CRITICAL MINERAL COMMODITY OCCURRENCES IN VIRGINIA – AN ASSESSMENT OF PROSPECTIVE GEOLOGIC AND GEOCHEMICAL FACTORS

In response to intensified efforts to better understand the potential for domestic sources of “critical minerals”, geoscientists at Virginia’s geological survey have begun a new assessment of the 35 identified mineral commodities in collaboration with the USGS Earth Mapping Resources Initiative (Earth MRI). In Virginia, many of the targeted commodities, including aluminum, arsenic, barite, manganese, tin, titanium, tungsten, uranium and zirconium have extensive histories of past production and/or exploration. Our archives contain numerous reports, maps, geochemical and geophysical data that document these activities. In most of these cases, modern exploration technologies have not been applied and the full nature and extent of geological resources remains uncertain. Geological mapping at the 1:24,000 scale is about 30% complete in Virginia, providing essential baseline information to interpret the nature of mineral deposition systems in many areas. Those areas lacking the needed geologic map and geophysical data coverage are prioritized for startup as funding opportunities become available.

For many of the critical commodities that have potential in Virginia, there are known geologic factors that can provide valuable guidance for future exploration and resource development. Examples include the alluvial and marine heavy mineral sand deposits that contain titanium and zirconium; enrichments of rare earth elements (REEs) in weathered residuum derived from granitic rocks; beryllium, tantalum, niobium, and lithium in pegmatite deposits in the eastern Piedmont; tungsten and tin occurrences associated with greisen-altered granodiorites in the Piedmont and Blue Ridge; and deposits of barite and manganese that occur as stratiform replacements in carbonate rocks in the Valley and Ridge. Through the 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 were previously unrecognized, and identification of mineralized provinces with the potential for undiscovered resources.