Carbonatite complex. The Oka complex is an elongated oval, double-ring structure 8 km long and 2-3 km wide, trending NW-SE.
It is one of the larger intrusions (approx. age 117-120 Ma) of the Monteregian alkaline province which includes such well known intrusions as Mont Saint-Hilaire. An oval-shaped carbonatite core is enclosed by ring-dykes of ultramafic rocks. It intrudes Precambrian rocks of the Grenville structural province.
The complex was intensely explored in the 1950s and significant deposits of niobium were found. There are a number of individual localities within the complex, which were explored by a number of mining interests, but only one mine, the St. Lawrence Columbium mine, has gone into production.
References:
GOLD, D.P. (1963) The relationship between the limestones and the alkaline igneous rocks of Oka and St. Hilaire, Quebec. Ph.D. Thesis, McGill University, Montreal. 354 p.
GOLD, D.P. (1967) Alkaline ultrabasic rocks in the Montreal area, Quebec. In: Ultramafic and Related Rocks, edited by P.J. Wyllie, 288-302. Robert E. Krieger Publ.Co. 464 p.
GOLD, D.P. (1969) The Oka carbonatite and alkaline complex. Guidebook GAC/MAC Annual meeting 1969, 43-62.
SABINA, A.P. (1968), revised (1983) Rocks and Minerals for the collector. Kingston, Ontario to Lac St-Jean, Quebec. Geological Survey of Canada paper 67-51 (1968), Misc. Report No. 32 (1983), 46-49.
Mariano, A. N., 1985. The paragenesis of the Bond Zone of the Oka Carbonatite Complex, Oka, Quebec. Senior Thesis, Bucknell Univ., Lewisburg, Pennsylvania.
Mariano, A. N., Roeder, P. L., 1989. Wöhlerite: chemical composition, cathodoluminescence and environment of crystallization. Canadian Mineralogist, 27: 709-720.
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Map Reference: 45°30'N , 74°3'W
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