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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The Fries Fault near Riner, Virginia: an example of a polydeformed, ductile deformation zone

Kaygi, Patti Boyd January 1979 (has links)
The Fries Fault, a 1.2-2.3 km wide zone near Riner, is a major tectonic discontinuity in the Blue Ridge geologic province, characterized by progressive stages of continuous ductile deformation. Trending northeast with a shallow to moderate southeast dip, this fault juxtaposes Little River Gneiss on the southeast against Pilot Gneiss and the Chilhowee Formation to the northwest. A 0.8-1.2 km wide subzone of protomylonite within the Little River Gneiss grades into a 0.5-1.0 km wide mylonite subzone, the latter containing narrow bands of phyllotactic ultramylonite ranging in width from centimeters to tens of meters. Mylonitization is reflected by a marked reduction in grain size, elongation of quartz and fracturing of feldspar, all concomitant with the development of a mylonitic foliation (S<sub>m</sub>). Ductile deformation processes involving grain elongation, recovery and recrystallization, combined with chemical processes (primarily pressure solution), are the dominant strain-accommodation mechanisms in the formation of S<sub>m</sub>. Rocks within the fault zone have undergone four phases of Paleozoic deformation. An early S₁ foliation has been nearly completely transposed by S<sub>m</sub>(S₂), which dominates across most of the area. The development of S<sub>m</sub> was accompanied by a retrogressive metamorphism that altered basement rocks from lower amphibolite to greenschist facies. Chilhowee Group rocks remained at lower greenschist facies. Post-faulting deformation produced an S₃ crenulation cleavage associated with northeast trending, overturned F₃ folds. Subsequent refolding produced open, northwest trending F₄ folds. Although the bulk deformation is progressive simple shear, flattening is increasingly dominant during the later stages of deformation. / Master of Science

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