Chinese Tianshan Research Articles

Investigating the influence of climate on the evolution of fold-and-thrust belts in Chinese Tianshan: A 2D doubly vergent numerical model approach

In most analogue and numerical modelling studies for investigating the evolutionary mechanisms of fold-and-thrust belts, the initial models are typically designed as “sandboxes” with one side fixed in the horizontal direction. However, such model setup has neglected the potential effects of drainage divide migration. To address this issue, in this study we developed a 2D doubly vergent numerical model that accounts for drainage divide migration to investigate the structural evolution in Tianshan fold-and-thrust belts since the late Cenozoic, with an emphasis on the influences of climatic forcing on rock deformation. The deformation styles of northern and southern Tianshan fold-and-thrust belts exhibit significant differences, with the northern Tianshan fold-and-thrust belt characterized by deep isoclinal anticlines, whereas the southern Tianshan fold-and-thrust belts are dominated by thrust faults and minor shallow-level tight anticlines. Our modelling results suggest that such differences in deformation style may be attributed to the north–south precipitation gradient across Tianshan mountain. The results also show that unilateral climatic perturbations can lead to migration of the drainage divides towards the side with lower precipitation, thereby impacting the structural evolution on the opposite side of the mountain range. Such impact mainly manifests as an increased tendency to develop more thrust faults in the direction toward which the drainage divide is shifting. This provides a new perspective for reevaluating the patterns of tectonic evolution in the global orogenic belts since the late Cenozoic.

Unraveling the deposition and incision paces of alluvial fan-river system by using single grain K-feldspar luminescence dating

Alluvial river in the piedmont area deposits and incises cyclically, in response to both exogenetic and endogenetic forcing across a range of timescales. The paces of these processes unveil the mechanisms governing the evolution of alluvial fan-river system and affect the policy for river management. Numerical simulation suggests that the incision of alluvial river is much faster than the deposition process. However, the field observations are rare. Alluvial rivers entrench up to 300 m into the alluvial fans built pre-Holocene on the northern piedmont of Chinese Tianshan, which provide ideal sites to unveil the pace of alluvial fan-river evolution. Jingou River is one of these rivers, with four levels of terraces identified at the downstream area. These terrace deposits are characterized by a complex of upper very coarse gravels and cobble (VCGC) unit and lower medium and coarse gravels (MCG) unit. In this study, potassium-feldspar (K-feldspar) single grain pIR110IR170 luminescence dating procedure was employed to date the samples taken from sandy lens of both upper VCGC and lower MCG units, for which the depositional ages are supposed to be associated with the fan-building and river incision processes, respectively. The luminescence ages of the lower MCG unit suggests a gradual fan building phase between 16 ± 1.9 ka and 8.1 ± 0.9 ka, while the ages of the upper VCGC unit cluster around ∼5.2 ka rather than a monotonic decrease towards low level terraces. Several scenarios are discussed with respect to the attained age sequences to unravel the pace of deposition and incision of Jingou River, of which the asymmetric aggradation and incision is more preferred and echoes to the finding of previous numerical investigation.

A CMIP6-based assessment of regional climate change in the Chinese Tianshan Mountains

A CMIP6-based assessment of regional climate change in the Chinese Tianshan Mountains

The Upper Paleozoic on the northern margin of the Tarim minor continent as a non-classical foredeep trough (evolution, tectonics, comparison)

