0 INTRODUCTION Orogenic belts are commonly built by multiple-stage processes involving oceanic subduction and continental collisions that result in the generation of magma with distinct geochemical compositions,as exe...0 INTRODUCTION Orogenic belts are commonly built by multiple-stage processes involving oceanic subduction and continental collisions that result in the generation of magma with distinct geochemical compositions,as exemplified by Central Asian Orogenic Belts(e.g.,Wang et al.,2024;Yin et al.,2024;Xiao et al.,2005)and the Tethyan tectonic domains(e.g.,Chen et al.,2024;Li et al.,2024;Tao et al.,2024a;Gehrels et al.,2011;Yin and Harrison,2000).展开更多
Recent climate dynamics denote patterns and variations in climatic conditions and associated cryospheric changes in the Pamir region,affecting downstream ecosystems and communities.The present investigation describes ...Recent climate dynamics denote patterns and variations in climatic conditions and associated cryospheric changes in the Pamir region,affecting downstream ecosystems and communities.The present investigation describes changes in Baralmos glacier and supraglacial lakes,along with related hazards,using meteorological observations,reanalysis products,and high-resolution satellite imagery from 2002 to 2022.Moreover,observations using Unmanned Aerial Vehicles(UAVs)were conducted between 2020 and 2022 to document recent variations.Reanalysis data suggested that there are no obvious trends in annual air temperature and precipitation except for a significant temperature rise in July(the warmest month)of about 1.34°C/decade(p<0.05)and precipitation decrease in December(p<0.05).During the last two decades of investigation,lake areas expanded from 20500 to 62800±21 m2,representing an approximately threefold increase,leading to increased mudflows in the Surkhob river and causing severe damage to property and infrastructures,most prominently during 2020 and 2022.The UAV data reveal an average decrease of-2.7±0.5 m in surface elevation downstream of Baralmos glacier between 2020 and 2022.This study is vital for implementing more intensive measures of the glacial environment and defining suitable mitigation strategies in the Pamir region.展开更多
This study identified soft-sediment deformation structures （SSDS） of seismic origin from lacustrine sediments in the late Quaternary paleo-dammed lake at Tashkorgan, northeastern Pamir. The observed deformation stru...This study identified soft-sediment deformation structures （SSDS） of seismic origin from lacustrine sediments in the late Quaternary paleo-dammed lake at Tashkorgan, northeastern Pamir. The observed deformation structures include sand dykes, liquefied diapir and convolute structures, gravity induced SSDS, and thixotropic pillar and tabular structures. We conducted a preliminary study on the morphology, formation and trigger mechanisms of pillar and tabular structures formed by liquefaction of underlying coarse sand and thixotropy of the upper silty clay. The regional tectonic setting and distribution of lacustrine strata indicate that the most probable trigger for the SSDS in lacustrine sediments was seismic activity, with an approximate earthquake magnitude of M〉6.0; the potential seismogenic fault is the southern part of the Kongur normal fault extensional system. AMS ^4C dating results indicate that the SSDS were formed by seismic events occurring between 26050±100 yrBP and 22710±80 yrBP, implying intense fault activity in this region during the late Pleistocene. This study provides new evidence for understanding tectonic activity and regional geodynamics in western China.展开更多
Glaciers in the eastern Pamir are important for water resources and the social and economic development of the region.In the last 50 years,these glaciers have shrunk and lost ice mass due to climate change.In order to...Glaciers in the eastern Pamir are important for water resources and the social and economic development of the region.In the last 50 years,these glaciers have shrunk and lost ice mass due to climate change.In order to understand recent glacier dynamics in the region,a new inventory was compiled from Landsat TM/ETM+ images acquired in2009,free of clouds and with minimal snow cover on the glacierized mountains.The first glacier inventory of the area was also updated by digitizing glacier outlines from topographical maps that had been modified and verified using aerial photographs.Total glacier area decreased by 10.8%±1.1%,mainly attributed to an increase in air temperature,although precipitation,glacier size and topographic features also combined to affect the general shrinkage of the glaciers.The 19.3–21.4 km^3 estimated glacier mass loss has contributed to an increase in river runoff and water resources.展开更多
A thrust belt formed in the basin along the eastern margin of Pamir.The thrust belt is about 50 km wide,extends about 200 km,and includes three compressive structures from south to north：the blind Qipan structural we...A thrust belt formed in the basin along the eastern margin of Pamir.The thrust belt is about 50 km wide,extends about 200 km,and includes three compressive structures from south to north：the blind Qipan structural wedge and Qimugen structural wedge,and the exposed Yengisar anticline.The thrust belt displays a right-stepping en echelon pattern.The Qipan structural wedge dies out northward to the west of the Qimugen structural wedge,and the Qimugen structural wedge dies out northward to the west of the Yengisar anticline.Detailed analysis of seismic reflection profiles of the western Tarim Basin reveal that fan-shaped growth strata were deposited in the shallow part of the thrust belt,recording the deformation sequence of the thrust belt.The depth of the Cenozoic growth strata decreases from south to north.The growth strata of the Qipan structural wedge is located in the middle-lower section of the Pliocene Artux Formation（N2a）,the growth strata of the Qimugen structural wedge is close to the bottom of the Pleistocene Xiyu Formation（Q1x）,and the growth strata of the Yengisar anticline is located in the middle section of the Xiyu Formation（Q1x）.Combined with magnetostratigraphic studies in the western Tarim basin,it can be preliminarily inferred that the deformation sequence of the thrust belt along the eastern margin of Pamir is progressively younger northward.The geometry and kinematic evolution of the thrust belt in the eastern margin of Pamir can be compared with previous analogue modeling experiments of transpressional deformation,suggesting that the thrust belt was formed in a transpressional tectonic setting.展开更多
