Geochemical Characteristics of the Plagiogranites in the Vicinity of Bingdaban,Central Tianshan.

The tectonic and geochemical characteristics suggest that the plagiogranitesexposed in the vicinity of Bingdaban on the northern margin of the central Tianshanuplift zone show a distinct mantle-source character, and their enrichment in LREE andselected enrichment in LILE (large ion lithophile elements) reflect a setting related to anarc tectonic regime. These rocks represent the products formed at shallow levels frommantle-derived magmas modified with subduction components (or super crustal rocks).

Late Triassic Intracontinental Deformation of South Tianshan,Central Asia:Evidence from Syn-tectonic Sedimentation and Detrital Zircon Provenances of the Kuqa Depression

The Tianshan range,a Paleozoic orogenic belt in Central Asia,has undergone multiple phases of tectonic activities characterized by the N-S compression after the early Mesozoic,including the far-field effects of the Cenozoic Indian-Asian collision.However,there are limited reports on the tectonic deformation and initiation of Triassic intracontinental deformation in the Tianshan range.Understanding this structural context is crucial for interpreting the early intracontinental deformation history of the Eurasian continent during the early Mesozoic.Growth strata and syn-tectonic sediments provide a rich source of information on tectonic activities and have been extensively used in the studies of orogenic belts.Based on detail fieldwork conducted in this study,the middle-late Triassic Kelamayi Formation of the northern Kuqa Depression in the southern Tianshan fold-thrust belt has been identified as the typical syn-tectonic growth strata.The youngest detrital zircon component in two lithic sandstone samples from the bottom and top of the Kelamayi growth strata yielded U-Pb ages of 223.4±3.1 and 215.5±2.9 Ma,respectively,indicating that the maximum depositional age of the bottom and top of the Kelamayi growth strata is 226-220 and 218-212 Ma.The geochronological distribution of detrital samples from the Early-Middle Triassic and Late Triassic revealed abrupt changes,suggesting a new source supply resulting from tectonic activation in the Tianshan range.The coupling relationship between the syn-tectonic sedimentation of the Kelamayi Formation and the South Tianshan fold-thrust system provides robust evidence that the Triassic intracontinental deformation of the South Tianshan range began at approximately 226-220 Ma(during the Late Triassic)and ended at approximately 218-212 Ma.These findings provide crucial constraints for understanding the intraplate deformation in the Tianshan range during the Triassic.

Geochronology and Geochemistry of the Xingxingxia Triassic A-type Granites in Central Tianshan,NW China:Petrogenesis and Tectonic Implications

The Triassic granitoids in Central Tianshan play a key role in determining the petrogenesis and tectonic evolution on the southern margin of the Central Asian orogenic belt.In this study,we present SHRIMP zircon U-Pb ages,Hf isotopic and geochemical data on the Xingxingxia biotite granite,amazonite granite and granitic pegmatite in Central Tianshan,NW China.Zircon U-Pb dating yielded formation ages of 242 Ma for the biotite granite and 240 Ma for the amazonite granite.These granitoid rocks have high K_(2)O with low MgO and CaO contents.They are enriched in Nb,Ta,Hf and Y,while being depleted in Ba and Sr,showing flat HREE patterns and negative Eu anomalies.They have typical A-type granite geochemical signatures with high Ga/A_(1)(8–13)and TFeO/(TFeO+MgO)ratios,showing an A_(2) affinity for biotite granite and an A_(1) affinity for amazonite granite and granitic pegmatite.Zircon ε_(Hf)(t)values of the granitoids are 0.45–2.66,with Hf model ages of 0.99–1.17 Ga.This suggests that these A-type granites originated from partial melting of the lower crust.We propose that Xingxingxia Triassic A-type granites formed under lithospheric extension from post-orogenic to anorogenic intraplate settings and NE-trending regional strike-slip fault-controlled magma emplacement in the upper crust.

