CONTENTS P,d.".. .............................. .
i,'
1. lntroduction .......... . ............................. • ........................ 2. 0'·~'p,il1til1gcri t ~,i. . ...................... . .................... . ................ 2 2.! c..""a!51at,mmt .. . ........... 2 2.1 Fi ... t onl<" ",t<,,;a - co'ifid,"u biliMillg ................ ..... ........... .. .. . 2 .20 M il1<"al supr'imp",MI ioll - srqu"'lial úifill . " "" ................ " """ ........ " , ... , 2.211 Stmct,,,ol,ul,,,,impqsilioll' cross Clmillg "'·;IIS. br«cía ........ . 2 ,3 ~olld o,du erilma _ SiI,p"iall o,"''';lIg 2.30> lI·tismole/,os /v1l,,,,"1I ,,11, ... lioll allá i'ifill compoll"''' ........ ....... , , , , , , , ........ . 1..31> 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\'<'S ....... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4 3. J BrO
,
Slqumllal i'ifill. "" .... ". "" ... 5 T .."tur.... nd Probl .. m. PI.tes 1-3 ........... , , ........ • ............. "' ............. . .. . ~lt 5. Fi,st (},d e.nite ,i,· , Iro,tu.,t ,u!,<"i mposi tiOI1 .. , ...... • ........................... erOSó Clllling ,.. ./ock" " ,k sl)ll,.,;. T U lures .nd Pmblems PI.tes 4·lt ............................................... .
i". -
" t2·l7
ord ~ "rit .. ri.· s lructur.1 superimposi lion ........................ , ................. 28 Brt«;a - f,ag"""" of <,o,ly slog' mill"alis<>ljoll coli loi"rd Willll" 1.lr, stag'" 28-35 T u lu' .. s . nd Probl em •. PI.t.. s 12·15 ........... , ........................ "...........
6. First
7. S.. cond orde, "i terí. . .............. . S".pidoll a,ousi"S. Parolld Ol""p,illli"S ,,,ills. IW",olio" ",;.matc/tillg, í"com;,I,,,¡ . lIuaUolI alldfe' ;'ifill l'l.tes 16-22 ..................................•
srq"'""". allrralioll of ollrraUolI, . . ..•. ••••••• • •••••.
8. Acknnwledgemen ts 9. Rd.. ",nces
.......................... " .......... • ................................ 5 1
PLATES St . r.'riel hn min~, ""., In'ineb.nk. north QU""..,I.M, Seoqu
A~.".lia.
2. I'.¡ingo gold mine. a..rlers T"",.... ,"Si.,.... north Queen>1;rnd. Australi. (5<'<>11 t.<>de). Seoq"." ti.1 inf,U - .pither"",1 OIyl<. 3. Teller SOld m,,...,, Tel!... , W..'em Austr.le., Au,,,. I,. (M 10 R""I), ~uenh.t ¡nhU. Stnxtur.1 .up"rimrosition _ eros> cu.ting ,'e,n 4. Kidston gold mi"", Eina:;lcigh rcgion.. north St .... ctura I sUp"rimp<»ition,,·ei ...
~I.n(t
Au,tTal i•.
5. IV• ..., ... ",.d·. ''''' mi,...,. C.,ntur)' "'Si"", north Que<-nsl.nd, A"",.li• . Struclur.1 .uperimposih",,·,·.ins, s....p;.,ion arous;"s _ '.y"",'rk inliU. 6, CrasbeTg rupper.gold mine, Ertsbe
9. )umna tin mine, 1"'i1\l!b;ln l , north QueensLond, A",,,.li • . Struc.ur.1 superimp<»,hon"'eins, Su.pidon .rou.ing _ ""Mering «TIIt.1 infill. 10. Unkno",n tin mine, E,,·.n Kanga"", I-lill. tinfield, north Queen.land Structural superimposition·"ei"". pa
Ctu ... l.uperimp<»ition-\'ein, brecci., ]l,
l>o,;r.eti gold mine. K"h'on di.trict, Charte ... To"",, .., not,h Q ....,... I.nd, Austr.Ii • . Structur.1 .uperimposition _ bre
13. Ra,·..... wood gold mining di.,riet, non" Qu""""I,nd. A,,'tr.li. (A~ 2 ,'e in, C''P'''',.ri. Gold) Struct"r. 1.uperimposition (000 mineral .uperimposit ion) _ b~i., 14. Mi>l. l . tunss'.n mi"., Em"ford, north Queensl.nd , Au,tr.lia. Stnxtural .uperimposi'ion (.nd mi""".1 .up"rimf'O"ition) _ br, brecci.
hnfi~ld,
norlh Qu"""'land, Austr.li • .
16. Ra,'eruwood gold m;n;ng di".;"t, north Qu..,,,,,land, A""cali. (SYC I'it' C.'!"'nt.ri. Cold). SU'pido<> .rousi ng - romp lex o\'''rprin'ing. parol ~el ''''cli" .. ion, ...... ld 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",>cl>.nk- north Qu<."-""I.nd, Aust"li •. Su.p i";on a rousing - inconsin
s....picion .rou.ing - i""onsisten' .Ite,"';on, comrl'" o,'erprinting, aUe .. 'ion 01 .llerati"" $t,,,,,,,ral .upenmp<»' tion-, 'eins. 21. r.gmont. I•• d·.i"" pros¡>«t Cloneu")' rcgion, north Ou""",I.nd, Au't,.lia. s...picion .rou,ing _ inronsist"'" .I t",otion, oUeration 01 .I "'r.lion. S'ruc'ural sUp"'i"'positiOl1 -,'.ins. 22. Tick J-t ill g<>ld mine, Ooncurry rcgion, '\Orth Qo.,etn'll.nd , Amt .. li • . Su.pieion ",ou.in.!; - . IIOrotion 01 .I",wion, la ye''''''trol.
1 lNTRoDuCTroN
M I,aelu,ing, a,i", Imm ~ny
01 ou, co"ceplS concernins lhe n~lu,e 01 h)'drolh..,m~ 1 syslems a t1d thei, ,eI~tionship ",i ~h 'oC< lh~ Como",n ob",,"'.lion lhal hyd,olh",mal fluids """m to p, ..dpilal<' d ff~,ent
m inN,, 1 ~=.",t> l~ ¡¡",,~, diiie.ent time> _ P.~~l i c~ ty """'y n,;n",at dep<>$;' 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<><]u~nc~, slteh as Stase I a"d St"S" 2. The pro« -ss 01 construetins a time "'-" lair lo "ate thal until lhis a,]'<-'Ct is "'e U "od~rslood, ao)' furlher s",ditos regardins ,ueh de"'s a, fluid ,nelusi""s, "lable '" ,adi '>¡;eniC i,oIO]'<-"" alte,ali" " S,,,,,h,,mistry ""d flu ,d "",deling, ,un the I'er)' Waw , i, k '" ""lIinS ,,11 from" n incurrl'Ct pr~mi"" 'Iñis sil"aliun i, n,,' eh mo,,' «>mmUIl Ihan mn,!! ni " (, d ~mid is prepared to .1dmil! ¡'rom a p raetica l ]'<-·,sp.-clive lhe eompr"he ns,on of p.H.1genetic "'-" t)']'<-· "f h)"d,olh~rm.l l s)'st~m " nd," in\'loslig.ltion, ""d i1 ",ill cume os no su'p ri.., tn , '~plo rat;,:m man' g""; 10 le~rn just ho\\' mall)' ti ""OS this h.lS N'Cn misil1krprd,"rlallt 10 unde",lalld ",hieh p hases are ",lua ll}' Ore bcoring. and 1" romp,,,hend Ihei, s patial d istribul'o n. From ~It'ry !"-·";p.-cti,,,, it b<"Comes a prinl<' gl"Ologic,,1 "-"
,,,JI
lo k""p,l1g ",ith the rest of this serics the texl is aim,"scr"" lio,lS ",hieh e"n be made t'ither by t')'e O' ",ilh a ha"d I""s . The p la l~"; h,\\"e N"''' ..,1,'C ICod to sho'" a ,a"g" 01 mi"<'ta lisa tio" styl,.,;. and p lote d .. ",riplions hM" N,,'n II'rill"n .l t I""glh lo ind i, al" Ih~ app 'oaeh arld tho"gh l prOC('S.."-OS i",-oh·.oJ.
l
ORE TIOXTURES VOLUME 3 0VERI'RI;"'' fING TEXTURES I
1 2
O VERPR1N Tl NG CR!TERIA 2.1 G" n~ral \\'ilhin Ihe "ml~>.1 01 this boook t h~ te.m o"c'print;ns rpf~rs to ,l nl' l,>,hora I ob ... " ,.lion whieh ,ar, The .im in all m .... p'intins obst>"'"lions.;, to esl"blish a St.""'"lions a rt' Ihus Ih" bu ilding block> ",hkh produee a pa ragenesis. The enli.e p.oress is absoluld y lund a mental to anyont ",ho is It)"ing lo ,.,;I.l blish exaeUy '",hal is soinS on' ",ithin an)' lor", 01 h)'d rolhe.mal-min",,,lisi nS 'plem O "erp rin ting "it,>ri. ar~ ""'l' simple in Iheo,y, but i<"nd lo be ••,Ihe. eomp le x in pra e lice . The'" " re nu", ,, rou, sm . 1I traps a", a it ing l he ,,,,"'a. )' o, ine'perien'ed ob"'''·e ., il"d as p,c"iousl)" sl oted • good groundins in Ihe diffe",,,ee be h """n inlill and a lkr"lion coneept. i> es;e nti.L In pr.",lin> " 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 s<>pa •• k inflll l a Iteration comp<,,,,,nls). (1'I,' les .... 11). (ii) Fr asn,.."ls (b reccia) of earl)' min~ ,,,lisati,,n mnlai" ..od \\'ithin !he n",w min~ralis.ll ion (1'lales ]2-15), 2.3 Second ord"r criteria (Su.pieio" aNusinS) Anl' struchm ' ",h ich has Jcled as a conduct for ,1 h)'d ' otherm.,1 fluid .,nd subs&¡ uent depos ilion, is "c r)' ---ORE TEXTURES
1
VOW~ l F.
3 OVERl'Rl,'.JT1NG TEXTURES
prone lo ... aetivati o " dll. inS a subse,!uent r", k fraeluti"s c,· ~n t. In simple I,>.ms lao lls, ""ins, b"""d. zo"es I~nd lo fo,m Ihe \\'eak li nks in Ihe chain ",h ieh h e p s on t>.eaking in Ih~ same place. It is .... ,y common for a suceession 01 mine ••, lisins c"ents to occupy the "",me zon., of sl .." tu r,,1 "'e" kne-ss . •tnd tm, simp l,· struelura l ,,'pedmposil ion crite.i a presented abo"e may becom" .>'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'<1nclwa y Sl,uelures (usuall), l'~i ns / m i cr",'~ins) trA"ersing e~ct'Ssi l't'I)' IMgl>r Meas of .lIcr,lI;on.
(ii) lVide. p r~ad altera ti"n ",hieh dot'. <101 ap pea. lo i"crea ... signifieantly «)t a l all) as il appro. ,h,>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<' ro,k, '",a n d l>' ~c ross' the ., lt e rat ion zone to produce gro.s ll' as)'mmet'i, s it" a ti ons (iv) Asymmetrie mism;tlching a lso orcurs in infil l ""'I0c"ces. A ll hough th ... p is no i nh~.~nt 'eason why m inerals should deposit s)'mm .. lr;eally on ca ,h sid,· of an op,>n ins. Ihe.e ore m."l' situ"tion, ",Itere t ite ob,.,r".,r inlu il i,'e!y ,uspects this shou ld oce". ",ilhin Ihe st)' le of s !,,-'Cimen beinS e~amintod, An extt. lay~r On on~ side is al",.ys su.pieious, (b) Inconsistc nl ., lleralion con/igurati"IIS Th.,,,, a", many \'arialions!o Ihis cr it~ria, bu l il is "e')' eommon fo • •,n .lte .;tlion >,one to ol'e'prin! prec., isting .lIe.ation. lllh,· SKond .,II~ration completel)' o"erpri SIl'I"-'Ct,od ch .",,,,,, zone ", il l S"'" diffe",nt .e.ulls _'1 diffe"'nl po inlS.
(e) Alter .'ion "f a lter.,ion T" ""me ex'eft' IhL~ i. a " ..iat;on "" ,h. aoo,-e, bu' i, ¡. qu ile common 10 ~ al tN~tio" prodUCIS whieh ret.in Ihe textl"e 01 pre'-iously .ltereJ rock. Exomples 01 ~ond order (suspicion .rollsins) e riteri~ He si"en throughoul the p lat"s, ",ith some ""Ieded situ.lt ions being illustr.,eJ in PI. tes 16-22. 2.4 Thi rd order criterio (lndirect overpri,,'ing) Almo»l any 00' of eore. Or brse rock sl.b. Silu.k-d in Ihe margina l rone; 01 struclura lly ronlrolleJ ore ",ill e xh ibil i,;olaleJ , 'einlets ",ith alteralion / inlill assemblages whieh are ol,,"iously differenl lo caeh olher _The Solme silualion will occur ,,"i lh isol a led "eins!>'einlel' IOCdleJ in 1""0 diflerenl pl.cu. The p'e."nee of ''''0 d iflerenl assembl.ges suggt-SIS Iwo d iflcre nl sl.ges, bUI OO"iously g"'<'S no hmong ",tormahon.
25 Fourlh order crileri. (In direet o"erprintinglemperalure infere'ncel. \Vhere !he above isolaled '-ein lel silualion OCCurs, il is oí considerable assistanee il th e obsen'er has sOrne ,oneepl 01 high lemperalure verSIIS lo,," lempot'r.ture ."cmblages_ 1>-10'1 par.genetic sequenee . rep rese nl declin ing flu id lempe ra lure sequenees. A b iot ite rich ' ssembledge would nOTmally ind iea te mueh higheT temper.lure Ihan one whieh "'.s predom inantly cI.y, It doc. nol nece ss.rily 10110"" Ihal the biolile is ea rHer, bul il is 3 good wOTking hypothesi s _ This s lyl~ 0 1 criterio needs lo l>e used ,,"ilh ea "tion, .nd hence Ihe íourth order grouping.
