Constraining the crustal structure under the central and western Tian Shan based on teleseismic receiver functions and gravity anomalies

The Tian Shan is a vast range that spans several countries in Asia.Understanding its evolutionary history may provide valuable insights into intracontinental orogenic dynamics.In this study,we explored the crustal characteristics of the Tian Shan and their relationships to the tectonic evolution of the region.A new H-stacking method that combines the P receiver function and gravity anomalies was used to estimate the thickness and ratio of P-to S-wave velocities(Vp/Vs)for 91 broadband seismic stations in the central and western Tian Shan.Our results revealed significant lateral variations in crustal thickness and Vp/Vs.A—45-km-thick crust and an intermediate-high Vp/Vs(-1.74-1.84)were found in the Kazakh Shield and Tarim Basin,which we interpreted to indicate a mafic crystalline basement and lower crust.The central Tian Shan varied greatly in crustal thickness(40-64 km)and Vp/Vs ratio(1.65-2.00).which may be due to crustal shortening,mafic underplating,and crustal melting.In contrast,we observed a relatively thin crust(42-50 km)with an intermediate Vp/Vs ratio(-1.78)in the western Tian Shan.The differences in the crustal structures between the western and central Tian Shan imply that the Talas-Fergana Fault may be trans-lithospheric.

Multistage Enrichment of the Sawafuqi Uranium Deposit: New Insights into Sandstone-hosted Uranium Deposits in the Intramontane Basins of Tian Shan, China

Meso-Cenozoic intracontinental orogenic processes in the Tian Shan orogenic belt have significant effect on the sandstone-hosted uranium deposits in the intramontane basins and those adjacent to the orogen. The Sawafuqi uranium deposit, which is located in the South Tian Shan orogenic belt, is investigated to reveal the relationships between uranium mineralization and orogenies. Recent exploration results show that the Sawafuqi uranium deposit has tabular, stratiform, quasi-stratiform, and lens-like orebodies and various geological characteristics different from typical interlayer oxidation zone sandstone-hosted uranium deposits. Systematic studies of ore samples from the Sawafuqi uranium deposit using a variety of techniques, including thin section observation, a-track radiograph, electron microprobe and scanning electron microscope, suggest that uranium mineralization is closely related to pyrite and organic matter. Mineralization-related alterations in the host rocks are mainly silicification and argillation including kaolinite, illite （and illite-smectite mixed layer） and chlorite. Tree stages of mineralization were identified in the Sawafuqi uranium deposit： （i） uranium-bearing detritus and synsedimentary initial pre-enrichment; （ii） interlayer oxidization zone uranium mineralization; and （iii） vein-type uranium mineralization. The synsedimentary uranium pre-enrichment represents an early uranium enrichment in the Sawafuqi uranium deposit, and interlayer oxidation zone uranium mineralization formed the main orebodies, which are superimposed by the vein-type uranium mineralization. Combining the results of this study with previous studies on the Meso-Cenozoic orogenies of South Tian Shan, it is proposed that the synsedimentary uranium pre-enrichment of the Sawafuqi uranium deposit was caused by Triassic Tian Shan uplift, and the interlayer oxidation zone uranium mineralization occurred during the Eocence-Oligocene period, when tectonism was relatively quiet, whereas the vein-type uranium mineralization took place in relation to the strong orogeny of South Tian Shan since Miocene.

LATE CENOZOIC TECTONICS ALONG THE NORTHWESTERN MARGIN OF THE TARIM BASIN: INTERACTIONS BETWEEN THE TARIM BASIN AND THE SOUTHERN TIAN SHAN, WEST CHINA

The Late Cenozoic fold\|and\|thrust zone along the northwestern margin of the Tarim Basin and the adjacent Tian Shan of Central Asia is an actively deforming part of the India\|Asia collision system. This deformation zone has two remarkable oppositely vergence arcuate fold\|and\|thrust systems (Kepingtage and Kashi\|Atushi fold\|and\|thrust belts) reaching from east of Keping to west of Kashi. This shape is manifested by structure, topography and seismicity. From north to south, this deformation zone is characterized by four main kinematic elements: (1) a hanging\|wall block (Maidan fault and Tuotegongbaizi\|Muziduke thrust system) that represents the Cenozoic reactivation of a late Paleozoic thrust system; (2) an imbricated thrust stack (Kepingtage\|Tashipeshake thrust system) where slices of Tarim platform sediments are thrust south toward the basin; (3) the Kashi\|Atushi fold\|and\|thrust system where thrusting and folding verge toward the Tian Shan; (4) a foot\|wall block (Tarim craton) that dips gently northwest below the sediment\|filled southern Tian Shan basin and generally has little internal deformation.

