THE LITHOSPHERIC STRUCTURE OF THE CENTRAL AND SOUTHERN TIEN SHAN: MTS DATA CORRELATED WITH PETROLOGY AND LABORATORY STUDIES OF LOWER-CRUST AND UPPER-MANTLE XENOLITHS
V.Yu. Bataleva, E.A. Batalevaa, V.V. Egorovab, V.E. Matyukova, and A.K. Rybina
aResearch Station of the Russian Academy of Sciences, Bishkek, 720049, Kyrgyzstan
bV.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
Keywords: Magnetotelluric soundings (MTS), crustal conductors, seismic velocities, geothermobarometry, Tarim, Tien Shan, At-Bashi accretionary-collisional zone, Issyk-Kul microcontinent
Pages: 1592-1599
Abstract
Magnetotelluric soundings (MTS) in the Kyrgyz Tien Shan along 74? and 76?E profiles reveal conductors in the crust which delineate the boundaries of the At-Bashi accretionary-collisional zone and the Issyk-Kul microcontinent. Correlated to earthquake converted-wave patterns ( v P) along the MANAS profile collected in 2007, the geoelectric model for the At-Bashi zone lends support to the hypothesis that the position and dip of large thrust sheets, as well as the way and direction of exhumation of eclogites in this zone, are similar to those in northwestern China. Petrological analysis, geothermobarometry, and elastic P -wave velocities measured in laboratory on lower-crust and upper-mantle xenoliths indicate that at the time when the xenoliths were dragged to the surface at ~70 Ma, the Moho was 20 km shallower than now (35 km against 55 km) and the heat flux was 20 mW/m2 higher (80 against 60 mW/m2).
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