Lateral and Vertical Alteration-Mineralization Zoning

 

ECONOMIC

GEOLOGY AN'D

BULLETIN

Vo..

OF

THE

THE

SOCIETY

OF

ECONOMIC

GEOLOGISTS

JuNE-JuLY, 1970

65

Lateral and Vertical Alteration-Mineralization oning in PorphyryOre PorphyryOre Deposits j. DAWDLOWELL DAWDLOWELLANDJOHN M. GUmBERT Abstract

The geologichistory geologichistory of the San Manuel-Kalamazoodeposithas deposithas provided an opportunity for the examination of vertical and horizontal zoning relationshipsin a porphyry copper system. PrecambrianOracle "granite," a Laramide monzonite monzoniteporphyry, porphyry, and a Laramide dacite porphyry are hosts to zones of potassic, potassic,phyllic, phyllic, argillic, and propylitic assemblages assemblages hown to be coaxially arranged outward from a potassic potassiccore core through phyllic, argillic, argillic, and propylitic zones. Alteration zones at depth comprisean outer chlorite-sericite-epidote-magnetiteassemblage chlorite-sericite-epidote-magnetiteassemblageyielding yielding to an inner zone of quartz-K4eldspar-sericite-chlorite. quartz-K4eldspar-se ricite-chlorite. Mineralization zones are conformable to the

alterationzones, alteration zones, he ore zone (with a 0.5% Cu cutoff) overlappinghe potassic nd

phyllic zones. Occurrence Occurrenceof of sulfideschanges sulfideschangesupward upward and outward from from dissemination at the low-grade core of the deposit through microveinlet to veinlet and finally vein occurrence ndicating the progressively ncreasing ncreasing effect of structural control. Several aspectsof aspectsof San Manuel-Kalamazoo geology suggest hat it is exemplary of the porphyry copper deposit depositgroup. group. To test that idea and to evolve three-dimensional aspectsof aspects of these deposits, table of geologiccharacteristics geologiccharacteristics f 27 major porphyry deposits is presented. Consideration Considerationof of the table indicates hat the "typical" porphyry copper deposit is eraplaced in late Cretaceous sediments and metasediments metasedimentsand and is associated ith a Laramide (65 m.y.) quartz monzonitestock. monzonitestock. Its host intrusive

rock is elongate-irregular,,000 elongate-irregular,,000X X 6,000 feet in outcrop,and outcrop,and is progressively ifferen-

tiated from quartz diorite to quartz monzonite n composition. The host is more like

a stock han a dike and is controlled y regional-scaleaulting. regional-scaleaulting. The orebody s oval to pipelike, with dimensions f 3,500 6,000 feet and gradational boundaries. Seventy Seventy percent of the 140 million tons of oreXoccurs n the igneous igne oushost host rocks, 30 percent in preore rocks. Metal values include0.45% include0.45% hypogeneCu with 0.35% supergeneCu,

and 0.015%Mo. Alteration s zoned rom potassic potassic t the core (and earliest) earliest) outward through phyllic (quartz-sericite-pyrite), (quartz-sericite-pyrite), argillic (quartz-kaolin-montmorillonite), (quartz-kaolin-montmorillonite), nd propylitic (epidote--calcite-chlorite), (epidote--calcite-chlorite),he he propylitic zone extending 2,500 feet beyond the copperore copperore zone. Over the same nterval, sulfide sulfidespecies species ary from chalcopyritemolybdenite-pyritehrough hroughsuccessive successivessemblages ssemblages o an assemblagef assemblagef galena-sphalerite with minor gold and silver values in solid solution,as metals, and as sulfosalts. Occurrence haracteristicshift haracteristicshift from disseminationshrough respective respective ones onesof of microveinlets (crackle (crackle fillings), veinlets,veins, veinlets,veins, and finally to individualstructures individualstructures n the peripherywhich periphery which may containhigh-grade containhigh-grademineralization. mineralization. Breccia pipes pipes with attendant crackle

zones a are re common.

Expressionof Expression of zoning is affected by exposure,structural exposure,structural and compositional omogeneity, and postore faulting or intrusive activity. Vertical dimensionscan dimensionscan reach 10,000 eet, with the upperreaches upperreaches f the porphyryenvironment porphyryenvironment erhapsonly at subvolcanicdepths volcanic depthsof of a few thousand eet. The vertical and lateral zoning described describeds s repeatedwith sufficient onstancyhat onstancyhat depthsof depthsof exposure t many deposits an be ci cited ted against the the model of San Manuel-Kalamazoo. 373

No.

4

 

374

.t. D. LOWELL AND J. M. GUILBERT Several ines of evidence uggest elativelyshallow elativelyshallowdepths depthsof of formationand formationand significant variations variations n water content n the porphyry environment. Shallow emplacement is consistent ith the appearance f brecciapipes pipesassociated associated ith ring and radial radial diking and with vertically telescoped oning. Models of the sourceof sourceof altering-mineralizing fluids are considered.

Contents PAGE

Introduction

.................... ................................. .............

Genetic modelsof modelsof porphyry deposits .......... Geologyof the San Manuel-Kalamazooeposit . Fresh rocks ................................ Alteration zones ................... ........................... ........ Mineralization zones ..................... ........................ ...

Comparison f porphyry deposits ............. ............. Deposits (column 1) ....................... Preore host rock (column 2) ................ Igneoushost Igneous host rock (columns3-11) (columns3-11) ........... Orebody (columns12-19) .................. .................. Hypogenealteration(columns 0-27) ........ Hypogenemineralization mineralizationcolumns columns 8-35) .... Occurrence f sulfides columns 6-42) ....... Supergene ulfides column43) column43) .............. .............. Genesisof Genesis of porphyry deposits ................. Conclusions

......................... .................................. .........

374

375 376

378 381 385

386 386 386 386 399 400 402 403 403 403

404

acteristicswhich link Bingham Canyon and many otherdepositso depositso the generalporphyry generalporphyrycopper copperdeposit deposit type. There appears o have been ittle published effort specificallyo specificallyo compareand compareand contrast he porphyry deposits deposits s a group. The first portion of this paper describesboth

lateral and vertical

alteration-mineralization

relation-

shipsat San Manuel-Kalamazoo Manuel-Kalamazoo.. The exploration model includedand includedand substantiatedpproximately substantiatedpproximately 0 degrees of postmineralization postmineralization ilting. Thus this geologic system provides provides information concerning both vertical and horizontalaxes horizontalaxes of a porphyry deposit. A three-dimensional three-dimensional ynthesis s given of hydrothermal lterationmineralogy lterationmineralogyand assemblages, of the distributionand distributionand quantitativeaspects quantitativeaspectsof sulfides, and of the structural occurrenceof occurrenceof sulfide and oxide minerals.

Vertical

treatment

of alteration

and

mineralization eometry s still tentative,but tentative,but some References ................................... 406 vertical zoning changescan changescan be identified. Comparison f other major porphyrybase-metal porphyry base-metal Introduction depositso deposits o San Manuel-Kalamazoo y meansof publisheddata lished data assembledn Table 1 permitsdeveloppermitsdevelopExv•.o1•,•T•oNff the Kalamazoo ortionof Exv•.o1•,•T•oN ortionof the San zonation Manuel-Kalamazooistrict,Pinal istrict,Pinal County,Arizona, County,Arizona, ment of a generalized ateral and vertical zonation depositgroup. Finally, that model s has presented n unparalleled pportunity or the model or the depositgroup. used to examine the genesis gen esisand and environmentof environmentof studyof study of a porphyrycopper porphyrycopperdeposit depositn three dimendimenporphyrydeposits. The data sugsions. The coaxialsymmetry coaxialsymmetry f alteration nd min- formationof the porphyry gest that it is sometimespossible sometimes possible o estimate the eralization oneswhich oneswhichwas was the basisof basisof the explorasurfacesof other tion model has been verified in the exploratory position of the present erosion surfacesof porphyrydeposits depositswith respecto their originalcoloriginalcoldrilling Lowell,1968) of the Kalamazooortionof porphyry umns of mineralization. mineralizatio n. Depth parametershave parameters have the district and in exploitationof exploitationof the San Manuel beenassigned assignedo o nine deposits, nd it is hoped hat portion. As explorationproceeded, explorationproceeded,tt became n- been be made creasinglyapparent creasingly apparent that many elementsof elementsof min- both scientific nd explorational se can be of three-dimensional lteration-mineralization oning. eralog-y,ccurrence,nd ccurrence,nd geometry geometry f otherporphyry copperdeposits copper depositswere explicitly represented t San The porphyrycopper porphyrycopperand and molybdenum eposits, hereaftercalled called"porphyries," "porphyries,"must first be defined. Manuel-Kalamazoo. Zoning Zonin g patterns here can be hereafter necessarilylexibledefinition definitionemerges emergesrom conconsidered refinedbase refinedbase or the studyof studyof mineraliza- A necessarilylexible sideration f many deposits nd descriptions descriptionsff a tion and alterationrelationships alterationrelationshipsn other porphyry copperdeposits, nd this this is the subjectof the study "typical" one. reported here, with compilationof compilationof data from 27 A porphyrydeposit porphyrydeposit s here definedas a copper major porphyrycopper porphyrycopper nd molybdenum molybdenumeposits epositsn n and/or molybdenum ulfidedepositconsisting depositconsisting f mineralieraliNorth and SouthAmerica. Most significants significants the disseminated and stockwork veinlet sulfide min emplacedn varioushost varioushostrocks hat havebeen emergencerom the many descriptions f a more zationemplacedn generally applicableunifying applicableunifying theme of large-scale altered alteredby by hydrothermal hy drothermal olutionsnto roughlyconalteration-mineralizationoning alteration-mineralization oning in these large de- centric zonal patterns. The deposit s generally posits hanhas hanhasgenerally generally een ecognized.Stringham ecognized.Stringham large, on the scaleof severalthousandsof feet, al(1953, p. 990) stated hat "a review r eview of hydro- though smaller occurrences re recognized. The thermal studiesof studiesof porphyrycopper porphyrycopperdeposits deposits hows relatively relativelyhomogeneous homogeneousnd commonly oughlyequioughlyequias many dissimilaritiess similarities similaritieso o the hydrohydro- dimensionaldeposit deposit s associatedwith a complex, thermal features at Bingham Canyon." We now passively mplaced tockof intermediate omposition omposition take the opposite osition hat there are many charchar- includingporphyry units. It containssignificant containssignificant Acknowledgments Acknowledgme nts .................. ............................ ..........

406

 

.4LTERATION-MINERALIZATION

ZONING IN PORPHYRY

amounts f pyrite,chalcopyrite, olybdenite,uartz, and sericiteassociated sericiteassociated ith other alteration,gangue, alteration,gangue, and ore mineralsand mineralsand metals ncludingminor ncludingminor lead, zinc, gold, and silver. silver. Mineralizationand Mineralizationand alteration suggesta suggest a late magrnatic-mesothermal emperature range. The deposit s generallyassociatedwith brecciapipes, breccia pipes,usually usually with a large cracklebrecciation zone,and zone,and is surrounded y peripheralmineral mineral

ORE DEPOSITS

375

to depthsapparently depthsapparently n the order of 3,000-5,000

feet. The modeldepends modeldepends n a melt derivedat derivedat some greaterdepth, greater depth,probably probablynear the mantle-crust oundary, which becomes aturatedwith aturatedwith water as it approaches he upper up per surface. Releaseof Releaseof that water may occur when internal vapor pressuredeveloped pressuredeveloped by supersaturationxceeds supersaturationxceedshe he lithostatic lit hostatic oad pressureor sure or when he intrusive intrusive ystems ystems rent by external

deposits uggestivef uggestivef lowertemperature mineralizamineralization.

stresses. Crystallization hen proceedspresumably along he linesof linesof Emmons' 1933) cupolaor R. H. Sales'ssub-hood Sales's sub-hood upoladevelopment. upoladevelopment. The grade of primary mineralizationn typical As described y Nielsen (1968), the sequencef porphyry opper epositsanges epositsanges p to 0.8% Cu and and eventscan can be paraphrased s intrusion,early intrusion,early mar0.02% Mo, and porphyry epositsn whichmolybwhichmolyb- events ginalcrystallization ginal crystallization hich hichproduces produces solidshell,and solidshell, and denite s the chief economic ineralhave ineralhave grades ruptureof of that shell o produceporphyritic-aphanitic ranging p to 0.6% Mo and 0.05% Cu. All por- rupture textures n subsequentlyrystallized ocks. Volatiles phyry copper deposits ontain at least traces of migrateoutward hrough migrateoutward molybdenite,nd ndall porphyrymolybdenumeposits released y the quenching stockwork,and brecciatedzones brecciatedzones n the cooler containsome contain somechalcopyrite. chalcopyrite.Many Many deposits ontain crackle,stockwork,and marginswhere, margins where, augmented y diffusioneffects, diffusioneffects, lterrecoverablequantities recoverable quantities of both minerals, either in mineralization ccur n responseo responseo gradiseparate rebodies r in ore with approximatelyation and mineralization ents"from "from near magmaticemperatures magmaticemperatures t the center equal copperand copperand molybdenum ollar values. Al- ents of the stock to relatively cool temperaturesn temperaturesn the thoughypicalporphyry porphyry opper epositsiffer epositsiffer rom reactionsof typicalmolybdenum typical molybdenumepositsn some espects,he he wall rocks" (p. 37). Silicate sulfide reactionsof existence f gradational haracteristics haracteristicsn metalliza- the typedescribed typedescribedy y Hemleyand HemleyandJones Jones 1964) prevail. Other authorswould authorswould not necessarilyimit the tion suggests common rigin. This definitions somewhateneralized somewhateneralizedecause ecauset separationof volatilesto the period of quenching, mustpermitconsiderationf many deposits hose but rather would consider volutionof the hydroquasi-continuouseparation eparationof localgeologic local geologicircumstances ircumstances ary as expressedy expressedy thermal fraction a quasi-continuous volatiles n responseo responseo the many variables variables elated their geometriesnd physical haracteristics. haracteristicsWe . temperat ure nd pressure. The loss of volatiles vo latiles believehe believe he porphyry epositso be a petrological-to temperature from near-surface ortions ortion s of a melt may permit the mineralizational lass, nd ndividualorphyry ndividualorphyry epositsare posits are best nterpreted s greateror lesserde- upward and outward replenishment f mineralizers greaterdepths. partures from the unifying model of the above from greaterdepths. Fournier (1968) suggestshat suggestshat the initial deep definitionselaboratedpon elaboratedponbelow. below. porphyry coppermelt was unsaturatedwith unsaturatedwith water at one to three percent, percent, that it was intruded to Genetic Models of Porphyry Deposits depthsof less les s han ha n about4,500 about4,500 feet,and that rupSeveral eneticmodels models avebeen avebeenproposedo re- ture by faultingwould faultingwouldcausesudden, venexplosive venexplosive of water and supercooling supercoo ling f the silicatemelt. silicatemelt. late the characteristics porphyry copperand and loss molybdenum eposits.All Allfofporphyrycopper the models modelsecognize ecognize Crystallizationwould then abruptlyhalt abruptlyhalt the upward the important nvolvement f porphyriticntrusive porphyriticntrusive progress f the now dry melt. Subsequent extenrockswithoredeposition, oredeposition,nd ndall all are fundame fundamentally ntallysive siveargillic argillicalteration alteration hownby mostporphyry mostporphyrycopmagmatic-hydrothermal, iffering n the sequencesper depositss depositss probablydue probablydue to a superimposedirsuperimposedirof events, epths f intrusion,he he timingof timingof deriva- culating culatinghot-spring hot-springsystem, system, ed mainly by meteoric tion of fluids, and the sourceof sourceof fluids. The models and cormatewater" (p. 101).

considered ere are the orthomagmatic odel, Fournier's model of intrusion of a water undersaturated melt, and the White model of multilevel

circulation f brinesadjacent brinesadjacent o a heat source. The orthomagrnaticodelhas odelhasbeen beenbest bestdescribed described in therecent therecentwritings writings f Burnham1967) Burnham1967) andNielandNielsen(1968). It is the geneticmodel model acitlyadopted acitlyadopted

in mostdeposit mostdeposit escriptions, s for example,hose hose

White (1968) in a particularlystimulating particularlystimulating aper suggestshat circulationof sulfur-deficient a-Ca-C1 brines, with salt contentsgenerally contentsgenerally equivalent o 5%-to 40% NaC1, are responsibleor many basemetal deposits. Such brines may may be produced n porphyry systemsby deuteric reaction of residual liquids with earlier formed plagioclase nd ferromagnesianminerals o achievehigh achievehigh contentsof contentsof cal-

ciumand andbasemetals. basemetals. AlthoughWhite AlthoughWhite in his paper described n Titley andHicks and Hicks (1966). It as sometimes involves enetration f the source o levelsas levels shallow cium doesnot does not develop specific pace-time odel or the

at 1,500 e eet et (Nielsen, 968), 968),but but morecommonly morecommonlyporphyry deposits,he deposits,he implicitly developsa developsa model

