MARINE MINERAL RESOURCES ON THE CONTINENTAL SHELF OFFSHORE OF VIRGINIA: NEW INSIGHTS CONCERNING ECONOMIC HEAVY MINERALS

Since the mid-1980s, the Virginia Department of Mines, Minerals and Energy has collaborated with the U.S. Bureau of Ocean Energy Management (BOEM) to assess occurrences of economic heavy minerals on the continental shelf offshore of Virginia. These include mineral sands containing economic and critical commodities such as titanium, zirconium, cesium, rare earth elements, among others. Following the impacts of Hurricane Sandy, the offshore cooperative work with BOEM was expanded to include an assessment of sand deposits suitable for beach replenishment and coastal restoration projects. New geophysical data and sediment cores collected as part of this ongoing work have benefited both objectives, aiding stratigraphic correlations, the interpretation of paleo-drainage channels, volumetric estimates of sand resources, and providing marine sediments for additional textural and heavy minerals analyses.

To date, mineral concentrates from over 620 sediment samples have been analyzed for total heavy mineral (THM) content, with 17 percent containing >5 percent THM, and 2 percent containing >10 percent THM. Ongoing studies are examining the spatial distribution, textural characteristics, provenance and transport pathways using factor analysis and detrital zircon geochronology, and the economic mineral fractions primarily as the sum percent of ilmenite, leucoxene, rutile, monazite, apatite, sillimanite, and zircon.

Preliminary volumetric estimates of beach-quality sand resources indicate 32 million cubic yards in a shoal deposit offshore of Sandbridge Beach, and 19 million cubic yards of sand in deposits offshore of Wallops Island to a depth of five feet below the sea floor. These deposits occur in primarily Holocene-age sand shoals, sheets, and paleo-channel infill deposits above fluvial and estuarine sediments of Pleistocene age. Additional data collection is needed to assess the full extent of these and other identified deposits.