PIEDMONT TO PLATEAU: NEW HIGH-RESOLUTION AIRBORNE GEOPHYSICAL DATA OVER A TRANSECT OF THE APPALACHIAN PROVINCES

We present preliminary results from an Earth MRI airborne magnetic and radiometric survey covering parts of Pennsylvania, Maryland, West Virginia, and Virginia. This ~48,000 km² survey, flown at 250-m line spacing, covers parts of five major eastern U.S. geological provinces with critical mineral potential: 1) The Appalachian Plateau, hosting high-Al underclays (Al, Ga, Li, REE potential), 2) the Valley and Ridge with extensive sequences of metalliferous shales and phosphates (Cr, Co, Mn, Ni, PGE, REE, Re, V, fluorspar potential), the 3) Blue Ridge and 4) Piedmont, which host volcanogenic and mafic magmatic deposits (Bi, Co, Cr, Ga, Ge, In, Mn, Ni, PGE, Sb, Sn, Te, Ti, W, Zn potential) as well as CAMP and skarn deposits in the Gettysburg rift basin (Co, Ni, PGE, Te potential), and 5) a small portion of the Atlantic Coastal Plain, which may host placer deposits (Ti, Zr, REE potential). The Gettysburg basin and surrounds are also a site of intraplate seismicity.

The survey started in August 2022 and is about 55% complete as of the date of this abstract. In the Valley and Ridge and Appalachian Plateau provinces, radiometric data highlight outcropping Paleozoic sedimentary units, with Th and K showing dramatic contrasts over sandstone, siltstone, shale, and limestone units, e.g. carbonate-rich lithologies show higher K and sandstones within Devonian shales show higher Th. Within the highly folded and faulted Valley and Ridge, clear structural relations are observed. The magnetic data in these provinces show gentle, long-wavelength anomalies reflecting the >5 km depth of the crystalline basement and clearly delineate part of the NY-AL magnetic lineament. Within the Piedmont and Blue Ridge (~30% flown to date), magnetic data show thin, linear anomalies that correspond to dikes and structural features within these igneous and metamorphic terranes. Within the Gettysburg rift basin, subdued anomalies probably representing the basin floor are punctuated by magnetic highs that likely correspond to Jurassic diabase and magnetite skarns. Radiometric K is elevated over granitoid and rhyolitic rocks as well as arkose sandstone in the Gettysburg basin; Th is elevated over shale and schist units. New insights regarding the geologic and structural history of these provinces are highly anticipated as data collection continues.