Climate warming is significantly influenced by rising summer maximum temperatures: insights from tree-ring evidence of the Western Tianshan Mountains, China

As one of the regions most affected by global cli-mate warming,the Tianshan mountains has experienced sev-eral ecological crises,including retreating glaciers and water deficits.Climate warming in these mountains is considered mainly to be caused by increases in minimum temperatures and winter temperatures,while the influence of maximum temperatures is unclear.In this study,a 300-year tree-ring chronology developed from the Western Tianshan Moun-tains was used to reconstruct the summer(June-August)maximum temperature(T_(max6-8))variations from 1718 to 2017.The reconstruction explained 53.1% of the variance in the observed T_(max6-8).Over the past 300 years,the T_(max6-8)reconstruction showed clear interannual and decadal vari-abilities.There was a significant warming trend(0.18°C/decade)after the 1950s,which was close to the increasing rates of the minimum and mean temperatures.The increase in maximum temperature was also present over the whole Tianshan mountains and its impact on climate warming has increased.The T_(max6-8) variations in the Western Tianshan mountains were influenced by frequent volcanic eruptions combined with the influence of solar activity and the sum-mer North Atlantic Oscillation.This study reveals that cli-mate warming is significantly influenced by the increase in maximum temperatures and clarifies possible driving mech-anisms of temperature variations in the Western Tianshan mountains which should aid climate predictions.

Climate warming is significantly influenced by rising summer maximum temperatures:insights from tree-ring evidence of the Western Tianshan Mountains,China

As one of the regions most affected by global climate warming,the Tianshan mountains has experienced several ecological crises,including retreating glaciers and water deficits.Climate warming in these mountains is considered mainly to be caused by increases in minimum temperatures and winter temperatures,while the influence of maximum temperatures is unclear.In this study,a 300-year tree-ring chronology developed from the Western Tianshan Mountains was used to reconstruct the summer(June-August)maximum temperature(Tmax6-8) variations from 1718 to2017.The reconstruction explained 53.1% of the variance in the observed Tmax6-8.Over the past 300 years,the Tmax6-8reconstruction showed clear interannual and decadal variabilities.There was a significant warming trend(0.18 ℃/decade) after the 1950s,which was close to the increasing rates of the minimum and mean temperatures.The increase in maximum temperature was also present over the whole Tianshan mountains and its impact on climate warming has increased.The Tmax6-8variations in the Western Tianshan mountains were influenced by frequent volcanic eruptions combined with the influence of solar activity and the summer North Atlantic Oscillation.This study reveals that climate warming is significantly influenced by the increase in maximum temperatures and clarifies possible driving mechanisms of temperature variations in the Western Tianshan mountains which should aid climate predictions.

Zircon U-Pb ages in the Nuratau ophiolitic mélange in the southern Tianshan,Uzbekistan:Implication for the closure of Paleo-Asian Ocean

1.Objective The Central Asian Orogenic Belt(CAOB),which is located between the European craton,Siberian craton,and Tarim-North China craton(Fig.1a),is the largest phanerozoic accretionary orogen in the world.It resulted from the longterm subduction and accretion of the Paleo-Asian Ocean(PAO).The PAO has been in existence since at least the late Mesoproterozoic(about 1020 Ma).However,there has been debate about the closing time of the PAO.

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

Climate warming profoundly affects hydrological changes,agricultural production,and human society.Arid and semi-arid areas of China are currently displaying a marked trend of warming and wetting.The Chinese Tianshan Mountains(CTM)have a high climate sensitivity,rendering the region particularly vulnerable to the effects of climate warming.In this study,we used monthly average temperature and monthly precipitation data from the CN05.1 gridded dataset(1961-2014)and 24 global climate models(GCMs)of the Coupled Model Intercomparison Project Phase 6(CMIP6)to assess the applicability of the CMIP6 GCMs in the CTM at the regional scale.Based on this,we conducted a systematic review of the interannual trends,dry-wet transitions(based on the standardized precipitation index(SPI)),and spatial distribution patterns of climate change in the CTM during 1961-2014.We further projected future temperature and precipitation changes over three terms(near-term(2021-2040),mid-term(2041-2060),and long-term(2081-2100))relative to the historical period(1961-2014)under four shared socio-economic pathway(SSP)scenarios(i.e.,SSP1-2.6,SSP2-4.5,SSP3-7.0,and SSP5-8.5).It was found that the CTM had experienced significant warming and wetting from 1961 to 2014,and will also experience warming in the future(2021-2100).Substantial warming in 1997 was captured by both the CN05.1 derived from interpolating meteorological station data and the multi-model ensemble(MME)from the CMIP6 GCMs.The MME simulation results indicated an apparent wetting in 2008,which occurred later than the wetting observed from the CN05.1 in 1989.The GCMs generally underestimated spring temperature and overestimated both winter temperature and spring precipitation in the CTM.Warming and wetting are more rapid in the northern part of the CTM.By the end of the 21st century,all the four SSP scenarios project warmer and wetter conditions in the CTM with multiple dry-wet transitions.However,the rise in precipitation fails to counterbalance the drought induced by escalating temperature in the future,so the nature of the drought in the CTM will not change at all.Additionally,the projected summer precipitation shows negative correlation with the radiative forcing.This study holds practical implications for the awareness of climate change and subsequent research in the CTM.

