Preliminary definition of the geothermal resources potential of Pennsylvania

Pennsylvania has a diverse geology. A small portion of the northeastern corner of the state is covered by Atlantic Coastal Plains sediments. To the northwest metamorphic rocks in the Piedment, Blue Ridge and Reading Prong areas are exposed. Triassic basine cut across portions of the Piedmont. The western portion of the state is underlain by Paleozoic sediments of the folded Appalachians and the Appalachian or Allegheny Basin. Crystalline rocks are limited to the metamorphic and igneous rocks of the Piedmont, Blue Ridge, and Reading Prong and to Triassic diabase intrusives. Potential for geothermal resources in Pennsylvania appear to be limited to small hydrothermal systems associated with deep convection in the folded Appalachians or deep sources in the Appalachian Basin. Heat flow measurements and temperature gradients from oil and gas wells suggest normal continental heat flow in Pennsylvania. Under such conditions temperatures of about 200{sup 0}C (392{sup 0}F) are possible near the base of the sedimentary section (about 9 km, 30,000 feet). Warm springs are not as common in Pennsylvania as they are to the south in West Virginia and Virginia. Apparently the structure does not facilitate convective circulation. Geothermal resources in Pennsylvania appear to be restricted to those available in an area of normal temperature gradients