The Major Two-stage Shortening Deformation of the Northern Tibet and Tian Shan Area Since the Latest Oligocene

It seems to be progressively recognized that the stress of the India-Asia convergent front can be transferred rapidly through the southern and central Tibetan lithosphere to the northern Tibet, hence leading to the crustal thickening deformation there during or immediately after the onset of the India-Asia collision（ca.55 Ma）.This study focuses on the late Cenozoic deformation and tectonic uplift of the northern Tibet and Tian Shan area.Detailed compilations of a variety of proxy data from sediments and bedrocks suggest that the northern Tibet and Tian Shan area underwent one stage of approximately synchronous widespread contractile deformation since 25–20 Ma, which seemed to decrease at circa 18 Ma as revealed by low-temperature thermochronological data.The latest Oligocene-early Miocene was also significant basin-forming episodes when many intermontane subbasins began to receive syntectonic sedimentation in the northeastern Tibet.Subsequently, the other phase of compressional deformation began to encroach more widely into the northern Tibet and Tian Shan area in episodic steps or continuously from 16–12 Ma to present.

Paleoseismological Study of the Late Quaternary Slip-rate along the South Barkol Basin Fault and Its Tectonic Implications,Eastern Tian Shan,Xinjiang

The easternmost Tian Shan lies in eastern Xinjiang, Central Asia. The South Barkol basin fault（SBF） in the northern part of the easternmost Tian Shan is a major tectonic structure in this orogenic region. The late Quaternary activity, paleoseismology, and deformation characteristics of the fault provide important clues for understanding the tectonic process of the eastern Tian Shan orogen and implementing seismic mitigation. Through interpretation of high-resolution satellite images, unmanned aerial vehicle measurements, and detailed geological and geomorphic investigations, we suggest that the fault exhibits clear left-lateral slip along its western segment. Paleoseismic trenches dug near Xiongkuer reveal evidence of six large paleoearthquakes. The four latest paleoearthquakes were dated： the oldest event occurred at 4663 BC–3839 BC. Data on the horizontal offsets along the probable 1842 Barkol earthquake coseismic rupture suggest clear multiple relationships between cumulative offsets and possible ~4 m of coseismic left-lateral slip per event. From the cumulative offsets and 14 C sample ages, we suggest an average Holocene left-lateral slip rate of 2.4–2.8 mm/a on the SBF, accounting for ~80% of lateral deformation within the entire eastern Tian Shan fault system. This result is comparable with the shortening rate of 2–4 mm/a in the whole eastern Tian Shan, indicating an equal role of strike-slip tectonics and compressional tectonics in this orogen, and that the SBF may accommodate substantial lateral tectonic deformation.

Physico-chemical Characteristics and Environmental Significance of Snow Deposition on Haxilegen Glacier No.51 in Tian Shan,China

Snow chemistry on the glaciers of alpine regions is a good indicator of atmospheric environmental change.We examine snow chemistry in three snowpits at different altitudes on the Haxilegen Glacier No.51,in the Kuitun River source,Tian Shan,China,during July-September 2004 to 2007.We use correlation analysis,factor analysis and sea-salt tracing methods to examine the characteristics and sources of major ions and mineral dust particles in the snow.Results show that mineral dust particles and major ions in the snow pits vary seasonally.During the Asian dust period in springtime,the concentration of mineral dust particles and major ions deposited in snow is high,while the concentration is relatively low during the non-dust period of summer and autumn.This may be caused by dust storm activity in central Asia.The order of major ionic concentrations in the snow packs was determined to be Ca2+ > SO42-> NH4+ > NO3-> Cl-> Na+ > Mg2+ > K+.Ca2+ was the dominant cation;SO42- was the dominant anion.We find,with the exception of NO3-,that the variabilities of ionic concentrations are highly correlated.Results show that the glacier region was significantly affected by dust activity and anthropogenic source.The major ions,especially Na+,originate from dust sources of central Asia and from the Ocean,transported by the westerly winds.

