Geologic Setting of the Devonian-Mississippian, Rea and Samatosum VMS Deposits of the Eagle Bay Assemblage, Adams Lake Area, South Central British Columbia (original) (raw)
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2012
The southern part of the Craig subterrane of the Alexander terrane, which extends from Prince of Wales Island southward into coastal British Columbia, contains an Ordovician volcanic-sedimentary-intrusive suite of probable back-arc affinity, the Moira Sound unit. Mapping, prospecting, and geochronological work as part of the GEM-Edges project in 2009-2011 identified small sulphide occurrences within and adjacent to Ordovician rhyolites and rhyolite breccias of this unit. The previously known Pitt VMS occurrence on Pitt Island consists of a 3.5 kilometre-long trend of base-metal sulphide bodies aligned along a major shear zone that marks the southwestern limit of ductile shearing related to the mid-Cretaceous Grenville Channel fault. Deformation of the sulphides and their host quartz-muscovite schists is so intense that an epigenetic, synkinematic origin cannot be ruled out on geological grounds. However, chalcopyrite and sphalerite separates from the main Pitt showing yield lead iso...
Economic Geology, 2008
The Upper Archean volcanic succession in the Kamiskotia area (Abitibi greenstone belt, Timmins region) hosts a series of past-producing copper-zinc volcanic-associated massive sulfide (VMS) deposits. All of these occur within a restricted, east-facing stratigraphic interval in the upper part of the Kamiskotia Volcanic Complex. New U-Pb ages for this interval, ranging from 2701.1 ± 1.4 to 2698.6 ± 1.3 Ma, and an age of 2703.1 ± 1.2 Ma from the lower part of the Kamiskotia Volcanic Complex, indicate that the complex is likely part of the Blake River assemblage (2701-2697 Ma) rather than the older Tisdale assemblage (2710-2703 Ma). The Kamiskotia Volcanic Complex consists largely of felsic and mafic lava flows, and VMS mineralization appears to have generally developed at or near the sea floor close to inferred synvolcanic faults. New U-Pb ages of 2714.6 ± 1.2 and 2712.3 ± 2.8 Ma from the northeast-facing volcanic succession in the northern part of the study area (Loveland, Macdiarmid, and Thorburn Townships) indicate that it forms part of the Kidd-Munro assemblage (2719-2710 Ma). A west-northwest-trending faulted contact is inferred between this older succession and the Kamiskotia Volcanic Complex rocks to the south. The Kidd-Munro assemblage rocks are coeval with the Kidd Volcanic Complex, which hosts the giant Kidd Creek VMS deposit 30 km to the east of the study area. The lower part of the succession, in south-central Loveland Township, consists of high silica FIIIb rhyolites. These rocks are geochemically similar to ore-associated FIIIb rocks from Kidd Creek and seem likely to represent the most prospective part of this succession. Future exploration in the Kamiskotia Volcanic Complex is probably best focused on the along-strike extension of the VMS-hosting interval and, in particular, on areas close to the intersections of synvolcanic faults. Mafic and felsic volcaniclastic strata which can be replaced by VMS mineralization, and felsic coherent facies flows and/or domes, appear to be important potential targets.
Economic Geology, 1996
Volcanogenie, polymetallic massive sulfide deposits within the Buttle Lake mining camp occur within the felsic volcanic and volcaniclastic rocks of the Myra formation that immediately overlies Price formation andesitc. These units comprise the lower exposed part of the Paleozoic Sicker Group in the Butfie Lake uplift in central Vancouver Island. The Sicker Group represents a volcanic island are that forins the base of the allochthonous Wrangell terrane. The Battle Main zone contains 2.3 million tons (Mr) of proven and probable reserves grading 1.3 g/t Au, 25.3 g/t Ag, 2.5 percent Cu, 0.5 percent Pb, and 13.2 percent Zn. Overall, the Buttie Lake camp hosts geologic reserves of about 12.5 Mr. The Battle Main massive sulfide zone occurs within the H-W horizon, the lowest member of the Myra formation, immediately above the Price formation andesitc. Price formation andesitc is over 300 m thick in the vicinity of the camp and consists of feldspar + pyroxene porphyritic basaltic andesitc flows. Synvo]canic block faulting of this unit formed the regional-scale Butfie Lake camp basin with a strike length of at least 10 kin. Local sub-basins in this major structure contain the sulfides and felsic volcanic rocks of the H-W horizon. The H-W horizon is a 15-to 200-m-thick felsic package that extends throughout the basin. It consists of eight members, three of which represent periods of massive sulfide deposition. From the stratigraphic base to the top of these members are (1)the Battle Main massive sulfide lens, (2) fine rhyolitic tuffaceous deposits, (3) H-W mafic sills, (4) Gap massive sulfide lens, (5) coarse rhyolite pyroelastic deposits, (6) rhyolite tuffaceous and cherry sediments, (7) Battle Upper massive sulfide lenses, and (8) a tripartite rhyolite flow-dome complex consisting of quartz porphyritic rhyolite, quartz-feldspar porphyritic rhyolite, and green quartz-feldspar porphyritic rhyolite. Volcaniclastic units in the felsic package evolved with interfingering of subaerial and submarine pyroelastic processes. Flow-dome units evolved by fractionation of quartz and feldspar. Alteration, evaluated petrographically and with Pearce element ratios, is most intense close to synvolcanic and synmineral feeder faults that channeled solutions through the Price formation andesitc proximal to the Battle Main massive sulfide lens. Envelopes to the feeder faults have distinctive Mg addition anomalies and contain the mineral assemblage pyrite > sericite > quartz > chlorite. Discharge feeder stockworks immediately below the Battle Main massive sulfide lens contain varySng proportions of sericite, quartz, and pyrite but lack significant ohiorite. Deposition of the H-W horizon rhyolitic units on top of the Battle Main massive sulfide lens did not halt mineralization. Rather, fluids continued to percolate upward through the newly deposited rhyolitic units and deposited the Battle Upper lenses close to the new sediment-water interface. Alteration below the Battle Upper lenses consists of quartz, sericite, and pyrite with minor galena, sphalerite, and tennantite. Overall, hydrolysis of feldspar in both the Price formation and the H-W horizon resulted in a halo surrounding the ore lenses marked by addition of K and concomitant Na and Ca depletion. reserves (Pearson, 1993; Westrain Resources Ltd., Annual Report, 1994) are about 12.5 Mt of proven and probable massive sulfide ore grading 2.0 g/t Au, 46.1 g/t Ag, 1.
Middle Tertiary eruptive rocks in the Vancouver area
Early Oligocene mafic volcanic rocks and related intrusions that cut sediments of the Burrard Formation in vancouver are a minor component of the Paleogene Georgia-Bellingharn basin, which straddles the international boundary between British Columbia and Washington State. In the vicinity of Vancouver they occur as flows, breccias, tuffs, dykes, and sills observed in outcrops generally of limited extent, excavations, and boreholes drilled for hydrocarbon exploration or geotechnical purpos€s.