 

376

.r. D. LOWELL AND J. M. GUILBERT

portions.Theupper upperKalamazoo Kalamazooortionmoved bout involvingmultilevel involving multilevelcirculation circulation f deutericallymetal- portions.The enriched or cormate-meteo cormate-meteoric ric sulfur-deficient metal8,000 feet in a down-dip,S55øW down-dip,S55øW direction. Small, h high-angle,orthwest-trending igh-angle, orthwest-trending ormalaults ormal lizingsolutions nder he influence f thermal t hermalgradigradidisplacedothhalves halves f the originalorebody, orebody, ents established y an adjacent or subjacentmagsubjacentmag- later displacedoth t rippedmost mostof of the Gila Conglomerate Conglomerate matic heat source. The model differs importantly and erosion tripped from the east end of the presentSan present San Manuel oreorefrom the orthomagrnaticmodel in that the source of the solutions,and solutions,and perhapsthe metals, is almost body (Fig. lb). The original,unfaulted unfaulted rebody, s defined y a completely xternalto the magmaticsystem, magmaticsystem,with with convectiveoverturn of circulating solutionspro- 0.5% copperimit, formed formeda a slightly lattened r which wasat at least7,700 least7,700 eet ong ducingalteration-mineralization ducing alteration-mineralizationnvelopes nvelopesnd nd zones. elliptical ylinderwhichwas and from 2,500 to 5,000 feet in diameter. The top cylinder, t the eastendafter endafter ilting,may ilting,mayhave have Geology of the San Manuel-Kalamazoo Deposit of the cylinder, been rounded,with rounded,with the bottom,at bottom,at the west, having The San Manuel-Kalamazoo Manuel-Kalamazoo deposit (Lowell, an irregularshape. irregularshape. The centerof centerof the orebodys orebodys 1968), located in Pinal County, Arizona, is here poorly poorlymetallized, metallized,o o that ore actually ormsa ormsa hol-

accepted s the type porphyrycopper porphyrycopperdeposit, deposit, nd low cylinderor cylinderor cylindrical hell. The shell surits geologyand geologyand other o ther characteristicsre presented roundinghe ow-gradeenter ow-gradeenter ariesrom ariesromabout about 00 for comparison nd contrastwith contrastwith others (Table 1). to 1,000 feet in thickness. Mineralization nd alterPrecambrianquartz monzonite of the Oracle ation zonesare approximatelyoaxial. approximatelyoaxial. Granite batholith in the San Manuel area was inThe alterationassemblages alterationassemblages n the San Manueltruded in Laramide time by swarms swarmsof of monzonite Kalamazoo Kalamazooeposit epositorm ormregular, regular, moothlyounded moothlyounded porphyry dikes and irregular massesof monzonite zones, zones,which, which, as in most porphyries, porphyries, re locally porphyry, more properly termed biotite latite por- gradationalnd nddifficulto difficulto placewithin withina a hundred phyries, although ong-establishedmonzonite ong-established monzoniteporpor- The feet,although feet, although heyare hey wellclearly defined n a broad phyry" terminology will be followedhere. followed here. Closely boundaries reare more defined hanscale. they related in time a and nd space to the activity was a are in mostporphyry mostporphyrydeposits,resumablyecause resumablyecause porphyrycopper porphyry coppermineralization vent hat produced the mineralizingluids luidsaffected affectedntrusive, ntrusive, ssentially the San Manuel-Kalamazoo rebodyand rebodyand its associ- homogeneous, sotropiclutonic sotropic lutonic ndhypabyssal ndhypabyssalost ost ated concentric lterationzones. lterationzones. The hydrothermal rocks rocksof of intermediate i ntermediateomposition. omposition. hese ocks esystem ppears o havebeencentered beencenteredn n the middle spondedo the indicated indicatedlkali lkalichemistry chemistry ithout of the monzonite orphyrydike orphyrydike swarm,and swarm,and metal- important ainsor losses.No losses.No marginal ediments, lization is almost equally distributedbetween distributedbetween he compositionally ontrastingntrusiveocks,planar ocks,planar monzoniteporphyry and the Oracle Granite host rock fabrics,or fabrics,or prominent ectonicelements ectonicelements rorocks Fig. 1). duced teep hysicalr chemical chemicalradients radientso influFollowinghydrothermal Following hydrothermalmineralization nd alter- ence the uniform zoning and symmetry. ation (Fig. la), the whole district districtwas was tilted to the Mineralogiconing Mineralogic oning t Kalamazoond Kalamazoond elsewhere northeast, nd n d the block ncluding nclud ing he San Manuel- suggests hatat least our hat ouralteration alterationssemblages ssemblages re Kalamazoo rebodywas wasprobably probablyelativelyelevated. easily iscernible n theporphyry theporphyryopperndmolybndmolyb-

Erosion of supergene this block exposed he topaofthin thechalore- lic, denum heave terms potassic, hyllic, hyllic, rgilbody, and ctivity formed andeposits. propylitic avebeen beenadapted adapted r adopted cociteenrichmentblanket. enrichmentblanket. At this time, the long from he iterature Burnham, 962;Creasey, 962;Creasey, 966; axis of the orebodymay orebodymay have plungedat about Meyer and Hemley, 1968) to describe describehe he four 65øSW. Shortly thereafter, errestrialsedimentsprincipal ssemblages.he he terms"argillic" "argillic"and and "propylitic"re "propylitic" re well knownand knownand widelyaccepted, widelyaccepted, began o cover he deposit. Further tilting, perhaps15ø 15ø followeddeposition followeddepositionbroadly describingquartz-kaolin-montmorilloniteof the lowermost Cloudburst Conglomerate. An chlorite-biotite nd chlorite-calcite-epidote-adulariaespectively. Phyllic" erosion surface surface form formed ed on the Cloudburst sediments albitealteration ssemblages, is here applied o the assemblageuartz-sericitewas later coveredby coveredby the Gila Conglomerate.A

third-stageilt of about30 third-stageilt about30ø ø gave he Gila Conglomerate ts present nclination nclinati on ndbrought he originally verticalaxis verticalaxis of the San Manuel-Kalamazoo rebody nto a 20ø 20ø southwest-plunging ttitude. The ttitude. San Manuel Manuel ault thendiagonally ffset he original, orig inal, nearly cylindrical cylindric al rebody nto two roughlyequalroughlyequal-

pyritewith ess han5% han5% kaolin, iotite, r K-feldspar,and spar, and "potassic" s suggested Guilbert nd Lowell, 968) o in include cludentroducedr recrystallized K-feldsparndbiotite, K-feldsparnd biotite,withminor withminorsericite sericitendhighly ndhighly variable ut persistentnd persistentndgenerallyminoramounts minoramounts

of anhydrite. Each of these theseassemblages assemblages be more ully descri described bed elow, specially s theyoccur theyill occur sized ieces,he he SanManuel SanManuel nd he Kalamazooat San Manuel-Kalamazoo. ther assemblages

 

.4LTERATION-MINER.4LIZATION

ZONING IN PORPHYRY

ORE DEPOSITS

377

pCqm

OREBODY

12

sw

•

.

•qml •{ • KALAMAZ•

SAN M•NUEL FAULT Cc•

SAN

-

NE

•

SEAMEN

_

•.•.'

0 lb

10•00'

I

I

Approximofe Approximo fe Scole

Fxa. 1. Schematicrawing Schematicrawingof structural istoryof istoryof SanManuel-Kalamazooeposit. (a) at time of emplacement and (b) at present. Note the umbrella-likelare of dikeswarm dikeswarmand the chalcocitenrichment chalcocitenrichmentone CCa). pœqm-Oracle Granite,TKrnp= TKrnp= monzonite orphyry,Tcb orphyry,Tcb= = Cloudburst ormation, gc = Gila Conglomerate.

rarely encountered n the porphyry nvironmentre The alterationzones alterationzoneswere were separated uring Kalathe advancedrgillic advancedrgillic (Meyer and Hemley, 1968) mazoo exploration as follows. The inner limit of and pegmatoid,espectively pegmatoid,espectivelynvolving nvolvingquartz quartz and the propylitic one onewas wasplaced placedwhere he total quartzpyrophyllite,ith pyrophyllite, ith races f dickire r kaolinire,opaz, opaz, montmorillonite,quartz-kaolin, quartz-kaolin, or quartz-sericite and zunyite, zunyite, nd quartz-coarseericite-K4eldspar, content in plagioclase ites exceeds he total of with or withoutcarbonate, withoutcarbonate,nhydrite, nhydrite, nd apatite. chloriteand epidotereplacing epidotereplacingmafic mafic minerals; here Hydrothermalalterationassemblages alterationassemblages n the San the color usually usually changes rom green to light gray. Manuel-Kalamazooeposit re summarized n Fig- The argillic zone, n which kaolin or montmorillonite ure 2, which showsalteration showsalterationchangesmineral mineralby by predominates predominatesn n plagioclase ites and chlorite chlorit e remineraland mineral and assemblages n AKF-ACF diagrams. placesbiotite,was not generallymapped generallymappedseparately separately significantquantitatively. The inner Supergene ctivity is limited to a 200-foot thick and is least significantquantitatively. zonenear zone near the top of the deposit. limit of propylitic alteration is locally the outer

 

378

J. D. LOWELL AND J. M. GUILBERT

SHALLOW-MODERATE EPTHSSEMBLAGES' EPTH SSEMBLAGES' FRESH IM,

PROPYLITIC ONE

PORPHYRIES

Quartz OrthoclaseMicrocline Plagioclase (An35.45)

ARGILLIC ONE

NoChange NoChange

Augmented

NoChange NoChange

Chloritized, leucoxene,tz tz Chlaritized

...

trocepyr re trocepyr

A-K-C-F

Pyritized

•Ac.(kaol}

Augmented Recry•tallized, npart eplaced by byalteration alteration -felclspar-quartz

Sericitized

Montmorill Montmorillonite onite , Kaolin

Biotite Chlor, ois, car, leucoxene Hornblen_d..e.._.p, p,car, car,mont, hlor 2 types)

POTASSIC ONE

Augmented

Flecked ith ithSericite Sericite

Tr. Mont, lecks& lecks& granulesp, zois, car, chlorite, aol.

Magnetite

PHYLLICONE

Fresh o completelyeplaced y brn-grn lt'n biotite,K-spar, K-spar,ser. ser.

Sericitized

Fresh or recrystallized recrystallized ta sucrose

Sericite,pyrite, pyrite, utile Sericite, yrite, uffle(?)

brn-grn ranules, chlorite Biotite, Biotite,+ + chlorite•utile chlorite•utile

Pyritized

•A•.kool

Pyritized

A

A

A=A' ,a•a - ?•Cp x.•,•F •,,.••• y, [,•,e /• =Casalts

CK

= Fe,Mg Fe,Mg

•rt

VeinletFillings

,•..•/,,;•car

r

.

•..•

ß

F "•

O-cal- K-spar-chlor-rare K-spar-chlor-rareb-rt

Q-ser-py-chlor Q-ser-py-chlor

DEEP-LEVEL

O-ser-py

Microcline

Plagioclase (An35-45)

Biotite_ Hornblende ,

•9•t•te

Dustedwith racesericite

AlterationK-sparwith withsericite, elictscommon, inor uartz

Dustedwith sericite, ohiorite,epidote ohiorite,epidote Largelychloritized, Largely chloritized,minor pidotemag pidotemag dded Chlorite Epidote Carbonate

Sericitized,with with alterationK-s•r-quartz, alterationK-s•r-quartz, relicts uncommon Chloritized,areprimaryelicts Chloritized; Chloritized;race racecarbonate carbonate

Augmented

A-K-C-Fer•• = K, Na

K

C

F = Fe, Mg

Mostly yritized A

K

r?

ab,k-spar• _chl •mag,py

VeinletFillings

Q-K-spar-bi-ser-anhy-cal-ap Q-K-spar-bi-ser-anhy-cal-ap

Augmented

A

C = Ca salts

P troce troceff

INNER

SlightlyAugmented

Orthoclase-

'•.•-- py, pt•,mb

ASSEMBLAGES

OUTER

•uar•z

I•i

r?

•mag-py • Q-ser-cal envelopes

k-•ar

•

/•

car?

mb

Q-K-s•r-ser-chl, Q-K-s•r-ser-chl, tr mag,py, mag,py, cp• mb

Fro. 2. Summary of hydrothermal hydrothermalalteration alteration assemblagest assemblagest San Manuel-Kal Manuel-Kal,amazoo. ,amazoo.

Fresh Rocks limit of either the argillic or the phyllic zone of pervasive conversion o quartz, sericite, and The unaltered unaltere d rocks at San Manuel-Kal Manuel-Kalamazoo amazoo pyrite. The inner limit of the th e phyllic zone is the includePrecambrian includePrecambrianOracleporphyriticquartz porphyriticquartz mon-

outer limit

of the first con continuous tinuous

section of sec-

ondary K-feldspar and secondary biotite, even though the total quartz and sericite content here ordinarily exceeds he total K-feldspar plus biotite content. The zoningpatterns zoningpatternsand and intercepts an be projectedremarkably projected remarkablywell well from hole to hole. Subsequent etrographic tudy tudyhas hascontributedo contributedo these descriptions f the zones,and zones,and subsequent ublicationsby J. M. Guilbertdescribinghe describinghe chemical nd structuralmineralogy structural mineralogyand and physicalgeochemistry physicalgeochemistry f the alteration-mineralizationrocesses alteration-mineralizationrocesses re planned. In the following sections,he sections,he fresh rocksat San

zonite and two of muchisyounger ycoarse oungergrained biotite porphyries. The.varieties Oracle "granite" coarsegrained (Fig. 4) with anhedral subrounded uartz units about a centimeteracross centimeteracrossand and commonly angential to their nearestneighbors, nearestneighbors, ectangular o irregular plagioclaseablets plagioclase ablets (Anas_45), (Anas_45), nd interstitial quartz and K-feldspar. K-feldsp ar. K-feldspar species ncludemicroncludemicrocline,orthoclase, cline, orthoclase,nd nd microperthite. Severalauthors, Severalauthors, especially anerjee 1959) haveconsidered haveconsideredhe rock palingenic, lthoughmany lthoughmany other workers accept ts orthomagmaticrigin. Accessoryminerals nclude biotite and hornblende,with hornblende,with trace amountsof amountsof zircon,

apatite,sphene,magnetite, nd very sparsemonazite. apatite,sphene, The porphyriesare porphyriesare of at least two types. One zonesexposedon exposedon a horizontalplane horizontalplane at moderate (here calledType A) is a quartz monzonite ordepth are described uccessivelyutward uccessivelyutward from the phyry distinguishedy distinguishedy its zonedand zonedand twinnedoligotwinnedoligocenter. Alteration and mineralization mineralizationchangeswith clase-andesinehenocrysts hich averageabout averageabout 5 depthare discussedast and are summarized cheche- mm and range up to 15 mm across Fig. 5), its quartz-K-feldspar roundmassommonly roundmassommonly ontaining matically n Figure 3a. Manuel-Kalamazoo

are first discussed and alteration

 

ALTERA TION-MINERALIZA SAN

TION

MANUEL

KALAMAZOO SEGMENT

/

ZONING

IN PORPHYRY

ORE DEPOSITS

379

FAULT SAN

MANUEL

SEGM.•.ENT

PROPYLITIC

/

Chl- pi- arb

Adui Aib.

•HYLLIC •'•

/

- Ser-py

/

\

ARGI LIC

I

)TASSIC

\

Q K-feld Bi-

\

•

-+ er• er•anh •

%

VEINS

PER PHEAL PHE AL p-gal,sl Au-Ag

VEINS

VEINS

PERIPHERAL cp-gel-el

Au-Ag

VEINLETS DISSEMII•

ED

DISS '4-

MICRO VLTS

DISS mag +

Fro.3. 3. Concentric lteration-mineralization onestt SanManuel-Kalamazoo. ones a) schematic rawingff alteration rawing zones. rokenines nKalamazoo nKalamazoo idendicate ide ndicatencertain ontinuity ontinuity r locationnd nSan nSanManuelide ide xtrapolation fromKalamazoo. from Kalamazoo.b) schematic rawingf mineralization rawingf ones. c) schematic rawingff theoccurrence rawing theoccurrence f sulfides.

 

380

.T.D. LOWELL AND J. M. GUILBERT .T.D.

..:.

