Objective Xining basin is located in the northeastern Qinghai- Tibetan Plateau, which tectonic location belongs to a junction of the Kunlun and Qilian mountains. The southern, northern and western parts of the basin a...Objective Xining basin is located in the northeastern Qinghai- Tibetan Plateau, which tectonic location belongs to a junction of the Kunlun and Qilian mountains. The southern, northern and western parts of the basin are restricted by the Laji, Daban and Riyue mountains fault zones, and go eastward into the Longzhong basin in Gansu Province. A succession of Cenozoic lacustrine sedimentary strata has been well developed in the Xining basin, with sediments over 800 m thick.展开更多
The Qaidam Basin in the NE Tibetan Plateau has contributed the largest amount of potash in China.However,how the potash was formed has long been a subject of debate.Here we carried out a deep drilling
After the 2015 M_S8. 1 Nepal earthquake,a strong and moderate seismicity belt has formed in Tibet gradually spreading along the northeast direction. In this paper,we attempt to summarize the features and investigate t...After the 2015 M_S8. 1 Nepal earthquake,a strong and moderate seismicity belt has formed in Tibet gradually spreading along the northeast direction. In this paper,we attempt to summarize the features and investigate the primary mechanism of this behavior of seismic activity,using a 2-D finite element numerical model with tectonic dynamic settings and GPS horizontal displacements as the constraints. In addition,compared with the NEtrending seismicity belt triggered by the 1996 Xiatongmoin earthquake,we discuss the future earthquake hazard in and around Tibet. Our results show that: the NE-directed seismicity belt is the response of enhanced loading on the anisotropic Qinghai-Tibetan plateau from the Indian plate and earthquake thrusting. Also,this possibly implies that a forthcoming strong earthquake may fill in the gaps in the NE-directed seismicity belt or enhance the seismic hazard in the eastern( the north-south seismic zone) and western( Tianshan tectonic region) parts near the NE-directed belt.展开更多
The Eastern Kunlun Mountains play an important role in the growth and eastward extrusion of the Tibetan Plateau. Tectonic and sedimentary study of the Cenozoic Qaidam Basin, especially the southern part, provides key ...The Eastern Kunlun Mountains play an important role in the growth and eastward extrusion of the Tibetan Plateau. Tectonic and sedimentary study of the Cenozoic Qaidam Basin, especially the southern part, provides key evidence for understanding their evolution. Here we present evidence including isopach maps, seismic sections and sedimentary analysis of single well to illustrate the sedimentary development of the basin and the structural features of its southern margin. The Qaidam Basin extended across Qiman Tagh-Eastern Kunlun Mountains in the early Cenozoic and withdrew northward at ca. 35.5 Ma, and then buckled as an EW striking elliptical depression since ca. 14.9 Ma, with the main depocenter migrating eastward. Our results support the view that the Kumukol and Hoh Xil basins joined the Qaidam Basin in the early Cenozoic time and we propose the Eastern Kunlun Mountains uplifted in the mid-Miocene.展开更多
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
Based on observations from a dense broadband seismic array located along the northeastern (NE) margin of the Tibetan Plateau in southeastern Gansu Province,we use receiver functions (RFs) to pick the arrival times of ...Based on observations from a dense broadband seismic array located along the northeastern (NE) margin of the Tibetan Plateau in southeastern Gansu Province,we use receiver functions (RFs) to pick the arrival times of P-to-S converted waves and bin the traces in different grids according to the piercing points of the 410 and 660 km discontinuities in the upper mantle.The depths of the two discontinuities are estimated by the ray tracing method with the IASP91 velocity model and a 3-D tomography model.The results indicate the following:(1) The arrival times of the P410s and P660s converted phases are delayed by approximately 1 s than those predicted by the IASP91 model.The mantle transition zone (MTZ) is thicker than that in the global model.(2) The synchronous lags in the P410s and P660s arrival times are consistent with low-velocity anomalies in the upper mantle,which are believed to result mainly from the eastward migration of materials beneath the NE margin of the Tibetan Plateau.(3) Combined with previous tomography results,the depression of the'660'discontinuity and the thickened MTZ are somewhat consistent with the big mantle wedge (BMW) model.However,due to data limitations,more studies are required to explore the BMW in the future.展开更多
Whether climatic changes in high latitudes of the Northern Hemisphere since the last glaciation have effects on the Tibetan Plateau monsoon, and the variation characteristics of the Plateau monsoon itself are still no...Whether climatic changes in high latitudes of the Northern Hemisphere since the last glaciation have effects on the Tibetan Plateau monsoon, and the variation characteristics of the Plateau monsoon itself are still not solved but of great significance. The 22-m high-resolution Ioess-paleosol sequence in the Hezuo Basin on the northeastern Tibetan Plateau demonstrates that the Plateau winter monsoon experienced a millennial variation similar to high latitude Northern Hemisphere, with cold events clearly correlated with Heinrich events but less for the warm events (Dansgarrd-Oeschger events). It may indicate that the climate system at high latitudes in the Northern Hemisphere had played an important role in both the Plateau monsoon and the high-level westerlies. On 10^4 year scale, there are two distinct anomalous changes, which are not found in the records from high latitude northern hemisphere, revealed by the loess grain size in the Hezuo Basin. One is that there was a considerable grain size increase at -36 kaBP, suggesting an abrupt enhancement of the Plateau winter monsoon at that time; the other is that, during 43--36 kaBP, the grain size decreased distinctly, indicating a notable weakening of the Plateau winter monsoon around that period. Both of the two anomalies suggest that the Tibetan climate may have been controlled by some other factors, besides the high latitude climatic changes in the Northern Hemisphere.展开更多
基金financially supported by the Chinese Academy of Geological Sciences Research Fund(Grant Nos.YYWF201511,DZLXJK201710,DZLXJK201405)the Geological Investigation Project of China Geological Survey(Grant Nos.12120113006100, 121201234000160014-4,121201101000150013)
文摘Objective Xining basin is located in the northeastern Qinghai- Tibetan Plateau, which tectonic location belongs to a junction of the Kunlun and Qilian mountains. The southern, northern and western parts of the basin are restricted by the Laji, Daban and Riyue mountains fault zones, and go eastward into the Longzhong basin in Gansu Province. A succession of Cenozoic lacustrine sedimentary strata has been well developed in the Xining basin, with sediments over 800 m thick.
