts of oldest supracrustal rocks (Sargur, Nuggihalli, Sathyamangalam and Wynad) in this region are mainly represented by intercalated sequences of sediments and volcanogenic assemblages, which are the locales of deposition of minerals. Important deposits within these belts are Gold deposit of Kolar, Ramagiri-Penakacherla, Hutti, Maski, Gadag, Raichur and Wynad schist belt of Kerala; Magnetite quartzite of the Sargur belt of Karnataka. Within the Peninsular

Gneiss

and

platformal

sediments

of

Proterozoic

age,

the

diamondiferous

kimberlite/lamproite bodies intrude. Kimberlites and lamproites, host rocks for diamonds are distributed in the States of Andhra Pradesh and Karnataka, in the eastern tectonic block of Dharwar Craton (EDC) which was stabilised by ~ 2500 Ma. EDC hosts these bodies along or at the intersection of the post-Cuddapah reactivated ENE-WSW and NW-SE fracture / fault systems and / or at the closure of domal structures. The geological milieu (granite-gneiss of PGC) and tectonic setup favoured emplacement of more than 65 kimberlites and 46 lamproites. Kimberlites discovered in southern India till now are restricted to the EDC and are distributed in four kimberlite fields, viz. Wajrakarur Kimberlite Field (WKF), Narayanpet Kimberlite Field (NKF), Tungabhadra Kimberlite Field (TKF) and Raichur Kimberlite Field (RKF) while lamproites occur in two fields, viz. Ramadugu and Krishna. Gold, iron, manganese and titaniferous-vanadiferous magnetite deposits are reported from the schist belts of Gadwal, Chitradurga, Holenarsipur, Khammam and Nellore. TRANSITION ZONE The Marginal Transitional Zone (MTZ) occurs between the Dharwar craton to the west and the Eastern Ghat Mobile Belt in the east and is made up of granite gneiss and supracrustal rocks, reworked and overprinted by younger deformational events. The schistose rocks of the Nellore – Khammam belt, trending parallel to the East Coast occupies the transition zone along the eastern margin of the craton. Recent studies brought to light the existence of Kandra Ophiolite Complex in southern part of Nellore schist belt. Close to the vicinity of eastern margin of Cuddapah basin a number of granite bodies occur within the schistose rocks of Nellore schist belt. This zone is underlain by Archaean schistose and granitic rocks and was intensely reactivated during the Middle to Late Proterozoic periods. As a result, the MTZ, the eastern margin of the Cuddapah basin and the EGMB know as Prakasam Alkaline Province (Leenandam 1980) the locie of igneous activity with the emplacement of anorthosites all along the mobile belt, alkaline and subalkaline plutons close to the western margin of the mobile belt, syenite and granite close to the eastern margin of the Cuddapah basin. The well-known Kunavaram alkaline complex occurs within

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the MTZ. Alkali syenite and related granites also occur outside the province. The world famous mica (muscovite) mines at Gudur are located in the Nellore Schist belt. SOUTHERN GRANULITE TERRAIN The Southern Granulite Terrane (SGT) is to the south of the Dharwar craton having a gradational boundary difined by the Fermor Line. The SGT is amalgamated to the Proterozoic pandian granulite belt along Palghat-Cauvery shear zone.

The SGT is mainly exposed in the States of Tamil Nadu, Kerala and southern part of Karnataka comprising the Coorg Biligirirangan hills granulite belt of Karnataka in the north and the Nilgiri Madras granulite belt of Tamil Nadu in the south divided by the Moyar shear zone. This Proterozoic terrain comprises the northern Periyar-Madurai granulite belt (Chetty, 1996; Yoshida et al., 1996), also referred to as the Madurai Block (Harris and Santosh,1993) with intercalated charnockite (charnockitic massifs of Nilgiri hills, Kollimalai and Pachchamalai hills along Cauvery shear zone) and metasedimentary (pelitic) sequence and the southern Kerala Khondalite belt. Other major rock units along the Cauvery shear zone,considered as ancient suture (Gopalakrishnan et al., 1990; Viswanathan et al., 1990), includes sheared charnockitic and migmatitic gneisses intruded by layered anothositic rocks around Bhavani and Sittampundi. It also consists mainly of high-grade remnants of greenstone belts (Sathyamangalam Group) along with supracrustal enclaves of the mobile belt, namely, quartzites, pelites. The Palghat shear zone is represented by a distinct geomorphic expression, a physiographic low, bounded by Nilgiri hills in the north and Anaimalai and Palni ranges in the south. The dominant rock types along the shear zone include migmatitic gneisses and banded charnockites. Achankovil shear zone is another major shear zone exposed in the southern tip of SGT. The regional fabric and fold patterns around Kodaikanal and Madurai blocks are abruptly truncated at this zone (Narayanaswamy and Purnalakshmi, 1967). Sporadic lenses of ultrabasic rocks occur within the garnetiferous granitic gneisses. In the southern flank of the Palghat gap, up to the north of the Achankovil shear zone, the rocks are predominantly charnockites, charnockitic gneisses and other gneisses with occasional assemblages of metasediments in the Idukki-Munnar region representing the western continuation of the Madurai block in Tamil Nadu. Within the southern part of the Palghat gap, charnockitic patches and hornblende-biotite gneisses predominate. Towards the central and the northern parts of the gap, migmatitic gneisses (hornblende-biotite gneisses) and patches of amphibolites, calc-granulites and

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granites are exposed. Northern flank of the gap consists of a metasedimentary sequence of khondalite and calc-granulite with crystalline limestone bands. Granulites, schists and gneisses, intruded by acid and alkaline plutons, constitute the northernmost parts of the State. Sporadic late Archaean – early Proterozoic granites and associated pegmatites as also Mesozoic-Cenozoic dykes intrude these rocks. The Kerala region is an important segment of the SGT, where major units of the Archaean continental crust, such as granulites, granites, gneisses and greenstones are preserved. Southern part of the State, south of Achankovil shear zone, exposes an assemblage of migmatised metasedimentary and meta-igneous rocks (khondalite-charnockite assemblages). The southern tip of the Peninsula is represented by the Nagercoil Charnockitic massif (or the Nagercoil block), a distinctly charnockitic unit with metasedimentary intercalations. Several intrusive igneous bodies of distinctive petrological and petrochemical attributes of Proterozoic age occur amidst the granulites, Sittampundi, Torappadi, Thenmudianur, and Mamandur in Tamil Nadu and Ezhimala gabbro-granophyre Complex, Perinthatta anorthosite and Adakkathodu gabbro in Kerala; Alkaline magmatism is recorded in the form of several syenite-carbonatite bodies. The alkaline-related plutonism was widespread in the north in parts of Vellore, Dharmapuri and Salem Districts, where a number of ultramafic-syenite-carbonatite bodies of Elagiri, Koratti, Samalpatti and Pakkanadu occur in a NNE-SSW-trending zone extending from Gudiyattam in the north to Bhavani in the south over about 200km. Besides these silica-saturated alkali plutons, there are two bodies of silica-undersaturated syenite complexes, namely the Pikkili and the Sivamalai syenites. In contrast to the saturated syenites, these bodies are devoid of carbonatite association and are characterized by pyroxene syenite, ijolite, nepheline syenite and corundum syenite. Minor carbonatites with magnetite have been recorded along the slopes of the Western Ghats near the Kerala border around Kambamettu and Kothagudi in Theni District.

Minor veins of siderite-

ankerite-bearing carbonatite with rare sovite types are recorded in the carbonated zone in Attur valley in Salem District. The Salem ultramafic body, famous for its magnesite deposit is considered to be related to this syenite-carbonatite activity. The time of emplacement of these alkaline plutons has been well constrained by different isotopic systematics. The SGT was earlier considered to be the southern extension of the granite-greenstone terrain of Dharwar Craton exposed at a deeper tectonic level. This concept was based on the observation that the grade of metamorphism gradually increases from north to south. Geochronological and isotopic studies have brought to light that the southern part of the SGT lying south of Palghat –

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Cauvery Lineament (PCL) has a geological history distinctly different from the Dharwar Craton. These studies have shown that the terrain lying north of PCL shows crustal growth during the period from 3400 to 2500 Ma. In contrast, crustal growth in the terrain south of PCL is considered to have taken place predominantly during post-Archaean times, as constrained by Nd model ages (Harris et al., 1994). This terrain might have witnessed several cycles of metamorphism, the most pervasive being the 550-Ma Pan-African granulite facies event as constrained by isotopic systematics (Unnikrishnan Warrier et al., 1995b; Jayananda et al., 1995, Bartlett et al., 1995, Ghosh et al., 1998). In view of the contrasting geological history recorded by the terrains north and south of PCL, the SGT has been divided into the northern Archaean Craton (Dharwar Craton) and the southern Proterozoic (Pandian) Mobile Belt (GSI, 1994) with the PCL marking the boundary between them. The generalised stratigraphic sequence of SGT is shown in Table 2. Table 2: SGT Stratigraphy Major Rock Types

Alkali granite, granite, grano -phyre & acid intrusive Massive & incipient charnockite, cordierite charnockite

Group (with mineral occurrences)

Younger Granite (W)

Age

Era

550-390 Ma

550 Ma

PALAEOZOIC to NEOPROTEROZOIC

Charnockite (Younger)

Gabbro Anorthosite

Ultrabasic / basic (Younger) (Mo)

Carbonatite,ultrabasic complex Alkaline complex Alkaline rock Epidote-hornblende gneiss

Alkali Complex (Younger) (U, Th, Y, Nb, Ta, Be, & REE)

Basic dyke

Basic intrusive

1600 – 2100 Ma

MESOPROTEROZOIC

Carbonatite and alkaline dyke Syenite complex Ultrabasic complex

Alkali Complex (Older)

1900 – 2300 Ma

PALAEOPROTEROZOIC

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700 -600Ma

700 – 900 Ma

NEOPROTEROZOIC

Older grantie / granitoid Pink migmatite Pink augen gneiss Hornblende gneiss Hornblende-biotite gneiss Garnetiferous quartzo-feldspathic gneiss Garnet-biotite gneiss

Migmatite Complex (Peninsular Gneissic Complex II) (Fe)

Basic and ultramafic rock Magnetite quartzite Pyroxene granulite Charnockite

Charnockite Group

2200–2550 Ma

LATE ARCHAEAN TO PROTEROZOIC

2600 Ma

LATE ARCHAEAN

Calc-granulite Limestone Quartzite Garnet-sillimanite-graphite gneiss

Khondalite Group

Quartzo-feldspathic rock Amphibolite Banded ferruginous quartzite

Kolar Group (Au)

2900 Ma

Pink migmatite Granitoid gneiss Fissile hornblende gneiss

(Peninsular Gneissic Complex I) (Bhavani Group)

3000 Ma

Ultramafic / mafic, ultrabasic rock

Layered ultramafic / mafic, ultrabasic complex (PGE, Cr)

3000 – 3100Ma

Sathyamangalam Group of Tamil Nadu;Wynad Schist Complex of Kerala (Pb,Zn,Cu,Ag,Cd) BASE NOT KNOWN

Amphibolite, calc-silicate rock, basic and ultrabasic rock, sillimanite-kyanite-corundummica schist, fuchsite-kyanite ferruginous quartzite, talc-tremolite schist etc.

ARCHAEAN

3200 Ma

The SGT is associated with the metallogeny of the metallic minerals, broadly grouped under the categories – Gold mineralization in Archaean greenstone belts of Veppanapalli and Bargur sectors in Krishnagiri district, Banded Iron Formation (BIF) in parts of Dharmapuri, North Arcot,Villupuram and Salem districts; PGE and chromite mineralization in Archaean ultramaficmafic-anorthosite complexes of Sittampundi and Mettuppalaiyam. Also recorded Base metal mineralization in the Mamandur area of Cuddalore district of Tamil Nadu, shear controlled Molybdenum mineralization related to Neoproterozoic magmatism in shear zones; Rare metals (U-

15

Th-Nb-Ta-Y, Be) and REE mineralization associated with Neoproterozoic alkaline-carbonatite complexes of northern Tamil Nadu and granites and pegmatites in central Tamil Nadu, and Tungsten mineralization (Skarn type) in calc-granulites associated with Neoproterozoic granites in the Karungalagudi area, Madurai district, Tamil Nadu. EASTERN GHATS MOBILE BELT The Dharwar craton is bounded in the northeast by the Eastern Ghats Mobile Belt EGMB), extending for over 1000 km covering a distance of more than 600 km of Andhra Pradesh from Ongole in the southern part of the State into Orissa in a northeasterly direction along the eastern coast of the Indian Peninsula, is widest in Orissa (~ 300 km) and covers the major part of southern Orissa. This is a granulite terrain mainly made up of charnockite, khondalite, quartzite, calcgranulite, pyroxene granulite and leptynites. The EGMB includes two broad litho-stratigraphic groups, the Charnockite and the Khondalite Groups, together forming the Eastern Ghats Supergroup, intruded by layered anorthosite and associated mafic and chromiferous ultramafics and alkaline complexes. Both its northern and western contacts respectively with NOC and Bastar cratons are tectonised. This is a typical Proterozoic mobile belt skirting Archaean cratonic blocks and characterized by strong linearity, ductile deformation, high grade of metamorphism and a high gravity gradient along its contact zone with cratons. Age data available from the isotopic studies have provided new insight in to the chronostratigraphy of the events of this Precambrian terrane which range from late Archaean to Pan-African (Sarkar and Paul, 1998, Krause et al.. 2001, Aftalion et al., 2000 and Crowe et al., 2001). The EGMB in Orissa is separated from the Western Orissa Sector by an abrupt geomorphic and geophysical (Bouger gravity) discontinuity, also confirmed by deep seismic sounding (Kaila and Bhatia, 1981), and extends from the southern tip of Orissa to Sambalpur.The eastern boundary of the EGMB is probably marked by another major lineament along which they abruptly meet the coastal alluvia. The Chilka lake anorthosites occur along this lineament. The EGMB has a broad arcuate trend with a westward convexity, in conformity with the shapes of the Nellore schist belt and the eastern margin of the Cuddapah basin, on the west. Broadly EGMB has a NNE-SSW trend in the southern part but changes to NE-SW trend at west of Eluru. After a gap of about 40 km occupied by the Gondwana sediments of the Godavari graben, NW of Eluru, the western margin of the EGMB skirts the eastern fringes of the Bastar craton of Madhya

16

Pradesh. The eastern margin of the EGMB, along the East Coast is covered with Gondwana, Tertiary and Quaternary formations. The contact between the cratonic gneisses and the EGMB is a major tectonic feature marked by gabbro-anorthosite and alkaline plutons of Middle Proterozoic age (1600-1000 Ma). The Nellore Schist Belt in the southeast and Khammam Schist Belt in the northeast probably represent the remnants of an originally single N-S-trending schist belt that got dismembered during the development of the EGMB and its subsequent deformation. These mobile belt granulites (EGMB) have contrasting geochemical attributes than the cratonic granulites of SGT (Subba Rao, 1980). EGMB granulites are rich in REE with K-rich alkalies compared to Na, Rb, Ba and Th-rich alkalies of SGT. This belt is famous for its large resources of bauxite (formed mainly by supergene enrichment of Al from metapelitic protoliths (khondalites), variety of dimension stones (commercial granites) using charnockite, leptynites, granitoids, anorthosite and alkaline rocks, occurrences of a variety of gemstones including emerald, chrysoberyl, aquamarine, ruby, sapphire, topaz and garnet, resources of high-grade graphite and manganese ore and are being exploited locally. EASTERN INDIAN CRATON The Singhbhum-Orissa or Eastern Indian Craton (EIC) comprises Archaean nucleus of South Singhbhum, Proterozoic Dalma volcanic belt and the Chotanagpur Gneissic Complex (CGC) in the north. The Singhbhum nucleus (Naqvi and Rogers, 1987), a triangular region flanking Bastar Craton in the west, is bounded by Copper Thrust Belt (CTB; also called Singhbhum Shear Zone) in the north, Sukinda thrust in the south, high-grade metamorphic Satpura belt in the northwest and Eastern Ghat granulite belt in the southwest. This is the richest mineralised cratonic block in India and geographically the EIC comprise western part of the State of West Bengal, southern part of Jharkhand and northern part of Orissa. The geology of EIC is detailed in Table 3. Table 3. Stratigraphy of EIC (as given in Balasubrahmanyan, 2006)

_________________________________________________________________________ Newer dolerite dykes and sills

1600-950 Ma

Mayurbhanj Granite

2100 Ma

Gabbro-anorthosite-ultramafics Kolhan Group

2100-2200 Ma

-------------------------------------Unconformity---------------------------------------------

17

Jagannathpur/Malangtoli and Dhanjori-Simlipal lavas, Quartzite-conglomerate (Dhanjori Group)

2300 Ma

Pelitic and arenaceous metasediments with mafic sills (Singhbhum Group)

2400-2300 Ma

--------------------------------------Unconformity--------------------------------------------Singhbhum Granite III

3100 Ma

Epidiorites (intrusives) Iron Ore Group (IOG volcano-sediments) ---------------------------------------Unconformity-------------------------------------------Singhbhum Granite I and II, Nilgiri Granite, Bonai Granite

3300 Ma

Older metamorphic Group (OMG) and Older Metamorphic Tonalitic Gneiss (OMTG) folding and metamorphism

3500-3400 Ma

OMTG

3775 Ma

OMG ?

4000 Ma

______________________________________________________________________

A major section of this craton is occupied by the Singhbhum granite batholith complex covering an area of about 10,000 sq km. A number of shallow basins (the supracrustals) within and around the periphery of this granite batholith are also present viz. iron ore basins in the western sector containing large economic deposits of iron ores, banded haematite quartz, Simlipal-Dhanjori basin comprising volcanics and volcanoclastic sediments, etc. Enclaves of older rocks like the Older Metamorphic Group (OMG) of igneous and sedimentary rocks now metamorphosed to amphibolite facies (ortho- and para-amphibolite respectively) and the Older Metamorphic Tonalite Gneisses (OMTG) occur as remnants within the batholithic complex. The OMTG intrudes synkinematically into the OMG amphibolites indicating that the latter is the oldest unit (Sharma et al., 1994). Presence of large number of enclaves of OMGOMTG association occurring throughout the batholithic complex attests to the extensive nature of these rocks before the intrusion of the Singhbhum Granite. The Iron Ore Group (IOG) of rocks (the major supracrustal unit in EIC) deposited subsequent to OMG-OMTG. IOG constitutes low-grade metasediments including phyllites, tuffaceous shales, banded hematite quartz/jasper (BHQ/BHJ), iron-ore,ferruginous banded quartzite, local dolomite,

18

acid intermediate and mafic volcanics as well as mafic sill-like intrusives. Deposition of IOG is followed by intrusion of Singhbhum granite batholith representing dominant crustal growth in this craton. From field evidence, trace, REE and isotope geochemistry (Saha, 1994), it has been considered that this vast granite batholith can be grouped into three different phases according to their time of emplacement which are as follows: Phase I: Dalima and Rajnagar-Kuyali units, Phase II: Besoi, Hatgamaria and Keonjhargarh-Bhaunra units and Phase III: Haludpukur-Chapra, Kalikapur-Matku, Saraikela-Jorapokhar-Tiring, Gorumahisani, Gamaria-Khorband-Karanjia units. A pause in crustal growth followed the intrusion of Singhbhum Granite and was interrupted by a sedimentary cycle (the Singhbhum Group) and a volcano-sedimentary cycle (the Dhanjori Group) respectively. The Singhbhum Group metasedimentaries, mainly confined to the areas close to CTB, extend across the thrust zone to SW of Baharagora over an extensive area up to the base of Simlipal hill range. Singhbhum Group starts with the Chaibasa Formation containing garnet, staurolite, kyanite-bearing mica schists with numerous bands of quartzites and ortho- and parahornblende schist. This is followed by Dhalbhum Formation at the top containing phyllites with a few quartzite bands, chlorite, magnetite and chlorite phyllites and epidiorite sills. Towards the top, the Singhbhum Group is terminated with the eruption of Dalma volcanics. The Dhanjori basin, resting unconformably over the IOG in the NE part of the craton, predominantly consists of volcanics and volcanoclastic sediments. Vast copper deposit within the low-grade metavolcanic member has been extensively mined. The Dhanjori volcano-sedimentary assemblage is considered to represent a greenstone cycle (Gupta et al., 1985) within the south Singhbhum Proterozoics. The sequence comprises a lower unit of metapelites, psammites with ultramafics and mafics (gabbro/dolerite) and an upper predominantly volcanic unit comprising mafic ultramafic tuffs, intrusives, metabasalts and tuffaceous sediments.The lower ultramafics have distinct komatiitic affinity with definitive spinifex textures (found only within this unit of EIC; Majumder, 1996).The upper Dhanjori basaltic suite comprises alkali olivine basalts passing upwards into K-poor oceanic tholeiites. An extensive granite granophyre complex occurring along the western margin of the main Dhanjori basin has obliterated the contact between the Dhanjoris and Archaean Singhbhum granite complex. Another large Proterozoic basin, called Simlipal basin (Iyenger and Banerjee, 1964) forming Simlipal hill range, is a large oval-shaped basin of mafic volcanics. The basin comprises spilitic lavas and tuffs along with basal arkose-orthoquartzites and overlies the Archaean basement and two thick inter-trappean orthoquartzite bands.Two other large volcanic suites were formed during this period namely, the Jagannathpur lava and Malangtoli

19

lava.These two lava formations are considered as post-Singhbhum granite and pre-Kolhan age (Saha, 1994). Compositionally these lavas display three distinct types viz. low-grade metabasalts, metaandesite and meta-oligoclase andesite. The Proterozoic Dalma belt, lying north of CTB and sandwiched between the Singhbhum nucleus in south and high-grade CGC in the north, is a 200-km-long and 3-7-km-wide arcuate belt and mainly comprises greenschist facies rocks of Singhbhum Group and meta-volcanics.The belt has been intensely folded into a synclinorium along E-W to NE-SW axes which is refolded at the eastern and western extremities (Saha, 1994). Stratigraphically, the rocks of this belt are classsified into a lower and upper member. The lower member comprises of phyllites (often carbonaceous), quartzites, shale, high-magnesian komatiitic serpentinised peridotites, lavas and vitric tuffs with quench textures, volcanoclastics, etc. Concordant basic-ultrabasic plutonic bodies (gabbro, pyroxenites) of considerable dimensions are also found interlayered with the tuffaceous horizons in the eastern sector. The upper Dalma member is represented by high iron - low potash tholeiitic basalts along with some rhyolites. Dalma volcanics bear considerable similarity with Dhanjori volcanics, though the former contains less basaltic komatiites. Stratigraphically, however, Dhanjori have always been considered as either equivalent to Dalma or slightly older. The Proterozoic volcano-sedimentary cycle is followed by intrusions of large isolated granitoid bodies like Kuilapal and Chakradharpur granites (CKPG) in the NE and southern margin of Dalma belt respectively. The Kuilapal granite is an ellipsoidal granite gneiss body occurring within moderately high-grade metamorphosed pelitic schist and interbanded hornblende schist, talc schist and conglomerate. Its composition varies from trondhjemite to tonalite. The CKPG is an east-westtrending elongated body with numerous enclaves of amphibolites, chlorite schist, talc-schist, rootless intercalations of arkose-conglomerate and quartzite (Bhaumik and Basu, 1984). Other acid plutons, intruded along the southern margin of CTB, are the soda granite and the Arkasani granophyre. After the relatively minor Proterozoic crust building episode within the Dalma belt, there was a pause followed by the final crust forming events in this area beginning with the emplacement of gabbro-anorthosite complex along the eastern margin of Singhbhum granite batholith extending from Butgora in the north to Nausahi in the south. This is followed by emplacement of Mayurbhanj Granite (MBG) covering approximatly 1000 sq km (Saha, 1994). The MBG was overlain by the Kolhan Group of sediments. The sediments are sandstone, shale, argillaceous limestone and orthoquartzite. The final stabilisation of this craton is marked by the intrusion of spectacular set of reticulating basic dyke swarm, known as Newer dolerite dyke swarm (NDD), mainly confined in the