Spatial and temporal patterns of the sensitivity of radial growth response by Picea schrenkiana to regional climate change in the Tianshan Mountains

Climate change significantly impacts forest ecosystems in arid and semi-arid regions.However,spatiotemporal patterns of climate-sensitive changes in individual tree growth under increased climate warming and precipitation in north-west China is unclear.The dendrochronological method was used to study climate response sensitivity of radial growth of Picea schrenkiana from 158 trees at six sites during 1990-2020.The results show that climate warming and increased precipitation significantly promoted the growth of trees.The response to temperature first increased,then decreased.However,the response to increased precipitation and the self-calibrating Palmer Drought Severity Index(scPDSI)increased significantly.In most areas of the Tianshan Mountains,the proportion of trees under increased precipitation and scPDSI positive response was relatively high.Over time,small-diameter trees were strongly affected by drought stress.It is predicted that under continuous warming and increased precipitation,trees in most areas of the Tianshan Mountains,especially those with small diameters,will be more affected by precipitation.

Modern pollen assemblages and their relationships with vegetation and climate on the northern slopes of the Tianshan Mountains, Xinjiang, China

The reconstruction of paleovegetation and paleoclimate requires an understanding of the relationships between surface pollen assemblages and modern vegetation and climate.Here,we analyzed the characteristics of surface pollen assemblages across different vegetation zones in the Tianshan Mountains.Using surface pollen analysis and vegetation sample surveys at 75 sites on the northern slopes of the Tianshan Mountains,we determined the correlation between the percentage of dominant pollen types and the corresponding vegetation cover.Redundancy analysis was used to investigate the relationships between surface pollen assemblages and environmental factors.Our results show that the Tianshan Mountains contain several distinct ecological regions,which can be divided into five main vegetation zones from low to high altitudes:mountain desert zone(Hutubi County(HTB):500-1300 m;Qitai County(QT):1000-1600 m),mountain steppe zone(HTB:1400-1600 m;QT:1650-1800 m),mountain forest zone(HTB:1650-2525 m;QT:1850-2450 m),subalpine meadow zone(HTB:2550-2600 m;QT:2500-2600 m),and alpine mat vegetation zone(HTB:2625-2700 m;QT:2625-2750 m).The surface pollen assemblages of different vegetation zones can accurately reflect the characteristics of the mountainous vegetation patterns on the northern slopes of the Tianshan Mountains when excluding the widespread occurrence of Chenopodiaceae,Artemisia,and Picea pollen.Both average annual precipitation(P_(ann))and annual average temperature(T_(ann))affect the distribution of surface pollen assemblages.Moreover,P_(ann) is the primary environmental factor affecting surface pollen assemblages in this region.A significant correlation exists between the pollen percentage and vegetation cover of Picea,Chenopodiaceae,Artemisia,and Asteraceae.Moreover,Picea,Chenopodiaceae,and Artemisia pollen are over-represented compared with their corresponding vegetation cover.The Asteraceae pollen percentage roughly reflects the distribution of a species within the local vegetation.These results have important implications for enhancing our understanding of the relationship between surface pollen assemblages and modern vegetation and climate.

