NEW HIGH-RESOLUTION AIRBORNE GEOPHYSICAL DATA FROM THE APPALACHIAN PROVINCES: EARLY INSIGHTS INTO THE EXTENT OF JURASSIC SYN-RIFT MAGMATISM AND THE ROLE OF PRE-EXISTING STRUCTURES

We present initial interpretations of an Earth Mapping Resources Initiative high-resolution airborne magnetic and radiometric survey over portions of Appalachian provinces within Pennsylvania, Maryland, Virginia, and West Virginia. The magnetic and radiometric data generally reveal strong correlations with mapped lithologies, but also suggest areas where mapping might be revisited. Results have implications for Paleozoic orogenic processes, Mesozoic magmatism, and critical mineral resources. Smooth, long wavelength magnetic anomalies observed across the Appalachian Plateau and Valley and Ridge provinces are consistent with greater depth to crystalline basement. However, in the eastern Valley and Ridge, an isolated, high-amplitude, narrow magnetic high (approximately 1.5 km by 0.6 km) has revealed the extent of an ultramafic kimberlite originally mapped from float. We observe similar narrow anomalies of slightly lower magnitude elsewhere in the Valley and Ridge, suggesting buried magnetized sources within the sedimentary strata. In the Piedmont and Blue Ridge provinces, where Neoproterozoic-Lower Paleozoic igneous and metamorphic rocks are exposed at the surface, high amplitude short-wavelength anomalies dominate the magnetic field, indicating shallow sources. We interpret prominent NE-SW magnetic lineaments to represent Paleozoic structural fabric, including a shear zone and possible suture between Laurentia and accreted terranes. The Mesozoic Gettysburg and Newark rift basins follow the Paleozoic fabric, suggesting their formation was linked to strain localization along pre-existing structures. Strong magnetic highs and low K and Th signatures in these Mesozoic basins correspond to known Jurassic diabase sills and suggest potential locations for others. The diabase sills are of economic interest, as cobalt deposits and platinum group element occurrences have been identified within outcrops. At least two mineralized areas are associated with magnetic highs. Linear magnetic anomalies correlate with mapped Jurassic dikes and transect the Piedmont, Blue Ridge, and Valley and Ridge provinces. In almost all cases, the anomalies intersect sills within the Mesozoic basins. Individual anomalies are oblique to Paleozoic fabric in some areas, but parallel in others suggesting local influence of structural inheritance during emplacement.