Abstract
A quasi-linear zone of noticeable geological and geophysical changes, which coincides approximately with 102–103° E meridians, is termed by the authors as “geodivider”. Active submeridional faults are observed predominantly along the zone and coincide with its strike. Seismicity is most intensive in the central part of this zone, from the Lake Baikal to the Three Rivers Region at the Sino-Myanmar frontier. Transects with deep seismic sections and energy dissipation graphs show most sharply increasing seismic energy amounts and hypocenter depths in the western part of the geodivider which delimits (in the first approximation) the Central Asian and East Asian transitional zones between the North Eurasian, Indian and Pacific lithosphere plates. The transpression tectonic regime dominates west of the geodivider under the influence of the Hindustan Indentor pressure, and the transtension regime prevails east of it due to the Pacific subduction slab submergence and continuation. The regime change coincides with an abrupt increase in the crust thickness – from 35–40 km to 45–70 km – west of the geodivider, as reflected in the geophysical fields and metallogenic characteristics of the crust. The direction ofP- andS-waves anisotropy together with the GPS data show decoupling layers of the crust and mantle in the southern part of the geodivider. According to our investigations, the 102–103° E geodivider is a regional geological-geophysical border that may be compared with the Tornquist Line, and, by its scale, with the Uralian and Appalachian fronts and some others large structures.
Highlights
The 102–103° E geodivider “neighbours” the VEBIRS Zone identified by geologists from Irkutsk in the 1970s [Komarov et al, 1978]
- Construction of the deep seismic sections based on the CMT data and the graphs of energy dissipation based on the NEIC data along the transects across the geodivider and the adjacent blocks;
Within the Indochina Peninsula, the 102–103° E geodivider goes along the sharp west margin of the Indosinian Massif and coincides with some active eastward thrusts and slips of the sub-longitudinal strike [Gatinsky, 2005]
Summary
A quasi-linear zone of noticeable geological changes tracing across Eurasia clearly stands out on the Electronic Geodynamic Globe (http://earth.jscc.ru) created in the Vernadsky State Geological Museum in Moscow. Active faults are observed predominantly along the zone and coincide with its strike. The 102–103° E geodivider is one of the most important tectonic structures in Central Asia Throughout its extent it includes on the surface, especially in its central part, seismically active submeridional faults, and, in depth, sharp gradients of the crust and lithosphere thickness, gravimetric steps, changing velocities of P-waves in the upper mantle and developing low-velocity zones within the lower and middle crust. The geodivider delimits two main transitional zones, Central Asian (in the west) and East Asian. The former is located between North-Eurasian and Indian plates and characterized by the transpression regime with predomination thrusts and slips. Geodynamics & Tectonophysics 2018 Volume 9 Issue 3 Pages 989–1006 tics and the deep anomalies, as well as clarifying the main causes of different regimes at the geodivider sides
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