Date of Degree Completion
Master of Science (MS)
Second Committee Member
Third Committee Member
Mabja Dome, southern Tibet, exposes mid-crustal rocks proposed to have originated from a southward flowing mid-crustal channel. Kinematic, mean kinematic vorticity (Wm), and metamorphic petrography analyses on these mid-crustal rocks were performed to test this hypothesis. Kinematic indicators show a transition with structural depth from top-north and top-south shear to solely top-south shear. Along the northernmost transects, Wm in schists and orthogneisses range from 0.52–0.84 (63–36% pure shear). Wm for quartzites ranges from 0.9–0.99 (27–1% pure shear). Deformation temperatures increase from ~450 °C in the chloritoid-zone to ~700 °C in the sillimanite-zone and were recorded between ~35–16 Ma. These patterns exhibit a complex flow regime characterized by: (1) opposing shear sense driven by heterogeneous viscosity and/or channel thickness, (2) broad top-south shear along the Main Central Thrust, (3) simple shear partitioned into weaker quartzite horizons, and (4) an increase in lithostatic load with depth.
Langille, Jackie, "Middle Crustal Ductile Deformation Patterns in Southern Tibet: Insights from Vorticity Studies in Mabja Dome" (2008). All Master's Theses. 1418.