TERRO.AXNITE AT TIIE COOKB MINE 905

The Cana.d.ianM ine rala gist Vol. 31, pp. 905-916(1993)

FACTORSCONTROLLING THE OCCURRENCE OF FERRO.AXINITE WITHINARCHEAN GOLD.COPPER.RICH OUARTZ VEINS: COOKEMINE, CHIBOUGAMAU AREA. ABITIBI GREENSTONE BELT*

BENOFI DIJBE** ANNJAYANTA GUHA Sciencesde lnTerre. Centre d'Ende sur les Ressources Mindrales, Ilniversitd d.u Qu.4bec d Chicoutimi, Chicouttuni,Qudbec G7H 2Bl

ABSTRACT

Boron is commonly associatedwith gold mineralization,as suggestedby the widespreadoccurrence of tourmalinein gold- bearingquartz veins. Axinite, a calc-silicateofboron, is rarer than tourmalineand generallyis not observedin associationwith auriferous zones.This paper documentsoccurences of ferro-axinite associatedwith gold--copper-richquartz veins at the Cooke mine, near Chibougamau,in OreAbitibi greenstoneb€lt. At the Cooke mine, pinkish violet ferro-axinite commonly occursin auriferousquartz veins, in baren calcite-quartzextension-related veins, in hydrothermalbreccias, and within or near late brittle faults. Cross-cuttingrelationships and strain compatibility indicate that the late brittle faults and the gold-hosting structureswere formed in a relatively short period of time. The FeO contentof the axinite is high (87o),whereas MgO is low (270).Composition variations are limited and do not seemto conelale with distinct environmentsof formation, despitethe dif- ferent modesof occurrence.The formation of ferro-axinite is consideredto occur where carbonatizationis limited so that the availableCa combineswith B, Fe, and Si from the hydrothermalfluid to form ferro-axinite ratherthan tourmaline.This reac- tion occurredearly, as the ferro-axinite is commonly attachedto the walls of the veins, whereasthe sulfides surroundand part- ly replacethe ferro-axinite.The similarity in compositionof the feno-axinite associatedwith mineralizedveins and with late brittle faults suggeststhat bottr structureswere infiltrated by the boron-rich fluid. The formation of feno-axinite rather than tourmalineis also strongly promotedby a Ca- and Lon-rich environment.The study illustratesthe stronginfluence of the com- position of the host rock and of the hydrothermalfluid on the formation of feno-axinite.

Keywords:ferro-axinite, gol4 copper,boron, K-feldspar,Bourbeau sill, Cooke mine, Chibougamau,Abitibi GreenstoneBeIt Quebec.

Sotwtarns

Le bore est communementassoci6 aux mindralisationsaurifdres, comme le suggdrela pr6sencefr6quente de tourrnaline dansles veinesde quartzawifdre. L'axinite, un calco-silicatede bore, est plus rare que la tourmalineet n'est g6n6ralementpas associ6eaux zonesaurifbres. Nous documentonsla pr6sencede la ferro-axinite associ& b des veinesde quartz riches en or et en cuivre i la mine Cooke,prbs de Chibougamau,dans la ceinture de rochesvertes de fAbitibi. A la mine Cooke, l'axinite 1gseviolac6 est repanduedans les veinesde quartzaurif€re, dans des veinesd'extension st6riles compos6es de calcite-quartz, dans des brbcheshydrothermales, et dans des failles cassantestardives, ou d proximit6 de ces demibres.Les relations de recoupementet de compatibilit6 de la d6formation indiquent que les fatlles tardives cassanteset les structuresh6tes de la min6ralisationaurifbre se sont form6esdurant une p6rioderelativement courte. I.e contenuen FeO de I'axinite est 6lev6 (envi- ron 8Vo),alors que celui en MgO est fuble (4Vo). ks variationsen compositionde la ferro-axinite sont limit6es et ne sem- blent paspouvoir €tre associ6esd desmilieux de formation sp6cifiquesmalgr6 les diff6rentstypes de mise en place.La forma- tion de la ferro-axinite serait1i6e i un milieu oi la carbonatisationest faible; ainsi, 1eCa disponiblese combineavec le B, Fe, et Si provenantdu fluide pour former la ferro-axinite plut6t que la tourmaline. Cette rdaction se produit pr6cocement,6tant donn6que la ferro-axinite est gdndralementafrach& aux murs des veines, alors que les sulfuresentourent et remplacentpar- tiellementla ferro-axinite.La prdsencede ferro-axinite de compositionsimilaire associ6eaux veinesmin6ralis6es et aux failles cassantestardives indique que les deux structuresont 616infiltr6es par le fluide riche en bore. La formation de ferro-axinite plutdt que de tourmalingss1 (gals6ea1 fortement influenc6e par I'abondancede Ca et de fer disponiblesdans le miliel de for- mation. Cefie 6tude illusre I'influence de la compositionde la roche-h6teet du fluide hydrothermalsur la formation de la ferro-axinite.

Mots-cl6s: ferro-axinite, or, cuiwe, bore, feldspathpotassique, sill de Bourbeau,mine de Cooke, Chibougamau,ceinture de rochesvertes de I'Abitibi, Qu6bec.

* Contributionnum6ro 92-513G-19 du Ministbre de I'Energie et desRessources du Qu6bec. ** Presentaddress: Commission gdologique du Canada,Centre gdoscientifique de Qu6bec,2700, rue Einstein,C.P. 7500' Sainte-Foy,Qu6bec GlV 4C7.

