Geoscience Map 2011-03: Geology, Geochronology, Lithogeochemistry and Metamorphism of the Mahatta Creek Area, Northern Vancouver Island (NTS 092L/05) 1:50 000 scale
View Geoscience Map 2011-3 (PDF, 4.1 MB)
Geoscience Map 2011-3 (1:50 000-scale) is the third 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 2011-3 describes the geology, geochronology, lithogeochemistry and metamorphism of the Mahatta Creek area (NTS 092L/05). 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. Of note stratigraphically is the radical change in thickness of the Late Triassic Quatsino limestone across the Mahatta Creek area from the west coast (~40 m thick) to the east (Neroutsos Inlet >900 m). A young Tertiary (Neogene) granodiorite, the Klaskish River Pluton, which is the founding member of the Late Miocene – Early Pliocene Klaskish Plutonic Suite, intrudes Late Triassic Karmutsen and Early Jurassic Bonanza (Le Mare Lake unit) volcanic rocks near the foot of the Brooks Peninsula. Recent exploration at the northern margin of this pluton has targeted a Cu-Mo porphyry system similar to mineralization at the former Island Copper mine hosted by a Middle Jurassic intrusion of the Island Plutonic Suite. Major northwesterly-trending faults with inferred vertical and/or stike-slip offsets occupy drift-filled valleys subparallel to the coast and appear to repeat Bonanza Group stratigraphy. One such fault system, the Le Mare Lake - Red Stripe Mountain faults, has demonstrably displaced stratigraphic units about 5 kilometres in a right-lateral sense. These structures are intersected by a set of steeply-dipping, northeasterly-trending, subparallel faults comprising the Brooks Peninsula Fault Zone, one of which (the Klaskish River Fault) cuts the Late Miocene Klaskish River Pluton. 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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