Geology and Mineral Occurrences in North Newcombe Lake Map SheetBCMEMPR Open File 1989-01
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Open File map 1989-01 presents the geology and mineral occurrences of the North Newcombe Lake map sheet, NTS 093E/14 in the Interior Plateau of central British Columbia. The mapping was a contribution to the Canada/British Columbia Mineral Development Agreement, 1985-1990. Lithogeochemical assay data, moss mat geochemical and stream sediment geochemical results are tabulated.
The oldest rocks in the area are Lower Jurassic Telkwa Formation of the Hazelton Group. These consists predominantly of andesitic flows; ash, lapilli and accretionary lapilli tuffs; and rhyolite flows. The overlying Middle Jurassic Smithers Formation of the Hazelton Group consists of siltstone, arkosic sandstone and granule pebble conglomerate. The Ashman Formation of the Middle Jurassic Bowser Lake Group is also sedimentary, consisting of argillite, sandstone and minor sandstone.
The Lower Cretaceous Skeena Group has an older volcanic division and a younger sedimentary division. Andesitic flows of the lower division are commonly porphyritic and often amygdaloidal. Phenocrysts are plagioclase and pyroxene. Siltstone, argillite and micaceous sandstone comprise the sedimentary division. The Upper Cretaceous Kasalka Group also has volcanic and sedimentary components. Andesitic flows give way upward to basaltic flows and toward the top there are intraformational conglomerate beds with cobbles of volcanic rock and pink granite.
The Eocene Ootsa Lake Group consists of rhyolite flows and polymictic conglomerate with andesite and rhyolite clasts.
Quaternary alluvium and glacial till mantle much of the map area; outcrop is not abundant.
Many of the mineral occurrences are granite-related types: molybdenum mineralization in biotite monzonite, disseminated chalcopyrite and molybdenite in quartz monzonite porphyries or altered Lower Jurassic volcanic rocks, and stockwork quartz veins carrying chalcopyrite in granodiorites and adjacent hornfelsed Telkwa Formation volcanics. Other occurrences are in altered volcanic rocks with no clear tie to plutonic activity, such as disseminated magnetite and hematite in chlorite and epidote altered Telkwa andesite. Extensive Quaternary cover has hampered mineral exploration in the area.
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