T E H T U R R T Z O N I N GIN

E P I I H E B M R T O U R R T Z U E I N S

G r e g g M o r r i s o n , 0 o n g G u o g i , S u D h a s h J a i r t h

l\\

K L O N D I K EEITLORATION SERVICES

TEI ITURRT ZONINGI N

EP ITHEEMRT OURRTZ UE I NS

6 r e g g M o r r i s o n , O o n g G u o U i , S u b h a s h J a i r s t h

K L O N D I K E

ISBN 0 646 241427

rekplre: (Om215193Fa6'nile (07) 2i 2003

@ Kimdite ExploFtior Snices

Thh b6t is @pyn!l. Aparl foE any fair deling for the pu'?ose of privale study, rsearchcriticis or revies, as pemitted under $e copyriel Act, m pan my b reproduced by my

Prccess withont wdnen pemissio..

Genenl e.quina ed puchas EquiFnenrs should be addresdKlotrdike Expl@tion Sefl i@s

7 Mary StTOWNSVILLE QLD .Aio

AUSTRALIA

TABLE OF CONTENTS

INIRODUCI'ION

CLASSIFICAT]ON O! QVARTZ TEXTURES

THE ORIGIN OF SOIG QUARTZ TEXTURESlriney emwth textuEsRedystalistion textresReplacenent rcxtuFs

OTHER MINERATS

TI]E TEXTURE ZONING MODEL

ORIGIN OF TEX'|URAL ZONES

Rtrrysbllisatio. bd rp]rei@r

DISTRIBUTION OF GOLD CRADE

APILICABILTTY OF THE ZONING MODEL

REFERENCES

PL"{TES

I

2

5

9

1214t516

17

1 8

18

21

INTRODUCTION

Most recent explootion of epithemrlveins has utilhed thc analogt wnhgeothemral sy$ehs ro interjrret fluidcondidons and posiiion within the stslem(e.g. Henley&Ellis,1983).Inranicular,laboratory studies on samples of *allrockhave been used ro ldentify rlterationnrinenl assenbhses which have nrenbeen conpued wnh assenblases in activeseothemal sy$ens (e.e. Lelch, 198?).Thc difficully wirh rhh aFprdr.h is ihatthe trcld geologist cannor rcdily idcndfymant ol thc crnlcil nindals so thrt theren a tnne Iag betweeD mappnrg or .orclosging and inierrreiarion of dre alrefttiontuineralogy. Our expe.ience wirhxtlontion of a vide.!oge olvein rypesin norih Qucensland is thrt the tex!{es ofvein quanz offei lhc ncld g.olotist noronly a r!pid reconnaissance tool tocvaldalc the chlracter ol mineralisinEcnvironments but aho a means ofide.rifying nineralised Iocii \rithin veinsynens (DoslinS & nlorison, 1990).

Recenr reconnaissad.e. .outrled \rithdetailed work on selected occunencessrgeeis there N a consisrenr sure oftexiuEs thatcharacteise Dary elldi.mveins. Fomal definition oi rhese texrDr.sprovides a rra.re of Eference lor thcsystenatic description ol samplcs.Pe i .o log i . Fo .k has a l lo redinte.pdarioi of the onsin ol rany ol lhetextures and the definnion of lcdcticgroups *ithin the cksnicaton.

In sidple veins there is a conshtntprttern ol dhribution ol tcxrures andconsistent assemblages of rexiurcs thatcan be used b define a leni.xl txruralzoDing Dodel. Such a model can berarionalised in terns ol fllid evolution inboiling georhernxl sy$eds and hencediredly conrpared wirh the nodel ofDuchanan (1981) to defi.e positionwnhin the systcn and ihe mos likelylocus of gold. In addition, an empiricalevaluation hxs becn nade ofa number olsy$eN with siEnificant asry data todete.mine yhich textDral assenblagesDo$ comnonly have siSninca.t goldCrades.In minerahed simple veins theerc specific textural assemblages rhatcatry grade. In conplex nultiphasesysens, orc shoors may contam severdtextunl ascnblags dat aE disdnct liomrhe asemblages in thc adjacent barenlode and have their oen inrernal zoningparcrn. Thus the quartz nrodel should bccrpxblc or deteminins venical position*ithh a boiliig epithemal vein syiemand prcdicting rhe locus ol gold

In practice, dev.lopmeot of a texroralzoning model inr a prospect .eqniEscaeful and syeenaric obseNltions onbroken sudace material, drill core orchips. While recogninon of all rextrmltypes pEsent is impoiant. rhe relativeabundance of 'exM tyFcs and theirtiming relarionshi!s are ssential toe$.blishins texrural a$.nblages. Thetexrml assemblage concpt is rhe smre asiLar tor netamorphi. facies or alFration

2nineral asenblages. While individualsahtles can be a$ignen to a txtural aneblscd on their texrural asscmblage thebounddjes bctwen 4nes re gradaiionalor overlrpping so that iudgehent srcquired in defining zo.es rhal *illdisingulsh inreFah of difiercnl onein o.

The lDrpose or this guide is 10 provide anilluslrated refrencetextures in edthcmal veins, to provide !s.ale nodel fd tne disfiibution or textordla$enblages *irlin an idealiscd lein andio identily the txturs and extdral zonesthar nrost conmonly host gold

CL.\SSIFICATION OF QUARTZTEXTURES

The classification of cpithennal quartztexrures has been dcveloped frcn arcview ol textures described in the

eraturc and ron an evaluation or odsdple coll4tions. The texnres descnbedare those rcadily identilied in hand-specihen Ma.y also have disrinctivefea$rs in rhin'section whlch have beni.corporated in the delinition vhereappro!.iate (Table l).The basis of thedsdlprive classification is the narule ofcrylal ageregales bft rhe textules havebeen erouped into three najor clasFs toaid intertretarior of lhei. origin a|denvironment ol fomahon (Table 1, Platesl-22). Prinry rrowih tcxiurs repEsentlnnial open space lein fill. There is anatunl subdivjsion of the Primary growth

textures inro those characreristic ofcryptociy*aLline quartz (nassivechalccdonic, bandd chaLcedonic andcollolom) a.d those characterlstic ofcrystalline quutz (sxccharcjdal, conb,zoned crystals). The membe.s of thesercxnral 8&ups co'monry dcur togetherand in sone cases the.e aie gradarionsfrom onc texrure to another.Recrysallisation textures ieflect rhehnsfomation ol amorphoDs silica orchalcedony io quanz. ThcY are mostcommonly associated wirh cryprocrystalline qudz texiues and may pdlyobscuE then vhere recrystallisxrion isextensive. Replacementrextuesrcpresentpanial or conplete pseudomorphs ororher Dinerals by silica niner.ls *ithin

The lorm ol individDal Enins rather rhanaggregates can also be a usefulclasificanon roor Wnhin an epithemalvein thee is a.onplete sradation frcnamoryhous sili.a to cryptocrystalline tocry$alline qudz with a vdieiy ol crysalhabns Gable 2). Sone textural clasessuch as massive chalcedo.ic ors&chmidal ae defined as consistineofonly one grain form. Orher lexruralclasses, laniculely crusdfdm textur,have conbinarions of Coi. roms Forrh.s rexrures, estimrtes ol the Elativeprcportions of diffcicnt Sirain lbms ae auseful guide to posnion vithin a textualdne. Tho ovdall progession ls to 6oFcrystalline qudtz and to more equmt

,t ^ Bf,E I: C1.\SS]NCATION OF QU

PRIi\IARY CNOWTH Tf,XTURES

M.\6a ettate?danic @tat t.2J

sdhdea .hak.hti. tasde) e\at s r,4)

sAccHAroDAr (Pb$ 5. 6)

ToNED cRYsrrS (Frrr 3)

hxbn) ripinr or charc.dory il cruniform br.ds.CRUSTTFORT{ (Prabs r0,r D

Co(cntric cnriroa. brnds suroun

MrcRoPLUr{osE (Prar. 1t

i r 'rdrir.6rd.d (Prars 17, l3la , a , o \ . f , t . ,

l ' ' ] ' | { 3 n , " ' ' { o | , . ' ' och,r ,rad.d (Prsres 19. 10)!:" r " 9r." /ur Lr idin!_ oi mDrlr\Pt ttet blad.d e\xB1l,17)11:l , rr: "i "