Another very Commo" suspióon arousing indic.lor is a sudden ch.rg" 01 cryslallis,'ion Slyle ",ith in an apparentl)" conlin uou s .equenlial inlill seque nee _ A sud den ch.n~e frum eo."'" "ysl31line eomb quorl? lo finely la y<'rc d 'eollolorm' style. ,,"ould be a eomm on example(l'l.t< 1)
OIl.E TEXTUII.F.S
VOLU~tE
3 0VERPRINTI¡":G TEXTURES J
3
O VE R P'~ I NT1 N G T EXTURES
' "A'uf~> 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.'<)logi~al parame' NS roneerning Ih .. slr",I"r.l1 and fluid hblory o f an indi"id "al ore d~posit. Adm;!tc..:lly lhe amOlml 01 "i,ual informalion Ih~ 1 can be extr.el~-d re la tes to th~ k no",lcdg~ and expe rienc~ 01 t h ~ obse r\·.. r, but Ine opportunily remdins :o conside r e"idenc~ re laling lo ore senesi, from ~ r.nse of in le rrelah.-d perspecli n 'S. Thest" include: O'· ~'V,· i",i,,¡.;
(e ) Fdetors rel alins to physic. 1 pM~m .. ters of Ihe ore n"i d s. Tempera tur .. indic~lors are rea d ily ~,·~;t~bl ~ Iro'" ,he: dcpo.i'io M I ~<~ u ~nce. I'aramelers re lalins lo p r<'ssurc and pr ... ssure "~r i "lions are present in lexluros thal can b~ r.. loted lo proc .. sses ind;c~li"e of hydra ulie fr.~lure. hydraulic b r<"<:dalion a,d bo iling. In m ~ n y (ases "ven the crystal s;z.s a nd .hapes can be I ~nl.l i '· ely re lated lO p ossi b le ~ooling r~ les, fluid salur~Holl. o. p h. Sf separations. This is cs p ~d a lly true wil h <¡"drIZ lexlur~s (Dong ~I al, 1995).
(A) $tructural .....·oJution as reflecled by Ih. sl)' Ic{sl of
fracturing. This (ould be !"eSla ted as underslandins Ihe de "elopmenl of fluid chan nd ways. 3nd h<'1"ICe :muelural (Olllrols. (b) Chem¡c ~ 1 composilion ~nd e"ol u lior of Ihe ore f1"id~ as refl<"Cted by 11", composiliol1 of Ihe infill m iner ~ ls. dnd their as~uciat~d altNalion assemblagt'S.
Stas" (Name)
Infill'
"Chloril.."
Quarlz, chlorile. pyrite
AII~ation
3.2 Recordi ng ~r\·alions . h is a lw.ys ",be to record ob"' r\'atioos, and Ihi. is PM lin,¡ arly Ir ue in o"erp r inling sl u dies. Many si lual ions ar~ ~mb i s""us and / or s ubt le, and il ;s crucial lo loo k carefu ll y and nol t" Iry lo force concl u sion. Irum unclear exampltS. 11 os q" ,l e surprisins jusI how many opparen tly elear / simple s¡tuaHon •• r.. in facl complex . A u,d ul pra(l ;ca l sug.¡¡estion, ;s to (OI\Struet a table as indie.led belo,,".
SlructuroJ
Slyl~
Commenl
fRock Iypc all"rNI C hlorilC, m inor ""rici le? and carbonate (Ba,;;, lt) Irregula r
Small " ..in 2-3cm wide
Distinc~oo between inlill and allera lioo blurred.
Darke. pink (Cranlte ) expres.sed by pinkins of fd dspars
L..a.rge "ein 6-&m wide. Infill predomina les. No breccialion. HiSh fluid pressure· jacking fracture open?
Suspecl pink ¡nlm and alteration BTC a lbite or K-spar? Cu l• • mall eh lori le vejn, wilh no apparenl e ffect'
oo,.
Pink vein
I'ale pink minerals. Sharp edse aSainst aheralioo
°lnfill. It is "ery raro tha! !h~ S<"luenlial infill ordercan be eosil)' obser\"ed on o ne .... mple. If r~l3 t ionshi ps aro a pparenllhey can be l"l'Corded. For exam plo- - Qua rtl
"""'1',;",<><1 by ~ h l",i, .., or Qu~rtz (Chlorito, Pyrit.. unce.l.in liming) .. t,.
4
ORE TFXfURES VOLUME 30VERPRIl\'TING TEXTU RES
,, 4
I
F 1RST OR D ER C RITER1A- MI N ERA L SU PERIMPOSIT10N SEQUF.NTIAL T~'tu,..",
1 ,~FlLI_
.1na p""'lcm, l'ldt(... 1-3.
"'t . .
1"lill le,h,r<'S pro\'id,·"'~ l}' \'" Iu.,b l.. ;nf",m.ll i"" co"cerning the s",quen"jng 01 mineral d .... po ~i1ion . W,lhin ~ ,ingll' sldse DI delX"'i1ioo ;1 is ,.~ry comm<>l' lOO" mi ..... 'al. lo pnoripil"" as crystdl> or I~y~ Earl)' ¡ormeuls or la}"<"f'S t>e<;o",.. "ock.oali"" ~Qr\O'S for .uqu<·mial sequ .. nc... This is mosl easily ob~,, ·,.,j in IMgC 5<31" u,·il k... wh,eh a .... 'mi)' p3rti.!!y inflll.>d . ~"d m~ny S,'Qlo¡;iS1> ",ou ld be f"mili.r "';th ~ lx",I"cu IM exampk.. which "",u, in ~li ,;"is>i ppi Valley sl}'l" en";mnmen!>_ WIl .. " Ih,' fluid spaee is com pll',e' }' ¡"filled . scqu .. nti.1 d .... ucliOlls 3 liUI .. mor(' dilfieuh. bu! can g.. ,,<-rally be .-.:hie, ed ",ith onl)' minor problems_ Crit~.i~ f()t '«osni~ing infiU d.e p..,.,...,tO'd in Volu"", t ...... it ii ,,·"'th noting tI"'t this is .. moch nq;1.-". :tcd skill.
.r.,
Within ,("in •• nd b,,'cda r ~ "i li~ S nyst.ls oft~n "uet""t" as isolJlcd indi\'idu" ls, r~ther than 'S ti", cont in uo" s I.yers ",hich M~ sO ohen depict~d in I,,~tl>ouks_ In this "i""'lion il C.n b..><:om~ ""'y dilfkll lt lo fjnd ex.mpl"S 10 de,,,I )' illuSlrat" the complel<' rclJlion>hip:. bo.-tw,'t"Il IIw Ih_lo fi,'~ mint"r.ls ..-hich ha>e 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;<"'1""""'" Imm one .p«inwn, .",d in many caso:s ..-ill be Idl wilh" fe", URCcrlA inl>CS conccmi"s deposilio",1 timi"g beh,·....'n t"'o 0' mo.e 01 the mine'dls. C Olllnwn minerals whieh gi".., p.'tieulM problcms .re Ihe rhakopyr il.-/ p )"'.hotil .. ""ir. n..."", fm;¡lX'fItI)' prodpil.tc rogt>t"" •• nd "",itht,. lilb to fo,m <"t)·s l.. ls. It is .. 1.., quite poss,ble fOf min .. ral s lo b .. p, .. cipi •• 1inS s im"l.aneousl)' o. eontinu"'-'sJy throughout. lhis e~n ob... iously prud~ COflIr.. diclory Ol·e.-printing ~,,\ts .
lhat the """'Iuenc. 01 p«<;pit.tion deduce1~!) Th",e are ~."er .. 1 .... ys of ,e~ohing .. p,obl,'m of Ihi s ".tUTC but th" firSI .t ~p is to b .. a lVare of the possibilit )'. An "arl)' warning "S" .. l ;s o.".lIy sinn by thc tnlu,.' and 0' miner.logi'.' eh .. ng~ s lVithin 11,.. ... quene~. The inm'r "'sion. of Ihe \'ug m,, )' ""ord ., ,h",p t{", lural chang" in ,,)'st,,1 si'.e_ AIt~rn .. t;"el )' tll<' en t i.~ mi neralosy may sudd ... nly chanse . In m.n} e.. ses both textural .. 11<1 mineralogie..1 ehanges QCCU' ... hieh ra;se s u s pi
T heorctkally th" si",,,lt.neo,,. o. eontin"o", p,edpitation problem (Qui d mah Ihe eoneept ,,1 ><'qllcnli.. 1o.-erprinting of li",il,'¿ ,·ah,,· 0' im""""ible lo .ppl)' as .. p,actie.1 n'illit y. HO\\"",'r from t"·...,I)' yurs of "XP<'fienc<". 1"" " ." .... c.. n a>su ... the ,e.
min<'uls nonnally p«<'p,tate in .. s.imple S<>qu,'ntial m. m"·,, whi,h is r<·adil ), dedu""",, with .. ... o.~ing ~""" 'I,'CIS~ of t"" p.inciple> of inlill "-"'ognition. A murh more s"ri ou ~ p'oblcm aris~s IVh~n i! is ,,·.li,."
0'1",
OII.l TF.XlUIU:S VOt.UMF l OVU;:J'IU"TtNC TI'XI LIU.!> 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""le<-'
T
Thl- Spt,
of Ihe ab<."'e is rcad il y visible but Ihe rea l question is: 'Ho'" many .tases of dcposition .re repres.ented here?' U >eems Ihat a large ca"ity has ~n prog ..,ssi,-cly filled . The ddiniti,,,, of a ,Iage lea,'es a liUte lo be desireJ, bul is generally I.ken as a sroup of mineral precipitat" ",hich ha,'e be .. n deposited durins. conlinuou. fluid flo", . l'his is imp<>Ssib lc lo e
6
ORE TEXTUH5
VOL U ~~E 30VERPRJ~'T I .\- G
TEXTURES
Wilh ea,h 1<"<'lon;" br .. " k a
n~"'
....1 of infiJl ,an b<:
p IJced i natelati, '~ timesequence.
In Ihe abo"c example lhe eag le "yed observer Cdn in terpeet a te<:tonic break by ,areful ly inspt"<'ting lhe ""S.S chaoge in s l yle in the c .. nt.al zon~ ", il h th~ introductioo 01 c a ss ilerile, is also cxt ... ", .. ly susp;"iou., (-'-en lhough nO CrOSS clIniog rc lotion,hip can be ooserved, The snddcn chan!e from coaroe cr)'Slal lormal 1<.> fine layer formal. is .1'0 su, piciou. denolins a ,han",· from isolated nuelealion to mu ll iple nucleal;on sit'-'S. Obviousl)' I he total ans",e, caonol be Meu.ald)' deductoJ from this spe<:imcrI, .nd ,"ore would ha'-e lo be coll ecled fron, the 1",.lit)'. However, the ' e is en"ugh lo su'ped al leaSl th.ee stages ",ith se\'\-ral ,h a nges of ,hcrric a l "od / or physical par.melers. Cassil .. rile is . . . Ial ively hiSh temperature minera l (say plus 200'C), 11,e", is also., ",inule "oss ,,,Uin!¡\ sitiea vein (bou"m leh) which tr.ver;.es the side layers 01 the sma ll \'ei" ."d ,,,,, Id lin \¡ lo Ihe centre quarl_? Tlle ca vit y de\'elopment across Ihe , .. nl,e seems to be • la te lea(hing effe<:l' Qnc lale fine black I.,)'e. Sl",ms lo be absent f,om Ihe tep Sl'
o I
1cm I
ORE TEXTURES VOLUME 3 OVERPRINTING TEXTURES 7
PLATE 2
SEQU[:\'TIAl. INFIl.l.-EI'ITHER_\IAI. STYLE l'.¡"'go gold min .. , Ch..lers To"~rs r~¡¡ion, norlh o-.-I~nd. Au,lr.l ... (Seou l.ooel·
u"-"d hit)' Jnd I.r)' Ih'o,,¡;houl Ih.- S)".lem, as dlff,....."fI1 regioos boil an.d / o. f •.oclu ... al di/fe"",t times.
TI..- sp<'Cimen
g'~ph".II)'
illu, tr.l....
t~e
probk-m and
it becomes almosl /u¡¡l .. t,)ing to s ort out Ihe
hlS pl~l" h~, been seleCl ed 10 lIIuSIr.le ,he problem, o/ S<'
T
Epilh" rm~1
'y
ra,,'d \\' ilh Ihi, ,i luJlion 11"",e ;5 ollen hUle po;nl in Iryine In arr",.¡,-Iy cl~fin~ 11-", numbe. ni ;ndi\"idu,,1 phJ",~ in Ihe co"'cnlio,,~1 mdn"er. I1
,
OKF.1UIURFS \'OLL\IF.JO\'[RPRINTllIiC IEXTLRt:S
brK'i ~l ion
."d inliU ;.equencin¡;. o.._pile 11>.- I.ry 11-", obserw. will quickl), run inlo prol>!<-n ... I.,.ing lo pi«<- lhe. .Ior)' l"!le:ht-'. Ubl'iously il dep<"fIds upon how d ....!"'r"t.. ly ti ..• tot~1 """Iu""",. is r<"eh Ihrer figure gold I alurs. I'ilgh g.ade tones .r~ oUen d.r~ coloun'd .~ Sil". Lo)'~'" as",oc;"le with fin., g •.>ined ,,,Ip hid,,,,.
el" ••
pho!og.~ph
o
lcm
I
I
ORE TEXTURES VOLUME 3 OVERPRlNTING TEXTURES 9
r LATE
3
SI QUE"ITlAL
INFILl.
STRUC 1 URAL
SUl'flU\tI'O$ITIQ'\I - CROSSCUlTI:>:G V!::I' . r ... r.,< goIJ mi ...... T"lf.... w'-
Tmmr l..,
hi~ pI~t~ h~s
illu>lr~l .. ~ mor" 01 ""'l",·" li.,I",l ill ~C('í>"' I'.",i.'"
