The geological processes responsible for outward growth of the Tibetan Plateau are debated.The Qilian Mountains on the northeastern margin of the plateau comprise one of the youngest structural components of the plate...The geological processes responsible for outward growth of the Tibetan Plateau are debated.The Qilian Mountains on the northeastern margin of the plateau comprise one of the youngest structural components of the plateau whose understanding is key to deciphering the broader geological evolution of the region.Here,based on a reprocessed deep seismic profile which was originally collected during the 1990 s across the northeast margin of the western Qilian Mountains and previous geological and geophysical data,we find evidence for decoupled crustal deformation that was partitioned by a decollement,in which lowercrustal deformation featured by local duplexing preceded upper-crustal deformation featured by imbricate thrusts.Furthermore,we propose that the Asian lithospheric mantle is being underthrust beneath the western Qilian Mountains,as inferred from patterns of lower crustal deformation which is marked by the Moho geometry.Integrating these results yields a better understanding of lithospheric deformation of western Qilian Mountains,northeastern margin of the plateau during the Cenozoic.展开更多
The collision between the Indian and Asian plates uplifted the Himalayan-Tibetan Plateau,thickening and expanding the crust.It is a scientific mystery of global concern as how the two continents collide and how the co...The collision between the Indian and Asian plates uplifted the Himalayan-Tibetan Plateau,thickening and expanding the crust.It is a scientific mystery of global concern as how the two continents collide and how the continent-continent collision deforms the continent.Deep seismic reflection profile detection is one of the most effective ways to unlock this scientific mystery.For more than 20 years using this technology,we have detected fine structures of the thick crust of the Tibetan plateau after overcoming technical bottlenecks to access the lower crust and Moho thus revealing the continental collision processes.This paper systematically summarizes the deep behaviors of the India-Asia collision and subduction beneath the Tibetan Plateau,from south to north,east to west and further into the hinterland of the plateau.The Indian crust undergoes underthrusting beneath the Himalayan orogenic belt on the southern margin of the plateau.Meanwhile,the lithosphere of the Alxa block in the Asian plate subducts southward beneath the Qilian Mountain in the north of the plateau,driving the northward overthrusting of the Qilian crust.Additionally,the Tarim and West Kunlun blocks undergo face-to-face collision in the northwestern margin of the plateau.In the easternmost part of the plateau,the Longriba fault,instead of the Longmen Shan fault zone,marks the western margin of the Yangtze block.It is also seismically evidenced that the Moho geometry in the plateaus hinterland appears thin and flat,indicating lithospheric collapse and extrusion.Multiple deep reflection profiles revealed the collisional behavior under the Yalung-Zangbo suture zone and longitudinal variation in subducting geometry of the Indian crust from west to the east.In the middle of the suture zone,it shows a decoupling between the upper and lower crusts of the Indian plate,where the upper crust undergoes a northward overthrusting while the lower one experiences a northward underthrusting.It is also seismically evidenced a down-and southward crustal duplexing of the subducting Indian crust thickening the northern Himalayas,leaving over a thinning subducting lower crust of the Indian slab.The subduction front of the Indian crust collides with the lower crust of the Asian plate at the mantle depth.A near-vertical collision boundary is seen between the Gangdese batholith and the Tethyan Himalayas,where the Gangdese batholith shows almost transparent weak reflections in the lower crust with localized bright spot reflection that indicates partial melting.Additionally,the near-flat Moho geometry implies an extensional tectonic environment of the southern margin of the Asian plate.展开更多
Reversions as receiver functions and ACH were performed using the teleseismic data acquired from the seismic array that were deployed across Tian Shan in Xinjiang in 1997\|1998 jointly by Sino\|French seismic crew.The...Reversions as receiver functions and ACH were performed using the teleseismic data acquired from the seismic array that were deployed across Tian Shan in Xinjiang in 1997\|1998 jointly by Sino\|French seismic crew.The results suggest the crustal shortening and thickening in the study area that are well expressed by the thickening in lower crust and the uplifting of Tian Shan in the collision between Euro\|Asian and Indian plates. Underthrusting in the intra\|continental collision model turns out to be asymmetrical, with the northward in the south much stronger than the southward in the north. The cause of the steepness of the southward underthrust is likely to rest on the strong extrusion. Going further deep, the curving end of the cold underthrusting zone may detach, penetrating its own way. The ongoing uplifting of Tian Shan is given birth mostly by the underthrusting on its south and the squeezing force from both sides. The underthrusting zone is composed of compact ancestral crystalline rocks. The thickness of the crust varys from 65km beneath the main body of Tian Shan to 41km beneath the Tarim and Zengar basins on sides with certain degree of thickening. The major faulting zones in the area go precipitously in the scope of crust, with those in the low\|velocity bodies closely associated to the activities of molten mantle materials and seismicity.展开更多
基金funded by the National Natural Science Foundation of China(Grant Nos.41904083,41430213,41590863,and 41774114)the Science and Technology Foundation of the Guangxi Province(Grant No.2018GXNSFAA138063)。
文摘The geological processes responsible for outward growth of the Tibetan Plateau are debated.The Qilian Mountains on the northeastern margin of the plateau comprise one of the youngest structural components of the plateau whose understanding is key to deciphering the broader geological evolution of the region.Here,based on a reprocessed deep seismic profile which was originally collected during the 1990 s across the northeast margin of the western Qilian Mountains and previous geological and geophysical data,we find evidence for decoupled crustal deformation that was partitioned by a decollement,in which lowercrustal deformation featured by local duplexing preceded upper-crustal deformation featured by imbricate thrusts.Furthermore,we propose that the Asian lithospheric mantle is being underthrust beneath the western Qilian Mountains,as inferred from patterns of lower crustal deformation which is marked by the Moho geometry.Integrating these results yields a better understanding of lithospheric deformation of western Qilian Mountains,northeastern margin of the plateau during the Cenozoic.