TABLE 2: FORMS OF SILICA AND OUARTZ

AMORPIIOUS SLICASilica ihat lacls otsrsllhe strnctue d a chdeerisric ddd fm.CRYPTOCRYSTAIIINECrrstars that @ loo snall to b distinsuisned undd th ddl.ary ni(l1M!eNEEDLEN*dre shaped d aciculd dysiils widr a c-dis ro a-dis rario g@le. dran 10:1-PRISMATICCrtstals yith one dimnsion nekedly longer rhm rhe orhd two.tnng Prish: dystal with a edis to a-di5 ratio of 5 ro 10|1N(ml Piisn: dtsur vith a c dis lo a uis niio of 2 b 5:1Squat lrisn: -y$al snn cdis to a ujs ntio less lhm 2 io IEQUANTCrystals witn dE sme d netr1y the ene diderd in aI diEcrions.All dial raiios less thM I 5:l

For the purpose oflhe classilicarioo, oolytexNres w i rh in le ins ha le beenconsidered. Ahered, panicula.ly silicifi ed*allro.k *hi.h is a common c.osniNertof nby eprhemal lodes d.es n.r exhibita r..!e of rxtutus useful for clasrification and so is rreated as pan olwallro.k alterrtion. Breccias ehich aE.ommo. io bolh lodes and venr, needaho to be teared separdely. Tecronicbec.i$ dominrred by qrllrsk lragnrensand vriably over!finted by hldro(hennxlxlr.ralior crdnot be !durted lron thepoifr of !ic* of quadz textu.es. Hoqe!er, IrfdJothcrnrrl brc.ias developeds i th in ve ins or by overpr in t iog o lex,$!,g !eins do cornnio.lt hrvc infill'tldiz textues tlrat cor becompdcd Bi(hrhe clx$ir,calion. ln derign!rinC rexruEso. rexnml asemblagcs io be.oirs adirrincrioo is nxde bclwcon clr!s andntt'x, nnd symbols are addrd todesiEnarc arcxs enhin lodes or renrswherebeccias dc prsent. Theclas andmrnx texnml assenblag.s .rn nomullybe conpdcd eith rhose iD dE hos v.inso nrd rhe dcercc ol.h$.rovemenr aftehnngof hy&olhemral bE.ciarion cdr

'rItE oRI(;IN OF SO}tlj QUARTZTEXTURES

Thc onlin ofqudz textures cM plnly beexplrincd by ituerprerarion of rhebehaviour of quaiiz, chal.edoil ,odanor lhous s i l i ca in h td rorbeml lsolLtions. As Nnmafted by Fouraier

(1985a), qodlz is rhe mo$ ixble lom orsilicr tn hydrothemal sysers. Facererl' tu r i z . rys ta ls genen l ly a ro* insolLtrions *hich a.e sliChrly supcrsatu nted vnh resp4t ro qu d4 i 0 di.arin8relaivelr' sl.*ly changing coidirions.Where qua.tz lecipiiares in opcn sprcedire.tly iron hydrcrhermal sollrion, itexhibns .rlnrl faces aDd locally wirhgrowrh zoncs ofinclusions tud all. lxesof qudz reroughll,perpendiculd lo destrrfte upon which !ro*1h initialll'

Chal.edooy mry lorn eirh- by d;ecrprecipihtun fom h]'drcthernal solu onor by txnsromxtion ofuroryhotrs \ililarocry$alline nxrnal Inrernrediar sili.asuFrlaruranon wrh resFect to qudz {rcqlired lor chalcedon! to tEcipiraredtr..lly fom soldion, a n atpea.s rotbrm md te(isr only ar rcnperatu.es

Thc detosirion of aho{rhors sili.arequtes a h igh degree o f r iL ica$'peNarunri.. wirh Erpect ro quanz lndera i l , wbtc the deEree o f s i l i ca!'perratunlon 'n respeor ro anoryhoussilicr relches a fx.1or of about 2.5,lDniogeneous nucleario. is likel), ro occurrltroLghout a sol ion (we.es er dr..1982). Silicr polynres gro* pricrnicdnu.lcos sze, aod liially corgnlare orfl occuhte, producing !cladrous mnrerial$hich lareris ranslormcd to amoryhoussilica, The anrorpho!s silica whi.hlorh.d rhrough rhis Fo.edrE usullly

6contains a ldge anount of Yard udsoneddes exnibits slheroidal ge1sEuctue. r de8rees of supdsaturaronac not gear nough to aUot thefornation of colloidal lanicles, thedeposltion ol mo.phos silid tales llacednectly on pie-existins solid surfacesftom aqneous solutions. The resultingnaenal is de.se, viFeous silica which@rhi,! mnch les water the thar initiallydcposird nDm getaiinous mtedal-

Primary grorvth t.$urs

M-q$:relbalcedo4e te{@ r@s underconditions ol intemediate silica suler-satuation wnn rcspect to quanz. Lrvrenpenhr (below abour 180'c) duingand alts deposition is eryonsible for lhelow cryslallinity mainiained in this

4g4! (6bous beded charcedonic quanz)is fomed by crystallisatio. fron aniniiially Dnifom rD6! of snica gel wh.ndifferntiatioh (or self-orgeisaiio.) iswe[ dwelopd duins d crysallisation.Ar low temperalures, because of theqfrene slowness of nuclearion nres ofs i@ binenls, high degres of silicasnpdsaruation cd b mainlained in thesoludon for quitc long periods of tihe.Tnis favous tne develolfenr ofoscilatory diff@ntiatio. of gelatinousmarsi,L f(ming agare bmding.

is sfiCndy supersatunted with !specr roquda but udeNhrated wirh rcslect rochal@dony (Founid, 1985a). Tiis slgntsnica supeerurarion k lo$ibly brcugnrabour by slow cooling or the syst n edunifom growlh from mulriple nucleii

zoned r$als imply nildly fluctuatlngenvironnents dunng crystal g1opthna*ed by encs or riuid and/or slid

Collof(m rdtue in cnat donic quM isinherired flon orieinol silica gel. Thestrong su"f4e te.sion of rh silica sel isEspdsible for the rcu.ded or tidney lile

CrNtif{m te$w is F comon that it isconsidered r diagnostic f.atuc orepithemal veins (Buchanan, 1981).Repetldve beds of dilTcMt @nlositionor rerture @flect fluciuating concen-sations of eleme.ts in solution andnuctuaring flnid conditions du.ingprecipirarion. These fluctuations areomonly asdib.d to pciiodic boiling of

Reoysiallisation tertures

All silica ninerals excepr qurtz @merastable. Aft! dposirion, rhey have atendency lo Fesfom to qudz. The siaed gendal appemce of qudz f@cdaier anorphons silica @ chalcedonydep.d; npor tmy facroa including the

rexha i6 qTically fomed in opm60@ a hydrclhsn l solution wtu(h

nrclertio. nechanism, inni *arercontenr or ano.lh ou s silica, renpcra rue,and composnion of the pore soluriod.Tide. high remperatun, high pH, hiEhsdinny and rhe presence ofdissolved Mghave all been found ro lavou. ihetansfomarion ol amorphous silica rochalcedony or quartz (Fournier, 1985a).Anorphous silica rhat h dcposited ardepth is likely to convet i.lrtiv.ll, npidlyto .hdcedony or qudtz, owidg ro high

Moss rc r ru ro t reseNes ar . r ig io ! ispheroidal gel texlure duriig recryiallisation ro chalcedon! or quarz.'lhe spheroidrl gel sncrure may belomred cnhcr byrhyrhnric dcFosnion olsilrca ecl a.ourd a nuclcus such as atbreien tdicle, or an edll, silitu pi{ricle,or by sc.ondrry dilfnsio. duing dryingot $ater-nch gelairous na@nrl. Veryhigh dcgrees ol silica supersarmrion,trhich lcad o the lonnarion ol highlyviscoos eelannous hllenal aDd rclarivelyhiSh te.rperarures, vhich larour recrysrallhation, are rcquired lor rhctomration of moss rexrure.

I,licr.plrmose rcxrure h6 beeo noredbyAdans (1920), *ho callcd it learheredor'tlanboyanr', and considered ir to bere*ricted to $trficial cnvironments.Sander d dr (1988) illLNrared samptesfrod some epirhemal veins, whi.h shovplumose extincrion in rhe rnn ol conbqudtz w'rh a cleu clhedral core. Theysugges ths iexrure could .esult lrcn

eirh.ri recry$allisarion of chalcedony o.amorphous silica qhich lomed a coatinsor euhcdJal qudzi or by accumnladon ofdomalns of qu.nz cry$ahes which gEwindividuaily b o!n space berore beinE.oated. The nsr loi (Ecry$dlisadon)perhaps is also rpplicable ro rhosesamtles which show welt developedplunose extin.tin throughour qrdrzcrriah and scaitered randonly $nhinganular.lDdz aggregares In this cxse,n,cro prumose Gxnrreperhaps repsenre ' rher an in re .n red ia re s tase o lr.cry$auhation or rhe producr olinterfecr FryMllisarion.

