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SDLRC Blog: Brooke Clements highlights January & February 2018


Sheahan Diamond Literature Reference Compilation
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.

January and February 2018

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 .

Technical Articles
Tectonics
Note: There are nine articles on Archean tectonics that I would like to point out. Four of these are in the recent issue of Geoscience Frontiers which is a free download. Most of the world's primary diamond mines (Argyle being an exception) and most of the world's significant diamond deposits (Buffalo Hills and Fort a La Corne being exceptions) are situated on what are thought to be stable Archean cratons. That is a place where the Archean basement has not been significantly disturbed since the Archean, or at least not disturbed before the diamonds came to the surface in a kimberlite. A big argument amongst geologists has always been about the time when plate tectonic processes started. Some argue it started in the Archean. Others argue that things were different in the Archean and modern tectonic processes started later. This question is addressed in a few of the papers. Each paper has a lot of valuable references. Those developing target areas for diamond exploration need to pay attention to the multiple tectonic models that are out there. There is a lot of great work being done with deep seismic data and I expect that interpretations will evolve in the coming decade.
Stagnant lids and mantle overturns: implications for Archean tectonics, magmagenesis, crust growth, mantle evolution, and the start of plate tectonics. Bedard, 1802-221 Good discussion of Archean tectonics with Canadian examples and good figures. In Geoscience Frontiers.
A planet in transition: the onset of plate tectonics on Earth between 3 and 2 Ga? - Condie, 1802-227 Another good discussion of Archean tectonics addressing the question of when plate tectonics started. In Geoscience Frontiers.
Archean tectonic systems: a view from igneous rocks. - Moyen and Laurent, 1802-254 A geochemical study of igneous rocks that points out differences between Archean and more recent plate tectonics.
Dominant Lid Tectonics behaviour of continental lithosphere in Precambrian times: paleomagnetism confirms prolonged quasi-integrity and absence of supercontinent cycles. - Piper,1802-258 Another Archean tectonics discussion in Geoscience Frontiers.
U-Pb and Lu-Hf isotopes of the Archean orthogneiss complex on eastern Hall Peninsula, southern Baffin Island, Nunavut: identification of exotic Paleo to Mesoarchean crust beneath eastern Hall Peninsula. - From et al., 1802-234 A study of zircons from the bedrock on eastern Hall peninsula on southeastern Baffin Island further confirms the stable Archean cratonic nature of this region where diamonds were found at Chidliak in 2008 by the Peregrine Diamonds team of which I was a member. Prior to the discovery of diamonds there, it was debated whether the basement in this area was stable Archean craton or was comprised of Archean terrane that was significantly "reworked" during the Paleoproterozoic era.
Making Archean cratonic roots by lateral compression: a two stage thickening and stabilization model. - Wang et al., 1801-78 Good discussion of Archean tectonics and cratonization with some good figures. In Tectonophysics.
Do cratons preserve evidence of stagnant lid tectonics? Superior Province. - Wyman, 1802-281 Discussion of Archean tectonics in Geoscience Frontiers using the Superior craton as an example.
Evolution of the Archean crust of the São Francisco craton, eastern Brazil. - Teixara et al., 1801-51 Many of us diamond explorers have spent significant time, mostly without success, trying to figure out where there might be primary sources for the many diamonds that have been found in the rivers of this part of Brazil. This 2017 paper is from a special Springer publication on the geology of the São Francisco craton. There is some renewed interest in diamond exploration in Brazil of late with commercial production of Lipari's Brauna mine commencing in 2017 and significant exploration activity by Five Star Diamonds
Imaging Precambrian lithospheric structure in Zambia using electromagnetic methods. - Sarafian et al., 1802-263 Archean subcontinental lithospheric mantle of the Bangweulu Block in Zambia is defined using magnetotellurics. There has been a lot of diamond exploration in Zambia because of its favorable tectonic setting, principally by DeBeers, but to date, no diamond mines.
Indicator Minerals - Garnets
Statistical approaches to the discrimination of crust and mantle derived low Cr garnet - Major element based methods and their application to diamond exploration. - Hardman et al., 1802-241 A detailed paper on discrimination between crustal and mantle garnets and low-Cr megacrysts for diamond exploration samples. Properly distinguishing between crustal garnets and diamond-friendly and not so diamond-friendly mantle garnets is a critical aspect of any diamond exploration program.
Alluvials
Popa Loimye Arc, correlations with Tibet, and alluvial diamonds in Myanmar. - Mitchell, 1802-253 I was not aware of these alluvial diamond occurrences in Myanmar, another tectonically active area, like Indonesia with mysterious diamond occurences.
Carbonatites
Surface alteration of a melilitite-clan carbonatite and the potential for remote carbonatite detection. - Shavers et al., 1801-66 A successful case study using remote spectroscopy to detect a melilitite-clan carbonatite in the Avon district of Missouri. Melilites are known to carry diamonds, one example being the Anabar craton in Russia. Some people have gone so far as to classify them as "kimberlitic". I undertook one of my first diamond exploration jobs in and around the Avon district of Missouri in the early 80s. I distinctly remember big rattlesnakes, ticks and chiggers. At that time, several of the ultramafic intrusions in this area were classified as kimberlites by some people.
The direct indicator mineral concept and QEMSCAN applied to exploration for carbonatite and carbonatite related ore deposits. QEMSCAN is an integrated automated mineralogy and petrography system that can be used to scan concentrates for indicator minerals quickly. - Simandl et al., 1801-63 QEMSCAM is used to quickly scan heavy mineral concentrates to look for target minerals, with the ability to scan finer fractions than is efficient for the human eye. Exploration companies have looked at and tested this technology, largely I believe without great success. The paper is part of Geological Assoc. of Canada Special Paper 50 Indicator minerals in tills and stream sediments of the Canadian Cordillera.
Kimberlites
Geodynamics of kimberlites on a cooling earth: clues to plate tectonic evolution and deep volatile cycles. - Tappe et al, 1801-70 Good discussion on the deep triggers of kimberlite magmatism and an attempt to explain why most of the world's kimberlites erupted between 250 and 50 million years ago.
A new kimberlite pipe in Balkamthota Vanka, Pennahobilam, Anantapur district, Andhra Pradesh, India - field aspects and preliminary investigations. - Phani, 1801-67 Case study of a new kimberlite outcrop discovery in the Lattavaram kimberlite cluster which now numbers 48. It's interesting that kimberlite outcrops can still be discovered in India.
Media and Corporate Releases
If you listen to the radio in your car, for the last year or so you have been hearing commercials describing "Artisan-made diamonds" that are clean and "ethically" produced, the same as a natural diamond only cheaper etc. Recently I heard a Spence Diamonds commercial describing beautiful pink synthetic diamonds. There has not been a lot of pushback or public response yet by the natural diamond industry to this very aggressive advertising campaign. I note a number of media and corporate items that refer to block-chain technology being developed by DeBeers to trace a diamond from mine to necklace/ring. This could be the beginning of a marketing campaign that would extoll the virtues of natural diamonds vs. synthetic ones. I can't imagine the entire history of a synthetic diamond being as interesting as the life of a natural diamond!

 
 

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