A new methodology for identification of potential pay zones from well logs: Intelligent system establishment and application in the Eastern Junggar Basin, China

In recent years, as the exploration practices extend into more complicated formations, conventional well log interpretation has often shown its inaccuracy and limitations in identifying hydrocarbons. The Permian Wutonggou Formation hosts typical clastic reservoirs in the Eastern Junggar Basin. The sophisticated lithology characteristics cause complex pore structures and fluid properties. These all finally cause low well testing agreement rate using conventional methods. Eleven years＇ recent statistics show that 12 out of 15 water layers have been incorrectly identified as being oil or oil/water layers by conventional well log interpretation. This paper proposes a methodology called intelligent prediction and identification system （IPIS）. Firstly, parameters reflecting lithological, petrophysical and electrical responses which are greatly related to reservoir fluids have been selected carefully. They are shale content （Vsh）, numbered rock type （RN）, porosity （φ）, permeability （K）, true resistivity （RT） and spontaneous-potential （SP）. Secondly, Vsh, φ and K are predicted from well logs through artificial neural networks （ANNs）. Finally, all the six parameters are input into a neuro-fuzzy inference machine （NFIM） to get fluids identification results. Eighteen new layers of 145.3 m effective thickness were examined by IPIS. There is full agreement with well testing results. This shows the system＇s accuracy and effectiveness.

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.

Temporal and Spatial Distribution of the Late Devonian (Famennian) Strata in the Northwestern Border of the Junggar Basin, Xinjiang, Northwestern China

The base of the Saerba Member （Mbr） of the Hongguleleng Formation （Fm.） probably lies in the Famennian Palmatolepis crepida Zone; the Longkou Mbr is probably a sedimentary wedge that thins out northwards; the Duguer Mbr has an approximate age from the upper part of the Pa. marginifera Zone or the Lower Pa. rugosa trachytera Zone through the top of the Pa. perlobata postera Zone; the Wulan Mbr has an age approximately corresponding to the whole Pa. gracilis expansa Zone. In the Bulongguoer section, the Lower Mbr of the Hongguleleng Fro. corresponds to Famennian Pa. crepida Zone through Pa. marginifera Zone; the Middle Mbr probably ranges from the Pa. r. trachytera Zone through the Pa. g. expansa Zone. The basal Namu Mbr of the Heishantou Fm. is probably the product during and after the Hangenberg Event in the upper part of the Siphonodellapraesulcata Zone, which is still within the Devonian. In this context, the underlying Chasi Mbr may approximately correspond to the lower part of the S. praesulcata Zone （before the Hangenberg Event）. Lateral distribution of strata indicates that the Upper Devonian in the Gennaren and Saerba areas each constitutes a structure of syncline, which differs from the previous recognition of a monocline structure.

MASTODONT REMAINS FROM THE MIOCENE OF JUNGGAR BASIN IN XINJIANG

The mastodont materials described in the present paper, associated with Amblycastor tunggurensis, Amphicyon sp., Anchitherium cf. aurelianense, Brachypotherium sp., ?Chilotherium sp., Stephanocemas thomsoni, Dicrocerus grangeri, Eotragus sp., Oioceros grangeri and O. noverca, were collected from the Haramagai formation of Junggar Basin in Xinjiang by an IVPP field team in 1982. The geology of the area has already been reported by Tong (1986, 1987). The mastodont fossils found at 5 sites on the north and west banks of the Ulungur river, Junggar Basin are abundant. They comprise 5 species, among which is one new species.The author is greatly indebted to the IVPP field team (Tong, Y., the head of the 1982 Junggar field team) allocating the mastodont materials for me to study.

LA-ICP-MS Zircon U-Pb Dating of the Huangyangshan Pluton and Its Enclaves from Kalamaili Area Eastern Junggar,and Geological Implications

LA-ICP-MS zircon U-Pb dating has revealed that the Huangyangshan pluton in Eastern Junggar was formed at 311±12 Ma,and that microgranular enclaves were formed at 300±6 Ma;both ages are very consistent within errors.It is the first time that the microgranular enclaves age in Kalamaili area was determined.Petrochemistry and geochemistry research shows the characteristics of host rock as follows:

The Petrology and Geochemistry of Listwaenite in the Sartohay Ophiolitic Melange of West Junggar, Xinjiang, China