Geochronology and Geochemistry of the Early Paleozoic Ore-host Volcanic Sequence in the Kalatag Area,East Tianshan,NW China:Implications for the Tectonic Evolution

The East Tianshan contains many late Paleozoic magmatic and polymetallic deposits.Recent studies demonstrate that the early Paleozoic volcanic rocks discovered in the northern region of East Tianshan can be subdivided into the Daliugou,Hongliuxia and Kalatag formations.Here,we report zircon U-Pb ages of volcanic rocks and quartz diorite porphyry,together with whole-rock geochemical and Sr-Nd isotope data of early Paleozoic volcanic rocks,in order to investigate their petrogenesis and geodynamic setting.Zircon U-Pb analyses of the rocks suggest that the Kalatag Formation formed at ca.438-413 Ma.Geochemical characteristics of the early Paleozoic volcanic rocks exhibit typical subduction-related features.They have high Mg^(#)(44-75),positiveε_(Nd)(t)values(0.25-7.88),low^(87)Sr/^(86)Sr ratios(0.70457 to 0.70588)and young two-stage Hf isotope model ages(551-446 Ma),consistent with a depleted mantle origin with limited crustal contamination.The basaltic andesite and andesite have relatively high MgO contents(6.1-9.4 wt%),suggesting that they belong to high-magnesian andesites.They were most likely derived from the partial melting of mantle peridotite caused by the addition of fluids released by subducted oceanic slab.Based on regional geology,geochemical characteristics and previous studies,we infer that the southward subduction of the Junggar Ocean slab resulted in the generation of early Paleozoic volcanic rocks and arc setting-related metallogenic systems in the Kalatag area.

Precipitation scale effect of the TRMM satellite in Tianshan,China

High-resolution precipitation data is conducive to objectively describe the spatial-temporal variability of regional precipitation,and the study of downscaling techniques and spatial scale effects can provide technical and theoretical support to improve the spatial resolution and accuracy of satellite precipitation data.In this study,we used a machine learning algorithm combined with a regression algorithm RF-PLS(Random Forest-Partial Least Squares)to construct a downscaling model to obtain three types of high-resolution TRMM(Tropical Rainfall Measuring Mission)downscaled precipitation data for the years 2000-2017 at 250 m,500 m,and 1km.The scale effects with topographic and geomorphological features in the study area were analysed.Finally,we described the spatial and temporal variation of precipitation based on the optimal TRMM downscaled precipitation data.The results showed that:1)The linear relationships between the TRMM downscaled precipitation data obtained by each of the three downscaled models(PLS,RF,and RF-PLS)and the precipitation at the observation stations were improved compared to the linear relationships between the original TRMM data and the precipitation at the observation stations.The accuracy of the RF-PLS model was better than the other two models.2)Based on the RF-PLS model,the resolution of the TRMM data was increased to three different scales(250 m,500 m,and 1 km),considering the scale effects with topographic and geomorphological features.The precipitation simulation effect with a spatial resolution of 500 m was better than the other two scales.3)The annual precipitation was the highest in the areas with extremely high mountains,followed by the mediumhigh mountain,high mountain,medium mountain,medium-low mountain,plain,low mountain,and basin.

Report of 2.7 Ga zircon U-Pb age of orthogneiss in the Wenquan metamorphic complex,West Tianshan,China

1.Objective The Wenquan Group is one of the important medium-to low-grade metamorphic units within the Wenquan metamorphic complexes which distributes in Chinese segment of the Tianshan Belt,the southern part of the Central Asian Orogenic Belt.It mainly consists of pre-Neoproterozoic metamorphosed volcanic and sedimentary rocks(Wang B et al.,2014).

Temporal and spatial responses of ecological resilience to climate change and human activities in the economic belt on the northern slope of the Tianshan Mountains, China

In the Anthropocene era,human activities have become increasingly complex and diversified.The natural ecosystems need higher ecological resilience to ensure regional sustainable development due to rapid urbanization and industrialization as well as other intensified human activities,especially in arid and semi-arid areas.In the study,we chose the economic belt on the northern slope of the Tianshan Mountains(EBNSTM)in Xinjiang Uygur Autonomous Region of China as a case study.By collecting geographic data and statistical data from 2010 and 2020,we constructed an ecological resilience assessment model based on the ecosystem habitat quality(EHQ),ecosystem landscape stability(ELS),and ecosystem service value(ESV).Further,we analyzed the temporal and spatial variation characteristics of ecological resilience in the EBNSTM from 2010 to 2020 by spatial autocorrelation analysis,and explored its responses to climate change and human activities using the geographically weighted regression(GWR)model.The results showed that the ecological resilience of the EBNSTM was at a low level and increased from 0.2732 to 0.2773 during 2010–2020.The spatial autocorrelation analysis of ecological resilience exhibited a spatial heterogeneity characteristic of"high in the western region and low in the eastern region",and the spatial clustering trend was enhanced during the study period.Desert,Gobi and rapidly urbanized areas showed low level of ecological resilience,and oasis and mountain areas exhibited high level of ecological resilience.Climate factors had an important impact on ecological resilience.Specifically,average annual temperature and annual precipitation were the key climate factors that improved ecological resilience,while average annual evapotranspiration was the main factor that blocked ecological resilience.Among the human activity factors,the distance from the main road showed a negative correlation with ecological resilience.Both night light index and PM2.5 concentration were negatively correlated with ecological resilience in the areas with better ecological conditions,whereas in the areas with poorer ecological conditions,the correlations were positive.The research findings could provide a scientific reference for protecting the ecological environment and promoting the harmony and stability of the human-land relationship in arid and semi-arid areas.

