Canadian Mineralogist Yol.22, pp. 93-109(1984)

GEOLOGYAND PETROGENESISOF THE KANICHEELAYERED COMPLEX. ONTARIO RICHARD S. JAMES Department of Geology, Laurentian University, Sudbury, Ofiarto BE 2C6 DONALD HAWKE GettyMines Limited, 700 WestPender St/eet,Vancouver, British ColumbiaV6C IGB

ABSTRACT tine, et caxbonate.Le complexeintrusif comprendcinq ryclesde cumulats.Dans les quatre cyclesinfdrieurs, la chro- The Kanicheelayered intrusive complex is the largestof mite, I' et le clinopyroxene constituent des roches several -ultramafic bodies in and mafic i cumulats qui s'6chelonnentde la d la clinopyrox6- metavolcanicrocks in the northern portion of the Tunagami nite. Dans le cinquibmecycle, une suite analoguede roches greenstonebelt, Ontario. An ultramafic apophysis along ultramafiques est r@ouvertede gabbrosd olivine et de gab- the northern margin of the intrusion contains a mineralized bros quartzifbres dans lesquels le plagioclase, le clinopy- zone of disseminatedand vein pynhotite, chalcopyrite and roxEneet une phased'oxyde de Fe-Ti sont les min6raux ; the host olivine has been altered to dominants. La hornblende ign6€est un accessoirecommun various serpentine-talc-carbonate assemblages,The in- desroches ultramafiques de tous les cycles;elle forme, dans trusive body consists of five cycles of cumulate rocks. In le premier cycle, une phase cumulative dans les clinopy- the lower four cycles, cumulus , olivine and rox6nites. Les sulfures se prdsentent en gtains interstitiels clinopyroxene form rocks ranging from dunite to dissdmin6sdans les roches ultramafiques des cinq cycles, clinopyroxenite.ln cycle5 a similar suite of ultrama.ficrocks mais sont particuterement abondants dans les cumulats is overlain by olivine and in which d'olivine de la basedu complex (c'est-i-dire, la zone min6- plagioclase, clinopyroxene and an Fe-Ti oxide phase are ralis6e,cycle l). Vu la similarit6 min€ralogiqueet chimi- the dominant .Igneous hornblende is a common que desroches ultramafiques des cinq cycles, chaquecycle accessoryin the ultramafic rocks of all cycles;in cycle l, seserait form6 i partir d'un magma de m€mecomposition; it occursas a cumulusphase in the clinopyroxenites.The seulela dernibre pouss6ede magna est demeurdeen place sulfide minerals occur as disseminatedinterstitial grains in le temps n€cessairepour permettre le fractionnement du the ultramafic rocks of all five cycles, but are particularly liquide ainsi que la cristallisalion du i olivine et peut- abundantin the olivine cumulatesat the baseof the com- 6tre aussicelle du gabbro quartzifbre. L'ordre d'apparition plex (r'.e.,the zone, cycle 1). The similarity in mineralogy desphases cumulatives dans chaquecycle et le chimisme and chemistryof rle ultramafic rocks of the five cyclessug- du magmaparent (d6duit desproportions relativesdes types geststhat each one formed from magma of similar com- de roche du cycle 5) montrent que chacun des cyclesa cris- position; only the final pulse of magma remained in place tallis6 d'un maerna basaltique riche en magndsiumappa- long enough to form fractionated liquids from which the rente aux tholdiites magnesiennesde Jolly (1980). olivine gabbro and possibly the quartz gabbro crystalliz- (fraduit par la Rddaction) ed. The order of appearanceof cumulatephases in each rycle and the of the parent magma (estimated Mots

Keywords: , mafic-ultramafic, layered,magmatic cycles, INTRoDUcTIoN olivine, clinopyroxene,plagroclase, Ni-Cu, platinum- group elements,Temagami, Ontario. The Kanichee layered intrusive complex is the largest of several sill-like mafic and ultramafic syn- volcanic intrusive bodies that occur in the northern Sovrrr{arns portion of the Temagami . Various aspects of the geology of this have been Le complexeintrusif plus stratifi6 de Kanicheeest le grand reported by Bennett (1978), Bennett & Innes (1971a, de plusieursmassifs mafiques-ultramafiques dans les roches b), Bennett & McNally (1970a, b), Simony (19il) and m6tavolcaniquesfelsiques et mafiques de la partie nord de (1942). l, Kanichee in- la ceinture de roches vertes de Temagami (Ontario). Une Moorhouse In Figure the apophyseultramafique en bordure nord du massif renferme trusive complex is shown to be located within mafic une zone mindralisde en pyrrhotine, chalcopyrite et pent- and felsic metavolcanic rocks in the central portion landite soit en filons, soit sousforme diss€min6e;cette p6ri- of Strathy Township, approximately 6.5 km north- dotite e ofivine est alt€r6een divers assemblagesde serpen- west of the townsite of Temagami, Ontario. It was 93 94 THE CANADIAN MINERALOGIST

lntrusionr t44ii

r '?^Jn

<(u J 1 ffi 3;iiin.r:i'#j Es c H:tg z'i '.7 MIDU-EPRECAMBRIAN Diobose 0) { ffi*pissins -#wW n^ I E+:liilillloowsondoForrmtion l\l ARoHEAN I r! -- I El f,Llil{i,f,lxl??i",nrusrons Formqlion e QJ-l-jh. lllllll{t'on *'# Q-i--.-3-3't"" fJreuc Mefovolconlcs FIc. 1. Regionalgeological plan of the Northeast Temagamiarea, after Bennett (1978). first reportedin the literatureby Knight (1920),who GENERAL GEOLOGICAL FEATURES recognizeda gossanzone 90 x 25 m at its northern extremity,that containsdisseminated and vein pyr- A plan view of the geology of the Kanicheein- rhotite, chalcopyrite and pentlandite mineralization. trusive complex is illustrated in Figure 2. The dimen- This zonehas beenintermittently exploredand mined sionsof the major and minor axesof this oval-shaped from as early as l9l0 (Bennett 1978).Most recent- body are approximatelty 1050 and 730 metres, ly, in the period 1972-1975,Ajax Minerals Ltd. respectively.A lenticularzone of quartz gabbro lies developedan open pit to excavateboth disseminated immediatelysouth of the main portion of the com- and vein ore to a depth of nearly 35 metres.Sandefur plex. It is not clearwhether it has a separateorigin (1943)described the geology of the intrusive com- from the olivine gabbro immediatelyto the north. plex in the immediate vicinity of this ore as well as As shown in Figure 2, and in more detail in Figure the mineralogy and paragenesisof the mineraliza- 4, the ore zone(cycle-l) rocks havea clearintrusive tion. Cabri & Laflamme (1974) documentedthe t'elationship to the metavolcanic country rocks. chemistry of the major ore minerals in a few Within this part of the complex, the contact has been typical vein-specimensfrom the intrusivebody, and observedin severalplaces. Typically, it is eithervery Naldrert et ol. (1979)and Naldrett (1981)reported sharp with no contact aureole,or it is the location the concentrationof Au and Pt-group metals in a of a talc-chlorite-carbonatezone of alteration that variety of ore-zonespecimens. separatesserpentinized peridotite from greenschisl- In this paper, we describe the geology and faciesmetavolcanic rocks. The contact with the coun- geochemistryof the layeredrocks that form the in- try ro.ck has not been observedelsewhere in the trusive body and host the Ni - Cu - precious-metal complex. mineralization at the northern extremity of the In Figure2, the layeredcomplex is shownto con- complex. sist of five magmaticcycles, each of which consists THE KANICHEE LAYERED COMPLEX 95 B-B'

