Partnering with the U.S. Geological Earth Mapping Resources Initiative (Earth MRI) provides a new opportunity to create maps that will stimulate domestic exploration for mineral resources that are critical to U.S. security and economic prosperity. This project is designed to support the goals of Federal Executive Order 13817 to strengthen and sustain our Nation’s critical mineral supply chains, and the Earth MRI Program to “improve topographic, geologic, and geophysical mapping of the United States and make the resulting data and metadata electronically accessible”.
Marcie Occhi and Aaron Barth
Strengthening the critical mineral supply chain – Placer deposits of heavy minerals that occur in unconsolidated fluvial and near shore sediments in the inner Coastal Plain of Virginia are a proven economic resource for Ti, Zr, and REE (Berquist and others, 2015; Bern and others, 2016; Shah and others, 2017). These commodities are among those identified by the USGS in 2018 as “essential to the economic and national security of the United States (Fortier and others, 2018). The critical commodities are concentrated in heavy minerals such as ilmenite, rutile, leucoxene, zircon, and monazite. These minerals occur in trace amounts in Paleozoic-age igneous and metamorphic rocks in the Piedmont, and once liberated by weathering, can be concentrated in sediments due to their relatively high specific gravity (> 2.9). A major objective of this project is to gain a better understanding of the geologic processes that influence the transport and concentration of economic heavy minerals. We expect to provide new geologic and geochemical data that will encourage exploration by the private sector to identify new mineral reserves.
Geologists collecting stream sediment sample
Improving geologic map coverage – The best available geologic map for a large portion of Virginia’s Coastal Plain is the 1:250,000-scale geologic map by Mixon and others (1989). While this map is an excellent resource, it does not provide sufficient detail for many needed decisions related to public safety, environmental protection, and economic development. Since 2000, Virginia has worked through the National Cooperative Geologic Mapping Program, STATEMAP component to improve the availability of detailed geologic maps. This effort has resulted in a new 1:100,000-scale geologic map of the Williamsburg 30- x 60-minute quadrangle (Berquist, 2013) and thirteen 1:24,000-scale geologic quadrangle maps. In addition, two quadrangles in the Petersburg area were mapped in cooperation with the National Park Service (Occhi and others, 2018). Despite this effort, significant areas in the Coastal Plain lack 1:100,000-scale or better map coverage. The proposed project will produce 1:100,000-scale geologic maps for the equivalent of six 1:24,000-scale quadrangles, resulting in improved map availability for more than 80% of the area targeted.
Sediment samples of Pleistocene-age Bacons Castle Formation
Marcie Occhi and Aaron Barth
Making geologic data electronically available – Most published geologic maps in the Coastal Plain are only available in hard copy format. Some recent maps are available in GIS, with a format ranging from separate shapefiles with minimal attribution to fully attributed NCGMP09 geodatabases. This project will improve the digital availability of geologic data by compiling the geology of the four target areas into a single, consistent digital geologic map and geodatabase that is fully compliant with GeMS and populated with available information about mineral resources, subsurface boring locations, and geochemical sample data. This map and geodatabase will be fully accessible to the public with complete metadata. The geodatabase will also serve as a nucleus for the planned 1:100,000-scale geologic maps and geodatabases of the Emporia 30- x 60-minute quadrangle and the Richmond metropolitan area.
For the 2019-2020 fiscal year, the USGS Earth Mapping Resources Initiative, geologic mapping in the placer Ti-Zr-REE deposits grant will compile existing geologic maps and complete new mapping along the Fall Zone to produce 1:100,000-scale geologic maps and a Geologic Map Schema (GeMS) compliant geodatabase.
Earth MRI 2019-2020 Focus Area
Bern, C.R., A.K. Shah, W.M. Benzel and H.A. Lowers, 2016 The distribution and composition of REE-bearing minerals in placers of the Atlantic and Gulf coastal plains, USA Journal of Geochemical Exploration Vol. 162, p. 50-61.