Rcplacement tertu.es

From rhe c.nrarison of noDhologicalae ures berpeen quadz and possiblerrory ninerals (like.dbon e, $lrare.elc ) Ne suggest thar mos tar ce bladediextoF r.sults honr rellacenent of bladedcmonatc by 'iudz. Thc exEene rhnrnc$of blldes, lanellar paiings,

.hon-bohodral cleavage and wcdee tikerernnaton aE cheactenyics ot lrimarybladed.arbonate. Thc rranslordarionappeus to r.volve overgrcwrh of rheb)ade by line.omb lite qDdtz sranN aswell xs conb like Erowlh along tameltarpaftines within rhe bllde, presunrblydunng ft dissolLlion (Plate l8).

h ehon blndcd texhre rhe blade forn honly deliled by concentarions ofLnturties retalned ftom rhe orisinalnnrcol du.ing replacenenr by quanz

(Plate l9). The replacins quutz isgranular and interlocldns and notinfluenced i. gni. roft o. dislribution bythe onshal bladed texr@ (Plac 20).

Peallel bladed ten!, could rsult fmnrellacme.r of grelld calcite by qudz6rong .epeared lameuf pdlng planes.The lamelld lding, which is pdalel tolhe basal pildoid ol cdbonate crystals, isthe mosi proninant or aU norrhologicfealures of carbonate in epirhernalenyironmenh. Replacement proceedsalong these plmes nde elsily than alongrhonbohednl clavage planes, as noredby Adams (1920). This selecrivreplacenenl yields a sel of panllelstuctures within bladed pseudonorphswhich de displayed under rhe niqosoleeithd by di|felent grain si4 of qudz, btprefded onenkrion of qufiz snins o.by difierent content of impuiiries (Plate22). The or;ntation of cleavage planes olindividual blades is the sane wnhln eachErolpi which indicates ihar each groutlelrsenls a sirgle cdbonar crysral.

mosl common ln epithrmal vei.s aswhile or pinL rhonbic crysals liningcodb qualtz veins or i. tustifom bands(Pl es 25, 34). Ii has orso been obsewsias moss aggregates assciated witn nossquartz and chdcedony in crusrifombands (Plate 32) and as ass!gats ofnedres f@ins disftd @stif(m buds(Pla& 23). h many exanples, theaduldia is vdiably eplaced by kaolinile

Anethvst is a despdent to rrestucenltuTle to pale violet vdiery of crystaninequanz. Its colou is genqauy imeIlreredto result from rhe !.esnce of Fe. It iscommon in epi&emar veins, pdicularlyln crustifom bands rhere crbonate ispresent and in bladed replaceneni ofcarbonare (Plate 19). Howevd, it is notconsistendy prt of o. limird to lbeseaNocraions and h.nce has nor been avery useful gnide to textural zones.

Carbonate minerals are common inepithe@l veins md exhibit a pide trgeof compositions Md texr@s lhat cs beused to mrdpret rexrural zones. Inaddition, mod crbonale minenls may bedissolved and rellaced by qudz lndereprthmal conditjons so that rhee is alea range or quM rellaceme.r re{ws lhataid interpEtation of xtulal zones. Someothd relatively soluble ninerals such assulrates, nuoddes md z@lites also @curin epnhmal veins @d fiey aln dhibir arange of prinary and reptacenentrexNes. However. tney d not c@mon

OTHER MINERALS

Mindals otier thtu qudz de como. inelithemal velns. Then distrlbution md

a useful ald to theinterpreiation of textural zones in

Aduldla h a vdiert or ( fldsptr wnh aweakly ticlinic ciysral strncture and apseudo-orthorhonbic oysul fom. It is

enough for thei. full textural variation ro

For cubonares, crystalline and sraruldassrecates, bladcd aggEsates (Plare 28)and no$ aegegates re nos connon.Crystalline ca.bonate lorms frassivezones r$ociated yirh chal.edony in someveins. lt is.ommonly Eplaced bypaallelbladcd quartz. MoE discFre crystah nxybe dispcaed throush chalcedony (Plate16) or Eroe in .ru$iform bands orovrries associared sirh cry$alline qudz(Plare 36). B laded cdbonaF occus on nsown (Plate 28) in asociation wirhnassive chalcedonic quanz whe.e n hvanably retl&ed by qudrz (Plates 17,18,29) or 'n ctunifom bonds wher it is0ko va.irbly replaced lPlarcs 19, 20).Fine eranuh and nros .arbonare isassoc ia rcd w i th noss quar tz in.rusirom collofom bands.

ealenal rc nosr comnonly asociaredFith crysalline qnutz in na$ive orcnrsntbm ager$tes (Plare 2?)

THD TEXTURE ZONING MODEL

A synenratic evalultion of the venical ddhonzonral disribudon of rexrucs within anmber of epnhcmal veins has led to thedeyelopnenr ola rextural nodel (!ig. t).scven texrural zones have been definedlrom the recognnion ol iexturalasemblages and rhesc have ben groupedinro three superzones. Tte $Derzonesrepresenr fundamenral changes lnpEdonxrer rcxtures whcreas the zoncsvirhin each superzone de defined by.hanges Ln subsidiary minerah or rherelanve proportiois ol Extural rypes. Notexture N necessanlyexcluded ftonr anyof rhe zones but rhe anes tre naned for$e pndominantrexrus.

The Chrlcedonic Superzone (CH) isdominated by chalcedonic qulrz. Thethree zones within it ae d.fined by thererarrve protonlons of !ssociaredcatuonare or bladed pseudonoryhs afiercarbonarc. The uppemon o. CarbonarZq! Ias not often becn observed andnay be obscure ln onrcrop because orweathedng of ca.bonate. The zoneconsis of massive crysklline or granulrcarbonate with bands or nasses ot.halcedony. weathedng pns or noldsatter cuboiate cry$ds nay be presen((Plate 16) i. rhe chalccdony and nayinclude sone pnrallel bladed qudrz

Su l l ide mi !e ra1s dcr ine a d is r inc tninenlogi.al and chemical zoning pasemthat is $ in(e$al par of Buchanan!epnhemal vein nrodel (Fig. l) Ar handspecrmcn scale rlrere arc o.ly generaltextural va.iarions. Fine grains oldiseninated pyrite occrin samples *ithoassive .halcedoaic, bladed aid Dosssaccharcidal quutz. Delicate bands andparches or ve.y fine gmined sulfides,sultusalts and selenides m lssociaredpirh collofom cru$ifonn banded qudz(llate 26, 32, 34). Dis.rcre, euhedralg.ains of simple sulfides (Pyrne,dsenopyite, chal.olyrire, sphaierirc,

1 0

:

i f * !

. J 5 : :i i i :: E : q iE ; E i E: i E E E= I I a :3 E i 9 iE i ! E J

9 l

E

iE:

:

a

. E : : ,

i , q o: l e , i

= i j i :! : 1 - !Fi " !Ei E E Ii F i ;; i : E

i= iB E= ' l : +E : i i: H ! i

q E s " ir 6 E t

F ; E i

EEe

s#i$ 3F3 l; !

a i "

! ii!sirii 3c:E

E;E

9

E 3

1

rormed by prinary or seco.dary@pl&enent of the cdbonare. The ovenlltextu@ ls ma$ive lo fudely bdded.