The 2008 Nura Mw6.7 earthquake occurred in front of the Trans-Alai Range, central Asia. We present Interferometric Synthetic Aperture Radar （InSAR） measurements of its coseismic ground deformation that are available...The 2008 Nura Mw6.7 earthquake occurred in front of the Trans-Alai Range, central Asia. We present Interferometric Synthetic Aperture Radar （InSAR） measurements of its coseismic ground deformation that are available for a major earthquake in the region. Analysis of the InSAR data shows that the earthquake ruptured a secondary fault of the Main Pamir Thrust for about 20 kin. The fault plane striking N46~E and dipping 48~SE is dominated by thrust slip up to 3 m, most of which is confined to the uppermost 2-5 km of the crust, similar to the nearby 1974 MwT.0 Markansu earthquake. The elastic model of interseismic deformation constrained by GPS measurements suggests that the two earthquakes may have resulted from the failures of two high-angle reverse faults that are about 10 km apart and rooted in a locked dScollement at depths of 5-6 kin. The elastic strain is built up by a freely creeping decollement at about 16 mm/a.展开更多
The Pamir Plateau can be divided into three secondary tectonic units from north to south:the North,the Middle and the South Pamir Blocks.The North Pamir Block belonged to the southern margin of Tarim-Karakum,thermochr...The Pamir Plateau can be divided into three secondary tectonic units from north to south:the North,the Middle and the South Pamir Blocks.The North Pamir Block belonged to the southern margin of Tarim-Karakum,thermochronological study of the Pamir structural intersection indicates that accretion of the Middle Pamir Block to the Eurasian Continental Margin and its subduction and collision with the North Pamir Block occurred in the Middle–Late Jurassic.Due to the Neo-Tethys closure in the Early Cretaceous,the South Pamir Block began to collide with the accretion(the Middle Pamir Block)of the Eurasian Continental Margin.Affected by the collision and continuous convergence between the Indian Plate and the Eurasian Plate since the Cenozoic,Pamir is in a multi-stage differential uplift process.During 56.1–48.5 Ma,North Pamir took the lead in uplifting,that is,the first rapid uplift in the Pamir region began there.The continuous compression and contraction of the Indian and Eurasian plates during 22.0–15.1 Ma forced the Pamir tectonic syntaxis to begin its overall uplift,i.e.Pamir began to enter the second rapid uplift stage in the Early Oligocene,which lasted until the Middle Miocene.During 14.6–8.5Ma,South Pamir was in a rapid uplift stage,while North Pamir was in a relatively stable state,showing asymmetry of tectonic deformation in the Pamir region in space.Since 6.5 Ma,Pamir began to rapidly uplift again.展开更多
The Pamir plateau may have been a westward continuation of Tibet plateau.Meanwhile,the Rushan-Pshart suture is correlative to the Bangong-Nujiang suture of Tibet,and the Central Pamir is the lateral equivalent of the ...The Pamir plateau may have been a westward continuation of Tibet plateau.Meanwhile,the Rushan-Pshart suture is correlative to the Bangong-Nujiang suture of Tibet,and the Central Pamir is the lateral equivalent of the Qiangtang Block.We present the first detailed LA-ICPMS zircon U-Pb chronology,major and trace element,and Lu-Hf isotope geochemistry of Taxkorgan two-mica monzogranite to illuminate the Tethys evolution in central Pamir.LA-ICPMS zircon U-Pb dating shows that two-mica monzogranite is emplaced in the Cretaceous(118 Ma).Its geochemical features are similar to S-type granite,with enrichment in LREEs and negative Ba,Sr,Zr and Ti anomalies.All the samples show negative zirconεHf(t)values ranging from 17.0 to 12.5(mean 14.5),corresponding to crustal Hf model(TDM2)ages of 1906 to 2169 Ma.It is inferred that these granitoids are derived from partial melting of peliticmetasedimentary rocks analogous to the Paleoproterozoic Bulunkuole Group,predominantly with muscovite schists component.Based on the petrological and geochemical data presented above,together with the regional geology,this work provides new insights that Bangong Nujiang Ocean closed in Early Cretaceous(120114 Ma).展开更多
We employed a double-difference algorithm （hypoDD） to relocate earthquakes within the region bounded by 66°E-78°E and 32°N-42°N in the period of 1964-2003 reported by the International Seismologi...We employed a double-difference algorithm （hypoDD） to relocate earthquakes within the region bounded by 66°E-78°E and 32°N-42°N in the period of 1964-2003 reported by the International Seismological Center （ISC）. The improved hypocentral locations delineate a double-layered Wadati-Benioff zone in the eastern Hindu Kush intermediate seismic belt. Based on this feature and other evidences, we propose that the intermediate-depth earthquakes beneath the Pamir-Hindu Kush region may occur in two collided subduction zones with opposite dip directions.展开更多
2-D crustal structure and velocity ratio are obtained by processing S-wave data from two wide-angle reflec-tion/refraction profiles in and around Jiashi in northeastern Pamir, with the result of P-wave data taken into...2-D crustal structure and velocity ratio are obtained by processing S-wave data from two wide-angle reflec-tion/refraction profiles in and around Jiashi in northeastern Pamir, with the result of P-wave data taken into con-sideration. The result shows that: 1) Average crustal velocity ratio is obviously higher in Tarim block than in West Kunlun Mts. and Tianshan fold zone, which reflects its crustal physical property of 'hardness' and stability. The relatively low but normai velocity ratio (Poisson's ratio) of the lower crust indicates that the 'downward thrusting' of Tarim basin is the main feature of crustal movement in this area. 2) The rock layer in the upper crust of Tianshan fold zone is relatively 'soft', which makes it prone to rupture and stress energy release. This is the primary tectonic factor for the concentration of small earthquakes in this area. 3) Jiashi is located right over the apex or the inflection point of the updoming lower crustal interface C and the crust-mantle boundary, which is the deep struc-tural background for the occurrence of strong earthquakes. The alternate variation of vp/vs near the block bounda-ries and the complicated configuration of the interfaces in the upper and middie part of the upper crust form a par-ticular structural environment for the Jiashi strong earthquake swarm. vp/vs is comparatively high and shear modulus is low at the focal region, which may be the main reason for the low stress drop of the Jiashi strong earthquake swarm.展开更多
In the northwest of the Himalayan-Tibetan Orogen, the ~250 km-long Kongur Shan extensional system in the eastern Pamir was formed during the convergence between the Indian and Asian plates. Tectonic activity of the Ko...In the northwest of the Himalayan-Tibetan Orogen, the ~250 km-long Kongur Shan extensional system in the eastern Pamir was formed during the convergence between the Indian and Asian plates. Tectonic activity of the Kongur Shan normal fault and the Tashkurgan normal fault can help to reveal the origin of east-west extension along the Kongur Shan extensional system. The Kongur Shan fault has been extensively studied, while the Tashkurgan fault calls for systemic research. In this study, low-temperature thermochronology including apatite fission track analysis and apatite and zircon(U-Th)/He analyses is applied to constrain the timing of activity of the Tashkurgan fault. Results indicate that the Tashkurgan fault initiated at 10–5 Ma, and most likely at 6–5 Ma. The footwall of the Tashkurgan fault has been exhumed at an average exhumation rate of 0.6–0.9 mm/a since the initiation of the Tashkurgan fault. Combined with previous research on the Kongur Shan fault, we believe that the origin of east-west extension along the Kongur Shan extensional system was driven by gravitational collapse of over-thickened Pamir crust.展开更多
