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

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GOLD MINERALIZATION Production commenced in 1915 and, through the 20 th century, the Macassa, Kirkland Lake Gold (later Kirkland Minerals), Teck–Hughes, Lake Shore, Wright–Hargreaves, Sylvanite and Toburn mines collectively produced 758.3 metric tonnes of gold with an average grade of 15.21 g/t (Gosselin and Dubé 2005) from one giant gold deposit (the Kirkland Lake deposit). Underground workings extend to ~2.5 km below the surface in the central part of the orebody, and mineralization remains open to depth (Charlewood 1964). The Upper Canada Mine produced 43.49 tonnes of gold at a grade of 10.3 g/t. Gold mineralization examined in this study includes the gold lodes of the Kirkland Lake deposit (underground in Macassa Mine and surface exposures on Wright–Hargreaves, Lake Shore, and Teck–Hughes properties), the past-producing Upper Canada Mine (L zone), and occurrences hosted by the LLCDZ. Mineralization of the Upper Canada Mine (Gauthier Township) is confined to a ductile Upper Canada deformation zone. In the L zone, the most productive mineralized zone of the mine, gold occurs in thin (2–5 mm) S2-parallel, quartz-carbonate bands or veinlets in quartz-sericite-carbonate-pyrite pervasively altered and foliated Timiskaming assemblage tuff. Strong bulk carbonatization is characteristic of the mineralized zone. As evident from relationships of alteration assemblages and deformational fabrics, hydrothermal activity spanned through three deformation stages (D2 to D4). Gold mineralization was emplaced relatively early, during D2, and was overprinted by subsequent deformation. The D4 overprint is particularly notable: the mineralized zone as a whole and individual gold-bearing quartz-carbonate bands and veinlets are folded into Z-asymmetric folds with locally developed axial planar S4. Gold occurrences at the Anoki and McBean properties are localized within, or in immediate proximity to, the first-order LLCDZ. Mineralized zones are not exposed at surface and were observed in drill core. Mineralization occurs as 1) sulphidized Fe-tholeiite flows (Anoki Main zone); 2) quartz stockworks in carbonate- and carbonate-fuchsite-altered ultramafic rocks (“green carbonate” McBean and Anoki Deep zones); 3) sulphidation and quartz veining with visible gold in Timiskaming clastic rocks, spatially associated with feldspar-phyric dikes (40 East zone); and 4) quartz veining with native gold and sulphides in cherty to graphitic exhalite horizons in basalts (Anoki South). Mineralization is typically accompanied by strong host-rock carbonatization. Relationships between carbonate-fuchsite alteration assemblage and deformational fabrics present in drill core from the footwall of the McBean zone are compatible with broad syn-D2 timing of alteration. Mineralized zones of the McBean and Anoki properties constitute part of a regional-scale hydrothermal system that corresponds to an approximately 20 km long segment of the Larder Lake– Cadillac deformation zone from the Kerr–Addison–Chesterville gold deposit (McGarry Township) in the east to the Anoki area (Gauthier Township) in the west. Other gold deposits of this group include Cheminis and Omega occurrences in McVittie Township. Sulphide-rich replacement ores in mafic (mostly tholeiitic) metavolcanic rocks (“flow ore”) account for most production and resources, native gold-bearing quartz stockworks in carbonate-fuchsite-altered meta-ultramafic rocks (“green carbonate ore”) rank second. Gold deposits and occurrences of the Larder Lake–Cadillac and Upper Canada deformation zones are likely related. The Upper Canada deformation zone is interpreted as a splay of the Larder Lake– Cadillac deformation zone, both structures were active during D2 and likely were hydraulically connected. Geochemical signatures of gold occurrences hosted by two deformation zones are generally compatible. Plunge of ore zones at the Upper Canada Mine and the McBean, Cheminis and Kerr–Addison deposits is approximately parallel to L2, which supports similar structural timing of Upper Canada and Larder Lake–Cadillac gold mineralization. Syn-D2 timing of Upper Canada mineralization documented in this study, and evidence supporting close relationships between the Upper Canada and Larder Lake– Cadillac mineralized systems suggest that gold mineralization hosted by LLCDZ probably was broadly synchronous with D2. 72
Mineralization of Kirkland Lake camp (i.e., Toburn, Sylvanite, Wright–Hargreaves, Lake Shore, Teck–Hughes, Kirkland Lake Gold and Macassa mines) consists of gold and telluride-bearing quartz veins associated with brittle to brittle-ductile Kirkland Lake fault (Main Break) and the ’04 Break, as well as with immediate splays of with these two faults. Presence of open-space-filling textures in veins, and the association of veins with brittle faults suggest relatively shallow crustal levels of mineralization. Relationships of gold-bearing veins, intra-mineral alkalic dikes and deformational fabrics, as well as presence of S4-parallel syn-mineralization stylolites and cataclastic breccias in gold-bearing quartz veins suggest that mineralization could have formed early in the D4 event synchronous with south-over-north reverse-dextral to