Petrogenesis of the Carboniferous Intrusive Rock in the Xiaobaishitou District of East Tianshan,Northwest China:Magma Evolution and Tectonic Significance

The Xiaobaishitou gabbro-diorite pluton comprises a medium-grained gabbro-diorite suite and a fine-grained diorite suite,which intrude the Kawabulag Group in the East Tianshan Orogen of the Central Asian Orogenic Belt(CAOB).A combination of mineral chemistry,zircon U-Pb age,whole-rock geochemistry,Sr-Nd isotopes,and in situ zircon Hf isotopes for newly found gabbro-diorite from the Xiaobaishitou district in the Central Tianshan Terrane(CTT)is presented to investigate the petrogenesis and tectonic or even crustal evolution of the East Tianshan Orogen.Laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS)zircon U-Pb analyses indicate that the gabbro-diorite was formed at 324.7±2.4 Ma.The isolated clinopyroxene formed under higher P-T-fO_(2)melt conditions(10.7–14.6 kbar;1199–1269℃;high fO_(2))than those for the hornblende,plagioclase,and zircon(557–687℃;moderate fO_(2))in the gabbro-diorite,which reveals a multilevel,magmatic storage system.The gabbro-diorite is characterized by fractioned REE patterns,enriched LILEs(e.g.,Ba and Pb),negative anomalies of HFSEs(e.g.,Nb and Ta),and low La/Yb and Sr/Y ratios,which are typically indicative of crustal contamination and accounted for by subduction-related fluids.The rock also characterized by typical features of high compatible elements(MgO=3.14–11.65 wt%,Cr=1–157 ppm,Ni=6–830 ppm),high Mg^(#)(47–74),positiveε_(Hf)(t)values(+5.1 to+10.3)andε_(Nd)(t)values(+2.3 to+4.4).These features suggest that the Xiaobaishitou gabbro-diorite was most likely derived from metasomatic mantle and contaminated minor crustal components.Taking into account the spatial and temporal distribution of the Carboniferous magmatic rocks in the CTT,we suggest the formation of the Xiaobaishitou gabbro-diorite was attributed to southward subduction of the Kangguer Ocean.

Hydroclimatic variations in the Tianshan Mountains based on grain size and geochemistry of core sediments since~1490 CE

Numerous studies have focused on modern hydroclimate and the modulated mechanisms in the Tianshan Mountains(TMs),arid central Asia.However,the detailed information of hydroclimatic processes beyond the instrumental period is still scarce.This paper reconstructed a hydrology history from core sediments of the Dalongchi Lake in the Tianshan Mountains.The comparability between endmembers(EMs)of grain size and ICP-AES based geochemical elements in the lake sediments highlighted their availability for hydrological reconstructions.Hydrodynamic forces(EM1,EM4,Ti/Al and Li/Al),chemical weathering intensity[(Mg+Ca+K)/Al],salinity proxy(Mg/Ca)and redoxsensitive proxy(Fe/Mn)highly correlated with the first principal component(P<0.01),whereas paleoproductivity proxies(TN,TOC,Ba/Al,Zn/Al and Cu/Al)and C/N showed high loadings on the second principal component(P<0.05).The inferred hydrology progress was nonlinearly responded to temperature,precipitation and climate-dictated glaciers.Specifically,the water level didn’t always covary with the humidity because of glaciers.The maximum water level was the comprehensive result of glaciers melting and high humidity around 1830 CE.Thereafter,water level continually decreased with declining moisture at high temperature,implying a limited buffering capacity of glaciers in the Dalongchi Lake basin.EM3-indicated eolian activity intensity was caused by the behaviors of Siberian High because the latter intensified surface wind and the dust transportation.The hydrothermal patterns were characterized by warm/dry and cold/wet alternations in a long run although warm/wet pattern was identified from a short-term view.

