Ontario paves way for base metals exploration

Hosting one of the biggest volcanogenic massive sulphide deposits (Kidd Creek) in the country, Ontario is hoping base metals exploration will pick up after a presentation at a recent mines and minerals symposium in Toronto. The last time there was a concerted effort to find base metals deposits in Ontario was in the 1952-1970 period. But in the years since then, geological thinking in the province has changed significantly. The recognition of several new felsic volcanic packages, together with booming base metals prices, could once again spur exploration for these metals.

Speaking before an audience of about 500, five members of the Ontario Geological Survey (OGS) briefly reviewed the regional, camp and deposit-scale tools needed for successful base metals exploration in the province.

“With these tools in mind, you can now re-dedicate yourself to the fascinating job of finding more base metals deposits,” geologist R. M. Easton said.

High-precision airborne electromagnetic survey data now covers about 30% of the provinces greenstone belts. Potential underestimated

There are at least nine felsic volcanic areas in the province (outside the present and former base metals camps) where the potential for finding new base metals deposits “may have been underestimated,” according to OGS geologist Andy Fyon.

The Temagami greenstone belt, stretching from Temagami in the east to Hwy 144 in the west, is one such area which was emphasized in the OGS presentation. Chemically, a felsic pyroclastic unit on the north limb of the Tetapaga syncline displays a rare earth element pattern similar to that of other felsic volcanic rocks known to be associated with massive sulphide mineralization, Fyon pointed out. In addition, alteration in Strathy and Cassels twps. appear to correspond to significant sulphide occurrences.

“Given the volcanology and chemical data, we might be drawn to that part of the volcanic stratigraphy which contains the felsic subaqueous pyroclastic flows, such as in the Boot Bay area,” Fyon said. The belt is host to the Temagami copper mine, a former producer. Another past producer, the Geneva Lake mine, is located further to the west.

Other areas of the province where revisions have been made to understanding of the geology in recent years in favor of base metals exploration include:

the boundary between the English River and Wabigoon subprovinces where several felsic rock units have not (until now) been widely recognized as being volcanic in origin;

the Little Marshall Lake belt, north-northeast of Lake Nipigon, where rocks, originally interpreted as being sedimentary, have recently been reinterpreted to consist in large part of felsic volcanic deposits (recent work by Giant Gripp Mines, a wholly-owned subsidiary of N.W.T. Copper Mines, suggests cumulative tonnage of about two million tons grading 4% zinc and 1% copper);

the western Lake St. Joseph area where a fourth, uppermost volcanic cycle consisting of voluminous pyroclastic material has recently been recognized;

the upper Windigo greenstone belt, 150 km northwest of Pickle Lake, where a rock unit, originally thought to be an epiclastic metasedimentary rock, has been reinterpreted to be a dacitic pyroclastic unit;

the North Onaman River Belt where felsic deposits occur as two thin units in the centre of the belt (mineralization on the Headway- Coulee property in the area assays 4% zinc and 2% lead);

the Lower Detour Lake area where drill-hole results indicate a large volume of felsic volcanic rocks under the extensive overburden that blankets the area; and,

the Grenville Province where exploration could be guided by a New Calumet and Montauban-type model.

Base metals deposits are three times more expensive to find in Ontario than are gold deposits, according to Brian Mackenzie of the Centre for Resource Studies in Kingston, Ont., but the rewards are five times larger. He presented the conclusions of his study, “Mineral Exploration and Mine Development Potential in Ontario,” at the same symposium.

“If it wasn’t for the Kidd Creek deposit, Ontario would be a marginally prospective area to search for economic deposits,” Mackenzie said. “But it is this deposit (one of 39 discoveries in the 1946-85 period that Mackenzie studied) that makes it a very good place to look for base metals.”