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Tuesday, November 15, 2011

Gold Occurrences in the Northwest Territory of Canada

The NWT of Canada

Some of the oldest rocks on Earth are the Acasta Gneiss found in the Northwest Territory of Canada.  The rock itself is metamorphosed sedimentary rock that is far older then its radiometric date of 3.8 billion years.  A zircon found in this rock has been dated as 4.03 billion years old.  These rocks of the Acasta formation are by far the oldest rocks discovered in North America, and were originally laid down in the Hadean era.

A fragment of the Acasta Gneiss on display in the Natural History Museum in Vienna.
Photo by Pedro Alexandrade

Unlike the Yukon that lies to the west of the NWT that has no exposed rock of the Canadian Shield most of the territory is composed of rocks of the shield.  These rocks display plenty of greenstone belts notably the Yellowknife Greenstone Belt near Great Slave Lake.

Gold was discovered in the territory in 1898, but active mining did not commence until the mid 1930s in the area around Yellowknife. The opportunities for additional exploration and prospecting in the territory abound. There are other valuable mineral deposits that are being worked in the territory including uranium and the recent discoveries of diamonds have resulted from the opening of diamond mines.

Yellowknife, NWT in the mid 20th century.
Photo by YK Times

A vast amount of information is available through the Northwest Territory’s Geoscience Office in Yellowknife. Another source of information is the Prospectors and Developers Association of Canada (PDAC) in Toronto, Ontario. The Northern Miner in Toronto is a weekly newspaper covering the mining industry worldwide including the Northwest Territory.

Prospecting for Gold the Northwest Territories of Canada along with many other valuable minerals including copper, diamonds and uranium is a viable occupation. Parts of the territory along the Arctic coast and on the islands in the Arctic Ocean contain gas and oil. A few years ago a geologist inadvertently published the locations of test wells on Ellsmere Island and received a proper wigging for his efforts. The territory depends on mining for most of its economy. Today however the emphasis is on diamonds rather then gold.

A significant gold discovery has recently been announced at the REN gold site. The gold was discovered in a seven kilometer long iron formation. Gold is often associated with iron especially with the ore granular magnetite. Some of the grab samples of ore collected have as much as 198 g/t of gold. In follow-up drilling more gold was found in the host rocks adjacent to the gold rich body of iron ore.  The area around Yellowknife is dominated by the Yellowknife Greenstone Belt that has been the scene of several past and present gold mines.

Over the years there have been a number of gold mines found in the area around Yellowknife the territory’s capitol. This city was originally settled as a gold camp and became the capitol later. The diamond mining industry is now centered Yellowknife although the actual mines are located to the Northeast of the city around the Lac de Gras area.

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