Whole Rock Geochemistry and X-ray Diffraction Mineralogy Measurements of Select Mafic and Ultramafic Units in the United States

This data release presents whole rock geochemical data and powder X-ray diffraction (XRD) mineralogic data from a suite of mafic and ultramafic geologic units in the United States. One-hundred-twelve samples were analyzed from core and outcrop settings at thirty sites, including from the contiguous United States, Alaska, and Hawaii. Sample localities include some of the large mafic and ultramafic structures in the United States that have been previously identified as targets for CO₂ mineralization (Blondes and others, 2019) and may hold potential for associated critical mineral recovery (e.g. Ni and Co). Sites were classified into 20 site groups based on common geologic origins or spatial proximity. All samples were analyzed for whole rock geochemistry by Activation Laboratories LTD (ActLabs, analysis codes 4B2 and 4F-S). Reported whole rock geochemical data of samples include contents for 55 major to trace elements measured via inductively coupled plasma-mass spectrometry (ICP-MS) analyses, as well as total sulfur content measured via infrared analyses and loss on ignition (LOI) values measured via gravimetric analyses. In some samples, Cr (n=6) and Ni contents (n=1) contents exceeded detection limits of the analysis. A subset of samples (n=51) was also analyzed for XRD at Pacific Northwest National Laboratories (PNNL). This subset was selected to ensure one or more samples were analyzed for XRD at each site. Quantitative mineralogy data are reported from Rietveld refinement of the XRD data, following standard methodologies of PNNL (Jacobs and others, 2025). Sites were further delineated by their lithology class (mafic versus ultramafic) and common lithology. For XRD-measurements, generalized lithologies were assigned to samples based on igneous textures, abundance of alteration products, and ultramafic ternary diagram classifications. These samples were measured in a collaboration between PNNL, the U.S. Geological Survey, and the Natural Resources Research Institute as part of the Supercritical CO₂ Based Mining for Critical Mineral Recovery project. This project was funded by the Mining Innovations for Negative Emissions Resources (MINER) program funded by the Advanced Research Projects Agency—Energy (ARPA-E) of the U.S. Department of Energy. Cited references: Blondes, M.S., Merrill, M.D., Anderson, S.T., and DeVera, C.A., 2019, Carbon dioxide mineralization feasibility in the United States: U.S. Geological Survey Scientific Investigations Report 2018–5079, 29 p., https://doi.org/10.3133/sir20185079. Jacobs, J.E., Stanfield, C.H., Miller, Q.R., Villante, M.A., Marcial, J., Nienhuis, E.T., Silverstein, J.A., Polites, E.G., Bartels, M.F., Gooch, B.T. and Liu, J., 2025. Technoeconomic Potential for Carbon Mineralization with Enhanced Recovery of Critical Minerals in the Pacific Northwest. ACS Sustainable Resource Management, 2(5), pp.775-785, https://doi.org/10.1021/acssusresmgt.4c00541.

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