USING AIRBORNE GEOPHYSICS TO ASSIST MAPPING IN THE EASTERN PIEDMONT: GEOLOGIC MAP OF WHITE OAK CREEK 7.5-MINUTE QUADRANGLE, FAIRFIELD AND KERSHAW COUNTIES, SOUTH CAROLINA

The South Carolina Geological Survey mapped the White Oak Creek quadrangle (WOC) as part of the USGS Earth Mapping Resources Initiative (Earth MRI). WOC is located within the Haile-Ridgeway and Brewer Focus Area, which contains known porphyry Cu-Mo-Au deposits that are prospective for Sb, As, Bi, Fl (topaz), REE, Te, and Zn mineral resources, and within the Neoacadian-Alleghanian Regolith Focus Area, where the validity of a regolith-hosted ion-adsorption REE deposit model in weathered granite plutons is being tested.

WOC contains four distinct lithotectonic elements: (1) Neoproterozoic – Early Cambrian Carolina terrane (Ct), (2) Pennsylvanian-Permian Liberty Hill pluton (LHP), (3) Jurassic diabase dikes and (4) Atlantic Coastal Plain sediments (CP). The Ct consists of polydeformed, regionally metamorphosed, greenschist facies intermediate to felsic volcanic and siliciclastic sedimentary rocks assigned to the Persimmon Fork Formation and Richtex Formations, respectively. The LHP is a granite laccolith that intrudes the Ct, consists of three compositionally and texturally separate zones, and imparts a 2 km-wide contact aureole (CA) on the surrounding Ct rocks. NW and NNW-trending Jurassic diabase dikes crosscut the earlier Piedmont rocks. Across the Fall Line, poorly sorted to well sorted, unconsolidated sublitharenite to quartz arenite CP sands unconformably overly the Piedmont crystalline rocks. West of the Fall Line CP outliers are mapped at higher elevations surrounded by Ct and LHP.

Earth MRI-funded geophysical surveys aided mapping where outcrop and exposure were limited. Aeromagnetic data indicated the presence of magnetite-rich zones in metasedimentary rocks within the CA, delineated diabase dikes and helped to recognize mineralogical facies within the LHP. Aeroradiometric K data expressed as %K delineated the contacts between the K-feldspar bearing LHP, and both the overlying mineralogically mature CP sands and the surrounding K-poor Ct. The utility of %K data is questionable where the transport of K-rich sediment derived from the LHP masks the underlying K-poor Ct bedrock. Future use of this geophysical data in the Ct and LHP could help identify critical mineral bearing Cu-Mo-Au deposits and distinct REE-bearing lithofacies, respectively.