-.....:• . '. -. •,.:;

•

•' .-e•'•':

ß

:

..,

.

.•.:.z

v•

:•,• -: • : •. •.:--•a ;• .3• .3• •.., ..

ß

ß

;• :•v... :-

.•. :

.•.

• •:• % ..•.:•; .-.< •.•- %:.•:• ..... :.•:•

:

•

:2•.'2:•

.5. ':L.

,•

': •

. ß

.

ß.

Figure

..

4

.:..,.::• .....•...:•..:: ..-....•;...:. :':. '.•;'ii•":,•.s

......... "•.-. ::•'•-:;• - .... : .•1 /.:..;;:i'•" ,?:.:.:--":-' .:.:--":-' ,•-.,.-. ,•-., ::•'•-:;•.... • .

'-

•: ...

:. -. •" •:.

..

• . ,. :• :-' * :•''••i•""• '••i•""• ""

•.:..,;.•.:.-.. .,•.:.. ...• .;'.• :.:.•-i..•. •...• ....

'...-:..i•..'.' .:.?...**;,:.q;.:•.-•.. .:.?...**;,:.q;.:•.-•.. ..?:..... ..... •.,..:•.:

::'• :} .

'* ....:• %'•"' ';'• . •' • ':•"-;½,.,, ....:• ./ .... .• .•"• "• * '.':.•i X.. -• ':•'.: - :•.•.. -:•: ...... ;: .•**,-'.;'.*; .•**,-'.;'.*;".: ".: •-:..:•.•• ß., .....'.-: •.• .•L:• .• L•":: %•- ; .' :" '•1•'?': •'•-:'-:'•'X: : t•:.• t•:.•• "*• • dike

-4Qmp -4Qmp

Qd 4 Gd 4 Dacp Dacp .4 Lp .4 Rhy

all

'"g'ci66';F•6i• .................................................................................................................. ........................................................... assive> active stock> dike Qd •; ................................................................................... Gd; /p, QIp all + seds ........................

'"•iiti•i'•''6'6i• '"•iiti•i'•' '6'6i• .................................................................................................................... ................................................................................ ................................................................................ assive> active stock 'Qp' ;''feld Qp' all + seds (both altered)

4000x 4000

passive> active

stock> dikes

Qd 4 Dac Dacp p 4 I_p 4 Iph

And, Qd, Dac Dacp, p,

150,000 350,000

passive

batholith

Qm apl, peg)-4Qmp

all

8000 25,000

passive> ctive

stock dike

Dio,Gd, Dio,Gd,sy, sy,G.4 QI• E•b

all + seds

stockdike stockdike

Gd4Qm4Qmp Gd4 4G 4Gp Gp4 4Db

Qm, p& Db

sodo d4Qd Qd4 4Dio Dio4 4Qm4

all(?)

Rhy Rhyp p 4 apl p 4 Gp

all

cluster

'"•J'l•'l•'•'•'•'•J•[.... '"•J'l•'l•'•'•'•'•J•[ .... passive

'"•'C•'•"•"(•J•J•J•'-• ..... passiveactive(?) stock dike

/p

................................................................................................................................... ...•.•.p. ....o...a..•...a..p. ....o...a..•...a..p. ........................................................... 4- 3000x 3000

active

stock> dike

tock Qm ' apl alsk ,"-; Db all '"•/6•i'/i•';/"i'•i/i///'//'/• ......;';';•i'•;• ...... ;';';•i'•;• ............................................................................. ......;......... ......; Gp ...... ................................................

'"/•/'•';•"i•;'6•/// ................. ;';';';i'•;; ............................................................................ -;........ ........ ;'Qp' ................................................................. tock> tock > clikes,sills clikes,sills Gd -; Gdp all large,elongate large, elongateEW

passive

stock dikes,sills dikes,sills

M, Qmp omplex

all + seds

tock> dike Qm.4 G • alsk reid ; ................................................ all '"¾//61iJiJii";,"i'•ii6i•;"c/6'6 ........;•';i;;;;¾.*'• ............................................................. ............................ ....................................................... ........ ...................... ;Q............ .............................. ..................

'";/•;'•i:i";,"•;/•i•i• ...................... ......................................................................................... ............................................... ................................. -•..................... -•seds ..................... ass,"•;•......................................................................................... stock> dike Qm.4Dio ; Qmp.4 Andp And p all .............. seds& & voles

0,000 all -7/•;';•;•;•i• '"•/6/c•i:i';• ........................... ;;•';i'•;; ............................. ,';;'•'•;"•/ii•; ..................... 5i;"•;"'•'•'5':-;"i5i; .................................... ....

'"•6///i';i'•///•.............................. '"•6///i';i'•///• .............................. ass,' e .......................................................................................................................................................... stock Qd 4 Qmp Qmp4 4 Qp' 4 Qp'+ Q Qmp 'C)p'

............................................................................................................................................................................... ...p.2+...9. ............... +__4000 4000

passive

sill > stock

Qmp

all + seds

'"•'¾i•;'666';•' b;'6'66 ............ ; ';' ; " •'•;i •'•;i'• '• ............... i ; ii " "ili'l g ............ •i'; ;"-7o;;; ;"-7 5';,"-; 5';,"-; 6i;..................... ..................... '•;;' '•;;' i ;.......... in wall tock dike Mp, Gp, bio....................... G •; apl, apl ........ d[l: voles "i'•'6i:iii;,"•//ii•i• ............... ;';;';'i•;; ............................ ............. .......................... ............................... ............... ........... ............................... •;............... ............... ;; ;;..................... ..................... .....................

..................................................................................................................................... a...•..y....p. ................................................................................. 8000x 8000 x 15,000

passive

stocks dikes

Qd 4 Db 4 Qmp4 Qmp4 And 4 Qmp4 Qmp4

all + metaseds

2000x 2000 x 4000

passive

dikeswarm dikeswarm

QIp,Rhy,Dac, Rhy,Dac,Qd, Qd,Gd Gd 4 Dac4

all + vales

;4000 7000(?)

passive

stock dike

Mp 4 Qmp Qmp4 4 Db

all

..................................................................................................................................... . ,...k,...a...•.y. ,...k,...a... ........................................................................ •.y. '";/'66/i';F•//• .............................. ................................................................................... •;.................................... .................................... •;........................................... ........................................... ass,ve stock> dike Dio •; Qd+ hbl Gd & bi Gd •; Qd, Gd+ seds

......................................................................... ................................... ...................................................................... ................................ .m.• ......................................................................... > 10,000NE 30, oooNW oooNW

passive

stock si I > dike

alsk 4 Dac Dacp p 4 Andp Andp 4 Omp

all + seds

"i'g66'•"•'•'6'6' ..................... /:'ilk;; ................................ ;;/'i;i'•';'•½"/li'i/g ................ •'g"/; ................................................... ;ii"•'i;;Fg"•,'g'i•;•"' 4000x 4000 x 6000

passive

stock dikes

Dio 4Qm4Qmp4 Qmp4 Op'

all + seds

 

390

.t. D. LOWELL AND .L M. GUILBERT

OREBOD'Y

D E P OSI T

Outward hape

Boundaries

(12)

Aio

Percentn Preore Rocks

(14)

(15)

(13)

oval, elongate W

Arizona

Percent n IgneousHost Igneous Host

original& faults

80?

20?

........................................................................................................................................................ 4:10 .................. .................. longateoval original +_90 +_90

Arizona

"ifii;'d4

................................................................................................................................................................................ teep,elliptical cylinder original -t-50 +50

British Columbia

Bingham Utah

pear-shaped,longate longateWSW original

75

25

........................................................................... .................................... ............................................................................. ................ ................ longateEW, longate EW,oval oval original&............................................................................. faults + 30....................................................... + '6'................

Arizona

(incl. bx)

Braden

Chile

............

Butte

0 ..........

o ......................... .......

Montana

Cananea Sonora

,• .........................

CastleDome

0,oo,

, ................ ..

,,,,o,0,,

...........

•o,,,,

, .....

....

,o,

,..,0 o..,,,o0,0 ..... , ......

El Salvador Chile 0 ...........

0,.,,

.....

Nevada

.......................... ..

British. Columbia ............

,o

Arizona

...............

...................

,,,

.....

.......

, .........................

0 .............................................

, .....................

,,,.o,,.,,o.,

o .................

100

0

................................. ................................... ......................... .. ........... ,.,

original Original NE & N• faults • .........

, .....................

,...•.,

40(?) 100

.........

0 .....

0.,,,.,

...........

, .........

60(?) 0

............................

, ...........

70(?)

?flat cylinder

original with faults

80

20

elongate val

original

100

0

• ............................................ ............................................ ............................................ ............................................ ..................................... .............

,.,.0,

above & below

.......

,,.,

, ....

,,,o,.,

•.,.o ................

original

30(?)

....................

0 .........

original

60(?)

40(?)

original & fault

50

50

........

crescent, convexSW

Arizona

+ 10

o .............................................................................................. ........................

oval pipe, lower lowergrade grade

flat cylinder

, .........

+ 90

• .......................................... ........................................... ........................................... ............................................ ............................................ ............................................ ............................................ .......................................... ..................

Mineral Park ,,

nested, nverted ones oval, elongate W .......

0

• .......................... ......................... ........................ ......................... ........................ ........................ ................... .....

elongateNW NWoval oval

,.0.o.o

Arizona 0 .........

o,.o

..............................................

............................................ ............................................ ............................................ ............................................ ............................................ ............................................ ............................................ ............................. .....

Inspiration .o .....

original& NW ault original&

0 ,,

Esperanza oo.,

o ................................................................................................... .........................................

, ....................... ...........

75

100

............... o ................. ......

• .....

Endako 0,

original originalbreccia brecciapipe pipe

25

pipe

center

0 ..............

Ely

....

pipelike

....................... ........

,.,,,,o,,0,,o.,00

Arizona

.........

original

oval, elongateNE

Colorado Climax Copper ities

.o[,,• .........

crudely omical

......................

Chile

o0,•.o,•,,

original& postore reccia original&

............................................................................................... ....................................

Arizona

.0 .....

hollowcircularcylinder hollowcircular

o .......

, .............

+ 100

0 ................ .................. .................. ...

Mission-Pima

, ................. .................. ......

oval

Ari zo n a

•

, ................. .................. .........

original& fault

, .....

+ 10

0

, .........

, .........

o ....

+_90

_ 70 orenci oval original + fault ...................................... ................................... .................. ................................... .................................... .................................... .................................... ................................... ................................... .................................. ................................. Arizona

o.,,,o,o,0..,,.,..,,, ,,,

o0.,...,..

.....

0.0

......................................... ..................

Questa

New Mexi co

,,...,

0,.0.,.,,0

...................

Ra•rizon

,0o,,,,

.......

,..,0,0,0.o,0 .o0

, .....

........

Ari zon a .....

, ...........

,,0

........

0 ......

, ......

Safford ,,.0o,

, ............................................ ........................................... .....................

irregular 0o.

.............

irregular val,longate longate W original ault

, .....

, .............

Arizona

, .......

0 ...........

, ................ .................. ................... ......

oval, dippingpipe

, ................. ...

0 ......................

30(?)

20

80

0 ................. .................. ...

original

0 ................ .................. .................. .......

20

• ................ .................. .................. .................. ..........

, ...........

0 ....

80 0 ................. ............

0.,

original

50

50

oval• elongate elongateNW NW

original

+_70

+_30 +_30

elongate val mineral mineralbelt belt

original

70

30

...............

, ...............

SantaRita Santa Rita .......

0 ..........

70(?)

, ............................................ ............................................ ............................................ ............................................ ............................................ ............................................ ........................... ...

SanManuel-Kalamazoo San Manuel-Kalamazoo hollowoval hollowoval cylinder ,0 .................

o ........................................... ......................

original

New Mexi co , ...................

Silver Bell

Arizona ......... o, .... , ............................

Toquepala

,,,,0 .................................... ........................... ..........

TypicalPorphyry Copper

oval, elongateNW

oval, pipelike

, ................................... .................................... .................................... .......................... ......

original: brecciapipe brecciapipe

original& original& postoreaults

0 .....

• ................

70

70

, ................................. ..................

30 (walls

30

 

ALTERA TION-MINERALIZA

TION ZONING

0 R E BODY-

Dimensions (feet) (16)

Total Ore Tonnoge (million) (17)

IN PORPHYRY

ORE DEPOSITS

391

Continued

Grade Hypogene+ Supergene (18) 0.75%

Cu

Grade Hypogene Only (19)

4000 x 7000

< 500

0.75%

Cu

1000 x 5000

< 100

0.76% Cu

2000 x 3000

< lr00

+ 0..025% Mo 0.6% Cu

+ 0.025% Mo 0.6% Cu

5000 x 7000 WSW

> 500

0.75% Cu 0.05% Mo

0.75% Cu 0.05% Mo

2000 x 2000

< 100

0.81% Cu

+ 0.55% Cu

ñ 5000 x 5000

> 500

2.25% Cu

1.00% Cu

5000 x 10,000 EW

> 500

0.8% Cu

0.2% Cu

250 x 1200

> 500

0..8% Cu

0.5% Cu

•_ 1500 x 3000

< 100

+ 0.70% Cu

+ 0.5% Cu (?)

2500 x 10,000

> 500

+ 1.7%.

+ 1.2% Cu

+ 0.5% Cu

... •?..r.?.:..y. ..................................................................................................................................................................

...•.o.).o...w...:..y. .................................................................................. ?..4?..r O....O..5.•...a..o. ....................................... 0...O..5.•...a..O.. ..O..5.•...a..O.. ................ ....r.•.?..•.:•.s..a..p. . ........................... ............. ......................... ........... • ?. .:.t.? ......................................................................................................................... .......................................................................................................................

"';ii:Ji:JiS' ":ii:Sti/5 ................................... :'•6i:i....................................... ....................................... "6'.'•/qo' /,i•................................... /,i•................................... •'i3•i•;i'qo"//• ................. 1500 x 2000

< 100

+ 0.60% Cu

+ 0.4% Cu

  500 1.5% Cu ND '" '"õiSi•ti' õiSi•ti' ,";/ti/5/5 ................................ .................................................. ' .....................................................................................

+ 1000 x 3000 x

< 500

1200 x 6000

> 100

+ 0.9% Cu

+ 0.1% Cu

+ 0.09% Mo

•_ 0.09% Mo

........1..o..-...2..o.,..o..o..o. 1..o..-...2..o.,..o..o..o. ............................... ............... ................................. ................................. .............................. .l...•.2.•...:.o...m..m...o.?. .............. ............................... .0.:.4..•. ..o..m...m..o. ................ ................ ß

2300 x 4200

.( 100

0.51% Cu 0.028% Mo

2500 x 8300

< 500

0.90% Cu

+ 0.3% Cu 0.028% Mo 0.15-1.20% 0.007% Mo

Cu

.... iJiS'•"•';i6•.............................................. .............................................................................................. ................................................................................................ ................................................................................ ................................   100 0.5% Cu 0.1-0.15% Cu 0.04% Mo

0.04% Mo

) 500

0.8% Cu

0.8% Cu

6000 x 13,000

) 500

0.88% Cu

0.1-0.15% Cu 0.007% Mo

7000 x 7000

) 500?

0.15-0.18%

3000NS x 10,000 EW

( 500

0.80% Cu

+ 4000 x 5000

> 500

0.50% Cu

cross section: 2500 x

> 500

4- 0.75% Cu

5000NW

x 7000NE

5000 x 4- 8000 high 5000 x 7000NNW

....2000x 2000x 2500& 2500& 1500 x 2500

4000WNW x 5000NNE

3500 x 6000

< 500

< 100 • 500

150

0.015% Mo 0.97% Cu

Mo

0.15-0.18%

Mo

0.10-0.80% Cu + 0.2% Cu

-t- 0.75% Cu

0.1-0.2% Cu(intr) 0.8% Cu (tactite)

............................................................ .......................................... .................. J•':•'"6•l'•"E•'iig;i• ... .75% Cu 0.8% Cu (tactite)

0.9% Cu

0.3% Cu

0.80% Cu 0.015% Mo

0.45% Cu 0.015% Mo

 

392

.r. D. LOWELL

AND .1. M. GUILBERT

HY D E P O S I T

Known

POG

EN

E ALTERATION

Extent

Beyond Ore (ft)

Peripheral Zone

(20)

Outer Zone

(21)

Intermediate Zone

(22)

(23)

Ajo

+ 5000

Bagdad

500 +

ND

not reported

not reported

Bethlehem

+ 300

ND

Q, chl, ep

Q, kaol, mont

Bingham

3000 +

chl, talc, kaol, ep,

Q, chl, kaol, cal, ep

Bisbee

7000?

