Geoscience Map 1991-3: Geology of the Duncan Area
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Scale 1:50 000
See Paper 1992-4
Geoscience Map 1991-3 portrays the geology of the Duncan area (NTS 092B/13), Vancouver Island British Columbia. This 1:50 000 scale map sheet covers the southwestern end of the Cowichan uplift. The uplift is cored by island-arc volcanics of the Devonian Sicker Group, and associated granodiorite and quartz-porphyry of the Saltspring intrusive suite, overlain by marginal basin and platformal sediments of the Mississippian to Lower Permian Buttle Lake Group. The Paleozoic sequences are intruded by dikes and sills of the late Triassic Mount Hall gabbro, and granodiorite stocks and plutons of the Island intrusive suite. Siliciclastic sediments of the Nanaimo Group overlie older rocks in the Cowichan valley and the coastal areas. The area has been disrupted and deformed by major contractional faults of the Eocene Cowichan fold and thrust system. The map area contains 52 documented mineral deposits and occurrences. The bulk of past production has come from rhodonite and manganese of the Hill 60 area, lode gold of Mount Richards, and various clay and aggregate sources. Other showings consist predominantly of volcanogenic massive sulphides, oxide exhalites and lode gold and copper veins but porphyry copper-molybdenum veins, rhodonite and other industrial minerals are also present within the area.
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