OZ GABBRO

CYCLE.

t6@

o.-g-:P Fr 9_____!!p___89__i$r 4 Ftc. 2. Geologicalplan of theKanichee layered intrusive complex.Numerals l-5 referto ryclesof igneousrocks 3 illustratedin sectionsA-Al andB-Bl in Figure3. Cy- cle I is alsoreferred to asthe "Ore Zone", Shading for metavolcanicrocks as in Figurel. Two agesof mafic 2 CLINOPYROXENITE dyke-rocksare also iUustrated as linear outlines of solid o dotsand open, cobble-like symbols. Field relations by D. Hawke. FT Ftc. 3. Geologyof theigneous cycles 2-5 inclusiveas ex- hibitedby the stratigraphicsections A-Al andB-81. of one or more rock types.These range in composi- Soliddots indicate sample locations. tion from dunite and olivine peridotite, in which olivine is the only major cumulusphase, to peridotite and clinopyroxenite, which are olivine - clino- is shownin Figure 2. SectionA-Ar consistsof four pyroxenecumulates. Gabbro is only found in cycle separateigneous cycles, each consisting oflayers of 5. The contactbetween cycles I and 2lies within the one or more of dunite, olivine peridotite,peridotite, open pit of the ore zone, but it is not accessiblefor clinopyroxenite or olivine gabbro. Cycle 5 showsthe observationowing to flooding. The ore zone (cycle widest range of rock types and can be correlatedwith 1) and the lower portion of cycle2 are separatedfrom reasonableconfidence between the two stratigraphic the remainderof the complexby a fault zonewhose sections.Cycles 3 and 4 appearas truncated versions azimuthis 050'. The boundarybetween cycles 3 and of cycle 5 in that they contain only the more olivine- 4 and betweencycles 4 and 5 is approximately mark- rich cumulate portions of cycle 5; clinopyroxenite ed by narrow (10-20m wide) linear valleysoriented and olivine gabbro are absent.Only the uppermost parallel to stratigraphicboundaries between felsic portion of cycle2 is observed,i.e., clinopyroxenite. and mafic metavolcanicunits in the country rock ad- The baseof this rycle is probably representedby the jacent to the complex. The precisenature of the con- peridotite that overliescycle-l rocks (Ftg. 4). tact betweencycles is unknown owing to lack of ex- The strike direction of the boundariesbetween poslue. Within individual cycles, the rocks are cycleswithin the layeredseries is approximately055'. typically massiveand medium grained. Boundaries This value has been determinedby correlation of between recognizably distinct rock-types (1.e., equivalent membersin the two stratigraphic sections peridotite and clinopyroxenite) are gradational, and illustrated in Figure 3. From Figure 2, it is clear that only rarely is centimetre-scalelayering recognized. the strike direction is nearly parallel to the flow con- In Figure 3, the geologyis presentedfor the two tacts exhibitedby the host metavolcanicrocks. The stratigraphic sectionsA-At and B-Brwhose location sequenceof cumulus pihasesforming eachmagmatic 96 THE CANADIAN MINERALOGIST

6F| .oo; $i /r1' {ji*T ds {s$

ffxt-?...... a.aaaaaaaaaaa a a . . a . . . . . ' ' '-'i $

FT o to 20 lto rl Ftc. 4. Detailed geological plan of the ore zone (cycle l). Symbols for rock units in the layered complex are as in Figure 3; thosefor mafic dykesare as in Figure 2. The heavyblack line showsthe distribution of the Cu-rich veinswithin the ore zone. The disseminatedNi-Cu ore is largely confined to the olivine peridotite unit of cycle l. The stratigraphic column is drawn for the geologyalong the sectionline ABC. Field relations by D. Hawke.

cycleindicates that the intrusive complexis south- confined to a salient of ultramafic rock at the north- facing, as are the enclosingmetavolcanic flows @en- ern margin of the complex.A geologicalplan and nett 1978). These data suggestthat rocks of the stratigraphicsection of its geologyare presentedin layered seriesin this complex originally formed in Figure 4. Three N-S oriented samplingprofiles (AB, a horizontal attitude and probably at a very shallow BC and DE in Fig. 4) indicate that this zone is crustallevel. Severalpulses of magmaticintrusion, layered.Rather thin membersof clinopyroxeniteand eachof which may havehad a surface(volcanic) ex- peridotite overlie a thick unit of olivine peridotite pression,are requiredto explainthe cyclicnature of to form the cycle-l sequenceof magmatic cumulates. these-igneous rocks. Further, a magneticanomaly A poorly exposedwedge of olivine peridotite along slightly elliptical in a NE-SW direction and caused the southwesternmargin of the ore zonerepresents largely by the alteration of olivine and pyroxene(s) the lowermostportion of a secondcycle. to a serpentine-magnetiteassemblage, indicates that drilling carried out over a period of 20 yearsbegin- the ultramafic rocks of all five cyclesdo not have ning in the 1930sindicates that the baseof the ore unexposedextensions much beyond the presently zone plungesS35'E at approximately40o (Bennett observedoutcroppings. From the aboveinformation, 1978, Fig. 9). The magmatic layering was not we concludethat the complexis cigar-shaped,its long recognizedat that time; henceno estimateof its at- axis plunging to the southeastat a rather steepangle, titude was reported. causedby one or more periodsof deformation that $rrrhotite, chalcopyriteand pentlandite occur not similarly folded and deformed the enslosingvolcanic only as disseminated phases within the olivine rocks. peridotite but also in carbonate-quartzveins that oc- cur throughout cycle-l rocks and at the contactsof GEOLOGY oF THE ORE ZONE the complexwith the metavolcaniccountry-rock. The distribution of theseveins is shownin Figure 4. Com- The ore zone, identified as cycle I in Figure 2, is bined valuesof Cu and Ni in the veins run as high THE KANICHEE LAYERED COMPLEX