1>0','" includ,'
"'~n1 ple
by Ir"n" ,,"¡;. 11 ,,,,',-,, 111.> crikri. 01 ,,,j.,,,<,,1 >l'p<',i'UI">sili,,n ,H1ol .lruelu.,,1 ,up' -" ;"'I,.."il;ol1 ,
Th(> 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<' 101' ronIMI. TI,., b .... 1 ........ comn, .. ....,ñ ,,-¡Ih
and
Pffil~-
(~Irop}'.il ..
lo a mid ...... 01
g .... )'I ... hitr 'Iu.rIJ
quarf'~
(sr..y / " hi1 .. ,
(1)._ ,. ..11",,·) and p)',jl.. (""Ir >,,110 ..')_
Thi, po',,.,, "p",.rols into .. fin ... gr.in.>d zonf ,,1 '1""'1>. p> "1 ... ",,111 mino. ct...lcop> rit... T"" (o"'pl .. ~ "1'1"" .....:tion wnsi'l~ 01 promi",,,,! b. ",h 01 gr.""I • •
"'"t.,
e~ leil.·, s.ey m ~ t ... i., Is (d"lomite .H1d "nd ~ nch,·<.>.k 1., )'". of p y.i tc/ch"lwp)·,il ,' ",hid, iSSi""I,.. in le, tu", lo Ihe .egion juSI 1",'"", Ih .. promin....1 ",kit., 1011<'.
p} .H .. -'
T),., inl .. ~ti l i~1 sul ph;d~ bt;-.:ome< 1'> .il.. d<.>min;;ml upw~lds. And bolh Iht s,~in M1.r of '1u •• tz and tnt ...,'ItI.1 "old 'p.cr {I«r ... ..., In .¡,_~. Thb i. ~ ,00"i.I<-01 f..a lu", o f the s.>ddl~ ."",f , .. in !4)' r,. of 1),., MIO ~ ..., f. 1 Tel l.... Thi~ ob"¡o,,pedm .. n p,~<"n IS man )' 1.. ' 1"",1 p",bl,·n'., Tht- inlerst; l i ~1 p),.i le·'lllMI,(chakopy.i¡'-) I.. a,,' f" ..""n l but .He d il''' p led (oy"'p rimed) by p"""in .. nt, " "gue ly n-i" 1ikt--I~yr.s o f f in.·. dull,· , p )'r il ... ~nd .Iso co"I ~;n sisnific~,,1 ~n'o"n!S of cd,bon~I,- (whi t.. ),
,h,,,"
In d,-\.> iI Ihe finN p )' ,it ..
I~) .. "
art-
«)mp<>S<'d of
1') ril"c'1·SI.ls of r~I ........ l)· ,.ri.bl .. ,uin sizr . and il i~ diffieuh lo inlr,p'.-r II'h .. t),.,. 1),.,> 'fpr<.,..n l an ,,,filling or on .h" •• l ion ,omponrnl The w,ilr.
" 'oule s usf"-"<'I •• p id nuelul ion with ,nhlt Ming domir . nt. dhhough Ih .. rr;. ~n imp'e«io n 01 shea, SI) 1.. in Ihe fa b.ir .ugg.. ,¡;ng ~ller.tion pyrile (o u ld .lso be p."sfnl. The p roblem r~nnol b .. , ..,o¡,. .. d by eye,
~ilk.)
11,.. c.. bon.l .. (..... hite) comp", ... nl "bo .pl"-'ars to be ,'"i n,I~ ..
infitl \\'h",,, it Ir.,·""",s Ihe ",idl" nf the sm~ ltl<,nsi"" sl)' I.. g.1.ht.... a.e p •• liclJ la .ly promi"""l abo,·.. tI><' uppt', fin<' py" t., 1.)',-" (1"1' "'fl) ".hieh ,o"l d ". ,,11 rel. le lo I h ~ o,iSín .. 1 m.in holi~ool.1 f'''':lo,in,_ TI... ",hIle" I"J'S. In.ond ~,,,,,,,d tM fin<' py.il .. I~rers•• s.,n _U"<'St _""."ng f.brie a~>o
'ock, .nd
nI(' .~,I""s,·"",nN sh"", 111<, del. ils 01
Ihe "ppe, .",d
lo"' .... n"io.,~ of the ,eln. 'I'h lo""" ,..,..;t,O" (boUom ,isht) ~ < compoS<'d 01 g ... yl " ·hile qu.,t . ",hkh is ele.,I} >om" ro.m 01 Inlill. Iln:"Son.ol c'1·~l.ol outli"..,;.,. p.o,balh he-'''S"""I oullUlO.'S. COIT<><1 oullined by eHellent tri."gul •• te>!u, .. , of ch.1k"'P)" I"¡ py"le infilling around the hM) q"MI~ uy~I.,I < I)'. ih· c'Y,t., 1..t>.po'" '"p,¡:: ....1 Ih.,! il " "d.·"I.,", p.io. lo rh . rcop)".ite. The qUMI~ sr,.IIl S are .Iso ch",,'ct.. ,iso.-d b)' \'.'g,"e d.rK , im, ",hieh ,ugg.",1 """'" ro,m nf ,Ik.dlion (silie., r<""ysl" lli,inS1) ."I"l inS lu .u lphid ~ d.· p .... ilion . It is .Iso .'pp",ent IhOl th.· ~"I phid~ ,om p ... n,'nt ocusionatly (111) Iht>" 6" th,' q "M17
.1""
The le,lu.r is difficuU lo inl ... p,el a~ m.n~ of Ir..'1u .. ,I" cry,I.ls apf'<'d' lo nuelul" from no ob, io". s ubslr.I •. ~' .. '" ck.... lr e.di .... Ih.!n 11'1<' , ,,'phld.,,,. and f,om I h .. i, appe3,.nce s .... m lo b .. ri l h ... fras n,.""" r,hibltins mild corros""'. or a nct..-ork of O)'SI~I~ &rowing in ~ 'Andom 1~lhce lo ,m. !. T),., 1.11,-. "'o" ld p'o' ide the sp~c" ' '''1" i'''d lo p.od"c" Ih<, COI"'" ", Iphide infilt, The occ~si"'ldl Crt.,.~ Ctlltin g ., ulphide 'el~I¡..,,,~"i p ,,,/;/;<,,, mild 'd p,~_ t,¡.ling .il". (~·s l.lls p.io' to sulphid .. deposilion? JO
ORE TEX1URES VOlL \lE 30\'ERI'RIt.. II"G TE), I L RES
It i. conccd..d Ih~ 1 nol e' e,) on~ n,ighl .g''''' on Ihe rleldils. b U1 Ih .. ,,'nerdl p~l!c.n of o pc'n s pace infil! gr.ding ' rom lo finN mo, ing up"'a ' ds. \\"ith 1.1.. , "t"g.·, 01 fille. and/or shc ... ? tt'laled co mponenl s oc c urrins w;lhin the 10p 'lu"'I~'. is ''1 Ihro"gho,,1 al1lh,· und'>''1'n"nd "'POSJ'es of lhis ,.-in. Sch"..hl .. i~ al", " ",mded ~I ",me poinls wilhin Ih" "110 R ~f. p.~d . ..
'''''''>'t'
1'''.,....
rr..- Tdf,-. 8"" .....1'1' of Sl.(~..d cres«nl ..... ddlr " .... ~haprj struCIU'es ...1.tOO to lold oull"..." ""lu; •.." interr,e UIi"n ". ilh ln Ihe abo.r IUlu •• 1 ,,,n lr,I, Euly high fluid p,t'SSUT<'" h.'e prob.obly pl.y.-d • mdjo, u d r rol .. in op .. n ins up the app'opri . le s t,,,Clu , .. 1 ~on .. s. ".i lh Id t.-, ~h ... r! 'fl. t.'d fdbrie b.-coming locused in Ihe uppt' . po.lioo. 11 is no! Ihe inl .. nt of Ihis d."",.iplion to "pt.", " I,lIe f".lhe •. bul .i mply lo illu >I'31" Iha l Ih .. o~'I',' l io".ll p"".."s ... f """"cr.;t,,n d inS '""c'p.inti,,S l. "",
~
infill. "Ite.~ tion, and slnocl" ••,1 f",r'pt'ctil' c", opt.·ns up a \"lid .. ",. Im of CTuci" I gen .. lic th inkinS'
o
lcm
1
1
ORE TEXTU RES VOLUME 3 OVERPRINTING TEXTURES 11
5.
FIRST ORDER CR1TERlA - STRUCTURAL SUPERIMPOSITION.
CROSS CUTIING VEINS - STOCKWORK ANO OTHER VEINS STYlES TEXTURES AN O PROBlEMS. PlATES 4·11
e""" " '''i''1; ",'''' ,"o "".. "''''' ,,.,'· i..... ,,1 "H " f" i "ti,,~
w,\"
"',j,,,,', .",,1 ",".,11,· 1'"."-,,,,
r,",' rn*,k"'.. ~I"" ')''''"'''' " ...... ,,1
., ",1.,,1,",,1,· 1",,· "umo,·.,,1 "'W" ~ ";,'h ,",' d i,'¡""",, d;(f"".." ,""
I'·M
<'"
1><'
"."11)' ,t ifl ...·" ,I ""I . 11"", ,,-•• , ,he< •. ,,,.
,,,ft,,, ')"C'"''
~ ' o",n
by 'oc'i , "")
n " OU,,'
,"yol"" "n,I,l f'k "" ~.,, "II •..,-,", I"~ .,nJ d'p'''>L ¡"n, Th ,' h.""",;"~ ,'"c'o, m,')' 1><' ,'I,,~ 'I ,' , II"~ ,~tI ", ,lq~ , ,, tI ,, , , , 1
' '''oL 1\
,y"""""
SO' oJ •" .'"\¡'l<' ~ "" Id 1><. "pi ,.-.. "",. 1 w lw ... "'1"·.",,1 ",' i lin~ ", .•. ,., . h ,,,.' hn", n",· in l< ' I
'f""
"·,,,It
,'oll"I" ,m ,...'n, . S,m' l." ,,", ,",n" , ,,.-,-u , ". i 'oi" ".,~.
1""""_' ". '''I'P'~ ,,,>d f""rt'''·"
n.. r~'¡'¡" n, t...,-, ",,,,, l. oto" "." í; II;";;- i" 'h c' """ '''''',,~ pk"' ... ,H ,h ..
" l'K-" III' I,,~ < f~"' ¡'"" ,,¡ ><'1 ' ~""" "'-~ ,, "','
T, p~'." ,.,." ""~;" •. ,, .".
R"i",.""",,";. ,h, ",u.,1 'I'I'''''~- "' .,,-,,1
,,,,,,,,, il)' l"mf'
, ,,'S" ",,-4 ," .,,,
",ml'~"
TI", 'pp",,
~"
,.,,",... lo, "O' "'.U,, I ""k;o~ . M,o) "",ro,,'), ,k.-k"""l> oH" ""il w"",", pul li "~
.p,''', w;'h ,"'o'''",pi" , 1" .. ,
"' · ...- I" i oh,,~
,,¡ ,
~'. ,'. '''-'' ""," I' in¡;
~."",
01 I'<"plw'i'"
" " ,,,,, ",,",' ~n¡;"' ",.~. 'n.o """'I!";'."'" ",-~k-J f~ ' '1'¡' H ¡'~ .....'11 w i'h i". "w" ¡".' '., I",,",c' P''''c' ,,1 inl•...",,,,,,,,
"·,,,'m
<.n .... n. .... _ , ,m~l ",-"un' h"",1~.J, "f OC<..." .. ,,·I,,~ ,' .' ,''''u,1 ";"",1 """ l.,""" I-...J "" lo< "1'"11)' """"",,1 wi>
In .. ""'. <..... d
,,'., uhh ....,o _.,.". .. , ,-. i", >r'.' p,'''k" I"I)"
romp~""
'"'l.......,;,,~
;. _
onIy impr.>
,o.
, ~ illed.'
Om,"
,.-.~
....,d 'h<
,l>.' ., ~ of ~"-,,.. i .,,,,
''''"r
¡i,., o,;.,,"
An ,.b'ur' n",,,~ i ~g ~I , co,,,, '''''',,~
, il.-, ,·, ';n ... l,
,' ~""
,ut> ,,, .. ,.-.... , ilk" ni"
"f"'''''i''''''' "I!,~...... I>.>k' ."",,-.,1, .,,,,,,,
",;n m.w ,II~, I'I~'" w,lh",,' ,-t... , ~,.;" ~~. ')' P"~' i1 ,."",,,-,,, ." "" li c~ ;;'k. ""in. lh;, ,.." il<- "".H,"" f, l". """,,1 imp"'''K.' ,,¡ t-.' ~
ru t 011, (S,,> ,,,,-, , ...... )
L" ,· f',lelu'"
"f'f'''''''
'-"~ri'" ,l>., '¡ '~f~i,,')' ,,1 ,..., ,,"", ,u" I "~ "".',."',,, 1, 'Iu"" ,",!,n",,~ ius< h
mol,,,,,,,,,,", "oc~"" .."".O
c,-""k·.....1 ,TI""
"',!t,. ,,,
"''''','' 'o ,~" pml>l .. m Ii",;n "'M, I, ,,·Iu ' ' h,' i ~",' ''i" ,'' i ,,,, i, 1 ''' I' i~ ~ 'o ,, ,' hic" " ',
f""l"""'~
"'.>c·lO,.,,¡,,"
"'''''''
r,,---,',"';n~
, ,,·~,, c' "")
,-,'m•.
A "',,-
f"''!'"¡;.l'" """"" ,' """" ""in, .nJ I;n. In., '-.;.... "H ,',lho'• • • k n., f,,!< ,~,,' ",-,,,
,~,¡""
nd
,·f"..., <." ",~ I , ,"""-....1.......·"."",
TI><· 1"lI o\\'¡ ,,~ 1'1."" ¡",I",k _-t,,,,,,," ~""!I ,, ,.,
k.-<. ..'_
...
