Ore Textures

CONTENTS P,d.".. .............................. .

i,'

1. lntroduction .......... . ............................. • ........................ 2. 0'·~'p,il1til1gcri t ~,i. . ...................... . .................... . ................ 2 2.! c..""a!51at,mmt .. . ........... 2 2.1 Fi ... t onl IlIcOIlSislml all,rolÍlm cClifiguratiolls 2,k JlII,rolia" of allf,aljoll 2. 4 T/¡j,d o,de' c,il"io - 1"Ji,~1 o""'prilllú'g - ",¡'",alossrmblagrs ........ """, ......... , 2,5 FOllrln o,du criluia· h,dim:1 Ol"'prilllillg - Irml"''''¡''''' i"dica /ors J

,, ,, ,,, ,

se.'"

3. O'·~,p,i nting tulu,ts - bro.der pe rspecti\' cu.ting ,'e,n 4. Kidston gold mi"", Eina:;lcigh rcgion.. north St .... ctura I sUp"rimpld mining d'''''ct. no"h ~rd, Australia. (Sud Reef _ SYC Pi', C.rpet'''ri. Cold) s....pieion ."""ing - comptex ",'.rprin'ing. paral ,,1 ",acti,·.ti"", Structurol .uperimposi.ion."ein. 18. R.,,,,,,,,,·ood gold mining distr;"t, north Queen,land, Austr. li. (Nol.". j'il, C.rpet".ri. Cold) Smpidon . rousing _ romple< ",·o>tprinling p... I..,1 r""et",.tion,. . I",..,;on ",i,match, St'Uéturol.uperimposition·' ·"¡", 19. s.::...nsons tin mine, Mount Mowbray di",> _ P.~~l i c~ ty """'y n,;n",at dep$;' wilt p • .,,, ide 3"

"'."'p l ~

"f

«,"~

eullins "eins, ",h ich a ,e Cotl\'~ntion"lly int'·'pr~:~d as t\\'o (o, a single) gener~tions 01 h)'drothNma (lu ids lI'ilh an in t ",\'~n i ng pe.iod 01 . ock f.acl u,ing. Th~ c"-'ss euuins 'dalions hip is an ex""'p le 01 an o""F,i"ling t ,·,tu r~, and th~ implied timins rda tionship aUows th,· til'O ,",'i ns to N' eata logu,oJ as" t"mporal S"'"lions.;, to esl"blish a St."ri. ar~ ""'l' simple in Iheo,y, but i " r., nse 01 teehni,!u"s an' utilised. ",h ieh ."nge I.om l i.st to fo"rth o.d,>. dept>ndins " pon th., degre", of in le,p "'l.\li"n, 2.2 h esl orde' criteri., (Confide""" bu i Iding) (~)

Mi "" ral supc,imposition

Hyd ' Olht'rmal fluid s tr.",,·.,inS 'op,>n' ehannd"'.,)'s may p.~eip¡I~I,· min,"~1s (infill ) ana wlwre On ,' ,ninc.a l e~ " be _" to ha"e nucl~aled opon .moth~ r. .,,' obv;ous timinS (o,· ~rp.i nti n s) .cl~tionsh i p CM' be infem"a No"ll"ous "x~",ple-s arc si""n in Vo lome 1 o( this .... ies, and "thers are disp l ay~-.d in Ihis !exl (Plate-s 1-3). (b) Sl' uelural supcri",posi tion Rock o. ",incra l failtore oceurring alt~r a pe,i od of hydroth",,,,al d t·pos il ion. \\' i ll Iraelu '~ .nd/o . Itasm .. nt pr,'ioosl)' formro ",i"c.al •. This co,nmOn silu.tion prol' id"s a ranse 01 ne\\' (o"erp' int inS) channel\\'3)'S fot fluid flo", .1nd d~position. 'fhe net result p.o\'id,.,; Ihe l\\'o mosl eommon crite,;a utilised lo sepa ••, l" O"t· pe.iod of mineral depo,it io n f.om .nothe" (i) C.o s. eutl ins \'ein s)'stems (euh ", ith spa •• k inflll l a Iteration comp'the, , Gi"en th.1 Neh inflox 01 flu id ",ill r.,sull in a "el\' infill "s....,mbl ag~ tos~lhe. ", it h a lkration 01 ,>ithe . p,,,·~xisling all~ration, or p re"iously unall~1\'d host 'OCleS. it is not so.p.isinS that eomplex s iwalion. m al' occu'ObS"T\' a l ions that raise .".picions 01 mu1t¡st~se OI'e'printi"g ;"dude the s truOmal supe.imposition criter i., m"ntion"d abo\'e, as lI'e1l as le .. ob" iou s .ilualions su rh aS: (.) Mi.malehes betw e cn a lteration and i"fi ll rumponcnlS ( I hin",~ oot 01 p'opo.tion) . l"eludins:· (i)

Small

eh's " si " ,bl~ eh;tnne l"'ay slruetu,e (I' ein, she.t, ' tria nsular ,·"S") (ii i) Veins (uso. II)· fi"t not~d as inlill st,uetur"s) ",hich a lthough ,e n t.;,lly loe a ted ,H o,ond altcration ",ithin the majorily of tll i"h~r"n, l y ,..rer to inlerpri'lalions regard ing In .. re lali,'~ time ,;equ ... ncing 01 hydrolht'rm.¡ e\'enls. Ho",,,,·.. r. i1 is imporl.nl lo pereei" e Ih.'1 Ine time sequen~ing obSCr\ations a¡.., ofler lhe opporlunit)· lo 10010 ot e. eh slagf scp..1r. tdy (or in eombin a lion) lo esl .l blish a ",idH r.lnse of gf.'que pr~eipit~l~d . Th" p.obl~m can usu.lI )' be rl'SOl"NI by inspecling .. t..rge numbe< of ... mplc5 rtkolaT SI.g.. aod slowl)' ...... sing "'-'1 I~ CTitk~1 'o"-"'S.o..-Ih' ."I.tioMhip~. Ob""" '" ",, should nol eXf"-"C1 lo di"",,,, 1"" full 0; S

P LATE J

SEQUENTlAL IN~ILL SI. ['alrick l in m",~, nea' Ir,· ineb.n k, oorth QueensJ"nd, AlI,trali •.

hiS speeimen has beco sel""le0','" includ,' 1.. '1 h~nd sl d ... depiclS • ''''''1'1 ..1.· \ l'''' ....:tion. 11>.. 1>0" .och are urbon.te unils ",hiel> are ¡u •• , ,.ibk a, dork ,I,,·~~ un 111" 6" th,' q "M17 oH" ""il w"",", pul li "~

.p,''', w;'h ,"'o'''",pi" , 1" .. ,

"' · ...- I" i oh,,~

,,¡ ,

~'. ,'. '''-'' ""," I' in¡;

~."",

01 I'.>k' ."",,-.,1, .,,,,,,,

",;n m.w ,II~, I'I~'" w,lh",,' ,-t... , ~,.;" ~~. ')' P"~' i1 ,."",,,-,,, ." "" li c~ ;;'k. ""in. lh;, ,.." ilin sc~ms 10 cut e\'crythi ng and is composed of fairly uniform d,,,k g"ey siJiea_ Th,·,,· is httle ",,1 e\'ide""" lo delineale Ihe proporlions o¡ infill \'e.sus altcTation. although Ihe rela l ively gooJ matching walls sUAAest infill prl>domin"tlO;:. A¡pinst Ihis il seems tltat some selecti\'e alterat i"n has oceurr,>d 01 th~ ,'cin intcrsoxtion 31 the top ri¡;ht. A very close inspeemS 10 occupy a fault ~ooe. as no,"", oí the veins on either side can be conlidmtly matchl>d The welllam inated (light and dark layered) ,,in (c~ntre·lch). appears to be symmetrical sequentia l inhll and th,> dark spots ore probably molylxlcoite. The sharp malching edges suggest Httle if ony "ltCT3tion _ Nonc 0 1 Ihe Olhers "eins conviocingly match this inlill Sl'qU'>nCl>,