Frc. 5. Microphotographs (transmitted light) of cumulate ultramafic rocks from the Kanichee intrusive complex. 5A. Serpentinizedolivine grains enclosedby postcumulus , cycle 3, olivine peridotite. 58. Cumulus serpentinized olivine and fresh clinopyroxenein peridotite from cycle 4. 5C. Unaltered cumulus clinopyroxenefrom clinopyroxenite member of cycle 5. 5D. cumulus hornblende crystals partly replacedby (colorless)in clinopyt'oxenite mem- ber of cycle 1. Scalebar is 1.0 mm.. 98 THE CANADIAN MINERALOGIST

as 12 wt. 9o; precious-metalvalues for pt, pd and cumulatesfrom the peridotitesand pyroxenitesof Au averageclose to 2110, 9015 and 2ll7 ppb, respec- each magmatic cycle. In the latter rock-type, rively (Naldrett & cabri 1976). clinopyroxeneforms 90 modal 9o or more of the cumulus silicate phases. Chromite remains as a Prtno<;naprry cumulus mineral in the lowermost part of the peridotite member of each cycle, but rapidly disap- Oliv ine-c hr omite camul otes pears upward in the section, as indicated by the geochemicaldata presentedin a subsequentsection. Dunite (> 90 modal go olivine) or olivine perid- Small-scale(cm to mm size)phase layering has been otite (or both) form the basal member of each observedin thin sectionfrom two samplesof perid- magmatic cycle. Theserocks consist of equant to otite. In both, thin layersrich in clinopyroxeneare oval-shapedgrains of serpentinizedolivine 0.1-l mm sandwichedbetween mush thicker layers rich in in diameter,with variableamounts of intercumulus olivine. clinopyroxene, and their alteration prod- Olivine and clinopyroxenein theserock typesare ucts (Fig. 5A). Nowhereis the olivine fresh; typical- equant to tabular in shapeand 0.5 to 2.0 mm in ly, it is representedby a serpentinemesh and, less maximum dimensions.Whereas olivine is invariably commonly, by hourglass cells (Wicks et al. lg77)t replacedby serpentine,the clinopyroxeneis generally secondary is abundant within the mesh quite fresh or variably altered to tremolite (Fig. 5 rims. Grains of cumuluschromite rimmed by second- B,C). Representativecompositions of cumulus clino- ary magnetite are typically wholly enclosedwithin pyroxenefrom the peridotitesin cycles3 and 5, deriv- olivine. Freshpostcumulus clinopyroxene is present ed by electron-microprobeanalysis, are reportedin in theserocks from all five magmatic cycles. Table l. Normally, however,it was replacedby a mixture As in the olivine , brown pleochroic of serpentine,talc and tremolite (Fig. 5A). Brown hornblendeoccurs as a minor postcumulusphase in pleochroicigneous hornblende occurs in very small most samplesof the peridotite, occasionallybeing amountsas a postcumulusinterstitial phasein most so abundant as to poikilitically enclosesmall crystals samplesof dunite and peridotite of all five cycles. of olivine and clinopyroxene.It is more abundant It is replaced,in many casescompletely, by actinolite. in the upper portions of the peridotite and certainly more so in pyroxenitethan in olivine peridotite. In Olivine-clinopyroxene-chro mite cumulates cycle-l , the hornblende sporadically oc- curs as a cumulus phase exhibiting excellent basal The presenceof both olivine and clinopyroxene sections often partially replaced by actinolite @g. as cumulateminerals servesto distinguishthe olivine 5D). Resultsof the partial analysisof both amphi- bolesare presentedin Table l. The igneousamphi- 'I. bole is classifiedas titaniferous magnesiohornblende TABLE COI4POSITIONOF CLIIIOPYROXENEAIID AMPHIBOLE,XANICHEE COMPLEX (Leake 1978).The actinolite that replacesit contains 56 only 0.1 wt. 9o TiO2. Thesedata $uggestthat the slo2 s3.03 52.94 5L.72 43.22 58.04 near-opaquezones with 0,33 0.47 0.32 0.38 4,74 o.Lr tabular, intergrown ac- L.29 L.62 l.ls 10.92 0.08 tinolite consist of cryptocrystallinerutile. !tso 6.80 6.9S 6.29 6.70 U..41 6.94 r@ I8.t"5 17.74 L7.20 15.18 L4.46 21.15 Cd 2L.63 27.36 2t.r4 2I.81 lt.30 L1.73 10T-23- rollf tTdt 94.42 t6:05 5B:T5 Plogioclase cumulates

Nutber of I@ @ basls of Within the pyroxenitesthat immediatelyunderlie 6 o{yg@ 24 o, (cn) the gabbro layer of cycle 5, modal olivine is very L.994 L.992 2.009 2.052 5l 6.442 8.167 postcumulus(?) A1 0.006 0.008 A1 r.518 scarce; interstitial, leucocratic z:00- zn-d- za.r' zav E:00- E:167 minerals (plagioclase a quartz) occur in small AL 0.051 0.064 0.053 0.056 A1 o,4L2 0.014 t! 0.010 0.0L4 0.009 o.oLl. ,1i 0.533 0.013 amounts betweeninterlocking, equant clinopyroxene Fet" 0.213 0.2t9 0,204 0.2L6 '1f,r. 3.289 4,4X0 !E r..016 0.994 0.995 0.&3 0.427 0.543 crystals;igneous hornblende is nearly absent, and 0.677 0.669 0.685 0.702 5.00 5.00 magnetite-ulvdspinel solution now I;t6r T;046 I;65C 0.605 0.272 cumulus solid t.414 r,372 replaced by a titanite-leucoxene(rutile + horn- z:IT9 16Ar blende) assemblage makes its first appearance. l{c 35.5 35.7 36.4 39.2 Rr 53.3 49.4 s2.8 48.1 Titanium oxide, which occurs in the igneous am- P6 r-I.2 14.9 1"0.8 12.t_ phibole in the ultramafic rocks, is concentratedin 100_lg_ 82.7 82.0 a2.9 40.2 69.3 84.s the oxide mineral(s)of the gabbro member of this l€+Fe cycle. The gabbro consists of saussuritized Cotryositlons are basedon results of part.ia'l electron-nlcrcDrcbe analysig.by0. trlallkof the follming: l. clinopyrcxene,Dtl7S, cycle plagioclase,uralitized clinopyroxene,rare chlorite- 3i 2. cllnopyrcxene,DH-101, cycle 5i 3. cllnopyioxene,DH-S8,'cyite serpentinemixtures pseudomorphous after olivine, 5; 1. glilopyrcxele,DH-95, cycle 5; 5. tgneoui-hornutinae,oi-:fi-t, cycle li 6. tremltte, DH-34-2,cycle I. and leucoxene. and clinopyroxeneeach con- THE KANICME LAYERED COMPLEX 99 stituted 45-50 modal Vo of the primary rock. The the extensive development of talc and smaller transition from to these plagioclase-rich amounts of carbonate (probably )ap- rocks occursover a stratigraphicdistance of lessthan parently at the expenseof previously formed serpen- l5 metres. tine and tremolite. Net-textured mineralization re- The quartz gabbro unit that occurs at the top of mains clearly recognizablein theserocks. The in- the stratigraphicsection is poorly exposed,so our terstitial sulfide-oxide assemblageis coarsegrained; knowledgeof its mineralogyis limited. The absence commonly, feathery blades of serpentine,with a of altered olivine, the presenceof interstitial quartz strong preferred orientation, Erow outward ffom and the distinctly higher modal concentration of elongategrains of serpentinizedolivine into the opa- leucoxeneserve to distinguishthis rock type from que minerals of the net-texture assemblage(Fig. 6B, the olivine gabbro. A singlespecimen from the cen- c). tral portion of the quartz gabbro zone is rich in The most alteredrocks in the ore zone, and those leucoxene,pyrite, carbonate and chlorite; it may with the highestNi+Cu valuesfor "disseminated representthe shearedremnants of an oxide horizon ore", consistof the talc-carbonateassemblage that in this layered sill (cycle 5). has been fractured on a very fine scaleto produce chaotic networks of irregular zonesand veins con- Minerqlized olivine cumulotes of the ore zone sisting of chlorite (anomalous brown to near- isotropic interference colors), coarse-grained Unlike their equivalentshigher in the stratigraphic dolomitic(?) carbonateand, rarely, talc. The vein section, the mineralized rocks show extensivealtera- systemscommonly show a preferredorientation as tion. This is expressedin the pervasivedevelopment do associatedsulfide veins and stringers,which are of not only serpentineand tremolite but also talc, increasinelycommon in specimensof this type. These carbonateminerals and chlorite. Thesephases com- sulfide veins may be similar in mineralogyor very pletely replace, commonly as pseudomorphs,the much richer in chalcopyrite compared to the in- primary silicate minerals and also occur in vein terstitial sulfide assemblage,and are consideredto systemsthat permeatethese rocks on all scales.In be clear evidenceof remobilization of the opaque addition, pronounced recrystallization and apparent minerals.In suchrocks, the interstitial sulfidesare remobilization of original magmatic Fe-Ni-Cu now commonly intergrown with coarse-grainedcar- sulfidesinto microscopicto macroscopicvein systems bonate,which often forms the core areaof thesein- has occurred in theserocks. terstitial intergrowths. Also, olivine, previously DisseminatedNi-Cu-Fe sulfidesoccur within the transformed to a pseudomorph of serpen- olivine-rich cumulatesof all five cyclesin this layered tine-tremolite-talc-carbonate intergrowths, is replac- complex.Samples not from the ore zonehave metal ed by one or more of the Ni-Cu-Fe sulfides (Fig. valuesin the range 0.2-0.5 wt. 9o combinedNi + Cu. 6D). Those from the open-pit area of cycle I normally fall in the 0.5-1.0 wt. 7o range.Those samples from Cu-rich veins within the ore zone the ore zone that show the least talc-chlorite- carbonate alteration consist of small domains (2-4 In Figure 4, the distribution of the mineralized cm in diameter) of net texture (Naldrett 1973)in carbonate-quartz veins is shown to be largely wlrich loosely packed serpentinizedolivine grains are restrictedto olivine peridotite. They are up to I m poikilitically enclosed by a pyrrhotite-chalco- in width, clearlycut the olivine peridotite, and con- pyrite-pentlandite-magnetiteassemblage (Fig. 6A, tain pockets and lensesof massivechalcopyrite, pyr- B); theseoccur within much larger silicatedomains rhotite and pentlandite. In somecases, these show of serpentinizedolivine, postcumulusclinopyroxene crude bandsof sulfide each2-5 cm thick and parallel and brown igneoushornblende (variously altered to to the vein walls. Narrow alterationzones, enriched tremolite). The distribution of the sulfide minerals in tremolite, chlorite or talc, commonly border the that forms the net texture is considered to be vein assemblage.Unlike the disseminatedmineraliza- magmatic in origin, but it is questionablewhether tion in olivine peridotite, in which pyrrhotite is nor- the mineralogy of the sulfide-oxide assemblage mally the most abundant sulfide phase,chalcopyrite reflects the original bulk-chemistry of the immisci is by far the most abundantsulfide in the vein system. ble sulfide liquid from which the assemblageform- Factors suggesting that the vein mineralization ed (cl, Groves & Keays 1979).Nowhere have we representsremobilized magmatic sulfides previous- observedmassive sulfide zones,which suggeststo us ly residentin the olivine peridotite include (a) restric- that the quantity of sulfide liquid that formed at the tion of veins to olivine peridotite, and possiblyto magmatic stage was insufficient to segregateand a relict fracture-pattern in the peridotite, (b) clear form major concentrationsof sulfide minerals. similarity of major sulfide-oxide minerals in both An intermediate stage in the alteration of the environments, although abundancesdiffer, and (c) olivine peridotiteof the ore zoneis characterizedby associationof carbonate- ore mineralsin the vein 100 THE CANADIAN MINERALOGIST

Fte. 6. ' Microphotographsof sulfide-oxide-silicateassemblages from the olivine peridotite member,cycle I, Kanichee intrusive complex.A and B transmittedlight, C and D reflectedlight. Scalebars 1.0 mm. 6A,.biaqueinterstitial sulfide-oxide assemblageenclosing s6rpentinized olivine grains. 6B. Similar to A but including orienteA feathery serpentine intergrown witl r_ecrystallizedpostcumulus sulfide minerals. 6C. Interstitial pynhoiite-chalcopyrite- magnetite-pentlanditeassemblage endosing serpentinizedolivine as in A and B. 6D. O;ulus olivine gruittr no* tota-llv rePlacedby intergrown pyrrhotite, pentlandite and minor serpentine;also, postcumulus recrystalliied sulfide- oxide assemblageas in, C. THE KANICHEE LAYERED COMPLEX 101 systemand that same associationin the last rec- ognizedstage of alteration, in the disseminatedores within olivine peridotite.

