Start |Author Index | View Uploaded Presentations | Meeting Information

Northeastern Section - 42nd Annual Meeting (12–14 March 2007)

Paper No. 7
Presentation Time: 1:00 PM-4:45 PM

PETROLOGIC EXAMINATION OF THE LITTLETON FORMATION OF SOUTHWEST NEW HAMPSHIRE


FIREBAUGH, Barbara, Earth and Environmental Sciences, Rensselaer Polytechnic Institute, Troy, NY 12180, SPEAR, Frank S., Earth and Environmental Sciences, Rensselaer Polytechnic Institute, 110 8th St, Troy, NY 12180 and PYLE, Joseph M., Earth and Environmental Sciences, Rensselaer Polytechnic Institute, 110 8th St, Troy, NY 12180, birkeb@rpi.edu

Rocks of the Littleton Formation of southwest New Hampshire on the northern end of the Vernon Dome have been sampled and mapped across strike in an effort to better describe structural and metamorphic relations within the region. Metamorphic grade increases from west to east from biotite zone to staurolite zone over a distance of ca 0.5 km.

Three foliations have been observed, in addition to locally preserved compositional layering. S1 is preserved only locally as crenulations in Q-F domains. S2 is the dominant schistosity and is pervasive in all but the lowest grade samples. S3 is manifest as kink bands in biotite and garnet zone samples and as axial planes to late folds of S2 in staurolite grade samples.

Biotite zone samples contain small round chlorite pseudomorphs after an unknown precursor, but possibly garnet. Chloritization of garnet is nearly ubiquitous in garnet zone samples and into the staurolite zone. Above the staurolite isograd, clots of chlorite possibly pseudomorphed after staurolite are common and no relict staurolite was found within several tens of meters of the isograd. Further east, relic staurolite and garnet porphyroblasts altered first to sericite and later to chlorite are common. Unaltered samples are rare within 1 km of the staurolite isograd. In a few samples, porphyroblasts of staurolite overprint S1 and possibly S2 foliations, although some flattening of S2 around the porphyroblasts is also observed.

Chemical ages of monazite have been determined on three samples, one from the garnet zone, one from just within the staurolite zone and one several kms into the staurolite zone. Monazites from the two low-grade samples displayed mottled Y zoning whereas monazite from the highest grade sample displayed low-Y cores and moderate-Y rims. Calculated ages range from ca 350-400 Ma with no discernable differences between cores and rims. These ages are consistent with Acadian metamorphism culminating in the latest Devonian.

Session No. 39--Booth# 7

Petrology and Mineralogy (Posters)
Tuesday, 13 March 2007: 1:00 PM-4:45 PM
Geological Society of America Abstracts with Programs. Vol. 39, No. 1, p.86
© Copyright 2007 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.
Back to: Petrology and Mineralogy (Posters)
<< Previous Abstract | Next Abstract >>