Apatite U–Pb dating and geochemistry of the Kyrgyz South Tian Shan(Central Asia): Establishing an apatite fingerprint for provenance studies

This paper presents an apatite U-Pb and geochemistry archive for exposed plutons and metamorphic rocks of the Kyrgyz South Tian Shan(STS)within the Central Asian Orogenic Belt.Apatite U-Pb dates and trace-element geochemistry are provided for 17 samples from late Carboniferous-early Permian I-type granites in the Terktinsky complex and A-type granites in the Kokshaal Range;early Devonian granites in the Kembel complex;Cryogenian granitoids and tuffs from the Middle Tian Shan and gneisses from the Atbashi metamorphic complex.These samples form a comprehensive selection of igneous and metamorphic rocks within the cores of Mesozoic basement highs that supplied detritus to adjacent basins such as the Tarim,Ferghana and Yarkand-Ferghana Basins.Generally,the granitoid samples preserve primary igneous apatite U-Pb ages that are within uncertainty of previously published zircon U-Pb dates.The apatites from the Atbashi metamorphic complex record anomalous Ordovician dates with large uncertainties that are interpreted as mixing ages between Cryogenian protolith formation and Carboniferous metamorphism.Principal component analysis discriminates apatite samples from the different bedrock terranes in the Kyrgyz STS based on their geochemical fingerprint and categorizes the samples with respect to an extensive apatite geochemical archive.The combined apatite-zircon archive provides a novel framework for provenance studies on the Meso-Cenozoic sedimentary history of the Central Asian Orogenic Belt.

Mapping the Late-Holocene Glacial Geomorphology and Glacier Surface Types in the Mt. Harajoriha, Central Tian Shan

Alpine glaciers in the central Tian Shan are an important indicator of climate change and also the freshwater tower for the transboundary countries in Central Asia. Knowledge about the glacier dynamics in the late Holocene, such as the Little Ice Age, and surface zones is still limited. In this study, two headwater basins, the Xiata and the Muzart basins, in the Harajoriha Mountain Range in northwestern China were selected to investigate the glacial landforms and glacier surface types using a combination of geomorphological mapping and remote sensing analysis. Several types of glacial landforms including glacial valleys, moraine complexes, moraine ridges, and trimlines were identified and manually digitized based on the 30 m Shuttle Radar Topography Mission (SRTM) digital elevation model, 10 m Sentinel-2 satellite imagery, and high-resolution images from Google Earth. In addition, an effective automated mapping algorithm was applied to the modern glaciers from a Landsat 8 scene using its optical and thermal bands to classify glacier facies, i.e. ice, snow, and slush zone, and supraglacial debris cover. Field trip to the forelands of the Aerqialeteer Glacier in the Xiata basin allowed detailed mapping of the proglacial environment and provided field checks for the mapping with GPS tracks and panoramic photos. Through this fused approach, the mapping results showed a combination of different sets of information connecting the glacier retreat since the late Holocene to contemporary glacier properties. They will be of particular value for future chronological reconstruction of past glacial events and for understanding how surface characteristics play a role in the heterogeneity of glacier responses to climate change.

Organochlorine pesticides in soils from the Issyk-Kul region in the western Tian Shan Mountains,Kyrgyzstan：Implication for spatial distribution,source apportionment and ecological risk assessment

As organchlorine pesticides(OCPs) may be an ecologic threat to mountain environments due to their tendency to deposit and accumulate in mountain regions undergoing long-range air transport, OCPs were analyzed in soils collected from an intermontane basin of the western Tian Shan Mountains, which is the UNESCO protected natural reserve of Issyk-Kul. Total OCP concentrations in the Issyk-Kul region ranged from 4.63 to 414 ng/g dw, of which two extraordinary high OCP concentrations(414 ng/g dw and 213 ng/g dw, respectively) influenced by an abandoned dumping site and urban sewage, respectively, were found. Principal component analysis(PCA) and correlation analysis inferred that the OCP inputs in the east of the Issyk-Kul region were mainly from local endogenous sources, and exogenous input via LRAT processes were prominent in the west and south. Additionally, the isomeric and parent substance/metabolite ratios revealed most pesticides accumulated in this region were from old usage, while DDTs had fresh input because of possibly illegal regional application and a slow degradation from the dumping site. Furthermore, ecological risk assessment revealed that no frequently adverse ecological effects were observed in the Issyk-Kul region, but potential risks on neighbouring organisms induced by p,p'-DDT and γ-HCH in dumping site and urban sewage should be considered when devising an efficient management plan to prevent secondary pollution.

