Northeastern Section - 47th Annual Meeting (1820 March 2012)
Paper No. 40-3
Presentation Time: 1:30 PM-5:30 PM

FLUID INCLUSION STUDY OF VEINS IN THE MARCELLUS SHALE ALONG THE APPALACHIAN STRUCTURAL FRONT IN CENTRAL PENNSYLVANIA: PALEOFLUIDS AND THERMAL MATURITY

LEO, Jeremy, Physics and Earth Science, Central Connecticut State University, New Britain, CT 06050, j.leo@my.ccsu.edu and EVANS, Mark A., Department of Physics and Earth Science, Central Connecticut State Univ, 1615 Stanley St, New Britain, CT 06050

The Marcellus shale in the Pennsylvania Plateau province exhibits distinct zones of high thermal maturation based on vitrinite reflectance data. The origin of these zones is unclear, but may be due to passage of ‘warm’ fluids. In order to test this hypothesis, fluid inclusion microthermometry of calcite and quartz vein minerals was used to investigate the paleofluid history in the Marcellus shale along the Appalachian Structural Front in central Pennsylvania. Samples of vein material were obtained from eight sites, from Buffalo Mills, PA, northeast through Bellefonte, PA. The southernmost sites are adjacent to a high thermal maturity zone in the plateau, while the northernmost sites were adjacent to a low maturity zone.

The vein material from the south is mostly calcite followed by quartz whereas in the northern lower thermal maturity area, the veins consist of calcite only. Primary and pseudosecondary fluid inclusions from the veins in the north show homogenization temperatures (Th) of 14.7° to 119.3°C, and they fluoresce light blue and yellow-gold indicative of liquid hydrocarbons and condensate-like fluids. In contrast, fluid inclusions from the calcite in the south have Th values of -93.7 to -78.2°C, while quartz Th values are -93.7° to -77.9°C, indicating nearly pure methane. The quartz inclusions were trapped at a minimum of 100°C at 55 MPa pressure. Fluid inclusions in quartz exhibit solid melting at -110°C, indicating the presence of 2% CO2 in the methane. The source of the CO2 may be from the dissolution of calcite during influx of fluids resulting in quartz precipitation. Quartz with CH4±CO2 inclusions is also found in a deep well core from the Marcellus shale in the eastern plateau in the high maturity zone.

In summary, in the low maturity north, veins contain in-situ petroleum fluids, whereas in the high maturity south, the presence of methane and late quartz suggests that ‘warm’ exotic fluids may be responsible for the increased thermal maturation.

Northeastern Section - 47th Annual Meeting (1820 March 2012)
General Information for this Meeting
Session No. 40--Booth# 20
Structural Geology (Posters)
Hartford Marriott Downtown: Ballrooms A & C and Ballroom Pre-function Area
1:30 PM-5:30 PM, Monday, 19 March 2012

Geological Society of America Abstracts with Programs, Vol. 44, No. 2, p. 96

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