The Bladed Zone Erades flon theCarbonate Zone by an incPase in rheEladv !rcponion ol bladed ro massivecarbonate and associated pseudonoryhs.The mosl conooD fom is massive.har.edonic qu6E *nh patches o. cndebands Df latrice'blades (Plare 29). Clearcrynalline quadz or anerhy$ nay bepresent between blades (Plare 29).Toward the Carbonare Zone bladedcubonate, molds after bladed carbonateor plnially replaced blades may ocur.Tow.rd $e Massile Chalcedonic zone tlepbpordon of lari.e blades !c chllcedonyd*reases and rhc blads are generallysm.ller a.d moro confined to bands.

ln the Mass ivo Cha lcedon ic zonechalcedony doni.ates. ln handspecimendre chalcedo.y appeus ma$ive but onpoli shed s urfa.es an iregular syirling orcrudely banded .hldcier is defined bycolour .h,nees (Plare l0l. In the npperpd or de zone some of rhe bands nay belattice bladed. In the lo*er lan or rhezone bandins may be nore regrld ddhe.cc moro like agate. Ehewhere drechalcedony nay have nos textuF in

The CnNtiforn C.lloforn Superzonelee) is narked by the development orconsistentbanding. There is a wide rangeof texrdres and ninerab snhin drc

Supezone but rhey re arnost endelydhposed within bands. Tlr Supeuone issomeehar arbitully divided inro iwozones based on the Elative prcponions olba.ds wnh chalcedo.ic md nNs lexruEsas opposed ro crysnlline (saccbmi&I.comb and zoned crystal) teatures. Th6u..er hne has chalcedonlc and mossbands doninant over clysralline bandsdd has associated moss aduldia, blrdedcubonare, larice blades md fine gralnedbandedsuhdcs (PlaF31, 32). Collorombandins is betd dcreloped in this zonebectuse ol the abundance of chalcedony.The lower zone has crystaUine bandsdonrnant over chalcodonic and mossbands and has associated needlecrlnalline adulRria and disseninatedcrtnalli.e sulfides as vtl as sullidebands (P la res 13 ,34) . Wl th in rheCrustifom Collofom Sutezone there isnoi only a chang lron doninantchalcedonic to doninmt crysralli.e qumbu1 aho a change ln dominanr qDaizcry$dl form from sacchroidal to zonedcrysrals ro clee codb (pnsmatic) crynals

The Cr t rs ra l l ine Superzone jscha.acterised by the associarion ofcrysEume qudz vi$ .rysulline aduldia,sulfides and calbonate. Chalcedonic,collofom, nos md bladed extuEs ffivirruauy absenr, bur ctustifon bands mcodmon. The crtnalline quarrz isdodinantly cler and pnsnatic but zonedcrynals and sac.haroidal quarrz arepresent locally. Withln the Supezone

1 2

there is a Cereral decrease in thepropoiions of suifides and adulda andincras in the prcponion or crystallinecrbonat intdsdnal to oyst lline qudzgoing downPad- The breal to doninantinrdstiriai cdbonale is nsed to distinguishthe ca$alline oudrz + adularia + sullidemd cry$slline qudz +crbonate zones.

The Exrural nodel (Fis. l) can beconpared with rhe ahelation, ore andgansue zonins nodel proposed byBuchanan (1981). Enpirically there isgood coopanson beNn the seneralsequence of ninerls ud dxturs dd lhisallows cros-checking vhen tyirg roe$ablnh vnical position within asy$en. Mos ocuences represnt onlya pofrion of rhe iddnen nodel ed moswell nineralised occurrences haveadditional conllexnies lelared tobMcixtion bd multiphase overprinr

In usiDs lhe overalt nodel the fu$ sep isto establish a spadal and parageneticzo.ing seqlcncc ror the deposit beingevaluated. Whft good vodi..l exposureor dJii inf(mation is available a venicalscale can be assignd to the zo.es andconpared with the scale a$isned byBuchanan (Fig. 1). The scale calculaledby Buchanan (r981) assunes boiling or afluid with an i.itial 2.84 veight per.enrNaCl, fiis is an averace for lne deposnsror vhich Buchanm compiled data tudhence is a sensible b ubnary rcfftnce.In evaluatins Gcuftnces the scale can beadjustd ro reflct the aciual posilion or

known zo.es, or adjusted using rheequadon provlded by Bu.hmm (1981)vhere fluid incLusion dara allowsirterpretation of salinny for rhe

ln nos eell nineralisd oc.u@nces,particularly bonanza veins, ore lsdeveloped in dGmte sh@h widin lordsrade or bmn veins or lodes. Fromexpedence to date, ore shoots arecharadensed by assemblages of texturethat distinslish them fmm the adjacentveins. The ore shoo* rend to bedomi.aied by rextures iroo theCrutiloin-Collofom Sulerzone andoie. conrai. brcciN wnh clasts andnarix whose texrres aho Epresent thisSuperzone. The adjaceil vein mayrpresent any or the tex$ral anes bur isEenerally linired in rems of the nunberof zones pEsenr md rhe .dgc of teatmswithin erh zo.e. Many b@n lodes a1sconsist of variably silicified andbrecciated wallro.k and this needs to bedhtincuhhd flon chalcedonic o. otbervein qudz befoe a texrural evaluaiion is

ORIGIN OF TEXTURAL ZONES

The Buchanm nodel (Fig.l)ls scaled asa sinsle pa$ boiline sy$en and fiezoning pattens e inerpetd in tud orrhe behavio!. of fluid undelgoing boiling.Sinlluly the textural nodel can beinterlrered in lelaiion to boiling, TheCry$alline Superzonc represdt the

1 3

tonion ol the model bclow the levelwhe.e boifirg r.Lcs place. The Cru$i,romr Collofom Superzonc rcpresents ftetlo phase or boilins inteNxl and theChalcedonic Supe.zone relrcscnts theinteral in which stem dcriled from lheboiling inteNal condenscs ornixes wirh

The zoning ol qDdz (and .alcne) rextuEsin genenl should depcnd on thesolubihyor and lre kinerics ol drsoluiion andpfeciFnadon of various lorns of sili.aand cal.ilc. Alrhough theE is enoughintirlnadon od the solubilily ofsilica andcalcft nr hydJothcmrl fluids lFounier.1985r) ihere are very limir.d data on rhekirctics of dhsolution and pFciFnarion ofrhese nincrals {Rimnidr & Bdnes, 1980;Brady & waxher, 1990j Dove & crer.r,

ExperiDredallt d.teftined sohbihricsofcommon silicaninerlls in pnre warc. arvaF. pressurcFeratuE. Ar ea.h renpedrure amoehoussili.a is more solLrble dft chllcedoDy ud.halcedony nore rhad quinz (Fournicr,1985a). At 2s'C in.rersed pE$ure hrslitde effeci on the solubil,ry olsilica bnr arhighcr temperarures (>l00oC) dresolubiliiy rapidly incrcases $ith presur.Below 300'C no{dnsolved salrs exccFlNlzSOa cause a slighr decrease in rhesolubiliry of ano.phous sitica Addnionof Na2SO4 i rc rcases the so lub i l i l yatldenrly thrcugh rhe fomrarion ofsilicasulraie conplex.s (Fournier, 1895a).Above 300'C rlE solubility olquxiz is

xno*n to rncEase wnh incFrse in lhcsdinity of fluids (Fournie., 1985a). AsHiSiol renains rhe dominant forft ofdissolvcd silica in acidic roneurral lluids.the solubility remxins independenr ofchanCes in pH. ObseNltions based on rhegcorhemal flnids h.ve shown rhat a1rcnperatures > 200'C quarz conb\ thesilicr saturation in fluids. Chal.cdoiy*hich has hieher solubility than qMnz,$ans conrrolling the silica santration !tlorver lenpe.atures (Foumier, l98sa).Thus deposirion of ano+hous silica,wh'ch r a condon pEcipihre in theseenvironnenG, requires high leveh ofsilica supersarurarion wnh rcsFect toquanz. This can be a.hieved undcrspecilic conditions in rho epirhemral

ln conra$ ro sili.r, ihe solubili(y ofcabnc (rnd orher ctrb.naF, n a funcrionol nor only T, F bur lso of rhe solubiliryolCOz i. the flnids and larrid prsureof COI At tempenrures >l t5oc Henry slaw connxnt (KH: Rxrio offugaciry ofCO2 and (he nole ftacion orCOzin thcfluid) increases wnh Lrl in renrperxrdreindicaring ihr t on coolin! CO2 panidonsin iavour of rhe gaseous Fhase. Beloyl?5'C, KH lalls wirh aalling rcbperaturcrhereby rcvc^ing rhe tuend &d COzsMstivouring the fluid lhase (EIh &Golding. 1963). The expedmenra]lydermined solubnny orcatciE decrcaseswrh in.rease in renleraruE (rehgradesolLrbihy) and incFass wnh norhernalincrease in the salinnt and lanial pEssreof COr (Ellis, 1959t 1963). At a lixed