PETROLOGY

In Figure 7, a summary picture of the stratigraphy of the intrusive complexis presented.The distribu- tion of the cumulus and postcumulusphases, to- gether with visual estimatesof the modal abundance of the former, allows for a clear distinction of the five magmaticcycles. Cycle 5 is the thickestunit; in addition to plagioclase,it containsall ofthe phases and rock typespresent in the underlyingunits. The olivine peridotite cumulatesin cycle I contain, on average,a higher propofiion of disseminatedNi- Cu sulfides than similar rock-types higher in the complex. The stratigraphy illustrated for cycles I - 4 and the ultramafic poftion of cycle 5 is almost entirely defined by the variation in the proportions of cumulusolivine and clinopyroxene.In Figure 8, the systematicvariation in wt.9o SiO2, CaO and (MgO + FeO) for specimensfrom cycles 2-5 o too reflectsthe variation in the proportion of thesetwo mafic minerals.Representative whole-rock compo- sitions of the major rock-typesare listed in Table 2. The chemistryof the dunitesand olivine perido- tites in eachcycle is very similar and is quite differ- ent from that of associatedperidotites. The clinopy- roxenitesin cycle 5 can be distinguishedfrom the Frc.7. Stratigraphyand modal variation in theKanichee more olivine-rich cumulatesusing thesesame oxides. intrusivecomplex. Solid shading and bars,cumulus However, the boundary with the peridotitesis per- phases;dashed bars, postcumulus phases. Proportions fectly gradational, in contra$tto the abrupt differ- of cumulusphases were determined by visualestimates; encesin chemistry(and modal mineralogy)between scalebar is for cumulusphases only. the olivine and olivine - clinopyroxenecumulates. Opaque, steel-greycumulus gtains of chromite oc- cur in small amounts throughout the ultramafic cumulatesin eachcycle, as indicated in Fieure 7. The Abrupt changesin CaO, (MgO + FeO), AlrO, distribution of Cr illustrated in Figure 8 indicatesthat and Cr and gradational changesin SiO2and TiOt chromite is most abundant in the olivine-rich in Figure 8 mark the transition from clinopyroxenite cumulatesof each cycle. The rapid decreasein Cr to olivine gabbro in cycle5. The changesin the first from the peridotitesto the pyroxenite and gabbro three oxides are causedby the sharply delimited flrst membersof cycle 5 is due to the early crystalliza- appearanceof cumulusplagioclase as a major phase tion of chromite and indicates that theselatter rock- and the corresponding . decrease in curnulus typescrystallized from a fractionatedsilicate liquid clinopyroxene. that had been strongly depletedin this element. Throughout the ultramafic membersof all five The distribution of Ni is very similar to the trends cycles, brown igneous hornblende occrus as a exhibited by MgO + FeOr, which suggeststhat postcumulusphase. Its distribution largely deter- cumulateolivine in the and peridotitesplayed mines the wt.9o TiO, valuesreported in Figure 8 for a major rold in controlling its distribution in the theserock types. In cycle 5, TiOt progressivelyin- ultramafic rocks of the, complex. Cu exhibits a creasesupward in the cycle. In the olivine and quartz similar pattern, but at certain horizons within the gabbros, it is found in leucoxene(after intergrowths pyroxene-rich cumulates of qycles4 and .5, it is ,of ilmenite and magnetite).The leucoxeneappears enrichedto a considerableextent above background in placeof the pleochroicamphibole in plagioclase- levels,probably o*ing to the samepostmagmatic rich cumulatesand is significantly more abundant hydrothermal processesthat formed the chalcopyrite- ip the quartz-bearinggabbros, as the chemicaldata rich carbonateveins in the ore zone. in Figure 8 indicate. The differencesin mineralogy t02 THE CANADIAN MINERALOGIST

, !p e , *-__!9__.__.19 rt_31!-J E_ls_u 1__,__3__-J 1__-___?__-___9 sio2 coo Fed+ Mso lloz AL2% Cr x lo5 Ni x lo3 Cur lo3

Ftc. 8. Element-variationdiagram for cycles2-5, Kanicheeintrusive complex.Solid dots are for data from A-Al sec- tion: x for B-Bl traverse.

and chemistrybetween these two typesof gabbro and 9o olivine. The presenceof postcumulusclinopyrox- the variation of theseproperties with stratigraphic ene is responsible for their skewed distribution height suggestthat the quartz gabbro unit is a dif- toward the Cpx apex of the figure. They do not lie ferentiateof the samemagma that formed the olivine on the Ol-Cpx compositionline, most probably ow- gabbro and ultramafic rocks of cycle 5. ing to serpentineand talc alteration of the primary olivine, during which a lossof MgO or relativegain Projections in the Ol-Cpx-Pl-Qz tetrohedron of SiO, (or both) shifts the compositionstoward the Qz apex of the projection. This is most noticeable The order in which the major cumulus minerals in samplesfrom cycle I (ore zone), wheretalc altera- appearin the rocks of this intrusivecomplex can be tion is particularly pronouncedand pervasive.By far understoodby examiningthe phaserelations in the the largestproportion of the peridotitesplotted in pseudoquaternarysystem Ol-Cpx-Pl-Qz as it has this figure consist of nearly equal to somewhat beendrawn by Irvine (1979,1970) and illustratedin greater proportions of normative clinopyroxene Figure 9. Of particular interestare the composition relativeto olivine. This is consistentwith the modal volunresfor olivine, plagioclase,ctnopyroxene and data on the cumulatephases summarized in Figure orthopyroxene,the position of the cotecticsurface 5. The clinopyroxenitesall lie on the quartz-richside a-d-c-f, which representsthe locus of liquids in of the Cpx-Opx tie-line. This may be accountedfor equilibrium with olivine and clinopyroxene,and par- by the presenceof small amounts of postcumulus ticularly the isobaric univariant curves such as a-d feldspar and secondary qvartz, bolh of which are that define a range of liquid compositions from common in the pyroxene-rich cumulateslocated im- which olivine, clinopyroxeneand plagioclasecan mediatelybeneath the olivine gabbro of cycle 5. crystallize.Also presentedin Figure 9 are the pseudo- Theseultramafic cumulateshave bulk composi- quaternaryphase-relations projected from the Pl, tions that lie very closeto the Ol-Cpx-Qz plane of Cpx and Ol apicesof the tetrahedron. On thesepro- the compositiontetrahedron; hence the plagioclase jections are plotted the cation-normativecomposi- projection quite accuratelyillustrates the proportions tions (Irvine & Baragar 1971)of a suite of rocks from of cumulus olivine and clinopyroxene.The olivine all five cycles in the layered intrusive complex. cumulates in each cycle of the complex have In the plagioclaseprojection, the olivine-rich crystallized from a silicate magma that plots within cumulates(dunite,s and olivine peridotites)are tiehtly the olivine volume of the tetrahedronin Figure 9. clusteredabout the olivine apex of the projection, The peridotites and pyroxenites crystallized from a indicating that the chemistryof thesecumulate rocks derivativeof this samemagma. It has precipitated is in agreement with petrographic data, which in- both olivine and clinopyroxene with falling dicate that they originaly consistedof 75-100 modal temperatureas its compositionmigrated acrossthe THE KANICHEE LAYERED COMPLEX 103