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INTRoDUSIIoN within bodies of diabase.They contendedthat the gold-bearing axinite-quartz veins are producedby a The associationof boron with gold mineralization hydrothermalsolution related with an orogenicmove- is relatively common,as suggestedby the occurrence ment and not with a skam or igneousactivity. J6brak of tourmaline in gold-bearingquartz veins (Boyle et al. (1991) reportedthe presenceof Mg-rich axinite 1979,Roberts 1987). Axinite, a boron-bearingcalc- as a metamorphicphase in early carbonatized silicate, is rarer than tourmaline,and its occurrencein andesitesin the McWat0ersgold mine on the Cadillac associationwith auriferousmineralization is much less break,in Abitibi, Quebec.They notedthe early common.On the other hand, axinite is relatively replacementof axinite by tourmaline and suggested commonin manganeseand femrginousore deposits, that boron was first incorporatedin axinite and only contactmetamorphic and metasomaticore deposits, later precipitatedto form gold-associatedtourmaline. granitic pegmatitesand associatedhigh-temperature Axinite is a common mineral in Archean rocks of environments,regionally metamorphosedrocks, and the Chibougamau- Chapaismining district, where it veins in igneous and sedimentaryrocks (Simonen & is reportedfrom both mineralizedand barren areas Wiik 1952,Deer et al. 1,962,Mozgova1964, Carstens (Buchan1964, L976, Dub6 & Guha1989, Dub6 1990). 1965,Serdyuchenko & Makarov 197I, Ozaki 1970, In this study,we documentthe occurrenceof ferro- 1972, Lumpkin & Ribbe 1979, Pringle & Kawachi axinite associatedwith gold-copper-richveins and 1980,Sonnet & Verkaeren1989). Its associationwith determinewhy axinite is found at Chibougamaurather fracture fillings along or near fault zoneshas been than the more commontourmaline associated with the documentedby Hietanen& Erd (1978).Its relation- majority of Archeanmesothermal gold deposits. ship with gold mineralizationhas been reportedby Boyle (1979) and, in the Timmins area,where axinite RsctoNArSsrrn{c and clinozoisite occur chiefly in veins located on the fringe of quartz-ankeritegold-bearing veins, by Hurst The Chibougamau- Chapaismining district is (1935). Suzuki & Fujiwara (1971) have reportedon locatedabout 600 km north of Montreal, at the eastem gold mineralization in axiniteluartz veins emplaced end of the Chibougamau-MatagamiGreenstone Belt

-_--1.--J-"v x_- --- -_-_:-Xj:- :" ---:--J ,--i *,r' =- I* ***.*Wlr-* -1tr-r,1*-li,***'1 *-a orraFo c'eo'#Fl :a'* -*" I v

%doo ooi +i++ ++^e+'+r --++*+*t l*. .- * *'i:-J- *+ r + , , + +,F

'. -T--:+ '{ f + ,- + + +"+ N.\ ++{+++-J@- i\\\r\* q 5 ul5rn + *,---:fi a'1 + + t 4 + + I UBST'TBIIAL@LDDEFOSIT | 8€Yff""^*"r*t"*. N ffiffi*. lE r*nu"sedoffiffi ffi,yr* Iffi#n*rorr ? oPEMISCAT?PBvEl{r (c,A!) O mnErexgrntveors (cq,ag) ffiffi F;1ffis*ffi'.*ffi ffi**bfiffi MW * rorrgrnycorrunrrm iffidw fffi]&#ffi$fi#^"^r * rsn-vomn F;rffisHh, ffiffit#fr eqdwlqt)

Ftc. 1. Regionalgeological map of the Chibougamauarea (modified from cr'thaet aI. 1.990a).