~~~
"','"'r"" ,,1
ilh» tr,'k' ';.' ""U
P LATE 4 SfRUcrURAL SUPERIMPQSITIQN-VEINS ](i dston gold min~, Einaslcigh region, norlh Qu""nsland, Auslrdl id ,
T
hiS plate has be<:t~>d , eSp<.><:i~lIy in systems d"min.> teJ by siHca. lt al"" shows some Iypkollomina l,>d ,tyl" quottz ' ·eins. which are \'Hy characteri,tic of porphyry molylxlenum systcms_ The relatio"ship bctw~'Cn the quartz \'eins wi¡hin this plat<- i. quil<' a mind puzzle. The c,>ntra l ",>in 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 inspe<:lion "".. e~ls o "'-'ry sm"n d.rkcr ,ilie" vein within the cen tral vein which is , 'isibk in thc upper re¡¡ion 01 Ihe platc and appcars lO contain wafer thin slivers 01 Ihe host \'ein? The ",ntral vcin ,..>emS 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><:idlly tl> 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~ si
co"
This ~ccount rould continu<' d<'M'ri bi n~ all Ihe "ther small \ ' ~ins ",ithin lile rk, However. it is apP''''T\t th.,t p"'cisc de l in~ation "f ¡he number nf stage, i, rdlh~r d illku ll_ 11 is "iso .pP<',,'nt t h~t .11 of th ~ sl"g~'S look \'er)' .imilar in g~neral, "nd the sy,t<'", v.'ould be' interp.ct<'d as" ,nnt inuou$ fluid fin" iotimately a,,,,,,iat,>d with mu lli p,," r<-,.i,,,,s 01 b.itt l" fracture . Fluid pres.ure is difficult to ~,tin'Jte bul ""-'ms cnou¡¡h ," hold \'l'in~ "pMt> Th~ fine grai"eJ nalu ... 01 the laminatcd sil ie~ "nd mot,·t>o.l'·T\it,· suu,,,t r,'pid depooilion with multiple oud~ati"n ,ites, Th<"" obse ...·ati""-~ Iri¡;¡¡~ •• S<.'ri ¡,s uf q ,,~'Stioos. What is t"" cause 01 the repe.te~" lo be pMt <)f a cnntinueJ tectnnic n 'enl ",ithin .1 reloti\'ely short p<'riod uf tim,·> \'o/hat i, the cau,
o I
1cm I
ORE TE XTURES VOLUM E 3 OVERPRI NTINC TEXTURES 1.3
P LATE 5
STR UCTURA L SU !'ERI1\.II'OSITJON· VEJI'IETRIC INHLl.
1V0Ison, Icad · "'ne mine_ Cenl"'y ,egion, n O'lh Q"""nsland, A"sl r,llia_
his plat<> has b,"en incl"d"d to il ,,,Sl ral,," Ihe difli.ulties i'l\'o l\'ed in ob.en' ing cross wlting rel~l i onships ",rocre Ihe mineralogy 01 .,,
T
Th~
p late il lllslrak'S seve,a l s tages 01 silica veillins, ,,-hi.h consist 01 in litl ",ith \'('ry liUle allerJli'm . Oe.. " .ut off-s,% have oce",red, invol"ing very lill lc SOUS" dlccl._ The micro(ra(ks ha\'e upelled under fluid p,e«ure, such thal Ihey hove rc asonab ly ",ell malching ",a ll s_ This criterion i. o/ten ustxl lo identily i"fill /rom alter.1tlon . Al"", ,h'-ers 01 ",all mck are included wilhin some o/ the smallcr ",'ins, a " d in SOrne (ases seem lixc'¿ as 'flo.uing' frasments (centr.11 region), No one seem S to h.'-e offered wn\'incing expl.n.tion for 'floaling- fr'sment. in s ilic. "ein, ",hich O«ur frequ ently al mueh ''''ger seales. In "lan)' c~ ses Ih"y arc 01 high se and ,hou ld sink! Are thq heid 'part by fiuid p"-"SSure long enough for silic~ lo pre<:ipilJ te oflen as comb quarlz! !)OC.,. Ihe ,lllea go IhrOl.gh a gel ph.1"" al ",me poinl> 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
14
Ol1E TEXTURFS \'OLUME 3 OVERI'RIt\:TING TEXTU RFS
ereeping up tI>;, 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,"
o
lcm
I
I
O RE TEXTU RES VOLUME 3 OVERPRlNTING TEXTURES 15
P LATE
6
STKucrUKAL SUI'EKI ~II'OS mO,,-VElNS, STOCK\\'OKK. Gra,ber¡.¡ copper"¡.¡old .nin~.E't~ber¡.¡ di,triet, Irían J.r~. Indone.i".
T
h~. be~n
hi. plat"
induded to illustrak the tl','t can oceu' lI"ithin • po'ph)",)" copp ... r stock\\"ork. It is deli ,úteJ)' nO! for th~ faint he~,ted. The stod''''ork is so ink",.. that th~", is litl l... re<:ognis.,ble rock textute remaining. eo,nple~ d~ta i l
The lale.t slage ,ecosnisabl .. is th~ gre~n malachik ' ...."hing lrom su,fae~ o~id"tio". A eo pper ,ieh fluid has p.mdratc'" a small crdck dlong th~ co"t,ct of th~ qUolIlz "dn (bollo", Idl) ,,'SultinS in micro iniíll along tire crack, and ",ino' aheration of pink felds""rs. Tire obvious sitie" n'in (bottom ,iSht) has be en o"erpri"led b)' a "ackle style 01 b,eedation, d,"nn~l i ng fluids thr<.>ughout the roe k ."d p,edpitati"g p)"rit., (1",,1., )',,1I0\\') and eh"lcop)"rit,' (b,.ss )'dlo",) as micro-infilL in. compl~~ spiden"eb sloc kwork. It se.,rnS th.t pyrite pre<:ipil"tio" pren c,ln e.sil), misgu ide the obsc"..,.. The quartz
.ppeu to h,,,"e no a l t~ratio" compon~nt and ar~ compo .... d uf suga,)' s,ey a nd "'hite in¡¡IL Th~ir relatinl)' high ",idth 5uggests high pres."re fiuid conlrol? ,,~i,,(s)
The rem~ind ... r oí the plat" (top leít) is ",cupied by I'ery small blark mkrol'eins of biolile ocwrrins as infill . L6S <.>b,·iou' are the g'<:y/bl.;ek micro,·eio. ~nd
Jo
ORE TEX ll .. t
VOLU~ I E
3 OVERPRINTI1':G rEXTURES
ro,,,,d ... d graios of m"snetite, "nd Ihe "'m 'MntS of.
f1n<' grain,.,j po rphyriti, ign,..,IlS ror:k
(diorit~?)
Ahhough timiog e\"ideoc~ i••1 liltl~ contr.d i,tory, th" m~io r it)' of the black bioti l e "e in . ,,,t the maSndit". ThiS tin)' "'¡Sp )' rn icro,,~in ~tyl ... i, le')" typica l of .""ondar)" bio1ite in porphyr)' coppe". ~nd .lthough usuall), refe,red lo as potassi, ah.'ralion th,,)· ar~ a,tual ly potassic infilJl l'h~ bi"til,· a l t~r"tion occut<; wilhiu the mafie miner,,!s of the host ror:k. The "'lua, ... / ublong black elols in lhe 101' Ielt ,om.'r, " re prob.,bly hornblende con,'e'led t<.> fin" aggreg.la'S of biotit~. Th .. wnwrsion bhrrs the edgt'S of originall ), ShMP bord .. rl'
""'r
Th~ mag""tit .. thu> 'epr ... ,ent. the "arliesl stage of slockwork br""Óation/altcr;rlion. S""I I ,n i"o,"'in, are "isible, "nd 11", rounded ",ag"et ite sr.lins a lt.'ration of th ... host roek Icldspar;.
.H"
The gene,al sequ.'nc<' of stdges - masnet;le·biol it... · silica_""lph i d~s fepr~ sent. a dcclining ... linit)' "nd temper,'hrre ""'l"en",' (6OQ'C to 35O"C?) I'he inte". it)' of " tock"'o,king implies rcpeat.'d fr.rctUfins (sem i r.ndom sh a tteTing) by a p'o<;es> 01 ,epe"ted high e,,,,rs)" releaS<'. (e.s relea ..." hpl"siv~' Itydraulic u'·... rp'es.uring?). The ex.;ct "'e<:h~nism lor multipl~ fr,,,turing in porph),r), c"pper 'ysl~n1S is unk"o,,"n, It i5 qu ite conm'on íOf t\\'o st"g''S 01 identical char.ct~r to overprint ead, other, suggest ins a strong link btoh,'c<'n frJCluring Jnd fluid rele,l>e.
o I
1cm I
ORE TEXTURES VOLUME 3 OVERPRINTINC TEXTURE5 / 7
P LATE 7
STRUcrU RA L SUl'ER Iil.II'OSITION -VEINS, STOCK\\ORKS. I'c~ RidS.' SOulhN~1 Missou,i, Am",ic," , Spo"Cim"n don.1tro by D" R. E, Myen;
hiS pL'lc has b.,,,,n selc-rled lo as~iu ill"sl,.,I" Ih" .,ud d ll/ic"lties ~nc<.>unl"rcd ,,,' eu ", ilh in \\'ell dcr;ned slock"'o,k s)'Sle",s . The 'NI q,,,,,,tion he'c is ¡uSI h",," n,.my , I.. ses of br<-rdatiou .H1d inli ll a'e i',,"ol,..,.. '
T
com~ ¡" x l l)'
Ois'cgarding Ihe minule ,''''lic,,1 a .. eks ",hich look Hkc ' -c" I.'k "c'in" Ih" 1~I~sl Slagc i, clearly ,ep,e""nled by Ih" syslem of .. nsled (,iSh t lo Idl) ",'ins which c'mlo in a ,'Miable mine, .. losy indudins '1uarlz (\\'hite-gr.')' ",ilh ""SS al centre ,iShl) fine sr. incd g,ey m~leri~1 (m.,s,,..tit,,, sulph idc's) an,1 equ., II)' ~'l<' sroined sr~~nish a ,ca, (epidole!). The .t.. se is hf;! 1 domi".'lc-d, and it is diffic,,1t lo dis.:",n any alterati"" effecl>, The", i. a "ery Sood c" .'",ple (cenl re kft) "f an abrupt risht ansle I"m ",here the st"se s",inss i"lo. p'... e~isti ns ' -ein ",ie,,13Ii,)01 It is a litlle diífinJlI lo ""erlain the
ne~t
,t.,se Nck, bul it seems 1" be .' d",k-Io monled Srey (silic asulphide¡ magneti le) vein system, best set'n in Ill<' bollom lefl h.nd com... r WhCTC it clcarly culS both Ih," pink and g''''''' mal... riaL and is in «,m Cl't by Ihe Srey mal,oria l d ... sn ibed abol'e. This st"Se b p,esenl as small v~in, (bottom leH) "nd 3S ",ia"f,~CI " ,e "eI",orks (E-IV, aeross ",id sl id,, )_ AII,'r~lion is v~ri ~blc . I'he pink ",all rock ..... ms lo suf/t"r \'<.'ry litU", Wh,"rNS Ihe s reen «-p i d"t ~) beco",es d ."ke" Th" d ... ker " lte ,.,lion (silic~?) is paelicularly "ol iccable in the E-IV ',,_,~Iom~ins ",icruf'''Clu,e ndwo,k (c... "lrt')
18
ORE TEXlURf5
I'OLtI~l~
3 OVE~I'MI""' II ¡":G TEXTtlRES
The
~Ht
slaSt" is p robab ly Ihe e h'Mesl, being ",p""",nl~>d by Ihe ,'ery "i", .. 1 s"-,,,n (ep idole ) in bolh brt"eci ••'nd mierovein formal. 'lhe,e a,e nu" ..,ro"s exa"' f les of ",ell defin~-J infill (s"",n ('pidote, \\'ilh dark", S""'n 'luael>.) ",!>ieh e.. " be ..... n n"cleal in!; 00 ,ein \'.".,lIs .md . rou"d frasonc"ls_ 11 is po»ible Ihat Ihere i~ ~ome ",hiler '1"arlz in Iht, «'nlre of l3rg~r I ón, (boUom Ielt) . Altera lio~ assodalcd wil h th is i,,(ill 5.',,",S negligible, rr"gn",nlS ar~ prc>domi~dle ly pink .nd d ... k s,een/bl.lCk .,,,d Ihe brecóa app'°ars lo be f~l'1t slyle. pr<')b.,bly a,>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><- top Ihird of 11><- pl,lI"', Thc ,"pidote ,laSe clearl)' m-erp,inlS" d",k black >lage (siliea!) which ""'urs as bR-rcia frasmenlS ""d a, as)'mmelrie Ihin edse, on vein s whieh ha" e been r''Of''',,,-d by 11", ,"pidole hydmfr oeking_ Also rresenl in Ihe to p ¡eh hand quadr",,, a", mi"ule p i "k infill vdus (feldspor') which cut 3 du ll S,ey (silica-mas"elile) backg,ound nad ie-mesh nd"'",. b'ecc i., sysle", _ Thi s sySlem appears lo h.1\'c" • consice,able dark sil ic••, llc",lion compon,,"t, From thi s e,amin"lio" it ,,"ould «",m Iha l Ihe rock has been brokcn lO p and su bj ecled 1" h)'drothermal fl"id 'y,teons on ~I le .. sl six occ.sions . 1'-<0 doubl Ihe ,e"de, \\'oule queshon 100me of the abono, .lS il is clc ~ r l y a co mplex o'-erprintins situahon re'lu i, inS ,.... ,y good OO"",,,at;ou .,nd t"xlren", c."e . 1'h" spt-rimen has been induded to make e,aetly this poinl. Very ("""I,dlro pelroloS)' are r"'1uirro ''' Ile oriSinal "xl.: is a lilll, en igmalic, The pink cryslals are prt",,,",ably fddsf " rs, Iht, ",hilc' b lebs are py,ile, lI'ilhin .. \'ery r;"" g,ained malri . , A spe,ie s of po,ph yryilic "ok.ni, or porph),ry i~ ,uggeslro ,
o
lcm
I
I
ORE TEXTURE5 VOLUME 3 OVERPRINTING TEXTURES /9
P LATE 8
S-rR UCJURAL SUI'[RL\II'OSITION-VEI NS srOCI(\\,OR KS.