20

southern part of CTB. NDD is considered to be the youngest magmatic activity and stratigraphic unit (op.cit) in EIC. The Chhotanagpur Granite Gneiss Complex (CGC) occupies a considerable area in the northern part of EIC and is intrusive into the schists in the south (Dunn and Dey, 1942). The Chhotanagpur Gneiss Complex (CGC), extending from Chhattisgarh in the west through Orissa and Jharkhand up to parts of the districts of Purulia, Bankura, Birbhum and Medinipur of West Bengal in the east, forms an integral segment of the Precambrian Continental Shield of Eastern India. The major parts of CGC occurring in south Bihar and northern part of Jharkhand and in West Bengal is a vast gneissic terrain exposing complex assemblages of diversified rocks, which have witnessed several periods of magmatism, tectonism, sedimentation, metamorphism, partial melting and mineralisation that have altered the pre-existing volcanic, plutonic and sedimentary rocks to a gneiss-granulite-granite association. In northeast India, the Meghalaya is a huge geomorphic up-arch of Precambrian metamorphic rocks with a narrow southern fringe. The northern limits of the Meghalaya uplands are marked by the Brahmaputra Plain.The various rock groups occupying the region includes Bomdila Group, Sung Valley alkaline carbonatite complex, basement gneisses of Meghalaya Plateau and granitoids of EIC like Kyrdem, Nongpoh and Mylliem. This part of the Peninsular Indian Shield is associated with the mineralization of copper in Mosabani-Bedi –Rakha mines in Jharkhand; Jaduguda uranium mineralization; iron, manganese, chromium, vanadium, titanium,gold, copper, molybdenum in the mafic magmatic provinces in Jharkhand and north Orissa; tin, niobium, lithium, beryllium occurrences in late Proterozoic granitesyenite-gabbroic province in western Orissa, occurrences of lead-copper, phosphorite, mica and manganese in the carbonate-rich mobile belt of Gangpur-Chotanagpur and granite plutons with associated pegmatites and quartz veins carrying beryllium, tin, tungsten, uranium and tantalum. CENTRAL INDIAN PRECAMBRIAN SHIELD The Central Indian Shield is a mosaic of two crustal provinces, the Southern Crustal Province (SCP) and Northern Crustal Province (NCP) separated by a prominent East -West trending Central Indian Shear (CIS)/ Central Indian Tectonic Zone (CITZ). The Western part of thei sector is blanketed by thick pile of Deccan Traps (i.e major part of Maharashtra and Western part of Madhyapradesh) The SCP is with Archien nuclei known as Bastor Craton. The Baster Craton is bounded to the North East by Mahanadi graben, of the South West by Godawari graben; to the North

21

Weas by Satpura Mobile Belt and to the South East by Easternghats Mobile Belts. Bhopalpatanam Granalite Belt is seen to shoulder along the Godawari Graben. The domain to north of the SonNarmada-Tapti (SONATA) lineament is named as the Bundelkhand Protocontinent (BP) or the NCP consisting of the Bundelkhand craton, surrounded by the Vindhyans and the fold belts of AravalliDelhi in Rajasthan. To the south, Deccan Protocontinent (DP) or the SCP occurs with the Singhbhum-Bastar-Dharwar Cratons (Yedeker, 1986; Yedeker et al., 1990; Acharyya and Roy, 2000). The Bundelkhand Craton (BDC) in the north and the Bastar Craton (BC) in the south have Archaean nuclei. The supracrustal belts in northern and western parts include the Mahakohal, Sakoli, Sausar Groups apart from the Dongargarh Supergroup, whereas to the south and east the Sukma, Bengpal and Bailadila Groups form the main lithotectonic associations.The Abujhmar Group is a volcano-sedimentary ensemble in contrast to Chhattisgarh, Indravati, Pakhal and Sullavai Groups constituting important Purana cover sedimentary sequences. The simplified stratigraphy of Central Indian Precambrian Shield (CIPS) is given in Table 4.

Table 4: Stratigraphy of CIPS (simplified after Sarkar et al., 1990) Major Rock Types Supracrustal rocks, granite and gneiss Kimberlites

Mafic dykes, granite,gneiss

Granite

Granite, gneiss, volcanics

Group Khairagarh Belt, Granite in Satpura Belt; as Tirodi Gneiss (Sausar Group) Majhgaon, Hinota diatremes Mafic dykes and granite in Bastar craton, Abhujmar Group, Keskal granite, Amgaon Gneiss, Tirodi Gneiss Sonakhan, Bailadila, Khairagarh, Gwalior, Sausar, (?) Sakoli, Chilpi Groups Sukma, Pujariguda, Burgudem, PaliamDarba, Cholanguda granite (Sn – W mineralization) Bundelkhand Granite, Khairagarh, Chilpi Ghat, Abujhmar Volcanics, Chilpi Group, Sausar Group, Dongargarh Granite, Malanjkhand tonalite-granodiorite Gneiss, Nandgaon Group,

Age 800 Ma

1200-1000 Ma

Era NEOPROTEROZOIC NEOPROTEROZOIC to MESO-

1500 Ma

MESOPROTEROZOIC

1600 Ma 1600 Ma

MESOPROTEROZOIC

2200 Ma

PALAEOPROTEROZOIC

PROTEROZOIC 2400-2300 Ma

22

To

Mahakoshal Group Abujhmar, Nandgaon, and (?) Sakoli Groups

Gneiss

Metasediments Gneissic Complex

Bengpal, Amgaon, Sukma Groups Bundelkhand, Baya and Sukma Gneiss

LATE ARCHAEAN 2600-2500 Ma

LATE ARCHAEAN

ARCHAEAN ? 3600 Ma

ARCHAEAN

BASTAR CRATON The Bastar Craton (BC) is bounded to the northeast by Mahanadi graben, to the southwest by the Pranhita-Godavari graben, to the northwest by Satpura mobile belt, and to the southeast by Eastern Ghats Mobile Belt. The cratonic components of Bastar includes Basement Gneiss (≈ 3.5Ga) followed by the (i) Sukma metamorphic suite (≈ 2.6 Ga), Bengpal Group (≈2.3 Ga), Bailadila Group (2.1 Ga), undifferentiated granites and basic dykes (Ramakrishnan, 1990).Dutta et al. (1981) indicate a Narainpur Group above the Bailadila Group with sandstone, conglomerate and mafic volcanics. Sukma Group comprises slivers of quartzite, pelites, calc-silicates, BIF and amphibolites. The Bengpal Group of rocks consists of low-to medium-grade volcanosedimentary sequence of amygdular metabasalt, quartzite, conglomerate and andalusite and chloritoid schist. Bailadila Group, consisting of quartzite, phyllite and BIF, hosts iron-rich deposits; (ii) Sonakhan belt is endowed with greenstone-granitoid association; (iii) Kotri-Dongargarh belt of volcanosedimentary-granite association of Dongargarh Supergroup is represented by older Nandgaon Group of basic and acid lava and pyroclastics, the Dongargarh granite and younger Khairagarh Group of volcanosedimentary sequence;

(iv) Sakoli belt comprises distinct low-grade supracrustrals of bimodal

volcanics, pelitics and quartzite laid on Amgaon Gneisses of 2.5 Ga, and (v) the cover sequence of the Chhattisgarh, Indravati, Albaka and Sullavai Supergroup / Group. The NCP includes (i) The Central Indian Tectonic Zone with gneiss- supracrustal-granite litho-associations of Mahakoshal, Sausar and Betul-Chhindwara belts and the granulites in Sausar terrain. (ii) Bundelkand gneiss-granitoid terrain with enclaves of minor supracrustal belts, and (iii) Cover sequences of Vindhyan and Bijawar Supergroup /Group. Archaean gneisses and high-grade granulitic/charnockitic rocks are exposed mainly in the southern part of the region. This includes gneissic rocks of Pranhita- Godavari valley, charnockitic suite of rocks along the Wainganga valley in Bhandara and Chandrapur districts, the gneisses and associated

supracrustals

of

Bastar

area,

the

23

Tirodi

gneisses

of

Nagpur-Seoni

area

(Narayanswamy,1962), gneisses and supra crustals occurring to the east of Sakoli basin in GondiaBhandara- Rajnandgaon sector grouped as Amgaon Group (Sarkar, 1958). The Bastar/Amgaon/Tirodi gneisses and associated supracrustals include upper amphibolite facies, high-grade gneiss-migmatite with supracrustals including metasediments (quartzite – BIF – carbonate - pelite) and meta-igneous (amphibolite, ultramafic) litho-types. The supracrustals are interleaved with gneissic rocks that contain relicts of TTG suite, the whole setup being dismembered by younger granitic intrusives in different areas of the region. The gneisses exposed south of Sakoli fold belt in Gadchiroli, Chandrapur, Nagpur and Bhandara districts are generally referred as Bengpal Gneisses. This belt is about 200km X 60km2 and further southward merges with the gneissic country of Bastar area where these have been named as Bengpal (Sukma) Gneiss-supracrustals. Gneiss migmatites include banded gneiss, stromatic gneiss and leucocratic gneiss containing meta-sedimentary, meta-igneous and TTG restites. Banded magnetite quartzite, hornblende schists, pyroxene-bearing gneisses, quartzite and pelitic schists occurring as thin bands are scattered over a wide area. Towards eastern part it is designated as Baya Gneiss. The closing of the Sukma Orogeny is indicated by the Sukma granite gneiss at ≈ 2.6 Ga. The maximum age for Bengpal Group of rocks is set by the intrusive Paliam and Darba granites with whole-rock isochron age at 2308± 48 Ma (Sri = 0.735) with mineral ages of 2050 Ma and 1620 Ma. Quartzite bands of Bailadila Group extend along strike for several kilometres in the southern parts of Gadchiroli District and are interbanded with other meta-sedimentary rocks. They show gradational contact with BIF and calc-silicates rocks. Quartzites include orthoquartzites, at times micaceous, calcareous and ferruginous, and commonly contain minor amounts of graphite. Magnetite – specularite form BMQ (BIF) with impersistent folded quartz-magnetite banding on milimetre to centimetre scale extending for several kilometres and contains 67 to 68 % Fe. Two such important patches are seen in parts of Chhattisgarh. The Sonakhan Group of rocks occurs in the eastern part of Chhattisgarh State. This comprises continental bimodal, basalt-rhyolite association of volcanics with greywackes and conglomerates. The quartz veins in the bimodal volcanics are gold-bearing. The Nandgaon Group comprises Bijli volcanics and Pitepani basic volcanics. Bijli consists mainly of rhyolite and sandstone. Pitepani volcanics mainly includes massive to porphyritic basalt with rare pillow structure. The rocks are well exposed in the eastern part of Bhandara district in

24

Salekasa area and extend southwards in Korchi area of Gadchiroli district and in parts of Rajnandgaon district of Chhattisgarh. The Sakoli Group covering an area of about 3500 sq km in parts of Nagpur, Bhandara and Gadchiroli districts of the Maharashtra comprises a metamorphosed volcano- sedimentary sequence. The volcanic to sedimentary rocks ratio is about 1:4. Both mafic and felsic volcanic rocks are present in nearly equal proportions. Sakoli Group includes metasediments dominated by phyllite (carbonaceous at places), mica schist (with varying proportions of magnetite, andalusite, chloritoid, garnet and staurolite), metabasalts, metarhyolites and banded iron formation (BIF). Quartztourmaline rock (tourmalinite) and banded garnet-amphibole-biotite-quartz rock (BGA, possibly a variant of banded manganiferous iron formation) are the other significant rocks of this group. Quartz veins, alkali-feldspar granite, pegmatite and amphibolite/gabbro are the intrusives in the Sakoli Group. The meta-basalt are iron-rich tholeiite while meta-rhyolite are represented by pyroclastics, tuffs and flows with composition ranging from rhyolite to rhyodacite. The gneiss and older supracrustals (Sukma-Amgaon) encircling the Sakoli Group represent basement to the Sakoli sequence and also occur as inliers within the Sakoli Fold Belt. The 75-km-wide and 300-km-long Sausar Fold Belt in Madhya Pradesh is trending E-W, curvilinear (southerly convex) belt extending from Balaghat in the east to Chindwara in the west, exposing a central domain of dominantly supracrustal rocks (metamorphosed quartzite, pelites and carbonates) and characterized by lack of volcanic rocks. It is intimately associated with a variety of granitic rocks of anatectic origin. The Sausar Mobile Belt (SMB) displays the Sausar Group together with some granulites, Tirodi Gneiss and the Augen Gneiss. It is confined between the northern Bundelkhand Protocontinent and the south Deccan / Bhandara Protocontinent. This Proterozoic major crustal belt is said to have three lithotectonic units – (i) Mafic granulite-felsic migmatite gneiss – the Tirodi biotite Gneiss, (ii) Augen Gneiss, foliated granite, and (iii) Sausar Group comprising calcsilicate gneiss, calcite marble, dolomite marble and quartzite (Bhowmik et al., 1999). The southern periphery of the supracrustal sequence reveals linear suite of two-pyroxene granulite-charnockitemetapelite granulite lenses and pods. The granulites reveal the pre-Sausar structure (Narayanaswami et al.,1963). The main Sausar Orogeny is ≈ 1000-Ma Grenvillian age implying granulite metamorphism as pre-Grenvillian. The Tirodi Gneiss indicates an age of 1525 ± 70 Ma with a mineral isochron at 860 Ma (Sarkar et al., 1986). The Tirodi biotite Gneiss considered earlier to be a migmatised Sausar supracrustal unit, is now related to a granulite-facies metamorphism in Ramakona – Katangi granulite belt preceding the deposition of the supracrustals.

25

The Makrohar granulites occurring as a belt to the south of the Son-Narmada South Fault (SNSF), south of Mahakoshal Belt and intruded by gabbro-anorthosite and granite are thought to represent granulite metamorphism at ≈ 1.7 Ga (Pichai Muthu, 1990; Roy and Prasad, 2003). The Mahakoshal Group is a supracrustal sequence with dominant metasediments and subordinate tholeiite metavolcanics with intrusive dunite-peridotite and occasional sills of sodagranite. The group has a faulted contact with the Archaean gneisses and migmatites between Jabalpur and Sidhi comprising the Agori and Parsoi Formations in which intrusives occur. The contact of this group with the Jungel Group is also faulted. The contact with the Vindhyan Supergroup lying above is also faulted. The lower Agori Formation consists of pillow-pahoehoe toes, bomb agglomerate, volcanic breccia, tuff and chert. This group of rocks occurs as a horst in the Satpura axis. The Betul supracrustal belt is a granitoid gneiss tract between Mahakoshal Belt to the north and the Sausar supracrustal belt in the south. This has quartzite, pelite, calc-silicate, BIF, garnet-anthophyllite schist intruded by mafic, ultramafic and granitic rocks with bimodal volcanics – a low K-tholeiitic basalt and calc-alkaline to alkaline rhyolite.Three phases of folding with amphibolite-facies grade of metamorphism and intrusion of granite are noted. In the northern part of this belt peridotite, pyroxenite, gabbro, norite and diorite have BIF granulite enclaves. Volcano-sedimentary sequences of the Khairagarh and Abujhmar groups and sediments of Chilpi Group belonging to Palaeo-Mesoproterozoic unconformably overlie the older sequences and the granite in the Mailkala range and Abujhmar plateau region. Pakhal Supergroup belonging to Mesoproterozoic occupies the Godavari valley region.

Platformal cover sequence of the

Chhattisgarh Supergroup of Meso-Neoproterozoic occupies the Chhattisgarh plains. The Dongargarh Supergroup occurs to the west of Chhattisgarh basin and to the east of Sakoli synclinorium. This group overlies Amgaon and Sakoli Groups, comprising the lower igneous suite of Nandgaon Group and upper sedimentary igneous alternation of Khairagarh Group separated by a pronounced unconformity subsequent to the emplacement of the Dongargarh Granite. The Khairagarh Group is exposed in the central part of the Dongargarh Belt south of Deori and around Darekasa of Maharashtra and in Rajnandgaon district of Chhattisgarh state. The Bortalao Formation forms the lowermost litho-sequence of the Khairagarh Group, which unconformably overlies the volcanic rocks of Nandgaon Group and the Dongargarh Granite. It forms an E-Wtrending belt of varying width on the flanks of normal and inverted canoe-shaped folds and saddle folds in the area south and west of Deori and NNE-SSW-trending limb of syncline in east of

26

Salekasa. Impersistent beds of conglomerate often occur at the base of this formation consisting of well-rounded pebbles, cobbles and boulders of variously coloured Bijli rhyolites, Dongargarh granite, arkose, vein quartz, quartzite, chert, trachyte, basalt and andesite in a fine-grained matrix. The Sitagota volcanics overlie this and comprise dull green basalt with minor tuffs and agglomerates. Karutola Formation disconformably overlies the Sitagota volcanics and consists of fine-to coarse-grained, well-bedded pure and ferruginous quartzites. It is followed by the Mangikhuta volcanics consisting of non-porphyritic, amygdaloidal pyroxene tholeiite with minor intertrappean, laminated shale and siltstone. Ghogra Sandstone is mainly quartz-arenite in composition, and this lithounit is considered by Yedekar and Jain (1996) as intraformational between Mangikhuta and Kotima Formations. Several major faults have been recorded mostly affecting the lithounits of the Khairagarh Group, which include N-S-trending Darekasa Fault (Sarkar, 1957-58). Dhara-Kamarwara and Tappa faults also extend in N-S direction for tens of kilometres at the eastern margin of the Khairagarh Group. The Kotri Belt is the southern extension of the Dongargarh belt with comparable stratigraphy. Mahla Formation and Rhyolite Formation represent the Nandgaon Group of Dongargarh supergroup in the Kotri Belt. The Abujhmar Group in the Kotri Belt is correlatable with Khairagarh Group. The belt occurs in northwestern part of the Gadchiroli district of Maharashtra and partly in adjoining parts of Chhattisgarh and includes a litho-assemblage of locally significant conglomerate, chlorite schist, muscovite schist and sericite quartzite associated with meta-ultramafic and gabbro bodies. The intrusives within the belt are coarse pink granites, which are correlatable with the Dongargarh Granite. The meta-ultramafics show alteration of original pyroxene to an assemblage of serpentinite-tremolite and tremolite-serpentinite-actinolite. The BIF includes carbonate-and sulphide-bearing bands, often being pyritiferous. Quartzite includes conglomeratic bands of local importance. The Amgaon Gneiss, located in the southern and northern part of the triangular belt with Sakoli, Sausar and Dongargarh supracrustals and granulite belts, is intruded by the Dongargarh quartz monzonite and Malanjkhand granodiorite, known as Dongargarh Granite. This granite, exposed in several batholiths and stocks parts of Bhandara and Gadchiroli districts of Maharashtra and Rajnandgaon district of Chhattisgarh States, is one of the oldest rapakivi epizonal coarse-grained granite with porphyritic, equigranular and microgranite textures and devoid of pegmatites, dated at ≈ 2.4 Ga. The isotopic age data points to a temporal association among Malanjkhand granodiorite,

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Bijli rhyolite and Dongargarh granite. It is emplaced between older Nandgaon Group and younger Khairagarh Group. BUNDELKHAND CRATON This highly deformed granite-greenstone terrain consists of the Bundelkhand Granite massif with an aerial extent of 26,000 km2 bounded by the Great Boundary Fault to its west, the SonNarmada North Fault of Central Indian Tectonic Zone to its south, Ganga Foreland to its north and wrapped around by the extensive Vindhyan Basin. This cratonic area comprises ultramafics, amphibolite, fuchsite quartzite, banded iron formation, schists, marble, calc-silicate rocks and tonalite-trondhjemite-granodiorite (TTG) intruded by undeformed hornblende-, biotite- and leuco granitoids. Dykes of porphyry, acid volcanics, rhyolite breccia and pegmatite veins pervade the massif. The NE quartz reefs and NW swarm of mafic dykes terminate the activity in this massif. The Bundelkhand Granite consists of an early porphyritic phase followed by several intrusive phases of monzonite, leucogranite, diorite-syenite-granite and other porphyries with three generations of dolerites. Bundelkhand Granite has been isotopically dated at ≈ 3.3 Ga. Large-scale granitoid magmatism of batholithic dimension around 2.5-2.2 Ga (Bundelkhand Granite, Dongargarh Granite, Malanjkhand Granite) in the Central Indian Shield probably reflects the late archaean - early Proterozoic cratonisation in this part of the shield area (Ramachandra, 1994; Ramachandra and Roy, 1998). Kimberlites occur as intrusives into Bastar craton. Other mineralisation in this part of the shield area includes the Malanjkhand copper in granodiorite; alkali granite and granodiorite in the Mahakoshal Group hosting copper mineralisation at Karaudiya in tholeiitic metabasalts; stratiform zinc sulphide mineralization at Kholari-Bhaonri in the lower part of Bhiwapur Formation and vein type copper-galena-gold-tungsten mineralization with platinum incidence at Kholari-BhaonriRanbori and Ranmangli areas in the upper part of the Bhiwapur Formation of Sakoli Group; minor gold-silver-tin-molybdenum occurrences in BIF of Sakoli Group; workable Khobna tungsten prospect of Umrer Tehsil of Nagpur district, Maharashtra State hosted by the quartz-chlorite mica schist of the Sakoli Group; skarn type of

tungsten (scheelite) occurrences along with minor

sulphides of base metals in amphibolite within tourmaline granite at Umrer and in marble/calcareous quartzite at Kosamtondi-Bagarban-Kheripur areas; occurrences of manganese ores associated with ‘Gondites’ of Sausar Group; uranium mineralization in a 100-km-long shear zone in crystalline rocks from River Mahan in the west of Surguja district of Madhya Pradesh

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extending to the east in Palamau district of Jharkhand State and uranium deposits in metarhyolite and metabasics in periphery or close to the Dongargarh Granite at Bodal and Bhandaritola; fluorite occurrences within sheared Dongargarh Granite at Chandidongri. Laterite with pockets of bauxite forms capping at a number of places over these rocks in Keshkal-Amabera area. WESTERN INDIAN PRECAMBRIAN SHIELD The Precambrian of the Western Indian Shield from east to west comprises the Banded Gneissic Complex (BGC) or craton and the Aravalli – Delhi mobile belts with the TransAravalli basins encompassing the area west of the Aravalli mountains. The stratigraphy of the area is summarized in Table 5. Table 5: Stratigraphy of Western Indian Precambrian Shield (after Gupta et al., 1980) Major Rock Types / Group Erinpura Granite Malani Volcanics Godhra Granite and Gneisses Punagarh and Sindreth Groups Sendra-Ambaji Granites Kishengarh Syenite Phulad Ophiolite Suite Kumbhalgarh and Ajabgarh Groups Gogunda and Alwar Groups Champaner Group Lunavada Group (Udaipur, Salumbar, Udaisagar and Darwal Granites) Rakhabdev Ultramafic Suite Jharol Group and Dovda Group Nathdwara Group Bari Lake and Kankroli Groups Udaipur Group Debari group Undifferentiated Granite Ranthambor Group Berach and Jahazpur Granites Rajpura-Dariba, Pur-Banera Jahazpur Groups and Sawar Group Hindoli Group, Mangalwar Complex and Sandmata Complex Mafic and ultramafics; Untala and Gingla Granites

Supergroup

Age

Era

1600 – 700 Ma

NEOPROTEROZOIC

Delhi Supergroup

2000-1600 Ma

MESOPROTEROZOIC

Aravalli Supergroup

2500-2000 Ma

PALAEOPROTEROZOIC

Bhilwara Supergroup

≥ 2500 Ma

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ARCHAEAN

BGC The oldest cratonic nucleus of the Western Indian Shield, the BGC, occupies a large tract in the Mewar plains of south and east Rajasthan. It is bounded on the west and southwest by Proterozoic fold belts of the Aravalli and Delhi Supergroups, while an arcuate belt of low-grade volcanometasedimentaries (Gwalior Series in Heron, 1953; Eastern Aravalli belt in Gupta, 1934, and Hindoli Group in Gupta et al., 1981) and Vindhyan platformal sediments demarcate the eastern boundary of this craton. The Deccan Traps delimit the southern boundary of its outcrop area (Gupta and Malhotra, 2000). The older component of the Aravalli craton occurs in the BGC in the eastern and southeastern parts of the Aravalli Range. The BGC is a time transgressive crystalline complex, comprising gneisses of amphibolite to granulite facies derived from plutonic, volcanic and sedimentary protoliths. The crystallines are intruded by granitic plutons of several generations ranging in age from Archaean to Middle Proterozoic. The sedimentary component is dominantly pelitic and is well exposed on the eastern margin of the Delhi Supergroup. The volcanic component is represented by basic lavas now occurring as hornblende schist or amphibolite (Heron, 1953; Roy,1988, 1991; Sinha Roy, 1985 and Sinha Roy et al., 1992). Metamorphic and structural studies have clearly demonstrated that the BGC was the crystalline basement over which Proterozoic rocks of Aravalli and Delhi Supergroups were deposited. The BGC was later on reclassified as the Bhilwara Supergroup comprising (1) the Sandmata Complex which is subdivided into three formations viz., the Baranch, Badnor and Shambhugarh Formations, and intruded by Gyangarh-Asind Charnockite-enderbite, Amet Granite, Anjana Granite, etc; (2) the Mangalwar Complex which is subdivided into the Lasaria, Kekri, Sarara, Mando Ki Pal, Suwana, Potla and Rajmahal Formations; and (3) the Hindoli Group which is subdivided into the Bhadesar, Sujanpura and Nangauli Formations.

