HR: 13:55h
AN: T13H-02    [Abstracts]
TI: Structural and Thermochronological Constraints on the Coupling Between Exhumation, Denudation and Tectonics in the Himalaya: Insights From the Ama Drime Massif, Tibet- Nepal
AU: * Jessup, M J
EM: mjessup@utk.edu
AF: University of Tennessee, Dept. of Earth & Planetary Sciences, Knoxville, TN 37996, United States
AU: Cottle, J M
EM: John.Cottle@earth.ox.ac.uk
AF: University of Oxford, Dept. of Earth Sciences, Oxford, OX1 3PR, United Kingdom
AU: Newell, D L
EM: dennis.newell@comcast.net
AF: Los Alamos National Laboratory, Hydrology, Geochemistry, and Geology Group, Los Alamos, NM 87545, United States
AU: Berger, A L
EM: alberger@vt.edu
AF: Virginia Tech, Dept. of Geosciences, Blacksburg, VA 24061, United States
AU: Spotila, J A
EM: spotila@vt.edu
AF: Virginia Tech, Dept. of Geosciences, Blacksburg, VA 24061, United States
AB: Focused denudation and mid-crustal flow are coupled in many active tectonic settings, including the Himalaya where exhumation of mid-crustal rocks is accommodated by thrust faults and low-angle detachment systems during crustal shortening. New structural data demonstrates that the most recently active tectonic feature in the Mt. Everest region is the Ama Drime Massif (ADM), a trans-Himalayan antiformal structure that protrudes ~ 70 km north from the crest of the Himalaya and displaces the South Tibetan Detachment system. Previous investigations interpreted the N-S striking shear zones and fault systems that bound either side of the ADM as the Main Central thrust. Our data show that these are 100-300 m thick normal-sense shear zones that are kinematically linked to young brittle faults that offset Quaternary deposits and record active E-W extension. Geochemical tracers in hot springs along the western shear zone indicate devolatilization of crustal rocks suggesting active metamorphism and/or melting beneath the ADM. Integration of high-to low-T thermochronometric methods, including U(-Th-)Pb, Apatite Fission Track and (U-Th)/He, yield important information regarding the timing and rate of exhumation of the ADM. These data reveal that rapid exhumation of material from the mid-crust during E-W extension began in the mid-Miocene and that a high rate of uplift / denudation persisted into the Pliocene. The southern end of the ADM is centered on the Arun River gorge, which previous geomorphological instigations defined as a prime candidate for climate-tectonic coupling. We combine our results with these exiting data to propose that active exhumation of deep crustal rocks of the ADM during E-W extension is coupled with denudation in the Arun River gorge. This model provides important quantitative constraints on the dynamic feedbacks between climate and tectonics in collisional orogens as well as the evolution of trans-Himalayan rivers and antiformal structures.
DE: 8012 High strain deformation zones
DE: 8107 Continental neotectonics (8002)
DE: 8110 Continental tectonics: general (0905)
DE: 8135 Hydrothermal systems (0450, 1034, 3017, 3616, 4832, 8424)
DE: 8177 Tectonics and climatic interactions
SC: Tectonophysics [T]
MN: 2007 Fall Meeting