Diamond exploration techniques emphasising indicator mineral geochemistry and Canadian examples

The vast Canadian Shield and adjacent areas underlain by cratonic rocks represent a highly prospective geological environment for diamonds. This has recently been demonstrated by the discovery of what appears to be a world-class diamondiferous kimberlite province in the Lac de Gras area of the Northwest Territories. The Lac de Gras discovery, together with others in Saskatchewan, Ontario and Quebec, resulted in a boom in diamond exploration activity in Canada on a massive scale. A brief overview of the petrology of kimberlites and lamproites and the genesis of diamonds is presented before reviewing exploration techniques. Indicator mineral geochemistry was central to the exploration program which led to the discovery of the first kimberlite in the Northwest Territories, and in this report major emphasis is placed on the use of indicator minerals both as pathfinders to kimberlites and as a means of evaluating the diamond potential of exploration targets. Techniques involving the use of both major and trace element geochemistry are evaluated. The indicator mineral geochemistry results from a study of 18 localities investigated in a Geological Survey of Canada funded research project completed in 1989 are discussed. Since conventional indicator mineral techniques are not always applicable to lamproite exploration, alternative pathfinder minerals also have been reviewed.