Open File 2001-18 describes the geology of the southern McConnell Range and Sustut River areas (94D/3,7,9,10,15,16) in central British Columbia. The coloured 1:50 000 scale geological map includes a legend, fossil references, references, and a list of mineral occurrences.

The oldest stratified rocks in the area are cherty mudstone, felsic to mafic volcanics, limestone and shale of the Early Permian Asitka Group. Unconformably overlying Late Triassic Takla Group rocks are subdivided into four formations. The Dewar Formation consists of epiclastic sandstone, siltstone and mudstone. Lower Savage Mountain units are: basalt porphyry, pillow basalt flows, pillow breccia, and feldspar and/or augite phyric basalt. Upper Savage Mountain units are andesitic bladed feldspar porphyry, and lithic tuff aprons that may be associated with vent breccia. Moosevale Formation units are marine siltstone, lithic tuff and submarine slide breccia, the middle sandy unit, the upper semi-stratified breccia and lahar conglomerate, conglomerate and sandstone, and undifferentiated breccias. Early Jurassic Hazelton Group contains the Telkwa and Nilkitkwa Formations. Telkwa Formation units are polymictic conglomerate, feldspar porphyry breccia with sandstone, mudstone and tuff interlayers, red and lapilli tuffs with andesite flows, andesitic to dacitic flows with welded tuffs and sediments, and undifferentiated andesitic to dacitic volcanics. The Nilkitkwa Formation is represented by argillite, siltstone and tuff with minor limestone and volcanic interlayers. Middle to Late Jurassic Bowser Lake Group sediments are conglomeratic sandstone, siltstone, carbonaceous claystone and coal. The Late Cretaceous Sustut Group has basal quartz-bearing conglomerate, mudstone and coal overlain by pebbly sandstone and mudstone.

Intrusive rocks in the area are of Late Triassic and Early Jurassic age. The Late Triassic suite includes the Menard complex, with clinopyroxenite, gabbro and diorite; subvolcanic dacitic to andesitic porphyry intrusions; and augite porphyry. Early Jurassic intrusions include rhyolite porphyry, gabbro, monzodiorites and dacite porphyries, and the Black Lake intrusive suite with stock to batholithic granodiorite to diorite to monzogranite phases.

The map pattern is dominated by faults with trends that vary from northeast to north to northwest. Offset of geologic units indicates both strike-slip and vertical offset.

Mineral occurrences copper with or without precious metals but some have associated lead, zinc or molybdenum. The most important occurrence known is the Sustut volcanic redbed copper deposit in Late Triassic semi-stratified breccia and lahar conglomerate host rocks. The area also has potential for porphyry copper +/- molybdenum +/- gold deposits and skarns.
 

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Last updated November 16, 2007