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of the SuperiorProvince, where the Abitibi Sub- the Chibougamau{opper Fault (Fie. 2). province is truncatedby the Grenville Front (Fig. 1). The gold-coppermineralization is found in sulfide- The Chibougamau- Chapaisarea consists of a rich quartz, calcite, ferro-axinite or K-feldspar veins sequenceof volcanic (Roy Group) and volcano- from a few cm to few m wide. Theseveins are located sedimentaryrocks (OpemiscaGroup) of Archeanage. within two main brittle to brittle-ductile shearzones Detaileddescriptions are given by Allatd et al. (1985). or fractures oriented NW-SE to E-W and known as The Bourbeausill, which hoststhe gold mineraliza- the no. 7 and 9 veins. Overall, thesestructures are sub- tion at the Cooke mine, is at the top of the mafic- parallel to stratigraphic contacts and are interpreted ultramafic CummingsComplex of three sills emplaced to be syntectonic(Dub6 & Guha 1992).At depth in lavas and felsic volcanogenicsediments of the (> 400 m), however,the structuresare discordant.The BlondeauFormation. Regionally, the Bourbeausill auriferous structureshave lateral and vertical exten- is a layered iron-rich gabbro of tholeiitic affinity sionsof more than 500 m. The gold- copperveins are @uquettel976,Dub€ & Guha 1989).The sill differ- confined to the Bourbeau sill and are generally sub- entiatedinto units that comprise,upward from the parallel to the shearzones. The mineralized shear base,peridotite-pyroxenite, leucogabbro, quattz zoneswere producedby a subhorizontal,north-south- ferrogabbro,quartz ferrodiorite, and local upper ferro- directedshortening compatible with the Kenoran gabbro(Dub6 & Guha1989). orogeny(Dubd & Guha 1992).The shearsare offset Dimroth et al. (1986) and Daigneaultet al. (1990) by oblique northeast-trendingsinistral and local summarizedthe four successiveregional structural north-south dextral brittle faults. Thesefaults, as well eventsof importance:(1) synvolcanicstructures, as the regional Gwillim Lake and Chibougamau- (2) large east-westregional folds and reverseductile Copperfaults, are productsofthe samesubhorizontal, faults formed during the Kenoran orogeny, (3) north- nortl-south-directedshortening and regional strain- east-trendingsinistral faults of probableLate Archean regime.However, cross-cutting relationships and age, reactivatedduring the Early Proterozoic,and strain compatibility indicate that the Gwillim Lake (4) NNE-trendingGrenvillian faults (Fig. 1). fault formed slightly later than the gold-hostingshear zonesin an eventof progressivedeformation (Dub6 & GEor-ocvor rr:s CooKEMnrE Gnltria1992). The sulfide content of the mineralizedveins varies 'ftte The Cooke mine is a Au{u-Ag deposithosted in from tracesto 90 vol. Vo. sulfidesare mainly chal- Archean rocks of the Superior Province.The mine copyrite,with a lesserproportion of pyrhotite, producedmore than 2 million tonnesof ore at a grade arsenopyriteand pyrite. Most gains of gold are pre- of 5.04 glt Au,0.66VoCu and l0 g/t Ag. The mine is sent as inclusions or as fracture fillings within the located 5 km northeastof tle two major Opemisca sulfides. Thin veinlets of orangeto red K-feldspar copper-gold deposits(Springer and Perry mines: containing fine hematite dusting are commonly Fig.2), which havehad a combinedproduction of observedat the vein - wallrock contact,in the miner- more than 24 million tonnesof ore grading of 2.40Vo alized or barren deformedzones, and less commonly Cu and lessthan I g/t Au. in veinlets that cut weakly deformed gabbro. ooHematization" Stratigraphic and structural relations of the study of K-feldspar is a commonprocess areaare based on the work ofLavoie (L972),on maps (Rosenqvist1951, Boone 1969), and its relationship of the undergroundworkings, and on recent detailed with gold mineralizationhas beendiscussed by vari- mappingby Dub6 & Guha (1989) ard Dub6 (1990). ous investigators(Boyle 7979, Cameron& Hattori The local stratigraphic section comprisesvolcani- 198?. clastic felsic rocks of the BlondeauFormation intruded The hydrothermalalteration of wallrocks is rela- by theBourbeau sill (Fig. 2)."1\e Bourbeausill, which tively weak, and characterizedby chloritization ofthe hoststhe gold-copper mineralization,is, at the Cooke pyroxene,amphibole and plagioclaseadjacent to the mine, a 40O-m-thicklayered mafic intrusion contain- veins and sericitizationofthe plagioclasefarther away ing at leasttlree different units: 1) a basalpyroxenite, (Dub6 1990).These hydrothermal minerals replace the 2) a leucogabbro,and 3) an upperquartz ferrogabbro. regional metamorphicassemblages, indicating that In the Cooke mine area.the main faults are the mineralization postdatesthe peak of the greenschist- Gwillim Lake Fault (Dimroth et al. 1984, Dub6 & faciesregional metamorphism. Guha 1992),which is a regional NE-SW brittle- ductile oblique fault more than 100 km long with an OccunnsNcEsor FsRRo-AxINnE obtque sinistral displacementof severalkm, the NNE AT TTIE COOKE MINE Chibougamau- CopperFault, characterizedby a sinistral oblique-reversemovement (Dub6 & Guha Pinkish violet axinite was first reportedin the 1992), and the E-W KapunapotagenFault. The mineralizedsamples of tle Cooke mine by Buchan Gwillim Lake fault cuts the latter ones.The Cooke (1976). In fact, axinite is observedin different envi- mine is located betweenthe Gwillim Lake Fault and ronments.It is presentin sulfide-rich auriferousquartz

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Ftc. 2. Geologicalsetting of the Cookemine, modified from I-avoie (1,972)andBllmger et al. (1,984).

veins (Fig. 3A), and in calcite-quartz extensionveins Themineralized zones away from the mineralized shear-zones(Fig. 3B), in hydrothermalbreccia developedin unstrainedor Quartz and calcite, commonlywith ferro-axinite weakly deformedgabbroic rocts (Fig. 3C), and inside and K-feldspar, are the chief gangueminerals in the fault gouge or veinlets located near the faults. These auriferousveins (Figs. 3A-B). Typically, the veins are veinlets are either oriented subparallel or oblique to zoned, with the outer parts composedof quartz and the faults (Frg. 3D).Ferro-axinite identification is con- ferro-axinite and K-feldspar;the cenfralparts are com- firmed by powderX-ray diffractomefy. posed of quartz, calcite and sulfides, commonly with

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Frc. 3. A. Ferro-axinite-richmineralized vein (scalebar equals 16 cm). B. Extensionalferro-axinite veins (scalebar equals 25 cm), C. Example of hydrothermalferro-axinite-rich breccia. D. Ferro-arinite veinlets spatially associatedwith a late brittle fault (scalebar equals6 cm).