Early Palaeozoic Granites in the Northern Tian Shan,Kyrgyzstan:Their Zircon Ages and Evolution Processes

The Tian Shan Orogenic Belt, which is a subsidiary of the Central Asian Orogenic Belt, is the largest accretion area of continental crust on the Earth during the Phanerozoic. It has experienced several accretionary processes during the Palaeozoic period and has attracted much concern among geologists. An Early Palaeozoic intrusive rock belt extends for 1000 km from east to west, occupying about 40% of the total area within the Kyrgyz Northern Tian Shan Orogenic Belt. Previous studies show that the petrology of these rocks is similar, consisting of granites and granodiorites.

基于弹性板模型的塔里木盆地北部新生代沉降模拟:对南天山隆升的启示

在印度-欧亚板块碰撞远程效应影响下,天山造山带在新生代活化隆升,与其南缘相邻的塔里木盆地北部发生挠曲沉降并沉积了巨厚的新生代地层,该巨厚新生代地层和造山沉积地层为本文进一步探究南天山隆升过程提供了关键的沉积记录。本文采用有限弹性板数值模拟的方法,对盆地新生代不同时期基底沉降剖面分别进行建模研究。结果表明:盆地沉降受沉积负载和构造负载共同控制,66~<5.3 Ma期间沉积负载对盆地沉降的贡献量小于或等于构造负载的贡献量;约5.3 Ma至今沉积负载对盆地沉降的贡献量远大于构造负载。南天山构造负载变化速率表现为66~<26.3 Ma缓慢增长;26.3~<5.3 Ma南天山稳定增长;约5.3 Ma至今南天山造山带构造负载高度快速增长。基于对盆地沉降过程的分析,限制南天山新生代初始隆升时间为古近纪,其相对海拔高度从400 m增长到2 500 m;虽然在约5.3 Ma至今南天山相对海拔高度保持稳定,但构造负载高度仍在增加,这可能是盆地俯冲作用的加剧在一定程度上抑制了造山带平均海拔高度的增长,进而导致南天山的侵蚀和隆升达到相对平衡。

Response of runoff and its components to climate change in the Manas River of the Tian Shan Mountains

A warming-wetting climate trend has led to increased runoff in most watersheds in the Tian Shan Mountains over the past few decades.However,it remains unclear how runoff components,that is,rainfall runoff(Rrain),snowmelt runoff(Rsnow),and glacier meltwater(Rglacier),responded to historical climate change and how they will evolve under future climate change scenarios.Here,we used a modified Hydrologiska Byrans Vattenbalansavdelning(HBV)model and a detrending method to quantify the impact of precipitation and temperature changes on runoff components in the largest river(Manas River)on the northern slope of the Tian Shan Mountains from 1982 to 2015.A multivariate calibration strategy,including snow cover,glacier area,and runoff was implemented to constrain model parameters associated with runoff components.The downscaled outputs of 12 general circulation models(GCMs)from the Sixth Coupled Model Intercomparison Project(CMIP6)were also used to force the modified HBV model to project the response of runoff and its components to future(2016-2100)climate change under three common socio-economic pathways(SSP126,SSP245,and SSP585).The results indicate that Rrain dominates mean annual runoff with a proportion of 42%,followed by Rsnow(37%)and Rglacier(21%).In terms of inter-annual variation,Rrain and Rsnow show increasing trends(0.93(p<0.05)and 0.31(p>0.05)mm per year),while Rglacier exhibits an insignificant(p>0.05)decreasing trend(-0.12 mm per year),leading to an increasing trend in total runoff(1.12 mm per year,p>0.05).The attribution analysis indicates that changes in precipitation and temperature contribute 8.16 and 10.37 mm,respectively,to the increase in runoff at the mean annual scale.Climate wetting(increased precipitation)increases Rrain(5.03 mm)and Rsnow(3.19 mm)but has a limited effect on Rglacier(-0.06 mm),while warming increases Rrain(10.69 mm)and Rglacier(5.79 mm)but decreases Rsnow(-6.12 mm).The negative effect of glacier shrinkage on Rglacier has outweighed the positive effect of warming on Rglaciers resulting in the tipping point(peak water)for Rglacier having passed.Runoff projections indicate that future decreases in Rglacier and Rsnow could be offset by increases in Rrain due to increased precipitation projections,reducing the risk of shortages of available water resources.However,management authorities still need to develop adequate adaptation strategies to cope with the continuing decline in Rgacier in the future,considering the large inter-annual fluctuations and high uncertainty in precipitation projection.