New data on the stratigraphy and structure of the Pre-Kokshaal foredeep (Kyrgyz and Chinese Tianshan), fragments of which have been preserved on the northwestern edge of the Tarim continental massif, now in the Ferghana, Kokshaal and Kharke ridges, are presented. The foredeep emerged when the Turkestan ocean closed and the South Tianshan collisional structure built at the end of the Carboniferous and the beginning of the Permian, about 310 - 290 Ma. The next parts of the Pre-Kokshaal foredeep may be highlighted. 1) The inner zone, which is superimposed on the distal part of the former slope of the Tarim continent and filled with Moscowian – Kasimovian turbidites, then folded and thrusted to the southeast. 2) To the south, outer zone, which corresponds to the proximal part of the slope, where the same events and structures developed here later, in the Gzhelian – Asselian. Analogues of these mostly flysch zones are usually not included as parts of the Pre-Ural, Prealpine and other classic foredeeps, where they are completely captured into the thrust complexes. 3) Marginal zone of the Pre-Kokshaal trough was loaded with thick clastic deposits only in the Gzhelian, but already at the beginning of the Permian its subsidence compensated, and the flysch was covered by Asselian limestones. After the Asselian thrusts in the Ferghana Ridge and less significant deformations in the east, development of the foredeep towards the south apparently stopped under the influence of the Tarim mantle plume, which facilitated the separation of the mantle slab and led to thickening and heating of the Tarim continental crust. After the Hercynian collision completed, in the Late Cenozoic the Pre-Kokshaal Upper Paleozoic foredeep experienced intracontinental transverse compression and surface shortening, when it completely disappeared in the east of the Tien Shan, but supplemented from the south by a new Cenozoic molasse trough.

Dynamic simulation and projection of land use change using system dynamics model in the Chinese Tianshan mountainous region, central Asia

A critical step in alleviating the contradiction between human activities and land systems is to project and analyze land use change traits in various scenarios to furnish a basis for formulating economic development and ecological conservation strategies. However, few studies have examined land use change using the system dynamics (SD) model and patch-generating land use simulation (PLUS) model in the Chinese Tianshan mountainous region (CTMR) affected by different economic growth patterns and climate change contexts. Therefore, based on the Shared Socioeconomic Pathways and Representative Concentration Pathways (SSPs-RCPs) scenarios, we attempted to construct a regional SD model (RSDM) including population, economic, land, and climate subsystems. Then, the coupled model by combining RSDM and PLUS was employed to simulate and project land use/cover changes (LUCC) in the CTMR at the regional level to explore the spatial distribution of land and its pattern of change in different climate contexts. The SD model is an effective method that can simulate the nonlinear behavior of a complex system and predict its evolution through the interactions and feedback relationships between different influencing factors. The PLUS model is an effective tool that can be used to simulate the evolution of land patches and capture the extent to which the driving factors contribute to LUCC. The relative errors were less than 5%, and the total accuracy of PLUS model was 91.77%. The above results demonstrated the effectiveness of RSDM and PLUS model in modeling LUCC across the CTMR. From 2005 to 2020, there was an expansion trend in the area of forest and construction land as well as in the area of cultivated land, while the grassland area displayed a significant decline. By 2040, the area of unused land, grassland, and water is expected to demonstrate a decreasing trend while other land types increase, with construction land showing the most significant increase of 101.37% under the SSP585 scenario. It is anticipated to expand mainly to cultivated land and grassland around cities. The cultivated land is expected to primarily encroach on the regions of unused land and grassland under the three scenarios, reaching the expansion demand. As opposed to the scenarios of SSP126 and SSP245, the SSP585 scenario distribution of the cultivated land patches will be more compact and denser. The SSP126 and SSP245 scenarios will exhibit similar patterns of future spatial distribution of land. The SSP585 scenario is anticipated to display marked differences. According to the three scenarios, grassland degradation will be severe and require increased grassland protection. The findings can offer novel perspective concepts with regard to future ecological and environmental management, judicious distribution of land resources, and sustainable progression in the CTMR.

