Year of Publication

2006

Document Type

Thesis

College

Arts and Sciences

Department

Geology

First Advisor

David P. Moecher

Abstract

Detailed structural and petrographic analysis of the Greenbrier Fault (GBF) reveal different fold and fabric styles and generations preserved in the Great Smoky Group (GSG) hanging wall and Snowbird Group (SG) footwall. Four planar fabrics (S0, S1, S2, and S3) are completely overprinted within meters of the contact by shear zone-related fabrics. Bedding (S0) is defined by planar laminations in the SG siltstones. S1 is weak, not associated with folding of S0, and defined locally by sub-parallel alignment of biotite. S2 (slaty cleavage) is deflected into a disjunctive planar (in GSG) or continuous planar (in SG) S3 foliation characterized by mica formation and dynamic recrystallization of quartz. Metamorphic microstructures indicate lower greenschist to upper amphibolite facies Taconian metamorphism is syn- to post-S2, and pre-S3. Local lower greenschist facies retrograde metamorphism precedes S3 formation. A meter scale, ductile mesoscopic shear zone in SG at the GSG-SG contact is characterized by S/C fabric; this is the youngest deformational event and postdates retrograde mineral assemblages indicating postmetamorphic motion along the contact. Premetamorphic fault fabrics indicative of GSG thrusting onto the SG were absent or completely reconstituted during metamorphism and deformation. The Metcalf phyllite and Pigeon siltstone were also compared to test the hypothesis that the Metcalf phyllite is tectonized Pigeon siltstone. Major and trace element abundances are similar between the lithologies, with the exception of depletion of Ca, Na and Zr in the Metcalf. The system appears to have been open with respect to these elements. It is concluded that the Metcalf phyllite is the tectonized equivalent of the Pigeon siltstone based on lateral continuity, the strong macroscopic and microscopic resemblance of weakly deformed Metcalf to the Pigeon, similar mean values and ranges in major, minor, and trace elements, and identical rock densities.

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