GEOLOGICAL ASSESSMENT OF ULTRAMAFIC AND MAFIC ROCKS IN VIRGINIA: PROSPECTS FOR CRITICAL MINERAL EXTRACTION AND CARBON MINERALIZATION

Ultramafic and mafic rocks are often enriched in nickel and cobalt, both of which are considered critical mineral commodities. Beyond the resource potential for supplying critical minerals, ultramafic and mafic rocks also contain abundant iron- and magnesium-bearing minerals that have garnered attention for their importance in carbon mineralization – a process by which carbon dioxide is naturally sequestered and immobilized within stable mineral forms such as calcite, dolomite and siderite.

Virginia hosts a remarkable abundance of ultramafic and mafic rocks, including 1) ultramafic rocks from the Albemarle-Nelson Soapstone Belt, 2) mafic metabasalt in the Blue Ridge geologic province; and 3) ultramafic komatiite, metabasalt, and diabase rocks in the Piedmont geologic province. Geologists from Virginia Energy, in collaboration with Virginia Tech, are conducting a comprehensive investigation of the geological and geochemical characteristics of the ultramafic and mafic rocks in Virginia, to evaluate their potential for carbon mineralization and critical mineral extraction (CMME). Field and archived samples are being characterized by petrographic mineralogical examinations and preliminary geochemical screenings are performed using portable X-ray fluorescence (PXRF) instrumentation. Selected samples have been sent to commercial laboratories and Virginia Tech for whole rock plus trace element, quantitative mineralogical, and CMME analyses.

The selection criteria for samples designated for CMME testing involve a target content of 0.1% nickel (~1000 ppm) and 0.01% cobalt (~100 ppm) by weight. Preliminary results from PXRF analysis indicate an elevated nickel concentration within most ultramafic samples that exceed the established threshold, reaching up to ~5400 ppm. Cobalt concentrations are also elevated, reaching up to ~600 ppm. Microscopic examination reveals the presence of minerals known to contain nickel and cobalt, such as olivine and serpentine. To date, elevated concentrations of critical minerals that meet the minimum threshold have not been observed in the mafic rock data. The results from laboratory geochemical analysis are compared with the results from our initial PXRF scanning.