The west Junggar,located in the eastern part of Balkash-Junggar tectonic province,is a major component of the core of the Central Asian metallogenic region.This area is characterized by occurrences of ophiolitic mélanges,such as the Sartohay ophiolitic mélange in the NE and the Tangbale ophiolitic mélange in the west.As a hydrothermal alteration product of serpentinite in the Sartohay ophiolitic mélange,listwaenite lenses are gold-mineralized and crop out on surface in the ophiolitic mélange via weathering of exhumated hanging wall of fault zone.Listwaenite is mainly composed of magnesite,quartz,dolomite,and trace amounts of mariposite,chromian spinel,talc and sulfide.A vertical thermal gradient model for the hydrothermal alteration shows that serpentinite would first be transformed to talc schist,then into listwaenite as the ophiolite slices continued to rise along shear zone,with XCO2,oxygen and sulfur fugacity increase and temperature decrease.Both serpentine and magnetite were progressively destroyed during the transformation from serpentinite to talc schist,andcompletely vanished in listwaenite,while mariposite generated in weakly deformed to mylonitized listwaenite.Concentrations of most trace elements including high field strength elements and metallogenic elements,increasing from undeformed,through weakly deformed,to mylonitized listwaenite,show a positive correlation with deformation degree and content of apatite,rutile,monazite,zircon and sulfide in listwaenite.The shear zone served as pathways for percolation and accumulation of fluid and trace elements during the metasomatism from serpentinite to listwaenite.Compared to undeformed listwaenite,mylonitized listwaenite will be more favorable to be fractured and brecciated due to more intense shearing,which caused strong metasomatic reaction and then induced trace element-bearing mylonitized listwaenite.

The Middle Devonian Bimodal Association of Volcanic Rocks in the Northern Area of East Junggar, Xinjiang

The Middle Devonian volcanic rocks in the northern area of East Junggar, located between the Ertix andUlungur rivers of northern Xinjiang, may be divided into basic and acid ones. It is evident that a compositionalgap exists between the two groups so that the volcanic rocks are not in line with a calc-alkaline series becausethe intermediate rocks are absent in the area. The fact shows that the volcanic rocks are a typical bimodal asso-ciation. The formation of the bimodal association of volcanic rocks in the area was closely related to continen-tal rifting or continental extension in the Middle Devonian. In such a tectonic setting, magmas were first pro-duced by partial melting of the mantle. Where crustal thinning was greater, the magmas ascended and eruptedon the surface directly so that the basic volcanic rocks formed, but olivine and/or partial pyroxenefractionation occurred in the magmas during their ascent through the thinning crust. On the other hand, wherecrustal thinning was less, ascending mantle-derived magmas reached the lower crust and accumulated there, re-sulting in partial melting of the lower crust and thus giving rise to the contaminated magma which was consoli-dated as acid volcanic rocks on the surface.

Geochemical characteristics of crude oils from Well Zheng-1 in the Junggar Basin, Xinjiang,China

Well Zheng-1 is located in the combined area of the central uplift and the north Tianshan piedmont depression in the Junggar Basin. Two oil-bearing beds are recognized at 4788–4797 m of the Lower Cretaceous Tugulu Formation (K1tg) and 4808.5–4812.5 m of the Lower Jurassic Sangonghe Formation (J1s). The geochemical characteristics of family composition, carbon isotopic composition, saturated hydrocarbons, sterane and terpane biomarkers and carotane of two crude oils are described in this paper. The results show that the geochemical characteristics of the two crude oils are basically similar to each other, indicating they were all derived mainly from the high mature, brine, algae-rich lake facies sediments. Oil-source correlation revealed that crude oils of the two beds were derived mainly from the source rocks of Permian and mixed by the oil derived from the source rocks of Jurassic and Triassic. This is consistent with the geological background with several sets of source rocks in the area studied.

Sm-Nd isochron age evidence for Precambrian metamorphic rocks from the eastern Junggar in northern Xinjiang, China

The characterstic of the basement of Junggar block has been a topic of long-standingdebate.Based on the data of gravity and magnetic anomaly,some researchers deduced thatthere were Precambrian basic-ultrabasic complex on the basement of Junggar block.However,others maintained that the basement of Junggar block was probably the Paleozoicoceanic crust because of the lack of isotopic evidence and older outcrops aroundthe Junggar Basin. In recent years,molecules of fossil community were discovered from Aleandao Groupat the Qingshuiquan and Kamuster of eastern Junggar.Most of the fossils,such asPylocorpus,Retincnlafopora,Asteropyla,were found at the boundary between Cambrianand Sinian in Qinling and South China.An isotopic age of 1908 Ma for leuco-pink graniticgneiss from the lower Huangcaopo Group was gained by evaporated Pb-isotope method forsingle zircon in Xiaoluigou of eastern Junggar by Zhang et al.But all of these results onlyindicate a possibility that the basement of Junggar block consists of

Partnership for Prosperity Eastern province commits human and financial resources to drive Xinjiang's development

Bahram Rahimjan,a Uygur student of art,dreams big.With 17 months to go before sitting the gaokao,China's national college entrance examination,he said his dream school is the prestigious Central Academy of Fine Arts in Beijing,more than 3,000 km from his hometown."Painting makes me happy,"he said while honing his skills at his school in Cocodala,Xinjiang Uygur Autonomous Region in northwest China.He said he is interested in rediscovering Uygur culture through artistic creation.

Comprehensive constraint on the tectono-sedimentary setting of Late Paleozoic turbidites of the Kamuste area, eastern Junggar,Xinjiang

Petrography and geochemistry, combined with sedimentation analyses allow for a thorough evaluation of the tectono-sedimentary setting of late Paleozoic turbidites of the Kamuste area eastern Junggar. Sandstones of the Alabiye1) Formation are composed mostly of volcanic and sedimentary detritus with lesser amounts of plagioclase and quartz. They were derived from an undissected magmatic-arc provenance. The geochemistry of sandstone-mudrock suites indicates a fesic-intermediate igneous provenance, and constrains the Alabiye Formation to have derived from a differentiated oceanic-continental margin island-arc tectonic setting. Likewise, geochemistry and sandstone petrography of the Kamuste Formation reflect a mixed provenance signature dominated by magmatic arc, basement uplift, and subduction-complex sources of a differentiated continental-island arc. Sedimentation analysis indicates that the Alabiye and Kamuste formations are two sets of turbidite sequences deposited on a submarine slope and a submarine fan and basin plain respectively. In conclusion, submarine slope turbidite deposition of the Alabiye Formation records the main sedimentary response to the development of early Devonian back-arc basins of the northern Junggar tectonic belt. Submarine fan and basin plain turbidite and background hemipelagic deposition of the Kamuste Formation record the main sedimentary response to the late Early Carboniferous development of an inter-arc relict ocean basin of the eastern Junggar composite terrane.

Geodynamic significance of the A-type granites in the Sawuer region in west Junggar, Xinjiang: Rock geochemistry and SHRIMP zircon age evidence

Sawuer region is located in west Junggar, Jimunai County of Altay district and Hefeng County of Tacheng district, Xinjiang. The region is along the north margin of Kazakstan-Junggar plate. The intrusions (mainly acid) are widespread. Qiaqihai and Kuoyitasi intrusions are important in the region, with the characteristics of A-type granite. Further investigations indicate that they belong to A2-type granite that formed in extension tectonic setting of post collision. The REE chon-drite-normalized patterns of the intrusions show LREE enrichment and the δ Eu values are lower. The Nd, Sr, Pb isotope compositions of the intrusions indicate a mantle source, while the low δ 18O values resulted from the isotope exchange between intrusion and meteoric water. According to SHRIMP U-Pb age analysis results, the crystallization age of Qiaqihai intrusion is 290.7 ± 9.3 Ma (1σ ), and that of Kuoyitasi intrusion is 297.9 ± 4.6 Ma (1σ ), corresponding to the beginning of early Permian. The A2-type granites indicate that the region was in the extension period of the post-collisional stage at the beginning of early Permian in the Sawuer region. The A-type granites in the Sawuer region in west Junggar discovered from this work is analogous to the A-type granites found in east Junggar of the Ulungur alkali granites belt. The confirmation of post-collisional A-type granites of early Permian in the Sawuer region provides new evidence for the regional vertical continental crust growth in early Per-mian. The former proposed Ulungur alkali granites belt can extend from east Ulungur through west Ulungur and to Zhaisang in Kazakstan westwards.

The ^(40)Ar/^(39)Ar Ar metamorphic ages of Tangbale blueschists and their geological significance in West Junggar of Xinjiang

SINCE Tangbale blueschist was found in West Junggar of Xinjiang in 1983, its metamorphicage and tectonic significance have been discussed for a long time. However, no exact dat-ing has been done by now. In this note, we present the 40Ar/39Ar data of sodic amphibolesfrom the blueschists and discuss their possible geological significance.

