Northeastern Section - 49th Annual Meeting (2325 March)
Paper No. 27-3
Presentation Time: 1:30 PM-4:15 PM

FLUID HISTORY AND PALEO-OVERBURDEN DURING THE ALLEGHENIAN OROGENY: CENTRAL PENNSYLVANIA VALLEY AND RIDGE PROVINCE

DELISLE, Amanda, Department of Physics and Earth Science, Central Connecticut State University, 1615 Stanley Street, New Britain, CT 06050, a.delisle@my.ccsu.edu and EVANS, Mark A., Department of Physics and Earth Science, Central Connecticut State Univ, 1615 Stanley St, New Britain, CT 06050

Fluid inclusion microthermometry of syn-tectonic vein minerals provides information on fluid history, including trapping conditions (PT), composition, hydrologic structure, and changes during deformation. Quartz and calcite veins were sampled from multiple stratigraphic levels along a transect in the Pennsylvania Valley and Ridge province, from the Appalachian Structural Front to the Great Valley. A line-balanced structural cross-section was constructed along the same transect to provide insight on the structural geometry of the area. The structural style across the Valley and Ridge changes from a series of closely-spaced C-O carbonate imbricate horses toward the hinterland to a long flat-on-flat toward the foreland, culminating in an antiformal stack of three carbonate layers.

In both Ordovician carbonate and clastic rocks, blocky calcite contains aqueous brine inclusions trapped at 104 -139 °C with salinities of 23.7-28.0 wt. %, and uncommon CH4 inclusions. Fluid trapping pressures range from 84-97 MPa. In the Silurian - Devonian carbonate rocks, blocky calcite contains aqueous brine inclusions trapped at 79-138 °C and have salinities of 24.0-28.0 wt. %. Fluid trapping pressures are interpreted to be 130-155 MPa. Middle Devonian clastic rocks contain early blocky calcite and dolomite with light-brown tinted hydrocarbon inclusions. Later quartz is blocky, but also occurs as prismatic and euhedral crystals up to 3 cm across. These contain aqueous brine inclusions that homogenize at 148-204 °C and have salinities of 7.9-18.6 wt. %. The quartz also contains abundant CH4±CO2 inclusions that homogenize as low as -122 °C with up to 6% CO2.There are at least two major growth phases within the quartz crystals as determined by SEM-CL analysis as well as numerous smaller incremental growth zones. There is a wide range of trapping conditions, with increasing trapping pressures from center to rim, indicating changing deformation conditions during crystal growth. In contrast, Middle Devonian rocks at the structural front contain only liquid hydrocarbon and condensate-like fluid inclusions that reflect low trapping temperatures. There is an apparent significant drop in paleo-overburden at this structural transition ranging from 4-5 km within the Valley and Ridge to less than 0.5 km at the Structural Front.

Northeastern Section - 49th Annual Meeting (2325 March)
General Information for this Meeting
Session No. 27--Booth# 34
Tectonic Links between the Northern and Southern Appalachians (Posters)
Lancaster Marriott at Penn Square: Freedom Hall A
1:30 PM-4:15 PM, Sunday, 23 March 2014


© Copyright 2014 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.