TABLE2. REPRESENTATIVEWHOLE-ROCK COMPOSITIONS(I), KANICHEE INTRUSIVE COMPLEX, ONTARIO

r(C-511 SpecirEn ut 74 Er 77 DH 50 W\ 47 D[r 93 DH 37 *IC-51 Dnite ot Pe!:i- Perido- Rnro:@!!ite oL Gabblo Qz Gabbno Calculated parent ^':le base of vJ! 5 qycLe 5 q'cb 5(?) ragna cdrposition ' c':/cle 4 cvcle 3 cvcLe 4 SecLi-on r A-Al alat Aler A-Ar A-AT B-81

sio2 (wt,%)44.LL 42.9\ 48.68 5I.49 49.67 48.45 48.60 48.51 0.48 0.98 tLw2 0.t 8 0.48 v.)z 0.67 10? r4.u 9.s0 ru2v3 1.68 3.28 4.56 15.84 7.46 FezOg(2) 1.90 1.90 z-u) 2.09 z. z5 J. UI 2.r8 2.60 Feo (2) L4.93 10.14 7.55 12.04 9.20 10.03 !,trio v. z) 0.27 u. zz 0.0L 0.L8 0.26 0.L7 0.2L Mgo 36.87 35.06 17 10 9.80 5.95 18.78 L5.27 0.96 L4.72 tq 6a )J.49 Lt.93 Lr-.93 Lt.89 Na2O 0.06 0.75 2.05 0.08 0.95 0.72 Kzo 0.01 0.0L 0.03 0.10 0.47 U.U) 0.19 0.16 0.04 E2vS 0.02 0.04 0.02 0.03 0.07 0.01 0.09 a U.If, 0.01 0.04 0.07 0.08 0.05 trotaL r00m $0m' 166:. m0:T0 $i]do- 166:10 100:10' 100;00" 3515 zJt I 2804 2L43 L03 1922 1337 Ni 1700 1840 820 s45 L85 46 814 692 L44 L39 93 74 55 62 6t zz5 269 26z 255 341 rv tL4 3s8 298 Z$ rt8 L46 78 77 81 L43 81 L01 (2) (1) The results of each analysis have been recalculated to l00 wt. % on a volatile-free,l.5 basjs. Fe20'3and FeOhave been recalculated from total us:ng the relationship Fe203= Ti02 + (after lrvine & Baragar l97l). t Secti0n is shownin Figure 2. * KC-51includes all rock types'in cycle S.gxcept the quartz gabbro, t,leightedaccording to their abundancein the stratigraphic section (Fjg. 3). KC-Srr includes the quartz gabbrohorizon.

cotecticsurfac e odcf toutar d the plagioclase-saturated it is probable that the quartz gabbro member is a c\rve a-d, differentiate of the same parent-magma that form- The gabbrosthat lie at the top of cycle5 are the ed the previously describedcomagmatic suite of only rocks in the complex believed to contain rocks in this cycle (5). cumulusplagioclase. Hence, only theserocks canbe expectedto have compositions near the isobaric CovrpostTloNoF THEPARENT Macua(s) univariant cuwe o-d-e it the variousprojections of Figure 9. In thesethree projections, liquids on the The five cyclesof magmatic cumulates that con- curve a-d will crystallizeolivine; those beyond d and stitute the exposedportion of the Kanicheeintrusive toward e will precipitate orthopyroxene (in addition complex have eachcrystallized from a separatepulse to plagioclaseand clinopyroxenein all cases).In each of magma. An accurateestimate of the composition projection, the olivine gabbrosplot adjacentto the of eachpulse is unknown, sinceclear examplesof projected cvrve a-d and, dependingupon the pro- chilled margins have not been observed.One way to jection, within the liquidus region for olivine, explain how eachcycle of cumulatesformed requires clinopyroxeneor plagioclasebut neverorthopyrox- the partial crystallization of silicate melt while the ene, In thesediagrams, one sampleis consistently magma was at rest at the site of intrusion. The richer in the calcium-bearingphases (plagioclase or cumulatesand residualfractionated liquid could then clinopyroxene)probably owing to epidote-carbonate have been separated(and not at the same stage for veinsin the specimen.All threegabbros are olivine- each pulse), the latter to form volcanic flows and normative, and their chemistry, interpreted in terms near-surfacehypabyssal intrusive bodies. Irvine & of theseprojections, supports our conclusionthat Smith (1967)used this conceptand a variant of it they and the underlying ultramafic rocks of cycle5 to explainthe formation of the cyclesof ultramafic form a comagmaticsuite. rocks in the Muskox complex from a magma of For the quartz gabbro unit that lies at the top of tholeiitic basaltcomposition. More recently,Camp- the stratigraphic sectionin Figure 7, we have a single bell (1977)argued that the macrorhythmicunits in composition, and it is qual"tznormative. In the three the Jimberlanacomplex most probably formed by projectionsof Figure 9, it plots in the orthopyrox- the same process.In the present case, using this enefield and in the generalvicinity of the projected mechanism,crystrallization of an olivine-rich mafic position of the liquidus curyed-e. To the extent that magma can, in generalterms, explain the formation conclusionsmay be drawn from a single data-point, of the cumulateuftramafic rocks in cyclesl-4, as 104 THE CANADIAN MINERALOGIST

OL

I t. . I otttiot* \g ta PLAGIOCLASE PI OL

Ftc. 9. Mafic and ultramafic rock compositionfrom the Kanicheeintrusive complex plotted on projectionsof the Ol- Cpx-Pl-Qz tetrahedron.9A. Phaserelations in the pseudoquaternarysystem Ol-Cpx-Pl-Qz asvisualized by Irvine (1970, 1979)for volcanic and hypabyssalconditions of crystallization.98. Composition of mafic and ultramafic rocks from cycles2-5 plotted on the plagioclaseprojection of Figure 9A, Ortho- and clinopyroxenecompositions are taken from lrvine's (l 970) data on the Muskox complex. Curve d-e is the extensionof a-d into the silica-saturated portion of the Ol-Cpx-Pl-Qz system.r olivine cumulates(dunites and olivine peridotites): I olivine + clinopyroxene cumulates (wghrtitq or peridotite); A clinopyroxene-rich cumulates (clinopyroxenites); x 2n4 @ clino- pyroxene + plagioclasecumulates with minor cumulusolivine (olivine gabbro) or'interstitial Qz (quartz gabbro), respectively.9C. Clinopyroxeneprojection, with somedata plotted as in B. Dashedcurves are for estimateof pos! r tion of phaseboundaries at 4.5 kbar (Green& Ringwood 1967).9D. Olivine projection of Figure 9A,.Phase boun- dariesat 4.5 kbar from Green & Ringwood (1967).

