HR: 1340h
AN: T43B-1357    [Abstracts]
TI: Deep Structure and Tectonic Evolution of the Basins of Northwestern China
AU: * Knepprath, N
EM: nknepprath@usgs.gov
AF: US Geological Survey, 345 Middlefield Rd. MS 977, Menlo Park, CA 94025, United States
AU: Mooney, W D
EM: mooney@usgs.gov
AF: US Geological Survey, 345 Middlefield Rd. MS 977, Menlo Park, CA 94025, United States
AU: Okaya, N
EM: nihalok@hotmail.com
AF: US Geological Survey, 345 Middlefield Rd. MS 977, Menlo Park, CA 94025, United States
AB: Northwest China contains a system of large sedimentary basins that include the Tarim, Qaidam, and Junggar. These basins are situated adjacent to the Tibetan Plateau and exhibit basements with contrasting evolutionary histories. Here we review three wide-angle seismic reflection/refraction profiles across these basins and their tectonic implications. The profiles include (1) a 1,400 km transect extending from the northern margin of the Tarim Basin to the eastern margin of the Qaidam Basin crossing the Altyn Tagh Range, (2) a 300 km transect extending from the northern to the southern margins of the Qaidam Basin, and (3) a 600 km transect extending from the northwestern to the southwestern margins of the Junggar Basin. The crustal structure of the Tarim Basin is interpreted as a typical stable continental platform. The seismic velocity boundaries between the felsic upper, intermediate middle, and mafic lower crust display clear divisions. Conversely, the Qaidam Basin, which lies at an elevation of ~3,000 m above sea level, is more similar to the soft deforming crust of the Tibetan Plateau. This crust is more felsic and lacks a high velocity mafic lower crust. Crustal structure of the Junggar basement includes a mix of oceanic materials and older blocks. Average crustal thicknesses are 55 km for the Tarim, 60 km for the Qaidam, and 50 km for the Junggar and the average seismic velocities are 6.0 km/s, 5.8 km/s, and 6.3 km/s (respectively). Of the three basins described, the Junggar is the thinnest and has the highest velocity.
DE: 1219 Gravity anomalies and Earth structure (0920, 7205, 7240)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
DE: 8124 Earth's interior: composition and state (1212, 7207, 7208, 8105)
DE: 8125 Evolution of the Earth (0325)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting