Northeastern Section - 44th Annual Meeting (2224 March 2009)
Paper No. 54-14
Presentation Time: 8:00 AM-12:00 PM


DABROWSKI, Daniel, Physics and Earth Science, Central Connecticut State University, New Britain, CT 06050, and EVANS, Mark, Department of Physics and Earth Sciences, Central Connecticut State University, New Britain, CT 06050

Fluid inclusion microthermometry of quartz in syn- to post-metamorphic veins is used to infer the post-peak metamorphic fluid history and deformation conditions of the Wepawaug Schist in southern Connecticut. Veins were sampled across the steep Barrovian metamorphic gradient, from the chlorite zone, biotite-garnet zone, and staurolite-kyanite zone.

Most fluid inclusions are two-phase, typically less than 10 microns in size, have a vapor bubble occupying <10- 20% volume % of the inclusion, and contain NaCl-rich fluids with less than 6.0 wt. % NaCl equivalent salinity. They occur as primary and pseudosecondary inclusions in chlorite zone veins; and as pseudosecondary and secondary inclusion in the biotite-garnet and staurolite-kyanite zones. In the higher grade zones, most primary inclusions exhibit re-equilibration textures. Primary inclusions in a NE-striking vein in the chlorite-zone have homogenization (Th) values of 144 - 177C and 2.9 to 3.5 % salinity, while inclusions in a NW-striking vein have Th values of 220 - 228C and 5.7 to 6.0 % salinity. Both veins post-date foliation. The NE-striking vein gives trapping conditions (based on lithostatic [25C km-1 and 26 MPa km-1]) of 320 - 460C and 315 450 MPa (12.1 17.3 km) and the NW-striking vein gives conditions of 415 - 425C and 405 420 MPa (15.6 16.2 km).

A folded quartz vein in the biotite-garnet zone has pseudosecondary inclusions that have Th) values of 201 - 236C and 5.0 % salinity, corresponding to trapping conditions of 390 - 450C and 380 445 MPa (14.6 17.1 km). A foliation-parallel vein in the biotite-garnet zone has coeval pseudosecondary CH4-CO2) and two-phase brine inclusions (Th) of 217 - 249C and 4.0 to 4.7 % salinity) that were trapped at 505C and 340 MPa (13.0 km). Secondary inclusions in a recrystallized foliation-parallel vein from the staurolite-kyanite zone has Th) values of 132 - 145C and 1.2 % salinity, giving trapping conditions of 295 - 315C and 290 310 MPa (11.2 11.9 km).

In general, fluid inclusions were trapped at 300 - 500C and <450 MPa, significantly less than 400 - 600C and 600 900 MPa at peak metamorphism as determined by Ague (1994). Therefore, fluid inclusions in veins reflect post-peak metamorphic conditions in the Wepawaug Schist, and were probably trapped as the system opened during unroofing and was at a depth of 12-17 km.

Northeastern Section - 44th Annual Meeting (2224 March 2009)
General Information for this Meeting
Session No. 54--Booth# 34
Igneous/Metamorphic Petrology, Geochemistry, Mineralogy (Posters)
Holiday Inn By the Bay: Casco Bay Hall
8:00 AM-12:00 PM, Tuesday, 24 March 2009

Geological Society of America Abstracts with Programs, Vol. 41, No. 3, p. 110

© Copyright 2009 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.