The Sheahan Diamond Literature Reference Compilation is compiled by Patricia Sheahan who publishes on a monthly basis a list of new scientific articles related to diamonds as well as media coverage and corporate announcements called the Sheahan Diamond Literature Service that is distributed as a free pdf to a list of followers. Pat has kindly agreed to allow her work to be made available as an online digital resource at Kaiser Research Online so that a broader community interested in diamonds and related geology can benefit. The SDLRC Blog is a guest commentary by an industry expert about articles, themes and trends in recent issues of the SDLRC.
Comments by Brooke Clements
Brooke Clements received a B.Sc in Geology from Indiana University and an M.Sc in Economic Geology from the University of Arizona. From 1982 to 1997, he was an Exploration Geologist and Regional Manager for Exmin Corporation where he conducted diamond exploration programs throughout the United States. From 1998 to 2007 he was Vice President, Exploration for Ashton Mining of Canada Inc. Under his leadership, the Ashton-SOQUEM exploration team discovered the Renard diamond district in Quebec where Stornoway Diamonds opened the Renard Diamond Mine in 2016. From 2007 to 2015 he was President of Peregrine Diamonds Ltd. where he led the team that discovered the Chidliak diamond district on Baffin Island in the Canadian Arctic. Currently, Brooke is President of JBC Ventures Ltd., a consulting company specializing in mineral exploration and community and government relations. He is also President and CEO of Craton Minerals Ltd., a private diamond exploration company focused on discovering North America's next new diamond district.
Brooke Clements has volunteered to highlight the scientific articles that caught his attention in the monthly reference compilations. The opinions expressed are solely his and he can be reached at .
Southern Superior Craton: Over the last five years or so, the southern Superior craton, north of Lake Superior has seen a resurgence in diamond exploration activity. Players include: De Beers Canada, Kennecott, Churchill Diamonds (private) and well-known Ontario prospector Rudy Wahl. De Beers announced the discovery of five kimberlites in the area at the IKC in September 2017. Kennecott has been active in the area for a long time and have discovered at least one diamondiferous dyke. Churchill Diamonds has also been exploring the area and recently optioned a property from Kennecott. Three items from Pat's May compilation have direct or indirect application to this area: Aulbach et al., Brett and McDannell et al. So far, the "kimberlites" just north of the big lake do not have economic diamond content and the Midcontinent rift event, 1.1 billion years ago has received a lot of the blame. Brett suggests that the mantle under Kennecott's diamondiferous "Rabbit Foot occurrence" was "good" when it was emplaced around 1.9 billion years ago, but the lithosphere was thinned by subsequent Mid-Continent rift activity about 1.1 billion years ago. At the IKC in September 2017, those of us not in the research loop uttered a collective "wow" when Thomas Stachel presented a paper postulating the age of the diamonds at the Victor Mine are 720 million years. Aulbach et al. suggest that the mantle under the mine was negatively altered by the Midcontinent rift, but "quickly" healed by 700 million years ago to allow the diamonds to form that made their way to the surface with the Victor kimberlite eruption.
De Beers' Victor Diamond Mine in the lowlands of northern Ontario hosts an exceptional population of very high value diamonds, possibly the highest "run of mine" value production from any mine in the world. An age of approximatey 720 million years is suggested for these diamonds. This is a real eye opener as most diamonds in the world are thought to be much older. This implies a young diamond formation event after the Mid-continent rift which is thought to have disrupted the area around 1.1 billion years ago. There are very interesting implications for diamond exploration from this revelation. How long does the lithosphere need to be stable for diamonds to be formed, do you need "stable" Archean craton for diamond formation, etc., etc.
Information presented in this Vancouver talk was also presented at the Sept. 2017 IKC in a poster. Brett suggests the lithosphere under their Rabbit Foot occurrence was diamond-friendly 1.9 billion years ago but events associated with the 1.1 billion year-old Midcontinent rift have rendered it not so friendly.
This study uses the thermal history of the Superior craton and adjacent areas to determine the cratonic stability. The Midcontinent rift, in the Lake Superior region is a prominent player in the story.
Optimum processing efficiency is different for each diamond deposit. You have to strike a balance between recovering as many of the big diamonds as you can while still being efficient and cost-effective. You need to understand if your deposit has a lot of big, high value stones, to determine your optimum processing circuit. This paper discusses using size frequency distribution (SFD) analysis to determine the optimum cut-off and re-crush sizes and the use of XRT (x-ray transmission) technology in the processing flow sheet at diamond mines.
Stiefenhofer presented this paper at the IKC in September, 2017. The De Beers crew presents a good tutorial, with real examples from their mines, on using microdiamond results to estimate commercial diamond grades. This is a very topical subject as those with advanced diamond projects are always seeking the most efficient and cost-effective methods to define their diamond resources.