Superficial and Deep Structure of Central Asia as Example of Continental Lithosphere Heterogeneity

Abstract

The north part of central Asia belongs to the north Eurasian lithosphere plate separated from neighboring plates by some transit zones. These zones consist of numerous crust blocks limited by active faults and interblock zones, in which maximal volumes of the seismic energy release. The examination of different geophysical fields of central Asia shows that interblock zones coincide with some anomalies in magnetic and partly gravity fields. Heat-flow values increase up to 80-100 μW/m -2 and more in interblock zones in boundaries of Hangay, Amurian, Tibet's, and Tarim blocks as well as in some inner continental rifts. Some of heat-flow anomalies can be connected with mantle plumes under Hangay and north part of the Amurian Block. Within the central Asian transit zone the up-to-date tectonic compression distinctly predominates, while in the east Asian zone it changes partly on extension and slipping with extension. The crust thickness changes from 25-30 km in the east of central Asia up to 50-75 km in the west under Tibet and neighboring blocks. The lithosphere thickness changes in the same direction from 60-80 km up to 120-150 km, but it decreases up to 100 km and less under inner continental rifts coinciding with interblock zones. The direction of the P-and S-waves anisotropy shows within the great part of the region the coupling deformation in the lithosphere upper mantle and crust. But east of the east Himalayan syntax differently directed vectors of horizontal displacement are established in the crust and upper mantle indicating decoupling these layers under the influence of the Hindustan-Asia collision and "a threshold" of the SE China thick lithosphere, coinciding with the interblock zone between SE China and Tibet's blocks. The majority of above-mentioned geophysical and geological data prove the heterogeneity of the central Asia lithosphere and its direct connection with interblock zones.

Central Asian Geodynamic Regimes West and East 102–104° Geodivider

“…-построение графиков диссипации сейсмической энергии и глубинных сейсмических разрезов через геораздел и транзитные зоны по методике, разработанной авторами в 2015-2018 гг. [Gatinsky, Prokhorova, 2015;Gatinsky et al, 2018] [Gatinsky, Prokhorova, 2014].…”

“…Границы блоков в пределах Центрально-Азиатской транзитной зоны характеризуются повышенной тектонической и сейсмической активностью, приуроченной к относительно узким (50-100 км) межблоковым зонам. Они были впервые выделены в работе [Gatinsky et al, 2009], позднее неоднократно уточнялись [Gatinsky et al, 2011;Gatinsky, Prokhorova, 2014, 2015. Эти зоны частично близки к «мобильным зонам континентальной литосферы» [Seminskii, 2008] и к «зонам современной деструкции литосферы» [Sherman, Zlogodukhova, 2011].…”

Crustal strain and seismic hazard of the NE Tibetan Plateau

“…Both idealised models only fit surface observations to some extent, with the block model focused on the slip rates on the major faults (Tapponnier et al, 2001a) and the continuum model focused on the long-wavelength deformation pattern (England and Molnar , 2005). The heterogeneous strength of the continental lithosphere, due to its complex tectonic and petrological history as well as the temperature and pressure conditions it is under (Vauchez et al, 1998;Ziegler et al, 1998;Mo et al, 2006;Gatinsky and Prokhorova, 2014), means the real system most likely lies somewhere in between these two end members.…”