Preliminary Bedrock Geology and Lake Sediment Geochemistry of the Northern Kechika Trough (NTS 94L/14,15; 94M/3,4,5,6,12,13; 104P/8,9,15,16)
BCMEMPR Open File 1997-14
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Open File 1997-14 presents the preliminary geology of the Northern Kechika Trough (94L/14, 15; 94M/3, 4, 5, 6, 12, 13; 104P/8, 9, 15, 16) in northeastern British Columbia. The Open File portrays geology at 1:100 000 scale, a legend, a geological cross section, references, and lithogeochemical assay data on sheet 1. Sheet 2 provides lake sediment geochemical analysis results and a sample location map.
The area is underlain by rocks of ancestral North American affinity and rocks of the Cassiar terrane. Cassiar terrane rocks range in age from Upper Proterozoic (?) to Paleozoic. They consist of quartz-feldspar sandstone and phyllite that may be Ingenika Group; dolomitic siltstone, cherty siltstone, siltstone and chert; silty limestone to calcareous siltstone; and quartz sandstone and slate.
Two informal units are of uncertain age. In the Upper Proterozoic (?) to Lower Paleozoic Aeroplane Lake panel, low-grade metamorphic rocks predominate. Three map units are mainly: limestone, phyllite and sandstone; siliceous schist and quartz sandstone; and calcareous phyllite and schist. The Kitza Creek facies consists mostly of carbonaceous siltstone to silty argillite and shaly slate associated with fetid limestone.
The oldest North American rocks are slate, phyllite, argillite and siltstone with interbedded micaceous sandstone, quartzite, and conglomerate that comprise the Proterozoic Hyland Group. One unit consists of undivided Upper Proterozoic and Cambrian rocks that include Hyland Group and younger strata. Upper Cambrian to Lower Ordovician Kechika Group strata include a siliceous facies that is mainly siltstone and fine sandstone with slate, and silty limestone or dolostone interbeds, and more normal assemblage of laminated slate, calcareous slate, and limestone. Locally Kechika and lower Road River strata are undifferentiated. Upper Ordovician to Middle Devonian Road River Group has a lower recessive part with mostly shale to slate and argillite, and an upper part that is characterized by the ‘Silurian Siltstone’ unit. This consists mainly of buff-brown to orange weathering siltstone and dolomitic siltstone with slate or argillite interbeds. Upper Devonian to Mississippian Earn Group rocks are predominantly argillite, cherty argillite, siltstone and slate; bedded barite is rare. Mississippian to Permian Mount Christie Formation strata are dominated by chert with minor argillite interbeds. Tertiary or Quaternary Tuya Formation basalts are massive to fragmental.
The oldest intrusive rocks in the area are Early Paleozoic (?) gabbro bodies. Early Cretaceous intrusions form sill, dikes and small stocks on Boya Hill. Biotite-feldspar and quartz porphyry predominate. Cretaceous (?) porphyries occur in or near the Aeroplane Lake panel. Granite with small quartz phenocrysts is of Late Cretaceous to Early Tertiary (?) age.
The strata are deformed into upright folds and cut by high angle east-directed thrust faults.
The area has potential for Sedex zinc-lead-silver deposits, barite deposits and tungsten, molybdenum and base metal porphyry or skarn mineralization is known. Placer gold has been reported.
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