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Teleseismic shear wave splitting and intracontinental collision deformation of the northern Tibetan Plateau and the eastern Tarim basin

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Science China Earth Sciences 2023年第7期66卷 1556-1568页

作者： Lijun CHANG Chunyong WANG Institute of Geophysics China Earthquake AdministrationBeijing 100081China

Shear wave splitting measurement of teleseismic data has been used to determine the fast polarization directions and delay times for 38 temporary stations and 15 permanent stations from a NW linear seismic array across the eastern Tarim basin(ETB) and the northern Tibetan Plateau(NTP),and 10 permanent stations on both sides of the array.We present an image of upper mantle anisotropy in the ETB and NTP using the 63 new measurements.The results show that the fast directions and delay times have complex spatial distribution characteristics.The delay times within the interior of the Tarim basin are very small,with an average value of 0.6 s,which is not only smaller than that in the Altyn Tagh fault and Tianshan on the southern and northern margins of the basin,but also smaller than that in the NTP,reflecting that the delay time of stable blocks is smaller than that of active blocks.Along the array,from east to west,the fast directions contrarotate from NNW in the southern Songpan-Garze terrane to NW in the northern Songpan-Garze terrane,to near E-W or ENE in the north of the East Kunlun fault and southern margin of the Qaidam basin,then first abruptly rotate to NW in the Qiman Tagh fault on the northwestern margin of the Qaidam basin,second abruptly rotate to ENE in the Altyn Tagh fault and south of the ETB,and third abruptly rotate to NW in the north of the ETB,then finally rotate to WNW in the Tianshan.The comparative analysis between the fast wave directions measured by shear wave splitting and predicted from the surface deformation field shows that,with the exclusion of the five observations with larger misfits within the interior of the ETB(with an average misfit of 27°),the misfits in the NTP and northern and southern margins of the Tarim basin are relatively small(with an average misfit of 9°).In addition,the fast wave directions of the tectonic units such as the Altyn Tagh fault,East Kunlun fault,and Tianshan are parallel to the strikes of faults and mountains in the region,which indicates that the deep and s

关键词： Northern Tibetan Plateau Eastern Tarim basin Altyn Tagh fault East Kunlun fault lithospheric deformation

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Three-dimensional thermo-rheological structure of the lithosphere in the North China Craton determined by integrating multiple observations: Implications for the formation of rifts

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Science China Earth Sciences 2020年第7期63卷 969-984页

作者： Kai WANG Xiong XIONG Yuming ZHOU Yashan FENG State Key Laboratory of Geodesy and Earth’s Dynamics Institute of Geodesy and GeophysicsChinese Academy of SciencesWuhan 430074China Institute of Geophysics and Geomatics China University of GeosciencesWuhan 430074China Department of Earth and Atmospheric Sciences Saint Louis UniversityMO 63108USA

The lithosphere of the North China Craton(NCC)has experienced significant destruction and deformation since the Mesozoic,a notable feature of which is the widespread extensional structure and lithospheric thinning in the eastern NCC.Since the thermo-rheological structure of the lithosphere is one of the main factors controlling these dynamic processes,a threedimensional thermo-rheological model of the present lithosphere in the NCC was developed based on a geophysical-petrological method using a variety of data,and its relationship with the extensional structures and the formation of rifts was further analyzed.Our results show that the western NCC is characterized by thick lithosphere,low Moho temperature(TMoholithospheric strength and mantle-crust strength ratio(Sm/Sc>1).The deformation of the western narrow rift is consistent with the localized deformation dominated by the strength of lithospheric mantle.On the other hand,the lithosphere in the eastern NCC is characterized by extensive thinning(with lithospheric thickness of about 80–110 km).However,the decrease of lithospheric strength is not uniform,with high strength(10×1012 Pa m)observed in some areas(such as the Bohai Bay Basin and Hehuai Basin).Most of the eastern lithosphere is characterized by high TMoho(600–750°C)and low Sm/Sc(deformation dominated by crustal strength,which eventually evolved into a series of wide rifts.However,the cooling and accretion of the lithosphere in the subsequent stages significantly increased the strength of the lithospheric mantle,resulting in the inconsiste

关键词： North China Craton Thermal structure Rheological structure lithospheric deformation Rift

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Large along-axis variations in magma supply and tectonism of the Southeast Indian Ridge near the Australian-Antarctic Discordance

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Acta Oceanologica Sinica 2020年第1期39卷 118-129页

作者： Shoujin Liu Jian Lin Zhiyuan Zhou Fan Zhang Key Laboratory of Ocean and Marginal Sea Geology South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301China University of Chinese Academy of Sciences Beijing 100049China Department of Geology and Geophysics Woods Hole Oceanographic InstitutionWoods HoleMA 02543USA Innovation Academy of South China Sea Ecology and Environmental Engineering Chinese Academy of SciencesGuangzhou 523936China

We analyzed seafloor morphology and geophysical anomalies of the Southeast Indian Ridge(SEIR) to reveal the remarkable changes in magma supply along this intermediate fast-spreading ridge. We found systematic differences of the Australian-Antarctic Discordance(AAD) from adjacent ridge segments with the residual mantle Bouguer gravity anomaly(RMBA) being more positive, seafloor being deeper, morphology being more chaotic, M factors being smaller at the AAD. These systematic anomalies, as well as the observed Na8.0 being greater and Fe8.0 being smaller at AAD, suggest relatively starved magma supply and relatively thin crust within the AAD.Comparing to the adjacent ridges segments, the calculated average map-view M factors are relatively small for the AAD, where several Oceanic Core Complexes(OCCs) develop. Close to 30 OCCs were found to be distributed asymmetrically along the SEIR with 60% of OCCs at the northern flank. The OCCs are concentrated mainly in Segments B3 and B4 within the AAD at ~124°–126°E, as well as at the eastern end of Zone C at ~115°E. The relatively small map-view M factors within the AAD indicate stronger tectonism than the adjacent SEIR segments.The interaction between the westward migrating Pacific mantle and the relatively cold mantle beneath the AAD may have caused a reduction in magma supply, leading to the development of abundant OCCs.

关键词： Oceanic Core Complexes magma supply Southeast Indian Ridge lithospheric deformation Australian-Antarctic Discordance

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