Arizona

Arizona

British Columbia

?chl, ab, zo, ser, Q, ank

........u..t• u..t•.......................................................... .......................................................... •.r..,..m..?..•.,...•..y..x. ......................................................................................................... Arizona

chl, ep, zo, cal, ser ?

kaol, ser(?)

raden .............................. .............. ............................. ............. 4:•6i:3• .................. •'i;'•37•};7•'•;• .......'•'i:;;;,7'• ....... '•'i:;;;,7'• 3; •i;•;•'•;•ii........ ........,;•'"'"•'•,';; ,;•'"'"•'•,';; 7;;,'i;•'•................. Chile

tm

Butte

1000 +

Q, chl, ep, cal

Q, mont, kaol

Cananea

5000

chl, ep

Q, ser, kaol

Castle Dome

3000

chl, ept py, ser, cal &

mont

Chuquicamata

few hundred

chl, ep, cal, spec, hm,

kaol ) ser

Montana Sonora

Arizona Chile

c l zo

TiOx

limax 2000? .............. .............................. ................................. ................................. ................................ ................................. .............................. 7'•i'i•i7•;'C.,'i ............. .................. ';'•'•';'•'•'• ................................ Colorado

CopperCities Copper Cities Ari zon a

5000 +

ep, cal, clzo, ser

mont, Q

.......................................................................................................................................................... l Salvador 1000 + py, chl &';•;ii'ii• ................................... Chile

............................................................................................................. ;-g•.•.ii¾i•;;• ...................................................................... ly 2000 Nevada

..........................................................................................................................................................................................................

Endako

British Columbia

Esperanza .0ooo

Arizona

...........

, .....

2000 + (?)

kaol weak, Q, cal

kaol moderate, Q, chl

ND

not reported

Q, kao , mon

chl, ep

Q, ser, kaol

Q, ser, 'clay'

Q

skarn, tactitc, hornfels

present

chl, ep

Q, mont

ser, Q, py -3_ al, kaol,

ser, Q, py -3_ al, kaol, ill

, ......................... ......................... ........................ ......................... ......................... ........................ ......................... ........................ ......................... .......................... ........................ ........................ ................. ..

Inspiration

1500 +

MineralPark

10,000

Mission-Pima

up to 5000

Morenci Arizona

) 5000

Questa

2000 + (?)

Arizona

, ................ ....

chl, ep, clzo,

.......•.r ....... •.r .z..o.?.?. ..................................................... •.t?.•.t. ..................... (.•.•. .•. ............................................................................. • Ar i zo na

skarn on SE

............................................ ............................................ ............................................ ............................................ ............................................ ........................................... ............................................ ........................................... ........................... ...

New Mexico Mexico

...........................................................................................................................................................................................................

Ray

1000-15,00 1000-15,000 0

Safford

-3_ 2,000

Arizona Arizona

ser, car, kaol, ep,

chl

i l I, fl

chl, ep, ab, cal, mont o

20,000 x 30,000

ep, chl

"chloritic"

....g•'•'•'•'•'" g•'•'•'•'•'"•'•'•'•'•g .... ....5•5•5•5"'•'6'•6 5•5•5•5"'•'6'•6 .............................................. ' •i4i';'•;',"fi•'i .................... •7•fi•;'i•'gf;i ............................. Arizona

.... ....•a'•"•i• •a'•"•i• ..................... 5000 New Mexi co

tactite

tactite

ahl,ep ahl,ep (Argillic)

.... ii•;•;"8'gl'•' ..................................... ........................................... ........................................................................................... ............................................................................................... ................................................. .. 3_ 2,00• •5000 chl, cal, ser, mont Q, ser, kaol Arizona

a Iteration zone

Toquepala

m nor; cp> mb

py > cp> mb

cp, gal, sl,

py • cp(?)

py • cp

py • cp • mb

Au, Ag, gal, sl

py, cp, sl, gal

py, cp

py, cp, mb

.......u..t..• ....... u..t..• ............................. . :.t..t ........................................................................................................................................... ND

py, cp, bn, cc, mb, mb,s sI

.......•• .•..o.•....................................................................................................................................... ....... ....................................................................................................................................... .y, •.p..•...]..0.•. ........................... py ) cp ) bn ) mb ) en

.......•• .?............................ ....... ........................... .t.•:.•.y. ................................................................................................... m.•..•.•.n. ................................... Montana Sonora

py, bn• cp, tn

py, cc, en•bn

py, cp, bn, mb,sl, gal

py, cp, bn, mb

py

py • cp • mb

py • cp • mb

py, cp

en, cp, co, bn, py(?)

en, cp, cc, py, bn(?), mb

py,tz, fl, hn, hn,cs cs

mb, cp

py

py• py• cp• cp• mb

py• cp mb

py, spec

ND

py - cp

........•: •: .•..o.,?.• ........................ ..•.,...v..,..•.o.,.. .p.•.................................. .p.• ........................................................................ ............................................................................ .................................................... ..............

........a,.. ....... .a,.. ......................... . .e. ..• ........................................................................................................................................ Arizona

Chile

py, cp, high total sul

.........a..• ........ .a..• .......................... .t•. •. ..n..•.a.• ................................................................................... . ?.•....s..-.. ..0. .......................

.........•). .•). ....ce.. •.m.• ............................. .......................................... ............. .py->Au

not recognized 1000 ft

ND • ........................................... .........

mb at depth

.... . •.•..o.:. ...................................................................................................................................................................... .................................................................................................................................................................. py (1%); cp(1-3%)

mb (0.01 -0.05%)

................................................ ..

low total sul; py•1%;

py:cp= 10:1

py) cp) mb

• ..................................................

py•cp•mb•bn

cp->py-> gal, sl, Au, Ag)

i .................................................. .

low.gradecenter-> nnular

ore zone & (cp, mb)->py->

cp->py

•. .............................................. ......

py zone contracts contracts& & py:mag increases

................................. ................ ................................. ................................ ................................. ................................. •.•..,..?.. ........................ ,..?. . ................ ................................ ........ ................................ ................................. ............................. ............ py, cp, bn, tt, mb,-sl

py• cp• mb• bn• sl

cp->py-> Ag, gal, sl)

ND

Q, tm+minor sul

py+__=p•bn, mb

(Q, tm)->cp->py

not observed

py• cp?mb• bn; low 3%) tot sul; py:½p 3:1

py• cp•mb•bn

(cp,mb)-•py-• mb)-•py-• (gal, sl, Ag, Au)

(cp,mb)-• mb)-•py py

anhydrite at depth

 

396

.t. D. LOWELL AND J. M. GUILBERT OCCURRENCE

DE POSI T S

Peripheral

Alteration

OF

Outer

Zone

Alteration

(36)

SULFIDES

Intermediate

Zone

Alteration

(37)

Inner

Zone

Al•erati6n

(38)

Zone

(39)

AJ•rizon

veinlets

diss/•vlts

diss/•vlts

Bagdad

vns & massive

vlts • diss

diss • vlts

Bethlehem British Columbia

veins

veinlets

veinlets

veinlets

Bingham

veins &

vns, vlts, diss

vlts, diss

diss) vlts

Bisbee

vns, vlts,

ND

ND

vns, vlts, diss

Braden

veins

patches & vlts

vlts & patches

vlts • patches

Butte

vn, vlt

vn, vlt

vn, vlt

vlt, vn, diss

Cananea

vein

veinlets

vlts, diss, mass.

vlts• diss

Castle Dome

veins

veinlets

diss • vlts

diss • vlts

vns & vlts

vlts • diss

vlts • diss

vlts •

vlts •

.......•• .z..o.n.• ....... ........................ r.•.p. •?.m..•?.t. ............................... .............. ................................. ................................ ................................ ................................. ................................. .......................... ..........

........u..t•.•. u..t•.•. .............................. ..•.• •.m..•?..t .................................. ................ .................................... ................................... ................................... .................................... .................................... ............................. ........... Arizona

mass. repl.

Chile

Montana

So•ra

Arizona

............................. ......

, .......................................... ........................................... ............................................ ........................................... ............................................ ................................ ........

Chuquicamata Chuquicama ta Chile

..............

0 ................................... ............

veins

, ................. .................. .................. .................. .................. .................. .................. ................... .................. .................. .......

Climax

vns & dikes

Colorado

.................

, .......

, ............................................ ............................................ ........................................... ................................... ............

CopperCities

,,..

veins

Arizona

veinlets

diss

diss

............................................ ............................................ ........................... ...

di ss • vlts

di ss • vlts

"' •i"'•i•'•;• ...................... ...................... ,'•i• ........................... ............................. i';•5•'ii•"•' .. ................... ................... ;i•'•';'•'ii•".• ................... i'•"•;i¾•'............... ............... Chile

............................... .........

,,

........................................... ........................................... ........................................... ............................................ ................................ ........

, .......................................... ................................ ........

Ely ......................

diss • vlt

Nevada

, .......

, ................

, .....

Endako British Columbia

...............

, ...........

veins

Arizona

............................................ ........................................... ............................................ ........................................... ............................................ ............................................ ............................................ ............................................ ..........................

Inspiration Arizona

....................

vlt • diss

vlt • diss

vns & vlts

vlts

vns & vlts

vlts •' diss

diss • v.lt , .......

, ..........

, .......

vlt •--

0 ........................

vlt

. ............................................ ........................................... ............................................ ............................................ ............................................ ............................................ .......................................... ..................

Esperanza .,,.,

, ............................................ .................................................. ..

veins

, ...........

,.,

Mineral Park

......

,..

...........................

..,

veins

.................................................................

diss • vlts

vlts • diss

ß ...............................................................

vlts• vns, stkwk

vlts• vns, stkwk

vlts, vns• stkwk

.......•r. •r. .z..o.?.? ................................................................. Z.q.i..?..P.?.?. .................. • :•.7...?.P. . ..•.."..•. ................ :•.'.•. ..P. ..?.•.?..•. .......... Mission-Pima

.......................... ......

Arizona

vn & vlt

,.,.,o,o,,,0

Morenci Ari zon a

......

, .....

0 .............

. .....

, ......................

vlt, diss &

. .................................... ..............

. .................................... ............

vns, Is repl.

....................................... ...................

Questa

New Mexi co

............................................ .................................. .............

,.,

Ray

vlts • diss

. .................

veins ...........

vns, vlts, diss

veins

SanManuel-Kalamazoo SanManuel-Kalam azoo

.................... ........

Arizona

, .....

SantaRita

vlts

0 .........

Safford

. ........................ .................. ...

New Mexico

......................... ....................... ......................... .......................... ........................ ........................ .......................... ........................ ....................... ..........

ilver Bell Arizona

......

0..,,,

veins

0 .....

vns, vlts, diss . ............................................ .......................

in shears, vns,

.,,0.....•

veins

,..

o,,0.,,0

• .......................... ......................... ............

vns & tactite

, ..............

,,.,,..•0,.,0

.....

,..,

vns & vlts

, ......................................... ............................................ ............................................ ............................................ ................................... ...........

.......................................... ............................................ ............................................ .................................. ............

.........•..z..o.•?. •..z..o.•?. .....................

massive

vns, vlts, diss : ..................................... ........................................ .............................. ........

paint

. ..............

0 ...........

ND

ß ..................................... .................................. ............

veins

Arizona

. .........................

....

, ........

eikes .......

vlts

........ ....

.o...

, ..........

vns & vlts

..........

in shears, vns,

dikes

,..,

J ............... ..

vns & tactite

, ....................... ...................... .............

vlts • diss

. ......................... ......................... ........................ ......................... .............

,

vlts,, diss, vns , ............................................ ......................

vns & vlts

.................. ......

. ....................... .......................... ....................... ...........

vlts • di ss

in veins, vlts, diss , ......................... ................ ...

vlts • diss , ........................ ............

, ..........

vlts,/•vlts• diss

vlts • diss

, ............... ...

........................................................................................................................................................................... ii'•'•'•:'•i¾•'............... ............... oquepala veins di ss • vlts Peru

Typical orphyry Copper

veins

vns vns& & vlts

bx vug fillings

bx vug fillings

veinlets

vnlts diss

 

.4LTERATION-MINERALIZATION

OCCURRENCE

OF

SUL.

ZONING IN PORPHYRY

ORE DEPOSITS

FIDES-Continz•ed SUPERGENE

Innermost

Alteratio0

Zone

Crackle

Breccia Pipes

(40)

(41)

SULFIDES

Zones

(43)

(42)

beyond ore limit

not reported

diss •/•vlts diss •

397

minor co, cv

Its

....i¾;"•;';1'/;';' ............................... ;;;; ;;:i'•,";,;'/;•';;;;;ii'•';,';i ........... ;'/ii-;•'f;; ;'/i i-;•'f;;;';•';;;"•,';;;,' ................ ,';';,'; .......................................

.................................. ................ .................................... .................... .. ................ .................................. .................................... ................................... ................................. ................

.... Ji'•'•'•";'i•; ........................n ........................ n gal,sl sl zone

extendseyond extendseyondal, al,sl sl

co,cv co,cv

important; 2 stages

NE horsetail zone

cc

vlts • patches

postore with min. frag.

present

cc • cv

diss • vlt

none

horsetail zone

cc, cv, dg

vlts• diss

numerous numerous& & mineralized

....................................................... p..,.

............. ............. .............. ............. ......

vlts)

; ............. ............. .............

diss

present

co, cv

i- ............ .............. ............. .........

present?

irregular clots

....

...............................................................................................................................

.• .............. ............. ............. .........

present

large central pipe

horsetail zone

co, cv

minor breccia, dikes

present

none

present

present

co,

cv

diss,/J. lts

deep, central, mineralized present

cc • cv

diss)

present

co, ½v

vlt

. ........................................... ..

present

• ................................................ ..

• ................................

, .................

ß ............................................. .......

diss • vlt

not reported

present

none

diss • vlt

present

present

cv, cc

vlts • diss (?)

not reported

.......................................... .............................. ........

•

present

......................................... ................................ ........

•

cc

.......................................... .............................. ......

,•

.............

, ...................................... ...............

vlts, vns, stockwork

none

present

cc

vlt, diss & massive

ore N-S dike;

poorly developed

cc• thin zone

....

....,

co, cv

...........................................................................................................................................................

...................................................... .p.:...•..a. .,..?. ......................................................................................................................... :..t..t. breccia zones• in pit

......................................

, .........

,.

vns & vlts ......

extensive

................................................ ..

present, important

, ...................................

, .......

vlts• diss, vns

co, cv

> ..................................................

ß ...........................................

extensive

............................................. .....

. .........

none

• .................................................. .................................................. ..

present & mineralized

present

cc• cv

ß

..........

. .......................... ........................ ............. ..

• ...................... .......

vns, vlts, diss

, .......................... ................ ..

present & mineralized

.......................................... .............................. ........

• ............................. ..........

diss • vlts

, ....................

................. ................... ..............

mineralized

::: :::: :: :::•:

diss )//vlts

::: ::::•:::•;;:

small

;:::J: '.:;•::

:::::

ß ................................... .............

NW horsetail

mineralized

:::::::

:: ::•:: :: :::: :::,::

ß

................ ................... ................

ß

.................. .................. .................

cc • cv

zone

cc .........

, ................ ...........

............. '• •"•'•'•;•';,'•'•'•i'•' •"•'•'•;•';,'•'•'•i'•' ..... cc ::::: ::::::

present& present& mineralized

:J::::;: ::::::::

:;: ;::: :::; ::•: ::•:;;

present

::::::

, ................

cc

samearea.as samearea.as intrusive • .................. .................. ..............

none

. .................. .......

co, cv

• .................. .................. ..............

one 500x 2500 ft pipe•

.... •'•'•:¾•' '•'Ji'i '•"•' •i'•'•........... •i'•'•........... •;•'•"•'•'J•i'•'J "•' •;

......................... ...................... .........

+ 5000 ft diameter

• ................. .................. ...............

ND

,•

• .......................................... ............................... .......

• .................. .................. ..............

vlts•/J. lts, diss

, ......................... ......................... .............

present

not reported

................. ................... ..............

',; :• •:•;•::;::::

• ..........

:: t.'::; '-:: :::: • :::: ::: ::;: :•: ::::: ::;: :::::

cc) cv

•,

', ::: •:::;:::

.............

•:: ::: :::: :.

