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

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the original Corfu (1993) age, only more precise. Regression of the more discordant, turbid and cracked zircon analyses (2z, 3z) together with those for the older four baddeleyites (5bd, 6bd, Bd-1 and Bd-2) results in an unrealistically old upper intercept age (2724 Ma), which is greater than the accepted age of the host Kidd–Munro assemblage volcanic rocks (ca. 2719–2711 Ma: Nunes and Jensen 1980; Corfu et al. 1989; Barrie and Davis 1990; Corfu and Noble 1992; Corfu 1993; Ayer et al. 2002). This fact, combined with the agreement to the earlier Corfu (1993) result, suggests that the 2712.4±1.1 Ma age represents an accurate and precise estimate of the timing of emplacement of the Ghost Range sill. The age for the Ghost Range gabbroic complex is now considered distinct and separate from the age of other mafic to ultramafic complexes found elsewhere in the Kidd–Munro assemblage, including the 2706.8±1.2 Ma Centre Hill complex (this report), the Munro–Warden sill (2704.9±1.9 Ma: Barrie 1999), the Dundonald mafic to ultramafic sill (2707+3/–2 Ma: Barrie and Corfu 1999), as well as the 2707 to 2705 Ma Kamiskotia Gabbroic Complex (2707±2 Ma gabbro: Barrie and Davis 1990; Corfu and Noble 1992; 2704.8±1.5 Ma granophyre: this report). Regional mafic to ultramafic intrusions elsewhere in the Timmins–Kidd Creek area also include the Mann mafic to ultramafic intrusion in Mann Township (2704 .0±4.9 Ma; Barrie 1999) and a dunite differentiate from Deloro Township (2707+3/–2 Ma; Corfu and Noble 1992; Corfu 1993), both of which are distinctly younger than the Ghost Range sill age refined here. 04JAA-0001 Quartz-phyric felsic flow, southwest Munro Township This sample was collected to establish a precise age for the base of the Kidd–Munro assemblage in Munro Township. Unfortunately, no datable accessory phases were found in the heavy mineral concentrate processed from this sample. 04JAA-0002 Leucogabbro, Centre Hill complex, north-central Munro Township (NAD83, Zone 17 UTM 558199E, 5383067N; #39 on Figure 2 and Table 1) A coarse-grained variety of leucogabbro exists in the upper fractionated portions of the Centre Hill mafic to ultramafic complex. A sample of this unit was collected for dating purposes to test the hypothesis that the Centre Hill complex might represent a synvolcanic intrusion related to the VMS mineralization in the overlying Potter Mine. The Centre Hill leucogabbro contained a moderately abundant population of both zircon and baddeleyite. Zircon occurs as large, colourless, sometimes cloudy, subhedral to anhedral grains with square cross-sections or as skeletal grains with flat, flange-like or partly hollow crystals. Some crystals are fragments of larger euhedra and many grains are cracked. Discrete, smaller and rounded, xenocrystic zircons are also present and were excluded from analysis. Baddeleyite grains in this sample occur as fineto medium-grained, brown, striated blocky and blade varieties. Most baddeleyite grains show a dull lustre suggestive of a fine-grained partial overgrowth or replacement by fine-grained zircon, an observation confirmed by secondary electron imaging. Isotope dilution results for two zircon single-grain analyses are shown in Table A1 and Figure 8D. The data are only slightly discordant (0.4–0.5%) and have identical 207 Pb/ 206 Pb ages at 2706.6 and 2706.9 Ma. Results for two analyzed single grains of baddeleyite (unabraded) are slightly more discordant (1.0–1.4%) but yield similar 207 Pb/ 206 Pb ages as the zircon analyses. Regression of all four analyses results in an upper intercept age of 2706.8±1.2 Ma with a very high probability of fit (94%; MSWD = 0.13). The regression is anchored through the origin and the goodness of fit for this discordia suggests that the Pbloss behaviour observed in the baddeleyites is a result of modern (zero-age) disturbances and not an older secondary Pb-loss event. Thus, the partial zircon frosting present on the baddeleyites likely reflects local, late saturation of the magma in silica rather than a younger metamorphic reaction. 130
A primary magmatic crystallization age of 2706.8±1.2 Ma for leucogabbro from the Centre Hill mafic to ultramafic complex is similar in age to the nearby Munro–Warden sill at 2704.9±1.9 Ma (Barrie 1999), the Middle Zone gabbro of the Kamiskotia Gabbroic Complex (2707±2 Ma: Barrie and Davis 1990), and the mafic Dundonald sill (2707+3/–2 Ma: Barrie and Corfu 1999) all of which were emplaced into slightly older rocks of the Kidd–Munro assemblage. 131
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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
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Intrusion Framework The plutonic ro
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The youngest dated synvolcanic mafi
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Albitite dikes are crosscut by gold
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Worming Geophysical Data Treatment
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In Timmins, the first generation of
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Figure 20. Geological sketch map of
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from Halfmoon Lake, only 2 km to th
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The Blake River Group is divided in
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Figure 22. Geological map of Munro
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Mine stratigraphic succession, have
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Figure 24. Geological map of Currie
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Table 5. Simplified classification
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mesocumulate). The Stoughton-Roquem
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Shaw Dome Area GEOLOGICAL SETTING T
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66 Figure 26. A generalized map of
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1999) in their REE patterns and oth
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plumbing system geometrically stabl
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GOLD MINERALIZATION Production comm
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The Narrows Break mineralized zone,
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Table 7. Diagnostic mineral assembl
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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
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 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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