The metamorphic-cum-

migmatitic contact between the Sandmata Complex and the Mangalwar Complex practically coincides with the Delwara lineament. The Sandmata Complex comprises migmatite, composite gneiss/bimodal gneiss, calc- gneiss, garnet-sillimanite gneiss, garnet-staurolite-sillimanite schist, chlorite-biotite schist, mica schist, cordierite-garnet pelitic gneiss, enderbite charnockite, pyroxene granulite, norite, hornblende schist, amphibolite, epidiorite and quartzite. The complex is further characterized by preponderance of acid, and mafic igneous suite of rocks. The term Sandmata Complex is restricted to the ductile shear zone bounded by granulite-facies rocks, with the absence of charnockite and eclogite but the presence of high-alumina granite, basic granulite, leptynite and norite dykes.

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The Mangalwar Complex is considered presently as representing Archaean primary granite– greenstone belt. In the northern part, migmatitic gneiss-amphibolite association of the greenstone sequence is represented by banded bimodal gneiss, amphibolite, pelitic schist, fuchsite quartzite, quartzite, chert, BIF, calc-silicate rock and marble. In the sourthern part of BGC terrain, mafic enclaves, represented by amphibolite, migmatised gabbroic rock and chlorite schist , are by far the most prolific of the suite. High-magnesia mafic and ultramafic enclaves include tremolite-actinolite schist, grunerite-garnet schist, magnetite and garnet- bearing chlorite-actinolite schist, chlorite schist, talc-chlorite schist and talcose serpentinites with asbestos veins. Besides, long linear bodies of felsic volcanics in the form of qurtzo-feldspathic rocks are also present. The Hindoli Group comprises a low-grade (greenschist facies) sequence predominated by turbidite and volcanics. The arcuate belt of the nearly continuous Hindoli Group, interrupted by Berach Granite, occurs along the eastern and southeastern flank of the BGC/Mangalwar Complex. In the southern end of the Hindoli belt, the Hindoli Group is overlain unconformably by the Vindhyan Supergroup of rocks and further south by the Deccan Trap basalts. Overlying the Hindoli Group of rocks and Mangalwar Complex with an unconformity occur the next younger groups of rocks classified as the Rajpura-Dariba (subdivided into the Bhinder, Malikhera, Dariba, Sindesar and Satdudhia Formations), Pur-Banera (classified into the Pur, Pansal, Rewara, Tiranga and Samodi Formations), Jahazpur and Sawar Groups (subdivided into the Morhi and the Ghatiali Formations) which are exposed in a series of isolated linear belts. All these synformal metasedimentary basins/structures of Lower Proterozoic age occur in disjointed belts as outliers and they are mostly composed of dolomite, marble, calc-gneiss, calcareous biotite schist, graphite-kyanite-staurolite schist, garnetiferous mica schist, chert, banded ferruginous chert and quartizite. The BGC are devoid of mineralization except for the Rampura-Agucha zinc-lead deposits. ARAVALLI-DELHI MOBILE BELTS The Aravalli and Delhi mobile belts, also known as fold belts or shear belts, are the major components of the western Indian Precambrian shield. These belts are metallogenically important with copper, zinc and lead mineralization with gold, tin and tungsten at places. The Aravalli-Delhi Province is composed of Proterozoic supracrustals sequences classified as the Aravalli Supergroup (Early Proterozoic) and Delhi Supergroup (Early to Middle Proterozoic). Metamorphic and structural parameters backed up by geochronological data have

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clearly demonstrated that the BGC was a crystalline basement upon which the rocks of the Proterozoic Aravalli and Delhi Supergroups were deposited. Besides, evidences of an unconformity between the BGC and the overlying supracrustal suites have been widely proposed. The Delhi Supergroup occurs in the form of two distinct fold belts, i.e., the North Delhi Fold Belt (NDFB) in Alwar, Dausa, Jaipur, Bharatpur, Sikar and Jhunjhunu districts and the South Delhi Fold Belt (SDFB) in Ajmer, Pali, Rajsamand, Udaipur and Sirohi distrcits. Recent mapping by GSI in the Khetri area have identified and separated the Khetri fold belt (Khetri basin) from the NDFB by a basement-cover sequence separable from the main NDFB of the Alwar-Bayana-Lalsot basin. The rocks of the Aravalli Supergroup show an inverted V-shaped map pattern with an arcuate disposition with the apex of the V located near Nathdwara. The width of the belt in the north is about 40 km gradually fanning out to 150 km in the south in Gujarat state. The Aravalli Supergroup shows two distinct ‘facies sequence’ indicating deep-sea and near-shore shelf environments interpreted by many as eugeosynclinal-miogeosynclinal couple or as forelandhinterland duplex. The eastern part of the Supergroup is occupied by carbonate, conglomerate, quartzite, phyllite and proximal greywacke representing shelf facies, whereas the western part of the Supergroup has a totally carbonate free distal facies, with thin bands of arenite, representing deepwater facies. Metabasic volcanics occur near the base of Aravalli Supergroup. The ultramafic rocks, represented mainly by serpentinite and its metasomatic alteration products, occur in the Aravalli Supergroup in the Rakhabdev-Dungarpur area and in the area between Jharol and Gogunda. Intrusives within the Aravalli - Fold Belt include Jaisamand Granite, Ahar River Granite, Udaisagar and Dakan Granite, Salumbar Granite, Lakapa Granite and Dudar Gneiss. The Aravalli Supergroup has been subdivided into a tripartite lower Delwara Group, middle Debari Group and the upper Jharol Group. The Delwara Group forms the basal part of the Aravalli Supergroup initiating with basal conglomerate followed upwards by basic volcanics and associated pyroclastics, shallow marine carbonate and carbonaceous sediments with local development of phosphatic and non-phosphatic algal biostromes. The Debari Group is mainly composed of a thick sequence of conglomeratequartzite followed by dolomitic limestone and mica schist sequence. The Jharol Group is a thick flysch-like accumulation in a distal trough represented by dominantly phyllite and intercalated quartzite with minor carbonate rocks. The Debari and the Jharol Groups exposed in Rajasthan are represented by the Lunavada (subdivided into Kalinjara, Wagidora and Kadana Formation) and the Champaner Groups (subdivided into Lambia, Khandia, Narukot, Jaban, Shivrajpur, Rajgarh Formation) in Gujarat state.

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The Delhi Supergroup metasediments and related extrusive igneous rocks rest unconformably or with a structural discordance over the Bhilwara Supergroup in the northeastern and the central parts and over the Aravalli metasediments(?BGC) in the southwestern part of Rajasthan and contiguous parts of Gujarat. The Delhi Supergroup forming the Delhi fold belt of Rajasthan and Gujarat occurs in two sectors, viz., (1) in Alwar-Bayana-Khetri region, and (2) along a narrow linear belt (Main Delhi Synclinorium of Heron, 1953) forming the rib of the Aravalli mountain range in central and southwestern Rajasthan and northern Gujarat. The two sectors differ in terms of lithofacies, structure, magmatism and metallogeny. The Khetri fold belt (Khetri basin) has been identified and separated from the NDFB in the Khetri area by a basement-cover sequence separable from the main NDFB of the Alwar-Bayana-Lalsot basin. The major stratigraphic units of the Delhi Supergroup in the NDFB are the lower Raialo Group (mainly calcareous), the middle Alwar Group (mainly areanaceous and sub-divided into Rajgarh, Kankwarhi and Pratapgarh Formations in the Alwar-Jaipur basin and Jogipura, Badalgarh, Bayana and Damdama Formations in the Bayana-Lalsot basin) and the upper Ajabgarh Group (mainly argillaceous constituting a lower Kushalgarh Formation and an upper Weir Formation). Five lithotectionic units, namely, Basantgarh, Barotiya, Sendra, Rajgarh and Bhim, have been delineated from west to east, all of them together forming the SDFB in Rajasthan and Gujarat. Tectonic discordance in the form of early ductile shear zones and superposed brittle-ductile shear zones demarcate the boundary surfaces of each unit. Another group of rocks, namely, the Devgarh Group, occurring east of the Bhim Group, is tentatively included in the eastern basin. The rock types of the SDFB continue towards south into Gujarat. The magmatic activity during the Meso- to Neoproterozoic times are represented by the Sendra-Ambaji granite gneiss, Godhra granite gneiss, Erinpura Granite and Idar Granite. Several important alkaline and other igneous complexes of Gujarat include the Barda Igneous Complex, Alech Hill Complex, Osham Hill Complex, Mount Girnar Complex, Kanessara Igneous Complex, Rajula Suite of rocks, Chamardi-Choghat Complex, Pavagarh Volcanic Complex, Phenai Mata Complex, and Amba Dongar Complex. The Rajpura-Dariba-Bethumni belt of polymetallic sulphide mineralization in Aravalli Supergroup is rich in ores of zinc, lead, copper, silver, cadmium with minor gold and molybdenum. The Lower Aravalli rocks of Udaisagar-Umra Belts, Udaipur district host uranium and copper and phosporite deposits around Udaipur and Sallopat in Banswara district. The major Pb-Zn reserves are hosted in Bhilwara-Aravalli Supergroup rocks in Agucha, Kayar-Ghughra,

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Zawar, Rajpura-Dariba, Pur-Banera belts of Rajasthan with association of silver with Pb-Zn ores of Zawar, Rajpura-Dariba, Bharak areas of Udaipur, Rajsamand and Bhilwara districts. The major reserves of gold are from the Jagpura-Bhukia belt in Banswara district of Rajasthan. (Five parallel lode bearing) zones extending over a total strike length of 2 km are delineated. Minor occurrences are noted in Hinglaz Mata area (Dungarpur district) Ladera area (Jaipur district), and from associated copper ores of the Khetri copper belt. Besides, gold is also noted to occur in Pindwara-Watera belt, which is about 20 km long. PURANA BASINS Peninsular India witnessed the development of a number of large intracratonic/ pericratonic platformal sedimentary basins, referred to as Purana (meaning ‘old’) basins by Holland (!907), during late Palaeoproterozoic to Neoproterozoic period. The basins to the south of the Son-NarmadaTapti (SONATA) lineament occur as isolated basins, wheras the sediments to the north form a continuous Vindhyan Basin. Most of these basins except Kaladgi-Bhima, have contact with the mobile belts. This includes Cuddapah, Kaladgi-Bhima, Pakhal, Indravati, Abujhmar, Chhattisgarh and Vindhyan. Cuddapah Basin The Cuddapah Basin, the southernmost intracratonic basin, is crescent shaped with its convex side towards west and with a 450- km- long concave eastern thrusted contact. It lies above the Peninsular Gneiss and the linear greenstone belts of Kadiri, Gadwal and Velligallu with a marked nonconformity. The sedimentary fill is largely arenaceous and argillaceous with subordinate calcareous and dolomitic components, intruded by sills and basaltic flows. Calcareous precipitates dominate the Kurnool Group,deposited in a basin temponally and spatially overlapping the Cuddapah Supergroup. The Cuddapah Supergroup of rocks is subdivided into three groups, namely i) Papaghni Group ii) Chitravati Group iii) Nallamalai Group and one formation, namely iv) Srisailam Quartzite while Kurnool is retained as a separate single Group (Nagaraja Rao et al., 1987). The gencralised stratigraphy is shown in Table 6.

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Table 6: Stratigraphy of Cuddapah Supergroup and Kurnool Group ________________________________________________________________________ Major Rock Types

Supergroup/Group

Nandyal Shale Koilkuntla Limestone Paniam Quartzite

Kurnool Group

Owk Shale Narji Limestone Banganapalli Quartzite (diamoma bering conglomerate) ---------------------------------------------Unconformity-------------------------------------------Srisailam Quartzite ---------------------------------------------Unconformity-------------------------------------------Cumbum(Pullampet) Formation

Nallamalai Group

Bairenkonda Nagari Quartzite -------Angular unconformity----Gandikota Quartzite Tadpatri Formation

Cuddapah Chitravati Group

Supergroup

Pulivendla Quartzite --------Disconformity-------------Vempalle Formation

Papaghni Group

Gulcheru Quartzite ------------------------------------------Unconformity----------------------------------------------Archaean

This basin is historically famous for the world renowned diamonds like the Koh-i-noor, the Great Moghul, the Hope and the Orloff identified in the kimberlite diatremes of EDC at Wajrakarur in Anantapur district of Andhra Pradesh and Narayanpet in Mahbhubnagar district of Andhra Pradesh and lamproite dykes at Chelima-Zangamrajupalle and Krishna lamproite fields. Basemetal mineral deposits are known in the Cumbum Formation, Vempalle and Tadpatri Formations spread in Agnigundala, Zangamrajupalle-Varikunta, Rayavaram-Chinavani-Palle, and Gani-Kalva and Pulivendla belts. The largest barite deposit in the world with a reserve of 74 million tonne is located in Mangampeta in Cuddapah district in the Pullampet Shale of the Cuddapah Supergroup.

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Besides, this basin has huge reserves of cement-grade limestone in the Narji limestone in Kurnool and Palnad subbasins; chrysotile variety of asbestos mined in the Pulivendla serpentinised belt and phosphorite occurrences in Tadpatri, Cumbum Formations and Srisailam Quartzites of Cuddapah Supergroup. Kaladgi and Badami basin The Kaladgi and Badami sediments, exposed in northwestern Karnataka extending to South-Western Maharashtra, represent intracratonic basins occurring above the Archaean Dharwar greenstones with a nonconformity and partly covered by the uppermost cretaceous Tertiary Deccan Traps to its north and west.The sediments consist of orthoquartzite-argillite-carbonate association without volcanics and are least metamorphosed and deformed.. Cement-grade limestone of Bagalkot, haematite iron ore occurrences in Kerkalmati and usage of Kerur arenites as dimensional stone are the mineral resources found in these platformal sediments. Bhima Basin This is the smallest and youngest of the Purana basins located in Karnataka and Andhra Pradesh overlying Archaean basement rocks and covered by Deccan Traps and consists of clastic sediments and limestone. Mineral potential in the sediments of this basin includes cement-grade limestone, use of limestone as dimensional stone, nodules or layers of barytes, and phosphorite within shale. Pakhal Basin The Proterozoic Pakhal Basin extends in NW- SE direction for 350 km along the Pranhita – Godavari Valley from Andhra Pradesh in the SE to Maharashtra in the NW. The sediments of the basin occur as two mutually parallel belts, with about 40- km- wide stretch of Gondwana sediments separating them. The southwestern belt extends from Khammam in the southeast to Adilabad in the northwest and extends further into Maharashtra State. The northeastern belt extends from a little north of Bhadrachalam in the southeast, to a little beyond Chanda (Maharashtra) in the northwest. The Pakhal Basin includes unmetamorphosed (except locally) and unfossiliferous sediments of the Pakhal Supergroup, unconformably overlain by the rocks of Penganga Group and Sullavai Sandstone.The Pakhal Supergroup correlatable to the Cuddapah Supergroup rest on the Archaean Gneiss Complex. The Penganga Group of rocks is correlated with the rocks of Kurnool Group.

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Conglomerate, arkose, shale, dolomite and quartzite characterize the Pakhals, arkose and limestone the Penganga, and sandstone the Sullavai. Mineral resources includes streaks and disseminations of copper ores (chalcopyrite) in dolomite, shale or quartzite (with old workings) near Venkatapuram, Sarkar Ragaboyanagudem and Manikaran villages; barytes at Sripuram, Cheruvapuram and Pochavaram, clay at Marigundem, cement- and flux- grade limestone from Putunur, Cherla, and Madharam shales and west of Gunjeda; haematite iron ore from the ferruginous grits and quartzites extending from Bayyaram to Nilavanch; quartzite of this basin are used for refractory purposes in ferrosilicon industry; dimensional stones in Sullavai sandstone and Jakkaram arkose have been quarried from Chavai, Ramagundam and Amarapad areas. Indravati Basin The Proterozoic Indravati Basin in the Bastar Craton extends for 9000 km2 revealing flat- lying sandstone, shale, limestone and stromatolitic dolomite above the Archaean basement. Kimberliteclan rocks were discovered in this basin in Tokapal Kimberlite Field. The rocks of this basin are classified into three formations, of which the middle Kanger Formation represents a deep intracratonic basinal system with deposition of lime-mud used in cement and flux. Ampani Outlier An outlier, 220 km2 in extent, located west of Ampani reveals a 280- m- thick sequence of polymict conglomerate, subarkosic sandstone, siltstone and shale with calcareous sediments.This incomplete sequence has been correlated with the basal stage of the Indravati-Chhattisgarh Basin and Upper Kurnool equivalent of Cuddapah Basin (Balakrishnan and Babu, 1987). Abujhmar Basin The Abujhmar Plateau of Bastar district, Chhattisgarh State, exposes the sediments in a 3000 km2 rectilinear basin trending NNW-SSE overlying Bengpal, Bailadila and Nandgaon Groups. This basin is bounded on the west by the NNE-SSW- trending Kotri Lineament, on the south by the WNWESE trending lineament and the Indravati river, and the BIF of Bailadila Group underlie in the north. The sediments are metamorphosed locally, and carry a pile of lavas and intruded by dykes and sills. They are correlated with the Cuddapah Basin and Dhanjori Group of south Singhbhum and considered younger to Nandgaon Volcanics.

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Chhatisgarh Basin The Chhattisgarh Basin covers an area of 33,000 km2 in the Chhattisgarh State. It has a lower arenaceous and an upper argillaceous-calcareous sedimentary sequence and overlies the Archaean granite gneiss and supracrustals of Chilpi and Sonakhan Groups. The isolated basins of Indravati, Ampani and others are considered to have been part of a Greater Chhattisgarh Basin. They have tuffs and pyroclastics and had a rift history. The Chhattisgarh Basin is correlated with Lower Vindhyan, Indravati, Kurnool and Bhima basins of Peninsular India. Recent exploration for diamond in Pairi-Khariar basin has resulted in the discovery of five kimberlite pipes, two of which are diamondiferous. In this Mainpur Kimberlite Field, more than forty mineral indicator zones were detected by stream sediment sampling. Vindhyan Supergroup The Vindhyan Supergroup is 1 to 4 km thick and extends for about 60,000 km2 in a curvilinear basin surrounding the Bundelkhand Granite massif and bounded by the Son-Narmada-Tapti (SONATA) Lineament in the south, the Great Boundary Fault (GBF) of Rajasthan in the west and Ganga alluvium to its north. A small outlier, the Bhaunathpur Basin of Vindhyan Formation is situated south of Son River in Jharkhand. It is correlated with the Marwar Supergroup of Trans-Aravalli region of Rajasthan. Though the basin to the north of the SONATA and east of GBF is generally depicted as Vindhyan, it is represented in Himalaya by the Hazara Slate, Attock Slates, Simla Slate, Haimanta Group and the Salt Range beds. Vindhyan sedimentation commenced later than the Cuddapah Basin at around 1400 Ma and continued to the end of the Proterozoic to terminate before Cambrian (≈ 570 Ma). Several works have been carried out in this basin in the last 150 years in search of diamonds, limestone and dimensional stones. The Vindhyan Supergroup has been classified into four groups Semri, Kaimur, Rewa, and Bhander – and twenty-three formations. The Vindhyan basin is a major storehouse for limestone, diamonds, glass sands and building stones. Occurrence of copper, lead, zinc mineralization and native sulphur are noted at Semri in Bundelkhand; reported occurrence of galena from Narsinghpur; pyrites from Amjhor, Banjari and Rohtas Fort; dolomitic limestone, laterite, bauxite, ochre, clay and potash are known and explored to a varying degree.

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Trans-Aravalli Basins The Proterozoic-Mesozoic basins in the terrain west of the Aravalli-Delhi mobile belt are known as the Trans-Aravalli, bounded in the south by the Satpura trend and Son-Narmada rift and separated from the Himalayan belt in the north by the Lahore-Delhi shallow ridge. Extensive mafic and ultramafic rocks separate this Indus Basin from the Baluchistan Basin. The shelf of Rajasthan is connected to that of Gujarat with a ridge known as the Jaisalmer Mari Arch with the NW-SE Kanoi Fault truncating the Arch in Thar Desert. The Kutch Basin has Nagar Parkar Massif, Rann of Kutch depression and Mainland High. The Kathiawar uplift to the south and Radhanpur Barmer Arch to the east form boundaries. The Marwar Supergroup and the Mesozoic basins occurring in Rajasthan are correlated with the Vindhyan Supergroup. The Upper Proterozoic - Early Cambrian evaporite basin of 50,000km2 area, with the Hanseran Evaporite Group and Nagaur Group constituting the Marwar Supergroup, occurs in Trans-Aravalli Vindhyans, below 300m of Quaternary sediments in the semi-desert areas of Punjab, Haryana and Rajasthan extending beyond to the Salt Range occurrences. The evaporite sequence is 100-160m thick with halite, potassic salts, dolomite/dolomitic limestone, anhydrite/gypsum and clay.

