Location: Kerby Centre, 1133 – 7 Ave SW, Calgary, AB, Lecture Room 205. Please check in at the Reception Desk and they will direct you to Room 205. If you are using the Kerby Centre parking lot, you can validate your parking at the same time.
Use of Automated Mineralogy in Geochemical Modeling of Mineralogies of the Bear Lodge REE Deposit, northeast Wyoming, USA
Dr. Adrian Van Rythoven, P.Geo.
Development of deposits that were previously avoided due to complex mineralogies and resulting processing issues is becoming increasingly commonplace as material demands increase and new analytical and processing techniques develop. Many rare earth element (REE) deposits under current evaluation by exploration and development companies are the result of multiple geochemical processes that result in mineral assemblages with different REE grades, REE distributions, and/or amenabilities to economic recovery.
The Eocene Bear Lodge complex contains a series of carbonatite dykes and associated stockworks that intrude slightly older trachyte/phonolite stocks and diatremes. Post magmatic hypogene, and especially supergene alteration processes have significantly altered ore and gangue mineralogies. Fenitization, REE remobilization, oxidation, carbonate dissolution, and clay alteration are all processes that contributed to an economically attractive, but heterogeneous deposit.
The use of geochemical indices, audited for accuracy by independent analytical methods, can be an extremely useful tool for quantifying information of mineralization/alteration across a deposit given complete and accurate assays. Simple geological logging of drilled core or chips cannot always provide information that can be easily used in deposit model generation. However, for geochemical indices to be effective, assumptions made during their construction must be calibrated by modal mineralogical data. Optical microscopic, XRD, and QEMSCAN/MLA data can all be used to audit the accuracy of such normative indices.
The establishment of these indices using a foundation of relatively costly mineralogical analyses on a small, representative subset of samples allows for the low-cost estimation and modeling of ore and gangue mineralogy across a deposit. Reasonably accurate estimates of mineralogical assemblages can then be resolved spatially using 3D modeling software. The resulting semi-quantitative characterization of deposit mineralogy can be of great use in resolving issues related to mineral processing, exploration, environmental characterization, and engineering.
Geochemical indices that attempt to quantify parameters including clay alteration, silicification, oxidation, and proportions of phosphate mineralization have been developed for the Bear Lodge. Given the highly variable nature of the mineralogies in a partially laterized deposit and the assumptions made, most indices have been found to be in reasonable agreement with modes observed using QEMSCAN, XRD, SEM, cathodoluminescence, and optical microscopy.
Adrian is originally from Burlington, Ontario. He found an interest in geology during his many summers as a child poking around the glacial till deposits by his family’s cottage. He obtained his degrees in geology from the University of Toronto, focusing on kimberlite and diamond. During that time he also worked for De Beers Canada, the Ontario Geological Survey, and as a mineralogy consultant. After grad school Adrian worked for almost four years as a mineralogist for Rare Element Resources in Wyoming on the Bear Lodge rare earths and gold project. Most recently, he was an assistant professor on a year-long contract at Mount Royal University. He is now again a mineralogy consultant with Applied Petrographics. He is also a licensed professional geoscientist in Alberta and Ontario.
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