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Diamond Deposits Of The North American Craton –An Overview
Diamonds have been found in placers in North America derived from unknown sources. Others were recovered from glacial deposits from distant lands. The number of placer diamonds found in North America indicates that several source deposits would be discovered.
Some discoveries initially led to developments of small mines in Murfreesburo, Arkansas (Prairie Creek) and the Colorado-Wyoming State Line district (Kelsey Lake). However, world-class diamond deposits have eluded the United States to date, but have now been found in Canada that led that nation to becoming a major source of gem-quality diamonds over a very short period of time. Canada now ranks as the third largest producer of gem-quality diamonds in the world, which followed the development of their first mine (Ekati) in 1998 and second mine (Diavik) a few years later. A third mine was recently dedicated (Jericho) and two additional mines are under development –all world-class deposits! With thousands of additional discoveries, other diamond mines will be developed in the future. The timing of this diamond boom and rush occurred at a promising time, when major diamond mines in Africa, Australia and Russia were showing declining production.
Even though favorable Cratonic (Archon) basement rocks extend south of Canada under large portions of the United States, essentially all meaningful exploration has been confined to Canada over the past 25 years. Reports of hundreds of diamonds along with hundreds of kimberlitic indicator mineral anomalies, kimberlites, lamproites, lamprophyres and some distinct geophysical anomalies in the US, lead one to anticipate that exploration could result in significant discoveries in the US.
The favorable Cratonic terrains in Canada that are host for some very impressive diamondiferous kimberlites do not stop at the Canadian border but continue southward into the Great Lakes region (Superior Province) and into Wyoming and Montana (Wyoming Province). One should anticipate that major swarms of mantle-derived intrusives continue southward into Montana, Wyoming, Colorado, Michigan, and Wisconsin, and that this terrain could potentially become an important source for diamonds in the future.
This craton and cratonized margin has been intruded by widespread swarms of these mantle-derived magmas. The North American craton is predicted to become the principal source of gem and industrial quality diamonds in the near future and for decades to come.
This paper is dedicated to the memory of three wonderful friends and geologists; John Dooley, Ray Harris and Robert Lyman. It is difficult to lose a friend so early in life, but three in their prime!
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