The Alpine zone of Central Pamir is elongated in sublatitudinal direction between the Hercynians of Northern Pamir and the Cimmerians of Southern Pamir south of the Vanch\|Akbaital thrust. Its western continuation is ...The Alpine zone of Central Pamir is elongated in sublatitudinal direction between the Hercynians of Northern Pamir and the Cimmerians of Southern Pamir south of the Vanch\|Akbaital thrust. Its western continuation is overthrusted by the Herat fault and its eastern continuation is cut by the Karakoram strike\|slip fault.. The Central Pamir is a mainly S\|vergent (at the southern part N\|vergent) Alpine nappe stack then folding in antiform. It comprises deposits from Vendian to Neogene which have a thickness of 10km. Paleozoic and Mesozoic tectonic activity was poorly displaied in its limits. Rifting took place in Early and probably Upper Paleozoic. Pre\|Upper Cretaceous unconformity is known only in southern (autochthonous) part of the Zone as a result of closing of Bangong\|Nu Jiang ocean. In northern (allochthonous) part of the zone the sequence of Mesozoic and Paleogene rocks has no unconformities. Alpine endogenous processes were developed very intensively. They implied nappes and imbricate structures, linear folding, different igneous activity, zonal metamorphism. Slices of pyroxenites and gabbroids occured. Calc\|alkaline lavas and tuffs constitutes the major part of Paleocene to Miocene sequence (andesites\|ryolites\|in Paleogene, alkaline basalts in Oligocene—Miocene). Oligocene—Miocene zonal metamorphic belt of the intermediate type of high pressure including series of granitegneiss domes can be traced along the Central Pamir. Cores of domes include migmatites and remobilized bodies of the Early Paleozoic gneissic granites. The decompression took place at a later stage and rocks were overprinted by the andalusite\|sillimanite type metamorphism.. Syenite and leucogranite bodies, pegmatite and aplite veins were emplaced.展开更多
As the western end point of continental collision between the Indian and Eurasian plates, Pamir is an ideal place to research uplifting mechanisms in the Tibetan plateau. In this study, 141 644 Pn arrivals were used t...As the western end point of continental collision between the Indian and Eurasian plates, Pamir is an ideal place to research uplifting mechanisms in the Tibetan plateau. In this study, 141 644 Pn arrivals were used to obtain seismic wave velocities and anisotropy in the uppermost mantle beneath Pamir and its adjacent regions by performing tomographic inversion of Pn travel times. The data were selected from multiple databases, including ISC/EHB, the Annual Bulletin of Chinese Earthquakes, and regional bulletins of Xinjiang. The tomography results reveal significant features with high resolution and correlate well with geological structures. The main results are as follows： （1） The Pn wave velocities are particularly high in the old stable blocks such as Tarim basin, Indian plate and Tajik basin, while the low Pn velocities always lie in tectonically active regions like the western Tibetan plateau, Pamir, Tianshan and Hindu Kush. （2） Strong Pn anisotropy is found beneath the Indian-Eurasian collision zone; its direction is parallel to the collision are and nearly perpendicular to both the direction of maximum compression stress and relative crustal movement. The result is probably caused by the pure shear deformation in the uppermost mantle of the collision zone. （3） A geodynamic continent-continent collision model is proposed to show anisotropy and collision mechanisms between the Indian plate and the Tarim and Tajik basins.展开更多
The collision between India plate and Eurasia continent 55 Ma ago caused the convergence between Southwest Tienshan and Pamirs tectonic systems, and conclusions by other researchers also suggest that the convergence w...The collision between India plate and Eurasia continent 55 Ma ago caused the convergence between Southwest Tienshan and Pamirs tectonic systems, and conclusions by other researchers also suggest that the convergence will continue. Studies on the collision between these systems are helpful to the knowledge of the history and the tendency of the in-land tectonics since Cenozoic and are important in science and the real world as for environment changes, resources and energy reform, and forecast of earthquakes. For this reason, by means of digital modeling, on the basis of crustal shortening rate, crustal motion rate and data of physical properties of rocks, with the help of the FE （finite element） theory-based marc software, the United States, we address on the tendency of the convergence in this area in almost 10 Ma and draw a conclusion that the converged borders move northward and stretch southeast. The Southwest Tienshan will move more slowly and suffer less deformation than the Pamirs-West Kunlun （昆仑） system. The Pamirs-West Kunlun system will rotate counterclockwise while moving northward and extending westward.展开更多
The Pamir Plateau comprises a series of crustal fragments that successively accreted to the Eurasian margin preceded the India-Asia collision,is an ideal place to study the Mesozoic tectonics.The authors investigate t...The Pamir Plateau comprises a series of crustal fragments that successively accreted to the Eurasian margin preceded the India-Asia collision,is an ideal place to study the Mesozoic tectonics.The authors investigate the southern Tashkorgan area,northeastern Pamir Plateau,where Mesozoic metamorphic and igneous rocks are exposed.New structural and biotite ^(40)Ar-^(39)Ar age data are presented.Two stages of intense deformation in the metamorphic rocks are identified,which are unconformably covered by the Early Cretaceous sediment.Two high-grade metamorphic rocks yielding 128.4±0.8 Ma and 144.5±0.9 Ma ^(40)Ar-^(39)Ar ages indicate that the samples experienced an Early Cretaceous cooling event.Combined with previous studies,it is proposed that the Early Cretaceous tectonic records in the southern Tashkorgan region are associated with Andean-style orogenesis.They are the results of the flat/low-angle subduction of the Neotethyan oceanic lithosphere.展开更多