Increased Vegetation Productivity of Altitudinal Vegetation Belts in the Chinese Tianshan Mountains despite Warming and Drying since the Early 21st Century

Gaining a deep understanding of how climate change affects the carbon cycle in dryland vegetation is of utmost importance, as it plays a pivotal role in shaping the overall carbon cycle in global ecosystems. It is currently not clear how plant communities at varying elevations in arid mountainous regions will respond to climate change in terms of their productivity. The aim of this study was to investigate the effect of climate change on vegetation productivity in different altitudinal vegetation belts of the Tianshan Mountains between 2000 and 2021, utilizing satellite-derived vegetation productivity and climate data. The findings suggest a notable increase in vegetation productivity across diverse altitudinal vegetation belts. The productivity of vegetation in the coniferous forest and alpine meadow belts displayed a notably higher interannual trend compared to other vegetation belts. Notably, an increase in vegetation productivity was accompanied by warming and drying. The productivity of altitudinal vegetation belts, however, appears to be resilient to current climate trends and was not significantly impacted by the severity of atmospheric drought. The trend of increased vegetation productivity was primarily driven by CO2 fertilization. Our results highlight that the extent of climate change may need to reach a threshold to noticeably affect variations in vegetation productivity in arid mountainous.

The Late Carboniferous Mafic–Ultramafic Complex Induced by Slab Breakoff in Eastern North Tianshan, Central Asian Orogenic Belt

The Late Carboniferous to Early Permian is a critical period of the Chinese Tianshan, witnessing the tectonic transition from subduction to post-collisional extension during the final amalgamation of the Central Asian Orogenic Belt (CAOB). The late Carboniferous Mozbaysay mafic–ultramafic complex in the Qijiaojing–Balikun area, eastern North Tianshan, provides important clues for revealing the nature and timing of this tectonic transition. The Mozbaysay complex comprises mainly hornblende gabbros and lherzolites. LA-ICP-MS U-Pb zircon ages of hornblende gabbro yielded a weighted mean age of 306 ± 1.9 Ma for this complex. These mafic–ultramafic rocks have high contents of MgO (up to 30 wt.%), Cr (up to 2493 ppm), and Ni (up to 1041 ppm), but low contents of SiO2 (40.34–47.70 wt.%). They are enriched in LREE and show characteristics of enriched mid-ocean ridge basalts (E-MORB). The relatively high Th/Yb and Ba/Nb ratios imply the mantle sources could have been metasomatized by slab–mantle interaction with aqueous fluids from dehydration of the subducted slab. Thus, these mafic–ultramafic rocks were most likely produced by partial melting of the asthenospheric and lithospheric mantle with a slight influence of slab-derived fluids. Therefore, we suggest that the formation of these Late Carboniferous mafic–ultramafic rocks was triggered by the decompression-induced influx of asthenospheric heat and melting through a slab window during post-collisional slab breakoff. Combined with geological data, the petrogenetic links of the Late Carboniferous mafic–ultramafic rocks in eastern North Tianshan to slab breakoff suggest that the tectonic transition from convergence to post-collision most likely initiated in situ at ca. 306 Ma and lasted to ca. 300 Ma.

Multiple stages of Au mobilization in the Changshagou Au deposit, Eastern Tianshan, NW China: Insights from mineral chemistry and fluid inclusions

Gold deposits involving multiple stages of mineralization have received considerable attention, but the relationship between these Au enrichment episodes remains enigmatic. The Changshagou Au deposit in the Chinese Tianshan Orogenic Belt exhibits two contrasting styles of mineralization. Early stockwork disseminated sulfide mineralization is associated with potassic alteration and acid magmatic fluids (log fO2 = -30 to -25, pH = 3 to 6), whereas late auriferous vein mineralization is associated with silicification and weakly alkaline hydrothermal fluids (log fO2 = -35 to -32, pH = 4 to 8). Early mineralization (average Au grade = 1.8 g/t) is dominated by invisible gold in sulfides, whereas late mineralization (average grade = 3.7 g/t) contains abundant native gold (fineness = 799 to 872). Fluids with high Au solubilities (∼104 ppb) from the late-stage mineralization remobilized pre-existing Au and formed As-enriched overgrowth bands on pyrite, with the core of these pyrite containing up to 1800 ppm Au, but little As, and their rim containing up to 4300 ppm As, but little Au. Subsequent fluid boiling accompanied with the escape of CO2 and H2S elevated the pH and redox state of the fluid (log fO2 = -32 to -28, pH >8), which caused a decrease in Au solubilities and precipitation of native gold (average grade = 28.6 g/t). In summary, we suggest the Changshagou Au deposit formed as a result of three key processes — pre-enrichment, re-mobilization, and re-enrichment — all of which are important to the formation of Au deposits characterized by multiple stages of mineralization.

Recent decreasing precipitation and snowmelt reduce the floods around the Chinese Tianshan Mountains

Understanding and managing mountain floods has become increasingly urgent, with global climate change and human activities exacerbating flood risk. However, flood research in Tianshan Mountains, a typical flood-prone mountainous region in China, is still insufficient. Here, we customized a set of flood research methods based on rainstorms and extreme snowmelt events, including a new flood counting method that comprehensively considered the frequency and magnitude of floods and the methods of flood classification and change attribution. We found that floods around the Chinese Tianshan Mountains (CTM) increased from 2014 to 2016 but decreased rapidly from 2016 to 2021, with storm floods, snowmelt floods, and mixed floods accounting for 38.3 %, 26.5 %, and 34.6 % of total flood events, respectively. The variation of floods was most significantly correlated with the average and extreme precipitation, followed by the temperature-driven average snowmelt change. Furthermore, atmospheric circulation anomalies and water vapor input from the western boundary of CTM caused decreasing precipitation and storm floods. Meanwhile, the warming hiatus also greatly impacted declining flood frequency. Notably, flood frequency is projected to rebound soon because of the rising precipitation and temperature, infrastructure aging, and reservoir abandonment, implying the present flood decline unsustainable. Our research develops a strategy to investigate short-term flood anomalies under climate oscillations around the CTM, providing insights into flood research and prevention in global mountainous regions.

Mesozoic-Cenozoic Topographic Evolution of the South Tianshan (NW China): Insights from Detrital Apatite Geo-Thermochronological and Geochemical Analyses

Abstract The present-day topography of Tianshan is the product of repeated phases of Meso-Cenozoic intracontinental deformation and reactivation, whereas the long-term Mesozoic topographic evolution and the timing of the onset of Cenozoic deformation remain debated. New insights into the Meso-Cenozoic geodynamic evolution and related basin-range interactions in the Tianshan were obtained based on new detrital single-grain apatite U-Pb, fission-track, and trace-element provenance data from Mesozoic sedimentary sequences on the northern margin of the Tarim Basin. Detrital apatite U-Pb age data from Early-Middle Triassic clastic rocks show two prominent age populations at 500–390 Ma and 330–260 Ma, with a paucity of ages between 390 and 330 Ma, suggesting that sediment source is predominantly from the northern Tarim and South Tianshan. From the Late Triassic to Early Jurassic, the first appearance of populations in the 390–330 Ma and 260–220 age ranges indicates that the Central Tianshan-Yili Block and Western Kunlun Orogen were source regions for the northern margin of Tarim Basin. In the Cretaceous strata, south-directed paleocurrents combined with the decrease in the 390–330 Ma age population from the Central Tianshan-Yili Block imply that South Tianshan was uplifted and again became the main source region to the Baicheng-Kuqa depression during the Cretaceous. Our new apatite fission-track data from the southern Chinese Tianshan suggest that rapid cooling commenced at c. 30 Ma along the southern margin, and the Early Mesozoic strata exposed on the southern flank of the Tianshan underwent c. 4–5 km of late Cenozoic exhumation during this period. This age is approximately synchronous with the onset of exhumation/deformation not only in the whole Tianshan but also in the interior of the Tibetan Plateau and its margins. It suggests that far-field, N-directed shortening resulting from the India-Asia collision was transmitted to the Tianshan at that time.