"-

'U ",""",o"""",.,o",.,""mN"C"""'""""" =

ORE' TEXTURES VOL'

Th~ ,'~in to the I"p rigot h~s .on\l' dem('nl, of th .. alx",e S&Juence (espL> the ext",mc right), bul " 't'm S to be cu t by another geoerJl inn of silk~ at a sh"lIow aogl~, This i. L'itl",r "fl, or is rmmi,,); up th~ sio.l'·T\it,· suu,,,t r,'pid depooilion with multiple oud~ati"n ,ites, Th 11,.. most oo,' ious stage is ,ep"-osented by the ",idé,>1 I' ertica l veins, wdh Ih" p al e crea m material eons is t"nll y On Ih" Idt hond ,ide, The p~ l ~ ne"m makrio l (caroo",. t,,') imme;, side, or is Ihe ,ili"a ' -ein opcning on One side 01 a p,e""xistlng earbonal~ "ón' -rhe", is ' -ery lill le CI' idcn", lo Sllpporl eilher hypotl-..,sis , It ls not,"oci"led ",ilh hiSh p ressl'''' IIt"d ,"Iroducllo", (h)'dr,l\JI,c J3(K'''gJ '1h... twly hislor)' f Ihe rock is besl «"en in 11>.pIAt .. _ Th .. , .. ur inlill ( m.lehin~ "'Allsl. and b.-st 'ep,~n 'l'd di Ihe ">p 01 Ihe plate. CtOM' inspen ~',,"Js a minu\t> Cft1 lr~1 p.lIk' brown ,Tin of lhe ,id .rite slase wa"""-'ting along II!. horizonlal da", !ourlNli .... infill bu' co",,«t inS lO lhe "e"ol srsl.....,. The nHI se! of ,· .. iM .r.. Ih .. dark horitonlal sel wh"h eonsisl of d a r k inHI! (lour",alin~) and "ariab le amuunl. of Srey/ white (sil k a ) and dark (lourmali n t') alter"tion. T he latler is prob a bl y altering an origina l f"ld.pathk COmpOnffll in Ihe rock an d mar S •• d .. oul inlo Ihe sr~~n . f.i ei le m..... 'ione('1 p.lIrt of Ihis assemblagf, ... pr..sentins al\t>ralion associalfll wHh an E-W ' rAclu ... ,rossing a

Th.' ... rllesl "ein sel is Ihe wh;te /¡;r~y q.~"z ve;n. whieh conl.;n occas¡onal d ark (tourm¡line) ctnlral zones and coa rse ly crystall ine (omb slyl.. quutz. The .... in. display no ,,11 .. ration a nd their J...-,,,,,,-

p ..... ",., • m i , 01

I .. ~.

'o,d

I"s ... n',. ,." 1,,,..

r. •• ",.nl .. 1 r", ... ",) ", .. 1.. "." , .. " .. lo"" ," " .1•. p.opo ... on •.

Th • .,." ~"I"~uhon ,,1 Ih". b,o~, ..

'o., ..

u.u .. l.. lI .. n~1'O ..........

"Iu"

1"""."

r LATE 12 STIIUCIURAL SUl'ERI1>II'OSITON· HR ECCI A Di,racli Sold mine. Ri""lon d i~lricl, cn.al1ers T""'ers. nt)I1h Qu...,,,,I~n.d. Austral",. Specml" don.. tt.'it,· p ldt ... belo", 'Nding the dibly uuscd by bL>, ling ,""ti,·,,)'.)