 

398

I. D. LOWELL AND J. M. GUILBERT

associatedwith them, but bu t evidence shows that ore

depositionwas essentially ontemporaneousith intrusionwithin the precisionof precisionof the I(-Ar technique. Age dating of the Laramide-mid-Tertiary Laramide-mid-Tertiary interval in the Southwest eportedby Damon and Mauger (1966) has indicated wo distinct pulses,one of Laramideplutonic ctivitybetween ctivitybetween 0 and75 and75 million years ago and one of dominantlyextrusive dominantlyextrusiveactivity activity

to be related o contemporaneousnd younger aulting and uplift. Table 1 shows hat most most of the host igneousbodies bodiesare are somewhat longateand longateand that districts with strong structuralcontrol structuralcontrol tend to include pronouncedlyelongatestocks. Column7 Column 7 lists the size of igneoushost rock outcrops for each district, the numbershaving been taken from texts or measured rom geologicmaps. geologicmaps.

duringmid-Tertiary time approximately 0 million These dimensions re in part subject o the same uncertainties s the descriptionsn descriptionsn Column6. The dimensionsndicate ndicate that the porphyry copper deTable 1 includes ges or depositsn depositsn British Co- dimensions lumbia and South America as wall as southwestern positenvironment posit environment ascommonly ascommonly evelopedn stocks North America. Six of 27 depositsare of mid- or cupolaswith crosssections crosssections f well under a square Tertiary age at 30-37 million years,17 are probably mile at the elevationof elevationof ore deposition.There apin the Laramide range of 59 to 72 million years,3 pear to be two host-rock ize izepopulations, populations, ne group are in the Jurassic ange of 122-143 million years, less than a mile square sq uareand and another smallergroup smallergroup dimensions. ions. and 1 deposithas a 200 millionyear Triassicdate. Triassicdate. of very large dimens Mode of Eraplacement Column 8).---These 8).---These enOf the Southwestdeposits Southwestdeposits ncluded n Table 1, all are of Laramideage Laramideage except hree mid-Tertiary mid-Tertiary de- tries adoptthe terminology nd tend to confirm he posits (Climax, Questa, and Bingham) and two conclusions f Stringham (1966) regarding mode emplacement. Stringham's Stringham'scriteria criteria are extended Jurassic epositsBisbeeand Bisbeeand Ely), two of the mid- of emplacement. additional tionalporphyry porphyry copper deposits Tertiary onesbeing onesbeingporphyry porphyrymolybdenum molybdenumeposits. to include the addi The pattern for porphyry dates emerging in described ere. Emplacement f the porphyry porphyrycopcop-

years ago.

British Columbia eemso eemso be one in whichparallel, overlapping, orthwest-trending orthwest-trendingrits rits of mineralization increasen increasen age from west to east. The single numericalage for a South American deposit n Table 1 is for Toquepala, eru, at 59 millionyears. millionyears. However,geologicelationships geologicelationshipsndrecentdating recentdatingby by Chileangeologists Chilean geologistsndicate hat many of the South Americandeposits American deposits re of mid-Tertiaryage. Controllin#Structures Controllin# Structures(Column 5).--Column 5 lists attitudesof attitudesof regional-scale tructures hought to

have controlled he emplacementf the stocksand batholithsand hencethe porphyry deposits hemhem-

selves. Considerationwas Considerationwas given to local structure shownon shown on publishedmine and district maps n preparing Column 5, but many bounding aults shown

per deposithost deposithost rocks s shown o be almost otally passive. This This passivitysuggests passivitysuggestshat hat replacement, stoping,and stoping, and assimilationwere more importantproimportantprocesseshan cesses han shouldering sideor sideor other manifestations of forceful intrusion,and intrusion,and it also suggestshe suggestshe likelihood hat both lateral and verticalpetrologic verticalpetrologic oning might be more common han has been recognized. Comparison f Column8 with Columns Columns41 41 and 42, the latter reporting brecciation nd shatteringspeshatteringspecificallywithin cifically within the orebodies,eveals orebodies,eveals hat brecciation or shatteringare shatteringare associatedwith ore deposition n every porphyrydeposit, porphyrydeposit,even even where emplacement f the host stocks s passive. passiv e. This disparity suggests that brecciation nd shattering shat tering re themselves passive," and that they can commonly e expected o

on thesemaps thesemapsare are of postoreage postoreage or of multiple age be "blind," as they are at many southwestern southwestern orth Americanporphyry porphyrydeposits deposits nd prospects.Forceprospects.Forcesuch hat their preore importance annotbe annotbe deter- American intrusionand active, even even explosivebrecciation mined.Greatereliance Greatereliance as hereforelaced hereforelaced pon ful intrusionand as at Toquepala Toquepalaand and Braden are apparentlyrare. apparentlyrare. direct text statementshan upon maps. Several Extensivemagmatic magmaticstoplng, stoplng, ssimilation, nd metaauthorscomment hat the specifics f controlling controlling Extensive ppearmechanically lly nd kinetically nconstructureswere obliteratedby the intrusionswhich somatism ppearmechanica sistent with extremely shallow shallow emplacement, ut they guided. moderatelyshallow shallowenvironments environmentsmay be indicated. Shapeand Shape andSize (Columns6 and 7).--The shapes moderately Porphyry molybdenum epositsseem epositsseem to show of intrusions (Column 6), like determinations f emplacementhan do portheir size (Column 7), are difficult to establish more evidenceof forcefulemplacement coppersn general. This evidence onsists f meaningfully,since meaningfully, sinceboth both have been affectedby affectedby in- phyrycoppersn ring and radial dikes and doming of the layered ternal and externalvariables. externalvariables. Exposureof Exposureof a pluton is certainlyaffectedby affectedby original depth and by post- rocks which sometimes verlie the deposits. Stock-Dike (Column 9).--Column 9 indicates intrusion ectonic nd erosional istory. The Boulder that stocks and stocks with subordinate associated batholithhas batholith has beenexposed or tens of miles, and a

large southernArizona batholith(Ettlinger, 1928) posits dikes are typical typi cal of porphyrycopper porphyry copperdedehanfar aremore dikes, dikes,dike dike swarms, r breccias lone. has been inferred from the distributionof distributionof cupolas. indicatedn Column6 Column6 The shape nd sizeof sizeof porphyryhost ntrusions eem This same dationshipwas indicatedn

 

ALTERATION-MINERALIZATI ALTERATION-M INERALIZATION ON

ZONING IN PORPHYRY ORE DEPOSITS

399

b e considered elow. Dioritic rockscommonly rockscommonly where porphyry deposits depositswere shownto shownto be equi- will be than tabular or llinear inear occur at intrusionmargins, intrusionmargins,as as at Ajo and Mineral bodies. Twenty-fourof Twenty-fourof the 27 depositsnvolve depositsnvolve m- Park, with progressively ore K-feldspathic ocks relationshipnot apparent apparen t in the table. portant stockdevelopment nd a high ratio of stock inward, a relationshipnot to dike forms. This distribution s consistentwith with apparent elsicSequenceof Intrusions and Rock Types MineralMineral- component nrichment ccompanying ccompan yingotassic otassic lterportions of some porphyry ized (Columns10 (Columns10 and //).--The sequences f in- ation near the central portions trusion shown n Column 10 reinforceearly reinforceearly observa- copperdeposits. tions (Buddington,1933) (Buddington,1933) of the association f copOrebody (Columns12-19) (Columns12-19) per deposits ith intermediateo intermediateo ffelsic elsic gneous ocks. Except for generally late diabase diabasedikes, dikes, no rocks Outward Shape (Column /2).--The porphyry more mafic than diorite occur in the intrusions ascopperdepositslmost ll havecircular havecircularor or ovalcross sociatedwith porphyrycopperdeposits. copperdeposits. Granodi- sections. sections.At At least our deposits aveclearly aveclearlydefined defined orite and quartz monzonite monzoniteand and their aphaniticand aphaniticand low-grade low-gradecenters centersproducing producinga a ringlike orebody n hypabyssalequivalents hypabyssal equivalentsoccur occur in almost all of the plan. The vertical dimensionsof hypogeneminhypogeneminporphyry copperdeposits, copperdeposits,with with more felsicvariants eralization n most depositsare unknown; however, however, common to the porphyry molybdenumdeposits. molybdenumdeposits. the tabulatedhypogene tabulatedhypogenemineral bodiesseem bodiesseem o fall Most papers consulted n preparing Table 1 give into three general configurations. specificsequences specific sequences f intrusive events and igneous 1. Seventeendeposits Seventeendepositshave have a steep-walledcylinsteep-walledcylinrock compositions,ut compositions,ut uncertain ield relationships drical shape. Two deposits Cananeaand Cananeaand Toquecoupledwith paucityof paucityof radiometric ge determinadetermina- pala) approximately oincidewith brecciapipes. brecciapipes. tions seldom seldom ermit unequivocal unequivocaldentification dentificationf the 2. Sevendeposits Sevendepositshave stubbycylindrical stubbycylindricalor or flat, beginning nd endingof endingof the magmatic pisodehat conical orms,as orms,as do all three of the porphyry po rphyrymolybmolybinvolved ore mineralization. Much older and much denurndeposits. denurn deposits. younger ocks,as ocks,as describedn describedn the appropriate efer3. Three deposits Inspiration,Ely, Inspiration, Ely, and Safford) ences, are excluded. Column 11 shows that all of have a gently dipping, abular shape,perhaps perhaps eprethe intrusive rocks of Column 10 are mine mineralized ralized sentinga senting a depositsimilar depositsimilar to (2) followinga preore in 22 of the 27 depositsabulated depositsabulated nd the youngest youngest structure r postore isplacement,r isplacement,r theymay repreintrusiveunit intrusive unit is mineralized n 2 of the remaining5. remaining5. sent a separate type. Columns 10 and an d 11 show that the sequences sequences Boundaries Column13).--In all of the deposits generally from dioritic to monzonitic ocks, com- studied, he orebodyboundariesre at least in part monly with late latitic to rhyoliticor "quartz por- gradationalor or "assaywall" "assaywall" boundaries. All have phyry" intrusions. Typically, all of theseare theseare min- been ntersected y a postoreerosionsurface.Eleven eralized, showing hat mineralization ither accom- are boundedby boundedby at least one postore fault. Two panied or briefly succeededhe emplacement f in- coincideclosely closelywith with brecciapipes brecciapipeswhich are preore trusiverocks. The associationf porphyrycopper porphyrycopper or contemporaneous ith ore, and one deposit depositswith intermediate lutonic ocks s impres- (Braden) forms a crude cylindricalshell cylindricalshell surrounddimensional to t o oval rather

sive but not as consistent as the association with

porphyry n all 27 districts isted. There has been discussionn discussion n recent years as to whether the name "porphyrycopper" "porphyry copper" s appropriateor the group of deposits escribedn escribedn this paper. paper. The writers believe that this associations genetic ather than coincidentaland incidental and feel that "porphyrycopper" is an excellentdescriptive excellent descriptivename for this unique and important group of ore deposits. The lamprophyreor lamprophyreor "late diabase"event diabase"event is less commonn common n the porphyry oppershan oppershanhasbeen hasbeenprepreviouslythought (Spurr, 1925). Late diabasehas been reported in only 5 of the 27 districts. The general trend, clearly, is from dioritic plutonic toward more felsic hypabyssalocks with all rock types usuallymineralized. usuallymineralized. The degree o which the

ing a postorebreccia postorebrecciapipe. pipe.

Percent in I#neous Host and Preore Preore Rocks

(Columns14 and 15).--In severaldeposits, deposits,100 100 percentof percent of the ore mineralizations mineralizations in igneoushost rocks (Butte, CastleDome, Copper Cities, Endak Endako, o, and Mineral Park). All containsomeore someore in igneous host rocks, but most ore at Bisbee, Braden, Mis-

sion, and Ray is in wall rocks. Somethingike Somethingike 30 percentof all ore mineralizationassociated ith porpercentof phyriesoccurs phyries occurs n wall rocks,again rocks,againsuggestingupola or at least high-levelenvironment high-levelenvironment or the porphyry deposition. DimensionsColumn Dimensions Column16) 16) .--Horizontal dimensions of the tabulateddeposits tabulateddeposits ange from 250 x 1,200

feet for the La Colorada ipeat Cananeao Cananeao 6,000x 13,000feet for the Morenci deposit. Fringes of the

shift from dioritic throughgranodioritic o monzo- difficult-to-limitButte difficult-to-limitButte district may may reach to dimennitic rocks may reflect K-feldspar K-feldspar enrichmentby sions sionson on the order of 20,000 x 50,000feet (only the meansof potassicalteration potassicalteration (Peters et al., 1966) "porphyry "porphyryequivalent" equivalent" or Butte is cited in Column

 

400

]. D. LOWELL AND J. M. GUILBERT

16). The averagedepositsize deducedrom deducedrom pub- genesilicate genesilicatealterationphases. Nonetheless,uperNonetheless,uperlisheddescriptionsnd lisheddescriptions nd maps s a perhapssurpris- genesericitehas sericitehas beenreported. Supergene ffects ingly small 3,500 3,500 x 5,000 feet. feet. havebeen have beeneliminated eliminated rom Table 1 whereveroriginal whereveroriginal Total Ore Tonnageand Tonnageand Grade Grad e (Columns 17, 18, authors rovided escriptionshich escriptionshichwould wouldpermit permit t. and 19.)--Of the 27 depositsabulated, depositsabulated, 3 are estiKnown Extent BeyondOre BeyondOre (Column20).--Colmatedto containover containover 500,000,000 ons of ore, 6 fall umn 20 records the stated or mapped extent of between 100,000,000 100,000,000 and 500,000,000 tons, and 8 alteration eyondhe outerboundary outerboundary f the orebody distances tances are somewhat unc uncertain ertain since contain ess than 100,000,000 100,0 00,000 ons. These tonnage itself. These dis estimates ustbe considerednly considerednly approximate. differentobservers different observers rew the outer out er line on differing Included in these figures are several deposits criteria. External alteration is narrow around the whoseore grade dependson secondary halcocite Bethlehem, .C., deposit, characteristicf characteristicf many enrichment.Averagegrade Averagegradeof of copperore copperore is 0.80% of the Canadianporphyry porphyrydeposits. deposits. Other Other deposits Cu, and averagegrade averagegrade of hypogenemineralization, show alteration extending housands ho usands f feet, averwhere this information is available, s 0.45% Cu. aging approximately ,500 feet. The higher numTwelve copperdeposits copperdeposits ontainat ontainat least 0.5% Cu in bers probably representmerging of hydrothermal hypogenemineralization hypogene mineralizationand and 10 contain less than with low-rankregional low-rankregionalmetamorphic metamorphicffects, he two 0.5% Cu. Molybdenumdeposits Molybdenumdepositsaverage average0.17% being distinguishedonly with difficulty. SignifiMo in grade. cantly,detectable cantly, detectablelteration lteration xtendsaterally xtendsaterallyan an average of half a mile beyond he orebodies, erhaps erhaps Hypogene dlteration Columns20-27) Columns20-27) more, since some authors drew the outer limit on The next three sections,Hypogene sections,Hypogene Alteration the basisof basisof "bleaching" nd the presence f sericite, (Columns20 (Columns 20 through27), through27), HypogeneMineralization HypogeneMineralization phenomena hat probably do not n ot mark the true (Columns28 through 35), and Occurrenceof Sul- outer limit.

fides (Columns36 (Columns36 through42), have parallel or-

PeripheralZone Peripheral Zone (Column 21) .--Alteration is deganizationso that the columnsfor each zone in a scribed n this zone for only five d deposits. eposits. It is given deposithave denticalheadings. headings. For example, generally generallyalong alongwell-developed well-developed tructures nd is selthe innermost alteration zone at San Manual-Kaladom well describedwith respect o associated minmazoo consistsof consistsof quartz, K-feldspar, biotite, and eralization. Where alteration mineralogy s given minoranhydrite Column25), Column25), andthe ore minerals it is of mixed affinity, dominantly dominantlypropylitic, propylitic, with sericitementioned mentioned t Questa. Skarn is described describedn n (with amounts) are pyrite, chalcopyrite, chalcopyrite,molybmolyb- sericite denite, and trace bornite (Column 32). The sul- this zone at Morenci and Santa Rita. Skarn or fides occur more commonlyas commonlyas disseminationshan tactite developments developments not as well reported n the as veinlets (Column (Column 40). literature as are hydrous silicate alteration assemIt should be restated here that the table is bas based ed blages. It is well known known that skarn zonesproject zonesproject apparentlydistort more normal no rmal zoning reas completely s possibleupon publisheddescrippublisheddescrip- into and apparentlydistort tions, and these are hardly uniform in approach, lationships,nd that many porphyry porphyrydepositsmight describedas contact-meta contact-metamorphic morphic eposits. eposits. detail,or detail, or even erminology.Several erminology.Severaldeposit deposit escrip- also be describedas apparentlypersist persistto the centersof centersof tions were based on temporal rather than t han spatial Skarn can also apparently relationships; relationships;hese hesedeposits depositswere enteredas enteredas earliest equals nnermost,and nnermost,and so on outward. Several deposit descriptionsnvolved descriptionsnvolved separateand separateand poorly related descriptions f alteration, mineralization,and mineralization,and occurrence. We have made every effort to match appropriatespatial appropriate spatial and mineralogicaldata. data. Question marks in the table generally generallydenote denoteuncertainty uncertainty of placementof placementof the information rather than uncertainty in the data.

orebodies.

