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 is President and CEO of Craton Minerals Ltd., a Vancouver-based private diamond exploration company focused on discovering North America's next diamond district. He is also President of JBC Ventures Ltd., a consulting company specializing in mineral exploration and community and government relations. 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. Before that, Brooke was Vice President, Exploration for Ashton Mining of Canada Inc. Under his leadership, Ashton and their partner SOQUEM discovered the Renard diamond district in Quebec where the Renard Diamond Mine commenced production in 2016. From 1982 to 1997, Brooke was an Exploration Geologist and Regional Manager for Exmin Corporation where he conducted diamond exploration programs throughout the United States. He holds a BSc in Geology from Indiana University and an MSc in Economic Geology from the University of Arizona.
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 .
Seven diamond- and graphite-bearing eclogite xenoliths from Udachnaya were studied. The results suggest that the eclogites are Archean in age (2.5-2.9 Ga) and that they were formed in a depleted mantle source and were not signficantly metasomatized after formation. The carbon istotopes for both carbon and graphite have a narrow range suggesting a mantle source for both. The study provides evidence that graphite can form in the mantle within the diamond stability field and be preserved there for over two billion years.
The Neoproterozoic Brasilia belt overlies the southwestern margin of the Sao Francisco craton in Brazil. 31 mantle xenoliths from three kimberlites, including Canastra 1 were studied and they conclude that "the xenoliths sample the Sao Francisco Craton mantle root, which extends beneath the Brasilia belt, but was modified by reactive transport of the magmas forming the Alto Parnaiba Igneous Province between 120 and 90 Ma." Figure one is a good general map of the Precambrian geology of region.
P-T and oxygen fugacity were estimated for the formation conditions of pyrope garnet inclusions in diamond and pyrope xenocrysts from diamond-bearing and barren kimberlites. It is concluded that the optimal conditions for diamond growth and preservation occur in water-rich mantle fluids containing the lowest abundance of free atomic carbon. The authors conclude that their method "can be used as a more precise mineralogical-petrological method for prospecting for kimberlitic diamond deposits."