文摘The collision between the Indian and Asian plates uplifted the Himalayan-Tibetan Plateau,thickening and expanding the crust.It is a scientific mystery of global concern as how the two continents collide and how the continent-continent collision deforms the continent.Deep seismic reflection profile detection is one of the most effective ways to unlock this scientific mystery.For more than 20 years using this technology,we have detected fine structures of the thick crust of the Tibetan plateau after overcoming technical bottlenecks to access the lower crust and Moho thus revealing the continental collision processes.This paper systematically summarizes the deep behaviors of the India-Asia collision and subduction beneath the Tibetan Plateau,from south to north,east to west and further into the hinterland of the plateau.The Indian crust undergoes underthrusting beneath the Himalayan orogenic belt on the southern margin of the plateau.Meanwhile,the lithosphere of the Alxa block in the Asian plate subducts southward beneath the Qilian Mountain in the north of the plateau,driving the northward overthrusting of the Qilian crust.Additionally,the Tarim and West Kunlun blocks undergo face-to-face collision in the northwestern margin of the plateau.In the easternmost part of the plateau,the Longriba fault,instead of the Longmen Shan fault zone,marks the western margin of the Yangtze block.It is also seismically evidenced that the Moho geometry in the plateaus hinterland appears thin and flat,indicating lithospheric collapse and extrusion.Multiple deep reflection profiles revealed the collisional behavior under the Yalung-Zangbo suture zone and longitudinal variation in subducting geometry of the Indian crust from west to the east.In the middle of the suture zone,it shows a decoupling between the upper and lower crusts of the Indian plate,where the upper crust undergoes a northward overthrusting while the lower one experiences a northward underthrusting.It is also seismically evidenced a down-and southward crustal duplexing of the subducting Indian crust thickening the northern Himalayas,leaving over a thinning subducting lower crust of the Indian slab.The subduction front of the Indian crust collides with the lower crust of the Asian plate at the mantle depth.A near-vertical collision boundary is seen between the Gangdese batholith and the Tethyan Himalayas,where the Gangdese batholith shows almost transparent weak reflections in the lower crust with localized bright spot reflection that indicates partial melting.Additionally,the near-flat Moho geometry implies an extensional tectonic environment of the southern margin of the Asian plate.
文摘Reversions as receiver functions and ACH were performed using the teleseismic data acquired from the seismic array that were deployed across Tian Shan in Xinjiang in 1997\|1998 jointly by Sino\|French seismic crew.The results suggest the crustal shortening and thickening in the study area that are well expressed by the thickening in lower crust and the uplifting of Tian Shan in the collision between Euro\|Asian and Indian plates. Underthrusting in the intra\|continental collision model turns out to be asymmetrical, with the northward in the south much stronger than the southward in the north. The cause of the steepness of the southward underthrust is likely to rest on the strong extrusion. Going further deep, the curving end of the cold underthrusting zone may detach, penetrating its own way. The ongoing uplifting of Tian Shan is given birth mostly by the underthrusting on its south and the squeezing force from both sides. The underthrusting zone is composed of compact ancestral crystalline rocks. The thickness of the crust varys from 65km beneath the main body of Tian Shan to 41km beneath the Tarim and Zengar basins on sides with certain degree of thickening. The major faulting zones in the area go precipitously in the scope of crust, with those in the low\|velocity bodies closely associated to the activities of molten mantle materials and seismicity.