GONDWANA BASINS The Gondwana sedimentation which was commenced in Late Carboniferous after the Hercynian orogeny (mid-Carboniferous), during which almost whole of land surface is represented by nondeposition except the Tethyan margins. Fall in sea level has been attributed to the glacio-eustatic drawdown during the accumulation of ice on uplifted high grounds. During late Carboniferous, the Gondwana supercontinent rotated clockwise almost 180o bringing the eastern and northern margin of Gondwanaland from equatorial position to high southern palaeolatitude resulting in widespread glacio-marine and rift-related sedimentation in many of the Gondwana basins during early Permian (Fig.5, Acharyya, 1998). Most part of Talchir sequence is unfossiliferous and the only fossil-bearing horizon within Talchir is at the top part associated with grey shale and limestone band that indicate a Sakmarian age. There is more than 500m thick Talchir sequence present in many basins. Recent borehole data by ONGC from west coast show the presence of recycled Upper Carboniferous palynomorphs, which is supposed to have been leaked from the Gondwana sediments underlying the Deccan Trap. Considering the stratigraphic position of Sakmarian fossil prompt us visualising the remote

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possibility of presence of some Upper Carboniferous sediments within the basal part of Talchir Formation in the deeper part of some basins. Palynoevents in Indian Gondwanas correlatable to the multiple marine transgressions caused by deglaciation covered part of Palaeo-Tethyan and Panthalassan margins and extended deep into the plate interior in almost all the continents except Antarctica during Sakmarian. Marine Eurydesma and Deltopecten fauna is found in India (both in peninsular and extrapeninsular basins) (Sinor,1922;Ghosh,1954; Dutt1965; Reed, 1932; Sahni & Srivastava,1956; Mishra et al.,1961; Dickins & Shah,1977). Two distinct groups of marine fossils associated with this transgression were initially reported from Upper part of Talchir Formation in Daltonganj, Manendragarh, Umaria, and Badhaura. Based on their recent finding of Eurydesma fauna in western part of Satpura basin Ghosh (2003) proposed a single marine front from east and considered the somewhat different fossil assemblage of Umaria as due to some local bathymetric reasons. He has excluded the fossils of Badhaura from the Gondwana gamut. During Karharbari Formation which is represented by coarse clastic dominated proximal sequence where fluvial processes dominate. e.g. presence of conglomerate at the contact of Barakar and Karharbari formation is quite common in many coalfields (e.g. Talchir, Ib Vally, Raniganj, Bisrampur, North Karanpura. A coarsening up sequence, starting with the shale facies at the top of Talchir Formation and ending at the top of Karharbari Formation is quite distinct. It may indicate the lowering of base level related to regressive phase of the sea. Scarcity of plant fossils might indicate that a periglacial environment persisted during the deposition of Karharbari Formation. However, the environment was conducive enough to promote sufficient growth of vegetation resulting in deposition of coal particularly where fluvial system was established. Deposition of coal bearing Permian Barakar & Raniganj formations under post glacial warmer condition in a fault-controlled subbasinal structure is quite distinct with enlargement of basinal area, which is more conspicuous in Damodar valley basin belt. The extinction of invertebrate at Palaeozoic & Mesozoic boundary is considered globally, though among the taxa Arthopods do not record any sharp break while ostracodes, Cochostracan & conodonts straddle this boundary. Where as land plants started to diversify their ecological niches much later than the marine invertebrates. The plants were more dependent on the climatic zonality and related regional lithogenetic variability while invertebrates were more acclimatic, global but determined by specifics of habit. During the transition of Permo-Triassic boundary paleoenvironment might brought drastic lithological changes in other Gondwana continents , but exclusively in the

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Indian continent, it can be stated that" a rotation/ movement of the Indian Gondwana during Permian period was halted at the P-T Boundary and thereby some of the Lithologenetic Belt transgressed in Triassic. Hence, favouring the Plant’s life to also transgress. The fossil spores & pollens are considered to reflect the past plant life accurately because of Taphonomic factors & hence episodic changes in lineages of presence of a short interval of the temporal scale in the Stratigraphy are well documented by the study of Sporae Dispersae. It is also well known in the Lower Permian, the climate was too favourable for triggering the rampant rise of the glossopteris flora , giving rise thereby to form huge coal deposits in Gondwana Basins. Therefore, it is opined that Palynology is the best suited tool for Gondwana Sequence because of their dominantly Non-marine depositional environment. More over, Palaeo-climate and the nature of precursor vegetal matter are the prime determinants for formation of different type of heterolithic coal in Indian Gondwana Basins. Since the introduction of the term"Gondwana" by Sir Medlicott (1872) no serious attempt was made to define the “Gondwana” into litho. Bio or chrono stratigraphic divisions and thereby to correlate them. Krishnan and Jacob (1956) had made an earliest recorded attempt to build up the International Stratigraphic Laxicon of Gondwana. Subsequently, in 1971 need of Stratigraphic standardization was actually conceived by adoption of a standard code by the Committee on Stratigraphic Nomenclature of India( Geo.Surv.Ind.Misc.Pub. no-20,1971) and which was ratified by the International SubCommittee on Stratigraphic Classification (ISSC) in 1972. There after no serious attempt was made to re-classify/ re-build the Gondwana Stratigraphy. The different Lithostratigraphic marker horizons of some selective Coalfields have already been prepared by the CW, GSI while carrying out 50 K Map compilation work, with the different Palyno-event-marker zones. General geological sequence of the respective coalfields is enclosed in Annexure-I It has been found that marine flooding surfaces within the Permian can be used to define sequence boundaries as well as time slots for dealing with the stratigraphy of the Gondwana Period. On this basis, the Gondwana lithosequences of different basins within India, could be grouped under specific time slots which may serve as powerful tools to arrive at a reasonable correlation framework, These time planes can be recognized as distinctive Gondwanide events. Plant fossils, so far reported from different Gondwana Basins are very wide ranging thus helping in no way to ascertain any specific age. Palynological data has its own constraints and till date is at best can be considered as corroborative. Vertebrate fossils are few in India, excepting few instances

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and in most cases are not very helpful in assigning pinpoint age. Moreover, any radiometric age data, for any of the formation in Gondwana basins of India is not available. Based on available tectonic, sedimentological, palaeontological and palaeomagnetic data total span of deposition of the Gondwana Sequence in India was considered to be initiated in Late Carboniferous after the Hercynian orogeny (mid-Carboniferous), by glaciations during which almost whole of land surface was represented by non-deposition except the Tethyan margins. Fall in sea level has been attributed to the glacio-eustatic drawdown during the accumulation of ice on uplifted high grounds (Veevers and Powell, 1987), which was subsequently affected by the severe erosion ,causing little sedimentation in the low lying peripheral parts in the north and south of Gondwanaland (Ilummedin and other basins of Africa in the North and the foreland basins, Parana-Karoo-Falkland-Elsworth-Bowen. in the south where Early Carboniferous/ Devonian rocks are preserved)and at places the sedimentary packages were totally eroded down even to Precambrian level. Abundance of coal and carbonaceous materials in the immediately succeeding Permian sediments also suggest an ameliorated humid climate and which was subsequently fluctuated gradually with time along with some what rifting of different basins. The end of deposition is considered as the product of major rifting activities as a result of Pangean break-up. Termination of Gondwana sedimentary deposition in India is considered to be terminated by the deposition of Bagra, Chikiala formations during early Cretaceous with the outpouring of Rajmahal Group of volcanics around 110-118 Ma, where as the Deccan Traps erupted around 65 Ma. Distensional tectonics, related to the movement of the Gondwana continents during Cretaceous, was accompanied by voluminous eruption of tholeiitic flood basalt and emplacement of sills and dykes. Igneous activity within the Gondwana basins of peninsular India is represented by dykes/sills of dolerite/basalt and lamprophyre and basic flows as found in many coalfields. Although there were differences in opinion regarding the actual age of these intrusive/effusive, it is more or less accepted that there are two major events of volcanic activity which can be correlated with the Rajmahal Trap and the Deccan Trap. Moreover in most of the cases these intrusives are found to follow the preexisting faults and never displaced by them. Trachyandesite porphyry is found to occur along the southern main boundary fault of Raigarh Coalfield, Mahanadi Valley Basin (Chakraborty, 1999).The rock is intrusive within the basement granite and also directly in contact with the Talchir Formation.

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Almost all the coalfields/basins of the Gondwana contain dykes/sills of dolerite/basalt of varying dimensions except the Talcher and Ib coalfields of Mahanadi Basin and Godavari Valley Basin. The origin of these intrusives have been linked with Deccan/Rajmahal Trap. Rajmahal Trap exposed along the western margin of Bengal Basin covering the Gondwana beds of Damodar-Rajmahal Gondwana basins. Volcanic flows in Meghalaya, better known as Sylhet Trap, are considered to be the equivalents of Rajmahal Trap. Lamprophyre dykes and sills occurring in Indian Gondwana form a consanguinous suite ranging from ultrabasic mica peridotite to micro-syenite assemblages. They are mainly reported from the Damodar Valley Basin close to Rajmahal and the preponderance diminishes towards west beyond Bokaro coalfield. They have a preference for coal seams and invade them at coal-sandstone interface. Rajahmundry Trap occupies about 35 sq km in Rajahmundry area at the north western fringe of Krishna Godavari Basin. Deep drilling by ONGC revealed presence of older trap equivalent to Rajmahal Trap below the Rajahmundry Trap (Biswas,1996).The upper flow (Rajahmundry Trap) overlies the Maastrichtian –Campanian sediments while the lower flow (Rajmahal equivalent) occurs below the Albian sediments Tripartite Classification of Gondwana exclusively on the basis of floral remains (e.g.-LowerGlossopteris, Middle -Dicrodium & Upper-Pterophyllum) is more acceptable and seems valid. The Middle Gondwana is also characterized by the record ofTriassic Reptiles. Amphibians and Estheriids. However, it is necessary to follow a uniform standard/code in conformity with the International practice while doing interbasinal correlation of different Gondwana basins of Peninsular India. As in widely

separated Gondwana basins closely related Unit/Member/Formation so far

defined are encountered with gross lithofacies variation along with diversified' fossil record, this Lacuna/Paradox still persists. The lithological/ sedimentation breaks, as depicted were not synchronous throughout and varied from one basin to basin, e.g. in the type area of Kamthi, there is a significant phase of preKamthi erosion, but in other part it is gradual. Thus the entire lower Gondwana sedimentation (as mentioned in the Annexur-I ) reflect both gradual/ conformable ( e.g Mahanadi Basin) and abrupt/sharp relation by the presence of paleosol zones( e.g. South Rewa Basin). To sort out these paradoxes, the attempt has been made to define the entire gamout of Gondwana sedimentation by Palyno-Events/ sequences. Indian Permian coal deposits of Gondwana Sequence are well known for their energy resources and to varying degrees for metallurgical purposes. Besides, recently it assumed

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significance repository of coal bed methane. Refractory clays are also present within Permian sediments. It was envisaged that an integral part of the project would be to locate new virgin potential area, particularly for coal and also for other commodities like refractor clay and uranium. . STRATIGRAPHIC CORRELATION OF GONDWANA SEQUENCE OF PENINSULAR INDIA INDIA Age

DamodarKoel

Rajmahal

Son

Sat pura

Mahanadi

Godavari

Early Cret Chikiala Late Jura-Early Cret

Bansa/Chandia

Jabalpur Bagra

Parsora

Up. Pachmarhi

Gangapur

Mid Jurassic Early Jurassic Late Triassic

Kota SupraPanchet

Dubrajpur

Kamthi (undifferenti ated)

(Tiki)

Up. Kamthi Dharmaram Maleri

late Mid. Triassic Bhimaram

Mid. Pachmarhi/ Denwa

Yerrapalli

early Mid Triassic

Early Triassic

Panchet

late Late Perm.

Raniganj

early Late Perm.

Barren Measures

late Early Perm.

Barakar

early Early Perm.

Talchir

Panchet

Pali Raniganj

Lr. Pachmarhi

Mid. Kamthi

Bijori

Raniganj

Lr. Kamthi

Barren Measures

Motur

Barren Measures

Barren Measures

Barakar

Barakar

Barakar

Barakar

Barakar

Talchir

Talchir

Talchir

Talchir

Talchir

DECCAN TRAP (CONTINENTAL BASALT) VOLCANISM Deccan Traps, the second most extensive geological formation in Peninsular India occupies major part (≈75%) of the Maharashtra State. It extends from Kutch in Gujarat in the west to as far as Belgaum in Karnataka in the south to Rajamundry in Andhra Pradesh in the southeast to Sirguja in Madhya Pradesh in the east to a few remnants in the bauxite laterites in Ranchi-Palamau in Jharkhand. They comprise tholeiitic flood basalts with some picrites. The traps rest on Upper Cretaceous strata. The isotopic ages indicate a 69 to 64 Ma period for the eruption with peak around a narrow span of 1 Ma around 65 Ma. The intertrappean fossils are Upper Cretaceous to Lower Eocene in age. The Bagh beds in lower Narmada Valley and the Lametas of Jabalpur constitute important infratrappean datums. Native copper has been reported from the Deccan basalts near

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Handigund (16°25': 75°05'), Belgaum district, Karnataka. Magnetite, haematite and maghemite are other associated minerals.

INDO-GANGETIC – BRAHMAPUTRA PLAIN Indo-Gangetic Plain extends from Aravalli - Delhi ridge in the west to the Rajmahal hills in the east. Indo-Gangetic (Ganga) Plain occupies the major part of the States of Haryana and Punjab with the upper and part of the middle part of the Ganga Plain in Uttar Pradesh. The rest of the middle part of the Ganga Plain falls in Bihar and the terminal part comes in West Bengal where the Bhagirathi river Plains to Indo-Bangladesh border in the east. The Brahmaputra Plains cover the whole of Assam Plains. The Ganga Plain is a part of the 'Indo - Gangetic Foreland Basin'. This foreland basin is developed during upper Tertiary and is closely related to the birth and rise of Himalaya. This Plain exposes fluvial sediments of Quaternary period. Subsurface exploration, particularly for petroleum, has revealed that a thick pile of alluvium rests over the Siwalik sequence of Neogene - Early Pleistocene period. This alluvium constitutes sedimentary fill of the Ganga Foredeep – the youngest foreland basin. The foredeep sediments extend much to the south of the depositional boundary of the Siwalik Foredeep and rest over the Cratonic rocks of Precambrian period. The thickness of the alluvium increases towards north and is maximum adjacent to the Foot Hill Fault (FHF) that marks the northern limit of the Ganga Foredeep Basin.

EXTRA-PENINSULAR REGION The Himalayan mountain chain constituting the Extra- Peninsular Region resulted due to continent - continent collision process during Tertiary period. The evolution of the Himalaya – the largest of the mountain ranges – can be described in a simple way (Balasubrahmanyan, 2006). A sea named variously as the Tethys or Purana evolved to the north of the Indian Shield providing the base for Lesser Himalaya characteristics at 2000 Ma ago. The withdrawal of this sea marks the beginning and the breakway of Tibetan microcontinent and development of Tethys Himalaya. During the tectonically unstable period between Permian and Cretaceous, submarine topography changed with formation of volcanic chain of islands. The movement of Indian plate over 7000 km to the north subsequent to the breaking from Africa-Madagascar resulted in notable changes in the geography of Asia, with Deccan Trap volcanism and formation of the Indo-Tsangpo suture welding India with the rest of Asia. The contemporary deformation and metamorphism resulted in initiation of major crustal

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fractures of the Main Central Thrust and Main Boundary Thrust and evolution of the Siwalik basin and leucogranite intrusions of Himalaya. The Sub-Himalaya, Lesser Himalaya, Higher Himalaya and the Trans-Himalaya are the morphotectonic and lithostratigraphic zones from south to north. (i) The Sub-Himalaya lies in the extreme south and separated from the northern Lesser Himalaya by Main Boundary Thrust. This is a 10- to 50- km- wide zone immediately north of the GangaBrahmaputra alluvium of Miocene to Tertiary age. The Molasse belt in Siwalik and other foothills with the Main Frontal Thrust (MFT) limit the orogenic margins of the Himalaya against the Ganga Brahmaputra Plains.This is constituted of Early Tertiary (Subathu-Dagshai-Kasauli-ChunabatiYinkiong) and Late Tertiary (Siwalik) rocks. There are two belts of Sub-Himalayan Tertiary coalfields trending WNW-ESE in JammuKashmir. (ii) The Lesser Himalaya is a 60- to 80- km- wide zone stretching between the Main Boundary Thrust(MBT) in the south and the Main Central Thrust (MCT) in the north and is made up of autochthonous sedimentaries of Precambrian (Shali-Deoban-Tejam belt) and Palaeozoic-Mesozoic age (Krol-Tal-Subathu) thrust overlain by epizonal metamorphic(Chail-Ramgarh) and mesozonal metamorphic(Jutogh-Munsiari) thrust sheets. At places, the crystalline thrust sheets have been removed by deep erosion in river valleys exposing the autochthonous sedimentaries of ShaliDegboon-Tejam belt as tectonic windows such as Kishtwar window, Kulu-Rampur window, Shali window, Chareota window, etc. It has Riphean to Palaeozoic platform sediments with some characters of the Peninsular Shield and is overlain by thrust sheets and crystalline nappes. (iii) The Higher Himalaya is a 10- to 15- km- wide zone of Precambrian crystallines exhumed along the greatest uplifted terrain with highest peaks of Himalaya (NunKun, Leopargial, Kedarnath, Badrinath, Nanda Devi, Api, Dhaulagiri, Everest, Kanchanjunga, etc.), made up of katazonal metamorphics (kyanite-sillimanite gneisses, migmatites and calc-silicates) and intruded by granites some of which are of Tertiary age. Metamorphic crystalline sequences of the Higher Himalaya are overlain unconformably by predominantly marine sediments of Paleozoic and Mesozoic age in parts of Kashmir, Spiti-Zanskar (H.P.) and Kumaon Garhwal (U.P.) in the Higher Himalayan Tethyan basins. Sporadic occurrences of bedded barite and polymetallic sulphide mineralisation have been reported from Garbyang and Ralam Formations of Uttar Pradesh. (iv)The Tethys Himalaya extends to the south of the Trans - Himalayan ranges and comprises predominantly fossiliferous sediments ranging in age from Late Proterozoic to Eocene. This belt

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bears an unconformable or faulted contact with the Higher Himalaya, the basement to the Tethyan sedimentary sequence. Tethyan sequence containing fossiliferous Palaeozoic rocks is well exposed in Garhwal and Kumaon region, Kinnaur basin, Lahul and Spiti in Himachal Himalaya, as Lachi, So Lamo Formation in Sikkim Himalaya. The Martoli Group, about 4500 m thick, consisting of phyllites, mica schist, quartzite, with lenticles of marble in the upper part overlies the Central Crystallines with a tectonic contact. This Group is also intruded by granite, pegmatite and quartz veins. Earlier workers considered it to be of Precambrian age, forming the basement for the fossiliferous Palaeozoic sequence. (v) Trans - Himalaya, lies to the north of the Indus Suture Zone in Ladakh region and extends eastward into Tibet. It is characterized by a huge discontinuous, nearly 2600-km-long batholith comprising rocks ranging from gabbro to granite. The Trans-Himalayan lithotectonic units north of the Indus Suture Zone includes the Ladakh batholith/magmatic arc (Ladakh Granitoid Complex), Shyok Suture Zone, Karakoram batholith/magmatic arc (KGC) and the Karakoram Supergroup and the Tso Morari Crystalline Complex This zone represents the lithounits brought together during the Eocene collision of North Indian plate elements with the trailing edge of Eurasian plate, i.e. the Lhasa block. The Indus-Tsangpo suture zone (ITSZ) extends as a linear belt all along the IndusTsangpo valleys between the Higher Himalaya to the south and Karakorum – Gangdse ranges to the north. It is best exposed for about 500 km in the Ladakh region and is referred as the Indus suture zone. This narrow linear belt comprises two units, tectonically juxtaposed, one including basal ophiolite followed by basic volcanics and flyschoid sediments and another by ophiolitic melange. This zone is separated from the Tethys Himalaya by Dras Thrust in the south and from the Karakorum Tethys and Granitoid Complex by the Shyok Thrust in the north. Two belts of granitoid complexes lie in the Trans-Himalayan region of Ladakh. The northern belt called the Karakorum Granitoid Complex, lies to the north of the Indus Suture Zone and intrudes the Late Palaeozoic metamorphites. The southern belt called the Ladakh Granitoid Complex intrudes the Upper Cretaceous-Eocene rocks of the Indus Suture Zone. Karakorum Granitoid Complex (KGC) is a linear batholithic body, about 20 km wide and 150 km long stretching NW-SE and occupies higher peaks of the Eastern Karakorum and the Pangong mountains.This granitoid belt extends into the Western Karakorum across Baura range, Hispar, Biafo to the west of Baltaro. The ITSZ branches into two thrusts―Main Mantle and Main Karakorum―with rocks in between comprising the rocks of the Kohistan Zone. Along the Karakorum Highway, in a north to

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south section, the K2 consists of Yasin flyschoid sediments, Chitra volcanics, the Kohistan-Ladakh batholith, the Chilas Layered Complex and the Jijal Complex. Arunachal Himalaya The correlation of Arunachal geology with the other parts of Himalaya is a complex job fraught with uncertaintes. Hence the geology has been dicussed separately following broad Himalayan classification. Bomdila Group comprise a sequence of low-to medium-grade metasediments with associated gneisses and younger granitoids occupying expansive areas throughout the lesser Himalaya of Arunachal Pradesh from Siang valley in the east to Kameng valley and Bhutan in the west. Similar sequence of rocks is known as Ithun Formation and Rikor Group in Dibang valley and Lohit valley areas. Tilung Formation and Namdhapa Crystalline Complex are also included in this group. The granitic and gneissic rocks of Bomdila Group are garnet bearing and highly deformed and mylonitised under ductile domains. The ultramafic bodies intruding the para-metamorphites of Ithun Formation in Myodia area have minor amounts of Platinum Group of elements.The lesser Himalayan zones of Arunachal Pradesh are classified into two parts: (i) The Kameng, Subansisri and Siang Himalaya and (ii) Lohit Himalayan). In KamengSubansisri-Siag Himalaya, the Tertiaries, Gondwana, Bichom Group and the metamorphic rocks are regionally disposed in ENE-WSW to NE-SW trend. In the lower Himalayan region NNE-SSW to NS trends are superimposed on the above regional trends. In the Lohit Himalayas the rocks exposed belong to Bomdila Group, Tenga and Miri Formations and Upper Siwaliks. A diorite-granodiorite Complex considered to be of Late Paleozoic age is also exposed in Lohit Himalayas . From west to east the Bomdila Group is overlain by the Dirang Formation till east of Subansiri River. In Siyom and Siang River sections, Sela Group of Higher Himalaya comprising high-grade schists, migmatites and gneisses overlie the Dirang schists in the higher Himalaya of Kameng district of Arunachal. Rocks of khondalite affinity of Southern Granulite Belt are noticed in the form of graphite-bearing quartz-biotite-sillimanite schists in the Simi Member of Khetabari Formation of Precambrian age in Upper Subansiri district.The NNW-SSE Trans-Himalayan Belt of Arunachal Pradesh exposed in the Upper Siang, Upper Dibang and Lohit valley areas is juxtaposed against the rocks of the Himalayan belt along the Tidding Suture. The Trans-Himalayan belt comprises two distinct lithopackages viz, i) the suture package comprising Yang Sang Chu Formation and Tidding Formation with serpentinites, and metavolcanics and ii) the Lohit Granitoid Complex and the Etalin Formation, the latter occurring as restites. The total assemblage of the suture package resembles an ophiolitic melange.

