Overview of Results from the Greenstone ... - Geology Ontario

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Watkinson and Comba 1989; Gibson and Watkinson 1990). However, pyroclastic rocks form an important part of the post-cauldron volcanism (Trudel 1978, 1979; Goutier 1997; Lafrance, Moorhead and Davis 2003). The abundance of base metals associated with highly elevated precious metals in deposits such as the Horne Mine in Noranda, Quebec, and the gold deposits to the east, led Robert and Poulsen (1997) to suggest that some of the gold mineralization in the Blake River Group was related to volcanism. The gold-rich VMS deposits that were formed before main-stage deformation include the LaRonde Penna deposit and the Doyon Mine located between Noranda and Val d’Or in the Doyon–Bousquet–LaRonde gold camp (Dubé et al. 2003). LaRonde is a giant pre-deformation gold-rich synvolcanic VMS deposit (Mercier-Langevin et al. 2004; Dubé, Mercier-Langevin et al. 2004), whereas Doyon is a world-class gold-copper sulphide-rich veintype deposit. The gold-bearing stockwork and sheeted veins at the Doyon deposit are deformed by the main foliation and mineralized veins in the West Zone are cut by pre-D2 deformation diorite dikes. These features suggest that the mineralization is pre- or early main-stage deformation. The Doyon deposit may be associated with the emplacement of a late magmatic phase (tonalite) of the multistage Mooshla pluton (Gosselin 1998; Galley, Pilote, and Davis 2003). Copper-zinc mineralization in the Ben Nevis area occurs within the upper part of the Blake River assemblage, which has a U/Pb age of 2696.6±1.3 Ma. This is younger than the pre-cauldron phase of the Noranda subgroup (2701±1 Ma: Mortensen 1993b), younger than the Misema subgroup in Pontiac Township (2701±2 Ma: Corfu et al. 1989), and of the same age as the post-cauldron phase of the Noranda subgroup (the Reneault–Dufresnoy formation: 2697.9+1.3/–0.7 (Mortensen 1993b) and 2696±1.1 Ma (Lafrance, Moorhead and Davis 2003, and the Bousquet formation: 2698.6±1.5 Ma, 2698.0±1.5 Ma and 2694±2 Ma (Lafrance, Moorhead and Davis 2003). Thus, the Ben Nevis–Clifford volcanic complex formed late in the Blake River Group volcanic event, an area in which gold-rich VMS deposits may also be present. The VMS deposits of the Kamiskotia deposit were previously believed to be part of the Tisdale assemblage, based on an age of 2705±2 Ma from Godfrey Township (Barrie and Davis 1990). However, they are associated with bimodal tholeiitic basalts and rhyolites and occur with a single stratigraphic horizon that has an age of 2700 Ma, all of which indicate they are more similar to the Blake River age and style of VMS mineralization. Unconformable juxtaposition of the VMS-rich Kidd–Munro and Blake River assemblages indicates that the northwestern part of the study areas had a long history of formation of significant VMS deposits and, thus, is an area that is worthy of focussed exploration for new Cu-Zn deposits (see “Kamiskotia Subprojects”). West of the Kamiskotia area, the Montcalm gabbroic complex is a peridotitic to gabbroic intrusion which hosts the Montcalm Ni-Cu deposit. A gabbro from this complex has an age of 2702±2 Ma and is cut by granodiorite dike with an age of 2700+5/–4 Ma (Barrie and Davis 1990). These ages suggest the Ni-Cu mineralization in the Montcalm gabbroic complex is coeval with Blake River assemblage volcanism in the Kamiskotia area. EPIGENETIC GOLD MINERALIZATION There were several phases of hydrothermalism and gold mineralization in the Timmins–Porcupine gold camp. Clasts of colloform-crustiform ankerite vein in conglomerate of the Dome formation at Dome Mine (Dubé, Williamson and Malo 2003) demonstrate early hydrothermal low-grade mineralization. Ankerite veining and minor mineralization in Dome and Aunor mines predate the Timiskaming unconformity, and may be related to D2 thrusting. Copper-gold-silver-molybdenum mineralization in the Pearl Lake porphyry predates main-stage quartz-gold veins in the Hollinger Mine and is post-Timiskaming sedimentation. This gold mineralization, which is perhaps coeval with Lightning zone replacement-style gold mineralization at the Holloway Mine, overprints a Timiskaming-age volcanic unit. At the Holloway Mine, the gold mineralization is itself cut by an inter-mineral dike with an age of 2671.5±1.9 Ma, which 88