Genetic link between orogenic Au and porphyry Cu ([sbnd]Au) mineralization in the Dananhu Arc, NW China: Evidence from geochronology, geochemistry, and Sr–Nd–Hf isotopes of the Tudunbei Au deposit

The late Paleozoic Chinese Tianshan is characterized by large volumes of arc-related magmatic rocks, and numerous associated orogenic Au and porphyry Cu (Au) deposits. The link between these two deposit styles, however, is ambiguous. Here, we present zircon U–Pb–Hf isotopes, bulk-rock geochemistry, and sericite 40Ar/39Ar geochronology from the newly discovered Tudunbei Au deposit located east of the Tuwu–Yandong porphyry Cu (Au) ore district in the Dananhu Arc, Chinese North Tianshan, and combine this with previously published geochronological and geochemical data to characterize the genetic relationship between orogenic Au and porphyry Cu (Au) mineralization. Our new UPb zircon ages indicate that the wall rocks of the Tudunbei Au deposit formed during the Carboniferous between 337 and 314 Ma (K-feldspar granite: 334.8 ± 1.9 Ma, basaltic tuff: 336.6 ± 4.0 Ma, quartz diorite: 316.0 ± 1.8 Ma, gabbroic diorite: 318.3 ± 1.8 Ma, and gabbro: 314.3 ± 1.8 Ma). These wall rocks are enriched in light rare earth elements and large ion lithophile elements (e.g., Ba, U, and Pb), and depleted in high field strength elements (e.g., Nb, Ta, and Ti). Given the absence of Precambrian basement rocks in the Chinese North Tianshan, and the depleted NdHf isotope compositions (εHf(t) = 12.12–14.98; εNd(t) = 5.77–7.06) of the wall rocks, their young Hf model ages (350–510 Ma), the lack of inherited zircons, and their enrichment in Na2O (2.84–4.73 wt%) relative to K2O (0.43–2.40 wt%), it is suggested that they formed in an oceanic arc environment. One sericite sample selected from an auriferous quartz vein yielded 40Ar/39Ar plateau ages of 260.6 ± 1.1 Ma, which is representative of the gold mineralization age. Given the abundance of gold in the Carboniferous wall rocks of the Tuwu–Yandong porphyry Cu (Au) ore district, the similarity in the timing of its magmatism with Tudunbei, and the geochemical–isotopic (Sr–Nd–Hf) similarity of their wall rocks, it is inferred that the gold in the Tudunbei deposit was remobilized from pre-existing gold in the Carboniferous wall rocks during regional metamorphism and deformation.

Change in the potential snowfall phenology: past, present, and future in the Chinese Tianshan mountainous region, Central Asia

Abstract. The acceleration of climate warming has led to a faster solid–liquid water cycle and a decrease in solid water storage in cold regions of the Earth. Although snowfall is the most critical input for the cryosphere, the phenology of snowfall, or potential snowfall phenology (PSP), has not been thoroughly studied, and there is a lack of indicators for PSP. For this reason, we have proposed three innovative indicators, namely, the start of potential snowfall season (SPSS), the end of potential snowfall season (EPSS), and the length of potential snowfall season (LPSS), to characterize the PSP. We then explored the spatial–temporal variation in all three PSP indicators in the past, present, and future across the Chinese Tianshan mountainous region (CTMR) based on the observed daily air temperature from 26 meteorological stations during 1961–2017/2020 combined with data from 14 models from CMIP6 (Phase 6 of the Coupled Model Intercomparison Project) under four different scenarios (SSP126, SSP245, SSP370, and SSP585, where SSP represents Shared Socioeconomic Pathway) during 2021–2100. The study showed that the SPSS, EPSS, and LPSS indicators could accurately describe the PSP characteristics across the study area. In the past and present, the potential snowfall season started on 2 November, ended on 18 March, and lasted for about 4.5 months across the CTMR on average. During 1961–2017/2020, the rate of advancing the EPSS (−1.6 d per decade) was faster than that of postponing the SPSS (1.2 d per decade). It was also found that there was a significant delay in the starting time (2–13 d) and advancement in the ending time (1–13 d), respectively, resulting in a reduction of 3–26 d for the LPSS. The potential snowfall season started earlier, ended later, and lasted longer in the north and center compared with the south. Similarly, the SPSS, EPSS, and LPSS indicators are also expected to vary under the four emission scenarios during 2021–2100. Under the highest emission scenario, SSP585, the starting time is expected to be postponed by up to 41 d, while the ending time is expected to be advanced by up to 23 d across the study area. This change is expected to reduce the length of the potential snowfall season by up to 61 d (about 2 months), and the length of the potential snowfall season will only last 2.5 months in the 2100s under the SSP585 scenario. The length of the potential snowfall season in the west and southwest of the CTMR will be compressed by more days due to a more delayed starting time and an advanced ending time under all four scenarios. This suggests that, with constant snowfall intensity, annual total snowfall may decrease, including the amount and frequency, leading to a reduction in snow cover or mass, which will ultimately contribute to more rapid warming through the lower reflectivity to solar radiation. This research provides new insights into capturing the potential snowfall phenology in the alpine region and can be easily extended to other snow-dominated areas worldwide. It can also help inform snowfall monitoring and early warning for solid water resources.