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The Upper Tertiary (Mio-Pliocene) molassic sediments constituting the Siwalik Group occurs as a linear belt along the foothills of Arunachal Pradesh extending from Bhutan to just east of Pasighat where it is overlapped by the alluvium. However, it re-appears on the left bank of Dibang River where it is tectonically overlain by the rocks of the Bomdila Group along the Roing Fault, which is considered as the continuation of the Mishimi Thrust. The Siwalik Group is bounded to the north by the Main Boundary Fault along which the Pre-Tertiary sequence has been brought over and its southern limit with the alluvium of the Brahmaputra River. The Tertiary sequence of Arunachal Pradesh is classified into Dafla, Subansiri and Kimin Formations broadly corresponding to the Lower, Middle and Upper sub-divisions of the Siwalik Group of northwestern Himalaya and are considered as the northward extension of the Tertiary sequence of Assam. Massive and vesicular basaltic and andesitic rocks of Abor volcanics of Phanerozoic age are associated with Miri Quartzites. The rocks overlying the Miri Quartzite are cherts, shales, black shales and carbonates, developed in the western flank of Subansiri valley, Igo valley, Basar-Along areas and in Siang valley areas in Arunachal Pradesh.

CENOZOIC FORMATIONS OF THE SHIELD In the southern peninsular India, the Tertiary sequence is well developed. In Tamil Nadu, the Ariyalur Group of Upper Cretaceous is overlain conformably by a sequence of limestone, calcareous shale/mud, clay and sandstone of Paleocene age. This sequence is named as Niniyur Formation in the Tiruchirapalli sub-basin with its equivalent in Pondicherry sub-basin as Karasur Formation. Rocks of Mio-Pliocene age (early Neogene) termed as Cuddalore Formation occupy a large area along the coast overlapping the Mesozoic sediments and at places over the crystalline basement. Cuddalore Formation contains large quantities of fossil wood around Tiruvakkarai in Villupuram District which have been declared and maintained as a National Fossil Wood Park by GSI. Thick lignite beds at Neyveli in Cuddalore District were originally thought to belong to Cuddalore Formation. In the coastal tract of Tuticorin and Tirunelveli districts, the Mio-Pliocene group is represented by fine-grained limestone and gritty sandstone intercalated with pebble beds, found to overlie the Archaean unconformably and below the Recent formations. These are referred to as Panamparai Sandstone. Along the west coast of Kanyakumari district, a sequence of sandstone and clay with thin lignite seams is recorded. These are correlated to Warkhali beds of Mio-Pliocene age of south Kerala and are similar to Cuddalore Formation. Beds of shelly limestone, clay and grit,

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intercalated with lignite layers are recognised in the southern coastal tracts of South Kanara district; these quasi-indurated sequences of sediments are considered to be the extension of Warkhali Beds occupying further south of Kerala. These Miocene beds, about 20 m thick and unconformably overlying the weathered gneisses and charnockites are capped by laterites. In the East Coast, the Tertiary rocks are represented by algal limestone in subcrops at Debagram, Jaguli, Jalangi and parts of Medinipur, Bankura, Bardhaman and Birbhum Districts of West Bengal. Recently, Distichoplax biserialis, an index fossil of the Palaeocene age was recognized in the subcrop samples from boreholes of ONGC . During early Eocene period, upheaval confined along

a narrow NE-SW-trending track

resulted in intrusion of ultramafic cumulates and volcanic members resulting in the formation of the Ophiolite suite of rocks comprising tectonised peridotite, cumulate ultramafics including dunite, peridotites and pyroxenites that are exposed in the eastern fringe of North-Eastern Region for about 200 km from Moreh in Manipur in south to north-east of Chiphur in Nagaland in north. Mid-Eocene sediment is represented by polymictic conglomerate, tuffaceous greywacke and lithic feldspathic arenite. Chromite is the main economic mineral of the ophiolite suite of rocks with Cr2O3 >45% and low TiO2. Parts of the ophiolite belt have been explored for chromite and other metals like Ni, Co, Cu, etc. The Tertiary rocks of northeast India rest over the weathered platforms of Precambrian rocks, and these comprise of both shelf and geosynclinal-facies sediments of Eocene age represented by the Jaintia and Disang Groups respectively. The overlying Barail (Oligocene), Surma (Lower Miocene), Tipam (Upper Miocene), Dupi tila (Mio-Pliocene) and Dihing (Pliocene) Groups also represent both shelf and geosynclinal facies. The Tertiary sedimentary history of Assam is an integral part of the tectono-sedimentary setting of the Tertiary sediments of the north-east India and is influenced by the prominent ‘Brahmaputra Arch’ running parallel to Brahmaputra River. The shelf-facies sediments (Jaintia Group) of Eocene age are calcareous and abundantly fossiliferous. In Meghalaya, Tertiary coal occurrences are recorded in Jaintia Group.

QUATERNARY FORMATIONS The Quaternary sediments in the peninsular India occur along the coastal tracts and inland river valleys by narrow continuous palaeo-beach ridges, interrupted by the prograding deltas of major rivers. They are represented by thick blankets of alluvium, gravel and colluvial deposits, beach sand,

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kankar, soils of various types and laterite. The Quaternary sediments were laid down in four major depositional environments, namely fluvial, fluvio- marine, marine and aeolian. The Quaternaries in Rajasthan and Gujarat are assorted deposits of aeolian, fluvial and lacustrine origin. They occur mostly in a large tract in western Rajasthan known as the Thar Desert. One of the important Quaternary episode in Gujarat is the formation of the Rann Surface,—a vast, marshy, saline tract extending for about 300 km in east-west direction in Kachchha region of Gujarat. A major part of the area flanking the Brahmaputra River in Lower and Upper Assam is covered by thick Quaternary fluvial sequence. Quaternary sequence located in Imphal valley of Manipur are of both laccustrine and fluvial types. Recent deposits in northeast India are represented by sand-silt-clay sequence in Brahmaputra and Surma River valleys in Assam and in the foot hills of Garo and Khasi hills of Meghalaya. Minor recent sediments also occur in Manipur, Mizoram and Nagaland. The Quaternary sand deposits along the coastal tracts of Kerala and Tamil Nadu are economically exploitable for ilmenite, rutile, zircon and monazite. Andaman & Nicobar Islands The Andaman-Nicobar Islands represent part of an arcuate island-arc chain, running from Myanmar to Indonesia to Indo-Sumatra subduction zone, flanked on the west by the Bay of Bengal and on the east by the Andaman Sea, constituting the southern most part of the Indian subcontinent covering an area of 8249 km2. The Andaman & Nicobar (A & N) Islands represent the subaerial part of the submarine fore-arc ridge of the Indonesian Island-arc system. An active zone of subduction along the Andaman-Java trench lies on the west of the Andaman-Nicobar Islands and continues southward into Indonesia. Underthusting of the Indian oceanic plate below the Eurasian plate since Cretaceous to present day along this subduction resulted in the formation of a wide accretionary prism and upbuilding of a high forarc-outerarc ridge known as Andaman-Nicobar ridge. The ophiolite occurrences in Andaman Islands are interpreted as thrust slices of oceanic crust scraped off the subducting slab at the toe of the accretionary complex. The outerarc-forearc terrain constituting the Andaman-Nicobar Islands is characterized by a complex mosaic of different geological provinces each having its own record of origin and geological evolution vis-a-vis mineral potentiality. Rocks of the Andaman Islands are technically thrusted into a narrow north-southtrending and linear belt paralleling the north-south trend of the Andaman-Java subduction. Older

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continental metamorphic rocks occur as small enclaves within the ophiolite-melange packages. Ophiolitc rocks in Andaman occur as north-south trending dismembered units of subhorizontal sheets thrusted over the much younger Andaman Flysch. They are Cretaceous-Palaeocene in age and are intermittently exposed from the saddle reef of North Andaman to almost the southern tip of the Great Nicobar Island. Rutland Island in the southern tip of South Andaman Island hosts the largest exposure of the ophiolites. The Ophiolites, their cover sediments and the Andaman Flysh together are folded into an open anticline (Ray, 1982). Sets of mesoscopic folds occur in all the sedimentary units associated with ophiolites. Recent Volcanism in Andaman & Nicobar Islands In Andaman & Nicobar Islands, Narcondam and Barren are the two small volcanic islands of Quaternary age, located about 100 km north and northeast of Port Blair on Andaman Sea. The Narcondam is considered to be a dormant type while the Barren has the history of recurring volcanic eruption since pre-historic age (Halder et al., 1992). The Barren Island volcano, the only active volcano in the Indian subcontinent has recently exploded during May 1991 after lying dormant for a long time.Subsequently it erupted again during 2005, 2006 and in 2009. The Barren Island volcano is characterized by resurgent volcanism, with three distinct volcanic episodes recorded so far. An initial submarine volcanism, possibly taking place in late to postPleistocene time formed a giant volcanic cone representing the ancestral / primordial Barren Island. This ancient volcanic cone was at times blown out and a thick pile of pyroclastics got deposited over the surface of the relict cauldron. Olivine basalt represents the first phase of eruption, while the second phase witnessed the eruption of high-alumina olivine basalt. The recent basaltic andesite eruption contains phenocrysts of plagioclase, diopsite, augite and titanomagnetite set in a hyalopilitic groundmass. Lakshadweep Islands The Union Territory of Lakshadweep forms a NE-SW-trending archipelago in the Laccadive-Chagos ridge system in the Arabian Sea, 220-440 km off the west coast of India. It is located between 8º and 12º30" North latitude and 71º and 74 º East longitudes and consists of twelve atolls, three reefs and five submerged banks, with a total of about 36 islands and islets, roughly covering 32 sq km. Geologically, all the islands are made up of coralline limestone and calcareous coralline sand and its variants. Mineral occurrences include Coralline Limestone,Calcareous sand with high CaO content

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and Guano deposits (P2O5- 8-11.72%) in Pilli island 30 km NW of Kavaratti. (0.12 million tonnes estimated by IBM in 1970).

MINERAL RESOURCES OF INDIA INTRODUCTION

India has a rich tradition of mineral exploration. Innumerable old workings, slag heaps are the tell tale signs of this glorious tradition. The flourishing diamond industry in the Deccan peninsula mainly in the Golconda kingdom, has attracted the world’s attention during the historical time. Copper, iron, and gold were also used locally since the day of Indus valley civilizations. East India Company started exploration for coal in the eighteenth century with setting up of Geological Survey of India, the premier Earth science organisation and the second oldest survey of the country, in 1851 for the systematic geological survey and prospecting for coal. India was a notable producer of gold in the early part of twentieth century and major exporter of mica, sillimanite, kyanite, magnetite and chromite. Metallurgical industry started with the setting up of steel plants at Burnpur, Jamshedpur and copper smelter at Ghatsila. Second World War created great demand for various minerals and metals including those of strategic importance viz tungsten. Industrial policy formulated after Independence, brought about a radical change in the mining and metallurgical industry. During the post Independence period, GSI has embarked upon the exploration for minerals particularly in favourable geological milieu spread over the Dharwar, Bastar, Singhbhum and Aravalli cratons. The investigations carried out since 1960s provide us first hand information of different mineral occurrences as well as their potential. Keeping in tune with the modern trends of mineral exploration, the GSI oriented its programmes through multidisciplinary surveys and from time to time equipped with state-of-the-art laboratories to back up its various exploration programmes. The efforts have led to discovery of several mineral deposits in virgin areas in different parts of the country. A few other central and state government organisations were also involved in mineral exploration now and then, mostly in collaboration with foreign organisations. The liberalization of our National Mineral Policy in 1993 paved the way for entry of private entrepreneurs, including those from overseas for carrying out mineral exploration. The database developed by GSI has been found very useful for taking investment decisions by the Multi National Companies. An ore or mineral deposit represents a geochemically anomalous concentration of elements in a very limited sector of the crust. The crustal elements have to undergo enrichment upto several

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orders to attain the status of an economic deposit. The concentration of Clarke varies from element to element depending on the economic utilization. The genesis of economic deposits is therefore essentially a question of enrichment. The crustal processes associated with crustal growth and recycling leading to metal concentration and formation of deposits is refeered by the term’metallogeny’. In the Indian context major metallogenic episodes have taken place during Archaean, Archaean-Proterozoic Transition and Proterozoic proper. Thus large deposits of base metal and basemetal-noble metals, Iron, manganese and chromium etc were formed in distinct episodes mostly from Archaean to Mesoproterozoic. Crustal evolution during Archaean: The Archaean forms the formative stages of the earth’s history, core segregation, major out gassing, meteoric bombardment and formation of primeval crust (Piranjo 1992). Archaean heat flow between 3.8 and 2.5 Ga is estimated to have been 2.5 to 4 times its present value. As a result lithosphere was presumably thin and somewhat buoyant. Subduction, if any, was probably little developed and mantle convection gave rise to a series of small jostling lithospheric plates. Initially these were made-up of mafic and ultramafic rocks. Later perhaps in response to partial melting of this lithosphere and the products of erosion of the early consolidated magmas, ore felsic rocks were formed and accreted leading to the formation of first sialic microplates. The aggregation of these micropltaes could have given rise to Protocontinents, and eventually together near continental size cratonic areas. These cratons were composed of granitic rocks and greenstone belts. The Proterozoic Eon was the most significant one when intraplate tectonics played a major role in earth’s evolution of magmatism, metamorphism and ore genesis. The Archaean Proterozoic boundary was a major turning point in crustal evolution and represents a diachronous and transitional period ranging from 3 Ga to 2.5 Ga. Massive crustal growth, lithospheric thickening, decrease in heat flow and a possible change in mantle convection pattern occurred, The presence of an unconformity is typical separating highly deformed Archaean rocks from the little deformed Proterozoic cratonic sequences. A major intrusive event characterised by large-scale granitic magmatism is identified between 2.67 and 2.5 Ga .The aggregation of a super continental mass resulted in the accumulation of heat in the mantle beneath.

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Genesis and localisation of economic deposits:The grouping of commercial types of ore deposits is based on a single genetic classification ie endogenous, exogenous and metamorphogenic series. The endogenic series incorporates magmatic, pegmatitic, metasomatic greisen type etc, carbonatite, skarn, plutonogenic hydrothermal, volcanogenic hydrothermal, massive sulfides and stratiform type groups. The exogenic include weathering, placer, sedimentary, mineralised waters and brines. Endogenic cycle and endogenic deposits: Magmatic deposits: Magmatic cycle (both extrusive and intrusives) is responsible for concentration of many important metallic deposits. A genetic connection between both is often difficult to establish because exhalation carrying ore minerals get intermixed with the hydrosphere and atmosphere and are deposited as chemogenic sediments. To this class belong the sedimentary exhalative deposits closely related to time and space with volcanic episodes (e.g. BIF, deposits of stratiform Zinc, Volcanic Hosted Massive type Sulphide type Pb-Zn-Cu deposits). Ores may be genetically related to specific intrusives as magmatic concentration and magmatic emanation exuded from magma during its consolidation. Some of them are early magmatic and late magmatic with reference to the intrusion. The podiform chromite mineralsiation associated with ultramafic rocks are examples of deposits of early magmatic concentration. Hydrothermal origin is attributed to many of the metalliferous deposits of copper, gold, lead etc and fluorite, barite deposits. The mineral rich solutions migrated from magma source gets precipatetd at different levels in the crust along strcturally favourable traps depending on the ambient pressure temperature conditions of precipitation at different crustal levels. The following table summarizes some empirical data on the igneous rock-ore linkage. Rock Type

Associated Ore

Kimberlite and Lamproite

Diamond

Dunite-Peridotite, Pyroxenite

Chromite, Nickel, Platinum Group

Norite-Gabbro- Anorthosite

PGE, Ti and Vanadium bearing Magnetite, native copper, silver, cobalt, nickel

Dolerite, diorite, monzonite

Magnetite, copper, gold

Granodiorite, quartz monzonite

Porphyry copper,-gold-Mo-Ag-

Syenite

Magnetite, gold

Nephelene syenite

Corundum

Granite and granite pegmatite

Tin-Tungsten, Uranium, radium, beryl, tourmaline

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Exogenic cycle and exogenic deposits: The mineral deposits formed at deeper zones of the crust under high temperature and pressure conditions are unstable in the interface of atmosphere, hydrosphere and biosphere which are characterised by low temperature, low pressure and abundant water. All these lead to geochemical fractionation of elements, which incidentally leads to formation of a number of mineral deposits. Enrichment of iron, Nickel, and aluminium takes place in the weathering cycle under warm tropical conditions in the form of laterite and bauxite cappings. This type of deposits is abundant in the Precambrian shield of Indian Peninsula. It represents insitu products of interaction of the stable crustal blocks with the dynamic atmosphere. Mechanical concentration of resistant minerals results in the formation of placer deposits of monazite, ilmenite, garnet, gold, cassiterite, diamond, platinum etc. The dynamic agencies of hydrologic cycle act upon crustal blocks and bring about concentration of heavy minerals. Examples of this type of deposits are the beach placers of Ilmenitemagnetite bearing sand placers of Kerala - Konkan Coast, diamond placers in Madhya Pradesh and Wairagarh, Tin placers of Bastar District,etc. Another important example of exogenous deposits is coal. This is important source of energy in the country. Large deposits of coal are found associated with Gondwana sediments. These are formed by large scale deposition of vegetation materials entrapped in the alluvial sediments brought in by the rivers which during the course of geologic time due to consolidation and lithification transformed into coal beds. As per the National Mineral Policy,2008, which emphasized for non-fuel and non-coal minerals, that is, deposits locked at depth, mineral occurrences of India is presented in detail for geologically potential areas in consonance with the national policy goals.Only significant mineralization with possible economic significance have been described. DIAMOND India has the distinction of prducing many of the historically famous diamonds like the Kohinoor (186 ct), the Great Moghul (787 ct), the Hope (67ct), Nizam (440ct), Pitt/Regent (410 ct), Orloff(300 ct) and Daryainoor(185 ct).Till the discovery of the Brazilian diamond fields, India was leading in diamond mining.

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Diamond occurrences in India are quite widespread. The known areas of occurrences of diamond source rocks are broadly grouped into three diamond provinces, namely the South Indian Diamond Province (SIDP), the Central Indian Diamond Province (CIDP) and the East Indian Diamond Province (EIDP). Each of these Provinces extends approximately over an area of 100,000 km2 and includes both primary (Kimberlites/Lamproites) and secondary source rocks (conglomerates and gravels) for diamond. The SIDP is confined to the Dharwar Craton in the states of Andhra Pradesh, Karnataka and Maharashtra, the CIDP to the Aravalli Craton in the states of Madhya Pradesh, Rajasthan and Uttar Pradesh and the EIDP to the Bastar and Singhbhum Cratons in the states of Maharashtra, Chhattishgarh, Orissa, Jharkhand and Madhya Pradesh. Considering the Cratons and presence of diamonds and the source rocks, areas have been prognosticated for kimberlite search in India.They are: (1) South Indian Diamond Province (SIDP) including East Dharwar Craton and adjoining Dharwar Mobile Belt; (2) West Dharwar Province; (3) East Bastar Craton including parts of Eastern Ghat Mobile Belt (EGMB); (4) West Bastar Craton; (5) Southern part of Bundelkhand – Aravalli Craton ; (6) North of Central Indian Suture (CIS); (7) Southern part of Singhbhum Craton including Singhbhum Mobile Belt; (8) Raigarh Mobile Belt; (9) Structural Corridor of Son – Narmada rift zone; (10) Structural Corridor of Tapti Lineament Zone; (11) Mahanadi Gondwana Graben and (12) Godavari Gondwana Graben. The SIDP consists of both primary and secondary source rocks of diamond. The kimberlites localised within the Eastern block of the Dharwar Craton are grouped into four kimberlite fields, viz. Wajrakarur Kimberlite Field (WKF), Narayanpet Kimberlite Field (NKF),Tungabhadra Kimberlite Field(TKF) and Raichur Kimberlite Field(RKF).Three N-S zones, viz. (i) the eastern zone of alkaline syenites / alkali granites (1600–1400 Ma) extending from the eastern tectonic contact of EGMB with DC to the eastern margin of CB, (ii) the middle zone of lamproites (~1350 Ma) covering Nallamalai Fold Belt (NFB) and PGC along the northeastern and northern margin of CB, and (iii) the western zone of kimberlites (~1100 Ma) covering PGC to the west of CB, are recognised. The major lamproite dykes occurring along the eastern margin of the Craton i.e. within the Nallamalai Fold Belt (NFB) and close to the north eastern margin of the Cuddapah basin are included in the Chelima- Zangamrajupalle Lamproite Field (CLF) and Jaggayyapeta-Krishna Lamproite Field (JLF) respectively.

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Until now, only the WKF is found to contain diamondiferous pipes.Twenty-one kimberlites of WKF are distributed in three clusters viz., Wajrakarur-Lattavaram cluster (Pipe 1-13), Chigicherla cluster (CC 1-5) and Kalyandurg cluster (KL 1-3). There are 34 kimberlite bodies in NKF distributed in Kotakunda (KK1-7), Maddur (MK 1-11), Narayanpet (NK 1-10) and Bhima clusters (BK 1-5 and RK-1). The lamproites are distributed in 12 clusters. Mineralogical composition of WKF indicates their derivation from shallower depths above the diamond window in the inhomogenous mantle.The diamond incidences (in carat per hundred tones-cpht) of Pipe 1 to 13 are 0.3, 3.5, 0.78 to 1, and 7.9 with the high value of 45 in the overburden of Pipe 7. Secondary sourced diamonds in South India can be traced to the Proterozoic Cumbum conglomerate (Cuddapah Supergroup), Banganapalle conglomerate (Kurnool Group) and UpperTertiary Gollapalli/Malavalli conglomerate from the extensive old workings. The Banganapalle conglomerate, explored by various agencies, has incidence of diamond – 0 to 35 cpht – with average at 2 to 3 cpht. 75% of the diamonds recovered are gem variety and the largest one weighed 6 ct. Though this diamond occurrence is rather localised, it assumes significance, in that, many of the world famous diamonds were reportedly recovered from gravels of the area. Another localized occurrence of old mining activity confining to the Mesozoic /Tertiary (?) sandstone is around Mallavelli to the east of Vijaywada and south-eastern side of the Eastern Ghat Mobile Belt. The basal conglomerate in the Banganapalle Quartzite Formation in the Kurnool Group is the main diamond-bearing stratigraphic unit so far known in the Cuddapah basin (Table 6). The conglomerate occurs as disconnected outcrops in a curved belt 250 km long in the western part of the Cuddapah Basin and about 120 km long in the Palnad Basin.The conglomerate range in thickness from 1 to 50 cm with an average of 10 cm, with clasts of chert and jasper and subordinate vein quartz embedded in sand-silt matrix.The diamond-bearing conglomerates are subarkose and classified as chert pebble-, oligomictic-, para-, conglomerates. The source of the conglomerates is traced to the west comprising lower Cuddapah sequences, igneous intrusives and the basement. Investigation for diamond bearing conglomerates has been revived recently from Banganapalle, Vajragiri-Munimadugu, Tammarajupalle and Ramallakota-Viryapalle-Yerubayi. Alluvial diamonds are known to occur in southern India along Krishna, Tungabadra and Penner Rivers. Old workings in Krishna Valleys occur in T2/T3 terraces at Panchalingala, Kurnool district near the confluence of Tungabhadra with Krishna River to Paritala down stream in Krishna

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district , over a distance of > 400 kms.The Pleistocene-Holocene gravels of Krishna and PennerRivers have been worked for diamond from different terraces (T2/T3 and T3) with probable primary source from WKF and other unknown sources.The gravels mainly of Krishna river along with those of the Pennar river, Sagileru, Kundair, Hundri and Ramileru yielded large quantities of diamonds. Diamond occurrences in the Godavari gravels are sporadic. The CIDP confined to the Aravalli Craton in the states of Madhya Pradesh, Rajasthan and Uttar Pradesh also consists of primary and secondary source rocks. The NE-SW trending Panna Diamond belt with established ancient mining activity is located within this province.This is the only belt where active mining for diamond is presently carried out in the country. The National Mineral Development Corporation Ltd is exploiting Majhgawan kimberlite/lamproite, the only diamond producing mine, with an average annual production of 16,000 carats. The lamproite pipe at Hinota has low diamond incidence and is not worked. NMDC also took up mining of a large gravel block at Ramkheria but abandoned the work due to operational difficulties. The extension of Hatupur conglomerate block has been explored by MECL. The occurrence of diamonds over such a long belt viewed in the light of only two known diamond bearing pipes at one end of the belt strongly point to contribution of diamonds from more pipes.

