Alkaline Rocks and Carbonatites of the World

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Mount Copeland

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Occurrence number: 
031-00-030
Country: 
Canada
Region: 
British Columbia
Location: 
Longitude: -118.42, Latitude: 51.12

On the southeast side of the Frenchman's Cap Dome lies a series of nepheline-bearing gneisses complexly folded within a sequence of biotite, diopside and sillimanite schists and gneisses, amphibolites, quartzites and some calc-silicate rocks. The alkaline gneisses comprise three units. A variable syenitic gneiss occurs which is usually silica-saturated, but contains a little altered nepheline here and there, occasional analcime, cancrinite, biotite, aegirine, diopside and hastingsitic amphibole and carbonate, but with dominant K-feldspar. This passes into a unit of alkaline amphibolite and amphibole-biotite schist with nepheline. The third, central zone is a syenite with 15-60% nepheline, usually altered, aegirine (30%), microcline, perthite, and accessory cancrinite, sphene and zircon; locally fluorite and rinkite are significant. Nepheline-bearing lamprophyric dykes occur.

Economic: 
Molybdenite mineralization is persistent at the margins of the syenite, and a small high-grade deposit was mined on the north side of Mount Copeland. A nearby marble horizon has significant Pb-Zn-Ag mineralization.
Age: 
K-Ar on biotite from lamprophyre gave 45 Ma and from syenite 48 Ma. These are probably ages of the matamorphism and not of the formation of the nepheline gneisses (Currie, 1976a, p.177).
References: 
CURRIE, K.L. 1976a. The alkaline rocks of Canada. Bulletin, Geological Survey of Canada, 239: 1-228. FYLES, J.T. 1970. The Jordon River area near Revelstoke, British Columbia. Bulletin, British Columbia Department of Mines and Petroleum Resources, 57: 1-64
Fig. 19 Mount Copeland area (after Currie, 1976b, Fig. 14).
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith