Diamond exploration targets, Michipicoten greenstone belt

CIM Bulletin, Vol. 97, No. 1077, 2004

A.C. Wilson

In 1991, local prospector C. “Mickey” Clement recovered at least three alluvial diamonds from the Michipicoten River. Two of these stones were sent to the Department of Mineralogy, Royal Ontario Museum, where they were identified as industrial-grade diamonds with weights of 1.05 and 1.13 carats. Both stones were described as frosted and graphite-inclusion riddled. In 1995, prospector Sandor Surmacz and geologist Marcelle Hauseux discovered diamonds in bedrock approximately 20 km north of the Michipicoten River. An 18.1 kg bulk sample of a xenolith-rich lamprophyre, taken from an outcrop at the side of the Trans Canada Highway north of Wawa, yielded 1 macro diamond and 5 micro diamonds. All but one was gem quality (Sage, 2000). Since then, more than 36 occurrences of diamonds in bedrock have been reported in an area approximately 30 km2 in size, centred 20 km north of the town of Wawa. The occurrences are hosted within a sequence of unusual, Archean-aged, heterolithic breccias previously considered to have no economic significance. Ten kimberlite occurrences also have been confirmed in the Michipicoten greenstone belt in the last five years. Two of these kimberlites are diamondiferous. To date, expenditures on property acquisition and diamond exploration in the Wawa are estimated at CDN$120 M. This paper summarizes the geological observations made on these occurrences and describes the relationship between the occurrences and the regional geology.

Mots Clés: Exploration, Diamonds, Geochronology, Lithology, Petrography, Wawa.