is, in turn, overprinted by a later auriferous quartz-carbonate veining event (Ropchan et al. 2002). The bulk of the gold mineralization in Timmins, however, corresponds to auriferous quartz veining in extensional fracture arrays interpreted as syn- to late-S3 foliation. Consequently, this main-stage goldquartz mineralization at Hollinger–McIntyre and Dome mines and in other deposits was the result of late D3 events. The geometry of a significant proportion of quartz veins is structurally compatible with oblique (right lateral, south block up) shear (Bateman, Ayer and Dubé 2005). Regionally, D3 was left lateral, so these vein systems may represent antithetic R′ shear arrays. The extensional network of quartzgold veins at Pamour Mine crosscut S4 foliation with a minimum of deformation, and formed during north-south shortening, dip-slip fault movement (D4). The D5 constriction generated local quartz ladder veins, but probably no new stage of gold mineralization was introduced. This protracted history of deformation and alteration indicate a long-lived or multistage auriferous hydrothermal system, and a plumbing system geometrically stable for long enough to feed gold into a relatively small volume of rock. Variability in timing is reflected in diverse styles of gold mineralization (vein type, vein mineralogy, disseminated, sulphide-rich mineralization), alteration mineralogy (massive ankerite, albite, sericite), sulphide and ore minerals (pyrite, tellurides) and metals (Au, Ag, Cu, Mo, W). Syn-deformation quartz-carbonate vein deposits are commonly spatially associated at the regional scale with Timiskaming-like regional unconformities and suggest an empirical relationship between large-scale greenstone quartz-carbonate gold deposits, deformation opening of these basins, and regional unconformities (Hodgson 1993; Robert 2000; Dubé, Williamson and Malo 2003). This is similar to the deformation–mineralization history recorded in the Archean Kalgoorlie gold camp in southwestern Australia (Bateman and Hagemann 2004). In the Kirkland Lake–Larder Lake camp, gold mineralization in Gauthier Township represents a hydrothermal event distinct from the Kirkland Lake gold lodes. Mineralization at the Upper Canada Mine occurs in a high-strain ductile deformation zone that probably represents a splay of the Larder Lake–Cadillac deformation zone. Although hydrothermal activity spanned three deformation phases (which, in Kirkland Lake–Larder Lake chronology, are identified as D2, D3 and D4), gold was introduced relatively early, during D2 (probably equivalent to D3 in Timmins) and was accompanied by strong bulk carbonatization. Subsequent deformation and, possibly, hydrothermal activity overprinted gold mineralization. Gold occurrences of the Anoki and McBean properties are localized within or in the immediate proximity of the first-order Larder Lake–Cadillac deformation zone. Gold occurs in sulphidized Fetholeiite flows (Anoki Main zone), in quartz stockworks within carbonate- and carbonate-fuchsite-altered ultramafic rocks (“green carbonate”, McBean and Anoki Deep zones), in quartz-sulphide zones hosted by Timiskaming assemblage clastic rocks and locally associated with feldspar-phyric dikes (40 East zone), and in quartz veining with sulphides in cherty to graphitic exhalite horizons enclosed in basalts (Anoki South). In all cases, mineralization is accompanied by extensive carbonatization. Drill cores from the McBean zone show that mineralization and alteration are most likely synchronous with the development of D2 fabrics. Mineralized zones at the Anoki and McBean properties are part of a regionally extensive hydrothermal system that affected an approximately 20 km long segment of the Larder Lake–Cadillac deformation zone from the Kerr–Addison–Chesterville gold deposit (east) to the Anoki occurrences (west). Other similar gold deposits include the Cheminis and Omega deposits in McVittie Township. Most gold production and reserves are from sulphide-rich replacement ores in mafic (mostly tholeiitic) volcanic rocks, whereas native gold-bearing quartz stockworks in carbonate-fuchsite-altered metaultramafic rocks (“green carbonate ore”) are second in importance. Gold deposits and occurrences along the Larder Lake–Cadillac and Upper Canada deformation zones are probably related because they have similar geochemical signatures and similar ore zone plunges roughly parallel to L2. The Upper Canada deformation zone is interpreted as a splay of the Larder Lake–Cadillac deformation zone, and as both structures are syn-D2, they were likely hydraulically connected during the introduction of gold-bearing fluids along these structures. 89
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ISBN 0-7794-8652-8 THESE TERMS GOVE
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ONTARIO GEOLOGICAL SURVEY Open File
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Contents Abstract .................