Red Dome coppc,-sold mi" c . Chillagoc. "o,lh Qt,.,..nsl~nd, Au> t ,~H ...
his pute h.os been induded "s .. good eumpl~ 01 a mull; pl~ o' Np'inlms Slcü ",or~. 11 .1.., ill"sl ,~ I"" Ihol e "~" ",ilh d~a,l )' "isible eomponents. timing ,elatio,,,hips dnd a lll"Ation/infill d i,li[\('lion ">
T
1'he toOst ,I.S" ",,,h,n Ihis ,ocl< is rcp'es~",ted by lhe prominert dar~, ,~,ti<:.I. e.. nl.~t ,~in 01 bomil ... TI..., S.n, .. SIOSl' i. "i$ibt~ at many othe, points as impe,si,te n t lines (mie,,,,,.,in.) 01 da . k Spo l •. O'(,1sio n.1 d a rk . poI S, on d "~I\"e alisn",enls of dHfuse "ein-!i".. _p ots/blotehes. The lalle, a , .. prt>miner.1 ""th,n a H',h,al )'.-110'" b.>n.d (g.,,,,,I) ')n tt,., riShl twnd s id ... This sl)'l .. uf 1.. 'lu .... is mmmon i, s k.,ns. .nd .11 of Ihe duk m.te".1 is m.,kins subtle e hanne'",. }s. Th .. i d enlifie~llOn of inlill 'c,sus a'le,.lion is impos.ible. "lthouSh il is ell',,, ,hM mosl of Ih,' 'pol s a,e "1I .. ' '' lio,,. So ",e inlill m~)' be p'ese,t in 11", nl. i" ,·,'in' The p .... «·ding stoge i. '''p.e ..,nt b y Ihe narro", mi('n¡.-".,ns (g'e) qU.,t7) ",hieh run f·W .nOSs 11>.pIAt .. _ Th .. , .. ur inlill ( m.lehin~ "'Allsl. and b.-st 'ep,~n 'l'd di Ihe ">p 01 Ihe plate. CtOM' inspe<:tion 01 Ihi . '''Ii'on ,,'''eals thal d" s pite inilial imp,essi~ns Ih~ 'lU"rlZ "" in d oes "01 .,elu"l ly eul IhrouSh lh., lK>",it~. Similar ,elation,híps a 'e more OO"ious lo", ard s 1"" boOM' 01 Ihe pIAI.·. bo,nitf .od qua't~ ,e,ns o,-c,p.int the 'di"", "ague d iffuSl' l ..tlow ¡;~",,'t ,eins (,iSht h~nd · 'c,lic. ). antl lop lel!
./O
th~
0Ii:[ TEXTURlS VOI.U\fF J OVEIU'II:INTING -r EXTUIo: ES
Al Ihi . point tif.· b.·come" diffic"ll! Th" obvious ,,'mdi,~ns m" te,i.l s"re S,,,,,,,I (red-c" nl .... \'<'i" / I~)·e') ""d ",hite (",ollaslo"ite). lVolI~stonile dCdfly ~uts OH' Ih.' red sanlel (1K>IIom.ldt quadranl) . C.,dul iMpedion 01 Ih .. ¡;e"..,.1 ",hile eolou, of Ih~ roel< ,e,uls g,ey ' _o"es, ",hieh ~ugge.1 th~1 mass """II,,.lonit.. ~It"r.t,on of ~n u"k"o""n ho.t roc~ (,ilÍC«u~ <. rbon~ll· !? ) h"s o«u,red . In l ilt/ al te,ation d ist i"clio" of t he "'oll~ s t on i te
Th.- s/'ort lo"" paugme;;,s ~ l. Red gamet "·,,,s (dllerat,on predomi, ... nt, lextur.l , . ri.ttion su¡;g~t s S(>me infill?) 2. D,,.k !i"",n py'o'~",,' eins (a lte,al''''' p'l~lomi""nl? N OI ...",11)' vi,íble). ). lVoll,lstonile (mo.lly.s alt",.,tio". nlinor ;nlill) 4. Ydlo,,' g"-""" gamn , .. in. (mosUy a, .Iter~tion ). <;. Qtu.rtt ,eins (infill). 6.1I"mile \'eins (m<>Sll y ~s alte'~lion , po~s ibl )' miJlO' in filJ». Ob, iQu s ly "'o'e 'f'«inlcn, ~ fe ' equi'cd to ~chi" '-e 1110 ... informatio" O" ti .., e~,ly slag"', ."d "",11 ,ocl< roml""'ition . The s!,,-,<,imen is 110",,,,·,,, a ,.ery good c~~mrk for hani"g obso.-r>AtiorYl ,;lills!
o I
1cm I
ORE TEXTURES VOLUME 3 OVERPR INTING TEXTURES 21
P LATE 9 STRUCTURAL SUPERIMPOSlTION-VE INS. SUSl' lcrON AROU51NC - WA NDERINC CENTRA L
INFILL
Jumn. li" mi". , rn·in .. b~nk . norl" Qu.... nsl a nd . Australia.
hiS spt'Cimen kas !>toen indudO'd \o ¡lIustrat.. tha! m 'err .inti"g \'I.'i" s ltuC!u ("t'!; can ~ cuns iderably mOr.. com?I ..~ lo unr.,-.. I th~n is popularly s up f"""'d.
T
It is .. I",ay. gO<>d t«hni,!"", <""en! through 10 th<- ..~rlirst.
lo
wo.k from tite latesl
On this sp«imt.'11 the lalest en'nl seems 10 a series oí
inconspicuou. tiny pa l.. bro ..... " ,·.. ins (sj d ~ri l .. ) ..... hieh a .... btost M'\'n in Ih.. lo ........ «'ntral regíon w h<> .... tltey cut through the da n: grt'y ",hite zone u w"tI as bolh qua r lI "r j n~ and ¡he da . k bla .. k (q ua rtztou . mali" .. ) ,-.. in •. In this , ..,ion th .. y a ... ¡n'ill domina ted and wt lhoul al teration h.;olos. How~,,· .. r, this is a trap for IIw i ...... perimeed aS IN s;IOrrK" ,-.. illS in Ih .. uppt'. ' .-gion produce ¡'«'gula, alteralion frins'" of o ra ns" (rUSly? 5 id ~ ri l ... ) and pa l ~ crea my o ra ns .. maleria ls (pri5I in~ sideril~?). This appe~rs lo be al lhe ~pense of gret'l1ish scricite in lile twm rocl<. Tho.> laltf>r 15 sorne form of '~Id sp~,h;c s.>nds'on~. "'h~re th ... ~ldsparsa ... .....-icili,...J (Iop~).
7. 0n, of rflal ively un a ltcred hOSl . A v~ ry g""d examp le of a fal .... , .. nl ra l cha nnrl ls pt\'Sefll, wilhin lhe Io"'er narrow b lAck \'ein. CI""" inspectk>n ~',,"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
" ~ ry
Thu. lhe alleralion US('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
SIaSt (Narnel
Infill
AUt.alion (Rack type oU"redJ
Struc\u r. 1 Style
Commtnl
Sid erite
Sid erile mm sale
Sid"';te (sericitise
Microvein nctwork mm srnll'
SmaU sc:ale
Tounnaline
Tourmaline mm sal ..
Quarlz lourmaline ("";dtise
Subparallel s)'Slem 01 small discontinuous
Alleration edeosi,·..
Nil
Subparalll'l v..inIets around Icm wide
"'"~lourmaline
11
This sla ge asa in lIluslrales Ihe n,"'" for ,..ry cardul InSp«tion of seeminSl y eross cultins '·fins. as Ihere are many exa m ples wlw." lhe lourma l i~ \'elns cu l .. arlie . '1uarlz ,·.. ;n~. bul lurn lO qu a.I ? ¡nfil! Wi l hou l a lt c.alion. T hi s ;5 common in m.n y si lua lions a nd can ea511r Si"" Ihe wrong ¡" p ression lo a superfid a l glo"'" .
Quartz tourmali .... cassi\t>rite? cmscale.
ORE TEXTURES VOUJME J O VERPRINT1N(: TEXTU RES
mkrovrins.
Fluid pres~ ... high?Combquartz
o I
1cm I
O RE TEXTU RES VOLU M E 3 O VERPRINTING TEXTURES 23
P LATE
]0
STRLCfURAI. SLPERI¡"II'OSlTI01\'·VEI1\'S, PARALlll. RIoACfIVATlON. Un~no ... n too mi"", E"'an K~ng~'oo Itill~ hnficld, nouh Qu..-.""'l ......
TdirlicJlty
hi~ ~p.'Cin"'n h~.
Mn ",1,'Ct,'" to ,Uu~t,~t~ tllt, in establishing o,~'p,ill, i llg , .. l .. !ionship, in situ ~tioos ",he'e infill ;< "ot .ccom pa -,i"d by sig nific."t ah"',1tion . 11 al . .. 11I",trot",. llIueh o,·"rt"" k",d ,¡t ua t ion, lIt t lta t Iddspa thic .1 11... alio". a,e I,~q,,,'ntly a«om p •."I,,<1 by leld.p,lthic Inlill.
The ",.11 ,ock (botto m le/I) is comp ..... d o/ pat.· (pillk / wh,te) fin" g,alned g,anl te , compuo.ed mo-tl)' 01 leldsp .... (pmk / " hite).r>d q".rt7. (grt'y). Th, s has Mil altcn.'
!4
ORe TOOUR~,S \'OLL'I E JO\'ERPRI ,' lTl'IJC TUfLKf,S
Sobseque llr Iraclorlng alo"lI th~ c .. ,,"al a"d ma'gi"al ,egion of the 'eln, ha, pr"O\-ldt'" ~ lor Iluid dcposl llng oc i~"-'ntc <:>f Ihe pa Icr albll" rleh s li,·" r. (top Idl) m i ~hl N' p."li. lll' ,ilici /i,·d , Th,' timing 01 th" 'luar t ~ ,t .. se is a tilll" d lfl i(ull 10 di"e", •• II appe a ~ 1<> h~, ·e (assit",il~ ( dark)~ . ~ pa ,ti,llinins .1 5<'\'('ral poin l", Ho"·.."", on balanc.. ,1 "",-'1llS mo,e prnbdbl.. tha! a hillh pre,su'e fluid ha, .."plo'l.. d p,e'-iousl)' oceupi",d ,assi l~r ll e rni(to,~iR5 ~nd . ,mpll' roreN (hyd ,of,aclo,"") I.... m Opt"n. Thc p'ominent o, .. nge l~ye' (lower mlddl~) is Ir"n .tal"iog ,,,¡aIN lo g ... u"d " .. Ier l"'reol~tiOfl .. long the ni" mMgln .
o
1cm
1
1
ORE TEXTURES VO LU ME 3 OVERPRINTING TEXTURES 25
PLATE
11
STRUcruRAL SUPERlMPOSITION-VEIN, BRECCIA
Mt Isa copper-lead-zinc-silver mi ne, Mt Isa, no rth Queensland, Australia.
hiS specimen has bren selected lo iIlustrate a very clea r c u t case of overprinting relationships in b reccia formato
T
The mast strik ing feature is the com prehe nsive ly shattered crackled white material (dolomite) which is associated w it h a network of m ic r ove in s con ta ining cha lcopy rite (ye ll ow), and dark material(?) . The m icrovein network Iinks to more sub sta nti ve blotches dominated by chalcopyr ite and mi nor pyri te (paJer yellow). It is very difficult to determine w helher or not the cha1copyrite represents ¡nHU or alte ration . This is a cammon problem with chalcopyrite which very rarely forms c1early recogn isab le c rysta ls. The substra te dolomite (white) also gives very Hule help in lerms oE providing clearly recognisable crystals projecting inlo potential chalcopyrite filJed vugs. Sorne oE the ragged edged doLomite and smalJ fragments? (mid to lower right) suggest that dolom ite may have been dissolved prior lo chalcopyrite deposition or simply altered lo chalcopyrite? However, witho ut furlher data it is impossible to be certain of the proportions oí infill versus altera tion, concerning chalcopyrite. The writer would suspect both a re present.
The fra cture system controlling chalcopyrite also cuts Ihe dark (si liceo us) fragments, a nd althou gh no l
26
ORE TEXTURES VOLUME 3 OVERPRINTlNG TEXTURES
lotally clear may link w ith some d irty grey dolomite m ic r ovei ns (bo ttom r ight) associa led wit h grey spotting (alteration) within the fragment. The relationship between the dark siliceous fragments and the white dolomite is especially interesting. Taken at face va lue there is a lmost no evidence lo suggest thal the fragments are being altered. They have sharp edges, and there are several exa mples of fragments which a re microveined by dolomite. In these cases the s ha r p wa ll s ca n be ma lc hed, a nd /o r parlially m atche d , leav in g Ihe overa ll impression o f h igh press ure flu id jacki ng w ilh s ubseque nt coa rse dolomite infill. The current concepts at Mt Isa which r eg ard mos t oE thi s do lo mit e as a lt eratio n (replacement) certainly merit re-examination. The siliceo us na tu re o E the fragmen ts is a lso ve ry suggestive oí alteration prior lo fragmentation. All of this suggests a th ree stage paragenesis oE: Early dark silica a lteration (channelways uncertain?) Major fractu ring and teclonic brecciation involving a high pressure flu id w hich preci pita tes dolomi te (moslly infill). Major fracturing and brecciation/crackling linked lo the introduction of the copper rieh fluids. (proportions of infill v alteration uncertain). This specimen is typica l of much oE the cop per o re bod y. Obviou s ly so rn e goo d petrog raph ic observation is required lO sharpen this perception.
o I
lcm I
ORE TEXTURES VOLUME 3 OVERPRINTING TEXTURES Ti
6
F IRST ORDER CRITERIA - STIW CTURAL SU PERIMrosIT1QN.
811 CCClA (f IlA G i\IENT S OF EAII L Y ST A G I, i\1 1N EIIAUSATI0N CO l\'TA1N EO WITl-I IN LA T ER ST ACES). TEXTU RES A N U 1'1I0 8 LEMS PL\.TES 12-1 5
... K..."I'.'''on ..r '" "p,,""nS ,,"h,'ns
, h,.
~o<,
.... . ,"."""" ~.II d.f,""¡ "u~
.....
,,,'h 'h. b"..""
,,,, boo)
.~"."".d ~u,IJ . ",11 ,.,J,I" ~"h' , ~, "'I""~
1... ""S'""'', o .. Hu,d, 1I ) ~ 'oO ......... 1 .. ~."II) ... "11. i • • U.... hon 01 bolh I.. , ..... " . nd . . ....... i, h p, ... ,p' .... ""'''''".~ ,,' ilh,. , .... 'OId, f lu ,d 110 ..· , h '''u~h b»I ... II) , .. ~ ¡...S"", . p,""u<,"S "') .".. '" d.. ,,,.,,,,,,,, ,,' .. 11... ,,,,,, 1,,,1;11.
'''K'
""h .. ,,,, .. lo,,",, b_ti.. ; i, 1""1"""') OH" ul ,h .. "'o', JHlk u l1 ,<"", .. 1
B..,, " .vd,,·, 1"'p",· i.I ..· f. ull .. 1''''0
,..,.., .. , .... In " ·,,,. omO<
t>m"
~y
Indo-N
'h ... . .. num"o\"'''''''rl .... h ... h ''''d .. o,.... ,," no' . . . n ,r
Ju"",, "'n'
e...... ,;,,"
' r .... . ·
"..". 01 p«>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".
