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

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The following Preliminary Maps have been published: 1. Map P.3543—Revised: Precambrian Geology of Ben Nevis and Katrine Townships by A.S. Péloquin. 2. Map P3544—Revised: Precambrian Geology, Parts of Godfrey, Turnbull, Carscallen and Bristol Townships by B. Hathway and S.M. Hocker. 3. Map P.3546—Revised: Precambrian Geology of Gauthier Township Transect by V.O. Ispolatov and B. Lafrance. 4. Map P.3547—Revised: Precambrian Geology, Parts of Whitney and Hoyle Townships by R. Bateman. 5. Map P.3555: Precambrian Geology of Tisdale Township and Parts of Deloro, Mountjoy and Ogden Townships by R. Bateman. 6. Map P.3556: Precambrian Geology, Parts of Godfrey, Robb, Jamieson, Loveland, Macdiarmid and Thorburn Townships by B. Hathway. 7. Map P.3557: Precambrian Geology of Munro Township by A.S. Péloquin, M.G. Houlé and H.L.Gibson. 8. Map P.3558: Precambrian Geology of Teck Township Transect by V.O. Ispolatov. The following Miscellaneous Release—Data (MRDs) of digital data have been published: 1. MRD 144: Geochemical, Petrographic and Compilation Data from the Genex Mine Area, Kamiskotia Area: Discover Abitibi Initiative by S.M. Hocker, P.C. Thurston and H.L. Gibson. 2. MRD 155: Digital Compilation of Maps and Data from the Greenstone Architecture Project: Discover Abitibi Initiative by J.A. Ayer, P.C. Thurston, R. Bateman, H.L. Gibson, M.A. Hamilton, B. Hathaway, S.M. Hocker, G. Hudak, B., Lafrance, V., Ispolatov, P.J. MacDonald, A.S. Péloquin, S.J. Piercey, L.E. Reed, P.H. Thompson and H. Izumi 3. MRD 162: Magnetic and Gravity 3D Modelling Products: Discover Abitibi Initiative by L.E. Reed. GEOLOGICAL SETTING The Superior Province is the nucleus of the North American continent and consists of a collage of easttrending primarily Neoarchean sedimentary and granite-greenstone subprovinces surrounding a central nucleus of Mesoarchean gneissic units with minor greenstone belts. The Abitibi Subprovince is the southernmost of the subprovinces. The subprovince is bounded to the north by sedimentary rocks of the Opatica Subprovince, to the south by sedimentary rocks of the Pontiac Subprovince and to the southeast by rocks of the Mesoproterozoic Grenville Province. The Abitibi Subprovince is interrupted by the northnortheast-trending Kapuskasing structural zone, a west-dipping thrust of Paleoproterozoic age, which exposes granulite facies mid-crustal equivalents of the Abitibi Subprovince (Percival and West 1994). This southern part of the greenstone belt consists of 6 major volcanic lithotectonic assemblages and two unconformably overlying primarily metasedimentary assemblages (Ayer, Amelin et al. 2002). The volcanic assemblages range in age from the ca. 2750 Ma Pacaud assemblage to the 2703 to 2696 Ma Blake River assemblage. In the following sections, the stratigraphy of the southern Abitibi greenstone belt is reviewed, emphasizing revisions to the stratigraphy established during the course of this project. 4
Geochronology The Greenstone Architecture Project has resulted in the processing of 52 samples for age determinations by the following methods: 1. 36 samples collected during the 2003 and 2004 field seasons were processed to extract suitable minerals at the Jack Satterly Geochronology Laboratory (JSL), Department of Geology, University of Toronto. Of these samples, 29 were found to contain suitable minerals for U/Pb geochronology using thermal ionization mass spectrometry (TIMS). 2. 5 samples that had received TIMS analysis prior to this project were selected for additional zircon analysis using the TIMS at the JSL. These samples were selected to provide more precise ages in areas relevant to the goals of the project. 3. 11 samples that had received TIMS analysis either prior to, or during the project, were selected for additional analysis using the sensitive high-resolution ion microprobe (SHRIMP) at the Geological Survey of Canada. This was done to better understand zircon inheritance and provenance in volcanic, sedimentary and intrusive units relevant to the goals of the project. THERMAL IONIZATION MASS SPECTROMETRY (TIMS) RESULTS A summary of the new thermal ionization mass spectrometry (TIMS) age results is presented in Table 1. The locations and ages of all U/Pb geochronology samples are shown on Figure 2 (back pocket) with new geochronology results highlighted and numbered to correlate with the numbers on Table 1 and are presented in graphical form (concordia diagrams) in Figures 3 to 8. These results are also discussed in “Stratigraphic Framework” and “Intrusion Framework” below. The analytical methodology, reports on each sample (including samples without minerals suitable for geochronological analyses) and detailed analytical results for individual analyzed fractions from each sample are provided in Appendix 1 (Table A1). SENSITIVE HIGH-RESOLUTION ION MICROPROBE (SHRIMP) RESULTS Ion microprobe U-Th-Pb isotopic analyses were carried out using the SHRIMP II facility at the Geological Survey of Canada, Ottawa, on representative zircon grains from 11 samples from the southern Abitibi greenstone belt in order to address two principal issues. First, we sought to understand better the occasional patterns of xenocrystic inheritance revealed, sometimes cryptically, in several magmatic samples for which ages were obtained using conventional isotope dilution thermal ionization mass spectrometry (TIMS). Secondly, the relatively rapid analytical routine possible with the SHRIMP allows for a far greater canvassing of detrital zircon populations present within any given metasedimentary unit and, thus, more statistically valid variations in provenance source patterns could be characterized by this method compared to TIMS. Detailed backscattered electron and cathodoluminescence imaging of a large number of zircons (typically 75–100 grains) from igneous lithologies allowed for the rapid identification of a number of zircons suspected to contain inherited, xenocrystic cores. In most cases, these were present as texturally distinct, rounded cores (with or without signs of internal growth or compositional zoning) or as embayed grain centres occasionally with truncated growth zoning, surrounded most commonly by oscillatoryzoned (magmatic) subhedral mantles or sharply prismatic euhedral igneous overgrowths. Rounded or subrounded cores were frequently surrounded by a series of radial cracks that propagate out to the grain exteriors. 5
Page 1: ISBN 0-7794-8652-8 THESE TERMS GOVE
Page 5: 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 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 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
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66 Figure 26. A generalized map of
Page 94 and 95:
1999) in their REE patterns and oth
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plumbing system geometrically stabl
Page 98 and 99:
GOLD MINERALIZATION Production comm
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The Narrows Break mineralized zone,
Page 102 and 103:
Table 7. Diagnostic mineral assembl
Page 104 and 105:
anomaly and the Dome Mine (Figures
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Recommendations • Further testing
Page 108 and 109:
of the inversion product. (Recent a
Page 110 and 111:
the evidence for pre-Pacaud strata
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plutonism suggests the onset of reg
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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
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References Ames, D.E., Bleeker, W.,
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Bleeker, W., Parrish, R.R. and Sage
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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
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Péloquin, A.S., Verpaelst, P., and
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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
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Therefore, on geochronological grou
Page 150 and 151:
Three individual grains were analyz
Page 152 and 153:
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
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
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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Overview of Results from the Greenstone ... - Geology Ontario

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