A little amount of diamond is being recovered from placer occurrences. The kimberlites/ lamproites (~1100Ma) intruding into the Kaimur Group of rocks are found along the western margin of the Vindhyan basin adjoining the Bundelkhand granite and are included in Majhgawan Kimberlite/Lamproite Field. Kimberlitic rocks discovered in this province are only a few and sporadic and are reported from the Bundelkhand granite terrain. The main source of diamonds in the country is from Majhgawan with about 10 carats per 100 tonnes within the pipes, which have been producing about 15000 carats per year of which a third are of the gem quality. The estimated reserve of diamond in this pipe is of the order of 1.3 million carats. The Hinota and Jungel have low incidence of 0.7 and 0.6 carat per 100 tonnes, respectively. The Vindhyan Supergroup of rocks host a major share of diamonds produced from the Panna Diamond Belt in the form of three diamondiferous conglomerate horizons associated with the Itwa sandstone, Jhiri shale, and Gahadra sandstone Formations of the Rewa Group of rocks of late Proterozoic age. The conglomerates at Shahidan mine at the base of the Jhiri shale have been worked for a long time and have a higher potential of 26 carats per 100 tonnes. Diamondiferous alluvial gravels are found mostly along the banks of the Ken-Ranj-Baghain rivers and lateritic gravels over the Baghain and Gahadra Sandstone Formations.The incidence of

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diamonds in Panna diamond belt from gravels of Baghain River (near Ramkheria village) and other streams are good at 23 carats per 100 tonnes. Diamond is also reported from the river gravels and alluvial caps at Chanda, Mahantola Salaia and Urdana. The EIDP confined to the Bastar and Singhbhum Cratons in the states of Maharashtra, Chhattishgarh, Orissa, Jharkhand and Madhya Pradesh is known for ancient diamond mining activity at a few places only viz., Wairagarh area in Maharashtra, and Hirakud area in Orissa and KoelSankh river areas inJharkhand. Kimberlite discoveries in the province are very recent and investigations carried out in different parts of the Bastar Craton led to identification of two new kimberlite fields (1) Mainpur kimberlite Field (MKF) and (2) Tokapal Kimberlite Field (TKF), both in the state of Chhattisgarh. The kimberlites of the MKF intruded into the Khariar group of rocks and those of TKF into the Indravati group of rocks of late Proterozoic age. Some of the kimberlites in the MKF are known to be diamondiferous.Diamond-bearing pipes in the former field have been identified from Payalikhand, Bahradih and Kodomali of Raipur district by GSI, DGM and private enterpreneurs. The recent discovery of kimberlitic / lamproitic rocks in Nuapada district of Orissa has opened a new area of primary source rocks for diamond. A few lamproite dykes have been discovered recently in adjoining Bargarh district, Orissa. A few of the Cretaceous lamproites intruding into the Gondwana sediments of the Damodar valley Coalfields and South Rewa Gondwana basin show similarities to that of lamproitic rocks. Diamonds are also reported in the gravels of Maini, Ib, and Mand rivers in Chhattishgarh and Tel-Mahanadi rivers in Orissa. The ancient workings in Wairagarh area appear to be in the conglomerates as well as gravels. The conglomerates and grit are associated with either the middle Proterozoic Sakoli group or the early Proterozoic Dongargarh Group of rocks. Meaningful prospecting and exploration for diamond and kimberlites depend much on the right type of prognostication. Prognostication for mineral search is essential at different stages of prospecting from regional operations over large areas to detailed operations over narrowed down target areas. As a result of GSI's work several prospective blocks have been identified for further investigation. Such blocks are listed below and short description on their status is enclosed.

A. LAMPROITE/ KIMBERLITES A.1 MAJHGAWAN KIMBERLITE/LAMPROITE DIATREME

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Geographic data: Location: Majhgawan, Panna district,(24039': 80002'); Toposheet no. 63O/2 Extent: 515 x 330 m diatreme. Access: Majhgawan pipe is located about 20 km south-west of Panna, the district Headquarters. Since Majhgawan pipe is a diamond producing mine, it is connected to Panna by an all weather road. Topography: The pipe intrudes into the Baghain sandstone, which forms a flat geomorphic surface with a height of 360m to 400m above MSL. At present, the mine is approximately 80m deep with a number of benches. Geological setup: The Majhgawan kimberlite diatreme identified as lamproite is a downward tapering, cone shaped body measuring about 515 x 330 m in plan. The contact with the host rock dips at fairly constant angle of 7000inwards. The contact between the kimberlite diatreme and the Baghain sandstone is normally sharp. In the western and southern periphery, however, the kimberlite is highly sheared and traversed by a network of calcite veins. The diatreme contains both cognate and accidental xenoliths. The yellow and blue grounds are well developed with a capping of 5 to 6m of soil. The contact between the yellow and the blue ground is at an average depth of 14 m from the surface.

Exploration: The

exploration programme was aimed at: (1) establishing offshoots of the kimberlite diatreme, (2)

deciphering the geometry of the body and study of different petrographic varieties at depth and (3) establishing incidence of diamond in the 'extended arm' of kimberlite on the basis of surface sampling with the help of deep pits.

A total of 2943.70 metres of drilling in 25 boreholes was done to study the pipe. During shallow drilling, two prominent offshoots were delineated upto a depth of 40 m and an additional reserve of kimberlite (0.14 Mt) has been established upto a depth of 40 m. To study the behaviour of the Majhgawan kimberlite at depth, 5 boreholes were drilled from outside the pipe area. The drilling has established the extension of pipe to a vertical depth of 330 m. The wall of the pipe indicates an inward dip of about 700 to 800. As against the diameter of the pipe, which is about 330 m on surface, it reduces to about 125m at a depth of 330m. The pipe continues to further depth. Treatment of about 1643.71t of kimberlite from offshoot yielded 14 diamonds weighing 7.20 ct indicating an incidence of 0.43 cpht as against 10 cpht in the main pipe. A.2 HINOTA KIMBERLITE DIATREME

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Geographic data Location: NNW of Hinota Village, Panna district, (24040': 80001'); Toposheet no. 63D/2 Extent: 200 x 180 m diatreme. Access: Hinota kimberlite diatreme is located about 20 km WSW of Panna. Topography: The pipe is emplaced into the Baghain sandstone which forms a flat geomorphic surface with a height of 360m to 400m. The pipe forms a topographic depression. Geological setup: The Hinota diatreme is emplaced into the Baghain Sandstone Formation of the Kaimur Group (Vindhyan Supergoup). On surface, the diameter of the pipe is 200 x 180 m with a slight NW-SE elongation. On the aerial photographs, the pipe is recognised by its high density of vegetation and negative topography. It is well recognised on satellite imageries also. The pipe was discovered as a result of magnetic and electrical resistivity surveys by GSI. The drilling in the Hinota pipe indicated top 2.5m of detrital material, followed by about 25 m of earthy yellow and greenish clayey matter and then blue ground upto a depth of 60 to 75m ending up in hard kimberlite.

Exploration: Atotal of 631.65 m of drilling was done in 3 boreholes, which indicated that the body extends beyond 160m in depth.Shaft Sinking: One 18.50m deep shaft was sunk in the pipe.A total of 228.40 tonnes of material from the shaft was treated and only two diamonds weighing 1.71 ct were recovered, which shows a very low incidence of diamond

Recommendations: As diamond incidence is low, further investigation in this pipe is unwarranted. Caution: The Hinota pipe falls in the Panna National Park area and to obtain prospecting lease, and to carry out large scale operations or even preliminary surveys, a prior permission from the Ministry of Environment, Government of India, is necessary. B. CONGLOMERATES B.1 HATUPUR BLOCK Geographic data: Location: Hatupur, Panna district,(240048': 80025') ; Toposheet no. 63 D/5 Extent: Hatupur block is 3 km x 3 km in extent; Hatupur, Rakhel and Damulua villages are located within the block. Access: The block is located about 23 km ENE of Panna on Panna-Paharikhera Road.

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Topography: The block fringes at Gahadara sandstone scarps in the southeastern part of the block, with an elevation difference of about 70m .There is a small hill in the eastern part of the block with a height of 440m. Geological setup: The Jhiri shales are exposed on the surface in the entire block. At the base of the Jhiri shale, a diamondiferous conglomerate horizon (Jhiri conglomerate), varying in thickness from 4 cm to 54 cm, exists. The Jhiri shale is underlain by Itwa Sandstone Formation. Towards the top of the Itwa Sandstone Formation, another diamondiferous conglomerate horizon (known as Itwa conglomerate) exists. The Jhiri and Itwa conglomerates are separated by 2 to 3 m thick sandstone horizon. The Itwa Sandstone Formation and Jhiri Shale Formation (with conglomerate) show very gentle dip towards SSE. The gradient is 1.5 to 2 m per 100 m. Exploration : The area has been mapped on 1:12,500 scale to demarcate conglomerate horizons, diamondiferous lateritic and alluvial gravels and detailed mapping of about 5 sq.km on 1:2000 scale. Drilling:In the western block the grid was laid at 200m intersection and in the eastern block at 250 m intersection. A total of 3345.95 m of drilling was done in 108 boreholes. The drill hole data revealed that the thickness of the Jhiri conglomerate ranges from about 1 cm to 70 cm. The depth of conglomerate varies from 4.55m to 36.35m.The Itwa conglomerate is separated from the Jhiri conglomerate by a non-diamondiferrous shale /sandstone horizon, the thickness of which varies from 2 to 4 m. The thicker conglomerate horizons also carry sandstone interbeds. The thickness of Itwa conglomerate varies from 1 cm to 2.42m and depth from surface varies from 3.42 m to 62.28m. Core loss has also been recorded in a few drill holes. In view of this, much thicker horizon of conglomerate is expected in the pits than in boreholes. Isopach map for the Jhiri and the Itwa conglomerates indicates irregular distribution of conglomerate. Both the conglomerates are thicker along palaeochannels than adjoining parts. The palaeochannels are oriented along NE-SW and E-W directions. Isolated patches of thick conglomerate are also recorded. The stratum contour plan of the base of the Itwa conglomerate horizon shows uniform and conspicuous south-easterly gradient. 36 shafts (2.5 x 2.5m), ranging in depth from 5m to 34.75m, were sunk on a grid varying from 100 to 250m to excavate the conglomerates. At the bottom of the shaft, where the Itwa conglomerate was encountered, two east-west oriented drives (1.8m height, 2.1m width and 6m length on each side) were driven to win the requisite quantity of conglomerate. The average thickness of conglomerate in shafts worked out to be 60 cm, varying from 17cm to 1.40m. A total of 4746.92 t of conglomerate was obtained from 6494.50 cu m. of excavation, which was treated at NMDC plant, Majhgawan.

Dimensions of explored prospects: i) Sub-block A: The sub-block (area 0.3 sq.km) was proved to contain conglomerate reserves of

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about 0.45 Mt with a diamond incidence of 27.91 cpht. This block is open at both ends, indicating the possibility of its further extension towards east and towards south-west. MECL has drilled in the eastern extensions of the block, the results of which are yet to be received. ii) Sub-block B: These sub-block measures 750 x 500m. Proved reserves of pure and diluted conglomerate estimated are 0.53 Mt and 1.49 Mt, respectively. Treatment results of the samples drawn are not available so far. The depth of the Itwa conglomerate varies from 20.95m to 29.10m iii) Sub-block C: The block is along a NW-SE trending channel. Thickness of the Itwa conglomerate ranges from 1.14 to 1.80m and depth varies from 6.45 to 21.65m. On the basis of the data of three pits (P-28, P-35 and P-36) and drives, about 0.31 Mt of undiluted and 0.74 Mt of diluted conglomerate of proved category have been estimated. Probable reserves of 0.60 Mt of undiluted conglomerate and 2.72 Mt diluted conglomerate have been estimated on the basis of drill hole data. The treatment results are not yet available. iv) Sub-block D: It is a small block located in the northeastern corner of the Hatupur block. The thickness of the Itwa conglomerate varies between 22 and 30 cm and depth varies from 8 to 8.5 m. Probable reserves of the conglomerate have been estimated at 0.106 Mt. for the undiluted and 0.742 Mt for the diluted categories. v) Sub block E: It is 1 km long, trending N-S and defined by drill holes. The thickness of Itwa conglomerate varies from 10 to 77cm and depth from 12.70 to 25.15m. No pits have been sunk in this sub block. On the basis of the drill hole data, probable reserves of the conglomerates have been estimated at 0.378 Mt of undiluted and 1.49 Mt of diluted conglomerate. vi) Sub-block F: It has a dimension of 500 x 500m and is a south-easterly extension of the subblock C. The depth of the Itwa conglomerate varies from 23.40 to 26.05m and thickness from 29 cm to 1.70m. On the basis of the drill hole and pit data, proved and probable reserves ofdiluted conglomerate have been estimated at 0.247 Mt and 0.495 Mt respectively.

Diamonds: The percentage of gem quality of diamonds is very high (55%). Off-colour and industrial diamonds constitute 19% and 26% of the total diamonds. The largest sizes of diamonds recovered so far, during the exploratory operations, are 3.38 ct (industrial variety), 2.27 ct (gem quality) and 1.68 ct (off colour). Average size of gem, off-colour and industrial varieties is 0.6 ct, 0.45 ct and 0.63 ct, respectively.

B.2 SHAHIDAN BLOCK Geographic data: Location: 2.5 Km NE of Panna, Panna district. Coordinates: 24044': 80012'; Toposheet no. 63 D/2;Extent : 2700 X 700 m Topography: Gently rolling terrain. Geological setup: Jhiri conglomerate occurs at the base and as interbeds within the JhiriShale and siltstone of the upper part of the Rewa Group. It forms escarpment to the SW and NE of Panna. The

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conglomerate is coarse, pebbly or granular, with subrounded granules of jasper, chert, sandstone and shale. It is rather well sorted with a sandy matrix. Exploration: Shahidan area has the record of best and larger size diamond recovery. Data computed from the operations of one of the large and systematically managed mines in Shahidan area indicated diamond incidence of 43 cpht. During 1972-74, GSI drilled 20 boreholes which indicated that the cumulative thickness of conglomerate to the SSE of Janakpur is above 30 cm. During 1980-85, mapping (on 1:5000 scale) and drilling (62 boreholes by MECL) was done. Drilling showed an average thickness of 20 cm of conglomerate. 10 pits sunk at drill hole sites indicated, on an average, 1.7 times greater thickness of conglomerate.The northern part of the area has a number of old workings which are upto 15m deep and waterlogged, causing seepage problem. A part of the northern section is in reserve forest, while the southern part is under cultivation. B.3 GANJA - SHAHPUR BLOCK Geographic data: Location: Near Ganja - Shahpur village, Panna district. Toposheet: 63 D/5 Topography: Gently rolling terrain. Geological Set up Both Itwa and Jhiri conglomerates are encountered in the area. The Jhiri conglomerate is both matrix as also clast supported. The matrix supported conglomerate has 15% to 40% of clasts set in an argillaceous groundmass. The clasts are generally of granule size. These include white quartzite, vein quartz, grey quartzite, green shale, cream quartzite, jasper, pink quartzite and chert. Exploration: 16 holes drilled in the area encountered Jhiri conglomerate at a depth of 12.15m in the northwest and at 49.30m in the southeast, down the dip. This is in conformity with the regional dip of the formation.The Itwa conglomerate is intersected at a depth of 13.48m in the northwest and 50.50m in the southeast. Thickness of Itwa conglomerate varies from 6 to 70 cm.Drill hole data also indicated that there is a rapid variation in the number of bands of Jhiri conglomerate from 1 to 6. The Itwa conglomerate has generally one or two bands, except for southwestern side where 5 bands are recorded. . Reserve: On the basis of drill-hole data, indicated reserves of the Jhiri conglomerate is about 6.74 Mt and that of the Itwa conglomerate is about 4.44 Mt C. RIVER GRAVELS Geographic data: Location: Itwa, Brijpur, Ramkheria villages, Panna district.

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Coordinates: 24047'- 24049': 80023'- 80030'; Toposheet no. 63 D/5 Extent: Gravel zone extends from Ramkheria (24049': 80027') in the east to Itwa (24047’: 800 23') in the west. Access: The area lies about 20 Km ENE of Panna and an all weather road between Panna and Paharikeria runs through the entire length of gravel zone. Topography: The area is practically flat, with the Baghain River incising into the flood plain deposits. Exploration : Systematic mapping (1:50,000) of alluvial zone was done as part of regional mapping.The area around and along the Baghain river was mapped on 1 : 12,500 scale as a part of delineation of diamondiferous gravel zones.Geophysical survey of the gravel along the entire river section in ItwaRamkheria section was done and the depth of bed rock was demarcated by taking cross traverses. Dimension of the prospect: The area covers a length of approximately 15 km and width of 1 to 2 km.Diamondiferous gravel is restricted to the basal part of the alluvial pile and its thickness varies from 30 cm to 4 m. It comprises boulders and pebbles of sandstone, shale and laterite, set in sandy matrix. Diamond Incidence: Bulk sampling by the GSI in 1956 in diamondiferous alluvial gravel of Ramkheria indicated an incidence of 26 cpht. The exploration by NMDC proved a resource of about 1,15,000 ct with incidence of about 16 cpht. Recommendations : Ramkheria gravel deposits indicate higher diamond incidence with higher percentage of gem quality diamonds than the Majhgawan kimberlite. This prospect appears to be quite promising provided prior exploration is done in the gravel. A few areas were delineated on the basis of photogeological studies for detailed exploration along the Baghain River. D. BUNDELKHAND BASEMENT Several ultrabasic bodies are found in the Bundelkhand granite massif,emplaced after or along with the granitic rocks. Preliminary exploration revealed diamonds, small in size. However, in view of their possible regional relevance in the emplacement of diamond bearing pipe rocks, short descriptions are given below. D.1 ANGOR AND BANDHA ULTRABASIC BODIES Geographic Data: Location : 0.5 km north of Angor Village (24044':79025'; Toposheet no.54 P/6), on the SagarChhatarpur state Highway and 130 km SW of Panna,Chhattarpur district

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.Prospect : Angor Ultramafic prospect Topography The granitic country is flat Geological setup The ultramafic rocks are found in Bundelkhand granites exposed mainly on the eastern side of the road but much of it has been levelled off to form cultivated land.

Exploration : : Geophysical surveys indicated a 450 m long and 200m wide body, trending in NNW-SSE direction and another 170m long and 30m wide body located 0.5 km NW of the first body. Drilling indicates top 7 -12m weathered zones, underlain by brecciated carbonated pyroxenite, underlain by harzburgite.7 boreholes totalling 792.35m were drilled in the main body, which continues beyond 289m depth.Six large pits reaching to a depth of 10m were put and two diamonds totalling 0.2 carats were recorded after treating 937.40 tonnes of excavated material. In course of another excavation, 311.80 tonnes of treated material yielded five diamonds weighing 3.52 carats. NMDC treated 1000 tonnes without any recovery of diamond.A similar body occurs near Bandha (240 39′:790 19'; 54 P/6) to the southwest of Gulganj. It is a dyke-like body, about 10m wide and covered by soil at both ends. 86 tonnes of material treated yielded two diamonds weighing 1.62 ct (one gem 0.57ct and one industrial 1.05 ct). . Recommendations In view of the diamond incidence, both the bodies could be subjected to further investigation. D.2 DONGRAHA ULTRABASIC ROCK Geographic data: Location : East of Dongraha (24051': 80008'), Panna district. Extent: 10m long and 50cm to 1m wide; trends N 30 E - S 30 W. Geological setup: The rock is intensely weathered, black in colour and porphyritic with phenocrysts of altered olivine. Groundmass contains calcite and dusty opaques like ilmenite, magnetite and possibly perovskite. Exploration: No exploration was carried out. D.3 ULTRABASIC ROCKS OF HARSA Geographic data: Location: 1.5 km north of Harsa village (24046':80006'), Panna district; Toposheet: 63 D/1 Extent: The outcrop measures 1 m long and 50 cm wide.

