Title page for ETD etd-11012008-063059


Type of Document Master's Thesis
Author Holmstad, Erin Frances
URN etd-11012008-063059
Title Geochemical and petrologic study of the Fries-Rockfish Valley Fault near Roanoke, Virginia
Degree Master of Science
Department Geology
Advisory Committee
Advisor Name Title
Tracy, Robert J. Committee Chair
Bodnar, Robert J. Committee Member
Henika, William S. Committee Member
Keywords
  • geochemistry
  • shear
  • metamorphic petrology
Date of Defense 1996-05-15
Availability restricted
Abstract
The Blue Ridge Province in southern and central Virginia is a complex slice of Precambrian basement emplaced on the margin of Laurentia during collisional events in the Paleozoic. This allochthonous basement is composed of Middle Proterozoic continental crust, Late Proterozoic intrusives, and Late Proterozoic-early Paleozoic metasediments and metavolcanics. Two distinct terranes within the Blue Ridge are separated by the northeasttrending and southeast dipping Fries-Rockfish Valley Fault Zone, exposed as a 1-10 km wide shear zone, formed during the middle Paleozoic Taconic Orogeny (425-450 Ma.).

These terranes are referred to as the Pedlar massif, a high-grade granulite terrane, to the northwest and the Lovingston massif, a lower-grade amphibolite terrane to the southeast. The connection between these terranes has been debated for decades.

A combined petrologic and geochemical approach has been applied in two transects across the shear zone, four kilometers apart along strike near Roanoke, Virginia, to study the geochemical and petrologic evidence of shearing along the fault and constrain the nature and timing of possible retrogressive and fluid infiltration events that affected these rocks. Mineral assemblages and microstructures at the northeastern Horsepen Mountain and at the southwestern Explore Park transects indicate that deformation occurred along the fault under greenshist facies conditions.

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