Magma source and tectonic setting of the Dunde granite in the Western Tianshan:constraints from geochronology,geochemistry,and Sr–Nd–Hf isotopes

The Dunde iron-zinc polymetallic deposit is one of large iron deposits occurred in the Awulale Metallogenetic Belt,Western Tianshan(NW-China).This study reports new geochronology and geochemistry for granite in the Dunde mining area in order to constrain the tectonicmagmatic activities and metallogenesis of this region.Granites in the southwest of Dunde mining area are mainly syenogranites intruded into volcanics of the Dahalajunshan Formation in the Early Carboniferous,and they are far from the area where ore bodies and mineralized altered rocks are widely developed.LA-ICP-MS U–Pb zircon dating indicates that Dunde syenogranite was at 306.8±1.0 Ma,which could constrain the upper limit of metallogenic age for this deposit.The Dunde granites are high SiO_(2)(73.41–80.07 wt%),high differentiation index(D.I.=89.7–95.0),weakly peraluminous to metaluminous(A/CNK=0.94–1.08),and they are enriched in LILE and LREE and depleted in Eu,Ba,Sr and P_(2)O_(5),indicating that they belong to highly fractionated Ⅰ-type granite.Based on εHf values(+9.2 to+10.5)for zircon and high εNd(-t)values(+4.7 to+5.8)for whole-rock,and the two-stage model ages for 601–735 Ma,suggest that the magma source could be the juvenile lower crust.Combined with regional geological setting,the 306.8 Ma Dunde granites are formed in post-collision extensional tectonic setting.

Redetermination of the Depositional Age of the Haerdaban Group in the Northern Margin of the Yili Block,Western Tianshan,NW China:Implications for Regional Tectonics and Pb-Zn Mineralization

The Yili Block in the Western Tianshan orogen is a key area for understanding the early crustal formation and evolution of the Central Asian orogenic belt,due to the widely-distributed Precambrian rocks.Also,it hosts a lot of medium–to large-scale sedimentary exhalative(SEDEX)Pb-Zn deposits that mainly occur in Proterozoic metamorphosed clasticcarbonate rocks.In this study,LA-ICP-MS U-Pb analyses were carried out on detrital zircons in siltstones of the Precambrian Haerdaban Group in the Haerdaban Pb-Zn deposit and magmatic zircons in the diorite dyke that cuts through the strata and orebodies.The maximum depositional age of the siltstones was determined to be about 604 Ma,the diorite having formed at approximately 500 Ma.As such,the Haerdaban Group was most likely formed in the Neoproterozoic Sinian,rather than the previously considered Mesoproterozoic Changchengian.Detrital materials of the Haerdaban Group were mostly derived from the Nanhua–Sinian mafic dykes and granitic rocks around Lake Sayram at the northern margin of the Yili Block.It is proposed that the Yili Block,together with the Kazakhstan and Central Tianshan blocks and the Tarim Craton,might all pertain to the same Rodinia supercontinent,which has great potential for targeting large to super-large SEDEX Pb-Zn deposits.

Abiotic Methane Reservoirs in the Western Tianshan HP–UHP Metamorphic Belt,China

Natural gas,consisting primarily of methane(CH_(4)),has become a major source of clean energy in modern society in many parts of the globe.Recent experimental observations and discoveries of deep-sourced abiotic CH_(4)in cold subduction zones indicate the important ability of cold subducted slabs to generate natural gas reservoirs.However,most CH_(4)flux and reservoirs remain unknown and their potential is overlooked in global carbon flux estimations.Massive abiotic CH_(4)-rich fluid inclusions(FIs)in garnet and omphacite from ultrahigh-pressure(UHP)eclogites have been found in the Western Tianshan(WT)UHP metamorphic belt,which provides one ideal case for quantification of abiotic CH_(4)stored in the cold subducted crust.By two methods,we assess the abiotic CH_(4)content stored in the Chinese WT HP–UHP metamorphic belt.Our calculations show that at least 113 Mt CH_(4)is stored in the WT eclogites.We also discuss the implications for CH_(4)reservoirs in subduction zones worldwide and speculate that the cold subduction zones may represent one of the largest,yet overlooked,sources of abiotic CH_(4)on Earth,which should not be ignored in the global natural resource and carbon flux estimations.