&mpentue tne solubilily of calcite in afluid in eqnlibnm wirb its valos phaseindeases with incre$e in the ptnialpressE of CO2 until mcoz= 1 nole^g(segnn e, al, 1962). At a l*ed tor6lpressur, d isolhemal inc@as. in th.concent.atjon of CO2 increases thesolubility of calcite nntil sco2 = 1mole/kg and decrass st higherconcenrrarions of CO2 (Sharp &Kenftdy, 1965). These $udies shos ttatloss of CO2 and dilution are 1he nainf&tds controlling deposition of calcite,{heras cooll.g of fluids makes thcnuids nndersaturated wnn respect tocalcne causing dissoLurion of earlier

Tr?ical epithemal fluid is a CO2 bedins,pE neutral fluid rith d avehge salinityof < i 7' eq NaCl (Eedenquist &tlenley, 1985). Such a fluid, Philemoving upwards along de channelyay,Dndrg@s reversible expanslon and atsone polnt, when lbe valour pressue ofde Jruid exceedi the hyd&$atic p6su,stuts boillng (jreversible adiabaticexpansion). Along the channelway,dpnding on the shapes of thchdnlway (consricrions ed bdget lnefluid can undergo lss vigorousiftv6ible expmsion known 4 thetding(Bdlon & Toulnin, 1963). The deprh atwhich the ascendins fluid undergoesboiling dep$ds on ihe renperature,salinity and the concentation of di$olved

gases. Purc sat r at 250'C will strnboill.g at a hydrcstatic dpdr of 460 nwhdeas 10 M % .q Naq ndd wiu boilat a sh.llDwer dpth ol 390 m (Haas.1971). In conran, warer comairi.gdissolved CO2 sill sht boning erlidi.e. ar Iteate! depths. In rh epithmalenvironnent, the composilion ofsuccesslve batches of fluids bovinsupYdds is not expated 10 chang nuchalthough lower teoperatu.es of thesefluids night move the anes of successiyeboiling upwtrds. Additionally, selectiveed pdial sealing due to silicincadon ofrccks a1 rhe shalloNer levels vill alsonov the boiling bne upPdds.

Below the imediate boilins zone, wheEthe fluid cools sradually by Evelsiblexpansion, lelarively sloq condnions ofprecipitation dominare and rhe silicasaturation is contolld by quartz.Threfore this zone is expected to becharacterised by the deposnio. ofcrystalline qudlz (supezone x) shichcould be acconpanied by bas m.tal

In the zone of boiling miLed by iapidlos of volatiles, increase id pII andcooling, the condnions ol deposition rm!.h nore .apid. Rapid ioss of COzcauses pecipilation of calcne, wh@aslncrede in pE Esults in de fomaiio. ofpotash feldspd. Sisnilicant cmling dueto adiabatlc qpdsion cm ruke de flnidsup.rsaruraled vith respecr to chalcedonyand amorphous silica and cause

1 5

amorrhous (sel) silica ro precipnate.Rapid rares of cryshllisarion re ahorer]eqed i. rhe type of potash leldspd(aduldla) chaiacte.ised by a hish deEeol disorder in the oystal symmetry.Zones of crustifom+collofom bandedquaitz very common in the SuperzoneCC, Giiect Epeated episodes of boiling.Brcccia veins with aragmens of edlir-roined banded quartz also indicarcsuccessive boilineevens.

If the adiabaiic expansion is inrensi!e bdthe fluid .ools while rapidly ascending rorhc surface.lt can b4ome supesarumredenh respeci to anoDhous sili.x anddcposn gel silica ir rhe lorn oa sinrca orsili.ify ihe toou\ groundwate.ich rockgenrati.g rhe silica cap connonlyobsded in nany epnhemal dcposirs.

Experimenral $udies on rhe .ryixlErowth of calcite have indicared tharcalcitc groving in fluids nuted by fdl inthc acdvny of carbonote ions have acuterhombohedrll shapes (Kirov cr al.,1970). Thererore calciE deposiring due obolling and los of COr and a$ociaEddrop i. rhc activiiy of roral cdbonare &d,ncrease in rhe acrivity ol calciur arcexpecied ro lbrn massive eranulRraggregates raihe. rha! rxbula. (bladed)foms. Rxrid deposnior following rapidnucleadon pill also assisr in rhe fomarionof nne-grain d lmnular aggregates.

In geothernal syiens shallo! levelsendked by a Rell-dcveloped zone ofmixing. ln a large numbe. ofepnhemaldetosns nixhg bctween vo difercntlluids has been indicated by fluidinclusion !.d $able notope *ldies(Eayba er ,1.. 1985: Iledenquist &Henley, 1985), Within georherdalsy$ems, rhree end Dember fluids havebeen rccognned (Hedenquisr & Henley,1985): COr beanns chloride nuids (henaln ore-.ftying fluid)r icrn he.rednereoric nuids or acid suuate-bicdbonarecompositioni and nixed oxidising

rn d'e cpnhemal enlimndnt rhe initillnixidg of near neural chto.ide fluidsnsing ratidly afrer boiling and cootingcan lcad ro the formarion ofa silica cnpdue to silicificailon of n\e ncronc rareFrich aquiferrcck.liis silica cap, dne tohiSh porosiry and fra.turins mainrainsmxss and heat ransld bet*een rhcmcreonc and nedrEuhl chloride lluidsin the earlier nages or ns fomarion.subscquent boiling e!ents resulr in rhecondensarion ofrbe acidic Eascs in ro rhecooler, oxidiscd meieo.ic lluids c&singargillic and advan.ed sgillic alrerarion.ExFenmental iudies have shoen drarqlafiz (and amorphous silica) in acidnuids at 2000 io 350'C dissolves andprecrpnares very slowly (Fournler,1985a). The prese.ce ofH+ ions in acidicfluids aho inhibns the polymcr(arion of

dissolved sil;c!. Theiefore n is posslble$ai the acid sullale bicrbonate fluidskeep silica dissolved, the oncenedon ofwhich in the rilids nisht additionallyteep on inoeasing due lo a.gillicafteration of silicales. causi.g exrFnesupersatrralion witb rspect tomorrhous silica. The fomation of silicasulfate complexes might be e addnionallactorincEasing silicajupcnatuation ofrhe flnids. Mixing ofthcse acidic fluidswith near-.e!tral chlodde fluids (pHncuralisins) wilL precipitac ano.phoussilica, recry$allising into massivechalcedony (Supezone CH).

Swe-one CH is chdacterised by largequaflz blades Fplacing carbonate. Thcprecipiration ofcalcite sh.llow lerels isvery problenatic, ddnly due to rheretrogdde nature or ns solDbnny. It hrossible thar nixing of CO2 released due10 boiling ol fluids ar deeler leveh vnhcooler meteoiic flDids nighr causeprcipitiaiio. oa catne due b an incEasein thc roral crbo.ate concentation rD thelluids. At loser tenpentures nost of rheptrritioning of CO2 soes in favou. of lhefluid phase. Theelore CO? dissolvesnoE readily to give F2COr vhich atlower tempenlures dnsoclarcs noreintensively,leading to an lndcasc in theactivities of HCq and COI 2 ions. Irthis htue, then rhe expenmennl studiesol 0

1 7

gas will eadily dissolve a.y cdbonatebecause lhe isothernal solubility olcrbonate in-eases wnh increase in lhe

Moss and nicropldnose textues fomedby rc.rystallisarion of anorphous sili.a

in rhe massivechalcedonic and mos ch alcedonic zones.Expenmetal studies have indica'ed drarline, hish emperature, hish pH, highsaliniriy dd the lEsen.e of dissolved Mglavor rccry*llisation of morphous sili.!(Four.ier, l98sa). The Fludes of hotvapoDr, snh COr and HzS released dueto boilins, passing thJough rhe colunnsol earlier prccipirated silica could be agood source of high lenperaturc neededfor .ec.ystallisarion. ln addnion, 'heresidual fluid which is Elatively moresaline and has a higher pH .oDld a\o

DTSTRIBUTION OF COLDGRADD

In lhe Buchanan nrodel rhere de specincinteNals lhat hod base md precious ncr.lmineralisation (Fis. l). In rhe rexturalmodel the precious netal inteNalessentially coresponds to lhe Crustifom!Colloforh iextural Superzone and thebasenetal iDtewal ove.lilps rhe crysElline> noss + chalcedonic zone and thecrysralline quanz + adularia + sulfLdezone (F lg . 1 ) . In p rac t ice rh isgencallsation holds very sell. Mosimporta.dy, the Chalcedonic Supenone

which is !m!ly nineialned overlies dreweil mi.eralised Crustifom CollofomSuperzo.e. In mineralised systems rheeenenl experie.ce is thal sdples fiomlhe Chalcedonic Superzone carryanomalous gold grades whdeas samplesfron rhe Chalcdonic Superzone inp@rly mineralised sys.d de barcn.