K-feldspar and ferro-axinite (Figs. 4A-B). In general, containsfractures fil1ed by calcite, or it is surrounded theseminerals are deformed.Quartz is polygonized by recrystallizedquartz. Locally, ferro-axinite occurs (Fig. 4C); the pyrite and arsenopyritehave been sub- as subroundedfragments in a matrix of chalcopyriteor mitted to cataclastic deformation. whereasthe pynhotite and is replacedby secondaryamphibole, chalcopyrite and pyrrhotite were affected by ductile calcite or quartz. Locally, K-feldspar attachedto the deformation,recrystallized and were probablyremobi- vein walls is surroundedby ferro-axinite or is partly lized in openingsand fractures in the other brittle replaced by ferro-axinite (Figs. 4A-B), thereby sulfides. suggestingthat at least some of the ferro-axinite Femo-axiniteforms crystals0.5 mm to I cm precipitatedlater than the K-feldpar during the same attachedto the walls of the veins. It is one of the frst mineralizingevent. hydrothermalminerals to have precipitated.Ferro- axinite commonly forms euhedralcrystals oriented Hydrothermal bre ccia and subperpendicularto the walls, suggestingthat it crys- barrenextension-related veins tallized as open-spacefillings in the absenceof any stress@ig. 4A). Ferro-axiniteconstitutes up to 307oof In hydrothermalbreccia and barren extension- someveins. Chalcopydteis common as inclusions or related veins, ferro-axinite is observedas 2 mm to is enclosedin ferro-axinite as fracture fillings. In 1 cm crystalsassociated with quartz,calcite and fraces places,the ferro-axinite is totally surroundedby chal- of tourmalineand amphibole.In general,ferro-axinite, copyrite.Elsewhere, it is partly replacedby chalco- quartz and feldspar are attachedto the walls of the plrite and pyrrhotite (Frg. 4D). As with the other vein veins, whereascalcite is in the interior. In the brecci4 minerals, the ferro-axitrite has been deformed the ferro-axinite is observedas fracture fillings and as (Frg. 5A). It shows undulatory extinction and locally replacementsof the gabbroichost-rocks. Preserved

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FIc. 4. Photomicrographsshowing A. typical assemblageat the vein - wallrock (W) contactcomposed of feldspar (K), ferro- axinite (A), chalcopyrite(Cp) and calcite (C); B. euheclralcrystals of ferro-axinite (A) subperpendicularto the walls of a chalcopyrite-rich(Cp) vein and suggestingopen-space fiIling; C. polygonizedquartz; D. ferro-axiniie (A) partly replaced by chalcopyrite(Cp). Scalebar equals0.35 cm exceptin C, whereit is 1 cm.

grains of primary titaniferous magnetitereplaced by axinite phenoclastwas observedto containtraces of leucoxeneand totally surroundedby feno-axinite sug- chalcopyrite,suggesting that ferro-axiniteand chal- gest that the ferro-axinite was formed by replacement copyrite are contemporaneousand that both minslalg of feldspar, pyroxene and am.phiboleof the gabbroic were strongly deformedby late faulting. Thus it is host-rocks(Fig. 5C). The ferro-axiniteis usually assumedthat the ferro-axinite and chalcopyriteare slightly deformedand cut by calcite veinlets.Locally, early relative to late faulting, althoughrepeated it is partly replacedby calcite,cb'lorite and epidote. movementsalong the fault also may be responsiblefor Tourmaline grains are locally observedand are partly deformationof minerals contemporaneouswith the replacedby ferro-axinite. fault. Textural relationshipsshow that ihe feno-axinite is Thefaultzones related to the samehydrothermal event leading to the precipitation of the sulfides and the gold mineraliza- Ferro-axinite is presentas a strongly deformed tion. Ferro-axinite does not presenttextural evidence mineral in the gougeof late brittle faults (Figs. 3D, that suggestsa late filling or replacementin the miner- 5D). It is presentwithin polyminerallic porphyroclasts alized zonesfollowing their re-openingassociated (0.05-0.2 mm) of feldspar,hornblende, quartz and with late movement along faults. The occurrenceof tourmaline,or as small fragmentsin a matrix of ferro-axinitein veinlets subparallelor discordantto euhedraltourmaline and actinolite. The ferro-axinite the brittle faults is puzzling. Was this fault-related showsundulose extinction and polygonization,and ferro-axinite producedby remobilization from previ- has fractures commonly filled by calcite. One ferro- ous gold-relatedferro-axinite?

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Ftc. 5. Photomicrographsshowing A. deformedferro-axinite (A) and associatedchalcopyrite (Cp); B. K-feldspar (K) partly replacedby ferro-axinite (A); C.'titaniferousmagnetite replaced by leucoxene(I-e) and totally surroundedby feno-axinite (A), and D. fefro-axinite (A) phenoclastwithin cataclasite.Scale bar equals0.35 cm.

CnurarcarCoN{posmoN oF FERRo-AXrNIE proportionswere calculatedon an anhydrousand boron-freebasis (Table 1). Concentrationsof water Forty-six spot analyseswere carriedout on seven and B2O3have not been deterrnined,and are allocated representativesamples from three differents occur- in stoichiometricproportions: OH = 2.0 and B = 2.0. rences,namely, extension-relatedbarren veins, miner- Total iron is expressedas Fe2*;the amountof Fe3+in alized veins and the late brittle faults (Table 1). the formula hasbeen calculated on the basisof (ryAl + Analyseswere obtainedusing a Material Analysis Ti + Fe3+)= 4.000. As suggestedby Pringle & Companyelectron microprobe equipped with a Kevex Kawachi (1980), the tendencyfor the analytical total 7000 energy-dispersionspectrometer standardized to approachl00Vo Qahle 1) supportsthe accuracyof againstnatural and syntheticminerals. Analytical con- this modifiedcalculation. ditions (acceleratingvoltage 20 kV, beam current 10 Results of the microprobe analysesclosely nA) and datareduction were controlled and processed approachboth the general formula for the axinite througha Digital PDPl103-L computerusing the group, A3Al2BSiaOl5,where A = Ca, Fe2+,Mg, Mn2* GeologicalSurvey of Canadasoftware EDDI. The rel- (Fleischer& Mandarino 1991),as well as the ideal ative accuracyof the analysesvaries from l-2Vo of the formula of axinite proposed by Lumpkin & amountpresent for major elementoto l07o for trace Ribbe ( 197 9) : (Mn,Fe2+,M g,Zn,Al.) (Car-,Mn,) elements.Results \ilere conected for background, .(Rlz_f"r*)r(oH2_,o,) rvlB2sis_d{lzlo3e,where w overlap and matrix effects (ZAF) (Love & Scott 1981, 4l, x 41, y << l, e << 1.The high FeO content, with Myklebustet al.1979). Fe greaterthan Mn, and the cationic proportion of Ca As done by Pringle & Kawachi (1980), cationic greaterthan 1.5, show that the mineral is ferro-axinite

