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

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(thickness) of banded iron-poor iron formation, succeeded by approximately 60 m thickness of heterolithic, unbedded, ungraded felsic pyroclastic breccia, a 5 m thickness of iron-formation conglomerate, 2 to 3 m of wacke in erosional contact with approximately 60 m thickness of monolithic rhyolitic pyroclastic breccia. The felsic volcanic units, given their unbedded, non-graded nature are considered mass-flow deposits. The contact between the chert fragment-bearing wackes and the upper pyroclastic breccia unit is an erosional surface transecting the wacke unit. North of English Township in Bartlett Township, the Deloro–Tisdale assemblages contact is marked by metre-scale feldspathic arkose beds with graphitic arkose tops. It is presumed that this is a more proximal facies of the relationships described in the preceding paragraph. In Carscallen Township at the Wire Gold occurrence (Hall and Smith 2002; see Table 4), iron formation breccia occurs at the contact between the Deloro assemblage and the overlying Upper Unit of the Kidd–Munro assemblage. This contact is interpreted to be a submarine unconformity based on these relationships. In summary, at each of the Deloro–Tisdale assemblages contacts shown on Figure 1, the “iron formation” actually consists of conventional banded iron formation, and/or iron formation conglomerate or other units deposited by mass-flow processes. Using the criteria of Shanmugam (1988), this chert breccia unit in the upper part of the Deloro assemblage is then interpreted as a regional-scale unconformity between the Deloro assemblage in Whitney, Bartlett, Geikie, McArthur and English townships and the overlying Tisdale assemblage and between the Deloro assemblage and the overlying Kidd–Munro assemblage in Carscallen Township. Similarly, the chert breccia unit beneath the lowest Deloro assemblage metavolcanic unit in the Shining Tree area also may represent an unconformity between the Pacaud and Deloro assemblages. STOUGHTON–ROQUEMAURE ASSEMBLAGE The 2723 to 2720 Ma Stoughton–Roquemaure assemblage consists of mafic volcanic rocks with subordinate felsic volcanic rocks and komatiites (~1%) (Sproule et al. 2002). The assemblage has been identified in both the northern and the southeastern parts of the study area (see Figure 2). In the north, the assemblage is conformably underlain by the Hunter Mine group of the Deloro assemblage east of Lake Abitibi batholith in Quebec (Mueller and Mortensen 2002). In the part of the assemblage that crops out south of Kirkland Lake, the basal contact is with the Pacaud assemblage. This contact represents an age gap of about 20 my and, thus, is interpreted to be unconformable. Iron formation in the upper part of the Stoughton–Roquemaure assemblage in this area (i.e., the Catharine group: Jackson and Fyon 1991), and crystallization ages of 2701 Ma with 2720 Ma zircon xenocryst in felsic volcanic rocks of the overlying upper Blake River assemblage (i.e., the Skead group) (Corfu 1993) indicate an unconformity also occurs at the top of this part of the Stoughton–Roquemaure assemblage. KIDD–MUNRO ASSEMBLAGE Lower Part The lowermost part of the Kidd–Munro assemblage ranges in age from 2719 to 2717 Ma. It differs from the more extensive upper Kidd–Munro assemblage by being dominated by intermediate to felsic calcalkalic volcanic rocks. It has been identified in 3 areas (see Figure 2): 1) in the northeast where it was 26
previously identified as the Coulson–Rand assemblage (Jackson and Fyon 1991). Here the lack of an age gap and the presence of xenocrystic zircons with an age of 2723 Ma indicates that it conformably overlies the Stoughton–Roquemaure assemblage located to the north, despite the presence of the North Branch Porcupine–Destor deformation zone at this contact. 2) In the north-central area, where it is complexly infolded with the upper Kidd–Munro assemblage rocks in Dundonald and Clergue townships; and 3) west of the Mattagami River fault in the northwest where a thick sequence of calc-alkalic volcanic rocks have an age of 2719.5±1.7 Ma (Ayer, Amelin et al. 2002). In the latter area, it lies in faulted contact with a northeast-facing unit of the upper part of the Kidd–Munro assemblage to the south, and has unknown contact relationships with rocks assumed to be part of the Blake River assemblage to the north. Upper Part The 2717 to 2711 Ma upper part of the Kidd–Munro assemblage is the traditionally known part of the Kidd–Munro assemblage as identified by Jackson and Fyon (1991). It extends across the northern part of the study area (see Figure 2) and is dominated by tholeiitic mafic and komatiitic rocks with localized accumulations of tholeiitic felsic volcanic rocks and graphitic sedimentary units. In the east, the basal contact is interpreted to be conformable with underlying calc-alkaline volcanic rocks of the lower Kidd– Munro assemblage to the north. To the west, the northern margin is in faulted contact with the Porcupine assemblage. The southern margin lies in faulted contact with sedimentary rocks of the Timiskaming assemblage along the Porcupine–Destor deformation zone (PDDZ) in the east, and the Porcupine assemblage (Pipestone fault) to the west. West of the Mattagami River fault, the assemblage has been sinistrally offset to the south by about 8 km. Here, both the northern and southern contacts are marked by faults. New geochronologic samples with crystallization ages of 2712.3±2.8 Ma and 2714.6±1.2 Ma from central Loveland and southern Thorburn townships (#1 and #2: Table 1, Figures 3A and 3B) confirm the mapping-based interpretation of a northeast-facing package in faulted contact with the lower Kidd–Munro assemblage in Thorburn Township to the north (see “Kamiskotia Area Subprojects”). In addition, one of these samples was found to contain a pre-Abitibi-age xenocryst with an age of 2861.4±1.7 Ma (#2: Table 1, Figure 3A). A less extensive part of the upper Kidd–Munro assemblage also occurs south of the Kamiskotia area. Here, the assemblage faces to the northeast and unconformably overlies iron formations at the top of the Deloro assemblage to the south (see above). Newly extracted zircons from a previously sampled overlying felsic tuff in Carscallen Township (Ayer, Amelin et al. 2002) yielded a more precise crystallization age of 2712.2±0.9 Ma (#8: Table 1, Figure 4B). This indicates an age gap of approximately 12 my exists between the unconformably underlying Deloro and the upper Kidd–Munro assemblages at this locality. The newly analyzed zircons from this sample also revealed the presence of a discordant pre- Abitibi xenocryst with an age of 2853.6±1.4 Ma (see Figure 4B). TISDALE ASSEMBLAGE Lower Part The lowermost part of the Tisdale assemblage ranges in age from 2710 to 2706 Ma. It consists predominantly of tholeiitic mafic volcanic rocks with localized accumulations of komatiite, intermediate to felsic calc-alkaline volcanic rocks and iron formation. It is widespread in the central part of the map area where it forms the nose and limbs of a broad west-closing synclinorium cored by the Blake River assemblage (see Figure 2). The basal contact of Tisdale assemblage is marked by iron formation and chert 27
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 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 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 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
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 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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