Poor assays of samlLes fron 1hecrustlrom Colloforn Sup.rzone aregenerally dis.ouraging for rhe sy$cn as awhole, but orc shoot characrerisrics,laniculrly vein breccias, should becmfuUy cneck.d. wnhin the Cn$ifom-Colloforn Superzone, subsidiarytextures, paiicuhny sunde b.nds andmoss or needle adnldia, r shonglyassociated wnh hish gmdes in a nudbe.of studied systens. The ideal sample fo.g.ade has well developed @stifom andcollofom bands, wnh or wldout braciarexture, but wnh good suuide bands,moss or needle adulria Md s&chdoidal

Assaying of .haracter samples hasdenonsrrated rhar within individualdeposns rhde is a consisrenr grxde raneelor each lexture assemblage. Forcxanple, at Wool8ar the Nsenblagebladed cubonare + bladed pseudonorphs+ nasivc chalcedonic which char-acterises rhe surf&e exposue ol the ln$World vein rftly has grad better rhan0.7 eh Au. ln condast, the asemblasectustifom + @Iofom + zoned c.ystals +mos aduldia + sulfide bands intersecrenin drill co.e in rb sdme vein typicallyasrays bette. ihan 4 g,/t Au. Chra.ter

satutling of rhn ryFe can be used toenablish a gr&lc disbibtrrion model $ar suseful for evdluaridg unrc{cd vclns orpafis olveios vithin th sane syscn.

APPLICABILITY OF THEZONTNC MODEL

txMal model noE apprcprixte to rhesesv$enN needs to be e$xblhhed.

REFERENCES

Adams, S.F., 1920. A ni.ros.opic studyofrein qnafiz: Econ Ceol., v. 15, p.

Bdo i . P B. l r . & Tou lmin , P . , 1961.Sone nechuisrs for coolinghrdmnremal fluids: U. S. CologicalSovey, P(fessional Plper, 424 D.

Bradr, P. v., & Walther, J. V., 1990.K,d.ri.s.f qlartz dhsolurion rt lowrempeftttres Chen. Ceol., v. 32, t.251 254.

BnchxDm, L. J.. 1931. Pre.ious nreialdepois associated *ith volcanicenvtroohents in .he sourhwen:Arizona 6eol.So..Digcst. v 1,1, p.231 261.

Dovc. P. Nl. & Cerlr D. 4., lr90Krtre!cs of quaiz dissolLiion ine lec t ro l r re so lu r ions us ing ahrdrorh.rdal hixed flow reador:Ceochnn. Cosnrochin. Acra, v. 54.

Dowling, K. & Mornon, G.lV., 1990.Applicnrioo ofqudz texrures ro rhcclassitrcarion of gold dposirs using\o ih Queens land exsmplcs :EcoD.Ceol. Moroenph 6. tp 342355.

l l l i s , A . 1 . , 1959. The so lLb ihy o fcalcite in carbon dnJxide sol,ri..\:An .J .Sc i . v . 25?, p .354 365.

lll(, A. t., 1963. The solDbilny ofcalcite nr soditrd chldnde solnion\ arhigh tempenius: Ad.J.Sci.. v 261,p.259-261

Ell(, A. J & Golding, R. M., 1963. ThcsolLrbiliry of .arbor dioxide above100"C in wa(er and in sod iunrchlonde solutions: An.J.Sci.,v 261,

M.s of rhc eradplcs used to e$lblishboth Buchanml (1981) hodel and thctextural nodel preseoted here would becla$ilied as dlldia scncrc rypcveinsinrlre schenre ol Ha-r,ba 4 dl {1985) F.racid nnfarcdeposirs rhe mi'eralnatun (more co.rmonly hosled in silica sullideEplxcemenr bodies and inegular lodesthan in dkretc simple leins. The reinsthai are preseoi tennlly hrv. onl! ahniled ranee ol ftxtures co.rprnble iorhose iir Ihe lower hall ol rhe nrodel.Sinrilarll thcr. dc a nu b.r ol nddicdve in d is t r i c$ in the Ph i l i l p ines ,Iod.ncsiq Fili and Colomdd *h.r theftis r tredamio)nce of cry$rlline aodsx.charcid!l quatz, nore carbonaresultules an{l !ulfides io crusifon aodcockade textuEs, les adulnia and l.schnlcedorlc, bladcd and noss tcxturs.The co'nnror eeoloCic learures of th.seoccuFefces n a seiiinE ir atrdesiric$rarovoica noe s and/or a closc !c. cti. I inkbetweenveins and intennediare to alkali.inlrusions. It is vell doc0nrenred rhrrdany geoihemral sysenN hosed $ardcsilic smtovolcanics are hiEherrente(ntre, hale a Sreater nagmalcfluid corponent and havc a diffe.nlhtd(nogic reainre compded ynh |hencouoreDafis rn rhyolnic .aldcras (e g.Henley & Ellis, 1983) These differencesaE reilecred r dr lcxruE bd mine'rlogyof th rssocirled epirheflml venx. A

t 9

FoDmld, R. O.,1985a. The behaliour ofsilica in hydrorhemal solftions: i.Berser, B. R. & Berhke, P. M. (edtCeology and geochemisry ofepnhmal syiens. Revlews in Econ.Ceo l . v . 2 , ! . ,15 51 .

Fournier, R. O., 1985b. Carbonater in \nor t dnd d . tus i ron n rheep rhcnr len \ ronmenr i r le r re rBR.& Berhko, P. M. eds. Ceolosy andgco.hrmisn o fen i rhem sr !ems:Rev iews,n E lon Ceo l \ . ) - o . 6 l

Haas. t. L., Jr., l9?1. The fied of

salinity o. the mrxinnm (hrnalgradien* of r hydrcthemrl srsrem xthydrostaic pressuft: Econ. Ceot.. v.

Hayba, D. O., Berhke, P. }'l., & Folev.N ( . . l99 i Ceo loq t r . m nemroq icAnd geo!hen n1 l chdr i . re r j ! s o tvolcanj.-hosted epirhchal Dre.iousncr , ldeoonA nBercer .A R , !Berhke, P M. . (ed t aeotorJ ,nd8eo!henikrry f epirhemr \1sem5Soc i r ry o f E .onom e Ceoocrns .Reviews id Econoni. Ceotog!. y.2p . 1 2 9 1 6 8 .

Ited.nqui$, J, W., & llentey. R. tV.r98s- The.inrpoflance oi COz onreeang porni neasur.nenrs of nuidinc lus ions : Ev ldences f r .ngeothemd sysens and inrpli.ationsIo. epirhernat oE deposnion. EconCeol., v. 80, p. 11791406.

H.dey, R. lv., & Elln, A. J., 19E3.ceothermar systens, ancient a.dnrodern: Eanh Sci.nces Re!te*.. v19 . p . l -50

Ki rov , G K. , Yessc l inor , L , &Chcrnova. 2.. 1972. Condnionr .ffomration of calcire cry$ah or hbdrand acute rhonbohedral tabia:Knnal and Technik. v ?. D. 49?5nq

Leach. T .M. . 198?. Pet ro tos ica levaluadon of thc colden Plat,;,nnCent.l Exrendatwtite Eooe reas otthe Cracow Min ins - Rec ion :Unrub.report for Cosaln Ausiralia

Lrd., by Chanered Mi.cratosicat

Mo6c. I. W.. 1983 The kinetics ofcalciun carbonate dissotution andf rec ip i 'a r i .n in Rceder R t , (ed . )c : rbonare \ mincr l loev Jndchcoistrr, Rcviews in Mine;losv. y.11 ,p .221-261.

