Assessing Scheelite As an Ore-deposit Discriminator Using Its Trace-element and REE Chemistry

Research Article| May 30, 2018 Assessing Scheelite As an Ore-deposit Discriminator Using Its Trace-element and REE Chemistry Rémy S. Poulin; Rémy S. Poulin § Harquail School of Earth Sciences, Laurentian University, 935 Ramsey Lake Road, Sudbury, Ontario, P3E 2C6, Canada § Corresponding author e-mail address: remyspoulin@gmail.com, ry_poulin@laurentian.ca Search for other works by this author on: GSW Google Scholar Daniel J. Kontak; Daniel J. Kontak Harquail School of Earth Sciences, Laurentian University, 935 Ramsey Lake Road, Sudbury, Ontario, P3E 2C6, Canada Search for other works by this author on: GSW Google Scholar Andrew McDonald; Andrew McDonald Harquail School of Earth Sciences, Laurentian University, 935 Ramsey Lake Road, Sudbury, Ontario, P3E 2C6, Canada Search for other works by this author on: GSW Google Scholar M. Beth McCLenaghan M. Beth McCLenaghan Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario, K1A 0E8, Canada Search for other works by this author on: GSW Google Scholar The Canadian Mineralogist (2018) 56 (3): 265–302. https://doi.org/10.3749/canmin.1800005 Article history first online: 16 Jul 2018 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Rémy S. Poulin, Daniel J. Kontak, Andrew McDonald, M. Beth McCLenaghan; Assessing Scheelite As an Ore-deposit Discriminator Using Its Trace-element and REE Chemistry. The Canadian Mineralogist 2018;; 56 (3): 265–302. doi: https://doi.org/10.3749/canmin.1800005 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyThe Canadian Mineralogist Search Advanced Search Abstract Scheelite (CaWO4) collected from 37 different ore-deposit settings (orogenic, sediment- and greenstone-hosted, skarn, porphyry, greisen, volcanogenic massive sulfide, breccia, and polymetallic deposits) globally was examined and evaluated using a combination of cathodoluminescence (CL), SEM-EDS, LA-ICP-MS, and δ18O analytical methods. These data provided the basis to assess whether the crystal-chemistry of scheelite could be used to distinguish between differing environments of formation. The results show: (1) scheelite can record very complex growth histories based on CL images and elemental mapping; (2) predominant elemental substitutions involve As5+ or Mo6+ ↔ W6+ and Sr2+ or REE3+ ↔ Ca2+; (3) highly variable trends for the REEs that vary in terms of ΣREEs (below detection to 104 range in CN values), the degree and nature of fractionation (i.e., flat, convex, concave), and the nature of EuN values, which are both positive and negative, with Eu anomalies (EuA) ranging from <0.1 to >20–30; and (4) δ18O values varying from –4.6 to +12.7‰, which apparently do not relate to a deposit-specific fluid signature (δ18OH2O). The variability in REE patterns suggests that many factors affect both ΣREE and incorporation, hence the observed fractionation, into scheelite (e.g., fluid chemistry, coprecipitation of other REE-bearing minerals). Substitutions involving Mo and As are of particular relevance, as both elements are redox sensitive and their enrichment is reflected in ore-deposit settings such that reduced orogenic-type Au-W deposits are As and Mo depleted in contrast to the more oxidized intrusion-related deposits where Mo is enriched (>100 ppm). Similarly, both the EuA values and Sr are relatively enriched in orogenic settings versus intrusion-related settings. These observed chemical differences for Sr, Mo, and EuA in scheelite from different deposit settings were used to construct the first ever discriminant diagram for scheelite, which is summarized in a plot of EuAversus Sr/Mo, which successfully discriminates the samples used in this study. Thus, the crystal-chemistry of scheelite is shown to be both a strong indicator of ore-forming conditions and an ore-deposit discriminator. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.