Timing and spatial variation of deformation along the Kanggur-Huangshan shear zone in the Chinese Tianshan: Implications for regional differential uplift and mineralization

The Chinese Tianshan experienced large-scale transcurrent tectonics, synkinematic emplacement of ultramafic to felsic intrusions, and the formation of various mineral deposits during late Paleozoic accretionary orogenesis. The relationships among the spatial variation of deformation, the distribution of Permian orogenic Au and magmatic Ni-Cu sulfide deposits, and the kinematic evolution of crustal-scale shear zones, however, remain ambiguous. To address these ambiguities, the spatial variation in the degree of deformation in the Kanggur-Huangshan shear zone in the Chinese Tianshan was characterized using detailed structural measurements and zircon U-Pb and muscovite 40Ar/39Ar age data. The new structural data indicate that a prominent spatial variation exists in the style of deformation throughout the Kanggur-Huangshan shear zone; intense ductile deformation structures are dominant in the east, while brittle structures become progressively more dominant toward to the west. Zircon U-Pb and muscovite 40Ar/39Ar age data for syn- and postkinematic intrusions along the Kanggur-Huangshan shear zone indicate that dextral strike-slip shearing occurred between 279 Ma and 249 Ma. The spatial variation in the degree of deformation and exhumation along the Kanggur-Huangshan shear zone was potentially caused by regional differential uplift induced by the collision of the Tianshan and Beishan regions; this was likely responsible for the predominant occurrence of magmatic Ni-Cu sulfide deposits in the eastern portion of the Kanggur-Huangshan shear zone and orogenic Au deposits in the western portion. The identified spatio-temporal relationship between deformation and distribution of orogenic Au and magmatic Ni-Cu sulfide deposits is crucial to the future success of mineral exploration in the Central Asian orogenic belt.

A re-evaluation of the Meso-Cenozoic thermo-tectonic evolution of Bogda Shan (Tian Shan, NW China) based on new basement and detrital apatite fission track thermochronology

