OFFSHORE Sand Resources and Economic Heavy Minerals
The DMME Division of Geology and Mineral Resources (DGMR) has conducted investigations of marine mineral resources on the continental shelf offshore of Virginia since our initial partnership in 1985 with the U.S. Department of Interior, Minerals Management Service (MMS). Our most recent project, funded in part by the successor to MMS, the U.S. Bureau of Ocean Energy Management (BOEM), provides new information about the thickness, lateral extent, and textural characteristics of potentially valuable deposits of clean, beach-quality sand that could be utilized for shoreline restoration projects and coastal ecosystem protection.
Volumetric assessments of beach-quality sand were conducted in the brown-shaded areas offshore of Wallops Island and Sandbridge Beach.
Our studies have also identified heavy minerals that were deposited with offshore marine sediments in quantities ranging from trace amounts to over 10 weight percent. Heavy minerals have a specific gravity greater than about 2.9 (common quartz – not a heavy mineral – has a specific gravity of 2.65), and include ilmenite (FeTiO3), leucoxene (altered ilmenite), rutile (TiO2), zircon (ZrSiO4), and monazite ((Ce,La,Y,Th)(PO4)), among others. These minerals contain critical elemental commodities such as titanium, zirconium, chromium, and rare earth elements (REE) that have commercial value and are potentially recoverable as an integral part of beach restoration operations.
Laboratory analysis of total heavy mineral (THM) concentrates from offshore samples has allowed for the quantification of the compositional variability of economic minerals, and the concentrations of the critical commodities they contain. The results also provide new information about grain size characteristics that, together with specific gravity and magnetic susceptibility, are important for the evaluation of recovery and separation methods.
Latest reports »
Open File Report 2019-03 – Economic heavy minerals on the continental shelf offshore of Virginia - new insights into the mineralogy, particle sizes, and critical element chemistry.
Open File Report 2019-04 – Heavy mineral distributions in offshore sediments using Q-mode factor analysis.
Open File Report 2016-01 - Grain size distribution and heavy mineral content of marine sands in Federal waters offshore of Virginia.
Locations of sediment samples analyzed for economic heavy minerals.
Why Are We Studying Offshore Sand Resources?
Sand and gravel is mined for natural aggregate and serves as a vital material for construction activities in our communities. The supply and availability of onshore sand and gravel resources is constrained by several factors, most importantly the increasing costs of transporting material from the mine source to the end user, typically by truck or rail. Offshore sources of material located on the continental shelf in State and Federal waters can be dredged and transported at relatively lower costs, and can meet the increasing demands for larger quantities of sand. Offshore sand deposits also serve as emergency reserves for coastal restoration following natural disasters. This is especially critical in our coastal communities that face growing risks from tidal flooding, erosional damages caused by increased storm frequency and duration, and accelerated sea level rise.
Shoreline stabilization is a major concern in many areas of Virginia, and various methods to accomplish this have included the construction of structural controls and barriers such as seawalls, groins and breakwaters. In recent years, a more natural “living shoreline” approach has utilized vegetation plantings to enhance dune formation, and beach sand replenishment. Also known as “beach nourishment”, sand from a source area that meets certain textural and compositional requirements is dredged and transported to a beach that has been severely impacted by erosion. The source areas may include material dredged as part of channel maintenance, or from known sand deposits in State and Federal waters. It is important to note that beach nourishment does not stop the erosive forces of the ocean, but rather provides a cost-effective means of reducing the risks associated with storms and flooding.
Marine sand deposits occur in a variety of settings including submerged shoals, lenticular sand sheets, and buried alluvial channels. Sand bodies that are considered suitable for dredging are identified on the basis of economic factors including the thickness and lateral extent of recoverable material, grain size and shape characteristics, suitable mineralogy, distance from shore, and the thickness of overburden. Equally important are environmental considerations to ensure the protection of sensitive benthic communities, marine faunal and floral habitats, minimizing post-dredging impacts on ecosystem services, and avoidance of archaeological and other restricted sites (military use, underwater cables, pipelines, etc.). The Federal Outer Continental Shelf Lands Act (OCSLA) authorizes BOEM to lease and regulate marine minerals seaward of the State–Federal boundary line located three nautical miles (nm) from shore.
Beach nourishment operations at Sandbridge Beach
(photo courtesy of Virginia Institute of Marine Science Shoreline Studies Program).