Rlniidt, J. D., & Bmes, It. L., t980.The kinerics ol silica-*atd Erctions:Ceochrm Cosmochrm A!n , \ 44 .p 1681 1699

Sander, M.v., 1988. Crysaltisation andrecrysra ll is arion of solrh zoned veinquaflz cry$als f.on epirhe.malst$ens - ibplication for fluidnc lu \ on \h rd ie \ E lon .Cco , v 8 t .

r l 1 0 5 2 - l r 1 6 )Segn i t , E . R. , Ho l tand, H. D. . &

Biscrdi, C. J., 1962. The solubiliryoi carcte 'n aqucous solDrions I.Thesolubihy of calcire in vater berween75 ' lnd 2u0oc i r CO) t fesu ie \ !pro 6rr zrm Ceoch m Co\nochrmacta, v. 26, p l30t 1330.

shup, w. E., & Kcnnedy, 6. C.. 1965.The sysem CaO Cq.H2Oin rhe rwophase reeion cllcite a.d aqueous\o lu r io r . Iour . o t C .o loe \ . \ .71 . ol9 l 401

WeEs, O., Yee, A., & Tsao, L., 1982.Equn io is Jnd ryne cu^cs fo rpred ,c rnS rhe po t l ,mer is i r io i o Iamorphous sili.a in eeothernalbrines: Soc.Petrot Eng.Jo_u.. D 9 16.

T-- --

2 0

2 1

P L A T E S

PRIMARY TEXTURES

PIATE 1. MASSIW CIIAL@DOMCCryF@rystaline quanz (chalcedony) wlh a nasslve fom, tylical wdyluste and conchoidal fretue, Binurr. Nonh QueenslId.

Plat 2. MASSI\aE CEArcEDONICDdse hedmEmDus agEEgate of crr?looy$alline quarE vlth locd sphencalor banded domiN ed codsd (@ystallised?) patches. Qndz Hill, Nd6Queenslffd, oosed polr.. f.ld of\re$ 5.4 m.

PIATE 3. BANDED CHArcEDONICDelicalely coloui banded cnalcedony (agate) with lodl @[ofm bands uddoss'cutting cryshllire (conb) qufz veins- Fraemenr in vei. bMcia,Qn@ sin. Nonn Quensldd

Plate 4. BANDED CSALCEDONICFibrous intmal habit with fibres onented orlhogonal lo band frdgins andopdcal continuity of fibres botwcen sDbbmds. Typic.l chmcter of bandcd&d some massive cnaledony. Sm sdple as Plate 3, Qudtz Eill, NonnQueensland; cDss lolds, field of vier 5.4 .fr.

PI'tC 5. SACCI{AROIDALMassive fine exained crystaUine quanz aggrcgate eith the appeance ofsDgd. Crain sizc is vriable and is nig igntd by the corser teminaredcrystals in the caviti$. Antanok Mine, Bagdo disFict, Phnillirs.

Plate 6. SACCHAROIDALInlerl@ki.s subhedral snins ol n* unifon smin sirc. rncal find EEinedaggregalqs &t d .ucleii to crude rosettes of elong$e 6ystals- Sde spcirenas PIaE 5t m$ed nicols, field of viev 5.4 nm

PRIMARY TEXTT'RES

coMBce& b gi"y qrrn/ odrd co1\nrrg oi righ. ) p&k@ subpm tel slrd soner ieo perpendq i r ro de bard sd ' s j rosr jeapp. tu tceoraaonb.LD .E \ r. ( ef,henJ"l rtm mLio -s d or cr d only rborbn .ide of ra. band)msurm.!orb.m brdrd veil wir chalc.donic md ^ ombquuz tidds,vuflz H , Nm uueenslan4

ZONED CRYSTAIJEuhdd l qud. c ry$J" .w. rh a l remar ins c te , .dd n ,UrJ zor , par l te , bsrcv necry ,a r lces [4 r lxJ uone"yecro*d .d * i . f t rd i1 lu " .on \ . \oEoe pde-pL lreIm.r\!:n{ nno !f ot rhe D,d ud rhe rFdce rhaDeddtnab r(med by cmdeddol rd $af LF.-*1ao,orrn"5,.ati pd;f amsuromqumvejn. QudD HiU. Nodh Qu*n ndir '

COLLOFORM BANDSfnebMdedchJledony wir , boEyodal rom ir crcs-$.rion @ a Ldre!5e pan \rd e lnL.\ rhe N? cat tomo"chalfdonJ in.turotom buoivum Hxr, Nd Qu4nnMd.

PIAT TO. CRUSTIFORM BANDS

i'mt*rft ',"9';;r*!m""'xyliH:i'itr:Jgy:;","r.?*:mdety buded wnh mqs md coru q",,c. s"ot rot", pi;t"s. M;", N;;iiCRUST]FORM COLIOFORA4 BANDSclas-.! *holA or$e -tu.'rom,d remaDlC, ro aUotom , boryo dal)Mds.onnd- en chddcErisd. o"eoii-ndt \; n. BtLedrdqrureba;dsftcrdc4oly_ gF\ Md pllpt. brnds.onbqu&u r.ocatq /on"d cry.D .J andftmj yeltDq bdnds adu-drir. Cno.a1 M;e..a\a. Sa;pte cof.sJ ot D J

COCIGDECai r fo r b rd . o f conb qud/ ch edony Md sL tnoe i ov^ ,c roqr rgwo ock.ru orhs vein rraenenL Tr"ica ot v.,n bFa$vmred qr rh tu . j ro - !o |o lm Lc 1 , . Ten e \e l .C .6 |nn&r r re ,Ja 6

RECRYSTALLISATION TEXTURES

Massive to crudel,v banded aEgregateappedance simild ro mo$ retetation.JMD l7 l a t 27 . r .

Plate 14. MOSSG r , p " . t . . a " ' . o s p \ e r o d , ; , " _ e d D J o . r ' . : o 1 . o .r p r n i e . l r . . \ - o s f ' . r h e p l . . l c p { J r e o - c o s r a , -r , r l . " ' ! o , . e d b ) . . - " r . - y , l l q r ' / L I p r r t r r T . e n e . -oriEinal sphcroidir rextuE. Pajiirso, r-oih eueensland, aitl hoic JMD 173 atd 6 i o r T D o l r - d g . o \ e . ) a r ' .

Pl,te 15. MICRO PLUNIOSEFerthery appeence in doflains *ilhin qudz crtnds elared to fomdion otcrysallircs do ng recryialtisarion of .hrlcedony. Crand Cenfial Vein.woolEuNonh Qdc.ndrnd; cossed nicots, fi.ld of view 5.,1nm.

t l J rc 16 ,

REPLACEITDNT TExTtTRES

MOLDSv d

. i \ - . l J " J o 1 / , ' . p o l e o . , t . . \ i. t r b o r - ' l o a b . f l . - r ? . . 1 ,

. ^ . . e n . \ b " r r J o r o , p , r \ . t . e or ' F e r .

. r t r o r b J . J n / o g d F r n . d e ' o f v & o d - . nprocescs Lo$ World vein. woolsrr Nor Otre.nnand.

LATTICE I]L{DEDA net*ork ol i asdi.g btldes $irh polyhedral calnics tanly tined byludz cry$\ This ExruErcFr4ents ei'hddimr peudondFhs or o.icinjt\ J . d r d b o r r - o ' D f , . e p . n - ' " o r r a . i v e r ' t 1 e ! - N , J r r . , s

c - . \ , g " ' rL . r p . , - o o . -o b r . , .o t , . .o r o lremJin,ngcdLonrr Bimuna Nofl h Qlccn\l Lnd.

LAMCE BLADEDA net*ork ofinrersecrins blades where each blade consi$s ota senes otp s , " - . e 0 . . , - J o / . J n ! ^ L r y . o t r e \ 1 e c D . . a l . . , o, , ) s l i l r F \ d . . L 1 s 1 ' - r ' l / . b o . . . . . 1 d d o - ? p n o , . l ' d , . or \ . n q . e . r , d - . . I k - B . m L r ' . \ 1 1 O _ - . J . - o s { n , o . .

of sphroidal grains vnh an overallPajingo, Nonh Queensland, dill hole

l '

REPI-ACEMENT TEXIURES

CI]OST BTNDEDiiJ"i ia"'mJi' u"a,p*i'.m bv coicntationsof idllntier nthd $miilii'iii iiiri* ".Jlidl," "n "1 ti,d:: qaq*': qq,1tl: !I,F:sl:Li"J*" :ip.l.J tv'",,"'. prcssrs a bladd tom and h_ gt ' re\ti nc-{' emenr ( ur"d$ i$ (oncenmuon o ' red a.d )e l lo{ on or ro 's Kepr#,i,-. i: .-i"i .ivra t"a:on or rhe io.actnr cN'fom bdta wh:cl1"" ':ns me} nr'ma rfd,o 'r'ls w@'ed Nonn QLans'drd

PISI 20. GEOST BLADM' "' -' l:lng;'ll:':"1:.:l:l;,q:1";.1 "u:rsrHfl 33fff ,li;i'jc;;; a;;;i v.:' woorgd \onr- Qrrnian.. co,red n'ors rie d olvlee 5.4 lm

