Geoscience Map 2011-02: Geology, Geochronology, Lithogeochemistry and Metamorphism of the Quatsino-Port McNeill Area, Northern Vancouver Island (NTS 092L/11, and parts of 092L/05, 12 and 13) 1:50 000 scale
View Geoscience Map 2011-2 (PDF, 4.3 MB)
Geoscience Map 2011-2 (1:50 000-scale) is the second in a series of five new geological maps (Geoscience Maps 2011-1 to 2011-5) of northern Vancouver Island which together provide a revised Early Mesozoic stratigraphic framework and Mesozoic-Tertiary plutonic history for southern Wrangellia. Geoscience Map 2011-2 describes the geology, geochronology, lithogeochemistry and metamorphism of the Quatsino – Port McNeill area (NTS 092L/11 and parts of 092L/05, 12 and 13). The map area is underlain by a folded and faulted sequence of Late Triassic to Middle Jurassic volcanic and sedimentary rocks of the Vancouver and Bonanza groups intruded by granitoids of the Early to Middle Jurassic Island Plutonic Suite. The deformed Triassic-Jurassic rocks are unconformably overlain by Cretaceous marine clastics and cut locally by Tertiary dikes and minor intrusions. Middle Jurassic intrusions of the Island Plutonic Suite (e.g. Rupert Inlet Pluton) are spatially and genetically associated with important calc-alkaline Cu-Au-Mo porphyry-style mineralization at the former Island Copper mine, as well as coeval high-sulphidation, base- and precious-metal epithermal prospects hosted by rhyolitic flows and pyroclastic rocks in the Pemberton Hills – Mount McIntosh area to the west (Geoscience Map 2011-1).
Intriguingly, a dyke similar to the one associated with mineralization at Island Copper extends over 5 km east of the Rupert Inlet Pluton beneath a thick cover of glacial drift, as inferred from geophysical surveys, and remains to be drill-tested. A major, westerly-trending fault zone, the Holberg Fault, exposed in cliffs on the headland between Rupert and Holberg inlets, separates well-mineralized, Middle Jurassic intrusions and the largely coeval Holberg volcanic unit of the Bonanza Group from their Early Jurassic counterparts to the south. Radical changes in lowermost Jurassic stratigraphy are also evident across this structural corridor: a thick, predominantly subaerial, volcanic-volcaniclastic sequence (Le Mare Lake volcanic unit) south of the Holberg Fault largely correlates with a more condensed succession of intercalated, marine sedimentary and volcaniclastic strata north of the fault zone (Nahwitti River siltstone-wacke unit and lower part of the overlying Holberg volcanic unit). In the eastern part of the area, outliers of Neogene Alert Bay volcanic rocks rest unconformably on a downdropped block of Upper Cretaceous sedimentary strata of the Nanaimo Group. Regional metamorphism is generally characterized by very low-grade mineral assemblages (prehnite-pumpellyite to zeolite facies) except in the vicinity of faults and intrusive contacts where the rocks may reach upper greenschist to amphibolite grade, respectively.
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