Lac de Gras

Lac de Gras. It is a large glacial lake located approximately 300 kilometers northeast of Yellowknife in the Northwest Territories of Canada. The lake is part of the drainage basin for the Coppermine River, which eventually flows into the Arctic Ocean. Its name, French for "Lake of Fat," is believed to refer to the greasy consistency of its water when frozen, a characteristic noted by early fur traders.

Geography

Lac de Gras lies within the Canadian Shield, a vast geological region characterized by Precambrian rock. The lake's surface sits at an elevation of approximately 396 meters above sea level and it covers an area of about 569 square kilometers. Its shoreline is highly irregular, dotted with numerous islands and inlets, a typical feature of glacially scoured landscapes. The primary outflow is to the north via the Coppermine River, a designated Canadian Heritage River system. The surrounding terrain consists of barren-ground tundra and taiga, with a climate classified as subarctic, featuring long, severe winters and short, cool summers. Key nearby geographical features include the Lac de Gras kimberlite field and the Snap Lake area.

Geology

The region surrounding Lac de Gras is geologically renowned for its kimberlite pipes, the primary source rock for diamonds. These volcanic pipes intruded through the ancient Archean granite and gneiss of the Slave Craton during the Cretaceous period. The discovery of these kimberlites in the early 1990s, notably by geologists like Chuck Fipke and Stewart Blusson, triggered a major mineral exploration rush. The Lac de Gras kimberlite field contains several economically significant pipes, including those at the Ekati and Diavik operations. The geology is also marked by prominent eskers and drumlins, glacial landforms left by the retreat of the Laurentide Ice Sheet.

History

The area has been part of the traditional lands of Indigenous groups, including the Tłı̨chǫ (Dogrib) and Yellowknives Dene. European presence began with explorers and fur traders associated with the Hudson's Bay Company and the North West Company in the 18th and 19th centuries. The modern era of history is dominated by the diamond rush of the 1990s, following the confirmation of diamond-bearing kimberlite by De Beers and other prospectors. This led to the staking of massive mining claims and the eventual development of major mines, fundamentally transforming the remote region. The settlement of Ekati, established to support the mine, became a focal point of this industrial activity.

Diamond mining

Lac de Gras is the epicenter of Canada's diamond mining industry. The Ekati Diamond Mine, owned by Dominion Diamond Mines, was the first to begin production in 1998. It was soon followed by the Diavik Diamond Mine, a joint venture between Rio Tinto and Dominion Diamond Mines, which opened in 2003. These mines extract ore from multiple kimberlite pipes located both under the lake and on its shores, requiring the construction of massive dikes for open-pit and underground operations. The Gahcho Kué Mine, another major operation southeast of the lake operated by De Beers and Mountain Province Diamonds, further cemented the region's global significance. The mines operate under stringent environmental agreements, including the Mackenzie Valley Resource Management Act.

Ecology

The lacustrine ecosystem of Lac de Gras supports species adapted to cold, nutrient-poor waters, such as lake trout and Arctic grayling. The surrounding tundra provides critical habitat for migratory species like the barren-ground caribou of the Bathurst caribou herd. Predators including wolves, grizzly bears, and Arctic foxes are present. The area is also a breeding ground for various bird species, including loons, Arctic terns, and peregrine falcons. Mining operations are required to conduct extensive environmental monitoring under frameworks like the Environmental Impact Assessment process to mitigate impacts on water quality, fish habitat, and wildlife migration corridors. The region falls within the Taiga Shield ecozone.

Category:Lakes of the Northwest Territories Category:Diamond mining in Canada