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Geological set up: The outcrop shows sharp contact with prophyritic pink granite; the other side is covered by residual soil, rich in carbonate kankars. The rock has been identified as lamprophyre. Exploration: No exploration for recovery of diamond was carried out. D 4 ULTRABASIC DYKE NEAR BARIARPUR BARRAGE Geographic data: Location: East bank of Ken River, north of Barrage, Panna district Coordinates: 24051': 80006'. Toposheet no.:63 D/1. Geological set up: A dyke-like body, 5m to 10m wide trending N 50 E -S 50W, is well exposed more than 1 km long in the west bank canal of the barrage, varying in thickness from 5 to 10m and, ends covered under soil.The rock is grey, green to greenish brown, showing olivine, reddish mica and opaques. The body cuts through Bundelkhand granite and shows contact metasomatism. The rock is traversed by serpentine, carbonate and quartz veins. It continues under soil cover for 600m, as proved by drilling three holes, spaced 200m apart; further extension possible. Two pits were sunk in the eastern bank of the Ken River and treatment of 138 tonnes of material from one of the pits yielded one diamond (off-colour) weighing 0.44 ct. Recommendation: In view of large strike extension and diamond incidence, the body should be further investigated. D.5 BASALTIC KIMBERLITE OF BIHARPUR AREA Geographic data: Location: 0.7 km WNW of Biharpur, Panna district. Coordinates: 24057’: 80031' - Toposheet no. 63 D/9 Extent: 600m long and 1 to 5m wide. Exploration: Two boreholes, aggregating 298.43m, were drilled. No kimberlite was intersected in any of the holes and it appears that this dyke pinches off at very shallow depth. About 33 cu m excavation was done, and 55 tonnes of material treated but no diamonds were recovered. PROSPECTS IN CHHATTISGARH The Chhattisgarh State forms a part of Bastar Craton extending on west to Maharashtra and on east to Orissa. It is of great significance that the Raigarh Mobile Belt, located between the Bastar Craton on south-west and the Singhbhum Craton on north-east, is manifested by the presence of diamond in all the streams of Ib, Maini, Mand and Sankh and their tributaries. The Archon of Bastar Craton is bordered by Protons of Raigarh Mobile Belt and Eastern Ghat Mobile Belt and this tectonic scenario is important in regional prognostication for diamond and kimberlite in Bastar Craton. In Bastar

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Craton there has been no major thermal activity after 2000 Ma. Hence, the Proterozoic platformal belts over the cratonic area have been selected as first priority blocks for investigation of kimberlite.The eastern and central parts of the craton are priority areas because they represent the low heat flow and high permeability zones. The area is marked by presence of platform cover sediments which protects the kimberlite diatremes from erosion. The prominent Proterozoic basins are Chhattisgarh basin, Pairi-Khariar basin, Ampani basin, Indravati basin, Sabri basin and Albaka basin.Considering all the positive features, the following target areas have been prognosticated in search for kimberlites. a) The Pairi-Khariar basin and surrounding granitic terrain, b) the Indravati basin and adjoining gneissic complex on west and south, c) the Sabari basin and adjoining gneissic complex, d) Saraipalli area comprising rocks of Chhattisgarh basin and the adjoining granitic terrain, e) the Albaka and Abujhmar basins, f) the southern part of Chhattisgarh basin and adjoining granitic terrain, g) the Raigarh Proterozoic crystallines bordering the Bastar Craton. A total of 14 priority target blocks have been demarcated of which 11 are in Chhattisgarh and three in Madhya Pradesh. The area of each block has been tentatively kept at 5000 Sq. Km. In the Chhattisgarh State, so far, two Kimberlite fields have been identified which are Mainpur Kimberlite Field in Raipur district and Tokapal Kimberlite Field in Bastar district. A. MAINPUR KIMBERLITE FIELD (RAIPUR DISTRICT) The Mainpur Kimberlite Field (MKF) is one of the three established diamond bearing kimberlite fields in Peninsular India, the other two being Panna in northern Madhya Pradesh and Wajrakarur (including Chigicherla and Kalyandurg kimberlites) in Andhra Pradesh. MKF is located in the south-eastern part of the Raipur district of the state of Chhattisgarh in Central India, 135km SE of Raipur city. Exploration activities by the GSI and the State Government have led to the identification of five kimberlite pipes (including three diamondiferous pipes) and more than 40 kimberlitic indicator anomaly zones in the MKF, which are likely to be associated with kimberlitic bodies. Kimberlitic rocks: their occurrence and distribution Five kimberlitic diatremes have been located in a linear span of 12.5 km in the Mainpur Kimberlite Field. The kimberlitic diatremes are Payalikhand-I (92010'10": 82021'00") (100m x 100m), Payalikhand-II (50m x 50m), Jangra( (>50m across), Kodomali (300m across) and Bahradih (300m x 200m).Most of the diatremes are circular in plan while Bahradih diatreme is elliptical. Amongst

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the diatremes only Kodomali exhibits fresh rock exposures while others have been weathered to green earth at the surface. A. 1. PAYALIKHAND DIATREMES Geographical data: Location: Payalikhand (20010'10: 82021'00", Toposheet No: 64 L/8), Raipur district; 169 km from Raipur Topography: 460m above MSL Geological set up: The Payalikhand area comprises a complex lithological assemblage represented by metavolcanics and metasedimentary sequences of Sonakhan Group, rocks of Baya Gneiss Complex, khondalite and charnockite suite of rocks of the Eastern Ghat Mobile Belt, intrusive Bundeli granitoid and the sedimentary cover sequences of Pairi and Ampani Groups and Chhattisgarh Super Group. Exploration: Two diatremes have been located along the slope of a foothill of the Khariar plateau. Characteristics of the diatremes: Number and name of kimberlite body: Payalikhand-I, MKF Field Dimension Trend: 100m x100m Emplacement control: Circular within granitoid rocks (64L/8) Outcrop characteristics: Expressed as a break in slope, highly altered kimberlitic rock (green earth) diatreme facies Diamond contents/Heavy minerals: Diamondiferous and garnet, spinel, clinopyroxene Number and name of kimberlite body: Payalikhand-II. MKF Field Dimension Trend: 50m x50m Emplacement control: Circular within granitoid rocks 64L/8 Outcrop characteristics: Along break in slope, highly altered kimberlitic rock as green earth. Diamond contents/Heavy minerals: Diamondiferous` A. 2. BAHRADIH DIATREME Geographical data Location: Bahradih (20012'30":82012' 00", ToposheetNo: 64L/4), Raipur district; 12 Km northwest of Payalikhand Topography: Approx 300m above M.S.L

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Geological Set up: The geological set up is same as that of Payalikhand Block. The kimberlite pipe located at Baharadih is elliptical in shape.Presence of xenoliths of consolidated shale and sandstone within the weathered kimberlite indicate post Khariar age of diatremes. Since the kimberlite pipe does not crop out above the Khariar cover sediments, it is therefore, presumed that it has only intruded part of the sequence. Exploration: The Bahradih diatreme is located in an ampitheatre like depression surrounded by resistant granitoid rocks. Bahradih diatreme surfaces at an altitude of 560m from MSL. Characteristics of the diatreme: Name of kimberlite body: Bahradih Dimension Trend: 300m x 200m; Emplacement control: Sub circular within granitoid rocks (64L/4) Outcrop characteristics: Ampitheatrical depression, highly altered kimberlitic rock (green earth), diatreme facies Diamond contents/Heavy minerals: Diamondiferous and garnet, spinel, clinopyroxene, orthopyroxene, phlogopite A. 3. JANGRA DIATREME Jangra diatreme surfaces at an altitude of 500m from MSL. Characteristics of the diatreme Name of kimberlite body: Jangra (200 08′30″: 820 19’ 40”). Dimension Trend: 50m x 50m Emplacement control: Circular within granitoid rocks 64L/8 Outcrop characteristics: Ampitheatrical depression within granitoid Diamond contents/heavy minerals: Not known/garnet and spinel A. 4. KODOMALI DIATREME Kodomali (20011' 10": 820 14' 08") kimberlite exposes as a dyke with WNW-ESE trend and is the only diatreme with rock exposure visible at the surface, amongst the five known diatremes in Mainpur Kimberlite Field. Like other diatremes, this diatreme is also surrounded by the granitoids. The near surface alteration as green earth is not much as compared to other diatremes. Characteristics of the diatreme Dimension Trend: 300m x 300m Diamond contents/Heavy minerals: Diamondiferous and garnet, spinel, clinopyroxene, ilmenite and olivine

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Kimberlites of Mainpur kimberlite field have been classified into three volcanic facies, viz. crater, diatreme and hypabyssal. Crater facies material has been preserved as xenoliths within Payalikhand-I and -II diatremes. Bahradih, Payalikhand I and II and Jangra diatremes have been classified as diatreme facies rocks. Only Kodomali rocks are classified as hypabassal facies Recommendation: The MKF has scope for further work to establish more kimberlite pipes and evaluation of their diamond potentiality. B. TOKAPAL KIMBERLITE FIELD (BASTAR DISTRICT) The regional search for kimberlites in Indravati basin has located kimberlite clan rocks in Tokapal, Duganpal, Bhejripadar and Parpa-Parakot areas and the Tokapal Kimberlite Field. The area is occupied by the Archaean-Proterozoic rocks of Bastar Craton. The kimberlitic pipes have intruded along NW-SE trending fracturers exhibited by mafic dyke swarms. The NW-SE trending dyke swarms as well as major lineaments and faults possibly indicate reactivated mantle permeable zones along which the kimberlitic pipes have been emplaced within the Proterozoic cover sediments.The Indravati basinal area forms the east – central part of Bastar Craton.The Tokapal, Duganpal and Parpa-Parakot kimberlitic rocks probably indicate multiple intrusions from a single or multiple feeders covering an area with 5km length and 1 km width. The borehole core samples indicate multiple intrusions at different levels with deposition of tuffs in the upper part. The Bastar kimberlites are in the crater facies, without much erosion. It is also interesting to note that in Bastar, there are kimberlitic flows in phases overlain and underlain by Indravati sediments. B.1. TOKAPAL KCR (KIMBERLITE CLAN ROCK) BODY The Tokapal rock is exposed in pit section and the rock is greenish in colour and shows typical kimberlitic clast-matrix texture and flowage structure within sediments (Jagdalpur Formation) in the form of flows (65E/16).The rock shows crude banding and top portion is lateritised and covered by black soil horizon. Diamond content: Not known B. 2. DUGANPAL KCR BODY The Duganpal kimberlitic rock exposed in the Duganpal nala section has been exposed by drilling. Diamond :content : Not known B. 3. BHEJRIPADAR KCR BODY The Bhejripadar kimberlitic body is located near village Bhejripadar (65 E/16). The body

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is exposed within the sandstone unit of Tirathgarh Formation. Diamond content: Not known B. 4. . PARPA – PARAKOT KCR BODY The kimberlitic rock in Parpa – Parakot sector was observed from the borewell cores drilled by the State Agricultural Department. The crater facies rocks are concealed under the soil and laterite cover of >20m. The borehole data show the presence of kimberlitic tuffs and pyroclastic rocks below 19.87m from the surface upto 36.67 m. From 36.67m to 62.69m greenish black massive kimberlite was observed. Diamond content: Not known C.EXPLORATION FOR KCR IN RAIGARH MOBILE BELT The exploration for KCR was also conducted in the Tapti Lineament Zone (TLZ) in parts of Raigarh and Surguja districts of Raigarh Mobile Belt from 1994 to 2000 on the basis of reported diamond incidences in the river gravels of Ib, Maini, Mand, Utial and Talda drainages.A total of 6000 sq km area was covered by PGRS studies and stream sediment sampling, but no primary source of diamond has been located except one grain of chromite falling in the edge of kimberlite field. D. SARANGARH SECTOR The Sarangarh area falls in the north eastern part of Chhattisgarh basin. A major part of the area forms a part of Bardwar sub basin of Chhattisgarh supergroup. Stream sediment sampling in the area revealed presence of kimberlitic pyrope garnet which are found to be G-9 type of lherzolitic derivative. In addition G-5 garnet has also been discovered from stream sediment samples. Detailed sampling in this area is recommended. PROSPECTS IN MAHARASTRA Indicator mineral survey carried out in the western part of Bastar craton, falling in Chandrapur and Garchiroli districts of Maharastra has revealed chrome diopside and G5 garnet.The chrome pyroxenes show some similarity with the pyroxenes from the Monastry kimberlite field, South Africa, in terms of their Ca/ (Ca + Mg) and Mg/(Mg + Fe) ratio with chromium. PALEOPLACER DIAMONDS OF WAIRAGARH, MAHARASHTRA: Diamond incidence is known from conglomerates of Wairagarh area in Maharashtra. The Wairagarh area exposes a narrow stretch of (10km x 6km), NNW-SSE trending low

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grade, highly deformed meta sedimentary belt within Archaean Amgaon Gneiss and forms a part of the western part of Bastar Craton. An octahedral diamond (3.5mm long and 2.5mm wide, 0.15 carat) was recently recovered during the GSI investigations of the conglomerate unit of WMS. Along with diamond other heavy assemblages identified include ilmenite, garnet (G-5 garnet, almandine, grossular and andraditic garnets), pyroxenes, amphibole, staurolite, chrome spinel and rare tourmaline. This find has opened up new vistas of diamond search in similar geological milieu in the western Bastar Craton.

PROSPECTS IN ORISSA With Multisensor Twin otter aero-geophysical survey carried out by the Airborne Mineral Survey and Exploration Wing (AMSE Wing) of Geological Survey of India during 1994-98 along E-W flight lines at intervals of 500m with a mean terrain clearance of 80m covering an area of about 27,850 sq. km. from Mainpur Payalikhand area in the south to Raigarh-Sundergarh area in the north around Chhattishgarh- Orissa border in search of kimberlite,. NE-SW trending olivine lamproite dyke cross cutting a NW-SE trending dolerite dyke has been discovered near Sakri village, Bargarh district, Orissa. Discovery of this lamproite has raised hopes of finding more such dykes and main lamproite bodies along the ideal setting of the contact of Bastar Craton and Eastern Ghat Mobile Belt. It may be mentioned here that this present setting is similar to the Krishna lamproite field (KLF) on the eastern margin of Dharwar Craton just outside the NE horn of Cuddapah Basin in Andhra Pradesh. Discovery of a lamproite dyke on the margin of Bastar Craton and Eastern Ghat Mobile Belt and incidence of several kimberlite indicators in Mainpur-Gariaband and Khariar roadPaikamal area prove that the integrated strategy is well founded and worth continuing further to utilize the vast amount of aero-geophysical data available with GSI pertaining to this area. Recently State DGM has recovered diamond from a pipe in Kalmidadar. The Cratonic domain of western Orissa lying in tectonic juxtaposition with circum cratonic EGMB is a promising regional target of primary diamond exploration due to old diamond panning records and recent discovery of kimberlite diatremes in adjoining state of Chattisgarh having identical geological milieu. KIMBERLITES AND LAMPROITES OF SOUTH INDIA

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Kimberlites and lamproites are located in about 270 x 180 Km area in Wajrakarur-LattavaramChigicherla-Kalyandurg area (WKF) in Anantapur district, Andhra Pradesh (A.P.), Narayanpet Kimberlite Field (NKF) in Mahboobnagar district, A.P.and Gulbarga district of Karnataka and Chelima-Zangamrajupalle area (CZLF) in Prakasam district,A.P. and Jaggayyapeta Lamproite Field(JLF) also known as Krishna Lamproite Field of Krishna and Nalgonda districts of A.P. These kimberlites and lamproites are known to occur only from the Eastern Dharwar Cratonic block. The WKF (14005'/ – 15003: 77018' – 77023'; Toposheet nos 57E/8 & F/5) measures 120kmx60km with kimberlites emplaced into the gneisses and schist belt.A total of 21 kimberlites are distributed in 3 clusters, viz, (i) Wajrakarur – Lattavaram cluster – 13 bodies (pipe – 1 to pipe-13) (ii) Chigicherla cluster – 5 bodies (CC-1 to CC-5) (iii)Kalyandurg cluster – 3 bodies (Kl-1 to Kl-3) Majority of the pipes in WKF are diamondiferous. During 2004, two new kimberlite bodies have been reported from Timmasamudram(TK1 & TK-2). The (NKF) is located about 150 km southwest of Hyderabad and 200 km north of the WKF. It measures 60 x 40 km in extent. The Kimberlites of (NKF), occur in four noticeable clusters, viz., (i) Maddur cluster – 11 bodies (MK-1 to MK-11) (ii) Kotakonda cluster – 7 bodies (KK-1 to KK-7) (iii)Narayanpet cluster – 10 bodies (NK-1 to NK-10) (iv)Bhima cluster – 6 bodies (BK-1 to BK-6). Incidence of diamond has not yet been reported from these bodies. During 2001-02 inbetween NKF and WKF three new kimberlite bodies were discovered near Siddampalle village (SK-1,SK-2&SK-3) in Gadwal district,A.P. WAJRAKARUR KIMBERLITES

In Wajrakarur area, three kimberlite bodies (pipes 1, 2 & 6) are found over a length of 4 km in an E-W direction. The pipe 6 occurs in black soil area whereas the rest in the residual brown soil area. KIMBERLITE PIPE 1 (WAJRAKARUR PIPE)

The kimberlite reserves estimated for the southwestern part (400 x 150m) are about 6.94 Mt

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upto 60m depth with a diamond resource of 52,000 ct. Though the average incidence is less, large majority of diamonds in general are gem quality and diamonds upto 9.45 ct were recovered. KIMBERLITE PIPE-6 (WAJRAKARUR WEST PIPE)

Location: About 1.5 km west of Wajrararur and 300m north of Kottakunta tank. Dimension: 260 x 240m – roughly circular in shape Drilling: 19 boreholes. Deepest borehole upto 280m depth. The body is completely covered under 1.5m thick black soil. Yellow ground occurs upto a depth of 45m, followed by blue ground which extends beyond 280m depth. A granite– kimberlite breccia raft (170m long and 30-80m wide) is found in the centre of the pipe extending upto 35 to 40m depth. The kimberlite resources estimated upto 60m depth are of the order of 5.99 Mt with a diamond resource of 40,000 ct.

KIMBERLITE PIPE -2 (WAJRAKARUR EAST PIPE)

Location: About 2.5 km east of Wajrakarur; Dimension: 380 x 70m Drilling: 11 boreholes,Unaltered kimberlite at surface The pipe is diamondiferous. Three diamonds were recovered after processing 278 tonnes of kimberlitic material. Diamonds are of gem variety and range of weight is 0.04 to 3.26 ct. LATTAVARAM KIMBERLITES

Four kimberlites (pipes 3, 4,8 and 9) are located in a radius of 0.5 km., about 1 to 1.5km east of Lattavaram (14055': 77017'; 57F/5). Outcrops are scanty. The results of exploration are as follows: Pipe No. 3: Diamond incidence(cpht)- 0.28 Pipe No. 4: Diamond incidence(cpht)- 0.25 Pipe No. 8: Diamond incidence(cpht)- 0.33 Pipe No. 9: Diamond incidence(cpht)- 0.5 KIMBERLITE PIPE -5 (MULIGIRIPALLE PIPE)

Location: About 1.5 km east of Muligiripalle Dimension: 240 x 45m Sampling Five bulk sample pits ( 3 x 2 x 10m each). 276 cum of excavation, 482t of processing. No diamonds recovered. KIMBERLITE DYKE – 7 (VENKATAMPALLE KIMBERLITE)

Location: About 0.5 km east of Venkatampalle (14056:77021'; 57F/5) Dimension: 1.2 km long x 0.5 to 30m wide – dyke like body.

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Av.Diamond incidence (cpht): 44.5 Kimberlite resources :About 0.5 Mt upto 90m depth (for the 600m length of dyke enlargements). About 14000 t of overburden over the dyke enlargement. Diamond resources: 48000 ct upto 90m depth in the kimberlite and 4700 ct in the overburden over the dyke enlargements. Diamond characteristics A large majority of the diamonds recovered from the kimberlitres are gem quality. Till now, the pipes 1 and 6 and dyke 7 have yielded more number of diamonds. In the pipes 1& 6, about 90% of the diamonds by weight are gem quality and in the dyke7, about 60% by weight. The largest diamond recovered from the area is 16.30 ct by weight (from dyke-7) and is of gem variety. KIMBERLITE PIPE – 10 (ANUMPALLE KIMBERLITE)

Location: 0.75 km west of Anumpalle village (14059' 40": 77030'55") Dimension: 1200m long x 1000m wide pod shaped body. Emplaced into the younger granitoids at the intersection of the ENE –WSW fracture with the major NW-SE trending Singanamala fault. No outcrops, covered by 1.5m kimberlite calcretre, rafts of granite float in the kimberlite – two linear disconnected satellite bodies noticed to the west of the main body. Pipe no. –P 10 Diamond recovery No/Wt.Ct.- 48/14.71 KIMBERLITE PIPE –11 (DIBBSANIPALLE KIMBERLITE)

Location 0.5 km SSE of Dibbsanipalle village (15002'00 : 77028' 00") Diamond incidence (ct/100t): 0.78 Dimension: 143m long x 82m wide Bean shaped Pipe no. –P 11 Diamond recovery No/Wt.Ct.- 2/2.15 Diamond incidence (ct/100t): 0.78 KIMBERLITE PIPE – 12 (CHINTALAMPALLE KIMBERLITE)

Location: 1 km west of Chintalampalle village (15002' 00": 77028' 00") Dimension: 130m long x 40m wide Pipe no. –P 12 Diamond recovery No/Wt.Ct.- Nil Diamond incidence (ct/100t): Nil

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KIMBERLITE PIPE -13 (TUMMATAPALLE KIMBERLITE)

Location: 2.5km NE of Tummatapalle village (14049'55 : 77041' 00") Dimension: 125m long x 100m wide Emplaced into the TGA rocks along a ENE-WSW sinistral fault that displaces the Manutla dome.Melanocratic outcrops and partly weathered and altered kimberlite capped by calcretes. A.2. CHIGICHERLA AREA (WKF) Coordinates: 14031': 77041'; Toposheet no. 57F/10 KIMBERLITE PIPE CC-1:

Dimension: 315 x 185 m – pear shapedA grab sample of 119 t from a well dump in the body yielded 4 diamonds weighing 0.44 ct. Subsequently 436 tonnes of material has been processed which yielded 5 diamonds weighing 1.31 ct averaging 0.30 cpht. KIMBERLITE BODY CC-2

Dimension 200 x 175m A total of 302 tonnes of kimberlite material was processed which yielded two diamonds weighing 1.02 ct averaging 0.35 cpht KIMBERLITE BODY CC-4

Location: about 1.75km west of Golapalle Dimension: 125m x 100m, nearly circular in outline Incidence of diamond: 15 diamonds weighing 2.17 ct were recovered from 88 tonnes of kimberlite material drawn from 5 trenches, indicating an average diamond incidence of 2.46cpht. KIMBERLITE BODY CC-5

Location : This kimberlite body is located about 1km NE of Gollapalle. Dimension : 220m x 70m Incidence of diamond : 6 diamonds weighing 1.38 ct have been recovered from 175 tonnes material of pipe CC-5. All are gems ranging in weight from 0.05 to 0.51 ct, the average weight of the stones being 0.23 ct. A.8. CHELIMA-ZANGAMRA JUPALLE AREA (NALLAMALAI FOLD BELT) A number of kimberlites/lamproites exists and lie undetected in the soil covered areas south, west and north of the Cuddapah Basin and within the basin itself. The known source rocks tested so far are not of much economic significance and therefore intensive efforts are needed to identify additional primary host rocks for diamond.