n... mldd ", ,t..ge is besl obsen'od b)' IrolCki"g Ih-< ' '''''' yell" ... bull m.\le,ial> .... I,;ch a ... "ar)'ins rombll1.uiQtlS

oi St'r;'::il,·,.,1(! PY''''·· TIll'SC actually alllink lgdher in ,1 cumple, "d ... o rk . dt bo lh a eo,,,,,,, ."d fine !O:., I ~ 01 Ir.1 ch"i"lI. -rhe dil/e,e nri ation belw .... " i" l il] ~"d oher.>li"" ",ilhin lhis , 'a,!;" is difficu l' . and n,,! ' e., II )' poSSib k-. Intuili\'ely ji Sl'(>mS Ihat pyrilt' is in""lwd JS mllll. b UI it .1 .... p roba b l)' "'-'curs os an .lIe,alio" prod ud, and give a vcry good idea 01 how the two dilfe.en t s ulphid es break "p. The breccia brea.., thmugh p.-..--existing s ulphidcs, "nd Iragments ha,'e .. I~~rly h..... n ffltcf'fll lly tra n sported . Sorne sty le 01 "xplo.i,·.,/intr u si,'., b.ecdat ion (milling) un be inl"rrcd u a bte s tage e-'''''I. In Ihe Idl hand 10p CO rner a con l in uou . rim 01 .rsenopyrile (silver) with sem i lo good crysl.l lorm COOI. 0\'.".. large sphalcril" (dark). """ I"tter secms lo "xhibit D cryst. l shape, although it d«0111id no"" Thi~ f~"'p l"x b.eeci.l is ne ... lr all ""n'posed of infill "';Ih ve')' lilll" alter.lI ion dl....:I., 1I alte.ation had bo."("n • m.jo. compone"I il is nOI h.rd to imagi .... 110", d ,fflcull it ,,'ould be to un.a,'rl' Ih" SI),lo:s of brec, iation '~p ,~nted a re . n"lh. r . Sp«t " ' hieh nttd< ""n5lde.alloo!

o I

1cm I

ORE TEXTURES VOLUME 3 OVERPRI NTI NG TEXTURES 33

r LATE

15

STRIJCTURAL SUI'F.RJ~II'OSITl0N - VfINS. BR[CCIA U"~,,o .... n ti" mine. E,,"~n. K.ng.""" Hill< ti"lldd, norl" Qu('t'Il.I,,,>J. Australia . 5pning br0""('

,ic"

The pIJ!' ronl,,;n" mullir'" S""ll lh .. e""", clIllinS sl.se in 1"" boltom right hard romn?

11 lltiro .1.SS 400~C). This plale is another good examp le of refra ctu ring along a pre*existing c hannel\'Va y, and again emphasizes Ihe need for good underslanding of Ihe infiJl /a lteration linking. Infill textures at Ihis sca le a re freqllenl[ y overlooked.

o I

lcm I

ORE TEXTURES VOLUME 3 OVERPRINTING TEXTURES 39

PLATE 18

SUSI'I CION AKOUSINC· CO.\ll 'LEX OVERI'RINTINC PARALLEL REACTIVAT1QN, AI.T[RATlON ~II S M ATCl I STIccon d ly 1!>e..... 're lIC," ~.al hinl~ thal ~rse""i,)".il .. may bt· in tin)' .... in. Iha' ~""OSs ~,, ' /.ngl~ ac~ ,!>e sph..o1o>rit... The spkal.·.il~ in Ih~ ')pi~ .. 1 eo.'s~ . ou nd ed a)"SI.1 (o.m . • n d illd" id ... 1gr.,,,,, 1oo~ lo b.- brokn """' in , ..... urP'" of th~ righl h..Ind ,·~in. no is no! ~no~gh

"g"

""""111

....,1,,,,,

..:1

Th..