'"'''''''''' lb.
h,~hl> b,o~, ..
'o., ..
u.u .. l.. lI .. n~1'
"n" .. ,1 011> ", .. ,.d ,oel Th. hoShl) l"',m .. bl. . .,,,I!, r",m, .. 1"',1«1 Jocu'
~"." « '''i"n
.. nJ "eW fluiJ flow , • • mn')'ntl""l: ~tu.." , Tht 1" " .1', .... o... "ud )'
pmd_~f'Ir' "~,, flu,d "" )
I" tI .. II,' fon.... " .." .. '" o«up) , .... 1'><'" ,'00.1., lH .. ,l.orlv ,1 ... ,., .... "' .... . 1... 1"'" """"'C ........;0.. (... inliU) ... .o.!MIo. . ..... of _ _ 1 Tht F""""'"
u""'.......... --.:...
... )· ",,~ ...·...I -
e............ po-.. ....o.,.,¡,., r. ) ~""'''' .11.-1 1r"S"""" (b) O .. " n<" ~n
...........
h iZh l . . .....
I."!i""""" """ ~''''I.I,'', .1_ "",.....
o..t"","",
"'''u...,., """ ......
uI "''''' ..... """".p, .. ihr_ • J d ) 'RI,II I . II "."~" p. i".,
1<)
\\"ho. "'ull ........ ' .. 1I'
.".".i... 11 .... io •. "
<.o " ""'_
.1> ... ,"", ¡".~"'5' '" ~' h:':b
inf,1I
.."""",Ir dil''''ull 'o dr
l. <""'I" n
. iluo""""
~'~~h
b«« '. "''''P''"''"¡
I~" "b, .. , .. i. ,.","," . J,; .. d 00 'm,,'
" ..... ' .1>0 I"'''p.... ).. io
h.~'.·
H .. I)· ,,,
1"'"'''' ""'_ ....,-tI ........ u' ,I ...", ..
11 ..,.-10.. ,""" "'" "" ~I\,,<,> . ... _ ... oou •• .on.d , .... """""", .... <.... Ih........ pp li.~ ." Ih.....,.. bo~. Un .... h"J ""'1" "'''''1 .. <."pI<, mul"pl) ... ,,,, ... J b,,,,e .. '0 .... •• ~u... . ~ .... " ,. 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.'
bot",,,
hiS 'I",,,i,,,,,,, ha. sel ..dcd lo ilh,,(r~l~ "''''') ,,1 Ihe p'<.>blems .ls>o<;ialcd ... ilh '" cr prin',ng in brecd .. """k TI.".",.", th."", rh ...... of hydrotl ... ,m~1 /luid i"I,oduction i",· ol\'t'd. ""d th, .. c Iy p u 01 l,aCl"rins / b ,{'(ci~ , i"n . W"rking ... ilh br~.'cddli"" is f" ',!IJ""!!)' " ..,eh l11"r~ di/lictdl Iha n i. s~ncr" l l y conn'i ,·ed. a nd 111." )' b , .. eci a s a,~ o,"c,lookcd . Read,,", a ,(' i.",ile"'" lo les! lhei' obse,\'.ui"nal ~k;Us "" 11>(" oppo>it,· p ldt ... belo", 'Nding the d<"la il bel" ....
T
The I~ ,I . I.l¡;" i. ~,,"¡Iy lhe mOSI ob.-i"us. wrn;lsling 01 C.. It:.lf ( ... hll,·) .. nd minor siliu (S''')' ) i"foll ... ilhu.,t • h~"'.liun. orrup)in¡;. c ..d,'" si)'''' brKri .. tiun. (lhi~ SUsc is .""",11 )' ",·t't'pO><>ibly 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 l<.>gdher 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 u<;1. is de.. rl)· in"<:>!,'<-d, L1~)' '" .h,..... tiQn .
Serici','
l8
OR E TFXTUIUS \OlL\l F } OVERI'II.INTINC !EXTloIIFS
",., mode ol b,<"'e).nd fluid fl".... \Vhen Ihis b'N'Cio is elimin • •cod lh ...... 1 oi lhe rock ,~"'ai"s. and is ,,, mp,,se d 01 ",~II d"fined da ,k Ir.s",enlS .>nd s,ey silk~. 1),., fr~smt'"ls ~r<.' ·'•• nil..·. ~l1 d a r<.' ",ell se par~ld ) ' ·.ri.-ty. It is possible Ih.1 """'" '¡lidflC.li<>" ('1 uarl~ "~Ining) OCC tl"t.'d bt'/"r{" thi S b.{'(ci~ t ;on . II thiS w~r.. so. il ..-ould i"'pl)' anolh...- pIl. ... prwa',·io u~I)'. \\' ;s" obs"'T\' ~' ",,,,li d mo,," ~nd 1')' lo lind 1", ,, ",·,'rp,i nled maleri.,1 ol lh .. ,-, ;,,1)' $I.'S .... Ho"'~'~r. tlw .., i. "n"" gh ",ithln Ihe pl.u,;, lO 1,·.,,1 'he lo " usp""t ,1Il in""s i \'~ b .. pi"" " ,\Vi"",,, ...,,t'
,..(i.,
Qbs<,,,.,,,
SeIe<:li\'e ~s ... y¡ng is ""1" i,('<1 'o I,.Ü Ihe gold . Th,' middle p y r ite ri(h .t~ g .. Is th~ mOSI probabk c. ndid"te.
o I
1cm I
ORE TEXTURES VOLUME 3 OVERPRINTING TEXTURES 29
: PLATE 13
•
STRUCfURAL SUI"ERJM J'OSJTION (ANO MJNERA L SUPERJ.\1 POSTTION)· BRECCJA R.Wen5wood goId mining district. north Qurensbnd. Au~tralia (A",a 2 vrin Carpentaria GoId).
hiS sfecimcn has booen included as an example 01 comple x inlill overprinling and brl-ccialion whkh refl~-cts • long history 0 1 deposition within " "ein structu ....
T
\'Jith sit .... tions 01 this style it is always ,."')' diffocult to know whe re to slar l. The working bae k wa.d~ principie (from Ihe [atest lO earliesl) is nOl always .pprop.... te. It i5 oftCf\ mo ... eff~""ive to settle 00 onc: s mall ~""", t tha t i. el...., and then selec! anothe •. Thi. can oh en I>(! done by working lTOm dear crystal sh"pes to s~.., the n~xt mine. al to be dcpositcd, or allernati,'e ly I. om a laye. which ;s coa l ing eilhe . CT)'sIals O" bmken material. A mOSI Ilriking lealu", i~ ¡he s ltongly brecdated material (lowe . Idl hnd edge). This ;, pn.'dominalcly fi""ly comminuted s phale.ite (block) and .rs.nopyrite (silver) within a black (siHca?) malrix . The f. agmen lS a re s harply angular lO wel1 . ound.>d, 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 dd' along the mMgins, Thc a.-s<:nopyrite rim is directly o,-er grown by chalcopy . ite (yellow) a5!oOCI.tw .... ilh occaslonal good erystals sh.pes 0 1 pyritc (role yellow)_
JO
ORE T10XTURES \'OLU~IE 3 OVUU'RINTINC T1XTUItES
D i. ee! sequ cn cing is difficult he re. Hu the bcen fracturcd to fonn isoIated dumps? IVhich C.me first. chalropyri¡e (If pyri le? The ~uthor's p .... le..,...¡ interpl"1!1ation i. that t.... arsenopyrit" has bcen disrupted and lhal t.... pyrite Í!I slighUy earlier, in • pyritc-chalcopyrite IMring,
~rsenq>yrite
The p.lc bulr material _ oiderile? (ri¡;ht hand ,ide) i. quite cleorJy ;nlill .... ith good tri"ngular lextures, nnd eq u.lI ~ dea r ly som e 0 1 the ".rlíe r ~~yri l e/pyri l e/(halropyri l e has he b~lf sideri le. but prcdale? tl>e ,'iolent b"-"CCia lion . Thei r ?rccise a.sodat;on is oot elear. Ot,..i<:usly. few more rocks might elear up iOmc oí Ihe p,oble!llll. Howe-·"r. t .... s mor¡¡asbo.d approoch has pJrtialJy ~nr.veled tM problem, whkh is one 01 v~g l il ling wilh per iods 0 1 se lecl¡"e f. agme ntat io n . Th~ sequ en Ce appeo rs 10 be oph.leri te (possiblc fr.gmentation) a.senopy.ite ( proto ble f.agmentation) pyrile -c h alcopy r ilc (dcfiritc fragmenta'ion) sideri le-c.Jc i'e (e~plosive fragmenta t ion) dark . ilíea . Mueh 01 the fragmentation is probilbly in response 10 high f1~id prcsu res w;thin ,' ugs ratlte. than direct tc
o 1
1cm
1
ORE TEXTURES VOLUME 3 OVERPRINTlNG TEXTURES 31
PLATE 14
snwcru l< A L SUPlo/U \11'OSITON (AN D Id IN EI
Thr-' frasme"I, a,~ OO'·ioo'ly mix~xI, and el",", lo ""m.. nf Ihci, o,igi n> a ... ~"'m in Ihe t<>p .iShl 'rgion. liere 1.... mot lled bufl gr'ff<.",n b ro~e" I>y • ",hi t,· .ilie. b,...,,';' gen,'r. tion prior 1" II\(' gil")' g"",n SilKa'
.bo\.
T
hiS sp«im~n has 1><.",,, indudctl lo i1Iu~t. ~l e the prime valuc of br\!<'(";a in pa r~gcnetic sc.-q uen<:inS'
Th~
\\"orking principl~s in·.ol,,~d ", ith breeda are finol l)' to dete,m;, ... the m""t '•.'« "nt ..".-nt, and then lO ....0.1< p'''8~i''eLy b.>ck"·d.d s "'Hhin th" ,-"mainins f'.gm ... nls. Th" p'oc"," eont inu es as diffe.ent fragments ""'''''''' isoLotOO . ' n eompl,,,, b"""'-;atinn ,1 is s ometím...,. mo.~ p.a'hu l to jusI " ·o . L in s mall "'-'S""~HS ( .... he ... IhinSOl a,,' elea. ) and the.. piea !he " .""lIs l<.>get'"", '11", ",os! "",ent .. \'cnl on Ihi! p l .lI~ is the eent" ,1 ",hilc
n-i" tr.,, ·~ ,~in¡; dia¡;on,lIy ¡ro", top left to bOllom right. The pielu.e is a hit '", confu sed by the o.ang~ iro" .Iainin¡;.. bul Ihe ,("in . ",,,ist. of cenl,al whi l ~ silÍ("a ",ith a tining of gre)'-)jI"t"Cn-buff l1"orite. Al Ihis poinl thr situaHon 1>«0111<"< fOnfu,,;ns as thr t,,·o sid<-< of Ihr lining do no! n.. "h "try \\"ell. A thin 2011(' ¡Iop Ie(t) of ne;lm y l1uo"te runs a loos t.... lop OOge oIlhe lo,,"e. linin);- ,md although d.ffI"ult to I.aee ",-""mS lo cut off a vei n of p., I" g,cy -sr"" R-b" ff (Ir", .i lc I,."",-,.ing diagon a lly Irom bOllom I,'fl Ir) Ir)p .ighl. TIte ",-"1 ,.,sull is • dl"g"'" of confusion as to ... heth... the<" a,e O"" O, t\\"o gen" .. li"ns "f Ihe g,ev"g",en . bufl Ouorit" (1,,"0 ~re ,usp.>elt.-d ). "'o,Ling b.K k",ards I>«ome. d ilrlCI,'l hum he,e. lhe basal sr.-gm .... t (b.Is.- of pl~I.) ronla i", 5<','era' ( ~"" Y ,,-,1',t" t.... comple~ity sn-m, lo b<- a coIIt-n.... , infin p.>C~S" .
J!
Of;:1 rt:XTURESVOt.L Mf
}OH Rr~l"n;';G TI :xruRfS
,,,d,
lhe diffocuh brecc'" s,tualio" ;s ""en fu'l...... e'lended, ",ilh th .. re .. li... tiOR thal .. Complel e suge 01 pal .. """,-"".Id g"""" nuonte " p~1 110P edge). 1'111. IS fuI by lhe la le Slage ,'''¡ns-, .nd app"ars to d"~il on lop of Ihe "·oIlramite ddrl< sHit. stage.
lI.,.
i• •,mple ~\· id.'nee "n this 1'1.11., lo ill" .I •• minim"m 01 ¡our , tag(" Df b'....:r i.t ion and infill. n", fin e g •• in ed g.anile ha. been f. as men ted and inlillOO by srey s'.... n .il ca 1
Gi",' n thal Ih,·", , ,,,,Id b~ t ",o genN.tion < of Ih,· I~tle., and Ihal bolh e .rly sili<: i¡i<:alio" ~"d se,ici l isa h "n of the i n ili~1 g,~nile ",all ,ock. art' po.sible, Ihe'e could lit' a S ma"J' aS se"'n sugrs i,,,"ol.ed! Ob.;ou sly "",.e .... mples ,,"ould cla.if) som. of tt... que~lion •. 1I ~ hould be nOled th~1 Ihe ,,"olf.amite-s i1ica Mag." qutie separ .. l~ Ir"m Ih~ I~! ~. Iluo . it" sl as..,.. Th. s p~-'Cimen ~o",es f.o m • '·CiR. and asain iLh"tr_In th" pro!",n.il)' 01. dn~ 10 co" st.mtly fo "" foc,,1 p"i"ts fo' rdragnlenlati"" and lle'" flr>id 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 . 5p<-'Clm
T h .. pro bl .. ms bn:ome e'- .. n mo .... ' ulr ,,-h"n the ,-.. i0<6 ~li,·<'tS 01 m~I".i~1 ~u.rouOO,ng lho, Y sh"pelCh.
""'j'
"i~
b"~ n
T'_'Ir lo. carl'ful obscn ati.,.,. I! plal,' t..s
indud .. d 10 ¡l lu s tral .... 11...
~I".. "",noS lo o/ Ihe f'ust ralions ;,,,.ol,·,,d ",,;th I"w ans,", CTO!II> cutting sili<:a ri<:h , '<,ins.nd al>o 10 {")o.hib,1 d,/(kul!! in obs<>ning br<"Cd •. Th .. qu..slion lo bl' ans"",e-d is hu... m.Il}' Sldges ... "" prese"r? ~ho .... >0""('
,ic"
The pIJ!' ronl,,;n" mullir'" S<""'fa lions 01 s ilic:. "cin,¡ ,.,,,n,: 01 whio:h • ..., 1""01,'00 WII" acromp."'y,ng .h"•• Ii,,~ . Vision is parliJlly obs."u'cd by ... y~lIuw (iron oxidc) sl"ini n g duc lo ",,,.U,,,,i n g. ",h,"" ~lIrfici .. 1 nuid s h.,'c sele.:ti\'Cly "I..,ng "c¡" m"'gi," ,,,d eI"'""h",,,_Th is is p rnmi'\('111 in Ih .. ",id leI! o/ ti", plO IC, ddj "eenl lo a prom in""l siliu i"lill \' ~ in , Th;~ p'o",in ~n l silic .. ,' ~ i n ha s a Y Sh3p~ d b,."chin$ lo.m ""d is disliogui,h<-n '1'1... !.ock of goug", or induder ~"U<.,.I it ",as orig,n.1l1y _ "'00 01 ",1.li,·..!)' .imple ",",kinS •• t"", thoon .1 m.jo. displ.d,·~ f. ul!
c".",,,,,k..:l
1.0"".
T h~ lo"'tr b'. '1.dll .. ltn.. romb qUlnl ,do,. oo un 0111)' be t,.oce(! "';Ihin it. 1)0 1.... )' "'f"">""ll lh .. e""", clIllinS sl.se in 1"" boltom right hard romn?
11 lltiro .1.S<· is slrilinslr n.·pn>S<'flle l h ~ " •• ious ,ilic~",,,s componc nls.
j4
OKElllX luRES \'OI.U~IE30\'ER I 'K ' '''TINC I LXIURES
E.-e" tllÍs d a. k m~l r Ti.1 on cloS<' inSp .. 'lion i. fTasnICnl .. y and rons;,1S of da.k g ..... n (chlo.iIi~ m.t .. ri .. l) (on tainins ,t'ddi. h mi ....... I. (c.>~i l "fLt~~) ",h;,:h ""'y link ",ilh lhe ",h;l~ s.lica lo the ímmedial.. left """,h also cont" ios t.... n.od fpln~ mlne.al. Thls.1I suue;ls anoche •• laS" of .ilica(C.~,lc,il .. ), "S6OC;"I'-'
,,,el.
Al Ihis poinl Ih .. ob"" .. ... ",m p.obably h." r eolla p,.,d in ( o nlu.ion, ",hieh tlt" .ea..,n for sel«linS Ihis pLaI~_ ()b"ioos ly thtnss. ", no!.os e.os)' .os lhey """m, " ' ilh ow.printing ,,·,os/ bn-«i.:tlion_ More ,.,(I:s",oold help!
"'.s
n... ro""I!! Lnl<'.p ... tation Js: l.
2. 3. ~.
5.. 6.
F.agmenlal metas' .. ) ",,,ke ",all ,
o
lcm
1
1
ORE TEXTURES VOLUME 3 OVERPRINTING TEXTURES 35
7
SECON D O RDER eR ITERlA; SUSPIClON AROUS ING TEXTURES A N D I~ ROBLEM S A SSOClATED WI TH VEI N RE-OP EN I NC, I NC LU D I NC-QVERPRI NTI NC I~ARALL E L INFILL, ALT ERAT IQN- INFILl M ISMATCHINC, I NCONSI STENT ALTERAT IO N SEL VACES ANO AL TERAT ION QF ALTERATI ON. PLATES 16-22 7.1 The following section of illuslralion s has becn st>lectcd lo ¡lIus tra le slI spicion aroll sing or second orde r ,ritería.
The majorily of Ihese occur where prce x i s ting
c h ilnnelway
slru clures
(us uall y \'eiI15) have been reilcti\'illed . The reac ti \'ation o( planar structures, naturall}' foc uSl's Ihe failure SUrfilC('s in
pilfalleJ, o r St'lllipiU.ll1el, nli1nner lO the original fracture. Mosl common! y
il
faiJ u re occurs along \'('in rnargin s, or directl y up Ihe ce nt ral zo ne, and ranges froln no n di s r up li \'c s imple frilclllT(' propilSillion lo di s rupl i ve brecciillion. In mos l Cilse s, Ihe
PLATE
rCilc livil lion will il lso resu[1 in new frilcture s urface s within Ihe sur rollndin g hos t rock s. The se art' especiillly co ncent rated afollnd Ihe fr inge Lones of tht' original fracl ure. Mo s l of Ihe new fea lures are bes l approached b y loo kin g for , and colhx ling s pcrimens whilsl in Ihe fie ld, and this s hould be Ihe first appf()'lch al normal vis ual sc.1Ie. Thus al outcrop or drill core seale Ihe first aclion s hould be lo move away from Ihe cenlre of minerali sa lion, and seck isolated microveins within llniform hos! rocks. The objec t ive is always lO Iry and d ecide which infi ll assemblages belong lO which alleralion a sscm b l¡¡Scs.
Th is s pecimen ha s been included lo illustrate the common s iluation of re p ea le d re-opening, and infilling of Ihe s.l me fracture system. 1I also ilJustrales just ho\\' difficult this ca n be lO dec ipher. The problem is compounded when each s tage con tains simila r componen ts. The narro\\' ve in sys tem tra ve rses a s li g hl ly 'wea thered ' granitic rock, composed of quartz (greywhite) and fe lds par (pink-orange iron stained) \\'ith minor biotile? (rusly brown). The fe ldspa rs are slightly argillised and minor acid leaching has occurred v ia so me of Ihe crack syslem s. These Irave rse Ihe vein horizontall y and link lo lo\\' angle fractures (lefl hand side). No clea r alteration halo borders Ihe vein system . A close inspection of the vei n indicales Ihat it conlains al leasl three separate components. The upper-left vein SI.."Ction is noticeable, as it contains very we ll developed wh ite quarlz crysta[s growing irregulady from Ihe vein wall, succeeded by p y rite (pale yellow). Thi s region is close ly associalcd wilh
OI~E
Ir Ihe obsen'cr only has an individual slab /specimcn of rock, and is unablc lo mo"c Ihere are Olany helpful slIspicion arous ing circ llOl sl ances (set' sl'ction 2.3).
16
SUSP ICION AROUS I NG COMP LEX OVERPRI NT ING, PARA LL EL REACTlVATlON, STRUCTURAL SU PER IMPOSIT ION-VE INS. Ravenswood gold mining district, north Queensland, Australia (SYC Pit? Carpentaria Gold ).
36
Forlun ¡¡lely inf ill assc mbl age s .1fe usuall y les!; affcclt'd by changes in hosl rock Ihan .lIteration asscmblagcs, and in thl' rilrc cases of multiple hosl rocks it qui c kl y beco mes apparen! !1M! \'arial io n s i n aheration do in r.1et belong lO onc mineralising ~ t agc and s imp ly rcflee l Ihe chcm is l ry of differcnl hosl roc ks.
TEXTURES VOLUME 3 0V ERPRINTING TEXTU I{ES
small elongate brown components (mil d ly oxidised marca site?). Thi s asse mbla ges can be Ira ced a long mos l of Ihe lefl hand s ide of Ihe v('in , and Ihen beco mes vague, bul re-appears in the bottom righ! hand edge. The botlolll righl hand occurrence is clearly c ut off, by an assemb lage of slightl y g reyer silica associated w ith arsenopy rite (sil ver). This ca n be traced a long mosl of Ihe righl hand side of Ihe vein, and is visi ble again lo Ihe righl of the fir s l stage assemblage allhe IOp of Ihe plale. The arsenopyrile-grey q ua rtz slage is in lurn cul by a noth er vcin, w hi ch is le ss \\,e[1 defined, and com p osed of occa sional dark brown (s ph alerile) cryslals, associated w ilh paje buff (siderile?) malerial, and probably pa le yellow py rite and quartz. The relalionships between Ihese stages are oflen very confll sed and difficult to deci pher. Indeed Ihe alllhor is by 110 means positive Ihal Ihe above in terprelalion is to ta ll y corree!. Thi s serves lo illu s trate ju s i ho\\' effecti vely vei ns of si m ilar composil iol1 can ' hide' as Ihey o ve rprint along the sa me controJling slruclural weakness. Once again inspection of more exa rnples is required lo confirm initial sus p icions. This exam ple also illustrales Ihe need for very carC'ful observa lion. The vein is gold bearing, an d it is nol cerlain which of Ihe slages is gold relaled!
o I
1cm I
O RE TEXTURES VOLU ME 3 OVERI'R IN TING TEXTURES 37
PLATE
17
SUSPIC ION AROUSING - COMPLEX OVERPRINTING, PARALLEL REACTlVATION. STRUCTURAL SUPE RIMPOSIT ION·VEINS. Ravenswood gold mining districl, north Queensland,
Austra lia (Buck Reef - SYC Pil, Carpen taria Gold).
T
hiS plale ¡[lustrales good second arder suspicion
arousing criteria which Icad to observer lo suspecl t\Vo stages of mineral isation.
The firsl reaclion lO the rack is lo note Ihe s ulphide rich infill channel, and the aHendan! dark alteral¡an zonc. The hosl rack is tonalite, and Ihe alteration is biotite. Biotite alteration is conventionall y associaled w ith minute veins in porphyry copper systems, bul is actuatl y quite w id esp read in many other magma tic associaled fluid syslems (especially s karns) and can
assume major propor tions. The suspic ion arousing ci rcumstances relate lo lhe micro*lhin ve ins, which exlend al low angles ¡nlo Ihe host rock. These are composed of p y ri te s i li ca? (inf i ll), bul h a ve no alteration halo. Given the intensity of Ihe black biotile a lteration this is an obvious anoma ly.
38
ORE TEXTURES VOLUME 3 OVERPRINT1NG TEXTURES
C lose inspeclion of the infill channe l reveal s !wo d istinclly different malerials. Coarse gra ined pyrile crystals form one associalio n with hinls of black triangu la r textures (biolite?) occurr ing around Ihe centre lef! regíon. A second association conta ins grey wh ile maleria l (silica) wilh fi ner elongale s trin gy pyrite. A small vein cross clltting Ihe biotile alteration appears lo link lO Ihis (bottom righl). The re lationsh ip between Ihe t\'Vo infi lling slages is difficult lo discern. Intuiti vely, the aulhor suspects Ihe biotite relalcd material lo be ea rly util ising Ihe ind irecl criterion concern ing temperature of deposition. Biotile a lteration/infi ll implies high temperature ( > 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 STI
hi< pl~t .. h • • b .... n in c1udw for '"'0 , ...SoM. firstl y il has m ~ n} .uspicion HO" ""g oH" p rinling cril .. ri~. ~nd s«ondly il will mah' Ih.. po;nl Ih,,1 il is un",b" lo Iry ~nd resoh-c proOl~nb in IIw 1 """'pri n ting \ein srs'''''''. \vI",,,· 1." ."<1 ",;Ih conflicts 01 mi"nal,hing a l l~ral "". o' pos.lbl" cmS..."Wng indica l;ol1', Ihe obser\" n.......... Ob;er\'ation al Ihe "ein mar~in s (naál ... 1.0""" o ...1""",h .. , ... may quiály ¡solal .. ¡ndi> id".l .t'g~"> and ",,'aloli.h ¡nfillf alt.. ralion f'dÍ~.
T
Tl\I." plal.. contains ''''0 sul phid .. ,-tins ..-hieh ron:. i"
,it,-
' p hal .. (d •• k) .rsenopy. it .. (sil, ... ) .nd mino. py"'" (f"I .. ),,,110"'). T h" sph.I".il.. h~. OC(".~;"n~1 s ih try n.s h ... du .. lo d .-a ' .~flK'.ne~. T ....·se . ppt •• lo b<. inlill mi"" •• r.. a nd al firsl ,i Shl Ih" .l"> this _mingl), n.,hor.. 1 ~rr.. ngem .. ,,' 01 I>igh temp.· •.""." Ms~n"py.ile o'·" 'r.ioled by ,ph~l e .ile. Fi,"lIr Ih".e i. a dish¡rbing I~d 01 ~~nOp)· .il" on 111 .. sid" walls 01 bolh \ dns lo". .. ds Ihe '01' 01 lllt- pl"'e ... nd >ccon 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'<:imc',s Ihis is indeed Ihe c.... , The .. rs.e"op )·.il" is lale •. • "d a fu"u'" is ulili sin g Ihe . p h .. le ri, .. ,ein ",alls lo cha"",,1 in Ihe a.senopy.i, ... , The su.p;':;"" u cusing eril"rio .ono giving l!>e co.....,' s ,snal! The siluoli"" ""•• ding al'..... I''''' p.oring. t..wmes ~,'"n more suspid"" .rou.ing. n..- o.ig,n.1 roe!. is ,,,,,,,,lit.., .. nd ,,,," d.r"". ruck "nib p.om;nen, on 1..... bollom ""nl.e .. nd bollom cenl .... ighl lorlt'S mos' d ..... l)" ~n>St"flII ..... o .ig' ... 1 roc~ I",'urr.
l h.. sph .. I.·.ite/a.senopy rtte ,'<.'ins clN rI)" p'e .... nl a p.oblem if Ihe)" .~g.\fded '" """ st~¡;e, At "'oSI poinh lhe y se..,,,, lo .el.>1e lO Ihe )"" lIolI'ioh oll"."tion, bul lo,,"~,d > 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<'1I1S as Ihe d ~.~ S........ mi ...... al n>p...-...nls chlori,iscd fcldspalS aM ehlorilised homblcnde!
''''"n
a.e
1""'"
s..,'..
In s imp le la nguage Ih e.e ..." > " ~ 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 missÍ<>n imp<...,.ible . nd mO' e lo Icss ronlusins si'nalions in , .... immed,.I .. "acinil)" TH IS SITUATIO N IS CO~'MON . AII of this faíl. lo arlS"·... , ..... vital question '" ' Whictl slaS'" ;s sold ¡,..aring!·
o
1cm
[
[
ORE TEXTURES VOLUME 3 OVERPRINTINC TEXTU RES .J I
PLATE 19
SUSI'ICION AROUSING - INCONSISTENT AllUlA'110N - COl\lI'tEX OVERI'RINT'lNG. I'ARAI I.J,I. Rf.ACTIVATIONSTRUCfURAL SUI·I:RI~II'OSlnON· VEIN5. $o'fMons tin min~. M"unt .\ towbr,l )' di s lrkr. In i"<'b.>nl<. norlh Queensl~nd. A"slr~Ii~.
