Key Laboratory of Earth Probe and Geodynamics

Beijing, China

Key Laboratory of Earth Probe and Geodynamics

Beijing, China
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Lu Z.-W.,Chinese Academy of Geological Sciences | Lu Z.-W.,Key Laboratory of Earth Probe and Geodynamics | Gao R.,Chinese Academy of Geological Sciences | Gao R.,Key Laboratory of Earth Probe and Geodynamics | And 9 more authors.
Geology in China | Year: 2016

The Tibetan Plateau, which is made up of a number of terranes, has the world's most thick crust. There is a long-Term dispute concerning crustal thickness across the Bangong-Nujiang suture (BNS) from the Lhasa terrane to the Qiangtang terrane. This paper mainly reports the result of the study of deep seismic reflection profile in this area. A clear reflection of Moho was detected, which reveals the change of crustal thickness from the Lhasa terrane to the Qiangtang terrane. Moho exhibits a sharp decrease of 6.2 km across the BNS and becomes 12.5 km shallower from the northernmost Lhasa terrane to the south Qiangtang terrane at 28 km north of the BNS. The viewpoint based on deep seismic reflection data denies previous understanding of a 20 km offset.


Wang H.-Y.,Chinese Academy of Geological Sciences | Wang H.-Y.,Key Laboratory of Earth Probe and Geodynamics | Gao R.,Chinese Academy of Geological Sciences | Gao R.,Key Laboratory of Earth Probe and Geodynamics | And 9 more authors.
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2014

Subduction of the Indian plate underneath the Eurasian plate results in continuous uplift of the Qinghai-Tibet Plateau, whose formation not only led to tectonic deformation of the Asian continent in the late Cenozoic, but also affects landscape patterns of its peripheral areas. The northeast margin of Qinghai Tibet Plateau is the front position where the Qinghai Tibet plateau grows northeastward, and is also an important place of conversion where the India and Eurasia plate collision changes its direction from nearly north-south to northeast and east. In this study, we used deep seismic reflection profiles completed in 2004 and 2008, respectively. We spliced original shot gathers and used some key processing techniques and parameters to obtain a 400 km-long reliable section. This section reveals overall crustal structure and deformation style of the West Qinling orogenic belt and basins on its both sides. The results display the deep tectonic characteristics about the West Qinling orogenic thrust-napping toward the Ruoergai basin. The north-dipping and south-dipping strong reflections in the lower crust of the West Qinling and its south are considered as reflective patterns of the Yangtze and North China plate convergence under the West Qinling orogenic. Moho geometry and depth indicate the northeast margin of the Tibetan Plateau has experienced intense extension and thinning after the plateau strongly uplifted.


Wang H.,Chinese Academy of Geological Sciences | Wang H.,Key Laboratory of Earth Probe and Geodynamics | Gao R.,Chinese Academy of Geological Sciences | Gao R.,Key Laboratory of Earth Probe and Geodynamics | And 8 more authors.
Tectonophysics | Year: 2014

Underthrusting of India below Eurasia has resulted in the formation of the Himalayan and the Qinghai-Tibet Plateau. Distributed deformation coupled with block translation and rotation has generated the Qilian Shan thrust belt and a series of east- and northwest-striking strike-slip faults across northeastern Tibet. Because these structures lie in a transition zone between the high plateau region to the south and the lowlands of the North China craton in the north, determining their deep-crustal and upper-mantle structures has important implications for unraveling the mechanism of Tibetan plateau formation. In this paper, we present new results from the SinoProbe-02 deep seismic reflection project across the eastern part of the Qilian Shan and the southern margin of the Alxa block. Interpretation of the reflection profile obtained from this study is based on constraints from surface geology and detailed geometric analysis of structural relationships among key reflectors in the crust and the upper mantle. Our results indicate that the upper crust of the eastern Qilian Shan is characterized by fault-bend folds and duplex systems involving Phanerozoic strata that may have resulted from early Paleozoic collisional tectonics and Cenozoic intra-continental deformation. Locally, half-graben structures hosting Cretaceous strata are also present. The active structures in the region are dominated by left-slip Haiyuan and Tianjian fault systems marking the northern margin of the Tibetan plateau. The strike-slip structures have variable dips and dip directions and sole into a common décollement with a depth of 40-45. km. Because the two faults do not cut and offset the Moho below, the active crustal and mantle deformation in the northeastern Tibet must be decoupled. © 2014 Elsevier B.V.


Gao R.,Chinese Academy of Geological Sciences | Gao R.,Key Laboratory of Earth Probe and Geodynamics | Wang H.,Chinese Academy of Geological Sciences | Wang H.,Key Laboratory of Earth Probe and Geodynamics | And 12 more authors.
Tectonophysics | Year: 2014

The Songpan block in the northeastern Qinghai-Tibet Plateau (QTP) located at the junction of the E-W- and N-S-trending tectonic belts has affected the formation and evolution of the Chinese continent since Mesozoic and is a tectonic node in the central part of the Chinese continent. In this study, the Hezuo-Tangke deep seismic reflection profiling of the 257. km-long was conducted in 2004, which is the first profile across the Songpan block and the West Qinling orogen. We reprocessed the data in 2009, and the results revealed the fine lithosphere structure of the northern margin of the Songpan block and the West Qinling orogen. The results also revealed the connection between the Songpan block and East Kunlun-West Qinling orogeny, indicating that the Songpan block and the West Qinling orogen belong to the same stable continental block and that their lower crusts are both characterized by north-dipping strong reflectors, which provide seismic evidence for subduction of the lower crust of the Songpan block beneath the West Qinling orogen. We found that the sub-horizontal Moho reflectors beneath the West Qinling orogen indicate that it underwent intensive extension after collisional orogeny. The results of this study also indicate that the Kunlun fault did not cut off the Moho. Actually, it terminated at a sub-horizontal decollement in the lowermost crust of Tibet at a depth of ~. 35. km. The data provided through the investigation also are helpful in evaluating prospective oil and gas resources in the Songpan block. © 2014 Elsevier B.V.

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