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 .
A free download and a very good summary of all the scientific details related to diamond dating. Geochronologists use inclusions trapped in the diamonds to date them. The age of the inclusion tells you how long it has been trapped in the diamond and thus the minimum time of diamond formation. Diamond dating is destructive and most gem diamonds don't have inclusions so diamond dates are obtained from a small subset of diamonds. Isotopic compositions for multiple inclusions are required to get an isochron to determine an age, so most diamond ages for a deposit are calculated from multiple stones within the deposit. The oldest known diamonds are from Ekati and Diavik at 3.5-3.3 billion years. The recent determination of an age of 720 million years for diamonds from the Victor mine in Ontario has caused some exploration geologists to rethink some long-held diamond exploration paradigms.
East-dipping subduction has been proposed by some researchers as the trigger for Cretaceous kimberlite/lamproite magmatism along a trend stretching from Somerset Island in the north and Arkansas to the south, and Cordilleran magmatism in western North America. The authors of this paper propose that the Cretaceous kimberlite magmatism and Mesozoic Cordilleran magmatism was triggered by west-dipping subduction of the North American lithosphere underneath the Cordillera. They suggest that the kimberlite/lamproite magmatism could have been triggered by extensional stress associated with that west-dipping subduction.
Researchers have suggested that the Archean mantle was hotter than today's mantle which has an estimated temperature of about 1350 degrees C. Estimates of the Archean mantle range from 1500-1600 degrees. Modelling in this paper postulates that a cooler Archean mantle, as low as 1450 degrees, is a better fit for what we observe in Archean crustal rocks.
In late 2018 the largest diamond ever recovered in North America was found at the Diavik mine. The previous record was 271 carats from Victor. The diamond is Type 1A with a high nitrogen content. There is a nice GIA video of the diamond in this free download