基于BSO-BP改进动态帧时隙算法的密集环境下RFID标签读写优化方法

无线射频识别技术作为物联网的关键技术,正在不断发展并广泛应用于我国制造业领域。为了解决大量无线射频识别标签读写时相互竞争信道而产生的数据碰撞现象,需要对标签数量进行准确估计。文章在传统动态帧时隙算法的基础上,利用天牛群搜索算法寻找BP神经网络的最优初始权值和阈值,并将最优值应用到BP神经网络的参数设定中,实现了对标签数量的准确估计。通过实验和企业实际使用RFID绑定电源线的生产效果证明,与传统的动态帧时隙算法相比,所提出的改进算法既保证了读取的准确性,又缩短了读取时间,有效地提高了系统的效率。

Meso-Cenozoic tectonic evolution of the Talas-Fergana region of the Kyrgyz Tien Shan revealed by low-temperature basement and detrital thermochronology

This study provides new low-temperature thermochronometric data, mainly apatite fission track data on the basement rocks in and adjacent to the Talas-Fergana Fault, in the Kyrgyz Tien Shan in the first place.In the second place, we also present new detrital apatite fission track data on the Meso-Cenozoic sediments from fault related basins and surrounding intramontane basins. Our results confirm multistaged Meso-Cenozoic tectonic activity, possibly induced by the accretion of the so-called Cimmerian blocks to the Eurasian margin. New evidence for this multi-staged thermo-tectonic activity is found in the data of both basement and Meso-Cenozoic sediment samples in or close to the Talas-Fergana Fault.Zircon(U-Th)/He and apatite fission track data constrain rapid Late TriassiceE arly Jurassic and Late JurassiceE arly Cretaceous basement cooling in the Kyrgyz Tien Shan around 200 Ma and 130 -100 Ma respectively. Detrital apatite fission track results indicate a different burial history on both sides of the Talas-Fergana Fault. The apatite fission track system of the Jurassic sediments in the Middle Tien Shan unit east of the Talas-Fergana Fault is not reset, while the Jurassic sediments in the Fergana Basin and Yarkand-Fergana Basin, west of the fault zone, are partially and in some cases even totally reset. The totally reset samples exhibit Oligocene and Miocene ages and evidence the Cenozoic reactivation of the western Kyrgyz Tien Shan as a consequence of the India-Eurasia convergence.

天山北麓河流下游冲积平原沉积记录的中晚全新世环境演变

天山北麓河流下游冲积平原与古尔班通古特沙漠交汇带,沉积环境独特,对全球气候变化响应敏感。囿于年代校正不确定性、代用指标的多解性以及地形地貌格局等因素的影响,该区域全新世时期沉积环境演变过程和气候演化模式研究,尚存在不同认识。重建该区域的中晚全新世环境演变历史及其对气候变化的响应过程,有助于加深对天山北麓冲积平原沉积环境演化时空特征的认识。本文选取天山北麓中部河流下游冲积平原四个典型冲积-湖积-风积地层剖面为研究材料,以光释光(OSL)测年确定地层绝对年代,综合沉积构造特征、沉积物粒度参数和石英砂表面微结构特征分析,探讨河流下游中晚全新世冲积-湖积平原沉积序列的演变过程和驱动因素。结果表明:(1)研究剖面主要由黏土、粉砂和极细砂含量较高的河湖相沉积构成,靠近北部沙漠边缘以极细砂、细砂为主的风成砂层明显增多,形成以冲积相、湖沼相和风沙相交替叠覆的沉积序列,其沉积相组合具有明显的时空变化特征;(2)沉积物石英颗粒表面常见冰川、流水、风力等多种外营力作用的痕迹,表明河流下游平原沉积物主要来源于山区冰川搬运、磨蚀的碎屑物质,并经流水和风力分选后成为古尔班通古特沙漠的重要物源;(3)7.59~6.0 ka河流活动频繁,广泛发育河湖相沉积,为相对暖湿气候期;6.0~4.25 ka期间,多地出现风沙活动,气候短暂转干,湿度有所降低;4.25 ka以来,发育冲洪积、湖积和风成沙交互沉积,气候“温湿-凉干”周期性波动。本文各剖面沉积序列综合揭示中全新世以来的沉积环境演变过程既有全球气候变化影响的共性特征,又有干旱区山麓地带大地貌控制的区域特点,这对预测未来沙漠边缘风沙活动变化趋势、合理利用淡水资源,从而构建区域生态安全屏障具有重要意义。