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Appendix 1. Thermal Ionization Mass
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Miscellaneous Release—Data 155 Di
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The Timmins area and Kirkland Lake-
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Overview of Results from the Greens
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3. The geophysical subproject funct
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The following Preliminary Maps have
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Samples with zircons analyzed by SH
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Figure 4. U/Pb concordia plots of T
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Figure 6. U/Pb concordia plot of TI
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Targeting of several of these overg
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Figure 10. U/Pb SHRIMP results from
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In northwest Cleaver Township, a fe
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SHRIMP U/Pb dating was carried out
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Stratigraphic Framework In this sec
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PACAUD ASSEMBLAGE The 2750 to 2735
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The iron formation and chert brecci
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(thickness) of banded iron-poor iro
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clast conglomerates at the top of t
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BLAKE RIVER ASSEMBLAGE Lower Part T
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The Krist formation consists of cal
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Timmins Area In the Timmins area, t
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Kirkland Lake-Larder Lake Area Hyde
Page 64 and 65: Intrusion Framework The plutonic ro
Page 66 and 67: The youngest dated synvolcanic mafi
Page 68 and 69: Albitite dikes are crosscut by gold
Page 70 and 71: Worming Geophysical Data Treatment
Page 72 and 73: In Timmins, the first generation of
Page 74 and 75: Figure 20. Geological sketch map of
Page 76 and 77: from Halfmoon Lake, only 2 km to th
Page 78 and 79: The Blake River Group is divided in
Page 80 and 81: Figure 22. Geological map of Munro
Page 82 and 83: Mine stratigraphic succession, have
Page 84 and 85: Figure 24. Geological map of Currie
Page 86 and 87: Table 5. Simplified classification
Page 88 and 89: mesocumulate). The Stoughton-Roquem
Page 90 and 91: Shaw Dome Area GEOLOGICAL SETTING T
Page 92 and 93: 66 Figure 26. A generalized map of
Page 94 and 95: 1999) in their REE patterns and oth
Page 96 and 97: plumbing system geometrically stabl
Page 98 and 99: GOLD MINERALIZATION Production comm
Page 100 and 101: The Narrows Break mineralized zone,
Page 102 and 103: Table 7. Diagnostic mineral assembl
Page 104 and 105: anomaly and the Dome Mine (Figures
Page 106 and 107: Recommendations • Further testing
Page 108 and 109: of the inversion product. (Recent a
Page 110 and 111: the evidence for pre-Pacaud strata
Page 112 and 113: plutonism suggests the onset of reg
Page 116 and 117: The Kirkland Lake giant gold deposi
Page 118 and 119: The Timmins and Kirkland Lake-Larde
Page 120 and 121: References Ames, D.E., Bleeker, W.,
Page 122 and 123: Bleeker, W., Parrish, R.R. and Sage
Page 124 and 125: Galley, A.G., Pilote, P. and Davis,
Page 126 and 127: Heather, K.B., Percival, J.A., Mose
Page 128 and 129: Lesher, C.M., 1989. Komatiite-assoc
Page 130 and 131: Péloquin, A.S., Verpaelst, P., and
Page 132 and 133: Stern, R.A. 1997. The GSC sensitive
Page 134 and 135: 108 This page left blank intentiona
Page 136 and 137: THERMAL IONIZATION MASS SPECTROMETR
Page 138 and 139: 04BHA-0462 Granophyre, Kamiskotia G
Page 140 and 141: contrastingly have been dated near
Page 142 and 143: The revised age of 2672.8±1.1 Ma f
Page 144 and 145: fraction (A1a) also overlaps concor
Page 146 and 147: 04JAA-0010 Albitite dike cutting Ti
Page 148 and 149: Therefore, on geochronological grou
Page 150 and 151: Three individual grains were analyz
Page 152 and 153: 03VOI-0422-1 Trachytic lava, Timisk
Page 154 and 155: 03SJP-115-1 Monzonite, Clifford sto
Page 156 and 157: the original Corfu (1993) age, only
Page 158 and 159: Table A1. U/Pb isotopic data for zi
Page 160 and 161: 206 Sample Analysis Description Wei
Page 162 and 163: Appendix 2 Sensitive High-Resolutio
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Table A2. Ion microprobe (SHRIMP II
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Table A2. continued Struct. U Th Pb
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Table A2. continued 204 U Th Pb* Pb
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Table A2. continued 204 U Th Pb* Pb
Page 172:
Metric Conversion Table Conversion
Page 175 and 176:
Chart A. Magnetic and Gravity Three
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