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  1. ABSTRACT The abundance of Ru in chromite has been suggested as an indicator of sulfide liquid saturation in komatiites. The komatiite magma-derived Archean Coobina intrusion is known to be barren in terms of sulfide mineralization. Therefore, the Coobina intrusion can serve as a useful case study to test the applicability of Ru abundance in chromite as a potential indicator for sulfide mineralization, as well as for better understanding the PGE-chromite association in general. The Coobina intrusion is a highly deformed layered intrusion interpreted to be a flared dike. It contains multiple massive chromitite seams that have been recently mined for metallurgical-grade chromite. In this study, 18 samples from chromitite seams throughout this intrusion are investigated for their whole-rock platinum group element (PGE) contents, which are compared to their chromite mineral chemistry (including PGE content), the platinum group mineral (PGM) mineralogy, and Re-Os isotope systematics. Each sample has a similar chromite major and minor element chemistry, but a unique trace element signature, even within the same seam. In general, there are higher concentrations of Ru (>300 ppb) within chromite in the southeast (toward the feeder dike) and lower concentrations (<50 ppb Ru) in the northwest. At a sample scale, Ru inmore »the whole rock and Ru in solid solution in the chromite are inversely correlated, while Ir shows a positive correlation between the whole rock and chromite mineral chemistry, indicating differing partitioning behaviors within the iridium-group PGE (IPGE = Os, Ir, Ru). The inverse correlation between Ru in solid solution within chromite and Ru in whole-rock chromitite suggests that, for seams with high Ru in whole rock, Ru is occurring within separate PGM phases. This is supported by the observation that the samples with high whole-rock Ru also have a high number of visible metal alloy and/or PGM inclusions. Although these inclusions are not necessarily Ru-rich phases, their presence suggests that there is a preference for these samples to form nuggets, which may restrict Ru partitioning into the chromite crystal structure. We suggest that the low Ru values in the Coobina chromite are a result of transient sulfide saturation. The Re-Os isotopic composition of the Coobina chromitite is chondritic [γ187Os(3.189 Ga) = −0.63 ± 0.21] and is consistent with derivation of the Coobina parental magma from the convecting upper mantle source, providing evidence for the mantle origin of the Coobina PGE inventory. If using chromite as a detrital indicator mineral for magmatic sulfide exploration, it must be kept in mind that transient sulfide saturation within chromitite seams may give a false positive signature.« less
    Free, publicly-accessible full text available November 1, 2023
  2. On August 4-5, 2022, the Thomas J. O’Keefe Institute for Sustainable Supply of Strategic Minerals at Missouri University of Science and Technology (Missouri S&T) hosted the 2nd annual national workshop on ‘Resilient Supply of Critical Minerals’ funded by the National Science Foundation (NSF). The workshop was convened via Zoom and attracted 346 registrants, including 171 registrants from academia (62 students), 88 registrants from government agencies, and 87 registrants from the private sector. The workshop was free to attend for everyone who registered. On day 1 of the workshop, 152 unique viewers logged into the sessions. Day 2 had 111 unique viewers. Four topical sessions were covered: A. The Critical Mineral Potential of the USA: Evaluation of existing, and exploration for new resources (Day 1). Keynote speaker: Jeffrey Mauk, United States Geological Survey. B. Mineral Processing and Recycling: Maximizing critical mineral recovery from existing production streams (Day 1). Keynote speaker: Karin Olson Hoal, Cornell University. C. Critical Mineral Policies: Toward effective and responsible governance (Day 2). Keynote speaker: Michelle Michot Foss, Rice University’s Baker Institute for Public Policy. D. Resource Sustainability: Ethical and environmentally sustainable supply of critical minerals (Day 2). Keynote speaker: Debra Struhsacker, Professional Geologist, Environmental Permitting & Governmentmore »Relations Consultant. Each topical session was composed of one keynote lecture and three invited presentations. The sessions concluded with a Q/A discussion with all presenters. Recordings of selected presentations are available from the workshop website: The third annual workshop on ‘Resilient Supply of Critical ‘Minerals’ will be held in the summer of 2023 on the Missouri S&T campus, Rolla, Missouri, USA. The dates will be announced in January 2023.« less
  3. On August 2-3, 2021, the Thomas J. O’Keefe Institute for Sustainable Supply of Strategic Minerals at Missouri University of Science and Technology (Missouri S&T) hosted the NSF-funded virtual workshop ‘Resilient Supply of Critical Minerals’. The workshop was convened via Zoom and attracted 158 registrants, including 108 registrants from academia (61 students), 30 registrants from government agencies, and 20 registrants from the private sector. Four topical sessions were covered: A. Mineral Exploration and Source Diversification. B. Supply Chain and Policy Issues. C. Improving Mineral Recycling and Reprocessing Technologies. D. Technological Alternatives to Critical Minerals. Each topical session was composed of two keynote lectures and followed by a breakout session that was designed to identify promising pathways towards increasing critical supply chain resilience in the United States. During each breakout session, participants were asked to address five questions: Q1. What are the roadblocks that affect the resilient supply of critical minerals? Q2. What are the most pressing research needs? Q3. What opportunities can lead to the fastest and biggest impact? Q4. What skills training is required to meet future workforce demands? Q5. What other questions should be asked, but are commonly overlooked? Several issues that limit critical mineral supply chain resilience inmore »the United States were identified and discussed in all breakout sessions, including: 1. Insufficient understanding of domestic critical minerals resources. To address this issue, workshop participants highlighted the need for (i) more geologic research to identify new and evaluate existing resources; and (ii) a qualitative and quantitative assessment of critical minerals that may be recovered as by/co-products from existing production streams. 2. Technical limitations of current mineral processing and recycling technologies. To address this issue, workshop participants highlighted the need for (i) innovative mineral processing technologies, including more environmentally friendly chemicals/solvents, and (ii) automated recycling technologies for appliances and e-waste. Participants also highlighted the need for a centralized and simplified way to collect recyclable materials, and incentives for the public to participate in recycling. 3. Long permitting processes for mining and mineral processing operations, with often unpredictable outcomes. To address this issue, workshop participants suggested the development of new critical mineral focused policies with faster processing times and more transparent / predictable decision-making processes. 4. The negative public image of mining and mineral processing operations. To address this issue, workshop participants suggested to design public outreach / education initiatives and to include local communities into decision-making processes. 5. Limited availability of a critical mineral workforce. To address this issue, workshop participants suggested an increased focus on critical mineral specific skill training in higher education institutions, and advanced training of the existing workforce.« less