PETROGRAPHY OF PETROLEUM FLUID INCLUSIONS IN POST-DIAGENETIC QUARTZ FROM THE BRALLIER FORMATION ON THE MARGIN OF THE BROAD TOP BASIN, PENNSYLVANIA

Fluid inclusion investigation of post-diagenetic quartz occurring within crosscutting vein-filled, slicked fractures in the Brallier Formation indicates a plethora of diverse hydrocarbon-rich fluids that flowed through Upper Devonian strata. Euhedral to sub-euhedral quartz was collected along the structurally active Tyrone-Mt. Union lineament on the western limb of the Broad Top Synclinorium. The fluids trapped within these post-diagenetic crystals are mostly composed of complex hydrocarbons, as shown by a UV-light source. The majority of the hydrocarbon inclusions fluoresced blue with some brown fluorescence interspersed. Individual quartz crystals showed a complex history of fluid entrapment, involving multiple types of petroleum fluids, ranging from gas condensates to light oils, indicated by the initial bubble volume. Inclusion bubbles, ranging in size from five to 60μm, homogenized to either liquid or gas. The temperatures of homogenization that were collected from these petroleum inclusions almost certainly do not reflect the entrapment temperature of the fluid. Homogenization temperatures ranged from 60-104⁰C. The fluids traveling through the Upper Devonian Brallier Formation may have come from either the directly underlying Hamilton Group or deeper Martinsburg Formation. This fluid inclusion study provides a useful record of hydrocarbon migration through the Upper Devonian-aged Brallier Formation, which can be used to trace fluid flow through the Paleozoic stratigraphic column in south-central Pennsylvania. These data undoubtedly have bearing on the oil and gas potential of rocks in the Broad Top Basin.