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dc.contributor.authorFrancsis, Matthew Keeganen
dc.date.accessioned2014-03-14T20:34:58Zen
dc.date.available2014-03-14T20:34:58Zen
dc.date.issued2012-04-20en
dc.identifier.otheretd-05032012-162325en
dc.identifier.urihttp://hdl.handle.net/10919/32170en
dc.description.abstractDynamically recrystallized quartz microstructure and grainsize evolution along mid-crustal shear zones allows for the estimation of tectonic driving stresses and strain rates acting in the mid-crust. Quartz-rich tectonites from three exhumed mid-crustal shear zones, the Main Central Thrust (MCT; Sutlej valley, NW India), South Tibetan Detachment System (STDS; Rongbuk valley, S Tibet), and Moine thrust (NW Scotland), were analyzed. Deformation temperatures estimated from quartz microstructural and petrofabric thermometers indicate steep apparent thermal gradients (80–420 °C/km) across 0.5–2.3 km thick sample transects across each shear zone. Quartz recrystallization microstructures evolve from transitional bulging/sub-grain rotation to dominant grain boundary migration at ~ 200 m structural distance as traced away from each shear zone. Optically measured quartz grainsizes increase from ~ 30 μm nearest the shear zones to 120+ μm at the largest structural distances. First-order Zener space analysis across the Moine nappe suggests strong phyllosilicate control on recrystallized quartz grainsize. Recrystallized quartz grainsize piezometry indicates that differential stress levels sharply decrease away from the shear zones from ~ 35 MPa to 10 MPa at ~ 200 m structural distance. Strain rates estimated with quartz dislocation creep flow laws are tectonically reasonable, between 10⁻¹² – 10⁻¹⁴ s⁻¹. Traced towards each shear zone strain rate estimates first decrease one order of magnitude before rapidly increasing one to two orders of magnitude at structural distances of ~ 200 m. This kinked strain rate profile is likely due to the steep apparent thermal gradients and relatively constant differential stress levels at large structural distances.en
dc.publisherVirginia Techen
dc.relation.haspartFrancsis_MK_T_2012.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectMoine Thrusten
dc.subjectMain Central Thrusten
dc.subjectquartz piezometryen
dc.subjectflow lawen
dc.subjectGreater Himalayan Seriesen
dc.subjectSouth Tibetan Detachment Systemen
dc.titlePiezometry and Strain Rate Estimates Along Mid-Crustal Shear Zonesen
dc.typeThesisen
dc.contributor.departmentGeosciencesen
dc.description.degreeMaster of Scienceen
thesis.degree.nameMaster of Scienceen
thesis.degree.levelmastersen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.disciplineGeosciencesen
dc.contributor.committeechairLaw, Richard D.en
dc.contributor.committeememberSpotila, James A.en
dc.contributor.committeememberCaddick, Mark J.en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-05032012-162325/en
dc.date.sdate2012-05-03en
dc.date.rdate2012-05-21en
dc.date.adate2012-05-21en


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