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Ministry of Energy Mines and Responsible for Core Review

Geology and Nobel Metal Geochemistry of the Turnagain Ultramafic Complex
(NTS 104I/7,10)

BCMEMPR Open File 1989-18


by G.T. Nixon, C.H. Ash, J.N. Connelly and G. Case

Scale 1:16 000


View Open File (PDF, 850 KB)


Open File 1989-18 describes he geology and noble metal geochemistry of the Turnagain ultramafic complex (104I/7, 10) in northern British Columbia. The geology map is at 1:16 000 scale and includes a legend and a table of noble metal analyses from various rock types in the ultramafic body. The Open File is a contribution to the Canada/ British Columbia Mineral Development Agreement 1985-1990.

The country rocks include the Upper Proterozoic to Lower Cambrian Atan Formation with argillite, siltstone, minor quartzite and limestone; Paleozoic graphitic slate and phyllite; and Upper Paleozoic metasedimentary and metavolcanic rocks of the Harper Ranch Group.

The Turnagain ultramafic complex is thought to be of Late Triassic age. The Complex consists of dunite; wehrlite with minor dunite, olivine clinopyroxenite, clinopyroxenite and hornblendite; olivine clinopyroxenite; hornblendite and feldspathic hornblendite; and serpentine. Early Jurassic (?) granodiorite bodies cut the older rocks.

The ultramafic body is separated from North American rocks by a reverse or thrust fault. To the west is a major transcurrent fault and rocks of the Harper Ranch Group lie to the west of it. Along the southern contact of the ultramafic body, it apparently intrudes rocks of the Harper Ranch Group.

The ultramafic body has chromite and sulphide occurrences. Net textured sulphide-rich wehrlite-clinopyroxenites yielded locally anomalous values in platinum, palladium and gold.


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