ABSTRACT Bogda Shan is a mountain belt located at the eastern extremity of the Chinese Tianshan and records a complex and debated exhumation history. Previous studies have reported a young Cenozoic thermal history for the exhumation of Bogda Shan, which is in conflict with the observation of preserved Mesozoic erosion surfaces in the area. This study re-evaluates the Meso-Cenozoic thermo-tectonic evolution of Bogda Shan using apatite fission track (AFT) thermochronology. Palaeozoic basement (meta-sandstone) samples collected from the northern and southwestern flanks of the mountain ranges reveal apparent Mesozoic AFT ages ranging from ~202 Ma to ~97 Ma. Inverse thermal history modelling results reveal slow to moderate basement cooling during the early Mesozoic, corresponding to relatively low levels of exhumation. This accounts for the preservation of low-relief Mesozoic peneplanation surfaces recognized at elevations of ~3500–4000 m. None of the presented AFT data and thermal history models show any evidence for significant deep Cenozoic exhumation. In the neighbouring Junggar Basin, a Middle Jurassic sandstone sample records partial resetting of the AFT system during the Cretaceous. This observation conflicts with previous data (from the same Jurassic strata) where complete resetting of the AFT clock during the Cenozoic was suggested. Furthermore, Lower Cretaceous and Palaeogene sediments from the Turpan-Hami Basin show non-reset detrital AFT age populations of ~197, ~135, and ~104 Ma, which are coincident with the main pulses of exhumation recorded in the Chinese North Tianshan. Based on a comprehensive summary of the published data, we argue for a Mesozoic building of the Bogda–Balikun–Harlik mountain chain in the eastern Chinese Tianshan. Subsequent Cenozoic exhumation must have been relatively modest at most (<2 km) as it was not recorded by AFT thermochronology.

Effect of topography on the changes of Urumqi Glacier No. 1 in the Chinese Tianshan Mountains

Topography plays an important role in determining the glacier changes. However, topography has often been oversimplified in the studies of the glacier changes. No systematic studies have been conducted to evaluate the relationship between the glacier changes and topographic features. The present study provided a detailed insight into the changes in the two branches (east branch and west branch) of Urumqi Glacier No. 1 in the Chinese Tianshan Mountains since 1993 and systematically discussed the effect of topography on the glacier parameters. This study analyzed comprehensive recently observed data (from 1992/1993 to 2018/2019), including mass balance, ice thickness, surface elevation, ice velocity, terminus, and area, and then determined the differences in the changes of the two branches and explored the effect of topography on the glacier changes. We also applied a topographic solar radiation model to analyze the influence of topography on the incoming shortwave radiation (SWin) across the entire glacier, focusing on the difference in the SWin between the two branches. The glacier mass balance of the east branch was more negative than that of the west branch from 1992/1993 to 2018/2019, and this was mainly attributed to the lower average altitude of the east branch. Compared with the west branch, the decrease rate of the ice velocity was lower in the east branch owing to its relatively increased slope. The narrow shape of the west branch and its southeast aspect in the earlier period resulted in a larger glacier terminus retreat of the west branch. The spatial variability of the SWin across the glacier surface became much larger as altitude increased. The SWin received by the east branch was slightly larger than that received by the west branch, and the northern aspect could receive more SWin, leading to glacier melting. In the future, the difference of the glacier changes between the two branches will continue to exist due to their topographic differences. This work is fundamental to understanding how topographic features affect the glacier changes, and provides information for building different types of relationship between the glacier area and ice volume to promote further studies on the basin-scale glacier classification.

Alpine vegetation responses to snow phenology in the Chinese Tianshan mountainous region

Alpine vegetation responses to snow phenology in the Chinese Tianshan mountainous region

Late Mesozoic intracontinental deformation and magmatism in the Chinese Tianshan and adjacent areas, Central Asia

Abstract The Tianshan Range–Junggar Basin– Kalamaili Range system represents the southwestern Central Asian Orogenic Belt and is a natural laboratory for studying intracontinental deformation processes. Its current topography is a product of the farfield effects of the Cenozoic India-Asia collision. However, the Mesozoic topographic and tectonic evolution of the Tianshan and Kalamaili Ranges and their impacts on the Junggar Basin remain enigmatic due to the scarcity of data. Here, we present a comprehensive synthesis of sedimentological and geochronological data on these ranges and adjacent basins to reconstruct the intracontinental evolution from the Early Jurassic to the Early Cretaceous. Based on field observations and seismic profile analysis, we identified several unconformities within the late Mesozoic strata in the Tianshan Range and the Junggar Basin. Detrital zircon U-Pb dating results for Lower Jurassic to Lower Cretaceous sandstones of the eastern and southern Junggar Basin, with published paleocurrent data, reveal a complex intracontinental topographic evolution. Moreover, tuffaceous gravels and tuff samples yielded weighted mean zircon 206Pb/238U ages of 156.5 ± 3.2 Ma and 156.3 ± 2.2 Ma, respectively, which indicates the presence of contemporary magmatic activity. The deformation and magmatism mentioned above were possibly related to multi-plate convergence in East Asia during the late Mesozoic. This study provides new insights into the late Mesozoic tectonic-magmatic evolution of the Tianshan Range and its adjacent areas.

