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The geology of Kinskuch Lake area, British Columbia Gale, Robert Earle

Abstract

Kinskuch Lake area covers a fifty-square mile portion of the Portland Canal district of western British Columbia. Kinskuch Lake lies near the eastern border of the Coast Mountains, approximately twelve miles north of the port of Alice Arm. Reconnaissance mapping of the area on a scale of 1" = 1000’ was done during part of the summer of 1956. Rock specimens collected in the field were examined microscopically and the results of the latter investigation form the greater part of this thesis. The interbedded volcanic and sedimentary rocks of Kinskuch Lake area were deposited during the period of Mesozoic volcanism and sedimentation which was widespread throughout western British Columbia and southeastern Alaska. Near Kinskuch Lake, the earliest products of Mesozoic volcanism are represented by augite porphyry volcanic breccias, crystal tuffs, flows and flow breccias outcropping along the western margin of the map area. Augitic volcanics are overlain to the east by interfingering felsitic breccias and tuffs, sedimentary rocks and greenstone. East of Kinskuch Lake, the latter rocks pass gradationally into a thick overlying sequence of felsitic volcanic breccia, crystal tuffs and feldspar porphyry flows. The youngest rocks outcrop near the eastern margin of the map area. Here, argillites and conglomerates overlie felsitic volcanic breccia and interbedded tuff. The Mesozoic volcanic and sedimentary rocks were folded, faulted and intruded by keratophyric and lamprophyric dykes. As a last stage in the geological sequence of events, volcanic rocks at the southeast corner of Kinskuch Lake were altered and mineralized. Highly fractured or sheared greenstone and felsitic volcanics were altered to chlorite, pyrite, epidote, sericite quartz and calcite. Minor chalcopyrite mineralization accompanied rock alteration and many small quartz-carbonate veins cut the altered rocks. Some of the latter veins carry pyrite, chalcopyrite and traces of sphalerite and galena. Albitization of some of the igneous rocks outside the altered zone accompanied the widespread carbonate alteration.

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