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On August 9-10, 2023, the Thomas J. O’Keefe Institute for Sustainable Supply of Strategic Minerals at Missouri University of Science and Technology (Missouri S&T) hosted the third annual workshop on ‘Resilient Supply of Critical Minerals’. The workshop was funded by the National Science Foundation (NSF) and was attended by 218 participants. 128 participants attended in-person in the Havener Center on the Missouri S&T campus in Rolla, Missouri, USA. Another 90 participants attended online via Zoom. Fourteen participants (including nine students) received travel support through the NSF grant to attend the conference in Rolla. Additionally, the online participation fee was waived for another six students and early career researchers to attend the workshop virtually. Out of the 218 participants, 190 stated their sectors of employment during registration showing that 87 participants were from academia (32 students), 62 from the private sector and 41 from government agencies. Four topical sessions were covered: A. The Critical Mineral Potential of the USA: Evaluation of existing, and exploration for new resources. B. Mineral Processing and Recycling: Maximizing critical mineral recovery from existing production streams. C. Critical Mineral Policies: Toward effective and responsible governance. D. Resource Sustainability: Ethical and environmentally sustainable supply of critical minerals. Each topical session was composed of two keynote lectures and complemented by oral and poster presentations by the workshop participants. Additionally, a panel discussion with panelists from academia, the private sector and government agencies was held that discussed ‘How to grow the American critical minerals workforce’. The 2023 workshop was followed by a post-workshop field trip to the lead-zinc mining operations of the Doe Run Company in southeast Missouri that was attended by 18 workshop participants from academia (n=10; including 4 students), the private sector (n=4), and government institutions (n=4). Discussions during the workshop led to the following suggestions to increase the domestic supply of critical minerals: (i) Research to better understand the geologic critical mineral potential of the USA, including primary reserves/resources, historic mine wastes, and mineral exploration potential. (ii) Development of novel extraction techniques targeted at the recovery of critical minerals as co-products from existing production streams, mine waste materials, and recyclables. (iii) Faster and more transparent permitting processes for mining and mineral processing operations. (iv) A more environmentally sustainable and ethical approach to mining and mineral processing. (v) Development of a highly skilled critical minerals workforce. This workshop report provides a detailed summary of the workshop discussions and describes a way forward for this workshop series for 2024 and beyond. 

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 in 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. 

Mantle plumes contain heterogenous chemical components and sample variable depths of the mantle, enabling glimpses into the compositional structure of Earth's interior. In this study, we evaluated ocean island basalts (OIB) from nine plume locations to provide a global and systematic assessment of the relationship betweenfO₂and He‐Sr‐Nd‐Pb‐W‐Os isotopic compositions. Ocean island basalts from the Pacific (Austral Islands, Hawaii, Mangaia, Samoa, Pitcairn), Atlantic (Azores, Canary Islands, St. Helena), and Indian Oceans (La Réunion) reveal thatfO₂in OIB is heterogeneous both within and among hotspots. Taken together with previous studies, global OIB have elevated and heterogenousfO₂(average = +0.5 ∆FMQ; 2SD = 1.5) relative to prior estimates of global mid‐ocean ridge basalts (MORB; average = −0.1 ∆FMQ; 2SD = 0.6), though many individual OIB overlap MORB. Specific mantle components, such as HIMU and enriched mantle 2 (EM2), defined by radiogenic Pb and Sr isotopic compositions compared to other OIB, respectively, have distinctly highfO₂based on statistical analysis. ElevatedfO₂in OIB samples of these components is associated with higher whole‐rock CaO/Al₂O₃and olivine CaO content, which may be linked to recycled carbonated oceanic crust. EM1‐type and geochemically depleted OIB are generally not as oxidized, possibly due to limited oxidizing potential of the recycled material in the enriched mantle 1 (EM1) component (e.g., sediment) or lack of recycled materials in geochemically depleted OIB. Despite systematic offset of thefO₂among EM1‐, EM2‐, and HIMU‐type OIB, geochemical indices of lithospheric recycling, such as Sr‐Nd‐Pb‐Os isotopic systems, generally do not correlate withfO₂.

 

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 & Government 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: https://criticalminerals.mst.edu/2022-presentation-videos/. 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. 

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 in 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. 

The lower crustal domain of the Ivrea‐Verbano Zone (NW Italy) hosts five ~300‐m‐wide pipe‐like ultramafic intrusions that are metasomatized and exhibit Ni‐Cu‐PGE sulphide mineralization. To better constrain the role of metasomatism in the ore genesis, we studied the best‐preserved pipe at Valmaggia which was emplaced 249 Myrs ago. Phlogopite⁴⁰Ar/³⁹Ar analyses show that the pipe was infiltrated by metasomatic fluids derived from the subcontinental lithospheric mantle (SCLM) in two pulses at ~208 Ma and ~189 Ma which introduced sulphides into the pipe. Consequently, the pipe repeatedly acted as a preferred path for mass transfer from the SCLM into the lower crust over >60 Myrs (i.e., emplacement to second metasomatic pulse). Uplifted block margins, such as the Ivrea‐Verbano Zone, are potentially important exploration targets for magmatic sulphides. We argue that exploration strategies should focus on structures such as pipes that can focus metasomatic agents during ascent through the lithosphere.