Deformation during the uplift of Pamir Since the Himalayan movement, the Punjab block of Indian plate has intruded into the interior of Eurasian plate, produced a protrusive Pamir knot in eastern Tethys. The Pamir kno...Deformation during the uplift of Pamir Since the Himalayan movement, the Punjab block of Indian plate has intruded into the interior of Eurasian plate, produced a protrusive Pamir knot in eastern Tethys. The Pamir knot is where crustal shortening is most intensive in Tethys. After India\|Eurasia collision, giant relief resulted from fast uplifting of Karakorum due to the convergence and underplating in northern and southern margins of Karakorum, the uplifting rates changed with times, and thrusting would be one of the most important factors controlling the uplifting. At the same time, large scale strike\|slip faulting could produced large vertical offsets, so that the exhumation of the rocks from middle and lower crust has drawn much attention. The post\|collisional deformation and evolution of Karakorum would involve the processes of continental escape, crustal shortening and thickening, and orogenic collapse in extensional regime. The thrusting started in late Jurassic and early Cretaceous, but two peaks occurred in late Cretaceous and Eocene, respectively. A large amount of klippen produced by thrusting from north to south have been discovered in the northern slope of the Kungai in front of Pamir. Molnar and Tapponnier noted that the mount of crustal shortening in Pamir would be up to 2000km in the past 40～45Ma, and Coward proposed that 300～400km shortening has happened only in southern Pamir to northern Pakistan. In western Pamir from Kabul of Afghanistan to Quatta of Pakistan, the Chaman left\|lateral strike\|slip fault system extends 1000km long. Multiple structural superposition in eastern Pamir, due to the effects of the uplifting of Qinghai\|Tibet plateau, resulted in complex deformation patterns.展开更多
The geological, geographic and seismicity data indicate that three arc tectonic belt developed on the northeast Pamir, which was the south Pamir arc, the north Pamir arc and the external Pamir arc from south to north....The geological, geographic and seismicity data indicate that three arc tectonic belt developed on the northeast Pamir, which was the south Pamir arc, the north Pamir arc and the external Pamir arc from south to north. In addition to these three belts, there are two nascent arc tectonic belts developed in its fore\|deep depression, the Kashi depression in the northwest Tarim basin, which is the northward propagation of the arc tectonics of northeast Pamir.The south Pamir is an ancient folded belt, composed of the Proterozoic metamorphic layers and igneous complex. It was pushed northward since the collision between the India and Asia, and uplifted since the end of the early Tertiary. The elevation of the Plateau is 4800～5300m, and several intermontane basins distributed in the plateau. At its northeast boundary is the Kalakorum right lateral strike slip fault. Strong strike slip earthquakes occurred along this fault. In the hinterland of the plateau, several normal faulting earthquakes occurred,which are consistent with the extensional dynamic environment of the south Pamir. Deep earthquakes occurred under the 70km depth crust of south Pamir. The N—S cross section of the focal depth show that the earthquake occurred within the south Pamir crust are lower than 70km, and the deep earthquakes with depth of 100～200km occurred in the crystal basement of Tarim basin which are under\|thrusting southward into the root of the south Pamir.展开更多
We want to talk about the geohazards in Pamir mountains,in Tajikistan,using different materials and researches about it.Also we are trying to look deeply into this problem,and want to research how about
The Pamirs—Himalaya region possessing a complex tectonic structure and high seismic activity is located at the central part of the Alpine—Himalayan fold belt. During long\|term geodynamical studies we revealed new f...The Pamirs—Himalaya region possessing a complex tectonic structure and high seismic activity is located at the central part of the Alpine—Himalayan fold belt. During long\|term geodynamical studies we revealed new features of its modern structural plan steadily traced at different deep levels. The reconstruction of paleostresses by analyzing fracture patterns of Mesozoic—Cenozoic sedimentary rocks has been carried out in order to establish geodynamic regularities of the region under study and to propose a model of its development. Unlike traditional approaches to the problem of paleostress reconstruction from orientation of systems of rock joints, approaches which are based usually on the local strength criteria, we consider the formation of joint sets as a rheological instability manifesting in localized form. The systems of layers of localized plastic deformation are formed during lithification of sedimentary rocks and evolve with time into joint sets. The corresponding method of reconstruction of paleostress axes was developed. It was tested for some tectonically active regions: Central Asia, the Caucasus, the Crimea, Cuba, Iran, and others. The method was found to be useful for reconstruction of both history and spatial distribution of paleostress axes in active crustal blocks and near large geological structures. In the Pamirs—Himalaya region the fracturing of rocks has been investigated in about 1000 outcrops. By analyzing the Mesozoic—Cenozoic paleostress history it was confirmed that the structural features of the region (including an arc\|like shape of the Pamirs—Tian Shan junction zone) are caused by movement of the Hindustan mobile plate towards the rather stable Eurasian plate during the Alpine cycle of development.展开更多
Basement structures and basement interfaces are obtained by finite-difference and time-term methods using Pg-wave data from two deep seismic sounding (DSS) profiles in the Artush-Jiashi strong earthquake area. The geo...Basement structures and basement interfaces are obtained by finite-difference and time-term methods using Pg-wave data from two deep seismic sounding (DSS) profiles in the Artush-Jiashi strong earthquake area. The geological units differ considerably in basement depth. The basement structures of contact zones between two geological units also vary obviously, which marks the existence of boundary faults. Finally, we make a remark upon the relationship between characteristics of basement structures and seismicity in the Artush meizoseismal area and the Jiashi earthquake swarm area.展开更多
基金supported by the National Key Research and Development Project(No.2022YFC2903302)the Second Tibet Plateau Scientific Expedition and Research Program(STEP),(No.2019QZKK0802)+2 种基金the National Natural Science Foundation of China(No.42361144841)the Chinese Academy of Geological Sciences Basal Research Fund(No.JKYZD202402)the Scientific Research Fund Project of BGRIMM Technology Group(No.JTKY202427822)。
文摘0 INTRODUCTION Orogenic belts are commonly built by multiple-stage processes involving oceanic subduction and continental collisions that result in the generation of magma with distinct geochemical compositions,as exemplified by Central Asian Orogenic Belts(e.g.,Wang et al.,2024;Yin et al.,2024;Xiao et al.,2005)and the Tethyan tectonic domains(e.g.,Chen et al.,2024;Li et al.,2024;Tao et al.,2024a;Gehrels et al.,2011;Yin and Harrison,2000).
