Geoscience

Industrial Minerals

Deposits and Occurrences - Precambrian

Diamonds

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Outcrop photograph of pelletal lapilli (arrows) from the diamondiferous polymictic conglomerate, Knee Lake.
Outcrop photograph of pelletal lapilli (arrows) from the diamondiferous polymictic conglomerate, Knee Lake.

 

In 2016, bedrock mapping and sampling by the Manitoba Geological Survey resulted in the discovery of diamonds in the Oxford Lake–Knee Lake greenstone belt of the Superior craton, representing the first confirmed occurrence of diamonds in Manitoba.

The diamonds are hosted by Archean sedimentary rocks that may have been derived from coeval lamprophyric volcanism.

Through its surficial geology program, the Manitoba Geological Survey continues to support diamond exploration by providing practical guides to drift prospecting. Results of this work are available at www.manitoba.ca/iem/geo/surficial/


Outcrop photograph of pelletal lapilli (arrows) from the diamondiferous polymictic conglomerate, Knee Lake.

 

Kimberlite-indicator Minerals

Sampling of surficial sediments in parts of Manitoba has revealed a wide range of kimberlite-indicator mineral (KIM) suites, with promising results in the Hudson Bay Lowlands, the northern Superior province, and at Southern Indian Lake in the Trans-Hudson orogen. Among the indicator minerals are garnets of G10 composition (low Ca, high Cr; potentially derived from diamond-forming regions in the mantle), which were found in till samples from the northern Superior province and from areas underlain by Mesozoic bedrock in the south. KIM sampling programs are ongoing in several parts of the province to expand and improve the data coverage.

More detailed information, including public domain KIM data and an integrated anomaly map designed for kimberlite exploration, is available at www.manitoba.ca/iem/geo/kimdata

 

Suggested references:

Mineral Commodities in Manitoba: Diamonds

Anderson, S.D. 2016: Alkaline rocks at Oxford Lake and Knee Lake, northwestern Superior province, Manitoba (NTS 53L13, 14, 15): preliminary results of new bedrock mapping and lithogeochemistry; in Report of Activities 2016,
Manitoba Growth, Enterprise and Trade, Manitoba Geological Survey, p. 16–27.

Open File OF2017-3
Preliminary geology of the diamond occurrence at southern Knee Lake, Oxford Lake–Knee Lake greenstone belt, Manitoba (NTS 53L15)
By S.D. Anderson

NTS Map

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