Outer Zone (Column22).--Mineralogic 22).--Mineralogic notation is given for 20 of the 27 deposits, dep osits,with with "propylitic" citedfor Ely, Nevada. Of these,18 these,18 includechlorite, includechlorite, 17 epidote, and 13 a carbonate (calcite in 11). Quartz is cited 7 times,sericite6, sericite6, zoisite-clinozoi zoisite-clinozoisite site 5, kaolin 3, specularite2, specularite2, montmorillonite2, montmorillonite2, and albite,hematite, albite, hematite,magnetite,ourmaline, magnetite,ourmaline, nd ruffle(?) once each. By far the most commonassemblage commonassemblages

The problemof distinguishingetween distinguishingetween upergene chlorite-epido chlorite-epidote--calcite. te--calcite.ention s seldommade madeof of and hypogene ffects s important. Hemley and the replacedminerals, minerals,but but the chief onesare onesare amphiJones 1964) curves ndicatesericite ndicatesericitestability stabilityonly only bole, bole,biotite, biotite,and and plagioclaseFig. plagioclaseFig. 12). This assemat moderately igh K+/H + ratios at low tempera- blagehasaffectedby affectedby far the largest largestvolume volumeof rock. tures, an environment onsistentwith with (but not re- The chlorite-epidote-calciteropylitic chlorite-epidote-calciteropyliticassemblage assemblages quiring) high pH. The extremdy low pH pre- always alwaysoutside outside he ore zone and beyond he phyllic p hyllic and argillic zoneswhere zones where these theseare present. Sericite sumed activesupergene activesupergene nrichmen nrichment t onesargues againstor mportant mportantdevelopment development f supergene sup ergene ericite is commonly eported even inare outermostalteration outermost alteration and indicate he kaolinminerals o be stablesuperstablesuper- assemblages.Whether Whether this mineral varies import-

 

ALTERATION-MINERALIZATION ONING N PORPHYRYORE PORPHYRYORE DEPOSITS

40i

Innermost Zone (Column 25).--This column is antly in composition,nd composition,nd hencen stability ield and surprisingof of the hypogenealterdistribution, s yet to be shown. It has been ob- perhaps he most surprising Potassicalteration, though relaserved,however, in amountsranging amountsranging from from trace to ation data block. Potassicalteration, tively subordinate subordinaten n the literature,occursat mostof moderate, nd chiefly replacingplagioclase, replacingplagioclase,n some porphyrydeposits s eitheran early or an innerouterzonesnot zonesnot reported n Table 1. The distribu- the porphyrydeposits reportedas simple tion with respecto respecto vertical oningwill oningwill be discussedmost assemblager both. It is reportedas below. quartz, K-feldspar,and K-feldspar,and biotite(?) only at Endako; K-feldspar,biotite,and and sericiteat sericiteat 7 deIntermediate Zone (Column 23).--This column as quartz, K-feldspar,biotite, posits,and and as quartz, qu artz, K-feldspar,biotite K-feldspar,biotite with chlordescribesredominantlyrgillic redominantlyrgillicassemblages. assemblages. ilici- posits, fluorite, anhydrite, anhydrite, or tourmaline at 8 fication is clearly more important here than in the ite, albite, fluorite, K-feldspar,and sericiteare reported outer zone, and the dominant minerals are quartz, more. Quartz, K-feldspar,and K-feldsparockaolin, montmorillonite, montmorillonite,and sericite. Argillic as- at Silver Bell, and quartzwith only K-feldsparoccurs at Mineral Park and Questa. Quartz, phlogosemblagesre semblages re discerniblen discerniblen 22 of the 27 deposits, tourmalineoccurat at Cananea,but but the zone if quartz-sericite-kaolinite4 quartz-sericite-kaolinite4 occurrences) e in- pite, and tourmalineoccur sericite,biobiocluded as argillic. Quartz is cited first in most may not be innermost here. Quartz, sericite, tite, and anhydriteoccur anhydrite occurat at Braden. Anhydrite at assemblages. aolin is citedsinglyor singlyor beforemontbeforemontparenthesesn Table 1 morillonite in 17 of the 22 assemblage assemblages sor which several ocales s given in parenthesesn hasnot beendescribed beendescribedn print. Specimens dataare data are given. Three deposits ave avemontmorillonite where t hasnot of anhydrite rom Esperanza,Questa,San Esperanza,Questa, San Manuelzonallybeyondkaolin, beyondkaolin, and 7 involvesericite. No Kalamazoo, and Santa Rita have been observed to argillicassemblages reported n 5 deposits. Inner Zone (Column 24).--Most of the quartz- swell the publishedoccurrences t Butte, E1 SalAjo, and Braden. sericite (and pyrite) assemblages,he he chief ore vador, Toquepala,Ajo, The commonoccurrence f anhydrite n the pobearersof the porphyrycopper porphyrycopperdeposits, deposits,all all in this tassiczone zone indicates hat (1) redox potentialsare potentialsare inner zone column. The zone is reported r eportedunequiunequi- tassic vocallyto have a pervasivequartz-sericite pervasivequartz-sericite ssem- considerablyhigher in the late magrnatic-deuteric the prevalence f unoxidized ulfur speblageat blage at 19 porphyrydistricts, porphyrydistricts, quartz-majorseriquartz-majorseri- fluids han the cies would indicate; (2) a high percentage f the cite-minorK-feldspar rray at 3 more,and more,anda quartzporphyrysystemmay be present major sericite-minorkaolin sericite-minorkaolin assemblage t 3 more. total sulfur n the porphyrysystem ( 3) high-temperature ydrothermal At Braden a quartz-sericite-biotite-anhydrite quartz-sericite-biotite-an hydrite nner- as sulfate; and (3) nnerreactions involving silicates, oxides, and sulfides zone assemblagerades assemblagerades nto strongersecondary strongersecondary iotite in the innermostzone. innermostzone. Only at Esperanza s must concern hemselveswith equilibria involving a quartz-K-feldspar quartz-K-feldspar air reported onallyoutside onallyoutsideof higher total sulfur than the net sulfide contents an unusual quartz-K-feldspar-biotite assemblage. would indicate. It is also noteworthy hat the conclusionof of Lutton (1959) concerningdepositional Creasey (1966) indicates hat K-feldspar can be clusion pegrnatoidnto "porphyry"condi"porphyry"condipart of his quartz-muscovite ssemblageound ssemblageound at continuum rom pegrnatoidnto tions are supported nd that the elementsgrouped Bagdad, Bingham, Bingham, and Chuquicamata. Creasey ormers"of high states 1966, p. 62) "quartz-sericite-pyritewithout by Ringwood 1955) as "complex ormers"of ionic potential are precisely hose found in major either a clay mineral or K-feldspar associateds associateds a commonassemblagehat doesnot doesnot fit into any of the and trace minerals n the porphyry p orphyry base-metaldedeposits,especially especiallyn n the potassic lterationzone. lterationzone. three previouslydescribed previouslydescribed lterationtypes. If clay posits, Other characteristicsof the potassiczone are were present [as at Endako, Inspiration, Inspiration, and Mission-Pima,where sion-Pima, wherekaolin s reported], he assemblage assemblage briefly described y Meyer and Hemley (1963) and Guilbertand and Lowell (1968). Ore commonly ccurs wouldbelong would belong o the argillic alteration,and and if K-feld- Guilbert at the interface interfacebetween betweenpotassic potassicand phyllic alteralterspar were present [as at Bagdad, Bingham, and generallycentral Chuquicamata], t would belong to the potassic." ation zones. The potassic one is generallycentral discernible,t is Since he assemblageppears y far mostcommonly mostcommonly or deepest, r if a time sequences discernible,t earliest. as quartz-sericite-py quartz-sericite-pyrite, rite,he he term "phyllic" s herein Zoning Sequencerom Sequencerom Center and Bottom (Colurged as a specific erm. Advanced Advancedargillic argillic alterumns26 umns 26 and27).---The and27).---The upwardzoning upwardzoningand outward ation, involving chiefly pyrophyllite, pyrophyllite,dickite, dickite, and zoningof zoning of alteration alteration ssemblagesre seldom eported topaz (Meyer and an d Hemley, 1968), is associated ith as such,but such,but their systematic ntry by by description r phyllic assemblages assemblagest Butte and Bisbee. It is not from map or diagram evealsa evealsa significant equence. reportedelsewhere reported elsewhere ut may have escaped etection. Seven,possibly Seven, possiblyeight eight (the positionof positionof phyllic alat E1 Salvador is uncertain), of the deTheexposedalteration phyllicassemblagef phyllicassemblage f Column24 Column24 innermost exposed alterationassemblage assemblage n is at the least six teration positsshow posits showalterationassemblages alterationassemblagesn the sameoutsameoutdistricts. ward sequence: otassic,phyllic, phyllic, argillic, and pro-

 

402

1. D. LOWELL AND ]. M. GUiLBERT

pylitic. Even where wherecertain certainassemblages assemblages re not rere ported,the remainingassemblages all in the same all order. Two deposits,possibly possibly hree, show only potassic nd phyllic zones, our lack only argillic, and six start with phyllic and includeargillic includeargillic and propylitic. For a few depositshe depositshe sequences un-

Outer Alteration Zone (Column (Colu mn29).--This zone generally corresponds o the propylitic alteration zone, and mineralization s generally restricted o pyrite, although sparse chalcopyrite s generally present along with variable amounts of bornite, molybdenite,magnetite, magnetite,specularite, specularite, hodochrosite, hodochrosite, known. sphalerite, alena,and alena,and rhodonite. Intermediate Alteration Zone (Column 30).-Vertical sequence f zonation s generallymuch generallymuch correspondsoughly to the argillic alteration less well known, so so assignmentsan assignmentsan be made in This correspondsoughly zone,and and the bulk of mineralizations mineralizations usuallypyrite usuallypyrite Column27 onlyfor Butte, Climax,E1 Climax,E1 Salvador, nd zone, with high highpyrite-to-chalcopyrite pyrite-to-chalcopyrite atioswhich atios whichaverage average San Manuel-Kalamazoo. Manuel-Kalamazoo.Except Except for uncertainty t E1 Salvador, the order is consistent with lateral 23:1 in deposits or which figures are available. Variableamounts amounts f bornite,molybdenite, bornite,molybdenite,ennantite, ennantite, zoning. Outwardand Outwardand upwardzoning upwardzoningof of the 27 de- Variable sphalerite, alena, alena,enargite, enargite, c chalcocite, halcocite, nd huebnerposits s mostconsistent mostconsistent ith the sequencef sequencef potasite have been found in this zone. HypogeneoreHypogeneoresic,phyllic, sic, phyllic, rgillic, ndpropylitic ndpropylitic ssemblages. grademineralization mineralization may overlap nto this zone,but may zone,but An alterationassemblage alterationassemblageas as beennoted n sev- grade generally his zone s outside he orebody. eral localitieswhichconsists f K-feldspar,biotite, biotite, Inner Alteration Zone (Column 31).--This zone coarsesericite,chlorite,and chlorite,and albite,accompaniedy commonly orrespondso the phyllic alteration alterationzone zone moderate pyrite and chalcopyritemineralization. chalcopyritemineralization. typicallycontains bundant yrite and high high total total This groupdoes groupdoesnot readily it the classification classificationutut- andtypicallycontains sulfidesogether ogetherwith with pervasive ericitization. ericitization.Pyrite Pyrite lined n Table 1, nor do the depositsenerally each sulfides content s not reported reportedquantitatively quantitatively or most deore grade. grade. The writersare of the opinion hat this by represents deepassemblage hose elationshipo elationshipo positsbut it appearso average bout10 percentby exthe main porphyrysystem porphyrysystem asnot asnot beenexposed beenexposedor or weightfor the 27 deposits, r about16 percent,exporphyrymolybdenumroup, roup,which whichare are study because f the geometryand geometryand large vertical cluding he porphyrymolybdenum dimensions involved. relatively low in pyrite. Pyrite-to-chalcopyrite ratiosaverage ratios average12.5:1. 12.5:1. This zonecommonly zonecommonly onstitutes the ore zone, especiallyn especially n those depositsn HypogeneMineralization Columns Columns 8-35) which

chatcocite enrichment

has occurred.

The

As has long been beenknown, known,hypogene hypogene ulfide-oxide principal principal"ore" "ore" mineral s pyrite, whichoccurswith mineralassemblagesre closely elated n time and chalcopyrite mineralassemblages chalcopyrite,, olybdenite,nd ndvariable ut generally spacewith silicate lterationmineral mineralassemblages assemblages n small amounts of bornite, chalcocite,sphalerite, sphalerite, porphyrydeposits. porphyry deposits. The designation f pyrite and enargite, enargite,and and magnetite. magnetite as ore minerals rather than alteration Innermost lteration one (Column 2).roThis minerals, or example,appears appears o be largely arbi- zone s generallyequivalent generallyequivalento o the potassic lteration trary. zone and is usually he central zone. Total sulfide In Table 1, sulfide-oxide ineralassemblages assemblagesave ave content s low to moderatewith an averagepyrite averagepyrite been described in Columns 28-35 with reference to content of about one percentand a pyrite-to-chalthe same alteration zones a as s are described in Colcopyrite atio of 3:1 in the depositsabulated. depositsabulated. This umns20-27. umns 20-27. The consistentequence consistentequencehrough hrougheach each zone zonemay may reachore reachore gradeand gradeand probablyaccounts probablyaccountsor or zone and from one assemblageo another outward most ore in solelyhypogene solelyhypogene re deposits. It also from the center s again significant. forms he "low-grade enter" n five deposits.The deposits.The PeripheralAlteration Peripheral Alteration Zone (Column 28).roThis sulfide sulfidemineral mineral assemblages chalcopyrite, yrite, column describes metal occurrence occurrences s that that form a disand molybdenite. continuousing normallynear normallynear the outer edgeof edgeof the Overall Abundance ol Major Ore Minerals propyliticzone. propylitic zone. The depositsend to be small to (Column 33).•In the porphyry coppers,pyrite pyrite is mediumsize, although arge lead-zincdeposits lead-zincdepositswith by far the most commonsulfide, commonsulfide, ollowed n order or without preciousmetals preciousmetals occur in this zone at by chalcopyrite, ornite, enargite,and enargite,and molybdenite. Santa Rita, Bingham, and Butte. At least minor Molybdenite s present n all 27 deposit deposits, s, fact not peripheralmineralization peripheral mineralizations s found n all 27 deposits previouslyecognized. studied. Arcuateclusters Arcuateclusters f minesor minesor prospectsurprospectsurZoning Sequencerom Sequencerom Center (Column 34) and round 23 deposits. Minerals common n this zone fromBottom Column35).•Grading Column35).•Grading outward rom are sphalerite, alena,silver, alena,silver,chalcopyrite, chalcopyrite,old,and the centerof centerof the deposit, he typical ateral mineralization sequence ppears o be the assemblages1) assemblages1) pyrite, andetrahedrite,barite, less commonly,specularite, commonly, specularite, enargite, enargite, famatinite, etrahedrite, barite, various sulfosalts, sulfosalts, nd chalcopyrite, chalcopyrite,yrite, yrite,bornite, bornite,molybdenite; molybdenite; 2) pyrite, manganese nd vanadiumminerals. chalcopyrite, olybdenite, ornite; (3) pyrite, chal-

 

,4LTERATION-MINERALIZATION ONING N PORPHYRY RE REDEPOSITS DEPOSITS

403

copyrite; and (4) sphalerite,galena, galena, silver, silver, gold. itic alteration. Crackle texture is often less distinct center,particularlyff a potassic lteration Apparentreversalswere reversalswere noted in only three camps. near the center,particularly Information as to vertical zoning is extremely zone is present. limited. Most deposits ave beenexplored beenexploredby by mine Supergene ulfides Column43) Column43) openingsor openings or drill holes only to depths which are shallowas shallow as comparedwith the probableoriginal probableoriginalverTwenty-threeeposits Twenty-three epositsontain upergeneulfides, tical dimensions.

Tentative

evidence from

13 de-

and secondarynrichment secondarynrichment as required required o reach marginalore ore grade n 10. Supergene Supergenehalcocite halcocite molybdenite ssemblage radesupward rades upward intoeported pyrite. (and (andprobably probablylso lsosecondaryigenitenddjurleite) nddjurleite) An apparent eversalof eversal of this order hasbeen positssuggests posits suggestshat hat typicallya typicallya pyrite-chalcopyritein two deposits.