基金funded by the Gansu Provincial Science and Technology Program(22ZD6FA005)Gansu Postdoctoral Science Foundation(Grant number-E339880204)。
文摘Recent climate dynamics denote patterns and variations in climatic conditions and associated cryospheric changes in the Pamir region,affecting downstream ecosystems and communities.The present investigation describes changes in Baralmos glacier and supraglacial lakes,along with related hazards,using meteorological observations,reanalysis products,and high-resolution satellite imagery from 2002 to 2022.Moreover,observations using Unmanned Aerial Vehicles(UAVs)were conducted between 2020 and 2022 to document recent variations.Reanalysis data suggested that there are no obvious trends in annual air temperature and precipitation except for a significant temperature rise in July(the warmest month)of about 1.34°C/decade(p<0.05)and precipitation decrease in December(p<0.05).During the last two decades of investigation,lake areas expanded from 20500 to 62800±21 m2,representing an approximately threefold increase,leading to increased mudflows in the Surkhob river and causing severe damage to property and infrastructures,most prominently during 2020 and 2022.The UAV data reveal an average decrease of-2.7±0.5 m in surface elevation downstream of Baralmos glacier between 2020 and 2022.This study is vital for implementing more intensive measures of the glacial environment and defining suitable mitigation strategies in the Pamir region.
基金financially supported by the National Natural Science Foundation of China (41702372)the Open Fund of State Key Laboratory of Earthquake Dynamics (LED2017B03)
文摘This study identified soft-sediment deformation structures （SSDS） of seismic origin from lacustrine sediments in the late Quaternary paleo-dammed lake at Tashkorgan, northeastern Pamir. The observed deformation structures include sand dykes, liquefied diapir and convolute structures, gravity induced SSDS, and thixotropic pillar and tabular structures. We conducted a preliminary study on the morphology, formation and trigger mechanisms of pillar and tabular structures formed by liquefaction of underlying coarse sand and thixotropy of the upper silty clay. The regional tectonic setting and distribution of lacustrine strata indicate that the most probable trigger for the SSDS in lacustrine sediments was seismic activity, with an approximate earthquake magnitude of M〉6.0; the potential seismogenic fault is the southern part of the Kongur normal fault extensional system. AMS ^4C dating results indicate that the SSDS were formed by seismic events occurring between 26050±100 yrBP and 22710±80 yrBP, implying intense fault activity in this region during the late Pleistocene. This study provides new evidence for understanding tectonic activity and regional geodynamics in western China.
基金supported by the Chinese Academy of Sciences (Grant No.KZZD-EW-12-1)the National Natural Science Foundation (Grant No.41190084)+3 种基金the Ministry of Science and Technology of China (MOST) (Grant Nos.2013FY111400,2010DFA92720-23)an immediate past project from the MOST (Grant No.2006FY110200)provided by "Investigation on glacier resources and their change in China" (Grant No.2006FY110200)"Glacier change monitoring and its impact assessment research in west China" (Grant No.kzcx2-yw-301)
文摘Glaciers in the eastern Pamir are important for water resources and the social and economic development of the region.In the last 50 years,these glaciers have shrunk and lost ice mass due to climate change.In order to understand recent glacier dynamics in the region,a new inventory was compiled from Landsat TM/ETM+ images acquired in2009,free of clouds and with minimal snow cover on the glacierized mountains.The first glacier inventory of the area was also updated by digitizing glacier outlines from topographical maps that had been modified and verified using aerial photographs.Total glacier area decreased by 10.8%±1.1%,mainly attributed to an increase in air temperature,although precipitation,glacier size and topographic features also combined to affect the general shrinkage of the glaciers.The 19.3–21.4 km^3 estimated glacier mass loss has contributed to an increase in river runoff and water resources.
基金funded by the National Natural Science Foundation of China(No.41272230)
文摘A thrust belt formed in the basin along the eastern margin of Pamir.The thrust belt is about 50 km wide,extends about 200 km,and includes three compressive structures from south to north：the blind Qipan structural wedge and Qimugen structural wedge,and the exposed Yengisar anticline.The thrust belt displays a right-stepping en echelon pattern.The Qipan structural wedge dies out northward to the west of the Qimugen structural wedge,and the Qimugen structural wedge dies out northward to the west of the Yengisar anticline.Detailed analysis of seismic reflection profiles of the western Tarim Basin reveal that fan-shaped growth strata were deposited in the shallow part of the thrust belt,recording the deformation sequence of the thrust belt.The depth of the Cenozoic growth strata decreases from south to north.The growth strata of the Qipan structural wedge is located in the middle-lower section of the Pliocene Artux Formation（N2a）,the growth strata of the Qimugen structural wedge is close to the bottom of the Pleistocene Xiyu Formation（Q1x）,and the growth strata of the Yengisar anticline is located in the middle section of the Xiyu Formation（Q1x）.Combined with magnetostratigraphic studies in the western Tarim basin,it can be preliminarily inferred that the deformation sequence of the thrust belt along the eastern margin of Pamir is progressively younger northward.The geometry and kinematic evolution of the thrust belt in the eastern margin of Pamir can be compared with previous analogue modeling experiments of transpressional deformation,suggesting that the thrust belt was formed in a transpressional tectonic setting.
基金The study is funded by the National Natural Science Foundation of China(41274027,41274037,41374030 and 41474097)
文摘The 2008 Nura Mw6.7 earthquake occurred in front of the Trans-Alai Range, central Asia. We present Interferometric Synthetic Aperture Radar （InSAR） measurements of its coseismic ground deformation that are available for a major earthquake in the region. Analysis of the InSAR data shows that the earthquake ruptured a secondary fault of the Main Pamir Thrust for about 20 kin. The fault plane striking N46~E and dipping 48~SE is dominated by thrust slip up to 3 m, most of which is confined to the uppermost 2-5 km of the crust, similar to the nearby 1974 MwT.0 Markansu earthquake. The elastic model of interseismic deformation constrained by GPS measurements suggests that the two earthquakes may have resulted from the failures of two high-angle reverse faults that are about 10 km apart and rooted in a locked dScollement at depths of 5-6 kin. The elastic strain is built up by a freely creeping decollement at about 16 mm/a.
基金This work was supported by the Projects of the China Geological Survey(grant nos 12120114018601,121201011000150010).
文摘The Pamir Plateau can be divided into three secondary tectonic units from north to south:the North,the Middle and the South Pamir Blocks.The North Pamir Block belonged to the southern margin of Tarim-Karakum,thermochronological study of the Pamir structural intersection indicates that accretion of the Middle Pamir Block to the Eurasian Continental Margin and its subduction and collision with the North Pamir Block occurred in the Middle–Late Jurassic.Due to the Neo-Tethys closure in the Early Cretaceous,the South Pamir Block began to collide with the accretion(the Middle Pamir Block)of the Eurasian Continental Margin.Affected by the collision and continuous convergence between the Indian Plate and the Eurasian Plate since the Cenozoic,Pamir is in a multi-stage differential uplift process.During 56.1–48.5 Ma,North Pamir took the lead in uplifting,that is,the first rapid uplift in the Pamir region began there.The continuous compression and contraction of the Indian and Eurasian plates during 22.0–15.1 Ma forced the Pamir tectonic syntaxis to begin its overall uplift,i.e.Pamir began to enter the second rapid uplift stage in the Early Oligocene,which lasted until the Middle Miocene.During 14.6–8.5Ma,South Pamir was in a rapid uplift stage,while North Pamir was in a relatively stable state,showing asymmetry of tectonic deformation in the Pamir region in space.Since 6.5 Ma,Pamir began to rapidly uplift again.
基金Project(41802103)supported by the National Natural Science Foundation of ChinaProject(2017YFC0601403)supported by the National Key R&D Program of China
文摘The Pamir plateau may have been a westward continuation of Tibet plateau.Meanwhile,the Rushan-Pshart suture is correlative to the Bangong-Nujiang suture of Tibet,and the Central Pamir is the lateral equivalent of the Qiangtang Block.We present the first detailed LA-ICPMS zircon U-Pb chronology,major and trace element,and Lu-Hf isotope geochemistry of Taxkorgan two-mica monzogranite to illuminate the Tethys evolution in central Pamir.LA-ICPMS zircon U-Pb dating shows that two-mica monzogranite is emplaced in the Cretaceous(118 Ma).Its geochemical features are similar to S-type granite,with enrichment in LREEs and negative Ba,Sr,Zr and Ti anomalies.All the samples show negative zirconεHf(t)values ranging from 17.0 to 12.5(mean 14.5),corresponding to crustal Hf model(TDM2)ages of 1906 to 2169 Ma.It is inferred that these granitoids are derived from partial melting of peliticmetasedimentary rocks analogous to the Paleoproterozoic Bulunkuole Group,predominantly with muscovite schists component.Based on the petrological and geochemical data presented above,together with the regional geology,this work provides new insights that Bangong Nujiang Ocean closed in Early Cretaceous(120114 Ma).
基金partly sup-ported by the National Fundamental Science Program of China under(No.2004cb418406)the National Natural Science Foundation of China(No.90814002)Key Projects in the National Science & Technology PillarProgram during the Eleventh Five-year Plan Period(No.2008BAC38B02-4)
文摘We employed a double-difference algorithm （hypoDD） to relocate earthquakes within the region bounded by 66°E-78°E and 32°N-42°N in the period of 1964-2003 reported by the International Seismological Center （ISC）. The improved hypocentral locations delineate a double-layered Wadati-Benioff zone in the eastern Hindu Kush intermediate seismic belt. Based on this feature and other evidences, we propose that the intermediate-depth earthquakes beneath the Pamir-Hindu Kush region may occur in two collided subduction zones with opposite dip directions.
基金State Key Basic Development and Programming Project (G1998040702)the Project (9691307) from Ministry of Science and Technology and China Seismological Bureau.
文摘2-D crustal structure and velocity ratio are obtained by processing S-wave data from two wide-angle reflec-tion/refraction profiles in and around Jiashi in northeastern Pamir, with the result of P-wave data taken into con-sideration. The result shows that: 1) Average crustal velocity ratio is obviously higher in Tarim block than in West Kunlun Mts. and Tianshan fold zone, which reflects its crustal physical property of 'hardness' and stability. The relatively low but normai velocity ratio (Poisson's ratio) of the lower crust indicates that the 'downward thrusting' of Tarim basin is the main feature of crustal movement in this area. 2) The rock layer in the upper crust of Tianshan fold zone is relatively 'soft', which makes it prone to rupture and stress energy release. This is the primary tectonic factor for the concentration of small earthquakes in this area. 3) Jiashi is located right over the apex or the inflection point of the updoming lower crustal interface C and the crust-mantle boundary, which is the deep struc-tural background for the occurrence of strong earthquakes. The alternate variation of vp/vs near the block bounda-ries and the complicated configuration of the interfaces in the upper and middie part of the upper crust form a par-ticular structural environment for the Jiashi strong earthquake swarm. vp/vs is comparatively high and shear modulus is low at the focal region, which may be the main reason for the low stress drop of the Jiashi strong earthquake swarm.