T
hiS p l.oIe h.,. be.."" ",k",t.d lo .. ,hi bi! a .... picion ,'r"Qusi"S ¡"«)1lSi,len! a I l<~rati(m conf;g"r~ l i'm ,
Tlle ",.11 'oc" (bol1om le/t) is gr"oi"·' comp"",-"I 0 1 /eldsp M (pinl: . ')T~ng .. ). q03rt>; (gr .. y' and miu (bmwn), 11", nlOSI ob"ious ¡... tu,e ¡s a da r ~ "do (t"VI ",hieh COIuains "er)' deM inf~1 te~I U~ """"'" ........1'·" ,,",m,,.,h..,. as darl blarl.b,o",,, equant c ry~tal s of c.ssil•..,.,t .. " ·'tl! ..·.. n ""' ....·Ioped tri."sul .. tUluR'S 01 infilling pot.,."ium fuldsp.r (pink).OO "1 ....'17, (gn.'Y)' """' ,llt"r.tion ""ir tI",1 links lo lhe ¡nfiU is d~,lr l)' thibly ~UMI7. (1"1' lefl). A p,ubl"m imm,'
'dising 1m, su.pki .... Ih.t I""Q .I~g"" are in\"QI,·NI . A '"<'ry ureful ~u",in.li )n of • serin uf minute micro"eíos p.,.lIdinS Iht main infoll Slmelu", (bot _n mid leh eom~ .... f , ilk. , leld . pa, and ,.'" e<>ss iler ile). re,·.,.l s IhU the y ." .. aLly cut Ihe anomak>us g"'y .h... ,olioo ~.m,... n... grey allerati(lll ~One ( mid lo bOllon. ,ighl) is in fae l • p"" io ... • 1t~"Tdti"" .,-hieh h ~ s ......... OH: rpnnlNl by lhe f~ldSf>"r s t. S.... It is composro of silica (g .....y ) and se,icit ... (darl g'ey·b,o"",,· í,o,, stdin~od •. "J"he infill IMi,ing to this .llt,·ratiun is nut "isiblc "n thi. plate, b,,1 is '.mfim",d as siliea eI ...·where "" the .""!",,ty. lh~ central ¡niill ZOlle 01 cdssiterile·lddsp-lr q ua'lI. actu:llly has t,..o diff"",nt ",.11 ThesE" "r~ th<.· granit .... s d ,.,;.::ri!>ed abo'·e . ana the p''''''¡ou''¡y alt ... red silie. · ... 'kitc ,ock (bollom lell). T"he leldspar aller.li"" ",ilhin ti"" lal1",. i5 ""Iec"wly pielil1g oul lhe ..... icil~ "" tht fril1gt""S.
""h.
A quart¿ il1fill ,,, in (bollon, 1.,(1 ) ",ilhoul an)" . s sociat.od ahtration rn.~ tep'''''''nt a thi td s tage (unlirntod).
o !
1cm !
ORE TEXTU RES VOLUME 3 OVE RPRIN TING TEXTURES 43
PLATE 20
SUSP IClON AKOUSING - INCONSISTENT ALTERA TlON, CO "II'LEX OVERI'RI r-.'TING, ALTERArlO,\ ¡ OF AL TERATION. srRUCT URAL
SUP ERI MPQSITlON-V EINS. "Ibite " I t~ r~t; "n. Malk-e Gap
C~ k.
Clon
norlh Q",'<,,,sl,,nd. Auslralia. Spe<:i l1\~11 donaled by Dr. I'.J. \V¡m,,,,s,
h¡S ,,,,k h.I ' b~cl1 ind uded as it ~xhibits Ih"",, o\'t'rp,inting st"g.~ "nd gi, ·c.,; " \'c,)' good '~l"l l "~I,, example 01 ti,,· "er)' (Oll1mon siluat io" wn~re th~r" ;> .In a~ymme!ry ",hiel> 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 <:>
The mosl obdous sl,'ge is Ihe e.Hhest d",k ""in (OOlhm. Idt), whid, i, , trikingly owrp,int,"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 (<<'" Ir,,-Iop) ",h~'e ti", pink actuaJly comes J ir<'CII)' into mnta,! ",ith h05t . ock ",ith no int,'"',,,nin6 ",hite W"~ The pink materia l is in fad oeCl".ing as " "'p",.,le st.'ge "nd oceurs;os a" a lte,.'lio" of Ii'o> ",hite albite, anJ prob.,bly the alle,,"<1 ime,,1 Sepa ra li"g out Ih,· inli Jl z<:>ne" to too ",ilh Ihe 10"0 fcldsp.,,,, is very diflieu lt. ." ,d th is ;s "s"ally Ihe ca~ in fdd~palhic sySkms. Thc white albite inl ill is ¡ust "isible (boll orn right) \\'h~,c il is di,tingni shed by a stigh tly co.""'_g,.,in s;ze. and a cr~.",)'
o __________________ ~I
~
1cm ORE TEXTURES VOLUME 3 OVERPRINTING TEXTURES 45 __________________JI
PLATE21
SUSI'IClON A ~OUSI NG· INCONSISTENT Al URATlON. ALTERATION OF ALT EKATIOI\ . STRUCI'U RAL SU I'ERI1>II"051T10N-Vl:I NS. I'tgmont, Ic.;od·ónc p~ . Cloneu'f)' nogion, nonh ~~od. A'OSIT~li~_
5p«im.... don.• tOO by Dr. 1'.1. Williams.
To''''p,;,,';ng t "~tur"s. with good e ~a "'pl.s of h¡~
1,lole h. , bt...,n ..,I"" ,.. d lo ¡lIo ,t •• t," su bU ...
;nn"'S;Sh> 111 .1t"'Ati"n halos. and alt"ra'iOfl of a lter.llion . It ",jll b~ of s pecial ¡"leTu I lo In~"y ,,,.,,lers. as il is pdrt "f ,he stockwor~ >y.t<'''' ",hi eh "n(I,·,li,.,; Ihe I'egmon! Icad_z;", p""'f>'.'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$. The aeh", 1 ,'cj" is im".,rSi,lent. a"d Ilwr~ ~rc b lolch~'S 01 darl bufl ",ateridl ~ssoda l ~'gion in ",id p l~tt·,
....
ORf TLXI UR[!, \'Ol.L \l EJ OVEIWI!INTING TlXTURf:S
T he leh hand side ,>~ h ibi l ~ Iwo ctcarl)' dilf.. 'enl ~ltcrJli<.>n 51),10$, one of ",hich t.end s \'~rli ,all )' is mosll)' pal~ y .. llo\\" ",ilh ",hi le fringu and leuur.lly .esembles Ih .. ah,>ratioo d esc.i bed . bo\'(>. It seems (ontrolll'd b)' minul" '· ... lk.1 mkroc • .ocks, and o'erp.inls . n '>Hl ier (gre)', grey·while) s ubho. izonla l all ... alion. Th i~ mal ... i.1 i5 K· fdd~p.or. a r>d wi th do.;e~" al,on il .ppt'''''' lo be •.. p lace dillicult 10 r~ I~I ~ Ih" obdolls d ..l infil! c h.nnd (centre-righl) lo .. ilher a lte.alioo, ond Ihe " ' hok question 01 fluid challrlelwa)'s a nd ingress i. not rO'SOI"able on Ihi s r,,(l. (lb, ,ollsl), mi"""racks. and ,arialion. in hosl .oc ~ g •• in ~i, .. /eh .. mis'r)' h. "" pl. )' ed a mOlor rol .. , wilh .Hualion prl'dominaling 0' er ¡n lill. This rocl has been euminl'd undcr lhe microsc0p" and lhe ea.l)' K.leld Sp
o
1cm
I
I
ORE TEXTU RES VOLUME 3 OVERPRINTI NG TEXTU RES 47
PLATE 22
SUSI'IClO,'\' A ROUSINC - Al T EKATlo,,\' 01' ALHRATlON, L A YER ROl. Tkk 11,11 80l d mi",-, C lo,,'u,.)' ,egioo. no r lh Ou<"-"bldnd, Australia.
cm.n
hlS roc~ !>.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<,,....:f 01 albi'e Ipale dno •...d pink) and sil i,. (gr..)"). n.., 1"'0 mdio< componCflb ,.""Y consid ...... bly in bolh forma, and quan!;t) , bul s .... m lo ha, .. aequir"d !h... ir ,onfigura',,,,, in len . .. duct il .. dd"'mation Th o,iginol nah .." 01 Ihe roek is conlt",tious. wilh opinions ',lOgl"8 lrom d" al'e,f.'d "'1".::-<'01.1111'" 01 ¡e l,k Ignl'
~nd
,i.
Th.· S¡ lu alion is nol maJe an,' ,' a si" . by Ih.' o""l'rinling alle •• tion (middll' to 1,,,..,· • ...gion), Thós 1'''-'''''''''''' mosl the original II'xtures and resulls in a m¡~tur~ of p~l(' g'('Y (quartr.) pal~ gr~('n.,,' h¡tt
4
ONI' IUTUIIES \'OLL\IE30\'L N!'MtJ\ITINC l'fXTLMES
(...:.'poli t.,) dMk g'N'" «"I<>rite?) to);~,her ",itl> red bro\\'n iron (aid.'~_ l' hr d.n ' e, lO ,,,,,; link !(>);.'th,·r ""d "-1'r.·...'nl lhe n, .. in eh.nn,·I ... a)'. controllins fluid ('nlry. A mi"ul" pal., sreen ,,~ck ... ithin , he e",nlral portion rould bt- an >nfill (h.on~l> Ebwwhe ... (JI'> IIw properl)', the grN"n -cape"t .. rich ~It.,r.lion can bt ,.,..., lak"'S out ,he ftltl ... ¡lInk roek on • mator ~)
'n,,, b,o"'''
iron o,id~ whkh 0<:(1l)"5 al man y p",n' < ...llh in th ... plal.> 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<>hiiS ós no! d"", lo "·ealhering.
11", 101' "f Ihe pl",~ ¡.. ,I «(JIers " (h.nge in roek Iyf"'. 'fhis "nit i. p rimaril)' ~""rlZ (\\'hite Sr.'Y) "nd chl"rile? (dark s"-,,,n .b lack) ",hkh s<",ms ,,, h.1\'e lit",,, by Ih" iron ",id., ~11.·c.t ion (brown)_ A ~n1~1I ,
"'f."" .-.I
o I
1cm I
ORE TEXTU RES VOLUME 3 OVERrRINTING TEXTURES 49
8
A C KNOWLEDGM ENTS
This Ihird "olum~ h~s laken more li",,, lo produce Ihan oolh 01 Ihe prcdt'C .... sors. Ot,,"ioo.ly the ""thors dé"S«!nl into m itd demensia h,1S r<'S" lkd in ,Io\\"e' I,mg't";';_ Ho"-"v", many people h,1\'e assistcd consid ce,'bly. The sponsors belo,,".re vital conuibu lors ",ho ma ke "v"rylhing poss ibt,.. "n d Simila' ;I( kno,,"ledgements are due to Ihe p ,oducti')ll k am _ D, Ga"in Clarkc c<>nt ributcd enormon.ly in rock col iL'Ction. ",Icetio n "n.1 prepar.,lion. Roge< Y,'Idh a m ,'ga ," prodoced tht, fi'¡'ny of my ,oll,'agues ha"., donat,-d . ",-'Cíal (photogeni,r¡ roc ks, ;lI1d Iha n k$ ;,,~ d"c to Dr R, Mycr'S, Dr I' ,J, Willíams ""d Dr G.I\' CI,ukt,
Sponsors: ECO N OMIC GEO LOG Y RESEARC HIRESO URCE
M IM EXI'LORATION r TY LTO
UN1T(ECRU¡ M " LEYSltON GOLD MINES A6ERFOY L E RESOURCES NE\\'CREST MINING ¡AUSTRALIA) I'TY LTO A6X
EXI' LOI~AN CI ONES
NORMANDY EXI'LORATION L TO ACACIA RESOURC ES NORTII FLl N O ER S EX I'LOR ATION AUSTRA LASIAN I N ST ITUTE O F MINING AN O N ORTII LTD
MET A LLU RC Y (NOR1"11 QUEENS LAN O 6RANCH)
I'ASMINCO EXPLORATION
ARIM CO
I~r
AU RORA COl.O I'TY LTD
FRE EI'ORT I NDO NESI A
I'LACE R EXPLORA TlON LT O
6AITtE MOUNT AIN (AUSTRA LI A) I NC.
I'LUTON I C M IN ING
61-1 r
RCC LT D
CYI'RU S COLO A USTRALI A COR I'.
ROSS J\-11N I NG NI.
D ELTA C OL O Nl
RTZt SO UTH AMERICA)
C REAT CE TRAL MINES
SONSO FGWALl A
HO.\IESTAKE A UST RALIA
WEST ERN M I N INC CO RrORATlON
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lf ',i, dOllblfll1 lifrslyle fOIlI;'",,.,, tI,;s ,"bj«1 ¡,,;JI fi lwJly ¡". adJrr;;Sl'l! 111 ,,,,,,,,,,,, 4 -
51)
OR E TF.XTU RI'S VOL U ~IE 3 OVERI'RI1\'TII_G n.xrURES
9 : REFERENCES Dong. c., MQTri:l()r"l, C.IV. and J~ircth. S. 1995. Qu~rU t.,~tures in .,pid....,......1 ,·.,ins. origin and impliNtion. F.ronomicG..()logy. V. 90. p. 1841-1856.
Taylor, Ite. 1m. Ore TeXlull."S Volume 1 lnfi ll. Economi<: Crology Cook Un¡'·...sily oí North Quc.m.sland. 2-4p. Taylor, R.G. 1994. Ore TeXlull."5 Volume IJ Aller3tion. Eronomic James Cook Uni"ers ilY nf NO.l" Q.>("(>1lsla nd. SSp.
R~~rch
("~Iogy
~and:
ct.ssiflcation.
Unit. Ceology o.,p;o rlml'11l. ¡.meo;
Res<>arch Unll, Crology Oep;ortment.
ORE TEXHJRES VOUJME 30VERl'RlNTlNG TF.Xl1JRES 51