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TABIJ T. AVERAGE COMPOSMON' OF FERRGAXINNBATINB C@re MINE

Ssryb PB.lilf.{68 PB-l1r{6 PB4|r{JB rts-16{:t lts-lm{:t Y8{/'285 tu249{6 &145{5 Mbcr lwcrof 942644410 @alytat Ocqratdcc (;hld Ydm BamYdm , Flortr so:(%) 4251 43Jt 43.6 c2sr 4931 43fi 42J4 4u3 slo.(%) 4LliI llor 001 og otxt ort 0I)4 txtlt 0t!4 (I(B T6, 0.19 Aul, tt,M 0a ns nM nz) t39 t6J't t6J9 Ato, l&4? H) 7:t6 &45 722 7:16 8.45 712 EJ9 tJ3 H) 6'jli' I'ltrO Lt2 29 2S 2.t2 234 up t:t2 l3) lrtr) 1.4,6 uso tst r3:l Itl t6t 133 r3r 1.48 2.t0 up 2.(n cd) n33 A.s mJ0 m33 8& Nlo mg m35 c8o D"qt rero fin uD un 0.m 000 0,m otxt iln r&p 0m KrO 0.(E 0116 0m (x!5 orF un 0Jl4 0.11 Kro o2l Toal 9r.49 9335 vta 9r.49 vt36 $a yLrT 9t:74 &ro! l.l9 &o ogl II2O. r.t9 tn ul Lt8 ljt r55 159 l5t qrcr r5t q9r' all 6n 6,a 6.10 621 6M 6.14 6.13 BPt sa7 ToET l(n.12

l.ord. (badrof 32 q OE, tut6 Elrd/ E!65 1056 EO67 U55 ubo st 79!t9 AI otbl n omt oJrrt otlt unr olnr oIIr, 0.(x)5 0tn4 It 0014 Al 3t{5 33!t6 3.m4 3J06 \J,!X 3.S4 tJ6 3m AI 4.0t3 Ittls 0.193 0.t99 0.ltlr 0.193 o.l99 0JE9 oza 0219 Rp' 0.167 4.0(n 'lln 4lm 4.mt 4.0m 4rm 4lxn 4.m 4& P IJTK IJIT ilx)8 ltxb 1.117 Lm t.t25 lIb{ RT IINE Irr! 0340 0369 ut2E 0340 0369 034 og,t5 oal Ivtr 0,3r Ms OA73 0371) 0501 o,{E 0370 05)l 0.415 05s MS OJEO C8 4J28 41(n 4.u5 qJA 4.1(x) 4.ltt 4.tu 4,ttt Cg 3M K 0012 0013 oolT 0l,12 0013 00r 0.010 ost K 0r!49 596!1 5969 5969 59E9 5"969 59'9 59'4' 6(m SAel oH. zqD z(m 2toJ 2Jm 2rq) urn 2M lln otr 2W E 2(m z|rn 2lm 2JXn 2JXn zlm atm zom B la95 Molgr% I'h 3.9l 638 sn 5gI 63E 5& 43{r 3JO & 7L46 mfit T7S 7L46 70.c| 72!X 7t.6 73,4r 22.s,9 R 2rst zns 2t2, 2tsI zn5 2t22 a,& z2ag 22.E9

* Ib a$omicpropotios havebeen calcotaie4 as Broposodby Pdngle& Kawac&l(1980), q an ohydrms ad boro:&es badc = = waE ud Broa-of offi e€ ostilnaredin stoicldom€fitcamqmb: oH 2.0, d B 2.0. +* Exaqle ;'xid!e composido, takq ftwD*r 4 al.(1962r. 'r. C8tctrlatEl;see tcrt

(Sanero& Gottardi1968). The chemicalcompositions principally undertakento examinethe CO2 and H2O of the ferro-axinite from the three distinct settings content of the fluid associatedwith the formation of within the depositshow little variation on the classifi- the feno-axinite. Most of the inclusionsare primary in cationdiagam proposedby Ozaki (1972)(Fig. 6). All nature,distributed mainly as single isolatedinclusions compositionsare locatedin an areaoverlapping the within grains of feno-axinite. The very small dimen- fields that characterizeaxinite from veins enclosedin sion of the inclusions(< 10 p,m) ma.kesa detailed igneous and sedimentaryrocks, from regional meta- study impossible.However, the few inclusions(11) morphic rocks, and from contact metamorphicand that could be studiedindicate that they are essentially metasomaticore deposits. aqueous,with no visible CO2.Homogenization tem- perafuresrange between 180 and 280'C. Only two Fl-uro-Ixcr-usroNDATA melting temperaturesof ice could be determined (-27.5"Cand -51'C), indicatingthe presenceof diva- A reconnaissancestudv of fluid inclusionswas lent cationssuch as Ca and Mg (Crawford 1981).