基金funded by the National Natural Science Foundation of China (Nos. 41720104003 and 41330207)the National Science and Technology Major Project of China (Nos. 2017ZX05008-001 and 2016ZX05003-001)Chen S Q receives a PhD grant (No. 201706320352) from the China Scholarship Council。
文摘In the northwest of the Himalayan-Tibetan Orogen, the ~250 km-long Kongur Shan extensional system in the eastern Pamir was formed during the convergence between the Indian and Asian plates. Tectonic activity of the Kongur Shan normal fault and the Tashkurgan normal fault can help to reveal the origin of east-west extension along the Kongur Shan extensional system. The Kongur Shan fault has been extensively studied, while the Tashkurgan fault calls for systemic research. In this study, low-temperature thermochronology including apatite fission track analysis and apatite and zircon(U-Th)/He analyses is applied to constrain the timing of activity of the Tashkurgan fault. Results indicate that the Tashkurgan fault initiated at 10–5 Ma, and most likely at 6–5 Ma. The footwall of the Tashkurgan fault has been exhumed at an average exhumation rate of 0.6–0.9 mm/a since the initiation of the Tashkurgan fault. Combined with previous research on the Kongur Shan fault, we believe that the origin of east-west extension along the Kongur Shan extensional system was driven by gravitational collapse of over-thickened Pamir crust.
文摘The Alpine zone of Central Pamir is elongated in sublatitudinal direction between the Hercynians of Northern Pamir and the Cimmerians of Southern Pamir south of the Vanch\|Akbaital thrust. Its western continuation is overthrusted by the Herat fault and its eastern continuation is cut by the Karakoram strike\|slip fault.. The Central Pamir is a mainly S\|vergent (at the southern part N\|vergent) Alpine nappe stack then folding in antiform. It comprises deposits from Vendian to Neogene which have a thickness of 10km. Paleozoic and Mesozoic tectonic activity was poorly displaied in its limits. Rifting took place in Early and probably Upper Paleozoic. Pre\|Upper Cretaceous unconformity is known only in southern (autochthonous) part of the Zone as a result of closing of Bangong\|Nu Jiang ocean. In northern (allochthonous) part of the zone the sequence of Mesozoic and Paleogene rocks has no unconformities. Alpine endogenous processes were developed very intensively. They implied nappes and imbricate structures, linear folding, different igneous activity, zonal metamorphism. Slices of pyroxenites and gabbroids occured. Calc\|alkaline lavas and tuffs constitutes the major part of Paleocene to Miocene sequence (andesites\|ryolites\|in Paleogene, alkaline basalts in Oligocene—Miocene). Oligocene—Miocene zonal metamorphic belt of the intermediate type of high pressure including series of granitegneiss domes can be traced along the Central Pamir. Cores of domes include migmatites and remobilized bodies of the Early Paleozoic gneissic granites. The decompression took place at a later stage and rocks were overprinted by the andalusite\|sillimanite type metamorphism.. Syenite and leucogranite bodies, pegmatite and aplite veins were emplaced.
基金financially supported jointly by the National Natural Science Foundation of China (Grant Nos. 41174036 and 41021001)the foundation from Chinese Academy of Sciences (Grant No. KZCX2-EW-QN102)
文摘As the western end point of continental collision between the Indian and Eurasian plates, Pamir is an ideal place to research uplifting mechanisms in the Tibetan plateau. In this study, 141 644 Pn arrivals were used to obtain seismic wave velocities and anisotropy in the uppermost mantle beneath Pamir and its adjacent regions by performing tomographic inversion of Pn travel times. The data were selected from multiple databases, including ISC/EHB, the Annual Bulletin of Chinese Earthquakes, and regional bulletins of Xinjiang. The tomography results reveal significant features with high resolution and correlate well with geological structures. The main results are as follows： （1） The Pn wave velocities are particularly high in the old stable blocks such as Tarim basin, Indian plate and Tajik basin, while the low Pn velocities always lie in tectonically active regions like the western Tibetan plateau, Pamir, Tianshan and Hindu Kush. （2） Strong Pn anisotropy is found beneath the Indian-Eurasian collision zone; its direction is parallel to the collision are and nearly perpendicular to both the direction of maximum compression stress and relative crustal movement. The result is probably caused by the pure shear deformation in the uppermost mantle of the collision zone. （3） A geodynamic continent-continent collision model is proposed to show anisotropy and collision mechanisms between the Indian plate and the Tarim and Tajik basins.
基金supported by the Basic Outlay of Scientific Re-search Work from the Ministry of Science and Technology of China (No. J0802)the National Natural Science Foundation of China (No. 40572122)Basic Geologic Project of China Geological Survey (Nos. 12010611811, 10210610105)
文摘The collision between India plate and Eurasia continent 55 Ma ago caused the convergence between Southwest Tienshan and Pamirs tectonic systems, and conclusions by other researchers also suggest that the convergence will continue. Studies on the collision between these systems are helpful to the knowledge of the history and the tendency of the in-land tectonics since Cenozoic and are important in science and the real world as for environment changes, resources and energy reform, and forecast of earthquakes. For this reason, by means of digital modeling, on the basis of crustal shortening rate, crustal motion rate and data of physical properties of rocks, with the help of the FE （finite element） theory-based marc software, the United States, we address on the tendency of the convergence in this area in almost 10 Ma and draw a conclusion that the converged borders move northward and stretch southeast. The Southwest Tienshan will move more slowly and suffer less deformation than the Pamirs-West Kunlun （昆仑） system. The Pamirs-West Kunlun system will rotate counterclockwise while moving northward and extending westward.
基金supported by the National Natural Science Foundation of China(91955203,91755101,41872121,41302166)the fund from the Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources(J1901-20-4)+2 种基金Scientific Research Fund of the Institute of Geology,Chinese Academy of Geological Sciences(S2003)the Basic Research Project of Chinese Academy of Geological Sciences(JYYWF20180903,JYYWF20182103)the project of China Geological Survey(DD20190006,DD20190060).
