GEODYNAMICS OF THE PAMIRS—HIMALAYA REGION

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.

Study on basement structures of the northeast Pamirs

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.

Temporal and Spatial Variation Characteristics of Snow Cover Area in the Pamirs from 2010 to 2020

Scientific and comprehensive monitoring of snow cover changes in the Pamirs is of great significance to the prevention of snow disasters around the Pamirs and the full utilization of water resources. Utilize the 2010-2020 snow cover product MOD10A2, Synthesis by maximum, The temporal and spatial variation characteristics of snow cover area in the Pamirs in the past 11 years have been obtained. Research indicates: In terms of interannual changes, the snow cover area of the Pamir Plateau from 2010 to 2020 generally showed a slight decrease trend. The average snow cover area in 2012 was the largest, reaching 54.167% of the total area. In 2014, the average snow cover area was the smallest, accounting for only 44.863% of the total area. In terms of annual changes, there are obvious changes with the change of seasons. The largest snow area is in March, and the smallest snow area is in August. In the past 11 years, the average snow cover area in spring and summer showed a slow decreasing trend, and there was almost no change in autumn and winter. In terms of space, the snow cover area of the Pamirs is significantly affected by altitude, and the high snow cover areas are mainly distributed in the Karakoram Mountains and other areas with an altitude greater than 5000 meters.

Xiadiya:Daughter of the Pamirs

ON the Pamir Plateau, 3,200 meters above sea level, live the Tajik people. Almost every Tajik knows the name Xiadiya. She is regarded as the pride of Tajik women, for she is the first female Tajik college student, the first female leader of Taxkorgan Tajik Autonomous County Party Committee and the first female Tajik deputy to come to Beijing to attend

Quantifying glacier surging and associated lake dynamics in Amu Darya river basin using UAV and remote sensing data

Glaciers in the Pamir region are experiencing rapid melting and receding due to climate change,which has a significant implication for the Amu Darya river basin.Predominantly,surging glaciers,which undergo unpredictable advances,are potentially leading to the obstruction of high-altitude river channels and also glacial lake outburst floods.decrease of-703.5±30.0 m.There is a substantial increase in the number(from 19 to 75)and area(from 4889.7±0.6 m2 to 15345.5±0.6 m2)of RGS lakes along with supra-glacier ponds based on a comparison of ArcGIS base map in 2011 and high-resolution UAV data in 2023.For M glacier,number of lakes increased from 4 to 22 but the lake area declined from 10715.2±0.6 to 365.6±0.6 m2.It was noted that the largest lake in 2011 with an area of 10406.4±0.6 m2 at the southeastern portion of the glacier was not observed in 2023 due to outburst.Both the glaciers have substantially impacted the river flow(Abdukahor river)by obstructing a significant proportion of river channel in recent years and might cause outburst floods.These findings enhance the understanding of glacier dynamics and their impacts on the surrounding areas,emphasizing the urgent need for continued monitoring and appropriate management strategies,with a specific focus on surging glaciers and the associated risks.

先进双基SAR技术研究(英文)

该文展示了世界上几个重要的先进混合双基SAR实验。混合双基模式是指发射端和接收端分别装载于不同类型的平台,例如星载/机载,机载/静止平台,星载/静止平台等。近年来相继有若干混合双基SAR实验成功完成,主要包括TerraSAR-X/PAMIR,PAMIR/静止平台,以及TerraSAR-X/静止平台。此外,在TerraSAR-X/静止平台的双基模式下还验证了多基线干涉SAR(MB-InSAR)和数字波束形成(DBF)技术。值得强调的是,该文所展示的DBF实验结果属于世界上首次成功的基于在轨雷达卫星的DBF实验。

A study on physical property of crustal material and seismogenic environment in northeastern Pamir

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.

Geohazards in Pamir Mountains,Tajikistan

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

A Preliminary Study on the Soft–Sediment Deformation Structures in the Late Quaternary Lacustrine Sediments at Tashkorgan, Northeastern Pamir, China

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.

Glacier changes since the early 1960s, eastern Pamir, China

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.

Mesozoic–Cenozoic Tectonic Evolution and Uplift in Pamir:Application of Fission Track Thermochronology

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.

Late Cenozoic Deformation Sequence of a Thrust System along the Eastern Margin of Pamir,Northwest China

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.

