Russian geologist sheds new light on diamond exploration

Companies exploring for diamonds in Canada are too focused on heavy mineral sampling, says Galina Kudrjavtseva, a professor of mineralogy at Moscow State University who specializes in kimberlites.

Speaking in Toronto recently alongside Australian diamond expert Bram Janse, Kudrjavtseva said those who hope to delineate diamond-bearing kimberlites should consider not only heavy minerals such as pyrope garnets and chrome diopsides within potentially diamond-bearing xenoliths, but also the common minerals that make up the kimberlitic groundmass. “We should think more about the minerals that crystallized from the kimberlite melt,” she told a meeting sponsored by the Canadian Institute of Mining, Metallurgy and Petroleum’s Economics Society. “We are working in very difficult conditions, so we should think of other, cheaper ways of exploring.” Most of the work in the Lac de Gras region of the Northwest Territories has involved finding heavy minerals and tracing them back to source. “Chuck Fipke worked hard, but he also had a lot of luck,” Janse said. “He is lucky that the Slave province is similar to the Kaapvaal province in South Africa, where pyrope garnets, chrome diopsides and illmenites are easy to find.”

Kudrjavtseva said heavy minerals are almost as rare as diamonds in the pipes of the new Arkhangelsk field north of Saint Petersburg in Russia. There, geologists have had to rely on other exploration methods — including groundmass analysis and finely tuned geophysics — to determine the diamond-bearing potential of the 150 pipes, five of which are economic, found since 1979.

She is currently examining samples from the C-14 and Bucke Twp. kimberlite pipes near Kirkland Lake, Ont., which have both yielded macrodiamonds for previous owners but have low concentrations of heavy minerals. She says that groundmass geochemistry suggests two pipes have “good potential” to host economic deposits.

KWG Resources (ME) holds the Bucke pipe and is optioning the C-14 pipe in Clifford Twp., Ont., from Regal Goldfields (CDN).

Chrome spinels and iron isotope ratios, for instance, tell a story about the speed of crystallization and the depth of the kimberlite chamber. Kimberlite that cooled quickly and originated below a certain point in the earth’s mantle is more likely to be diamond-bearing.

Groundmass analysis is also cheaper than heavy mineral analysis because it requires much smaller samples, Kudrjavtseva pointed out.