Occurrence l Sulfides(Columns36-42) (Columns36-42)

Hypogenesulfides Hypogene sulfides n porphyry deposits ypically form veinlets or disseminated rains. This habit is probably elatedto the fact that that cracklebrecciation cracklebrecciation is present p resent hroughout he volumeof volumeof mineralization. Broadly, he porphyries eem o be masses f homogeneous ock penetratedby reticulate racturesand racturesand mineralizedby fluids which soaked he mass massrather rather than beingconstricted beingconstrictedo tabularmasses tabularmasses r replacements.

is presentwherever wherever econdaryulfides ccurand ccurand alwaysconstitutes always constituteshe chief enrichment mineral. Covellite s reported n 12 deposits, enerallyow enerallyow

in the enrichment blanket.

Porphyry Deposit Genesis The data of Table 1 and the inferences drawn

from them, from the field, and from the detailed geologyof geology of the San Manuel-Kalamazoo eposit epositap-

pear to support he orthomagmatic odeldescribed odeldescribed earlier, although he nature of the data and the scale actorsare actorsare not suchthat suchthat the problemscan problemscan be conclusivelyesolved. The formationalmodelwhich modelwhich

Occurrence f Sulfidesby Sulfidesby Zones (Columns (Columns3636most generally generallyapplicable smany oneyears of a ago dif40) .--A progressive radation n sulfidedistribution sulfidedistribution appears ferentiationcontinuum ferentiation continuumas asapplicables suggested is noted in almost every deposit deposit abulated. This by W. H. Emmons (1933) in his descriptionof sequenceprogresses rom veins in the peripheral cupola ormation. ormation. Near-surfacentrusion Near-surfacentrusionof a melt zone o veinlets n the outer zone,veinlets zone,veinletsand and minor which whichproduces producesocks ocksof of intermediate ranitoid ranitoidcomdisseminatedrains disseminated rains in the intermediate one, one,veinvein- position s either a passive ntrusion as at Butte, lets approximately qual to disseminations n the Santa Rita, and Ajo, or a dike swarm swarm as at San inner zone, and predominantdisseminations predominantdisseminationsn the Manuel-Kalamazoo nd Safford. Response f wall innermost one. The tendency or the t he increasing rocks o this intrusiondepends pon their composi-

importance f dissemination owards he core may tion, their structural fabric, and the nature of the owards

result from metasomatismr metasomatismr recrystallization recrys tallization f the intrusive melt. Cooling begins from the surface rockandhealingof veinlets. The absencef promi- downward, downward,and and gentle thermal gradients gradientsare are estabnentveins nent veins n mostalteration mostalterationonesmay ndicatehat ndicatehat lishedfrom higher temperatures t depth to slightly a crackle recciationone recciationonebehaves behaves san incompetent lower ones nearer to the ssurface urface and outward. Minmasswhich mass which can not support hrough-goingissures eralization and alteration chemistries are established and veins.

respect o thesegradients, these gradients, hemistries hemistrieshat hat reBrecciaPipes and CrackleZones BrecciaPipes CrackleZones (Columns41 (Columns41 with flectessentially euteric o late magmatic onditions, and 42).--Breccia pipesare pipesare present n 20 and are with potassicalteration potassicalteration yielding upward and outmineralizedn 18 deposits. deposits.Toquepala Toquepala nd Cananea ward through the phyllic zones (or the "zone of are mineralized recciapipes n whichore whichore limits are feldspar destruction," Robertson, 1962) into the nearly coextensive ith the pipes. Toquepala, Toquepala,n n zones of more typical hydrothermalalteration reparticular,shows particular, showsevidence evidencehat hat the surrounding l- sponses. These gentle gradients presumablyhave presumablyhave terationzones teration zoneshave havebeen been elescopednto a relatively a direct bearing bearing on the large dimensionsof dimensionsof the thin halo,and halo,and alteration ssemblagesithin the ore- porphyries porphyriesand and the coarselygradational coarselygradationalalterationalterationbody' verlap. ve rlap. The Bradenorebody Bradenorebody pparently on- mineralizationboundarieswhich they show. sistsof a verticalcylindrical verticalcylindrical epositwhichhas whichhasbeen been We thus reaffirm on the th e basis of the published publis hed penetratedlong penetrated long ts verticalaxis verticalaxisby a postore reccia record that the porphyry copper depositsare depositsare the

pipe.

results of a physical-geochemical physical-geochemicalontinuum ontinuum from A well-developedrackle well-developedracklezone zone is present n 26 low-temperaturemagmatic o "conventional" "conventional" ydrodeposits ut is largely absent n the skarn ska rn of the thermal conditions. The gradientsare gradientsare reachedas reachedas a

result of cooling in an onal intrusive mass,interfaces and the Mission-Pima rebody. Crackle zones are usually circular n outline and are always arger than the alteration-mineralization boundary orebodies,ypically ypicallyadingout adingout in the t he zoneof zoneof propyl- appear to have been established s standing orms

 

404

.r. D. LOWELL AND J. M. GUILBERT

rather than as upward and outward advancing advancingmega envelopes. Application of the Hemley-Jones Hemley-Jonesmodel model of potassiumsilicate potassiumsilicate stabilities stabilities and alteration, as modified by Fournier (1967) and Meyer and Hemley (1968), permits passage rom essentially magmaticconditions magmatic conditionsat depth to areas of higher hydrogen on concentration co ncentration nd lower K+/H + and lower temperatures ither with time at a given point

surfaces or several porphyry copper depositsare depositsare shown n Figure 13. Morenci is placed placedhigh high in the hypotheticalvertical hypothetical vertical section becauseof becauseof the wide exposureof exposure of the phyllic zone without exposureof exposureof potassicassemblages. potassic assemblages. Several aspects aspectsof of Morenci geologymbreccia geologymbrecc ia ones, the broad-scalealteration broad-scalealteration symmetry,and the occurrenceand distributionof sulfides•suggestt hat potassic lterationwill sulfides•sugges lterationwill be en-

depth under thethat existing open pit. deep in the system or through space upward and countered It is alsotnoteworthyhere noteworthy here phyllic zone alteroutward at asystemor given time. It is spaceupward important o note, however, that an inner inne r zone need not have been ation assemblages,ith assemblages,ith their high pyrite content contentand and microveinlets,are precededby the mineralogyand mineralogyand assemblagesf assemblagesf an their profusion of veinlets and microveinlets, responsibleor the extensive extensivedevelopment f outer zone in a systemof systemof decline,of decline,of loweringtem- chieflyresponsibleor

supergeneoxidation, leaching, and enrichment of supergeneoxidation, southwesternNorth American deposits. This high exposureappears o be the most common, may well dictate whether copper or molybdenum level of exposureappears supergene-enrichedeposits. eposits. predominatesn predominates n the ultimate deposit,molybdenite deposit,molybdenite especially n supergene-enriched tending to be associatedwith more silicic variants. Recentpublications Recent publications n the Chino deposit t Santa Rita, New Mexico, show hat an island of low-grade Conclusions material is being left in the center of the northern portion of the pit area. This island of low grade The foregoing summary forcefully demonstrates is symmetrical symmetrically ly nd centrally disposedwith respect that the th e porphyry copper-molybdenumeposits is- to secondary -feldspar,chalcopyrite, chalcopyrite, ndpyrite display importantunifying geologiccharacteristics geologiccharacteristicsncluding various lateral and vertical zones. The fact tribution aThis s reportedby reported Nielson (1968, 6, 7, and 9). as "low by grade island" mayFigs. represent of zoning s not new, but several mportantaspects, the croppingout croppingout of a low-gradebarren zone analosuch as sulfide species,detailed species,detailed alteration assem- gousto the central core at San Manuel-Kalamazoo. blages,and blages, and the characteristic ccurrences ccurrencesf the sul- Lastly, Gilluly's (1946 (1946)) descriptionof the Ajo defides, is far more widespreadhan has previously posit involves much the same K-feldspar-biotiteK-feldspar-biotitebeen realized. Indeed, a "typical"porphyry porphyrycopper copper chlorite-sericite chlorite-sericiteand and magnetite-chalcopyrite magnetite-chalcopyritessemdepositcan deposit can be hypothesizedrom hypothesizedrom Table 1 and is blages blagesand and zonal characteristics s those encountered encountered includedalong included along the bottom of the table. at depth in San Manuel-Kalamazoo. Manuel-Kalamazoo. It appears It is especially oteworthy hat many,and many,and perhaps possible, herefore, o assigna assigna third dimension o most, porphyry depositshave depositshave coaxially cylind cylindrical rical at least severaldeposits,and and many others may be alterationzones. alteration zones. Factors hat limit the development assigned assigneddepth depth parametersas parametersas further information of discernible ymmetryn porphyrydeposits porphyrydepositsnclude nclude develops. For example,brecciation example,brecciation nd ring diking the following: may have significancen regard to depth of forma-

peratures, or of shallow upward gradients. Variation

in the

d differentiation ifferentiation

index

of the intrusion

1. Regional or local structural fabric that may produce asymmetry in alteration and mineral ore zones.

tion.

It alsoappears alsoappears ignificant ignificanthat hat the porphyry deposits depositsof of British Columbia (formajor example, the Bethlehemand and Lornex deposits) occur in quartz 2. Heterogeneous nd contrastingcomposition contrastingcomposition f Bethlehem reportedat preore rocks, especially he presenceof sedimentary diorite, and the K-feldspathic ock types reportedat Ajo yield outward to a quartz diorite composition "screens." evidence idence oncerningarge3. Dislocationsof the original geometry geometryby by fault (Wadsworth,1968). The ev scale metasomatismf metasomatism f rocks, rocks,generally generally with attendant displacement displaceme nt r by postore ntrusions. and quartz as described 4. Exposureof Exposureof the porphyry system system aterallyand enrichmentin K-feldspar and at BinghamCanyonby Stringham 1956), may well at depth. prove to be more general han is now realized. The The vertical dimension dimension nterpreted for the San alteration alterationassemblages assemblages,, ineralization haracteristics, and occurrenc occurrence e of sulfides at Bethlehem and Lornex Manuel-Kalamazoosystem Manuel-Kalamazoo system s on the order of 8,00010,000 feet. No definiteevidence definiteevidencesuggests suggestshat hat this are consistent ith deep exposure, nd n d we may see vertical dimension dimension s either typical or normal, but now exposeda exposeda relatively deep-seated orphyry enthe mineral assemblagesypical of different vertical vironment. The fact that thesedeposits thesedeposits lso nvolve zones n San Manuel-Kalamazooappear Manuel-Kalamazooappear to be use- quartz diorites rather than granodiorite granodioriteor or quartz ful in estimating he depth of formation of several monzonites monzonitesmay may be another manifestationof manifestationof the deposits. These "depth levels" levels" o off presentexposure presentexposure vertical dimensionn porphyry depositgenesis. depositgenesis.

 

.dLTERATION-MINERALIZATION ONINGN ONING N PORPHYRYRB PORPHYRYRBDEPOSITS SAN

MANUEL

405

FAULT

KALAMAZOO •1 SAN

EGMENT

MANUEL•

SEGMNT.._•?•

PROPYLITIC • ChlEpiEpi- arb

•

Adul AIb

PHYLLIC ••'--.,.••--,'•-MORENCl, ••'--.,.••--,'•MORENCl, UTTE Ser-py py /

ARGILLIC Q- KoolChl

•

\

\ •• POTASSIC

MINERAL PARK,

SILVER ELL

BINGHAM, SANTA RITA

Q- K- fe•l•- Bi+ser + onh

t t t

ADO,(BETHLEHEM)

ChI-Ser-

Epi-eg eg Fro. 13. Schematic rawing rawingof of San Manuel-Kalamazoo Manuel-Kalamazoo howingexposure howingexposureevels evelsof of several orphyry opper eposits. Other deposits ould be added,but added,but these ew serveto showa vertically developed imension.

A growing body of data indicates hat the porphyry deposit minerals may form at depths as shallowas shallow as 5,000-10,000 5,000-10,000 feet. Facts supporting supporting his conclusionre conclusion re (1) the occurrence f porphyryrocks porphyryrocks in all 27 deposits f Table 1; (2) the cutting of all deposits y postoreerosion postoreerosionsurfaces; surfaces; 3) the widespreadoccurrenceof brecciation even though the host intrusions are usually passively emplaced); (4) the location of 14 deposits n Cretaceousor youngerpreore younger preorerocks rockswhile while the intrusions hemselves hemselves are of late Cretaceous r younger youngerage; age; (5) regional structural-stratigraphiconsiderations; structural-stratigraphic onsiderations; nd (6) the common occurrenceof occurrenceof porphyry-ore-formingenporphyry-ore-formingenvironmentsn cupola-like tocksess han one square

enormous alos of pyrite-sericite-quartz ydrotherydro thermal alteration o "dry" depositswith relatively ow ow sericite-pyrite ontent. Althoughperhaps Althoughperhaps he terms are too casual, "wet" and "dry" refer to the net apparent bundance,nvolvement, nvolvement,nd permeation f a mineralizing-alteringluid. mineralizing-alteringluid. Concentric oning is also present n "dry" deposits, ut it is telescoped laterally into a small fraction of the halo h alo thickness of the "wet" type. The "wet" type is represented by mostof mostof the Southwest eposits,uch eposits,uchas as Bingham and 7Morenci, nd includesmost includesmost of the large porphyry copper deposits. The "dry" type is reprerep resentedby sented by many of the British Columbiadeposits, Columbiadeposits, suchas such as Bethlehem, nd includesmany of the hypo-

mile in area at the ore-forming elevation. ore-grade porphyryeature coppers. Theore-gradeporphyry most distinctive distinctive of the porphyry deDeposits seem o range from "wet" types having gene high pyrite-to-chalcopyrite pyrite-to-chalcopyriteatios and surrounded y posits s simply heir huge size as comparedwith

 

406

.L D. LOWELLAND J'.M. J'.M. GUILBERT

otherhydrothermalre hydrothermalre deposits. ncl ncluding udingore- that the integratedmodel modelof of verticaland verticaland lateral siligrademineralizationndsurroundinglteration nd cate-oxide lteration, ulfidemineralization, mineralization,nd nd sulmineralization,hey mineralization, hey assume imensions ore com- fide occurrenceharacteristics n the t he porphyry emonly ssociatedith stockshan hanwith withoredeposits.positsmay be useful o economiceologists economiceologistsoth oth Thebulk The bulkshape shape f porphyry epositseflectsarge- explorationally explorationallynd nd scientifically. scalestructural ontrolof of mineralizationnd may alsobe related o the originaldepth originaldepthof formation. Flat-tabular, one,and one,and flat-dippingube-type flat-dippingube-type e-

Acknowledgments

The writerswish writerswish o expressheir expressheir appreciationo colleagueswhosediscussion nd compositsmay posits mayheresteep represent shallow depthreof their many colleagues formation here steep elatively nvironmental radients vail. Steep,columnar Steep,columnar eposits ith longvertical ments have contributed o this paper, to L. B. dimensions and little brecciation seem seem to indicate

Gustafson, ames'Gilluly,nd ndT. T. W. Mitcham ho

vironmentalgradients. vironmental gradients.

T. Wolf, and B. Townsend for their assistance n

relativelygreat depthof depthof formation nd gentleengentleen- reviewed he manuscript, nd to H. R. Hauck, M. Brecciapipe Breccia pipe deposits, uch as Toquepala,with with preparing he manuscript nd illustrations.

only thin alteration halos and with evidenceof evidenceof vio-

lent emplacement,re emplacement,re clearly representative representativeff a different enesisn which he mineralizers mineralizers ay have evolved uddenlyn a more or lessopen lessopenvent vent with relativelysteeppressure steeppressuregradients. gradients. Examplesof Examplesof blind mineralized recciapipes pipesat at Cananea, ilares, and elsewhere ndicate, ndicate, however, that mineralized

5211N. ORACX.E,

TucsoN, ARIZONA,

AND

DEPARTMENTFGEOLOGY, DEPARTMENTF UNIVERSITY FARIZONA, FARIZONA, TUCSON,ARIZONA, ARIZONA,

December19, 1969; March 16, 1970

breccia ipesneed ipesneednot not necessarilye necessarilye eitheropen eitheropen o

REFERENCES

the surface deposits r emplacedt emplaced shallow epth. elongate, Anderson, . A., A., 1968,Arizonaand Arizonaand adjacentNew New Mexico, Porphyry endt to have either in Ore O re Deposits f the Unite United d States,1933-1968 1933-1968Gratonvertical,columnarshapes columnarshapes San Manuel-Kalamazoo Manuel-Kalamazoo SalesVolume), John D. Ridge, ed., Vol. 2: New York, and Bingham) or foreshortened olumnar, almost

A.I.M.E., p. 1163-1190.

