Diamonds In Canada

CIM Bulletin, Vol. 71, No. 798, 1978

J. J. Drummer, Exploration Manager, Minerals Division, Canadian Occidental Petroleum Ltd., Rexdale, Ontario

The possibility of diamonds occurring in Canada was first raised by W. H. Hobbs in 1899, who concluded:"that the apex of the fan of diamond distribution probably lies somewhere in the strip of the territory bordering James Bay on the east."This was based on the occurrence of diamonds in surflcial sediments at various locations south of the Great Lakes.There are two recorded discoveries of drift diamonds in Ontario: (a) the Peterborough Diamond, 33 carats in size, poorly documented and found sometime before 1920; and (b) the Jar-vi Diamond, 0.255 carat, found during 1971 in Sheraton Township near Timmins. Both discoveries were in surflcial sediments and their source(s) have not been located.During 1960, Selco Exploration Company Ltd. started a heavy-mineral sample program of river gravels in the James Bay Lowlands of Ontario. This was continued by Canadian Rock Company Ltd. (1962-1963) and the Ontario Division of Mines (1973). The surveys discovered the presence of kimberlite minerals in gravel samples from streams draining the Moose River Basin. A total of 53 pyrope grains, four magnesian ilmenites and one grain of chrome diopside were identified from 32 sample locations. A study of the distribution of these minerals suggested the kimberlite source rocks to be located along the north margin or within the Kapuskasing gravity "high" in the area immediately south of James Bay. The Jarvi Diamond, found on an esker east of Timmins, could well have originated from this area.During 1965, an esker was sampled by the Geological Survey of Canada, and the results attracted attention to the area south of Lake Abitibi. At 9 out of 34 sites sampled along the Munro esker, Lee recorded the presence of pyrope garnets and very minor chrome diopside. The subsequent search for the source of the kimberlite minerals resulted in the discovery, during 1968, of a 3-foot-wide dyke of kimberlite on the 2750-ft level of the Upper Canada Mine in Gauthier Twp., Ontario. Earlier work by Satterly had recorded the intersection of two thin (6-in.) kimberlite dykes in drill holes in Michaud Township, Ontario. The author does not consider these two occurrences to be the only sources of the pyrope garnets detected. He considers that there are other undiscovered kimberlites present in the general area which contributed pyrope to the esker samples. The logical areas to search would be along rift valleys with associated carbonatites in the area north of Arnold Twp., Ontario.The three kimberlitic occurrences mapped on lie Bizard, 9 miles west of Montreal, form part of the Monteregian Hills. One of the three occurrences, the Pain de Sucre diatreme, yielded ten microscopic diamonds, the largest being 0.0244 carat in size, as the result of sampling completed by Canadian Rock Company Ltd. during 1968. This is the first bedrock diamond discovery made in Canada.Collerson has recorded the occurrence of kimberlitic diatremes and dykes near Saglek on the northeast coast of Labrador. He considers their emplacement to be related to the early formation of the Labrador Sea.Recent work by Diapros Canada Ltd. and Cominco Ltd. on Somerset Island resulted in the discovery of at least 19 kimberlite occurrences during 1973-1974. One of these, the Batty Pipe, covers an area of about 95 acres, which compares favourably with other pipes recorded elsewhere. A "few small diamonds" were recovered by Diapros from bulk samples collected from the Batty, Elwin and Diapros pipes during 1974 and 1975. Emplacement of the Somerset Island kimberlites appears to be controlled by continental rifting associated with opening of the North Atlantic, which commenced during Cretaceous times (80 m.y.) and is still active.Prospecting for kimberlites in the Canadian Arctic is much simpler and more rewarding than similar efforts in the forested drift-covered areas of southern Canada.Since Hobbs first suggested (1899) the possibility of diamonds occurring in Canada, a considerable amount of work has been done since 1960. This has since accelerated with the discovery of the Somerset Island kimberlites and recognition of the association of kimberlites with rift structures in the Arctic and elsewhere. The search for diamonds is still in progress and results will eventually be published when the discoverers are ready to do so.
Keywords: Diamonds, Economic geology, Peterborough Diamond, Jarvi Diamond, Kimberlites, Glacial drift, James Bay Lowlands, He Bizard, Labrador, Somerset Island, Rift structures, Carbonatites.