ASSESSMENT OF GEOLOGICAL AND GEOCHEMICAL FACTORS ASSOCIATED WITH OCCURRENCES OF CRITICAL MINERALS IN VIRGINIA

Virginia’s state geological survey is collaborating with the USGS Earth Mapping Resources Initiative (Earth MRI) to better understand the potential for domestic sources of 35 identified “critical minerals”. Many of these mineral commodities have extensive histories of past production and/or exploration in Virginia. State archives contain numerous reports, maps, and geochemical and geophysical data that document occurrences of aluminum, arsenic, barite, manganese, tin, titanium, tungsten, uranium, zirconium, among other commodities. Economic criteria for many of these have changed, yet the full nature and extent of geological resources will remain uncertain without applications of modern exploration technologies. Geological mapping at the 1:24,000 scale provides essential baseline information to interpret the nature of mineral deposition systems, yet is only about 33% complete in Virginia. Those areas lacking the necessary geological map and geophysical data coverage are prioritized for startup as funding opportunities become available.

For many of the critical commodities, there are geological and geochemical factors that provide valuable guidance for future exploration. For example, heavy mineral sands containing titanium and zirconium were concentrated in Virginia’s coastal plain sediments as a result of transgressive-regressive events in the late Pliocene and early Pleistocene epochs; deposits of barite and manganese occur as stratiform replacements in carbonate rocks in the Valley and Ridge; tungsten and tin deposits are closely associated with greisen-altered granodiorites in the Piedmont and Blue Ridge; enrichments of rare earth elements (REEs) may occur in weathered residuum derived from granitic rocks in Virginia’s Piedmont and Blue Ridge. Through collaboration with Earth MRI, we are assessing the natural variability of geochemical concentrations of the critical commodities in potential host rocks and producing mineral prospectivity maps using a geographic information system (GIS) approach. This will lead to a better understanding of important mineralization processes, identification of mineral associations that may have been previously unrecognized, and identification of mineralized provinces with the potential for undiscovered resources.