, Scholz,E. Scholz,E. A., and Strobell,J. Strobell,J. D., Jr., 1955,Geology 1955,Geology discoldshapes Climax or Ray). These shapes and discoldshapes ore deposits f the Bagdad Bagdadarea,' area,'Yavapai Yavapai County, suggest hat migration of hydrothermal luids was Arizona: U.S. Geol. SurveyProf. Paper 278, 1 102 02 p. Banerjee, Banerjee,A. A. K., 1957, 1957,Structure Structureand and petrology petrologyof of the Oracle controlled y nearlyvertical nearlyverticalgradients gradients nd that fluids, granite, P Pinal inal County, Arizona: Unpub. Ph.D. thesis, however derived, migrated upward across arge Univ. of Arizona, Tucson, Arizona.

areas, up to tens of thousandsof feet in diameter. Bauer, H. L., Jr., Breitrick, R. A., Cooper,J. J., and Anderson,J. Anderson, J. A., 1966, Porphyry copperdeposits n the It appears ikely that the mineralizersoriginated originatedas as Robinsonmining district, Nevada, in Geology of the

a separation f fluidsat the point of crystallization PorphyryCopperDeposits, CopperDeposits,Southwestern Southwestern orth America, S. R. Titley and C. L. Hicks (eds.): Tucson,Arizona, Tucson,Arizona, of the "host intrusive body." It shouldbe noted The University of Arizona Press, p. 233-244. that the "overhang"effect "overhang"effect or beet shapeof San Beall, J. V., 1965, Southwest opper--aposition opper--apositionsurvey: survey: Manuel-Kalamazoo Manuel-Kalam azoo

could also be consistent with an

influx of deeplycirculating, deeplycirculating, xternallyderived, xternallyderived,perper-

haps hapscooler water, although othation he depthand depth wall rockscooler nvolved nvolvedmake make his explanation explan eemunlikely. eemand unlikely. Many characteristicsdescribed characteristicsdescribed n Table 1 and systematizedn systematized n Figure 13 are consistentwith one

another.

Variations

in the character

of sulfide oc-

currence, or example, appear best explainedby

considering that dissemination extures are com-

Min. Engr., v. 17, p. 77-92.

Bryant, D. G., 1968, ntrus ntrusive ivebreccias breccias ssociated ith ore, Warren (Bisbee) mining district, Arizona: EcoN. Gvo•.., v. 63, p. 1-12.

, and Metz, H. E., 1966, Geology Geologyand and ore depositsof depositsof the Warren mining district, op. cit. (4): p. 189-204. Buddington,A. A. F., 1933, Correlation of kinds of igneous rocks with kinds of mineralization, n Ore Deposits of the Western States (Lindgren Volume): New York,

A.I.M.E., p. 350-385. Burnham, C. W., 1962, Facies and types of hydrothermal alteration: EcoN. Gv.o•..,v. v. 57, p. 768-784.

, 1967, Hydrothermal fluids at the magmaticstage, magmaticstage, n patible with a model involving crystallizationof Geochemistry of Hydrothermal Ore Deposits, H. L. rock-formingsilicates rock-forming silicates i.e., the potassic one) such Barnes (ed.): New York, Holt, Rinehart and Winston, that the sulfides,whichare whichare really igneous ccessory Inc., p. 166-235. depositsof of the minerals,are are deposited ither as truly included in cludedmin- Carpenter, R. H., 1968, Geology and ore deposits Questamolybdenummine area, Taos Taos County, New Mexerals or in fracturesand fracturesand microfracturesn microfracturesn newly ico, op. cit. (1), Vol. 2: p. 1328-1350. Porphyries, hyries, breccias,and copper mincompetent ocks which are subsequently ealedby CarT, J. M., 1960, Porp

localcrystallization. local crystallization.

eralization n Highland Valley, B.C.: Can. Min. Journal, Nov., p. 71-73.

The San Manuel-Kalamazoo Manuel-Kalamazooeposit eposithus husappears appears ---, and Lee, R., 1966, Geological map of the Highland Valley area, British Columbia: Dept. of Mines and P Petrol. etrol. to be typicaland typicalandillustrativeof porphyrycopper porphyrycopperand Res., Vancouver, B.C., Prelim. map, British Columbia. molybdenum eposits. We We suggest n conclusion Cooper, J. R., 1960, Some geologic features of the Pima

 

ALTERATION-MINERALIZATION

ZONING IN PORPHYRY ORE DEPOSITS

mining district, Pima County, Arizona: U.S. Geol. Survey Bull. 1112-C, p. 63-103. Creasey,S.C., Creasey, S.C., 1965,Geology Geologyof of the San Manuel area, Pinal County, Arizona: U.S. Geol. Survey Prof. Paper 471, 64 p. , 1966, Hydrotherma Hydrothermall alteration, alteration, op. cit. (4): p. 51-74. Damon, P. E., and Mauger, R. L., 1966, Epeirogeny-orogeny viewed from the Basin and Range province: A.I.M.E. Trans. v. 235, p. 99-112. Dixon, D. W., 1966, Geology of the New Cornelia mine, Ajo, Arizona, op. cit. (4): p. 123-13 123-132. 2. Drummond, A.D., and Kimura, E. T., 1968, Hydrothermal alteration at Endako mines--a comparison o experimental studies: Presented at Canadian Inst. Mining Annual Meeting, Vancouver, Vancouver, B.C., April 24, 1968, 28 p. Eidel, J. J., Frost, J. E., and Clippinger, D. M., 1968, Copper-molybdenum mineralization at Mineral Park, Mohave County, Arizona, op. cit. (1), Vol. 2, p. 1258-

407

Mayo, E. B., 1958, Lineament tectonicsand some ore districts of the Southwest: Min. Engr., v. 10, p. 1169-1175. Metz, R. A., and Ros Rose, e, A. W., 1966, Geology of the Ray copper deposit, Ray, Arizona, op. cit. (4): p. 177-188. Meyer, C., and Hemley, J. J., 1967, Wall rock alteration, op. cit. (•0): p. 166-235. •-, Shea, E. P., Goddards, C. C., Jr., Staff, 1968, Ore depositsat deposits at Butte, Montana, op. cit. (1), Vol. 2: p. 13731417.

Moolick, R. T., and Dur Durek, ek, J. J., 1966, The Morenci district, op. cit. (4): p. 221-232. Moore, W. J., Lanphere, M. A., and Obra Obradovich, dovich, J. D., 1968,Chronologyof Chronologyof intrusion,volcanism, volcanism,and and ore deposition at Bingham, Utah: EcoN. G•.o•., v. 63, p. 612-622. Nielsen, R. L., 1968, Hypogene texture and mineral zoning in a copper-bearinggranodiorite copper-bearinggranodiorite porphyry porphyry stock, Santa Rita, New N ew Mexico: Ecoa. G•.o•., v. 63, p. 37-50. Olmstead, H. W., and Johnson, D. W., 1966, Inspiration geology, op. cit. (4): p. 143-150. 1281. Emmons,W. H., 1933, On the mechanism f the deposition Perry, V. D., 1933, Applied geology at Cananea, Sonora, op. city (8): p. 701-709. of certain metalliferous lode systems associated with , 1952, Geology Geology of the Chuquicamata orebody: Min. granitic batholiths,op. cit. (8): p. 327-349. Engr., v. 4, p. 1166-1169. Ettlinger, I. A., 1928, Ore deposits depositssupport support hypothesisof hypothesisof a 1961, The significance of mineralized breccia pipes: central Arizona batholith: A.I.M.E. Tech. Pub. 63, 23 p. --., 216-226.. Fournier, R. O., 1967, Syngenetic ormation and subsequent A.I.M.E. Trans., v. 220, p. 216-226 alteration of the porphyry copper deposit near Ely, Peters, W. C., James, A. H., and. Field, C. W., 1966, Geology of the Bingham Canyon porph porphyry yry copper deposit, Neveda: EcoN. G•.o•..,v. 62, p. 57-81, 207-2 207-227. 27. Utah, op. cit. (4): p. 16 165-175. 5-175. , 1968, Depths of intr. sion and conditions of hydroPeterson,N. N. P., 1954,Copper Cities copper copperdeposits, deposits,GlobeGlobethermal alteration in porphyry copper deposits: Geol. Peterson, Miami district, Arizona: Ecoa. G•.o% v. 49, p. 362-377. Soc. America America Program Annual Meetings, p. 101. --, 1962, Geology and ore deposits of the Globe-Miami Gilluly, 1946,Prof. The Ajo mining district, district, Arizona: U.S. Geol. Survey Prof. Paper 342, Geol. J., Survey Paper 209, 112 p. Arizona: U.S. 151 p. Gott, G. B., and McCarthy, J. H., Jr., 1966, Distribution , Gilbert, C. M., and Quic Quick, k, G. L., 1951, Geology and of gold, silver, tellurium, and mercuryin the Ely mining ore deposits of the Castle Dome area, Gila County, district, White Pine County,Nevada: U.S. Geol. Survey Arizona: U.S. Geol. Survey Bull. 971, 134 p. Circ. 535, 5 p. Ransome, F. L., 1904, Geology and ore deposits of the Gullbert, J. M., and Lowell, J. D., 1968, Potassicalteration Potassicalteration Bisbee quadrangle, Arizona: U.S. Geol. Survey Prof. in porphyry copper copperdeposits: deposits:Geol. Geol. Soc. America Program Paper 21, 168 p. Annual Meetings,p. Meetings,p. 120. 1919,The copperdeposits copperdeposits f Ray and Miami, Arizona: , and Sumner, J. S., 1968, Distribution of porphyry --., 1919,The U.S. Geol. Survey Prof. Paper, 1 115, 15, 192 p. copper deposits n the light of recent tectonic advances, Renzetti, B. L., 1957, Geologyand petrogenesis t Chuquiin Southern Arizona Guidebook II, S. R. Titley (ed.): camata, Chile: Unpubl. Ph.D. dissertation,Univer.sity of Tucson Arizona, Arizona, Arizona Geological Society, p. 97-112. Indiana. Hemley, J. J., and Jones,W. Jones,W. R., 1964, Chemicalaspects Chemicalaspectsof hydrothermal alteration with emphasis on hydrogen Richard, K., and Courtright, J. H., 1958, Geology of Toquepala, Peru: Min. Engr., v. 10, p. 262-266 262-266.. metasomatism:Ecom metasomatism: Ecom G•.o•..,v. G•.o•..,v. 59, p. 538-569. 1966, Structure and mineralization mineralizationat at Silver Howell, F. H., and Molloy, J. S., 1960, Geology of the ---, and •-,

Braden orebody, orebody,Chile, South America: Ecoa. G•.oL.,

Bell, Arizona, op. cit. (4): p. 157-163. Ringwood, A. E., 1955, Principles governing trace element behavior during magmatic crystallization: Geochim. et

Ecoa.W.G•.o•..,v. G•.o•.., 39, p. 251-286. Jones, R., v. Hernon, R. M., and Moore, S. L., 1967, General geology geology of the Santa Rita quadrangle,Grant County, New Mexico: U.S. Geol. Survey Prof. Paper 555, 144 p. Kimura, E. T., and Drummond, Drummond,A.D., A.D., 1966, Geologyof the Endako molybdenumdeposit: molybdenumdeposit: Presentedat Canadian Inst. Mining SectionMeeting, SectionMeeting, Victoria, B.C., 10 p.

Cosmochim. A1962, cta, v.Crysta 7, p. llization 242-254.sequence Robertson, F., Acta, Crystallization sequenceof of minerals leading to formation of ore deposits n quartz monzonitic rocks in the northwestern northwesternpart part of the Boulder batholith, Montana: Geol. Soc. America Bull., v. 73, p. 1257-127 1257-1276. 6. Robinson, R. F., and Cook, A., 1966, The Safford copper deposit, Lone Star mining district, Graham County, Arizona, op. cit (4): p. 251-266. Rose, A. W., and Balto Baltosser, sser,W. W. W., 1966, The porphyry copperdeposit copper depositat at Santa Rita, New Mexico, op. cit. (4): p. 205-220. Sales, R. H., and Meyer, C., 1948, Wall-rock alteration at

v. 55, p. 863-90 863-905. 5. Jarrell, O. W., 1944, Oxidation at Chuquicamata,Chile: Chile:

Kinnison,J. Kinnison, J. E., 1966,The 1966,The Missioncopper Missioncopperdeposit, deposit,op. op. cit.

(4): p. 281-287. Laughlin, A. W., Damon, P. E., and Watson, B. N., 1968, Potassium-argon ates ates from Toquepalaand Toquepalaand Michiquillay, Peru: Ecom GEOL., GEOL., . 63, p. 166-168. Lindgren, W., 1905,Copper depositsof the Clifton-Morenci district, Arizona: U.S. Geol. Survey Prof. Paper 43,

Butte, Montana: A.I.M.E. Trans. 178,p. 9-35.

Schmitt, H. A., 1966, Por.phyry copper deposits in their regional setting, op. cit. (4): p. 17-34. 412 p. Schwartz, G. M., 1953, Geology of the San Manuel copper deposit, Arizona: U.S. Geol. Survey Prof. Paper 256, Lowell, J. D., 1968, Geology of the Kalamazoo orebody, 63 p. San Manuel district,Arizona: Ecoa. G•.o•.,v. 63, p. 645654. Simmons,W. Simmons, W. W., and Fowe Fowells, lls, J. E., 1966, Geologyo.f tthe he Copper Cities mine, op. cit. (4): p. 151-156. Lutton, R. J., 1959, Pegmatites Pegmatitesas as a link between magma

and copper-molybde copper-molybdenum numre: re: The Mines Magazine, Magazine, Dec., p. 15-24.

Spencer,A. Spencer, C., 1917, and ore deposits depositsof ofp. Ely, Nevada:A.U.S. Geol. Geology Survey Prof. Paper 96, 189

Lynch, D. W., 1966, 1966,The The economic eologyof eologyof the Esperanza Spurr, J. E., 1925, Basic dike injections in magmatic semine and vicinity, op. cit. (4): p. 267-280. 267-280. quences:Geol. quences: Geol. Soc. America Bull., v. 36, p. 545-582.

 

408

ALTERATIONALTERATION-MINERALIZAT MINERALIZATION ION

ZONING

IN PORPHYRY

ORE DEPOSITS

Steele,H. J., and. and.Rubly, Rubly, G. R., 1957,San Manuel prospect: Wadsworth, W. B., 1968, The Cor.nelia pluton, Ajo, Arizona: EcoN. G•-o•.., v. 63, p. 101-115. A.I.M.E. Tech. Pub. 2255, Mining Technology, v. 11, Wallace, S. R., et al., 1960, Geologyof Geologyof the Climax molybno. 5, 12 p. denurn deposit: a progress report: Geol. Soc. America Still, A. R., 1962, Uranium at Copper Cities and other Guidebook for Field Trips (Guide to the geology of porphyrycopperdeposits, copperdeposits,Miami Miami district, Arizona: Unpub. Colorado), Field Trip B3, p. 23 238-252. 8-252. Ph.D. thesis, Harvard University. , Muncaster, N. K., Jonson, D.C., Mackenzie, W. B., Stringham, B., 1953, Granitization a and nd hydrothermal hydrothermal alterBookstrom, A. A., and. Surface, V. E., 1968, Multiple ation at Bingham, Utah: Geol. Soc Soc.. America Bull., v. 64, intrusion and mineralization at Climax, Colorado, op. cit. p. 945-991. (1), Vol. 1: p. 605-640. --, 1966, Igneous rock types and host rocks associated White, D. E., 1968, Environmentsof generationof generationof some base-metal ore deposits: EcoN. G•-o•.., v. 63, p. 301-335. with porphyry copper copperdeposits, deposits, o op. p. cit. (4): p. 35-40. Swayne,W. Swayne, W. H., and Trask, F., 1960, Geologyof Geologyof E1 Salva- White, W. H., Harakal, J. E., and Carter, N. C., 1968, dor: Min. Engr., v. 12, 344-348. Potassium-argonages Potassium-argon ages of some ore deposits in British Thomas, L. A., 1966, Geologyof the San Manuel ore body, Columbia: Can. Inst. Mining Bull. v. 61, p. 1326-1334. 'op.cit. 'op. cit. (4): p. 133-142. , Thompson,R. R. M., and McTaggart, 1957, 1957,The The geology Velasco, J. R., 1966, Geology of the Cananea district, op. and mineral mineral deposits of Highland Valley, B.C.; Can. cit. (4): p. 245-250. Min. and Met. Trans., v. 60, p. 273-289.