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Ca Axlnitefrom mineralizedzones I (15 analyses) Axinltetrom fault zones ( t o analyses) Axinitefrom extenslonbaren veins(ro analyses)

Mn 50 Fe F'.9ffi Axinitefrom manganesEand ferruglnousmanganese ore deposits ffi Axinitetrom pegmatites lfrEl] Axiniietrom contactmetamorphic and metasomatlc ore deposlts v--v Axinitefrom regionalmetamorphic rocks rffit Axlnltefrom velnsIn lgneousand sedimentary rocks |....!'..Ag

Frc. 6. Triangutar diagram showing axinite compositionsaccording to Ozaki (1972), andthe distribution of the ferro-axinite compositionsaccording to their distinct settingsat the Cookemine.

Since clathratescould not be observedowing to the HrO-rich fluid is associatedwith the formation of small dimensionof the inclusions,a more sophisticat- ferro-axinite. ed technique,solid probemass spectometry (SPMS) had to be used to ascertainthe level of CO2in ttre inclusions.The SPMS technique,which has been describedin detail in Guha et al. (L990b, 1991), allows us to identiff with a greaterdegree of accuracy TABI;82. COMPO$IION OFTRAPPED FLUID RELATED TO TEE the minor componentsof the fluid. Table 2 showsthat FORMATION OF FENRO.A)UNITE fluid inclusions related to the formation of the ferro- axinite associatedwith the mineralization are essen- SaEpls Bubs . CEI E2O @2 tially free of CO2. Although only a small number of PB-119-868 mlE t 9.0 S2.A 0.2 inclusionshas been sfidied. the microthermometric PE-041-858 6.2 84.8 1.0 PB-842-85 9.3 81.8 1.0 results and SPMS investigationsemphasize that a

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DtscussroNaro CoNcrusroNs mass-balancelithogeochemical study demonstrates that Al was relatively immobile in comparisonto tle Ferro-axinite at the Cooke mine formed from othermajor elements,and Ca was leachedand incor- hydrothermalfluids circulating in the shearzones. porated into the hydrothermal fluid to form ferro- Most likely, boron was derivedfrom a hydrothermal axinite@ub6 1990). These resulrs are compatible with fluid circulating tlrough shearzones and fractures, datapublished by Hurst (1935),Vallance (1966), and and leaching volcanic and sedimentaryrocks. The Mansergh & Watters (1969), who suggestedthat the mass-balancelithogeochemical study of the altered formation of ferro-axiniterather than tourmaline wallrock indicatesthat Ca was leached,whereas Fe resultsfrom a Ca-rich environment.Hietanen & Erd was added@ub6 1990).The Ca liberatedwould nor- (1978) suggestedthat the high iron contentof ferro- mally combine with CO, presentin the hydrothermal axinite is a reflection of a high iron contentof the host fluid to form carbonatesso typical of Archean rock in which the axinite-bearingveins occur (up to mesothermalgold deposits(Roberts 1987). The fluid- 10.307oFeO and3.62Vo FqO3 at the Cookemine). In inclusion data indicate the paucity of CO2 during the a generalperspective, this study illustrates the strong formation of the ferro-axinite.The extentof carbonati- influenceof the compositionof the host rock and of zation is relatively limited in the Cookemine, indicat- the hydrothermalfluid, and their resultantinteraction, ing that all the liberated Ca has not beenfixed by the on the formationof ferro-axinitein Archeansold COr. Thus, a significant amount of Ca was available deposits. to combine with the B presentin the hydrothermal fluid to form axinite. As previously mentioned, ACKNOWLEDGEIVIENTS ganguetourmaline is usually observedin gold-bearing veinsor wallrock;tourmaline, however, does not con- This paperis part of a Ph.D. thesisby the first tain significantCa (<2-3VoCaO), whereas Ca is one author,undertaken at the Universitddu Qu6beci of the principal constituentsof axinite (up to 207o Chicoutimi.The authorsgratefully acknowledgethe CaO).The B, Fe andSi presentin the fluid phasehave Ministdrede I'Energie et?es Resiourcesdu doeU"" combinedwith Ca, allowing the formation of ferro- for financial support,provided as a researchcontract, axinite.This reactionseems to be oneofthe first ones during the frst t"vo years of this study, for excellent to occur. That ferro-axinite is parageneticallyyounger logistic and scientific collaboration,and for permis- than the sulfides and gold is evident from its occur- sion to publish. We thank Minnova Inc. for their col- rence along the wall of the veins and its partial laboration,excellent supportduring field work and replacementby the surroundingsulfides. Similar tex- permissionto publish. We also expressour sincere tural relationshipshave been reportedby Mozgova appreciationto G. Pringleofthe GeologicalSurvey of (1964)and Serdyuchenko & Matiarov(1971). The tex- Canadafor writing a specialsoftware subr,gutine on tural relationshipssuggest that the ferro-axinite is in his EDDI progam to allow the electron-niicroprobe essencecontemporaneous with gold mineralization. analysisof axinite,and to M. Bonardifor his.help Structuralinterpretation of the mineralizedveins during the electron-microprobeanalyses. Rnancial and the late brittle faults suggeststhat the two struc- support in the form of a scholarshipaward from the tures were formed in a relatively short period of time NaturalSciences and Engineering Research Council of (Dub6 & Gnha 1992). As the briule faults are larer Canada(NSERC), ALCAN and the Reiearch than the auriferousmineralization" the ferro-axinite in Foundationof the Universit6 du Qu6becto B.D, as the fault zonesmay fs rnainly related to deformation well as additional tunding (NSERC grant 48374 and of the previously depositedferro-arinite contempora- FCAR Team Grant) to J. Guha, are also gratefully neousto the event of gold mineralization.It cannotbe acknowledged.The manuscriptbenefitted from con- precluded,however, that the fault-relatedfeno-axinite structivecriticism by Drs. TomasFeininger and J.L. is partly related to a secondgeneration of formation. Jambor. Our thanks are extendedto Claude Dallaire The presenceof ferro-axiniteof similar composition for drafting someof the figures.B.D. thankscol- associatedboth with tfie mineralizedveins and the late leaguesat the Mineral ResourcesDivision of the GSC fault-zonemay indicatethat both structureswere infil- for their hospitality. Thanks are due to two reviewers, trated by the boron-rich fluid; as the structuresare whosecomments helped improve the final manuscript. interpretedto have formed in a relatively short period of time, the sameconditions controlling the formation of ferro-axinitemay haveprevailed. RnrBnrncrs At the Sigmamine, Val d'Or, Quebec,Al and Ca, initially presentin the wallrock, were mobilized under Arrano,G.O., Cary, I.-L. & GoBErL,A. (1985):The the influence of the hydrothermalfluid (Robert & Archeansupracrustal rocks of the Chibougamauarea. 1z Brorrn 1986).These elements were incomoratedinto Evolutionof ArcheanSupracrustal Sequences (L.D. the fluid and were precipitatedas tourmalineand car- Ayres,P.C. Thurston, K.D. Card & W. Weber,eds.). bonateminerals in the veins. At the Cooke mine. a Geol. Assoc. Can., Spec. Pap. 28,55-63.

