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

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Figure 20. Geological sketch map of the Kamiskotia area, with locations of known VMS deposits and samples used for U/Pb geochronology (from Hathway, Hudak and Hamilton 2005, p.3). Age 2719.5±1.7 Ma (at very top of figure) is from Ayer, Amelin et al. (2002); 2705±2 Ma (near bottom of figure) is from Barrie and Davis (1990). 48
KVC are to the east or northeast, except in south-central Jamieson Township where southwest-facing indicators at outcrop (pillow packing) and in drill core (graded felsic tuff units) suggest the presence of a possible synclinal axis. South of the Steep Lake fault (see Figure 20), the KVC consists largely of coherent rhyolite and associated rhyolitic breccia and lapilli tuff, with lenses of mafic lava in northeast Carscallen and northwest Bristol townships, and around and to the south of the Genex Mine. Farther north, the lower part of the KVC consists largely of pillowed and massive mafic lava, whereas the upper part is dominated by rhyolite (e.g., Ski-Hill and Godfrey Creek units: see Figure 20). A 150 to 200 m thick, northeast-facing interval of tuffaceous sandstone and conglomerate, with minor graphitic mudstone is present in a series of drill holes approximately 1 km northeast of the Kam-Kotia Mine. Similar sedimentary strata sectioned by several drill holes in southern Jamieson Township appear to lie broadly along strike from the sections northeast of Kam-Kotia and, if the westward facing reported from one Falconbridge core is discounted, could represent a southeastward extension of that interval. Similar clastic rocks also occur in the Genex Mine hanging wall (Hocker, Thurston and Gibson 2005a). As with re-deposited volcaniclastic facies throughout the KVC, these intervals all appear to have been deposited by sediment gravity flows, and there seems to be no evidence for deposition above storm wave base. The KVC sample set analyzed in the present study is strongly bimodal, with a compositional gap between 56 and 72 weight % SiO 2 . Rhyolites in the lower part of the KVC and at the level of the VMS deposits include FII and low-Yb FIIIb types, with minor high-Yb FIIIb rocks, whereas rhyolites in the upper part of the KVC are uniformly of the high-Yb FIIIb type. Hart (1984) divided the KVC mafic volcanic rocks in Godfrey, Jamieson and Robb townships into primitive and overlying, more evolved types. New geochemical data obtained in this study supports this division, which is clear on plots of TiO 2 against Zr and P 2 O 5 (see also Hocker, Thurston and Gibson 2005a, p.18, Figure 6). The contact between the two types appears to coincide with the VMS-hosting interval at the Canadian Jamieson and Kam-Kotia mines. On the Jensen plot, both types fall in the tholeiitic basalt field, but lavas lying stratigraphically above the VMS deposits are more iron-rich than those below. Both types have relatively flat chondrite-normalized REE patterns, generally with slight to moderate negative Eu anomalies, but there is a consistent increase in total REE concentrations stratigraphically upward from the primitive into the more evolved lavas. The mafic lavas from Carscallen and Bristol townships fall in the alkali basalt field on the Nb/Y versus Zr/TiO 2 plot (see also Hathway et al. 2005, p.16, Figure 4). Their REE patterns are also unlike those seen in other groups, showing relatively steep, smoothly S-curved negative slopes in the middle and light REE, and no Eu anomaly. These rocks are geochemically distinct from the KVC tholeiitic basalts to the northeast. Given their stratigraphic position at or near the base of the KVC, it is possible that they may represent part of the Kidd–Munro assemblage, which is present farther to the southwest in Carscallen Township (Ayer, Amelin et al. 2002). KAMISKOTIA GABBROIC COMPLEX The Kamiskotia Gabbroic Complex (KGC) has generally been thought to be broadly coeval with the KVC, which it underlies and intrudes (e.g., Barrie 1992). Barrie (1992) divided the KGC into four zones, of which only the uppermost two are found in the present study area. Gabbro of the “Upper Zone” is exposed to the northeast and southwest of Kamiskotia Lake and in a small area to the northeast of Steep Lake. Remaining KGC rocks in the area are generally of felsic to intermediate composition and were included in the “granophyre zone”, lying above and along strike with the Upper Zone, by Barrie (1992). A new age of 2704.8±1.4 Ma for a granophyric phase of the Upper Zone gabbro is younger than a previous age of 2707±2 Ma from the stratigraphically lower, Middle Zone gabbro in Turnbull Township (Barrie and Davis 1990). The new age is slightly older than (although within error of) the new age of 2703.1±1.2 Ma from the lower part of the KVC. However, it is significantly older than the 2700.0±1.1 Ma KVC rhyolite age 49
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ISBN 0-7794-8652-8 THESE TERMS GOVE
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ONTARIO GEOLOGICAL SURVEY Open File
Page 9:
Contents Abstract .................
Page 13:
Appendix 1. Thermal Ionization Mass
Page 17:
Miscellaneous Release—Data 155 Di
Page 21:
The Timmins area and Kirkland Lake-
Page 25: Overview of Results from the Greens
Page 28 and 29: 3. The geophysical subproject funct
Page 30 and 31: The following Preliminary Maps have
Page 32 and 33: Samples with zircons analyzed by SH
Page 34 and 35: Figure 4. U/Pb concordia plots of T
Page 36 and 37: Figure 6. U/Pb concordia plot of TI
Page 38 and 39: Targeting of several of these overg
Page 40 and 41: Figure 10. U/Pb SHRIMP results from
Page 42 and 43: In northwest Cleaver Township, a fe
Page 44 and 45: SHRIMP U/Pb dating was carried out
Page 46 and 47: 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 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 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
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04BHA-0462 Granophyre, Kamiskotia G
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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
Page 164 and 165:
Table A2. Ion microprobe (SHRIMP II
Page 166 and 167:
Table A2. continued Struct. U Th Pb
Page 168 and 169:
Table A2. continued 204 U Th Pb* Pb
Page 170 and 171:
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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