265 D3. Recent Advances in Economic Geology (Posters)

Wednesday, 12 October 2022
2:00 PM - 6:00 PM
Exhibit Hall F

MARINE MINERAL SANDS ON VIRGINIA’S OUTER CONTINENTAL SHELF – THE CASE FOR EXTRACTING CRITICAL MINERALS AS PART OF BEACH RESTORATION PROJECTS

Paper number: 265-29
Program: Technical Sessions
Time: 2:00 PM – 6:00 PM

Authors

Abstract

Since the 1980s, Virginia’s state geological survey has worked collaboratively with federal and other state agencies to assess marine mineral resources on the continental shelf. Substantial deposits of beach-quality sand have been identified in two main areas: (1) shoal and sheeted sand deposits located offshore of Assateague and Wallops Islands, and (2) shoal deposits located offshore of the community of Sandbridge. These deposits occur within 10 feet of the subbottom at water depths of less than 60 feet, and are accessible by marine dredging for use as beach nourishment sand. These sand deposits also contain heavy minerals that are potential sources of critical commodities such as titanium (Ti), zirconium (Zr), and rare earth elements (REE).

A feasibility study is presently underway to evaluate methods for recovering economic heavy minerals in marine sands. Three main goals of the study are to: (1) assess separation and recovery methods that may be integral to beach nourishment operations, (2) develop a field protocol for rapid screening of critical elements using a portable X-ray fluorescence (pXRF) and gamma scintillometer, and (3) assess environmental and safety concerns associated with mineral separation processes. The total heavy mineral (THM) content assessed in over 600 sediment samples taken from offshore averages 2.7% by weight, up to 14.7%. The average composition of the THM fractions consists of 34% Ti-minerals (ilmenite, rutile, and leucoxene), 3.4% zircon, and lesser amounts of xenotime, titanite, and monazite. Based on recent market prices of mineral concentrates, the estimated value of 1 cubic yard of sand containing 2.7% THM is about $10.80. Applying this unit value to a recent beach nourishment project that placed about 1.8 million cubic yards of sand on Sandbridge Beach, the estimated value of THM is nearly $20 million.

The positive benefits of recovering heavy minerals from beach sand placements are threefold. First, the value of these minerals has the potential to offset the costs of coastal resilience projects. Second, these minerals represent a potential source of domestic critical commodities that by definition are essential to economic and national security. Third, the removal of dark heavy minerals from beach sand placed in tourist areas results in a more desirable lighter appearance.

Geological Society of America Abstracts with Programs. Vol. 54, No. 6

doi: 10.1130/abs/2022AM-381889

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