Saskatchewan pipes get a second look

In 1988, Saskatchewan witnessed a preview of today’s diamond rush in the Lac de Gras area of the Northwest Territories. Encouraged by news of a diamond discovery and subsequent land grab by De Beers Consolidated Mines’ subsidiary Monopros on the north shore of Sturgeon Lake, junior and senior companies alike claimed close to two million acres in the wheat fields near Prince Albert, Sask.

Today, although at least 18 kimberlite pipes have been confirmed in the province, some of the main players have cleared out. International Corona (recently acquired by NYSE-listed Homestake Mining), once one of the most active under the leadership of diamond expert Christopher Jennings, abandoned its Saskatchewan program after the diamond-bearing kimberlite discovered on claims shared with Claude Resources (TSE) northwest of Prince Albert proved uneconomic.

Subsequent research led geologists to believe that Corona’s kimberlite find, and possibly Monopros’ previous discovery just two miles to the southeast, were actually large erratics (boulders) transported from their source by ice-age glaciers. This revelation did nothing to encourage further diamond exploration in the province.

But with diamond fever now spreading country-wide, Saskatchewan is regaining some of its former glory. An estimated 600,000 acres of ground has been set aside for this year’s hunt, and a contingent of juniors is reportedly headed for the prairies.

Most of the exploration is confined to the Phanerozoic basin consisting mainly of flat-lying sediments overlying Archean basement rocks. Overburden is generally about 200-300 ft. thick. Faulting and folding within and at the edge of the basin, and zones of crustal weakness in the Archean, formed the conduits needed for kimberlite emplacement during the Cretaceous age. Companies currently active in the area include Cameco (TSE), Uranerz Exploration and Development, Claude, Rhonda Mining (ASE), Aaron Oil (ASE), CopperQuest (CDN) and Currie Rose Resources (VSE). Formation Capital (VSE) recently picked up ground around the play by purchasing Coronation Mines, a private Saskatchewan company. And mining giant Rio Algom (TSE) has reportedly staked close to 60,000 acres just south of the diamond-bearing pipes sampled by Uranerz last year.

Recently listed Rhonda, along with partners Claude and Aaron Oil, has launched “Operation Fish Scale,” a program designed to delineate the marker bed intruded by kimberlite magma about 100 million years ago and, ultimately, to find the source of Corona’s discovery. According to Peter Gummer, president of Rhonda, the abundance of fish skeletons in the sediments suggests that a major event occurred during the Cretaceous that made the waters above Saskatchewan uninhabitable. That event, he suggests, was the eruption of several kimberlite volcanoes.

“We have linked our program to the stratigraphy,” he says. “The fish-scale beds likely represent a major ecological disaster.”

Unlike the Point Lake kimberlite in the Northwest Territories, which appears to have been eroded down to the diatreme zone, Gummer believes that the entire kimberlite system has been preserved from top to bottom in the Saskatchewan bodies. Grounds to support this theory include the bedded nature of the kimberlite occurrences in the area and the donut-shaped magnetic anomalies that define them. These anomalies are characterized by a magnetic low in the middle (representing the center of a Maar volcano), surrounded by a magnetic high (the tuffaceous rim of the volcano).

A producing example of this preserved system is the Orapa mine in Botswana, from which De Beers Consolidated Mines extracted more than six million carats in 1991.

“This kimberlite geology contrasts sharply with the conventional idea that the kimberlite target is a vertical cylindrical pipe,” Gummer says. “The exploration target is actually a stratabound diamond deposit in volcanics and sediments.”

To test its theory, the junior consortium plans to launch a 3-hole drilling program in the black shales several hundred feet up-ice of the Corona discovery. The first hole will test stratigraphy down to a bedrock depth of 300-500 ft. The second hole, collared further north, will probe the rim of a donut anomaly. With the third hole, Rhonda will attempt to intersect a kimberlite neck or pipe at a depth of 1,000-2,000 ft.

“Eventually we are going to find the source of these erratics,” says Gummer. “It has to be there.”

Drilling is scheduled to get under way at the end of September, after the wheat harvest.

Uranerz, in a joint venture with Cameco, is also active near Prince Albert, where it has identified 70 potential pipes. The partners have recently launched a third drilling program to follow-up results of last year’s bulk sample, which yielded a total of 160 macrodiamonds (greater than half a millimetre in diameter) from 15 pipes in the Fort a la Corne region. The diamonds, most of which are gem quality, have an average weight of 0.04 carats and range up to 0.6 carats.

This years program will include more detailed testing on some of the more prospective pipes ranging from 50 acres to more than 150 acres in area, says Uranerz communications manager Roland Loewer. Results are not expected before the end of the year.