Origin of Early Creceouscalc-alkaline granite, Taxkorgan: Implications for evolution of Tethys evolution in central Pamir

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).

Tree ring based drought variability in Northwest Tajikistan since 1895 AD

Determining the mechanisms controlling the changes of wet and dry conditions will improve our understanding of climate change over the past hundred years,which is of great significance to the study of climate and environmental changes in the arid regions of Central Asia.Forest trees are ecologically significant in the local environment,and therefore the tree ring analysis can provide a clear record of regional historical climate.This study analyzed the correlation between the tree ring width chronology of Juniperus turkestanica Komarov and the standardized precipitation evapotranspiration index(SPEI)in Northwest Tajikistan,based on 56 tree ring samples collected from Shahristan in the Pamir region.Climate data including precipitation,temperature and the SPEI were downloaded from the Climate Research Unit(CRU)TS 4.00.The COFECHA program was used for cross-dating,and the ARSTAN program was used to remove the growth trend of the tree itself and the influence of non-climatic factors on the growth of the trees.A significant correlation was found between the radial growth of J.turkestanica trees and the monthly mean SPEI of February–April.The monthly mean SPEI sequence of February–April during the period of 1895–2016 was reconstructed,and the reconstruction equation explained 42.5%of the variance.During the past 122 a(1895–2016),the study area has experienced three wetter periods(precipitation above average):1901–1919,1945–1983 and 1995–2010,and four drier periods(precipitation below average):1895–1900,1920–1944,1984–1994 and 2011–2016.The spatial correlation analysis revealed that the monthly mean SPEI reconstruction sequence of February–April could be used to characterize the large-scale dry-wet variations in Northwest Tajikistan during the period of 1895–2016.This study could provide comparative data for validating the projections of climate models and scientific basis for managing water resources in Tajikistan in the context of climate change.

The 2008 Nura Mw6.7 earthquake: A shallow rupture on the Main Pamir Thrust revealed by GPS and In SAR

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.

THE CENTRAL PAMIR—AN ALPINE COLLISION ZONE

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.

Early Cretaceous deformation in the southern Tashkorgan region: Implications for the tectonic evolution of the northeastern Pamir

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.

TECTONIC TRANSFER ON THE EASTERN EDGE OF PAMIR

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.

THE NORTHWARD PROPAGATION OF THE ARC TECTONICS OF THE NORTHEAST PAMIR AND NORTHWEST TARIM BASIN

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.

PETROLOGIC AND GEOCHRONOLOGIC STUDIES

The model of extrusion tectonics for the accommodation of the Indo\|Asian collis i on requires the presence of large\|scale strike\|slip faults with hundreds of ki lo meters of displacement. Along the western edge of the Tibetan Plateau, the Kara koram fault, extending ～900[KG*9]km from the central Pamir to western Tibet, ha s been proposed as one of these accommodating faults. At the northern terminus of the Karakoram fault lies the west\|southwest dipping Kongur Shan detachment f ault system. As the two systems have been proposed to be kinematically linked, constraining the amount of slip along the Kongur Shan detachment system helps d etermine the total displacement along the Karakoram fault system. This in turn will co nstrain the applicability of extrusion tectonics models for the Indo\|Asian coll ision. [KH*2] Detailed geologic mapping was conducted in the northern Kongur Shan region along the Gezi River and near the village of Qiake lake. Kinematic indicators f rom rocks directly below the fault, such as rotated crystals, asymmetric boundar y, and S\|C fabrics, show a normal sense of shear. The detachment fault in th e area dips between 35° to 45° to the east. A thin zone of chloritic breccias, a few meters thick, is locally exposed directly below the fault. Mylonitic gneisse s ＞2[KG*9]km thick are present in the footwall. The strike of mylonitic foliat ions c hanges systematically and, together with the domal geometry of a deformed grani tic body, define a gneiss dome in the footwall. Associated with the variation i n the strike of foliation is a systematic change in the trend of the mylonitic l ineation. Their trend is to the west directly below the fault, but changes to the northwest farther away from the fault. Rocks in the footwall of the detachm ent fault are composed of biotite and muscovite schists (quartz, plagioclase, bi otite, muscovite, +/-garnet, +/-epidote), and deformed granitite sills and sh ee t\|like bodies. Preliminary petrologic studies indicate that these rocks have ex perienced upper greenschist to lower amphibolite facies metamorphism.