文摘The Pamir Plateau comprises a series of crustal fragments that successively accreted to the Eurasian margin preceded the India-Asia collision,is an ideal place to study the Mesozoic tectonics.The authors investigate the southern Tashkorgan area,northeastern Pamir Plateau,where Mesozoic metamorphic and igneous rocks are exposed.New structural and biotite ^(40)Ar-^(39)Ar age data are presented.Two stages of intense deformation in the metamorphic rocks are identified,which are unconformably covered by the Early Cretaceous sediment.Two high-grade metamorphic rocks yielding 128.4±0.8 Ma and 144.5±0.9 Ma ^(40)Ar-^(39)Ar ages indicate that the samples experienced an Early Cretaceous cooling event.Combined with previous studies,it is proposed that the Early Cretaceous tectonic records in the southern Tashkorgan region are associated with Andean-style orogenesis.They are the results of the flat/low-angle subduction of the Neotethyan oceanic lithosphere.
文摘Deformation during the uplift of Pamir Since the Himalayan movement, the Punjab block of Indian plate has intruded into the interior of Eurasian plate, produced a protrusive Pamir knot in eastern Tethys. The Pamir knot is where crustal shortening is most intensive in Tethys. After India\|Eurasia collision, giant relief resulted from fast uplifting of Karakorum due to the convergence and underplating in northern and southern margins of Karakorum, the uplifting rates changed with times, and thrusting would be one of the most important factors controlling the uplifting. At the same time, large scale strike\|slip faulting could produced large vertical offsets, so that the exhumation of the rocks from middle and lower crust has drawn much attention. The post\|collisional deformation and evolution of Karakorum would involve the processes of continental escape, crustal shortening and thickening, and orogenic collapse in extensional regime. The thrusting started in late Jurassic and early Cretaceous, but two peaks occurred in late Cretaceous and Eocene, respectively. A large amount of klippen produced by thrusting from north to south have been discovered in the northern slope of the Kungai in front of Pamir. Molnar and Tapponnier noted that the mount of crustal shortening in Pamir would be up to 2000km in the past 40～45Ma, and Coward proposed that 300～400km shortening has happened only in southern Pamir to northern Pakistan. In western Pamir from Kabul of Afghanistan to Quatta of Pakistan, the Chaman left\|lateral strike\|slip fault system extends 1000km long. Multiple structural superposition in eastern Pamir, due to the effects of the uplifting of Qinghai\|Tibet plateau, resulted in complex deformation patterns.
文摘The geological, geographic and seismicity data indicate that three arc tectonic belt developed on the northeast Pamir, which was the south Pamir arc, the north Pamir arc and the external Pamir arc from south to north. In addition to these three belts, there are two nascent arc tectonic belts developed in its fore\|deep depression, the Kashi depression in the northwest Tarim basin, which is the northward propagation of the arc tectonics of northeast Pamir.The south Pamir is an ancient folded belt, composed of the Proterozoic metamorphic layers and igneous complex. It was pushed northward since the collision between the India and Asia, and uplifted since the end of the early Tertiary. The elevation of the Plateau is 4800～5300m, and several intermontane basins distributed in the plateau. At its northeast boundary is the Kalakorum right lateral strike slip fault. Strong strike slip earthquakes occurred along this fault. In the hinterland of the plateau, several normal faulting earthquakes occurred,which are consistent with the extensional dynamic environment of the south Pamir. Deep earthquakes occurred under the 70km depth crust of south Pamir. The N—S cross section of the focal depth show that the earthquake occurred within the south Pamir crust are lower than 70km, and the deep earthquakes with depth of 100～200km occurred in the crystal basement of Tarim basin which are under\|thrusting southward into the root of the south Pamir.
文摘We want to talk about the geohazards in Pamir mountains,in Tajikistan,using different materials and researches about it.Also we are trying to look deeply into this problem,and want to research how about
文摘The Pamirs—Himalaya region possessing a complex tectonic structure and high seismic activity is located at the central part of the Alpine—Himalayan fold belt. During long\|term geodynamical studies we revealed new features of its modern structural plan steadily traced at different deep levels. The reconstruction of paleostresses by analyzing fracture patterns of Mesozoic—Cenozoic sedimentary rocks has been carried out in order to establish geodynamic regularities of the region under study and to propose a model of its development. Unlike traditional approaches to the problem of paleostress reconstruction from orientation of systems of rock joints, approaches which are based usually on the local strength criteria, we consider the formation of joint sets as a rheological instability manifesting in localized form. The systems of layers of localized plastic deformation are formed during lithification of sedimentary rocks and evolve with time into joint sets. The corresponding method of reconstruction of paleostress axes was developed. It was tested for some tectonically active regions: Central Asia, the Caucasus, the Crimea, Cuba, Iran, and others. The method was found to be useful for reconstruction of both history and spatial distribution of paleostress axes in active crustal blocks and near large geological structures. In the Pamirs—Himalaya region the fracturing of rocks has been investigated in about 1000 outcrops. By analyzing the Mesozoic—Cenozoic paleostress history it was confirmed that the structural features of the region (including an arc\|like shape of the Pamirs—Tian Shan junction zone) are caused by movement of the Hindustan mobile plate towards the rather stable Eurasian plate during the Alpine cycle of development.
基金State Key Basic Research Development and Programming Project Mechanism and Prediction of Strong Continental Earthquake (G1998040702) and Joint Seismological Science Foundation of China (198062). Contribution No. GPB200109 Research Center of Exploration
文摘Basement structures and basement interfaces are obtained by finite-difference and time-term methods using Pg-wave data from two deep seismic sounding (DSS) profiles in the Artush-Jiashi strong earthquake area. The geological units differ considerably in basement depth. The basement structures of contact zones between two geological units also vary obviously, which marks the existence of boundary faults. Finally, we make a remark upon the relationship between characteristics of basement structures and seismicity in the Artush meizoseismal area and the Jiashi earthquake swarm area.