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B6reNcrn, J., Guua, J., CouroMss,A. & CantcNaN,J. - & - (1992): Relationshipbetween NE trending (1984):The 8-5 zone,Cooke mine, Chapais:a vol- regionalfaults and Archeanmesothermal goldEcopper canogenicmassive sulphide deposit in the Blondeau mineralization: Cooke mine, Abitibi greenstonebelt, Formation. /z Chibougamau - Stratigraphy and Quebec,Canada. Econ. Geol.87, 1525-1540. Mineralization (J. Guha & E.H. Chown, eds.).Can. Inst. Min. Metall.,Spec. Vol. 34,27 l-287. Dueuerre, G. (1976):North half of McKenzieand Roy lowtrshipsand northwestquarter of McCorkill township. BooNr, G.M. (1969):Origin of cloudedred feldspars:petro- Minist?re desRichesses Naturelles, Qudbec DPE357 . logic contrastsin a granitic porphyry intrusion.An. "/. Sci.261,633-668. FLETScHER,M. & MaNnenrNo,J.A. (199I): Glossaryof Mineral Species1991. The MineralogicalRecord Inc., BoyLE,R.W. (1979):The geochemistryof gold and its Tucson,Arizona. deposits.Geol. Surv. Can., Bull.7fl0. GUHA,J., CHowN,E.H., Ancner',tnArir,T,G., BARNES,S.-J., BucIrAN,R. (1964):Report on investigationsof samplessub- BnrssoN,H., DAIGNEAULT,R., DIoN,C., DuB6,B., mitted by OpemiskaCopper Mines Ltd. Internalreport MUELLER,W. & PrLorE,P. (1990a):Metallogeny in rela- for thecompany (unpubl.). tion to magmaticand structuralevolution of al Archean greenstonebelt: Chibougamaumining district. Iri Gold - (1976):Mineralogical examination of gold-bearing and Base-Metal Mineralization in the Abitibi samplesfrom Cooke mine, Opemiska.Falconbridge Subprovince,Canada, with Emphasison the Quebec Nickel Mines Ltde, Metallurgical Inb. Rep. Ministdre de Segment(compiled by S.E. Ho, F. Robert& D.I. I'Energieet desRessources du Qudbec,G.M. 36317. Groves). Department of Geology and University Extension,University of WestetnAustralia, Publ. 24, CarvnnoN,E.M. & Harroru, K. (1987):Archean gold miner- 121-166. alization and oxidized hydrothermal fliids. Econ. Geol. 82,1.1,77-tt9l. -_ Lu, HueNc-Zralc, DUBE,B., RoBERr,F. & GecNoN, M. (1991):Fluid characteristicsof vein andaltered wall- CARsrENs,H. (1965): Contributionsto the mineralogyof rock in Archeanmesothermal gold deposits.Econ. Geol. Norway. 32. Axinite in the NorwegianCaledonides. 86, tijT-684. NorskGeol. Tidsskr. 45.397415. & GAGNoN,M. (1990b):Gas compositions of CRAwFoRD,M.L. (1981): Phaseequilibria in aquousfluid fluid inclusions using solid probe mass spectometryaad inclusions./z Fluid Inclusions:Applications to Petrology its application to study of mineralizing processes. (L.S. Hollister & M.L. CranCord,eds.). Mineral. Assoc. Geochim.Cosmochim. Acta 54, 553-558. Can, Short-Course Handbook 6, 75-100. HmreNeN,A. & ERD,R.C. (1978):Ferroaxinites from the frorn DercNseuLr,R., Sr-JulrcN,P. & Ar-leno, G.O. (1990): FeatherRiver area, northern California and the McGrath and RussianMission quadrangles,Alaska. J. Tectonic evolution of the northeastportion of the Res.U.,S. GeoI. Surv.6,603-610. ArcheanAbitibi GreenstoneBelt, Chibougamauarea, Can.J. EanhSci.n,nru-n36. Quebec. Hunsr, M.E. (1935):Vein formationat Porcupine,Ontario. Econ.Geol. 30, 103-127. DsBn,W.A., Howm, R.A. & ZussrrleN,J. (1.962):Rock- Fonning Minerals. l. Ortho- and Ring Silicates. Long- JEnner, M., MTNEAU,R., Benooux, M. & Gouler, N. man, Greenand Co., Lonoon. (1991):Boron cycle in the Abitibi greenstonebelt, and compositionalvariations in tourmalineassociated with DrMRorH,E., ARCHAMBAnLT,G., GouLET,N., Guu, J. & gold deposits.1n GreenstoneGold and CrustalEvolution. Murlr-rn, W. (1984):A mechanicalanalysis of the late hoc. Nuna Conf. (Val d'Or, Qu6bec)@. Robert,P.A. ArcheanGwillim Lake shearbelt, Chibougamauarea, Sheahan& S.B. Green,eds.). Geol. Assoc. Can., Mineral Quebec.Can. J. Eanh Sci.21, 963-968. DepositsDiv., (abstr.).

