MAPPIN' WITHOUT DIGGIN': AN APPLICATION OF MAGNETOMETRY TECHNIQUES IN RITTENHOUSE GAP MINING DISTRICT IN BERKS COUNTY, PENNSYLVANIA

Magnetite veins in the Rittenhouse Gap iron-mining district located in Berks County, Pennsylvania are parallel, but offset in a stepped fashion, cutting Proterozoic granitic gneisses. Forest litter obscures all of the outcrop, making geologic mapping difficult. We used a hand-held proton procession magnetometer coupled with a GPS receiver, sampling with a two-meter area, and compiled our data with GIS to map the magnetic field in the iron-mining district. We interpreted the variations in the magnetic data in terms of wall rock hydrothermal alteration, calibrated by comparing magnetic data with petrographic studies of rocks exposed in the iron-mine region. In order to determine whether the district’s en echelon vein pattern reflects a large-scale Reidel shear fracture, or offsets of a simple vein by cross faults, a larger study area involving smaller grids of magnetometer readings would generate a clearer and decisive underground petrology picture.