ECONOMIC HEAVY MINERALS IN SAND RESOURCES OFFSHORE OF VIRGINIA

Over the last 40 years, mineralogic studies covering dynamic marine environments on the inner and outer continental shelf (OCS) offshore of Virginia have demonstrated the presence of economically valuable critical commodities such as titanium, zirconium, and rare earth elements contained in heavy mineral sands. Total heavy mineral (THM) concentrations ranging from less than 1% to ~15% by weight (wt%) in over 600 legacy offshore grab and core samples reflect complex depositional settings influenced by paleo-drainage transport from upland source areas and modern ocean seafloor and current dynamics.

Forty-five new samples were collected from vibracores provided by Schnabel Engineering within the Atlantic federal navigation channel (“Atlantic Channel”), and the Sandbridge Shoal federal OCS lease area managed by the Bureau of Ocean Energy Management as a sand source for coastal municipalities. Sediment samples were sieved and gravity-separated for heavy mineral sand concentration, and 23 concentrates were submitted to SGS Laboratories, LLC for detailed modal mineralogy. The average THM fraction for the two borrow areas within Sandbridge Shoal is 0.85 wt%, with a maximum of 1.9 wt% and a minimum of 0.4 wt%. Ilmenite is the most abundant economic heavy mineral making up 35-45 wt% of the THM fraction, while zircon and rutile each make up 5-7 wt% THM, and monazite and xenotime are <0.1 wt% THM. We used the wt% THM with reported sand resource volumes for Sandbridge Shoal offshore of Virginia Beach to calculate a heavy mineral sand resource. We preliminarily estimate 330,000 metric tons of THM, part of which contains critical commodities titanium, zirconium, and rare earth elements.

In addition to the mineral resource estimate, we highlight current methodologies and technologies that may be needed for co-extraction of heavy minerals from sand aggregate material. The findings presented here serve as a guide toward cooperative and economically beneficial relationships between marine and coastal resource end-users.