Collision Tectonics between the Tarim Block(Basin)and the Northwestern Tibet Plateau:New Observations from a Multidisciplinary Geoscientific Investigation in the Western Kunlun Mountains  

作　　者：XIAO Xuchang LIU Xun GAO Rui Houn KAO LUO Zhaohua 

机构地区：[1]Institute of Geology,Chinese Academy of Geological Sciences [2]Institute of Earth Sciences,Academia Sinica,Taipei,China [3]China University of Geosciences

出　　处：《Acta Geologica Sinica(English Edition)》2001年第2期126-132,共7页地质学报（英文版）

基　　金：These research results are part of a key project carried out in 1997–2000,financially supported by the former Ministry of Geology and Mineral Resources(No.9501204 and 9501101);National Natural Science Foundation of China(No.F49734230);State Project 305 of the Xinjiang Uygur Autonomous Region(No.96-915-07).

摘　　要：New results from deep seismic reflection profiling, wide-angle reflection-refraction profiling and broadband seismic experiments reveal that a series of south-dipping reflectors occur on the southern margin of the Tarim block (basin). However, it is these south-dipping structures that are intercepted by another series of north-dipping reflectors at depths from 30 to about 150 km beneath the foreland of the W Kunlun Mountains. No evidence from the above geophysical data as well as geochemical and surface geological data indicate the southward subduction of the Tarim block beneath the W Kunlun Mountains (NW Tibet plateau), forming the so-called “two-sided subduction” model for the Tibet plateau as proposed by previous studies. So the authors infer that the tectonic interaction between the Tarim block and the W Kunlun block was chiefly affected by a “horizontal compression in opposite directions”, which brought about “face-to-face contact” between these two lithospheric blocks and led to the thickening, shortening and densifying of the lithosphere. Hence a “delamination” was formed due to the gravitational instability created by the thickening and densifying; then alkaline basic volcanic rocks (mainly shoshonite series) was erupted along the northern margin of the Tibet plateau owing to the delamination. This inference for the formation of the alkaline basic volcanics has been confirmed by recent geochemical and petrological studies in Tibet, indicating that different contacts control different magmatic activities: the alkali basalts are always developed in the “horizontal shortening boundary (contact)” on the northern margin of the Tibet plateau, while the muscovite granite and two-mica granite (leucogranite) in the “subductional contact” on the southern margin of the Tibet plateau.New results from deep seismic reflection profiling, wide-angle reflection-refraction profiling and broadband seismic experiments reveal that a series of south-dipping reflectors occur on the southern margin of the Tarim block (basin). However, it is these south-dipping structures that are intercepted by another series of north-dipping reflectors at depths from 30 to about 150 km beneath the foreland of the W Kunlun Mountains. No evidence from the above geophysical data as well as geochemical and surface geological data indicate the southward subduction of the Tarim block beneath the W Kunlun Mountains (NW Tibet plateau), forming the so-called “two-sided subduction” model for the Tibet plateau as proposed by previous studies. So the authors infer that the tectonic interaction between the Tarim block and the W Kunlun block was chiefly affected by a “horizontal compression in opposite directions”, which brought about “face-to-face contact” between these two lithospheric blocks and led to the thickening, shortening and densifying of the lithosphere. Hence a “delamination” was formed due to the gravitational instability created by the thickening and densifying; then alkaline basic volcanic rocks (mainly shoshonite series) was erupted along the northern margin of the Tibet plateau owing to the delamination. This inference for the formation of the alkaline basic volcanics has been confirmed by recent geochemical and petrological studies in Tibet, indicating that different contacts control different magmatic activities: the alkali basalts are always developed in the “horizontal shortening boundary (contact)” on the northern margin of the Tibet plateau, while the muscovite granite and two-mica granite (leucogranite) in the “subductional contact” on the southern margin of the Tibet plateau.

关 键 词：collision tectonics deep structure NW Tibet plateau 

分 类 号：P54[天文地球—构造地质学]