EXPLORATION & DISCOVERY: DIAMONDS SPARK EXPLORATION; Were it

In 1991, Canadian exploration expenditures totalled $532 million, down from $775 million in 1990. Senior companies spent $416 million and junior companies $116 million. Some 732 operators reported exploration projects in 1991, down from 936 companies in 1990. Planned exploration expenditures for 1992, gathered from companies early that year were $498 million, but actual expenditures may have been as low as $450 million. After adjustment for inflation, Canadian mineral exploration expenditures in 1991 and 1992 were the lowest since the mid-1970s. They are not expected to increase in 1993.

Of the $532 million spent on exploration in Canada in 1991, $67 million was spent on the search for new deposits on the properties of existing mines.

Quebec, British Columbia and Ontario accounted for 72% of total Canadian mineral exploration expenditures. Compared with 1990, exploration expenditures dropped in all provinces and territories: by 59% in Nova Scotia, 48% in Newfoundland, 40% in British Columbia, 38% in Alberta, 30% in Quebec, 28% in Ontario, 28% in Manitoba, 25% in Saskatchewan, 12% in Northwest Territories, 10% in Yukon and 4% in New Brunswick.

Exploration expenditures for precious metals (nearly all for gold) accounted for 52% of the Canadian total, down from 60% in 1990. Those for base metals accounted for 40%, up from 31% a year earlier. The amount of surface exploration diamond drilling declined to 1,861,998 metres from 2,953,626 metres in 1990.

Diamond exploration

and discoveries

The discovery of diamonds in kimberlite pipes in Canada was the Canadian exploration highlight of 1992. A number of gemstone-quality, diamond-bearing kimberlite pipes of possible economic grade were discovered in the Northwest Territories. (See “Diamonds” review by M. Boucher in the Industrial Minerals section).

There have been various previous indications that economic diamond deposits might exist in Canada. Diamonds have been found in glacial overburden in the Great Lakes area of the United States. A diamond of about 33 carats, but broken and of little value as a gem, was found near Peterborough, Ont., prior to 1920. A second diamond of about 0.255 carats was found in an esker near Timmins, Ont., by Reno Jarvi. This diamond is of gemstone quality, and is housed in the Royal Ontario Museum. The sources of these two diamonds have yet to be discovered.

Kimberlite intrusions containing microdiamonds of no economic significance were found some years ago on Somerset Island, N.W.T.; near Kirkland Lake, Ont.; in Quebec and elsewhere. In 1988, exploration turned up at least several dozen kimberlite pipes intruding post-Precambrian rocks in Saskatchewan. At least 15 of these were reported to contain diamonds, most of them microdiamonds. Several of the intrusions have yielded 160 larger macrodiamonds, most of them gem quality. However, these are apparently all small diamonds. The average diamond content of all the pipes is less than 10 carats per 100 tonnes, too low to be economic.

Following the discovery of diamond-bearing kimberlite pipes in Saskatchewan, diamond exploration soon spread to Alberta and the Northwest Territories. The significant diamond discovery was made in 1991 by BHP Minerals and Dia Met Minerals at Point Lake, in the Lac de Gras area, about 200 km. northwest of Yellowknife, N.W.T. A 145-t sample taken by drilling into one kimberlite pipe on the property yielded 101 carats of diamonds, one quarter of which appear to be of gem quality. A few of them are 1-3 carats in size. The surface area of the pipe appears to be about 20 hectares. Much larger bulk samples will have to be tested before it is known whether the deposit is mineable. Subsequently, a stock exchange listing report stated that a kimberlite resource of 73 million tonnes grading 69 carats per 100 tonnes had been outlined to a depth of 220 metres. In December, it was announced that core and surface sampling of nine new kimberlite pipes all contained macrodiamonds. At least six of those new pipes are as large or larger than the Point Lake kimberlite.

Several microdiamonds were also reported in November from kimberlite intrusions about 15 km southeast of Point Lake on a property owned by other companies. Kimberlite intrusions are reported on various other properties in the Point Lake area.

The Point Lake discoveries led to unprecedented staking in the Northwest Territories, where some 7.2 million hectares had reportedly been staked, up from 2.2 million hectares in 1991 and 356,000 hectares in 1990. In Alberta, a December staking rush covered 22.4 million hectares, more than one-third of the area of the province.

Active diamond exploration was also reported in northeastern British Columbia; near Kirkland Lake; in the James Bay lowlands and elsewhere in Ontario; near Snow Lake, Man.; and in northwestern Quebec.

The Federal-Provincial exploration survey reported $7.7 million of diamond exploration expenditures in 1990 and $7.0 million in 1991. The survey for 1992 will undoubtedly report much increased expenditures on diamond exploration.