文摘The Qaidam Basin in the NE Tibetan Plateau has contributed the largest amount of potash in China.However,how the potash was formed has long been a subject of debate.Here we carried out a deep drilling
基金funded by China Comprehensive Geophysical Field Observation in North China of Earthquake Scientific Research(201508009)
文摘After the 2015 M_S8. 1 Nepal earthquake,a strong and moderate seismicity belt has formed in Tibet gradually spreading along the northeast direction. In this paper,we attempt to summarize the features and investigate the primary mechanism of this behavior of seismic activity,using a 2-D finite element numerical model with tectonic dynamic settings and GPS horizontal displacements as the constraints. In addition,compared with the NEtrending seismicity belt triggered by the 1996 Xiatongmoin earthquake,we discuss the future earthquake hazard in and around Tibet. Our results show that: the NE-directed seismicity belt is the response of enhanced loading on the anisotropic Qinghai-Tibetan plateau from the Indian plate and earthquake thrusting. Also,this possibly implies that a forthcoming strong earthquake may fill in the gaps in the NE-directed seismicity belt or enhance the seismic hazard in the eastern( the north-south seismic zone) and western( Tianshan tectonic region) parts near the NE-directed belt.
基金supported by Qinghai Oilfield Company,PetroChina(Grant No.2007-technology-exploration-14)National Key Scientific and Technological Projects(Grant No.2008ZX05003-001)
文摘The Eastern Kunlun Mountains play an important role in the growth and eastward extrusion of the Tibetan Plateau. Tectonic and sedimentary study of the Cenozoic Qaidam Basin, especially the southern part, provides key evidence for understanding their evolution. Here we present evidence including isopach maps, seismic sections and sedimentary analysis of single well to illustrate the sedimentary development of the basin and the structural features of its southern margin. The Qaidam Basin extended across Qiman Tagh-Eastern Kunlun Mountains in the early Cenozoic and withdrew northward at ca. 35.5 Ma, and then buckled as an EW striking elliptical depression since ca. 14.9 Ma, with the main depocenter migrating eastward. Our results support the view that the Kumukol and Hoh Xil basins joined the Qaidam Basin in the early Cenozoic time and we propose the Eastern Kunlun Mountains uplifted in the mid-Miocene.
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.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41574077, 41704057 & 41730212)the National Key R & D Program of China (Grant No. 2017YFC1500100)
文摘Based on observations from a dense broadband seismic array located along the northeastern (NE) margin of the Tibetan Plateau in southeastern Gansu Province,we use receiver functions (RFs) to pick the arrival times of P-to-S converted waves and bin the traces in different grids according to the piercing points of the 410 and 660 km discontinuities in the upper mantle.The depths of the two discontinuities are estimated by the ray tracing method with the IASP91 velocity model and a 3-D tomography model.The results indicate the following:(1) The arrival times of the P410s and P660s converted phases are delayed by approximately 1 s than those predicted by the IASP91 model.The mantle transition zone (MTZ) is thicker than that in the global model.(2) The synchronous lags in the P410s and P660s arrival times are consistent with low-velocity anomalies in the upper mantle,which are believed to result mainly from the eastward migration of materials beneath the NE margin of the Tibetan Plateau.(3) Combined with previous tomography results,the depression of the'660'discontinuity and the thickened MTZ are somewhat consistent with the big mantle wedge (BMW) model.However,due to data limitations,more studies are required to explore the BMW in the future.
文摘Whether climatic changes in high latitudes of the Northern Hemisphere since the last glaciation have effects on the Tibetan Plateau monsoon, and the variation characteristics of the Plateau monsoon itself are still not solved but of great significance. The 22-m high-resolution Ioess-paleosol sequence in the Hezuo Basin on the northeastern Tibetan Plateau demonstrates that the Plateau winter monsoon experienced a millennial variation similar to high latitude Northern Hemisphere, with cold events clearly correlated with Heinrich events but less for the warm events (Dansgarrd-Oeschger events). It may indicate that the climate system at high latitudes in the Northern Hemisphere had played an important role in both the Plateau monsoon and the high-level westerlies. On 10^4 year scale, there are two distinct anomalous changes, which are not found in the records from high latitude northern hemisphere, revealed by the loess grain size in the Hezuo Basin. One is that there was a considerable grain size increase at -36 kaBP, suggesting an abrupt enhancement of the Plateau winter monsoon at that time; the other is that, during 43--36 kaBP, the grain size decreased distinctly, indicating a notable weakening of the Plateau winter monsoon around that period. Both of the two anomalies suggest that the Tibetan climate may have been controlled by some other factors, besides the high latitude climatic changes in the Northern Hemisphere.
