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

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Timmins Area In the Timmins area, the Timiskaming assemblage is confined to a narrow east-trending unit of conglomerates and sandstone overlying the Tisdale and Porcupine assemblages. An angular unconformity occurs along the north contact of the Timiskaming assemblage and it is truncated by the PDDZ and/or the Dome fault to the south (see “Timmins Subproject”). Born (1995) subdivided the Timiskaming assemblage in this area into the lowermost Dome formation, consisting of alluvial sediments grading upwards into proximal and mid-fan turbidites, in turn overlain by the Three Nations formation grading upwards from alluvial to fluvial to shelf-facies sandstones. Two samples from the Dome formation at the Dome Mine were analyzed using the TIMS methods (Ayer, Barr et al. 2003): wacke from the basal part of the Dome formation in the “Greenstone Nose” contains detrital zircons with ages ranging from 2710 Ma to 2679±4 Ma, whereas conglomerate in the “sedimentary trough” yields a broader spectrum of detrital zircon ages ranging from 2814 Ma to 2674±2 Ma (#11 and #12: Figure 2). Less precise SHRIMP results from these 2 samples reveal bimodal age distributions with a significant pre-Abitibi population ranging in age from 2820 to 2780 Ma and an Abitibi-age population ranging from 2730 Ma to approximately 2670 Ma (see Figures 12A and 12B). Detrital zircons from a pebbly sandstone unit with the Three Nations formation in German Township about 25 km to the northeast indicate a considerably younger maximum depositional age of 2669±1 Ma. In addition, older detrital zircons ranging from 2700 to 2816 Ma are also present in this sample (Bleeker 1999). Newly recognized portions of the Timiskaming assemblage consisting of conglomerate, sandstone, siltstone and heterolithic volcanic breccia have been identified along the PDDZ west of the Dome Mine (see Figure 2). A sample of heterolithic conglomerate from the Buffalo Ankerite Mine in Deloro Township yielded ages of ca. 2682±4 Ma and 2669±7 Ma and a fine-grained epiclastic unit at the Nabob Mine in Ogden Township yielded ages ranging from ca. 2673 Ma to 2722 Ma (Ayer, Barr et al. 2003). Further to the west in Thorneloe Township, the youngest detrital zircon age of 2684.4±1.7 Ma from a new geochronology sample of conglomerate closely associated with the PDDZ, in addition to older detrital zircons with ages of 2705 Ma, 2713 to 2716 Ma, 2726 to 2728 Ma (#9: Table 1, Figure 4C), suggest this unit may also be part of the Timiskaming assemblage, although the age of the youngest detrital zircon also allows for the possibility that it may alternatively be part of the Porcupine assemblage. East of Matheson Area Timiskaming assemblage clastic sedimentary rocks composed of conglomerate, wacke-sandstone, siltstone, argillite and schist are closely associated with the PDDZ from the Quebec border to Hislop Township. These rocks were originally lumped together with structurally interleaved older volcanic assemblages in a unit identified as the Destor–Porcupine Complex by Jensen and Langford (1985). Berger (2002) reported banded magnetite-hematite iron formation is complexly interbedded and structurally interleaved with clastic sedimentary rocks in Michaud Township, and sedimentary and alkalic volcanic rocks correlative with the Timiskaming assemblage underlie the southeast part of Hislop Township, south of the PDDZ, and display a close spatial relationship with the Hislop and Ross faults. Ropchan et al. (2002) reported TIMS geochronology results from Timiskaming assemblage units in Holloway Township. The youngest concordant detrital zircons from sandstone interbedded with conglomerate yielded an age of 2684±1.3 Ma, a second discordant zircon (1.8%) yielded an age of 2676.5±1.6 Ma, in addition to older detrital zircons with ages ranging from 2695 to 2724 Ma. The youngest detrital zircon from a heterolithic volcanic breccia closely associated with the Lighting Zone mineralization at the Holloway Mine (sample 3D-CG, #37: Figures 2 and 10A) yielded an age of 2686.6±1.8 Ma with older zircons ranging from 2695 to 2717 Ma. SHRIMP analysis of this sample has yielded less precise zircon ages ranging from 2682 to 2796 Ma (Figure 16). 34
The volcanic breccia sample from the Holloway Mine is texturally and compositionally similar to a Timiskaming assemblage volcanic breccia unit in Swayze Township in the Swayze belt, which yielded a variety of zircon ages based on TIMS analysis, the youngest being about 2669 Ma (Ayer, Ketchum and Trowell 2002). Zircons from this sample (99JAA-0057) were analyzed by SHRIMP and define a full range of morphological types, ranging from elongate and sharply prismatic to short, stubby, subrounded or even very well-rounded grains. The most reliable younger ages from this sample come from analyses of distinct overgrowths or thin embayments, constraining deposition generally at, or younger than, 2672 to 2683 Ma (Figure 17). Concordant or nearly concordant spot analyses from interior igneous domains mostly define a narrow age spectrum between ca. 2695 and 2705 Ma, with a peak age mode near 2700 Ma (see Figure 10B; Appendix 2). Older ages occur near 2730 Ma, 2740 Ma and 2765 Ma and support the earlier observations that the inherited components in this fragmental volcanic were derived from underlying lithologies within the Pacaud, Deloro, Tisdale and Blake River assemblages (Ayer, Ketchum and Trowell 2002). Figure 16. Backscattered electron (BSE) and cathodoluminescence (CL) images of the cores of inherited zircon and a zircon overgrowth from Timiskaming assemblage volcanic sample 3D-CG. The spot locations, numbers and ages correspond with the SHRIMP II analyses in Appendix 2 (Table A2). 35
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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 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 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 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
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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
Page 130 and 131:
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
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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
Page 154 and 155:
03SJP-115-1 Monzonite, Clifford sto
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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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