HR: 14:25h
AN: T13H-04    [Abstracts]
TI: Structural Development of the Eastern Kunlun Transpressional System, Central Tibet, China
AU: * McRivette, M W
EM: mmcrivet@ucla.edu
AF: Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, 595 Charles Young Drive East 3806 Geology Building, Los Angeles, CA 90095-1567, United States
AU: Yin, A
EM: yin@ess.ucla.edu
AF: Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, 595 Charles Young Drive East 3806 Geology Building, Los Angeles, CA 90095-1567, United States
AU: Chen, X
EM: xhchen@cags.net.cn
AF: Institute of Geomechanics, Chinese Academy of Geological Sciences, 11 Minzu Daxue Nan Road Haidian District, Beijing, 100081, China
AB: The Himalayan-Tibetan orogenic system is superposed on a vast area assembled throughout the Paleozoic and Mesozoic by collision of several discrete tectonic blocks. The Eastern Kunlun range in central Tibet coincides with the boundary between two of these tectonic terranes: the Songpan-Ganzi terrane to the south and the Eastern Kunlun-Qaidam block to the north. The former is characterized by thick, deformed Triassic flysch; the southern margin of the latter consists of Proterozic gneiss, Paleozoic-Mesozoic marine strata and volcanics, and early Paleozoic and Permian-Triassic granitic intrusions. Convergence between the two terranes was accommodated by northward subduction of the Songpan-Ganzi terrane, with suturing completed by the Early Jurassic. Tectonically, the Eastern Kunlun region comprises a large transpressional system consisting of the E-trending left-slip Kunlun fault and two thrust belts: the Qimen Tagh to the west and the Bayanhar to the east. The Kunlun fault is generally considered to have reactivated the Kunlun suture along much of its length. Each thrust belt is distinctly triangular-shaped, widening away from the central segment of the Kunlun fault. In the Qimen Tagh belt, north-dipping thrusts are expressed at the surface along the southern margins of individual ranges. In contrast, there is no major south-dipping structure along the northern flank of the Eastern Kunlun range. The thrusts are oriented obliquely to the Kunlun fault, trending WNW and merging with the Kunlun fault at an angle of approximately 20-30 degrees. To the west, the Kunlun fault terminates into WNW-trending thrusts and N-trending rifts. Taken together, these observations suggest that the transpressional system may have developed by propagating laterally: as the Kunlun fault extended by reactivating the Kunlun suture, obliquely-oriented thrust faults initiated to accommodate crustal shortening. The thrusts of the Qimen Tagh belt likely root into a regional detachment beneath Qaidam basin, with shortening in the Eastern Kunlun occurring above a tectonic wedge. The development of north-dipping thrusts may reflect the influence of pre-existing fabrics associated with the Kunlun suture which may have been similarly north-dipping.
DE: 8100 TECTONOPHYSICS
DE: 8110 Continental tectonics: general (0905)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting