Geological Characteristics and Zircon U-Pb Dating of Volcanic Rocks from the Beizhan Iron Deposit in Western Tianshan Mountains, Xinjiang, NW China

The Beizhan large iron deposit located in the east part of the Awulale metallogenic belt in the western Tianshan Mountains is hosted in the Unit 2 of the Dahalajunshan Formation as lens, veinlets and stratoid, and both of the hanging wall and footwall are quartz-monzonite; the dip is to the north with thick and high-grade ore bodies downwards. Ore minerals are mainly magnetite with minor sulfides, such as pyrite, pyrrhotite, chalcopyrite and sphalerite. Skarnization is widespread around the ore bodies, and garnet, diopside, wollastonite, actinolite, epidote, uralite, tourmaline sericite and calcite are ubiquitous as gangues. Radiating outwards from the center of the ore body the deposit can be classified into skarn, calcite, serpentinite and marble zones. LA-ICP-MS zircon U-Pb dating of the rhyolite and dacite from the Dahalajunshan Formation indicates that they were formed at 301.3±0.8 Ma and 303.7±0.9 Ma, respectively, which might have been related to the continental arc magmatism during the late stage of subduction in the western Tianshan Mountains. Iron formation is genetically related with volcanic eruption during this interval. The Dahalajunshan Formation and the quartz-monzonite intrusion jointly control the distribution of ore bodies. Both ore textures and wall rock alteration indicate that the Beizhan iron deposit is probably skarn type.

Metallogenic Epoch and Ore-forming Environment of the Lamasu Skarn-porphyritic Cu-Zn deposit,western Tianshan,Xinjiang,NW China

Granitic rocks, widely developed in the Lamasu copper ore region, western Tianshan were formed at 390.5±7.7 Ma according to the SHRIMP zircon U-Pb dating of the plagioclase granite porphyry. Based on the regional tectonic evolution and published chronological data of both diagenesis and mineralization, the Biezhentao- Kokirqin region was rolled into the orogen associated with the closure of Yili Ocean during early Devonian. The N-S-trending thrust faults were formed during this period and accompanied by the intrusion of granitic rocks. On this stage, the paleo-Asian Ocean Plate entered into the early collision orogenic phase and the plagioclase granite porphyry intruded （390.5±7.7 Ma） and replaced with limestone of the Mesoproterozoic Kusongmuqieke Group, Jixianian System and formed the early phase of skarn-type copper mineralization in the Lamasu region. Furthermore, the subduction-melting of Bayingou Ocean Plate during Carboniferous generated a deep-seated magmatic chamber in the Lamasu copper ore region which located in the northwestern part of the Paleozoic Biezhentao-Kokirqin island arc. The magmatic chamber segregated Cu-bearing magmas, which transported upward to the shallow earth crust along the faults or fractures and formed the Cu-hosting porphyry. According to the research on the characteristics of the ore deposit and the ore-forming environment as mentioned above, the Lamasu Cu-Zn deposit was characterized by the superposing of mineralization at different geological settings and it was skarn-porphyritic type.

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.

Permo-Carboniferous Radiolarians from the Wupata'erkan Group,Western South Tianshan, Xinjiang, China

The Wupata'erkan Group, also called Wupata'erkan Formation, distributed in the South Tianshan, Xinjiang, China, mainly consists of gray and dark gray fine-grained clastic rocks, interlayered with volcanic rocks, carbonates and cherts. Some ultra-basic rocks (blocks) punctuate the formation. The formation was variously assigned to Silurian-Middle Devonian, Silurian-Lower Devonian, and pre-Devonian, mainly based on Atrypa bodini Mansuy, Hypothyridina parallelepipedia (Brour.) and Prismatophyllum hexagonum Yoh collected from the limestone interlayers, respectively. However, radiolarian fossils obtained from 24 chert specimens of the Wupata'erkan Group, mainly include Albaillella sp. cf. A. undulata Deflandre, Albaillella sp. cf. A. paradoxa Deflandre, Albaillella cf. A. deflandrei Gourmelon, Albaillella sp. cf. A. indensis Won, Albaillella sp. cf. A. excelsa Ishiga, Kito and Imoto, Albaillella sp. and Latentifistulidae gen. et. sp. indet., are earliest Carboniferous and Late Permian. The earliest Carboniferous assemblage is characterized by Albaillella sp. cf. A. undulata Deflandre, Albaillella sp. cf. A. paradoxa Deflandre, Albaillella cf. A. deflandrei Gourmelon and Albaillella sp. cf. A. indensis Won, and the Late Permian assemblage by Albaillella sp. cf. A. excelsa Ishiga, Kito and Imoto. This new stratigraphic evidence indicates that the Wupata'erkan Group is possibly composed of rocks with different ages from Silurian to Permian, and therefore, it is probably an ophiolite melange. The discovery of Late Permian Albaillella sp. cf. A. excelsa provides more reliable evidence supporting the existence of a Permian relic ancient oceanic basin in the western part of Xinjiang South Tianshan.

Association of Late Paleozoic Adakitic Rocks and Shoshonitic Volcanic Rocks in the Western Tianshan, China

The late Paleozoic adakitic rocks are closely associated with the shoshonitic volcanic rocks in the western Tianshan Mountains, China, both spatially and temporally. The magmatic rocks were formed during the period from the middle to the late Permian with isotopic ages of 248-268 Ma. The 87Sr/86Sr initial ratios of the rocks are low in a narrow variation range (-0.7050). The 143Nd/144Nd initial ratios are high (-0.51240) with positive εND(t) values (+1.28-+4.92). In the εNd(t)-(87Sr/86Sr)i diagram they fall in the first quadrant. The association of the shoshonitic and adakitic rocks can be interpreted by a two-stage model: the shoshonitic volcanic rocks were formed through long-term fractional crystallization of underplated basaltic magma, while the following partial melting of the residual phases formed the adakitic rocks.

Differential Evolution of High-Pressure and Ultrahigh-Pressure Metapelites from Habutengsu, Chinese Western Tianshan: Phase Equilibria Modelling and ^(40)Ar/^(39)Ar Geochronology

Metapelite is one of the predominant rock types in the high-pressure–ultrahigh-pressure（HP–UHP） metamorphic belt of western Tianshan, NW China; however, the spatial and temporal variations of this belt during metamorphism are poorly understood. In this study, we present comparative petrological studies and 40^Ar/39 ^Ar geochronology of HP and UHP pelitic schist exposed along the Habutengsu valley. The schist mainly comprises quartz, white mica, garnet, albite and bluish amphibole. In the Mn O–Na2O–Ca O–K2O–Fe O–Mg O–Al2O3–Si O2–H2O（Mn NCKFMASH） system, P–T pseudosections were constructed using THERMOCALC 333 for two representative pelitic schists. The results demonstrate that there was a break in the peak metamorphic pressures in the Habutengsu area. The northern schist has experienced UHP metamorphism, consistent with the presence of coesite in the same section, while the southern one formed at lower pressures that stabilized the quartz. This result supports the previous finding of a metamorphic gradient through the HP–UHP metamorphic belt of the Chinese western Tianshan by the authors. Additionally, phengite in the northern schist was modelled as having a Si content of 3.55–3.70（a.p.f.u.） at the peak stage, a value much higher than that of oriented matrix phengite（Si content 3.32–3.38 a.p.f.u.）. This indicates that the phengite flakes in the UHP schist were subjected to recrystallization during exhumation, which is consistent with the presence of phengite aggregates surrounding garnet porphyroblast. The 40^Ar/39^ Ar age spectra of white mica（dominantly phengite） from the two schists exhibit similar plateau ages of ca. 315 Ma, which is interpreted as the timing of a tectonometamorphic event that occurred during the exhumation of the HP–UHP metamorphic belt of the Chinese western Tianshan.

Variations of Snow Temperature and their Influence on Snow Cover Physical Parameters in the Western Tianshan Mountains,China

This article discussed about snow temperature variations and their impact on snow cover parameters. Automatic temperature recorders were used to sample at lo-minute intervals at the Tianshan Station for Snow-cover and Avalanche Research, Chinese snow temperature Academy of Sciences. lo-layer and the snow cover parameters were measured by the snow property analyzer （Snow Fork） in its Stable period, Interim period and Snow melting period. Results indicate that the amplitude of the diurnal fluctuation in the temperature during Snow melting period is 1.62 times greater than that during Stable period. Time up to the peak temperature at the snow surface lags behind the peak solar radiation by more than 2.5 hours, and lags behind the peak atmospheric temperature by more than 0.2 hours during all three periods. The optimal fitted function of snow temperature profile becomes more complicated from Stable period to Snow melting period. 22 h temperature profiles in Stable period are the optimal fitted by cubic polynomial equation. In Interim period and Snow melting period, temperature profiles are optimal fitted by exponential equation between sunset and sunrise, and by Fourier function when solar radiation is strong. The vertical gradient in the snow temperature reaches its maximum value at the snow surface for three periods. The peak of this maximum value occurs during Stableperiod, and is 4.46 times greater than during Interim period. The absolute value of temperature gradient is lower than 0.1℃ cm-1 for 30 cm beneath snow surface. Snow temperature and temperature gradient in Stable period-Interim period indirectly cause increase （decrease） of snow density mainly by increasing （decreasing） permittivity. While it dramatically increases its water content to change its permittivity and snow density in Snow melting period.

Constraints of REE and trace elements of high-pressure-veins and host rocks in western Tianshan on origin of deep fluids in paleosubduction zones

The western Tianshan high-pressure(HP) metamorphic belt represents the paleosubduction mélange of paleozoic south Tianshan ocean between the Yili-central Tianshan and Tarim plates. High-pressure veins are extensively developed in this HP belt. Compared with normal mid-ocean ridge basalt(N-MORB), the high-pressure veins and host rocks are enriched in light rare earth elements(LREE) and incompatible elements. But high-pressure veins show a larger variation than host rocks in total REE abundance. On the trace element spidergram, all the samples are enriched in incompatible elements and show strong positive Pb anomaly relative to N-MORB. The array tendency lines of plots of the HP rocks have apparent slopes on diagram of m(Sr) vs m(Sr)/m(Zr), m(Li) vs m(Li)/m(Y) and (m(Ce)) vs m(Ce)/m(Pb), which indicates that the enrichment in LREE and incompatible elements relative to N-MORB of the HP-metamorphic rocks from western Tianshan is not attributed to magma evolution process of the protolith. High field strength elements, such as Nb, Ta, Ti, Zr and Hf, do not show negative anomaly relative to N-MORB, which is dissimilar to that of island arc basalts. Therefore, the enrichment in LREE and incompatible elements of the HP rocks is not attributed to the enrichment of the source of the protolith. The mass ratios of Rb to Ba, Ce to Pb, Nb to U and Ta to U of high-pressure veins and host rocks are intermediate of mid-ocean ridge basalt or oceanic island basalt and continental crust. The fluids in western Tianshan paleosubduction zones are mixtures of two sources, dehydration or devolatilization of host rocks and of subducted sediments.

Study on the Source Parameters of Earthquakes in the Middle Eastern Area of North Tianshan in Xinjiang

By applying the empirical Green＇s function method, we first proved that the source spectra in the middle eastern area of North Tianshan follow the ω^-2 Brune model, and then, on this basis, obtained the source spectra for 105 earthquakes of ML 2.5 - 5.7 in the studied area upon removing the noise, instrument, propagation and site effects in the observational seismic S waveforms. Finally, we determined the source parameters such as the seismic moment, stress drop, source dimension, etc., based on the Brune model. The results show that there is a good linear correlation between scalar seismic moment, M0, and ML, which is Log10 M0 = 1.10 ML ＋ 17.20; The source radii range between 100- 1500m; the stress drop, 1-16MPa with a predominant range of 1 - 10MPa. The relationship of the seismic moment versus corner frequencies indicates that there may exist two source scaling, that is, when M0 〈 4×10^21 dyne. cm （equal to an ML4.0 event）, stress drop is weakly dependent on M0： whereas, when M0 〉 4×10^21 dyne·cm, stress drop is independent of M0.

Analysis on Variations of the Temperature and Precipitation in North Slope Area of the Western Tianshan in Recent 50 Years

[Objective] The research aimed to analyze variation characteristics of the temperature and precipitation in north slope area of the Western Tianshan in recent 50 years.[Method] According to temperature and rainfall data from 1961 to 2010 at three meteorological stations in north slope area of the Western Tianshan,climate change in the zone in recent 50 years was analyzed by using linear trend analysis method and 5-year sliding average method.[Result] The temperature in north slope area of the Western Tianshan showed significant warming trend.The annual average temperature significantly increased at 0.3 ℃/10 a in recent 50 years.But rise rates of the temperature in different seasons were different:autumn> winter> spring> summer.The annual rainfall in north slope area of the Western Tianshan in recent 50 years overall presented relative increase trend.Seen from annual rainfall,it significantly increased at 16.9 mm/10 a.Seen from seasonal rainfall,except in autumn,rainfalls in other three seasons in the past 50 years all showed significant increase trends,with amplitude of 3.2-11.2 mm/10 a.The largest increase amplitude was in summer.After a small precipitation peak in the 1980s,autumn rainfall slightly declined in the past 20 years.[Conclusion] The climate in north slope area of the Western Tianshan become warm and wet.

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.

Spatiotemporal variations in the growth status of declining wild apple trees in a narrow valley in the western Tianshan Mountains, China

Malus sieversii(wild apple tree),only distributed in the Tianshan Mountains in Central Asia,is a tertiary relic species and an ancestral species of cultivated apples.However,existing natural populations of wild apple trees have been declining.To date,spatiotemporal variations in the growth status of declining wild apple trees and influencing factors in the narrow valley areas in the Tianshan Mountains remain unclear.In this study,field investigation and sampling were carried out in three years(2016-2018)at four elevations(1300,1400,1500,and 1600 m)in the Qiaolakesai Valley(a typical longitudinal narrow valley in the Yili River Valley)of the western Tianshan Mountains in Xinyuan County,Xinjiang Uygur Autonomous Region,China.Projective coverage,dead branch percentage,and 18 twig traits(these 20 parameters were collectively referred to as plant traits)were determined to comprehensively reflect the growth status of declining wild apple trees.The values of dead branch percentage ranged from 36%to 59%,with a mean of 40%.Year generally showed higher impact on plant traits than elevation.In 2017 and 2018,projective coverage,leaf size,leaf nitrogen concentration,and nitrogen to phosphorous ratio were markedly higher than those in 2016.However,dead branch percentage and leaf and stem phosphorous concentrations showed the opposite trend.Most of the topological parameters of plant trait networks differed in the three years,but the strength of trait-trait association increased year by year.The mean difference between day and night temperatures(MDT),annual accumulative precipitation,soil electrical conductivity,and soil pH had the greatest impact on the plant trait matrix.The growth status of declining wild apple trees was directly and positively affected by MDT and leaf size.In conclusion,the growth of declining wild apple trees distributed in the narrow valley areas was more sensitive to interannual environmental changes than elevation changes.The results are of great significance for further revealing the decline mechanism of wild apple trees in the Tianshan Mountains.

Fluid flow on centimeter-scale in deep paleosubduction zones in western Tianshan,China:Evidence from high-pressure veins

High-pressure(HP)veins were extensively developed in western Tianshan high-pressure(HP)metamorphic belt.The HP vein and host-rocks were analyzed by electronic microprobe to trace the origin of vein-forming fluids.Analytical data show that the immediately adjacent host-rocks of the studied HP vein are eclogites and gradually turned into blueschist as the distance from the veins increases,which indicates that the vein-forming fluid was derived from adjacent host-rocks;the boundaries between the vein and the host-rocks are sharp,which indicates that the fracture of the host-rocks is brittle during the vein-forming process.It is suggested that this type of HP veins is precipitated from the liquid formed by the dehydration of the host-rocks during the prograde metamorphism from blueschist to eclogite facies,which results in hydrofracturing of the rocks and provides the space for the vein to precipitate.The width of the eclogite-facies host-rocks is usually 1-2 cm,which provides the direct evidence that the fluid flow is on centimeter-scale.