?ARALLELDLADEDi i "ua u,a*orq ' * " e," ' .ed i r srcD { 'hr l rsd 'acer 'croup'hdt5d lnq "n r onPn . "do , B ades rpE*1 r ep lace r " ! a lo lg t rL rLpk n rF rdi l i " i . " "L*" " ' t . . r * l to /se. ; 'bordre sd r ' Lanel ls" i1 h 'i * ro i_ ' .0e " uor ' t i . to t ed ia l ( 'esva8e r ro inse 'e r r rsse6ra 'dui,,ipioii'J L.* p..tl.t . ' Bl,d" 8rc!p, derrne rte onsinal 'odeFausor m6silc.dbonde Bimum. Nonh QUeeniano

PAR,{LLE!-BLADEDe"**" i " ra** r t^ ,1" . ns Dr lerd onenauol n oddl le l r 's r trdduEn eoire ortrr' *ts'en t6 Pming"onespord ro basd orlronilii','e.i" i*b".:" e."i", d h"s bren \ompeFlv Fpl&ed bv qJanTiri...iircs"p. .t .*i . "ple A Plde 2l BiUm Nor\ Quee' slrd:so$ed nicols. field ofvLew 5 a m

I9,**,"*-," "'''. n",n+o e rir"'. rviriei rd(sts nsm{dom.ol-o.oi d;dad ,rddz cavrries ler m h g\lic\red b) g'ndrng po$der;ii;;on d $mi rlld q d/ ald {dorrre ' cg*dns rhev E!Er-wedndd adL lr'ia needre. d".onginJlv gE$ i ' rxe bud"d oldu r'JrlgoMine, Ndrh Queensland.

MOLDii-* *. *. -a p*"e. l.- 18 bolnose'o asd-ecarA o elolsde fineqL@ CrdnsoFd tFseFeo d lined rn.Ll\:or rtrzone( radse q 'drziui.. ?u' 'o.. toi.l r "onro:" rm ni.e and rrt sr'n' ls qre sd8asi#"1iG;,!;;";0,." "n oiaddrdia n.@," bv q' ru-ard-od'ualf, F;;;;J ;p.*..;. . ".,h-rinc o -nailine .dd dir b' m r -ri eii;; ;;pLe aJPbb 23, Pljingo Mine, Nolih Queensland; 6o$ed nicors

OTHER MINERALS

ADI,'L-ARIA!,r,i- o*ov"l". -,t-a: r!( ri om Dalds $irh ch'i'edonv 'orb;;;-;i;;;li;;. ML rhpn^e bec.s rooe rr arde'r" Gorden Prarea-llrre. Ctu ow, Queensland

FINE SULPHIDESi,i.-ana.rtlo* ma, t ca a. I d m r l trd EoL _ nen i rde'i e l oq,r.*&r*" 0t"..,, ".tg "'oacruqJom !o lofom,bond rlotr'a cenrd; ; ; ; . ' n , ; i # ; i : ' r ' e n u : " . i a e ' a e a n o ' p p e r ' c o d e n v e I o d e

Plltc 27. COARSE SULPIiIDES\er b.e.. i" cl, 'wi \ Dmd ano orlade o"etgoY \" of(od'e cE'rdrmsj.e,9yflF sp1d6re galaaard ombo d ( rcur Mre rava

CARBONATE LATT]CE BLAOES. i rnorro. n . r ,e , . reu l .ae"o l .aL .vpurre! b !poblenJal .aut ie .i r , i i . i i " , ; " t * r " . t ' ,o"a ouJ, / 'PLG 17 ' n d ' e v conpr6ble

o ie 3 e a! , Pse rdonorPl ox;;di Mrne. C.romddel , Nevzealand

TEXTURAL ZONES

' '-" -

M::i ;.i"'"-... qlm/ $ir' qe I de" ooo l'ru'e brJdes drd pddllel" " i i ' . i r i , l ' . . r ' " l ' - * . 'o . led ry iL i ieqds / i1 losdha l f /ge / l;ndLry .Ld . i requ iz r r i l roLr i t ' t qwo ' l $oo lBd

Plat 30, ZONE CHtu' ' - _ _- ra^* JFl*ao ' qddz * h t rsr ' t !$ i r l in t 'o ou oand ' r 'erw le f t )ffd.ear ] bai"o nilq rclon ngt ' Lor $o' d Woolge

TEXTURAL ZONES

ZONE CC@Glstifofl and collofom bandeit qndz with budr dominated bv nossLAue ((r!m. Di*). Bvd. of chal!edory (srey) ud zoned q' dzryqalsDdk .e;ms beiwee. bards releserr weth.Fd { lr@' lvpical orhiC}EEde oE. S.ot L.oe. Pai lgo. o,r$ole tMD 7l 21 0 m rJ gd r ore I d)

zoNE ccCrosdfm collofom with b&ds of saheidar-conb qnartz (whne) yithdjsseninated sulfidesr massive lo no$ chalcedonic quartz (buro; nosaduldia rc em,; dd sl!fide s 'lplo\al pdings 'b'act\ lt8\ grade At AgSe o( , rL f iUno lapr - . Sample (ou i ,Ps) Jo fn Dow \ewronr '

BRECCIA IN ZONE CCsaCLass of @srilom-collof@ bmded vein quar.zjulflde (entie and ulpdnsht) and veined dd siliciied walr@k 0ef0 overgrcM by hstifom bandsoiirorors chalrdony (srr, and ecch@idal qdd/ lvhiE). Oe mr' scorrLode, Pai:neo,.ln I lol.; tMD 24) arol5m(7q2 M A' over' m)

BRECCIA FROM CC xadTRANSmONCrlasts of siDcified v.llrock (nght cent) dd sacchuoidal quar'tz sulide(dqhr lrper ovsso$n bJ ru.rJom brd' and celadeso'mn"d qLMzda dl;axme adt lri, Colo.n P.daL open n't, Cra ow. Quers|mo

ZONE XsMuldlhase, crudely cruslifom vei. consisri.g edirly of dned qudtcry.@js d d os. sran -l& r l '.tu (pfalri.e, prrik. gdlem , t al( opyn k\'S'lv?r-ba "meral or I e.neidll) ro. Bo.o or.. ldrdo v"in. San IranMountains, Colorado. Smple counesy ofD.J. KiN&.

PIat 36, ZONEXCaCrysraline conb quanz viL\ weal mstifm teaturc due b nilky-cledva;ction tr quM. CirbonaE :nfi l i1 vug. 8tr1 o! low sr ade 6ne. ScolL !de , PdrnEodr i l lho le JMD 2J1d 20n(064E/ 'Au@qI n )

ACKNOWLEDGEMENTS

Thisrolume was onginallt prcduced in 19q) by th aulhon for the Cold Resemh cotrp arJanes Cook Univesity as pa't of AMIRA Eoje.t P24? Epithemal cold Deposirs in

The clasification and zoning model \eas sy.rheshed from rconnaisence work on nuneronsveins andsample suites (C.M.. D.G. &N.M.Tate)and detailed studies on deposirs (R. Bobn

Scott t de, Pajingoi J.Digweed woolsarj R.Pone. - Pajingo oubide lodesi M. Wo6ley

Acces to deposils, ptuvision or snple suites and nndcial s$poft for the ovei.lt researchooie, ra. p!\iden rh6l"Ir qVIRA b) rhe lolo/re.omprn.e.

Aberfoyls Ltd Ausralian Consolidated Minomts LtdAzlec Mning Conpany lrd Bante Mounlain (Austmtia) lnc.Carpdnuna Explomtion Conpany Cenr,al Pacinc Minmts NLChevDn Explomtion CoQoarion CEcow Midng vemureCRA Exploctior r\t Ltd Clprus Cold Ausralia Cor'omtionDalrymple Reeurces NL Elde6 ResounesGeopeko Golden ShanDckHunterResources K*laweeKid$oncoldMines Merda Mnenls NLNedex Pl, Ltd Newmoni AustmliaBilliton North Broken Hill PekoOtter Explomtion PancontinenhlPlrason Cotd |.ly Ltd Plac{ Pacifi.Poseidor Ltd RCC LtdRosMiningNl RTzW.stem Mining CorpoEtion

The onsiml edition was q?ed by S. Waren and nocked up in de ttintery at Jades C@kUnive6ir_.Thants also to Ja. Morison and Nick Tate for tle coler design. Al1 this sDppon is