Widespread glacier advances across the Tian Shan during Marine Isotope Stage 3 not supported by climate-glaciation simulations

Whether there were more extensive glaciations during the Marine Isotope Stage(MIS)3 relative to MIS 2 across the Tian Shan in Central Asia is intensely debated because of the uncertainty in chronological data and fully understanding the driving mechanisms.To help resolve the ongoing debate,we assess the climate sensitivity of the glaciers and reconstruct the extent of glaciation during MIS 2 and 3 across the Tian Shan,using a glacier-resolving(250×250 m)ice sheet model asynchronously coupled with a global climate model.Our results demonstrate that the equilibrium-line altitude(ELA)over the Tian Shan decreases by∼180 m for every 1°C cooling under a modern precipitation regime,but precipitation reduction greatly lowers the sensitivity of the glaciers to temperature decrease(e.g.,the effect of 2°C cooling is broadly offset by a 50%decrease in precipitation).Under the modeled colder/drier-than-present climate,the model predicts an ELA depression(∆ELA)of∼75 m(162 m)over the Tian Shan during MIS 3 interstadials(stadials).The extent of MIS 3 glaciation is much smaller than that during MIS 2(i.e.,∆ELA=∼726 m).The more extensive glaciation during MIS 2 is largely attributed to the enhanced summer cooling.Furthermore,through a site-to-site model-data comparison,we find that the closest match between the modeled glacier margin and the locations of the glacial deposits previously argued to be MIS 3 is generally achieved under MIS 2 climatic conditions.These results suggest more extensive glacier advances over the Tian Shan during MIS 2 than MIS 3 on a regional scale,although MIS 3 glaciation may still occur in individual glacier catchments.This pattern suggests general synchronicity with the timing of maximum Northern Hemisphere ice sheets during the last glacial,which should be further tested in a multimodel framework in the future.

中天山阿拉斯台地区志留纪侵入岩年代学、地球化学特征及其构造意义

为探讨中天山阿拉斯台一带侵入岩的岩石成因、形成时代及其构造环境,对侵入岩(闪长岩、花岗闪长岩)样品进行了激光剥蚀等离子质谱(LA-ICP-MS)锆石U-Pb定年和岩石地球化学研究。结果显示,阿拉斯台一带侵入岩侵位于早志留世[(433±3.1)Ma,(436.7±1.5)Ma],具有较高的SiO_(2)(58.19%~68.75%)、MgO(1.34%~3.17%)、和Na(K_(2)O/Na_(2)O=0.16~0.57)含量;稀土元素配分型式呈右倾型,具有铕弱负异常到正异常(δEu=0.85~1.34);富集大离子亲石元素(LILE)Ba、Rb和Th,亏损高场强元素(HFSE)Nb、Ta、Ti和P;具有高Sr低Yb、较高La_(CN)/Yb_(CN)值(6.87~42.01)。以上特征表明,阿拉斯台侵入岩与俯冲洋壳型埃达克岩特征相似;再结合区域地质资料,认为阿拉斯台一带志留纪侵入岩的源岩可能为壳幔混源岩浆,是与南天山洋盆北向俯冲有关的产物。

新疆伽师强震群区三维地壳上地幔S波速度结构及其地震成因的探讨

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