THE MAGMATIC PLUMBING OF CAMP INTRUSIVES IN THE TRIASSIC/JURASSIC RIFT BASINS OF PENNSYLVANIA: INSIGHTS ON THE GETTYSBURG, YORK HAVEN, AND MORGANTOWN INTRUSIONS FROM GRAVITY AND AEROMAGNETIC DATA

Early Jurassic syn-rift magmatism emplaced in the Triassic/Jurassic Gettysburg and Newark rift basins, part of the Central Atlantic Magmatic Province (CAMP), has historically been a target of iron ore operations and mineral exploration. In Pennsylvania, known critical minerals related to this magmatism include magnetite skarns with byproduct cobalt and platinum group element occurrences. To better understand the mineral systems, we investigate the magmatic plumbing. The CAMP Gettysburg, York Haven, and Morgantown sheets, observed within these rift basins, are generally thought to have a bowl shape crosscutting Triassic syn-rift strata. Recent structural and geochemical analyses of the Morgantown intrusion, however, suggest that the magmatic plumbing is more likely a complex system of dikes, sills, sheets, and ramps. To image the subsurface magmatic plumbing, we analyze publicly available gravity data with recent high resolution aeromagnetic data, geologic maps, and models based on seismic reflection and structural observations. The most widespread expression of CAMP is a series of dikes traversing the region expressed as linear, positive, short-wavelength (< 250 m wide) magnetic anomalies, most of which intersect the sheets. In both the magnetic and bouguer gravity data, the Gettysburg, York Haven, and Morgantown intrusions exhibit positive short wavelength (generally < 2 km wide) anomalies within the rift basin that coincide with mapped diabase outcrops. Matched filtering shows that the northeastern half of the Gettysburg intrusion and northwestern half of the York Haven intrusion also exhibit positive intermediate to long-wavelength (> 5 km wide), collocated magnetic and bouguer gravity anomalies. These collocated anomalies suggest dense, magnetic sources lie beneath the shallow sills. We interpret these deeper sources as underlying intrusive bodies which fed the shallowest diabase intrusions. To test this hypothesis, we also use two-dimensional (2-D) forward models of the gravity and magnetic data with structural and geologic controls to investigate the plumbing of these magmatic systems. Our early 2-D forward models of the Gettysburg basin suggest that the magmatic plumbing is a complex system of shallow dikes, sills, and sheets fed by an underlying intrusive body.