Projected change in precipitation forms in the Chinese Tianshan Mountains based on the Back Propagation Neural Network Model

Projected change in precipitation forms in the Chinese Tianshan Mountains based on the Back Propagation Neural Network Model

Spatio-Temporal Heterogeneity of Climate Warming in the Chinese Tianshan Mountainous Region

The Chinese Tianshan mountainous region (CTMR) is a typical alpine region with high topographic heterogeneity, characterized by a large altitude span, complex topography, and diverse landscapes. A significant increase in air temperature had occurred in the CTMR during the last five decades. However, the detailed, comprehensive, and systematical characteristics of climate warming, such as its temporal and spatial heterogeneity, remain unclear. In this study, the temporal and spatial heterogeneity of climate warming across the CTMR had been comprehensively analyzed based on the 10-day air temperature data gathered during 1961–2020 from 26 meteorological stations. The results revealed local cooling in the context of general warming in the CTMR. The amplitude of variation (AV) varied from −0.57 to 3.64 °C, with the average value of 1.19 °C during the last six decades. The lapse rates of the elevation-dependent warming that existed annually, and in spring, summer, and autumn are −0.5 °C/100 m, −0.5 °C/100 m, −0.7 °C/100 m, and −0.4 °C/100 m, respectively. The warming in the CTMR is characteristic of high temporal heterogeneity, as represented by the amplified warming at 10-d scale for more than half a year, and the values of AV were higher than 1.09 °C of the global warming during 2011–2020 (GWV2011–2020). Meanwhile, the amplitudes of warming differed greatly on a seasonal scale, with the rates in spring, autumn, and winter higher than that in summer. The large spatial heterogeneity of climate warming also occurred across the CTMR. The warming pole existed in the warm part, the Turpan-Hami basin (below 1000 m asl) where the air temperature itself was high. That is, the warm places were warmer across the CTMR. The cooling pole was also found in the Kuqa region (about 1000 m asl). This study could greatly improve the understanding of the spatio-temporal dynamics, patterns, and regional heterogeneity of climate warming across the CTMR and even northwest China.

Long-term topographic evolution of the Central Tianshan (NW China) constrained by low-temperature thermochronology

The Tianshan belt forms the southwestern part of the Central Asian Orogenic Belt, and its current topography is a product of punctuated Meso-Cenozoic intra-continental deformation that is still active today. This study provides new apatite fission track data on the Paleozoic rocks in and adjacent to the Chinese Central Tianshan, including two age-elevation profiles in the Alagou and Gangou areas. Inverse thermal history modelling reveals that the Central Tianshan experienced regional slow to moderate cooling during most of the Mesozoic, and that the present-day topography was mainly built by Cenozoic uplift and erosion. Geomorphological observation reveals several fragments of flat, low-relief surfaces within the Central Tianshan, which were likely to have formed in the Mesozoic as evidenced by thermal history modelling of the Alagou age-elevation profile. Furthermore, our data suggest that the Chinese Central Tianshan and its adjacent terranes did not undergo intensive relief building during its long-term Mesozoic evolution, as several pre-Mesozoic deep-rooted regional faults did not record evidence for a strong Mesozoic reactivation. Finally, differential exhumation in the Western Chinese Tianshan and Junggar is discussed, and we propose that the development of regional brittle faults could significantly influence the processes of intra-continental deformation.