well aq the more completesequence represented in five cycles. Unlike cycles l-4, cycle 5 probably cycle5. representsa nearly completesequence of cumulates The fact that the uliramafic rocks that form rycles and relatedderivative . If so, it is the on- L-4 are igneouscumulates precludes the possibility ly cycle from which lhe composition of the initial that they crystallizedfiom an olivine-rich ultramafic magma for all cyclesmight be estimated. magma. This is further substantiatedby l) the The proportions of gabbro and ultramafic rock- similarity in mineralogy, textures and chemistry of types in cycle 5 indicate that the magma from which thesecumulates to those that form the lower por- it crystallized is intermediate betweenbasalt and an tion of cycle 5 and 2) the presenceof cumulate olivine-rich ultramafic composition. Clearly then, the chromite with olivine in the olivine peridotites of all Kanicheeintrusive complexis not a memberof the THE KANICHEE LAYERED COMPLEX 105

peridotitic classof intrusions of komatiitic affinity In Table 2, we list two estimatesof the magma that Naldretr (1981) and Ross & Travis (1981) composition from which cycle.5 rocks in the described.It may be a member of Naldrett,s class Kanicheecomplex crystallized. They werecalculated of layered intrusive complexes(type 2a) that are from compositions of representativerock-types thought to crystallize from picritic (tholeiitic) weightedaccording to their abundancein this cycle. magmas or it may represent the product of Both estimates have MgO values in the high- crystallization of a magma of komatiitic com- magnesium-basaltrange (12-?n \Nt.Vo MgO) and less position. The authorsmentioned did not include in than l0 wt.9o Al2O3.These features are consistent their classificationscheme a category for layered with the observationthat olivine and clinopyroxene complexesof the latter type. That such liquids do are the early cumulussilicate phases in eachof the form layered intrusions is suggestedby published cycles of the Kanichee complex. This feature in- material on the sills in the Cape Smith Fold Belt dicatesthat they are membersof Jolly's (1980) reportedby Francis& Hynes(1979). Certainly, some magnesian or magnesian tholeiite suite and of the layeredflows and sills in Munro Township, distinguishesthem from layered complexesof his Ontario have crystallized from similar magma- tholeiite suite, in which olivine and plagioclaseare compositions,given that volcanicrocks in this range the two earliestmagmatic phases.The absenceof are recognizedfrom that area.A mineralizedexam- olivine or pyroxenespinifex in the border phasesof ple of this type is the Mt. Sholl mafic-ultramafic the Kanichee complex and of rocks of known complexdescribed by Mathison & Marshall (1981). komatiitic affinity in the host volcanicsequence in- They suggestedthat the gabbro-peridotite suite, host dicatesthat the complexcrystallized from a magma to the disseminatedand massiveNi-Cu sulfidesat belongingto the magnesiantholeiite suite. The values the baseof this complex,crystallized from a magma (wt.9o basis) of the ratios Al2O3lTiO2 and of basaltic composition. CaO/AlrOt (- l0 and > 1.1,respectively) for the

wT. % TiOz

WT.% Mso Ftc. 10, Chemical composition of the Kanicheemafic and ultramafic rocks from cycles2-5 plotted on a wt.Vo TiO2versusMgO diagram. Solid curve outlines gab- bros, basaltsand a few pyroxenitic rocks oftholeiitic affinity. The area encom- passedby the dashedcurve encloses data-points for komatiite-suitevolcanic and plutonic rocks of mafic and ultramafic composition as well as tholeiitic ultramafic cumulates.Data basefor thesecurves include Arndt (l9ZZ), lJndt et al. (1977), Naldrett & Cabri (1976)and MacRae (1969).Symbols for Kanicheedara as in previous diagrams; open symbols are for cycle 5 and solid symbols for cycles2, 3 and 4. Large solid circles are for olivine (OL) and pyroxene (PX) ultrarnafic cumulatesand komatiitic (G) and tholeiitic (T) gabbros, all from layeredsills, Cape Smith Fold Belt, Quebec(Francis & Hynes 1979).Large solid triangles KC5, and KC5" representtwo estimatesof magma composition from which cycle-5 cumulates (Kanichee) crystallized. 106 THE CANADIAN MINERALOGIST two estimatesof the magmacomposition from which The few remainingdata-points for ultramafic com- cycle-5rocks crystallized(Table 2) supportthis con- positions and the singledata-point for quartz gab- clusionand indicatethat thesecompositions are not bro lie in the tholeiitic field, whereasthe compos! membersof a typical komatiitic (AUK) suite (see tions of the olivine gabbroslie wholly within the field Nesbitt et ol. 1979\. for rocks of the komatiitic suite.One estimateof the By far the most widely used chemicalvariation- magma composition for cycle 5 lies within the diagrams in the recent geological literature to tholeiitic field, whereasthe other is in an area in distinguishrocks of komatiitic affinity from those which the tholeiitic and komatiitic fields overlap. The of tholeiitic suites[or of komatiitic and magnesian trend exhibitedby the Kanicheedata is similar to that affinity from thoseof the magnesiantholeiite suite, illustrated by gabbrosand ultramafic cumulatesfrom usingJolly's (1980) terminologyl are those in which layered sills describedby Francis & Hynes (1979). MgO is plotted versus TiO2 and AlrO, versus Theserocks occur within a volcanic sequencecon- FeO*,/(FeO*+ MgO). In themselves,these diagrams taining spinifex-bearingkomatiitic . are not infallible, as Nesbitt et al. (1979)and Naldrett In the Al2O3 versus FeO*/(FeO* + MgO) (1981)pointed out. The boundaryseparating the two diagram(Fig. 1l), the ultramaficrocks of all cycles suitesin the latter plot should be usedwith caution from the Kanicheecomplex plot wholly within the whenextended to regionsother than the Abitibi belt, tholeiitic field of the diagram, whereasthe two a point emphasizedby Nesbitt et ol. (1979). ln estimatesof the parent magma for cycle 5 and the Figuresl0 and 11,we presenton thesetwo diagrams olivinegabbros from this cycleplot on the komatiitic data for the various cyclesof the Kanicheecomplex side of the figure; the olivine gabbro compositions and for layered sills, most of which are from the plot in a regionin whichvolcanic rocks of komatiitic, Abitibi belt. tholeiitic, or Al-rich basalticaffiliation may plot, as In the MgO versusTiO2 diagram, compositions recognizedby Naldrett& Goodwin(1977). The single of most of the ultramafic rocks fall in the area in quartzgabbro composition lies in the tholeiitic field, which both tholeiitic and komatiitic fields overlaD. as it doesin Figure 10. In this diagram,the Kanichee