reverse movement along the Main Break. However, the presently available evidence supporting temporal overlap of mineralization and D4 is relatively sparse, and it is possible that mineralization predated the D4 event. The positive correlation between high tellurium and gold content and the fact that the deposit is hosted within an alkalic multiphase intrusive complex clearly indicate that the Kirkland Lake gold deposit shares very strong analogies with gold deposits related to alkalic magmatism (e.g., Jensen and Barton 2000). The key geological parameters that support such an analogy include 1) location of the mineralized system in an area characterized by protracted multi-stage alkalic magmatism (both volcanic and intrusive) and its spatial association with a multi-phase alkalic stock; 2) gold- and telluride-rich high-grade mineralization; 3) base metal-poor quartz-carbonate veins with high Au/Ag ratio; 4) carbonatization and K metasomatism (sericite alteration); 5) enrichment in molybdenum; and 6) structurally focussed zones of high-grade mineralization. If the Kirkland Lake gold deposit is indeed related to alkalic magmatism, the parent intrusion is yet to be identified. At present, it is impossible to establish a definite genetic link between gold mineralization and any specific magmatic phase. Direct structural relationships imply that mineralization postdated the emplacement and, most likely, complete crystallization of the syenite porphyry stock, because the ore-controlling Main Break and subsidiary structures cut and displace the intrusion in a brittle fashion. Moreover, the ≥2.5 km vertical extent of mineralization in the syenite porphyry, consistent association of gold-bearing veins with discrete brittle faults throughout this vertical interval, and apparent lack of zoning and features indicative of magmatic–hydrothermal transition within the intrusion, imply that hydrothermal fluids probably were not derived directly from the syenite porphyry host. A deep magmatic source (i.e., larger intrusion or magmatic chamber at depth) is more probable. Whether syenitic intrusions exposed at present erosional level and mineralizing fluids of the Kirkland Lake gold deposit were derived from a single deep magmatic source, or they instead represent two different magmatic “events” within the Timiskaming-type, predominantly alkalic magmatic cycle, remains completely unclear. This is mainly because the length of the time gap between emplacement of the syenite porphyry and formation of gold-bearing veins is unknown, due to inconclusive nature of presently available geochronological data. The occurrence of intra-mineral alkalic dikes is important. Even though these very small dikes are unlikely to be genetically related to mineralization, their presence indicates that alkalic magmatism overlapped in time with hydrothermal activity, and thus the existence of a deep magmatic chamber (i.e., potential fluid source) is geologically feasible. However, regardless of the timing of Kirkland Lake mineralization and many uncertain details of its genesis, the distinct metal inventory (Te>Au, Mo, Pb, Ag, high Au/Ag, low As) of gold-bearing veins indicates a distinct fluid source, that is, different from the source that contributed fluids for gold deposits and occurrences clustering along the Larder Lake–Cadillac deformation zone and its splays. Based on presently available data, a deep alkaline magmatic fluid source (magmatic chamber or intrusion at depth) for Kirkland Lake gold mineralization appears most probable. 73
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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
Page 48 and 49: PACAUD ASSEMBLAGE The 2750 to 2735
Page 50 and 51: The iron formation and chert brecci
Page 52 and 53: (thickness) of banded iron-poor iro
Page 54 and 55: clast conglomerates at the top of t
Page 56 and 57: BLAKE RIVER ASSEMBLAGE Lower Part T
Page 58 and 59: The Krist formation consists of cal
Page 60 and 61: Timmins Area In the Timmins area, t
Page 62 and 63: 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 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 114 and 115: Watkinson and Comba 1989; Gibson an
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
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Therefore, on geochronological grou
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Three individual grains were analyz
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03VOI-0422-1 Trachytic lava, Timisk
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03SJP-115-1 Monzonite, Clifford sto
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the original Corfu (1993) age, only
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Table A1. U/Pb isotopic data for zi
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206 Sample Analysis Description Wei
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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
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Metric Conversion Table Conversion
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Chart A. Magnetic and Gravity Three
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Overview of Results from the Greenstone ... - Geology Ontario

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