- Muer-Lrn,W., DArcNlsAr,'r-r,R., BrussoN,H., PorrRAs, LAvoIE,J. S. (1972):Geology of Opemiskamines. Internal A. & RocIELEAU,M. (1986):Diapirism during regional report, FalconbridgeCopper Limited, OpemiskaDivision compression:the structural pattern in the Chibougamau (unpubl.). region of the Archean Abitibi belt, Qu6bec.Geol. Rundschau75,715-736. LovB, G. & Scorr, V.D. (1981):Updating correclion proce- duresin quantitativeelectron-probe microanalysis. DwE, B. (1990): Mdtallogdnie aurif?re du filon-couche de Scanning4,l11-130. Bourbeau, rdgion de Chibougamau.Thbse de doctorat, Univenitd du Qu6becI Chicoutimi, Chicoutimi, Qu6bec. Lt,n,tnrn,G.R. & RBBE,P.H. (1979):Chemistry and physi- cal propertiesof axinites.Arz. Mineral. fu , 635-fu5. - & Guue,J. (1989):Etude m6tallog6nique (auriBre) du filon-couchede Bourbeau,r6gion de Chibougamau:syn- MANSERcH,G.D. & Werrrns, W.A. (1969):A note on axi- thbsefinale. Ministdre de I'Energie et des Ressourcesdu nite from Aviemore, Waitaki Valley. N,Z. J. Geol. Qu€becNfrlI87rt03. Geophys.13,725-727 .

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MozcovA, N.N. (1964): Axinite and datolite from polymetal SaNnno,E. & Gotrranol G. (1968):Nomenclature and crys- skarndeposits in theFar East..lzt. Geol. Rev.6, 682-689. ta"lchemistry of axinites.Am Mineral.53,1407-l4ll.

MYKLEBUST,R.L., Fronr, C,E. & Hnnnrcn, K.F.J. (1979): SERDvUcHENKo,D.P. & MArARov, V.N. (1971):New data FRAME C: a compactprocedure for quantitativeenergy- on magnesium-ironaxinite from Pechengaand on the dispersiVeelectron probe X-ray analysis.Nat Bur, chemicalcomposition in general.Dokl, Acad. Sci. USS& Stanlards, Tech.Note L106, Earth Sci.Sec. lW, 128-130.

OZAK, M. (1970): The chemicalvariation of axinite in refer- SrvronrN,A. & Wrrr, H.B. (1952):The axinitesfrom enceto their modesof occurrence,J. Jap. Assoc.Mineral. Jokioinenand Petsamo.Bull, Soc. G6oI.Finlande 157" 1,- Petrol.Econ. Geol. 64, 157-172. 6.

- (1972): Chemicalcomposition and occurrenceof axi- SoNNEr,P.M. & VpnrapneN,J. (1989): Scheelite-, nite.Kwnannto J. Sci.,Geol.9.7-34. malayaite-,and axinite-bearingskams from El Hammam, centralMorocco, Econ. Geol. A,575-590. PRtr,rcr"E,I.J. & Kewacsr, Y. (1980): Axinite mineral group in low-graderegionally metamorphosedrocks in southem SuzuKi, M. & FUJIwARA,T. (1971): Gold-bearing New Zealand.Am. Mineral, 65. 1119-1129. axinite-quartz veins in the diabasezone along the west- ern margin of the Hidaka belt, Hokkaido. J. Jap. Assoc. RoBERr,F. & BRowN,A.C. (1986):Archean gold-bearing Mineral., Petrol., Econ. Geol. 65, 3948. quartz veins at the Sigra mine, Abitibi greenstonebelt, Quebec.tr. Vein paragenesisand hydrothermalalteration. Ver-r-eNce,T.G. (1966): A contactmetamorphic axinite para- Econ.GeoI. 81, 593-616. genesisat london Bridge, near Queanbeyan,N.S.W. R. Soc.New South Wales J. Proc.99.57-67. Rossnrs,R.G. (1987):Ore depositsmodels. 11. Archean lodegold deposits.Geosci. Can. 14,37-52.

RosnNevrsr,I.T. (1951): lnvestigationsin the crystal chem- istry of silicates. III. The relation haematite-microcline, Received May 25, 1992, revised manuscript accepted NorskGeol. Tid.sskr, 29.65-76. October 31. 1992.

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