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File Created: 15-Jan-1992 by Jennifer W. Pell (JP)
Last Edit:  23-May-2023 by Nicole Barlow (NB)

Summary Help Help

NMI
Name PHOSPHATE Mining Division Cariboo, Liard
BCGS Map 093I019
Status Showing NTS Map 093I01W
Latitude 054º 10' 50'' UTM 10 (NAD 83)
Longitude 120º 16' 15'' Northing 6007051
Easting 678099
Commodities Phosphate Deposit Types F07 : Upwelling-type phosphate
Tectonic Belt Foreland Terrane Ancestral North America
Capsule Geology

The Phosphate showing is located approximately 98 kilometres north of McBride (Highway 16) and 163 kilometres east-northeast of Prince George. It is 21 kilometres west of the British Columbia–Alberta border, in the Liard Mining Division.

The region is underlain by an assemblage of sedimentary rocks that were deposited in a continental shelf environment along the western margin of Ancestral North America. This clastic and carbonate rock sequence ranges in age from Hadrynian to Upper Cretaceous and now lies within the Foreland tectonostratigraphic division of the Canadian Cordillera. Folds and southwest-dipping, northeast-directed thrust faults are the dominant structures of the region.

At the kilometre scale, shallow- and potentially doubly-plunging folds, as well as thrust panels, juxtapose three units relevant to the phosphorite showing: the Mississippian Rundle Group (limestones, marbles, calcareous sediments); the Carboniferous to Permian Stoddart, Fantasque and Kindle formations (undivided sedimentary rocks) and the Triassic Sulphur Mountain Formation of the Spray River Group.

The occurrence area plots on the southwest limbs of two northeast-trending folds that expose these three units in succession, with the youngest Sulphur Mountain Formation at the fold core.

Phosphorite horizons are known from upper Paleozoic and lower Mesozoic strata in the region. At this site, phosphorite beds are present in the Whistler Member of the Lower Triassic Sulphur Mountain Formation (Spray River Group) and occur near the core of a syncline. The phosphatic horizon at this location is 10 to 15 centimetres thick and is exposed in a rubbly outcrop associated with calcareous siltstones and silty limestones. The phosphorite is dark grey or bluish to white-weathering, with a dark brown to black fresh surface. It has a gritty texture, a petroliferous odor and contains abundant ammonite and pelecypod fossils. Purple fluorite is present as veinlet infillings and fracture coatings. Grab samples of these phosphorites contained 21 to 23 per cent phosphorus pentaoxide (Fieldwork 1991, page 79).

Bibliography
EMPR FIELDWORK 1991, pp. 65-82, 83-91
EMPR OF 1992-10

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