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Geology of the Aiken Lake map-area, British Columbia Roots, Ernest Frederick

Abstract

Aiken Lake map-area lies in the Cassiar District of north-central British Colombia between 56°00' and 57°00’ north and longitudes 125°00' and 126°00' west. It is a relatively rugged, glaciated area lying almost entirely within the Omineca-Cassiar Mountain System. The oldest rocks within the map-area are quartz-mica schists, garnetiferous schists and quartzites of probable Proterozoic age conformably overlain by Lower Cambrian chlorite schists, slates, quartzites, and limestones. A relatively large area of these Proterozoic and Cambrian rocks has been further metamorphosed to feldspathized quartzite and gneiss. A total of nearly 30,000 feet of interbedded volcanic pyroclastic and true sedimentary rocks ranging in age from Devonian or Mississippian to Upper Triassic outcrops in a broad belt across the central part of the map-area. These rocks are intruded by dykes, sills, stocks, and batholiths of Upper Jurassio or Lower Cretaceous age. The intrusive bodies range from granite to pyroxenite in composition, granodiorite being the dominant rock type. A body of conglomerate at least 5500 feet thick of probably Lower Cretaceous age, containing many pebbles of intrusive rocks, is faulted into Triassic or Upper Palaeozoic rocks. The Proterozoic and Lower Cambrian rocks have been folded, apparently during their period of metamorphism, into large anticlinoria. The planes of schistosity of the metamorphosed rocks lie approximately parallel to the limbs and to the crests of the anticlinoria. The grade of regional metamorphism of these rocks increases uniformly as lower stratigraphic horizons are reached. Known mineral deposits within the area are almost entirely confined to the Lower Cambrian and Proterozoic schists and limestones, or to the aureoles of the Jurassic-Cretaceous igneous bodies. Those in the Lower Cambrian and Proterozoic rocks are typically of the lead-zinc-silver type. Many of these mineral occurrences have no known association with igneous rocks. The deposits found within the aureoles of the Jurassic-Cretaceous igneous bodies have characteristic gold-quartz, gold-copper, or copper-lead mineralization.

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