Economic Heavy Minerals
Offshore sand deposits contain disseminated heavy minerals that are sources of titanium- and zirconium-oxides used in the manufacture of pigment for paints, plastics, ceramic glazes, and other industrial uses. Other minerals of potential economic interest include monazite, sillimanite minerals (Al2SiO5), garnet ((Mg, Fe, Mn, Ca)Al2Si3O12), and high-purity silica quartz. Occurrences of these minerals reflect the geologic processes that have acted on bedrock and sediments in Virginia’s Coastal Plain – erosion, sediment transport, and deposition – combined with marine processes that have sorted and re-distributed the sediments on the continental shelf. Depending upon the concentration, extent, and mineral composition of these resources, economically viable deposits may be co-extracted with marine sand for beach nourishment, or possibly as stand-alone heavy mineral mining operations.
Heavy minerals (dark areas in center of photo) concentrated by wave action on Sandbridge Beach.
For more information contact DGMR.
Funding for this project was provided by the U.S. Bureau of Ocean Energy Management (BOEM) under Cooperative Agreement M14AC00013 with additional funding contributions from the Virginia Department of Mines, Minerals and Energy (DMME).
For more information about marine minerals on the Atlantic continental shelf, visit the BOEM web site.
Berquist, C.R., Jr., and C.H. Hobbs, III, 1986, Assessment of economic heavy minerals of the Virginia inner shelf: Virginia Division of Mineral Resources Open File Report 86-1.
Berquist, C.R., Jr., and C.H. Hobbs, III, 1988, Study of economic heavy minerals of the Virginia inner continental shelf: Virginia Division of Mineral Resources Open File Report 88-4, 149 p.
Berquist, C.R., Jr., [ed.], 1990, Heavy-mineral studies – Virginia inner continental shelf, Virginia Division of Mineral Resources Publication 103, 124 p.
Berquist, C.R., Jr., Lassetter, W.L., and Goodwyn, M.H., 2016, Grain size distribution and heavy mineral content of marine sands in Federal waters offshore of Virginia: Virginia Division of Geology and Mineral Resources Open File Report 2016-01, 34 p.
Berquist, C.R., Jr., and Boon, J.D., 2019, Heavy mineral distributions in offshore sediments using Q-mode factor analysis: Virginia Division of Mineral Resources Open File Report 2019-04, 35 p.
Blanchette, J.S., and Lassetter, W.L., 2019, Assessment of offshore sand resources for beach remediation in Virginia: Virginia Division of Geology and Mineral Resources Open File Report 2019-02, 24 p. and Appendices.
DMME (Department of Mines, Minerals and Energy), 2012, Sand resource evaluation on Virginia’s outer continental shelf – Final Technical Report: Prepared for U.S. Bureau of Ocean Energy Management, Cooperative Agreement M10AC20021 for the performance period Sept 14, 2010 to Oct 31, 2011: 19 p.
Goodwyn, M.H., Enomoto, M.R., Lassetter, W.L., and Kuehl, S.A., 2016, GIS compilation of geophysical data on Virginia’s Outer Continental Shelf: Division of Geology and Mineral Resources Open File Report 2016-02.
Lassetter, W.L., and Blanchette, J.S., 2019, Economic heavy minerals on the continental shelf offshore of Virginia - new insights into the mineralogy, particle sizes, and critical element chemistry: Virginia Division of Geology and Mineral Resources Open File Report 2019-03, 33 pp and Appendices.
Milligan, D.A., Kuehl, S.A., and Hardaway, C.S., 2016, Digital conversion of geologic core data, quality control, and preliminary assessment of sand resource area on Virginia’s Outer Continental Shelf: Division of Geology and Mineral Resources Open File Report 2016-03.
Blanchette, J., and W.L. Lassetter, 2018, Marine mineral resources on Virginia’s outer continental shelf: quantifying sand deposits for coastal restoration and occurrences of economic heavy minerals [abs]: Geological Society of America Northeastern Sectional Annual Meeting, 17-20 March 2018, Burlington, VT.
Lassetter, W.L., Blanchette, J.S., and Holm-Denoma, C., 2019, Marine mineral resources on the continental shelf offshore of Virginia: new insights concerning economic heavy minerals: [abs]: Geological Society of America Southeastern Sectional Annual Meeting, 28-29 March 2019, Charleston, SC.