ORL lU;l\JRES \·(M.L\IE J O\·ERI'1I.INTINC

nxn. ~

evi d ,~~

lo be o ·.t •• in. bul f.onl otl".. 'pt' 11", 10p I.. fl ,1 s ph.lle.iI~ i"fill is in di."", ro"'",,' ".ilh d~.k ".dll roc~ and is no )'dlo,," .. lIeraIiO"_ T his ahe.ation mi sma tch i, .gain suspkion a rousing. Th .. )"..110"" (se.idle ) alt.,.-a tio" cou ld jus, be motchNI lo Ih .. a ...... no p)"rit~ or mo.e li kdy is ",I ..¡,.d 10 the mkroth,n ~10> (Pl'ril"') "";ns. N .. ithe. a no pa .'icubrl)' cOI",i"";ns! ra l ¡:>oin ls c .. n be obsen....t ............ II!.- d •• ~ g ........ minnol in II!.h"", ro'" is slo",l) e""'e"'''S into tM dull .... .,.,y. ), ..110,," g . .... " .... k il... E'·.. n Ih .. o . igi nal .ock i5 nol ",hal il se " ~ picion Mousing rri tNia e\'Cf)"whe.e_ All~ast Ih".....",d quil~ pmb.1bl)" fo". stages .\fe possib"" This ;s the ""0"1:\ sp...., imen fo. "'·"rp.inling resoluli"", .nd 11", ~"'er .hould slop aUt'mpling missÍn impibly ~UMI7. (1"1' lefl). A p,ubl"m imm,' gi,·.,s Ih,> elue lo ,,'p.Hating an ,'pp",\-nl l)' single ,tase into [",o.

T

The ",al! rod, (bOllO"'. ,ent r.. ) is composcd 01 fi n.g,. ¡ned ., Ibite (grey) w¡l h ol,·» Th~ o"c'p,inling m.'k,i., ls (wh ik / pink ) dea rly exi,t as ~ltcr"l i on, ",ith the ",hile, (al bilc) ocen,ring as a" . Ikrat io" "r tlw h~t ","c k. At firs! sigh t Ih., "h ile

44

O~ F.·I

EX1'U Io: I:S I'OlUME 3 OI'ERI'RINTII>:G TEXTURf.s

(albile) "",noS lo .,"'- u, as" fringe lo Ihe pi .. k na tNi.1 a nd a n i"itia l inl"'p"'lation ",onld a"ess this as a zoned Jltera!ion fro"t, Ho,,"c\'(" ir Ihe bscn' N ca,d"lIy I,aeh all aronnd the f,onl. I h~,c is •• point (y.t'.'CI. The 1>0,,1 !"OC"(s) • ..., fi,\(· grair.ed meta""'¡¡mentM in t......... oo lo >illY-silnd. si,.. Tang.... 1- . - ..... ron'posro 01 '.1')''''8 rombi .... ,ions 01 mi.,."..I" p.1t.. grttrl g~'

(f"ldspa,?j pale grey (quartzJ dark black -grcen (chlorit ... biolit .. ?) and gJ..ssy red (goo..-nt1?). Th .. m ~t b,-;o", chan" .. '",.}' is r .. pr~nrl.'d by • d.,k infill -n .. in s tr uel u.e (cent'e . ;ght). Thr d~ r k m.I... i.b (g"-')' 'l"Mlz and bl.ock 10". 0"'li .... ) "",m lo rel ale lo ~ ,ery iHegular alte ra llo" h~lo ",hl;h is mosll y while, wilh some irregubrly d i>lribu l ~>d ¡Mle )'e llo\\" co"'po"e"I$. The aeh", 1 ,'cj" is im".,rSi,lent. a"d Ilwr~ ~rc b lolch~'S 01 darl bufl ",ateridl ~ssoda l ~'d wi th do.;e~" al,on il .ppt'''''' lo be •.. p lace.os Mn ;""¡,,dfd to muSlra,,- re,a',,''''Y 00"':;",,' o,-e'p"nting whi,h is ess..-ntially laye. (Onlroll~d_ 11 a lso s ho,,", a su bll ... u a mpl~ of alter.lhon alkring ,.Ite,.uion.

T

s~in1l'n

¡"""

",igina'''. Tick IIilI gold mine. lhe pin l< rock ¡. Ihe gold b".ring unit. It is , t>mp is al", an Q"c'p,inl, ""d OCCIl"", an " It"r.,tion of bolh Ihe pi,,1. and sr.",,,. A ,m. 1I «SS cuning miero,'ein ;s ... ell d"pla yed (le/! hand _ide' cenl ... ) aS in cross cul~ Ih. srcen rock and 31t~", 1"'-' darl? and / or ...m,,,,nt al!>tc (pink) ron'p