Evolution of economic linkage network of the cities and counties on the northern slope of the Tianshan Mountains,China

The exchanges between cities and counties in the northern slope economic belt of Tianshan Mountains(NSEBTM)are increasingly frequent and the economic linkages are increasingly close,but the spatial distribution of economic development and linkages among the cities and counties within NSEBTM is uneven.Therefore,it is of great significance to study the evolution of spatial-temporal pattern of the economic linkage network of cities and counties on NSEBTM to promote the coordinated and integrated development of the regional economy on NSEBTM.In this study,we used the modified gravity model and social network analysis method to analyze the spatio-temporal evolution characteristics of the economic linkage network structure of cities and counties on NSEBTM in 2000,2010,and 2020.The results showed that the comprehensive development quality level of cities and counties on NSEBTM increased from 2000 to 2020,its growth rate also increased,and its gap between cities and counties continued expanding.Both the spatial distribution patterns of the comprehensive development quality level of cities and counties on NSEBTM in 2000 and 2010 were presented as“high in the middle and low at both ends”,while the spatial distribution pattern of 2020 was exhibited as“high value and low value staggered”.The total amount of external economic linkages of cities and counties on NSEBTM showed an obvious upward trend,and its gap between cities and counties continued expanding,presenting a pattern of“a strong middle section and weak ends”.The direction of economic linkages of NSEBTM existed obvious central orientation and geographical proximity.The density of economic linkage network of NSEBTM increased from 2000 to 2020,and the structure of economic linkage network changed from single-core structure centered with Urumqi City to multicore structure centered with Urumqi City,Karamay City,Shihezi City,and Changji City,shifting from unbalanced development to balanced development.In the future,we should accelerate the construction of urban agglomeration on NSEBTM,cultivate a modern Urumqi metropolitan area,improve comprehensive development quality of the cities and counties at the eastern and western ends,strengthen the intensity of economic linkages between cities and counties,optimize the economic linkage network,and promote the coordinated and integrated development of regional economy.

西天山乌孙山花岗岩和闪长岩年代学、地球化学及岩石成因

笔者选取位于伊犁盆地内乌孙山北缘察布查尔林场花岗岩为研究对象,其地球化学、地质年代学和岩石成因研究对于探讨西天山南缘壳幔岩浆作用具有较重要的指示意义。岩石地球化学特征显示二长花岗岩属高钾钙碱性准铝质-弱过铝质岩石系列;轻稀土富集,弱的Eu负异常(δEu=0.74~0.84),富集大离子亲石元素,亏损Nb、Ta、P、Ti等高场强元素特征,Zr/Hf=42~44,部分样品中含有少量的刚玉标准矿物,显示出壳源花岗岩的特征。闪长岩Al_(2)O_(3)、FeOT、CaO含量明显高于二长花岗岩,Na_(2)O和K_(2)O含量低于二长花岗岩,属于高钾准铝质岩石系列;轻稀土富集,显示出Eu的轻微正异常(δEu=0.90~1.24),富集大离子亲石元素,亏损Nb、Ta等高场强元素,此外,闪长岩还显示出具有高Sr(Sr>400×10^(-6))低Y(12.83×10^(-6))及Yb(1.34×10^(-6))和高Mg^(#)特征,其源岩应为俯冲板片上覆地幔部分熔融产物。二者均显示出岛弧岩浆的特征。二长花岗岩锆石U-Pb年龄为(361.7±1.8)Ma;形成于晚泥盆世末期,结合前人的研究资料认为在~360 Ma由于南天山洋板片的回撤或俯冲流体参与,上覆地幔发生部分熔融产生了基性岩浆,岩浆上涌过程中提供大量的热导致地壳发生部分熔融形成了酸性岩浆,两种岩浆发生不均匀混合作用。上涌的岩浆引起地幔对流,导致伊犁地块内部出现一定的伸展作用(弧后伸展作用)。