EARTH MRI IN SOUTH CAROLINA, RESEARCH INTO CRITICAL MINERALS ONSHORE AND OFFSHORE

South Carolina (SC) shows promise in having heavy mineral deposits with Rare earth elements (REE) and Ti both on- and offshore. REE and Ti are considered critical mineral resources defined by Executive Order 13817 and subsequent DOI directives. A critical mineral is a non-fuel commodity deemed important to the security and economy of the US. These commodities are being targeted by the Earth Mapping Resources Initiative (EMRI). In SC, REE-hosting monazite and xenotime have been found in both crystalline and sedimentary rocks. Heavy mineral sands containing monazite have been mined in SC for Ti and Zr, with monazite recovered as an accessory mineral.

The SC Geological Survey is collaborating with state universities and BOEM to identify offshore REE resources as a supplementary part of a project to identify sand resources. High-definition mineralogy of offshore samples separated with heavy-liquids detected liberated monazite and zircon. Elemental analyses show abundant Ce, Dy, La, Th, Y, and Zr in the sink fraction. Zr and Th have high upgrading factors indicating that heavy mineral deposits could be successfully processed.

Onshore, the USGS has evaluated the presence of heavy minerals and REE in the Southeastern Atlantic Coastal Plain. This work focused on identifying sources of radiometric equivalent thorium (eTh), a proxy for monazite and xenotime in the upper 1m. In SC, eTh anomalies indicate that REM placer deposits are located along the Fall Line and above the Orangeburg scarp.

In Summer 2019, aeromagnetic and radiometric surveys were flown from the Orangeburg scarp to Charleston. Elevated eTh anomalies appear to correlate with mapped lithofacies and primary landforms in the Lower Coastal Plain and along the coast.

In SC, an ongoing set of geophysical surveys and a geologic mapping project funded by EMRI will be used to evaluate eTh anomalies between the Orangeburg scarp and the Fall Line. New surveys and mapping are being proposed to locate regolith-hosted REE deposits in the SC Piedmont. The extent of these deposits is poorly understood. The new data, along with geologic mapping, geochemistry, and geochronology, will provide for a completely new deposit model. This work will also advise a source-to-sink model for weathering, transport, and deposition of critical minerals across the Piedmont and Atlantic Coastal Plain.