A Report of the Newly Discovered Cu–Ni Ore Deposit in the West of East Tianshan, North Xinjiang, China

Objective The Early Permian mafic-ultramafic intrusions （298- 270 Ma, Mao et al., 2008）, which are widely distributed in different tectonic domains in North Xinjiang, host magmatic sulfide ore deposits, making North Xinjiang the second most important region for Ni resources in China. The bulk of Cu-Ni ore deposits in East Tianshan, making up a large portion of Ni resources in North Xinjiang, were concentrated in the east of East Tianshan （the Huangshan- Jing＇erquan region） （Feng Yanqing, et al., 2017）, while no any analogue was discovered in the west of East Tianshan until the Lubei Cu-Ni （Co） ore deposit （90°21＇E, 42°10rN） was identified by Xinjiang Geological Survey in 2014. The Lubei Cu-Ni （Co） ore deposit is a medium- to large- sized deposit with Ni and Cu grades in the range 0.2%- 7.76% and 0.2%-2.30%, respectively. This work has initiated the prospection for a large-sized Cu-Ni ore deposit in the west of East Tianshan.

The Depositional Environment of the Cretaceous Kizilsu Group in Xinjiang——With a Discussion of the Lowermost Marine Horizon of the Cretaceous in the Western Tarim Basin

In this paper. it is demonstrated that there exist marine horizons in the upper part of the lower subcycleand the upper subeycle of the Kizilsu Group in Xinjiang. based on new evidence of authigenic glauconite.boron content. carbon and oxygen stablc isotopic analyses. and lithological and sedimentary features. The up-per part of the lower subeycle is the lowermost marine horizon of the Cretaceous in the western Tarim Basin,which is inferred to be of Barremian age.

Geochemical Characteristics of Granitoids in the Eastern Sector of the Northern Tianshan Mountains in Xinjiang

The granitioids in question are located in the geosynclinal fold belt of the Northern Tianshan Mountains.The magmas are intruded into a Carboniferous marine volcanic-sedimentary rock series. forming a contempo-raneous. intermediate-basic to acid. composite intrusion. With a whole-rock Rb-Sr isochron age of 315.7 Ma. itis considered to be of middle Heicynian age. The granitoids have a SiO_2 content of 48-78%, a calc-alkali indexof 60 and silica-alkali indices ρ=2.2-2.4 and σ=1.5-2. From basic to acid compositions, the total REE con-tent increases from 38 to 143 ppm. δEu ranges from 0.47 to 0.86 and the Eu anomalies are negative. Thenormalized curves of REE of various rock types are very similar. These coupled with the characteristics of traceelement geochemistry show that the intrusion is an island arc-continental margin, calc-alkaline one. Theδ^(18)O values range from 5.8 to 8.9‰ and the ^(87)Sr/^(86)Sr initial ratio is 0.705. The materials of the intrusion arecomposed of a mixture of the magmas at the top of the upper mantle and in the lower crust, This indicates thatthe rocks might be consanguineous. differentiated and evolved products and possess the characteristics of Ⅰtype granites.

Zircon U-Pb Ages and Tectonic Implications of Late Paleozoic Volcanic Rocks in the Western Tianshan,North Xinjiang,China

The Late Paleozoic volcanic rocks are widespread in the Western Tianshan,and mainly consist of basalt,trachyte,trachy-andesite,andesite and rhyolite.However,the formation timing and tectonic implications of the volcanic rocks remain controversial.To obtain a comprehensive dataset with adequate spatial coverage,we collected the published zircon U-Pb age data of the Late Paleozoic volcanic rocks in the Western Tianshan,and mapped the temporal and spatial distribution of these volcanic rocks.Our compiled dataset indicates that the volcanic rocks in the Western Tianshan were formed in two major stages:Late Silurian-Early Carboniferous and Late Carboniferous-Middle Permian.The southward subduction of the Northern Tianshan Ocean formed a large number of Late Silurian-Early Carboniferous volcanic rocks.The flare-up of Late Carboniferous to Middle Permian magmatism in the NTOB was considered to be the response of the slab-roll back of the northern Tianshan Ocean.Therefore,arc magma assemblage and spatial-temporal distribution are of great significance to identify the dynamic mechanism transformation of subduction zone.