THEOSGABBROS

FREDS -; wT. GABBROS % DUNDONALD GABBRO Ahor THOLEIITES

OS CI'MULATES

.\oUNDoNALD CUMULATES

o.l o.2 0.3 0.4 0.5 0.6 0.7 0.8 F"ilG"d*r,,tso) Frc. I 1. Distinction betweenrock typesin layeredmafic-ultramafic sills oi tholeiitic and komatiitic affinities on a wt. alo Al2O3versus FeO*/(FeOx + MgO) diagram (FeOErepresents total Fe expressedas FeO). Boundary for fields of komatiitesand tholeiitesis from Naldrett & Cabri (1976);triangular areaoutlined in vicinity of gab- bros of komatiitic affinity is from Naldrett & Goodwin (1977).Solid curvesoutline mafic and ultramafic plutonic rocks of tholeiitic affinity; dashedcurves for similar rock-typesof komatiitic affinity. Sourceof data baseand characterof symbolsas in Figure 10. THE KANICHEE LAYERED COMPLEX r07

data are comparedro trenils exhibited by layered CaOlAl2O) for chilled marginal rocks and the bodiesof both tholeiitic (Dundonaldsill and Theo's absenceof spinifex in theserocks. Thesefeatures flow) and komatiitic (Fred's flow) affinity. The trend contrast with those reported for layeredmafic sills of the Kanicheedata differs from both thesegroups of similar mineralogyin Minnesota (Schultz 1982); and from the komatiitic trend exhibited by the there, pyroxenespinifex is observedin the chilled cumulatesand differentiates of the layeredsills from margin of the intrusion, and estimatesof the com- the Cape Smith Fold Belt (Francis& Hynes 1979), position of the parent magma [in terms of also plotted in Figure 10. Al2O3/TiO2and CaO/AlrO3 ratios and Al2O, ver- A majority of the analytical data from the szs FeO*/(FeO* + MgO)l are consistentwith a Kanicheecomplex plotted in Figure l0lies within the komatiitic basalt composition. overlappingregions of the tholeiitic and komatiitic fields. For this reason, the diagram offers no Suvvany definitive information concerningthe chemicalaf- finity of the parentmagma of this complex.In terms The relevantpoints of Figure ll, the chemistry of the ultramafic to be emphasizedconcerning the geologyand origin of cumulate rocks suggestthat they formed from a the Kanicheelayered in- trusive complexinclude tholeiite magma-source,whereas the gabbroic dif- the following: l) The com- plex consists five ferentiates(olivine-bearing types) are as magnesian of magmaticcycles, each of which originatedfrom very or more so than the gabbros from the layered similar magma-sourcesto form four cyclesof ultramafic komatiitic sills shown in Figure ll. The weak Fe- cumulatesand a final cy- cle that also has gabbroic enrichmenttrend shown by the olivine gabbros in differentiates. In each. olivine, chromite and cycle5 of the Kanicheecomplex is also exhibitedby clinopyroxeneare the major phases; the plagioclase-richdifferentiates (anorthositic gab- cumulus plagioclaseis a significantcumulus phasein the final cycle. 2) bros) in the layered komatiitic sills (Ship Hill and Each cycleof cumulates has Koedebodies) from the Kaapmuidenarea, Barber- crystallized from a high-magnesiumbasaltic magma. The order ton Land, (Viljoen & Vil- of appearanceof the cumulus phases in joen 1970).Such differentiation trends clearlv con- each cycle, the value of the ratios trast with the more regularFe-enrichment putt..ns Al2O3,/TiO2and CaO/Al2O, for two estimatesof the parent exhibited by both the komatiitic and magnesian composition of the magma, and the absence tholeiite sills illustrated in Figure 11. Factors such of olivine or clinopyroxenespinifex in rocks at the margin of as (l) the FelMg ratio of the silicatephases that form the intrusivebody, all indicatethat this magma (1980) the ultramafic cumulates,(2) the presenceand pro- is a memberof Jolly's magnesian portions of Fe-rich cumulate phases other than tholeiite suite. 3) The remobilization of disseminated postcumulus olivine and pyroxenes,e.g., spinel-groupminerals, Ni-Cu sulfidesand associatedAu and platinum-group processes and (3) the proportion and compositionof the in- metalsby hydrothermal in- peridotite terstitial postcumulusliquid to thesecumulate phases to vein systemsin the olivine of the earliest in the ultramaficrocks, all will determinewhere both cycle of the complex is responsiblefor significant the ultramafic cumulatesand gabbroicdifferentiates concentrationsof theseelements. Owing to the ab- normally precious plot in the AlrO, versusFeO*./(FeO* + MeO) high concentrationsof metals, periodically diagram.It is beyondthe scopeof this paperto pur- theserocks have been mined over the past years. suethe topic further, but it is clearat this point that 60 the interpretationof thesevariation diagramsshould be viewedwith caution when individual whole-rock AcloqowtencEMENTS compositionsfrom layeredsills and flows are used to estimate the chemical affinity of the parent This researchhas beensupported by grantsfrom magmas. the Natural Sciencesand .Engineering Research Taken in its entirety, the available information Council and the Departmentof Energy, Mines and suggeststo us that all five cyclesof the Kanicheein- Resources.This study wasmade possible by the co- trusivecomplex crystallized from repeatedpulses of operation of R. Stavely and J. Koza of Kanichee a high-magnesiumbasaltic magma. It is a member Mines Inc. In periodic visits to the mine site during of Jolly's (1980)magnesian tholeiite suite, as is rhe the period 1976-1977,much generous technical composition of the magmasfrom which the Dun- assistancewas provided by Mr. L. Belamy and his donald sill and Theo's flow crystallized;both have associateson the mine staff, for which the authors a similar proportion of clinopyroxenecumulates to are particularly grateful. Constructivecriticism of that observedin cycle 5 of the Kanicheecomplex. the various versionsof this manuscript by colleagqes We suspectthat the layeredsills reportedby Francis in the Departmentof Geology,Laurentian Univer- & Hynes (1979)may also be membersof this suite, sity and by two external refereeshave measurably basedupon their analytical data (AlrO,,zTiO, and improved the quality of the paper. 108 THE CANADIAN MINERALOGIST

RsFsRENcss (1979):Rocks whose composition is determin- ed by crystal accumulation and sorting. In The ARNDT,N.T. (1977):Thick layeredperidotite-gabbro Evolution of Igneous Rocks, Fiftieth Anniversary flows in MunroeTownship, Ontario. Can. J. Perspectives(H.S. Yoder, Jr., ed.), Princeton Univ. Earth Sci. 14, 2620-2637, Press,Princeton, N. J.

NernRErr,A.J. & Pvrn, D.R. (1977): & Banacan,W.R.A. (1971):A guideto the Komatiiticand iron-rich tholeiitic of Munroe chemical classification of the common volcanic Township, northeastOntario. J. Petrologt lE, rocks. Can J. Earth Sci. E. 523-548. 319-369. - & Sunn, C.H. (1967):The ultramaficrocks of BENNerr,G. (1978): Geology of the Northeast the Muskox intrusion. Northwest Territories. Temagamiarea, District of Nipissing.Ont. Geol. Canada.In Ultramafrc and RelatedRocks @.J. Sun. Rep. 163. Wyllie, ed.). John Wiley & Sons,New York.

& INNss,D.G. (l97la): ChambersTownship, Jorlv, W.T. (1980): Development and degrada.tionof District of Nipissing.Ozl. Dep. MinesNorthern Af- lavas, Abitibi area, Canada, in light of ma- fairs, Prelim. Geol. Map P666. jor element . J. Petro logy 21, 323-363.

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