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A.9 JAGGAYYAPETA (KRISHNA) LAMPROITE FIELD (JLF/KLF) The JLF or KLF falls north of the Krishna River, along the eastern margin of Dharwar Craton (DC) in Krishna and Nalgonda district spread over an area of about 160 sq. km. and comprises 25 lamproite bodies located just outside the peripheral parts of the north-eastern horn of Cuddapah basin. The lamproites occur as 0.5m – 5m dykes, mostly as clusters and run for lengths of about 1m to 400m in close association with dolerite dykes mostly emplaced along the contacts between granite gneiss and dolerite dykes. A.10. SIDDAMPALLE KIMBERLITES During 2001-02 three new kimberlite bodies were discovered near Siddampalle village in Gadwal district, Andhra Pradesh. The first body (SK-1) measuring 100x65m is located about 2km N25E of Siddampalle village and SK-2 measuring 110x50m is located about 1.5km N10W of Mallapuram Tanda. The third body (SK-3) measuring 26 x 14m is exposed in a well section. SK-1 & SK-3 are mainly ‘hardebank’ variety while SK-2 is a concealed body with calcrete cover. B. CONGLOMERATES B.1 BANGANAPALLE - NEREDUCHERLA AREA Banganapalle - Nereducherla, Kurnool district. Coordinates : 15012' -15020'; Long.: 77050'-78015';Toposheet no. 57 I/2 & E/16 Extent : 30 km long and 200 m to 2 km wide Exploration: To assess diamond potential of the conglomerates (mainly basal) exploration was carried out in 'two phases during 1980-87 by GSI in association with MECL and NMDC, in eight selected blocks in the area, six in the Munimadugu-Allahabad plateau areas and two in the Banganapalle-Rallakotturu-Lingambadi Plateau areas. MUNIMADUGU BLOCK:

No. of diamonds/weight : 167/84,38 ct Diamond incidence : 2.26 cpht Average diamond weight : 0.50 ct Conglomerate resource : 60, 700 t Diamond resource : 2,000 ct An average incidence of 8.32 cpht (spot values upto 35 cpht) was recorded. Average diamond weight from this area is 0.87 ct. ALLAHABAD WEST AND WEST EXTENSION BLOCKS:

No. of diamonds/weight : 221/71.24 ct

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Diamond incidence : 1.48 cpht Average diamond weight : 0.32 ct Conglomerate resource : 10,44,000 t Diamond resource : 15,600 ct Spot values for diamond are upto 7 cpht. ALLAHABAD SOUTHWEST AND SOUTHWEST EXTENSION BLOCKS:

No. of diamonds/weight : 298/125.90 ct Diamond incidence : 2.89 cpht Average diamond weight : 0.42 ct Conglomerate resource : 3,94,000 t Diamond resource : 11,400 ct An incidence of 8.23 cpht was recorded over a length of 200m (with spot values upto 27.35 cpht) RALLAKOTTURU - LlNGAMBADI BLOCK:

No of diamonds/weight : 104/51.67 ct Diamond incidence : 2.59 cpht Average diamond weight : 0.49 ct Conglomerate resource : 21,37,00 t Diamond resource : 26,600 ct Of the total diamonds recovered, gem quality constitutes about 76% while the off colour and industrials, 8% and 16% respectively. B.2 RAMALLAKOTA- YAMBAI AREA The erratic distribution and lensoid geometry of the conglomerate beds warrant close spaced pitting/shallow drilling to delineate the beds as well as estimate the conglomerate resources. B.3 UNDUTLA-TAMMARAJUPALLE -CEMENTNAGAR AREA Area : Undutla-Tammarajupalle-Cementnagar, Kumool district. Coordinates : 15030' –15025'.: 78010' – 78015' The conglomerates from both the Undutla and Cementnagar Plateau have to be tested for diamond potential. Search for kimberlite in Buthpur and Achampet block in Mahbubnagar district, Andhra Pradesh, yielded kimberlite specific minerals like picro-ilmenite and chrome-spinel in stream sediment samples from Palkampally, Wattipalli and Kottapalli. Kimberlite specific minerals like

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chrome spinel has also been recorded from Kalwakurthi and Charakunda block in Mahbubnagar and Nalgonda districts. GOLD India ranked 6th in the world with a Gold production of 19.5 tonnes during the year 1905, whereas the production of gold from primary source during the year 2007 is only 2.490 tonnes. Kolar mine has produced more than 800 tonnes of gold before its closure in 2001. Presently gold is produced from three mines viz Hutti, Uti, Hirabuddni (HGML) in Karnataka and as by product from basemetal sulphide deposits of Khetri (Rajasthan), Mosabani, Singhbhum(Jharkhand), in public sector and Kundrekocha in private sector in the decreasing order. In India, the total gold production in the year (2006-07) was 12.82 tonnes, ( 0.5% of world production), of which 2.36 tonnes is from primary source, 127 kg from basemetal mines as by product, and the remaining 10.34 tonnes recovered from secondary source by smelting of imported copper concentrates by HINDALCO at Dahej in Bharuch dist, Gujarat. Kolar, the second deepest (3200 m) gold mine in the world, survived for 110 years and the Hutti gold field witnessed four periods of widely separated exploration and mining Viz, Pre Asokan +2000 years old, Nizam period 1886-1920; 1937 to 1947; and the present and most successful from 1947 onwards. The deepest (about 250m in length and over 195m in depth) known old working in the

world

is

located

on

the

Main

reef

at

Hutti

gold

mines.

The advent of worldwide gold rushes in 19th century laid the foundation for present day mining activity. The gold boom was experienced in India with discovery and mining in Kolar, Hutti, Gadag, Ramagiri, Honalli, Wynad, in the South and a few in North viz, Lawa, Mysara, Pahardia, Kundrekocha, etc. Most of the old workings were closed due to dwindling production and prevailing cost-benefits. Geochronological data of gold metallogeny revealed major periods of enrichment as Archaean and Proterozoic. Gold occurs in a variety of litho assemblages, and multiple geological environments / settings such as greenstone belts, mantle derived intrusions, diaperic juvenile plutons and granulites. In the Indian subcontinent, prominent granite greenstone belts of Peninsular Sheild are located in Dharwar, Bastar, Singhbhum and Rajasthan cratons. The Dharwar craton, with two blocks viz the eastern and western, hosts the maximum number of gold occurrences. The Eastern block provides an important and favourable lithologic, structural and stratigraphic milieu for gold mineralization

and

hosts

major

deposits

like

Kolar

and

Hutti.

In the northwestern Indian Shield, gold occurs in association with copper in the Archaean

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greenstone-like

sequence

(at

Dhani

Basri,

in

Mangalwar

Complex)

and

Proterozoic

metavolcanosediments (at Bhukia and Dugocha, in Aravalli Supergroup) with enrichment in the latter. Gold also occurs in Palaeo / recent river alluvium placers, laterite, soil and regolith. Puga geothermal system is a “hot spring” type epithermal gold deposit in the making, in the Ladakh region of Jammu and Kashmir. In SGT, the primary gold mineralisation is recorded in three different geological settings viz.(i) Archaean greenstone belts similar to Dharwar Craton, (ii) in Banded Iron Formations (BIF) and amphibolite associated with granulites and (iii) in quartz-carbonate veins related to alkaline magmatism. Among these, the gold mineralisation associated with the greenstone belts is quite significant. Kolar Gold Fields (KGF) had been the primary gold producer in the country. From the position of a large producer in the world (790 tonnes since 1880 from a grade of about 16 gms/t), it became an insignificant gold producer with grades lowered to about 3-4 gms/t to about one tonne per annum in the mine.The KGF comprising the Champion, Nundydoorg, Mysore and Bisanattam mines is located in the central part of the 80 km long Kolar Schist Belt. There are two zones of subparallel lodes, sub-conformable to the meta-basite host rock viz., the Champion lode on the east and on the west the Oriental and McTaggert lode.Gold-polysulphide association were identified in Champion Reef and gold-pyrrhotite-arsenopyrite in McTagart lode with characteristic scheelite.The deposits are vein type with wall rock alteration, especially in the eastern part of the belt.The economical values of gold ore in the southern end of the Kolar Schist Belt came into limelight at the time the KGF values were uneconomical to mine and is marked by a number of old workings.Gold mineralization in the southern belt was established by GSI at Chigargunta, Mallappakonda, Bisanattam, Kudithinapalle and Avulathinapalle.The Chigargunta mineralization in the south is in non-conformance with that of the KGF to the north and is in distinct tectonised zones and post-dates the major folding and amphibolite grade metamorphism.The 3 km long mineralized zone occurs in the amphibolite and Champion Gneiss units as well as on their contacts, confined to shear zones.A reserve of 4.19 Mt with grade ranging from 4.2 to 5.22 g/t of Au over widths ranging from 1.46 to 12.05m was estimated. The deposit is under exploitation by the BGML. In Mallappakonda Block, auriferous zones associated with BIF are lensoid, parallel and enechelon occurring over a strike lenth of 400m.A reserve of 0.65 Mt of ore with an average grade of 4.3 g/t was established.In Bisanattam Block, both GSI and MECL carried out investigations for gold. The mineralized zones found in fissile amphibolite are lensoid, parallel and en-echelon in disposition and vary in width from 1 to 3

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m. About 0.13 Mt of ore with a grade of 5.1 g/t was established.The deposit was mined by BGML and since been closed.In Kudithinapalle Block, located 3 km south of Bisanattam Mine, gold mineralization in quartz reefs is hosted by both hornblende schist and Champion Gneiss. The quartz reef is about 100m long and 2 to 3 m wide. A reserve of 0.48 Mt ore with an average grade of 1.2 g/t was established. Molybdenum is also found in the quartz veins. Gold mineralisation is reported in the southern extension of the Kolar schist belt in Veppananpalli and Bargur sectors in Krishnagiri district of Tamil Nadu. In Veppananpalli sector, the southern continuity of the Kolar schist belt is traceable as two narrow linear strips, viz. the eastern Maharajagadai strip and the western Adakonda strip representing synformal keels. In the Maharajagadai block, eleven zones of gold mineralisation have been delineated within the silicified zones in quartz-sericite schist (Champion gneiss) occurring in association with amphibolite. The epigenetic gold mineralisation is mainly confined to the sheared and silicified zones in the quartz-sericite schist. Gold is associated with sulphides, viz. pyrite, pyrrhotite, sphalerite, chalcopyrite, arsenopyrite and galena of which pyrite is the most dominant. Exploratory drilling in this block has indicated a potential reserve of 0.07 million tonnes of ore with 1 to 2 g/t of gold upto 75 m vertical depth. In the Adakonda Block, gold mineralisation is confined to sheared and silicified zone in amphibolite and associated BIF. In this block, gold is associated with pyrite, pyrrhotite, arsenopyrite and chalcopyrite. The surface exploration, by trenching and groove sampling, has indicated gold values ranging from 0.2 to 2.57 g/t with an average width of 1.5 m over a strike length of 450 m. Near Bargur (15 km SE of Maharajagadai block), gold mineralisation has been recorded in the amphibolite band occurring within the gneisses. The mineralisation is traceable for a strike length of about 75 m over a width of 0.65 to 4.45 m with gold assay values ranging from 0.2 to 0.96 g/t. In the Hutti-Maski Schist Belt, gold mineralization is localized along the shear zones developed parallel/subparallel to S1 schistosity in both basic and acid meta-volcanic rocks.The Hutti Gold Mines located in the northern part of the belt produced 1048 Kg of gold during 1990-91. Extensive and detailed investigations were carried out by GSI in Hutti mines area, Wandalli, Uti, Hira-Buddini and Maski, proving sizeable gold reserves. In the Gadag Gold Fields of Chitradurga district, ancient workings and mines are seen over an area of 200 km2. All the known gold bearing lodes are confined to the western limb of an overturned syncline over a strike lenth of 15 km.The prospects explored by GSI are-(i) Western

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Group comprising Hosur-Champion, Yelishirur and Venkatapur mines hosted dominantly in metabasalts and meta-andesites, (ii) Middle Group comprising Kabuliyatkatti-Attikatti, Mysore Mine and Sangli Mine, hosted mostly in greywacke,and (iii) Eastern Group comprising Sankatodak Block and a fewer prospects east of Nabhapur and Kabuliyatkatti villages, hosted in greywacke. In addition, gold mineralization is also known from the area north of Nagavi hosted in BIF in contact with tuffaceous rocks. In the Anesidri-Ajjanahalli-Bellara area, Tumkur district, Karnataka, gold mineralization is associated with meta-volcanics as well as sulphide banded iron formation of the Chitradurga Group. In the Ajjanahalli block, 10 parallel zones of mineralization localized in shear zones in sulphidic BIF along a fold have been delineated by GSI. The strike lenth of the block is about 1500 m. The estimated reserves at 0.5 g/t cut-off grade are 0.77 Mt of ore. Very recent exploration for gold by GSI in Ajjanahalli Block-C, Tumkur district, Karnataka on.bedrock samples yielded gold value ranging from 0.10 g/t to 4.22 g/t. Analysis of trench samples indicated gold value ranging from 0.36 g/t to 6.0 g/t. In Ajjanahalli block-F, three major auriferous BIF bands have been delineated. Band-I (strike length 300m average width 3 to 4m) has recorded 1.02 to 2.2 g/t gold; Band-II (strike length 200m average width of 2m) has recorded 0.28 to 1.70 g/t gold; Band III (strike length of 700m average width 4m) has recorded gold values from 0.03 to 0.70g/t. The Ramagiri-Penakacherla Schist Belt extends over a strike lenth of 100 km with number of gold prospects grouped into two fields viz. (1) Ramagiri Gold Field (RGF) and (2) Bhadrampalle Gold Field (BGF). RGF has a reserve of 0.7 Mt with an average grade of 7 g/t in the Om Pratima-Gantalappa Block. In Kottapalle Block, north of this mine, a probable reserve of 0.11 Mt withan average grade of 2.65 g/t over an average width of 1.41 m was estimated upto 165 m depth. Auriferous lodes of BGF are of small length. A reserve of 0.023 Mt of ore with an average grade of 4.13 g/t of Au over an average width of 1.21 m upto 75 m depth for the main lode and 0.36 Mt with 2.34 g/t of gold over a width of 1.00 m upto 80 m depth for the northern lode has been estimated. In Ramapuram area, preliminary exploration has led to estimation of 0.07 Mt of ore upto a maximum depth of 70 m for 4 lodes over width varying from 1.29 to 1.56 m and gold content ranging from 1.28 to 1.39 g/t. Ancient mining activity is recorded in both the fields. Another prominent area of gold mineralisation is located in Wynad gold field in DevalaPandalur, Cherambadi and Kotagiri sectors in Nilgiri district of Tamil Nadu and in the adjoining parts of Kerala.

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In Devala-Pandalur sector, gold mineralisation is confined to zones of intense shearing and dislocation which have acted as loci for emplacement of auriferous quartz veins. The host rocks for these quartz veins are biotite gneiss with interbanded hornblende granulite and magnetite quartzite. The gold mineralisation is associated with intense wall rock alteration in the form of sericitisation and chloritisation. The gold-bearing quartz reefs show a general trend of N-S. Two main types of gold mineralisation have been recognised – one is sulphide-rich and the other is sulphide-poor type. Alpha-Victoria, Nadghani, Solomon and Hare Wood mines near Devala and Phoenix, Rosedall and Glenrock mines near Pandalur are the important old workings located in this sector. Samples collected from this sector have analysed gold content of 3.06 to 15.2 g/t. The exploratory drilling carried out in some of the old working areas reveal that in Alpha-Victoria mine, the gold mineralised zone is traceable for a strike length of about 1000 m over a width of 1 to 3 m with an average tenor of 1.98 g/t. In Hare Wood mine, the maximum strike length and width of the lode are 116 m and 30 m respectively. In Solomon mine, the lode is having a width of 2 to 5 m for a limited strike length of 40 to 60 m with grade varying from 1.9 to 6.04 g/t. In Cherambadi sector several old workings for gold are located in Mangorange, Duraiswamikaradu, Went worth-I & II and Cherangode. Auriferous quartz veins occur in sheared biotite gneiss showing intense sericitisation. In Mangorange tea estate, two quartz veins are exposed. The first one occurring in the form of two detached en-echelon reefs trending in E-W direction with 25 to 30º dip towards north. Among these two reefs, the prominent one is having a strike length of over 1.5 km with a width of 2 m. The other reef is measuring 100 m x 2 m. Another quartz vein has been traced for a strike length of 1.2 km with width varying from 1 to 3 m. In Duraiswamikaradu area, a quartz reef with a thickness of 1 to 3 m over a strike length of 0.8 km has been traced. This shows NE-SW trend with southeasterly dip in the southern part and N-S trend with 60º dip towards east in the northern part. In Went Worth-I & II old workings, three quartz reefs are exposed. The width of the individual quartz reefs varies from 20 cm to 5 m and traceable for a length of about 60m. The gold assay values of the samples collected from this sector are not encouraging. Gold occurrences and ancient mining activities are also reported from Adathurai-Kotagiri sector located in the eastern part of the Nilgiri hill ranges in Tamil Nadu. Preliminary sampling by GSI in the year 1967, from the old inclines, drives and trenches has indicated an average gold value of 2.41 g/t from 61 samples with 18.3 g/t being the highest value. Subsequent detailed studies by GSI (2004-06) have brought out that the Adathurai area is traversed by a major brittle-ductile shear

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trending N-S to NNE-SSW. All along the shear / fracture planes, emplacement of auriferous quartz veins is noticed. Chemical analysis of the trench samples collected from this zone shows an average gold values of 2.26 g/t over 2.5 m width and 6.2 g/t over 1.5 m width in two profiles. Similarly, the samples collected from an gold incline have analysed a maximum gold value of 22.9 g/t thereby indicating than this zone is a promising one for gold mineralisation. Four first level boreholes drilled in this zone have indicated the depth persistence of the gold mineralised zone at 50 m vertical depth. Although the assay values obtained for the core samples by AAS are not encouraging, selected samples analysed by Fire assay method have indicated gold values upto 5.8 g/t. In Gopanari-Velliyankadi sector in Coimbatore district, forming the eastern extension of Attappadi valley in Kerala, gold minerlaisation is reported within the fractured and sheared quartz veins emplaced along minor shears developed close to the major Bhavani Shear Zone. The general trend of the quartz veins varies from NE-SW to ENE-WSW and occasionally along NNW-SSE to NW-SE directions. The quartz veins occur as small stringers as well as thick veins having a maximum width of about 5 m over 150 m length. The quartz vein contains sulphides which are mostly pyrite and subordinate arsenopyrite. Limonitistion is seen along the fracture planes. A total of five zones of gold mineralisation represented by lensoid auriferous quartz veins have been delineated. These zones vary in length from 7 to 13.5 km. Samples collected from the auriferous quartz veins have shown gold values ranging from 0.03 to 3.5 g/t. This prospect falls within the Gopanari Reserved Forest area. Old workings for gold are also recorded in Bensibetta-Modikadavur -Inbakombai sector in parts of Erode and Coimbatore districts. Auriferous quartz veins are found within the sheared granitic gneisses which occur in association with charnockite, pyroxene granulite and minor meta-sedimentaries of Sathyamangalam Group. These lithounits show intense shearing marked by cataclasites, mylonites and phyllonites. Preliminary sampling by GSI has indicated gold values from 0.1 to 0.8 g/t. Wynad gold field is one of the earliest known gold fields in the country, where gold is found in quartz reefs. Placer deposits of gold are known from Nilambur valley in Malappuram district. In Kottathara block of Attapadi valley, Palaghat district, Kerala, 60000 tonnes of gold ore with an average grade of 13.6 g/t has been established.

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In Maruda area of

Malappuram district, are estimated reserve of 0.55 million tonnes of primary gold ore with an average grade of 4 g/t over a strike length of 350 m upto a depth of 100 m has been worked out by KMEDP. Preliminary exploration carried out by GSI by test drilling has indicated six parallel lensoid zones in en echelon pattern in Kappil prospect and two lensoid lode zones in Mankada prospect. Gold mineralisation is restricted to the highly sheared and fractured quartz vein within the biotite-hornblende gneiss and amphibolite. The grade of the mineralisation in Kappil prospect ranges from 1.28 to 4.58 ppm and preliminary estimate indicate 0.462 m.t. of ore with a gold content of 1726 kg in Kappil prospect. Gold mineralisation has been reported by GSI in epigenetic quartz veins emplaced within amphibolite / granite gneiss in Puttumala in Attapadi valley in Palakkad district. A structurally controlled mineralised zone with an average width of 1.75 m has been traced with a value of 7.3 g/t gold. Besides, preliminary gold occurrences are also known in Meppadi, Chundale, Vayittiri, Tariode, Vattam, Kuthimada, Karumsanthod, Thavingal, Venmani, Kakkarikunnu and Manathoddy areas of Wynad district in Kerala. The tenor of gold bearing reefs in Wynad Gold fields is generally 2 to 3 g/t. ii) Gold mineralisation associated with Archaean BIF in granulite terrain Numerous bands of Banded Iron Formation (BIF) occur in association with charnockite and pyroxene granulite within the granulite terrain in northern Tamil Nadu in parts of Dharmapuri, North Arcot, Tiruvannamalai, Villupuram and Salem districts. The BIF shows transition from quartzite (oxide phase), magnetite-orthopyroxene bearing quartzite (silicate phase) to silicified sulphide rich quartzite (sulphide phase). These BIF show intense shearing, brecciation and minor drag folds. Gold bearing quartz veins occupy the shear zones and fracture / foliation planes within the BIF. Preliminary prospecting of the BIF occurring in Melchengam-Attipadi-Thirthamalai belts and in Vediappanmalai-Kavuthimalai-Uchchimalai areas of Tiruvannamalai district has indicated gold values ranging from < 0.1 to 0.6.5 ppm. Samples collected from Kannakadu Malai and east of Ravathanallur in Villupuram district have assay gold values ranging from 0.28 to 0.6 g/t.The samples collected from the BIF of Nainar Malai, Idaiyappatti, Rasipuram, Kariyampatti and other areas have analysed 0.1 to 0.9 g/t of gold.

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The available data indicate that gold mineralisation in BIF is sporadic and the higher values of gold are mainly from the silicified zone in BIF. iii) Gold mineralisation associated with Neoproterozoic alkaline-carbonatite complex In northern part of Tamil Nadu, an array of alkaline-carbonatite complexes is found within the major NNE-SSW trending Dharmapuri shear zone. This zone is marked by intense shearing, hydrothermal alteration of the charnockite and the associated quartzofeldspathic gneiss with profuse development of epidote and carbonates and emplacement of several quartz veins. The HarurUttangarai molybdenum prospect is located within this shear zone. A few occurrences of gold are reported in the quartz veins as well as in the ankeritesiderite bearing quartzofeldspathic gneiss within this shear zone. The prominent among them are in Nekkundi area near Vaniyambadi and in Andipatti-Elavadai-Ammapettai and Vellakkal west sectors within the Harur-Uttangarai molybdenum belt in Dharmapuri district. In Nekkundi area, gold mineralisation occurs in the quartz veins emplaced within the sheared epidote-hornblende gneiss containing quartz-carbonate and ultrapotassic veins. The major quartz vein trending in NE-SW direction is traceable for a strike length of about 1 km with a width varying from 1 to 20 m. Chip samples collected from the sheared quartz vein with perthosite have analysed gold values ranging from 01. to 4.35 g/t with sporadic high values upto 10 g/t. In Andipatti area, a major quartz vein is traced for a strike length of 600 m with width varying from, 5 to 27 m. Out of 42 groove samples collected from the entire length of the quartz vein, six samples have analysed 1.05 to 1.25 g/t of Au, fifteen samples showing gold values from 0.2 to 0.8 g/t and five samples giving 0.04 to 0.15 g/t of gold. In Elavadi area, the auriferous quartz vein is 1 km long and 4 to 12 km wide trending in N20ºW-S20ºE to N-S. Out of 87 groove samples collected from this vein, two samples have analysed 2.46 to 3.10 g/t of gold, eighteen samples have analysed 0.11 to 0.73 g/t and six samples analysed 0.03 to 0.09 g/t. The remaining samples have shown < 0.03 g/t of gold. The 1.4 km long quartz vein traced in Ammapettai area shows a general trend of N20ºES20ºW with 20º to 40º dip towards southeast. The width of the quartz vein is 5 to 17 m. It shows intense shearing and wall rock alteration. Out of 117 groove samples collected from this quartz vein, five samples have analysed 1.1 to 5 g/t of gold and six samples analysed from 0.13 to 0.3 g/t. The remaining samples have shown gold values 0.5% copper) are confined to 4 discontinuous zones varying in length from 70 to 440 m. The cumulative strike length of the 4 zones is about 1380 m. The width of these zones range from 0.35 to 3.03 m (average 1.36 m) and copper content from 0.5 to 1.53% Apart from these, a parallel mineralised zone has also been established over a strike length of about 350 m. The width of this zone ranges upto 1.55 m and copper content ranges from 0.35 to 1.77%.On the basis of borehole data, the reserves estimated in this block are as follows : Indicated - 77,180 tonnes with 0.95% Copper and 9.31 g/t silver. Inferred - 314,150 tonnes with 0.95% Copper and 9.31 g/t silver. Total = 391,330 tonnes. Ingaldhalu North-east block : the copper content varies from 1.14 to 3.38%. The reserves estimated in this block are of the order of 0.16 million tonnes with a copper content of 1.79%. Ingaldhalu South block :In this block, copper mineralisation has been traced over a strike l length of about 750 m. The copper content in the sulphide zones vary between 0.1 and 2.2%. Zinc ranges from 0.32 to 10%, generally between 2 and 6%,and lead from 0.3 to 9%, generally between 0.5 and 2%.Reserves have not been estimated from this block, since the average copper content is