Berquist, C.R., A.K. Shah, and A. Karst, 2015, Placer deposits of the Atlantic Coastal Plain: stratigraphy, sedimentology, mineral resources, mining and reclamation: Cove Point, Maryland, Williamsburg and Stony Creek, Virginia, Society of Economic Geology Guidebook, 50, 48
Dischinger, J.B., Jr. 1987, Late Mesozoic and Cenozoic Stratigraphic and Structural Framework near Hopewell, Virginia: U.S. Geological Survey Bulletin 1567, 48 p.
DMME (Department of Mines, Minerals and Energy), 2020, Annual production reports submitted by mine operators, Division of Mineral Mining.
Duval, J.S., Carson, J.M., Holman, P.B., and Darnley, A.G., 2005, Terrestrial radioactivity and gamma-ray exposure in the United States and Canada: U.S. Geological Survey Open-File Report 2005-1413.
Fortier, S.M., Nassar, N.T., Lederer, G.W., Brainard, J., Gambogi, J., and McCullough, E.A., 2018, Draft critical mineral list – Summary of methodology and background information – U.S. Geological Survey technical input document in response to Secretarial Order No. 3359: U.S. Geological Survey Open-File Report 2018-1021, 15 p.
Grossman, Jeffrey N., 1998, National Geochemical Atlas: The geochemical landscape of the conterminous United States derived from stream sediment and other solid sample media analyzed by the National Uranium Resource Evaluation (NURE) Program: U.S. Geological Survey Open-File Report 98-622, U.S. Geological Survey, Reston, VA.
Johnson, G.H. and Berquist, C.R., Jr., 1989, Geology and mineral resources of the Brandon and Norge quadrangles, Virginia: Virginia Division of Geology and Mineral Resources Publication 87, 28 p.
McClenaghan, M.B., 2011, Overview of common processing methods for recovery of indicator minerals from sediment and bedrock in mineral exploration: Geochemistry, Exploration, Environment, Analysis, Vol 11, p. 265-278.
Mertie, J.B., Jr., 1975, Monazite placers in the southeastern Atlantic States: U.S. Geological Survey Bulletin 1390, 41 p.
Mixon, R.B., Berquist, C.R., Newell W.L., and Johnson, G.H., 1989, Geologic map and generalized cross-sections of the Coastal Plain and adjacent parts of the Piedmont, Virginia: U.S. Geological Survey Map I-2033, one sheet.
Occhi, M.E., Blanchette, J.S. and Berquist, C.R., Jr., 2017, Geologic Map of the Chester quadrangle, Virginia: Virginia Division of Geology and Mineral Resources 2017 STATEMAP Deliverable, 1:24,000-scale map.
Occhi, M.E., Berquist, C.R., Jr., Latane, V.M., and Blanchette, J.S., 2018, Geology of the Petersburg National Battlefield and adjacent areas: Virginia Division of Geology and Mineral Resources 2018 NPS Grant Deliverable, 29 p.
Pirkle, F.L., Pirkle, W.A., and E.C. Pirkle 2007 Heavy Mineral Sands of the Atlantic and Gulf Coastal Plains, USA in Developments in Sedimentology, Vol. 58, p. 1144-1232 https://doi.org/10.1016/S0070-4571(07)58045-3
Shah, A.K., Bern, C.R., Van Gosen, B.S., Daniels, D.L., Benzel, W.M., Budahn, J.R., Ellefsen, K.J., Karst, A., Davis, R., 2017, Rare earth mineral potential in the southeastern U.S. Coastal Plain from integrated geophysical, geochemical, and geological approaches: Geological Society of America Bulletin Vol. 129, Issue 9-10, DOI: 10.1130/B31481.1.
Van Gosen, B., D. Fey, A. Shah, P. Verplanck, and T. Heofen, 2014, Deposit model for heavy-mineral sands in coastal environments, U.S. Geological Survey Scientific Investigations Report 2010-5070-L, 51 p.
Weems, R.E., Schindler, J.S., and Lewis, W.C., 2010, Detailed sections from auger holes in the Emporia 1:100,000-scale quadrangle, North Carolina and Virginia: U.S. Geological Survey Open-File Report 2010–1121, 288 p.