Significance of native arsenic in the Baogutu gold deposit, western Junggar, Xinjiang, NW China

Native arsenic together with comb quartz and stibnite is found in the Baogutu gold deposit, western Junggar (Xinjiang), NW China. It is anhedral with various grain size (<0.001 to 2 mm), and contains 98 wt% to 98.7 wt% As. Micro-granular electrum, the main auriferous mineral in the Baogutu gold deposit, is commonly enclosed in or closely accompanied by native arsenic. Three ore-forming paragenetic stages could be identified. Native arsenic mainly formed at stage II which is also the major stage for gold deposition. Mineral assemblage formed at this stage is native arsenic-stibnite-electrum-arseno- pyrite-miargyrite-freibergite-pyrrhotite-pyrite. Based on native arsenic and its coexisting minerals, the temperature (230 to 170℃), oxygen fugacity (logfO2 = -42―-56.5) and sulfur fugacity (logf S2 = -13.3― -16.6) of stage II are estimated. From stage I to stage II, the temperature, sulfur fugacity and S2- concentration of hydrothermal fluid decrease obviously, whereas the As concentration increases. Coexistence with native arsenic of electrum and its contents of 0.5 wt%―1.3 wt% As suggest that As is important to transport Au when S2- concentration decrease in hydrothermal fluid. Crystallization of native arsenic induced the deposition of electrum and consequently the formation of the Baogutu gold deposit.

The Discovery of ～310 Ma Back-Arc Basin Basalt in the West Junggar,Xinjiang,NW China and its Geological Significance

Objective Mafic magmas can form in different tectonic settings with various geochemical characteristics depending on their mantle sources. Basalts generated in back-arc basins provide valuable perspectives on mantle structure and composition, on controls for melt generation, and on the sources responsible for arc magma genesis.

Recent glacial retreat and its effect on water resources in eastern Xinjiang

The eastern Xinjiang Basin is desperately short of water. Most rivers in the basin originate in the high eastern Tianshan, which has abundant precipitation and numerous alpine glaciers. Fieldwork conducted on three reference glaciers around Mt. Bogda in 1981 and 2009 suggests that they all strongly melt in summer, a process that has tended to accelerate in recent decades. Based on topographic maps from 1962 and 1972 and 2005/2006 satellite imagery, we investigated 203 glaciers near Mt. Bogda and 75 glaciers near Mt. Harlik. The results show that the surface area of the Mt. Bogda glaciers decreased by 21.6% (0.49% a?1) from 1962 to 2006. This was accompanied by a 181 m decrease in length and a 28% drop in ice volume. In the Mt. Harlik region, areal extent was reduced by 10.5% (0.32% a?1), length by 166 m, and volume by 14% between 1972 and 2005. South-facing glaciers lost more of their area than those that are north facing, yielding an areal loss of 25.3% and 16.9% for southern and northern slopes of Mt. Bogda, respectively, and 12.3% and 6.6% for the comparable slopes of Mt. Harlik. Glaciers smaller than 0.5 km2 in area experienced the strongest retreat, whereas glaciers larger than 2 km2 in area experienced gentle recession but may be the main contributors in the future to river runoff. Glacial ablation in eastern Xinjiang tends to be strong, and the water resources in this region are deteriorating. Also, a heavy reduction in the capacity of the local karez system, as well as a significant change in river runoff, can be related to glacial retreat. Combined, this will adversely affect the downstream city of Urumqi and the Turfan Basin.

Zircon U-Pb and Hf isotopes of volcanic rocks from the Batamayineishan Formation in the eastern Junggar Basin

内部结构的研究被进行从 Batamayineishan 形成调查 U-Pb 年龄，踪迹元素和玄武岩的锆石的 Hf 同位素。暗岩从练习井圣罐头被获得 1 在 Junggar 盆以内在东方 Luliang 上高举。跟踪所有样品是 magmatic 的锆石表演的元素数据，与类似的 REE 模式，包括积极 Ce (Ce=5.06134 ) ，而是否定 Eu (Eu=0.06 ? 0.55 ) 在重稀土元素元素的异例和丰富。在 25 谷物之中，一致年龄被细分进三个组；300.4 整潲祺潧整的年龄？

The Spatial-Temporal Distribution Patterns of Dyke Swarms in Central Asia and their Tectonic Significance: Case Studies in Eastern Tianshan and Western Junggar

Dykes are a special kind of intrusive rocks which were formed by deep magma intruded into the existing brittle fractures in the crust.Dykes swarms in different tectonic environments are very significant to re-construct the

Statistical Prediction of Endogenetic Gold Deposit in East Junggar,Xinjiang

The system of mineral deposit statistical prediction methods , based on the similarity - analogy theory , searching anomaly theory and the theory of ore - controlling by quantitative assemblage of metallotects , can be summarized into the following aspects : (1) concluding main ore - controlling conditions and ore - hunting indicators from typical deposits; (2)establishing geological concept model of deposits ; (3)selecting geological variable and dividing study units and granting specific value for each variable; (4) by the use of geological and mathematical geology method , building predication model , delineating prospective area for exploration and estimating the total resources; (5) evaluating the prospecting work . It is good practice to use this system for metallogenic prognosis and regional prospecting of gold deposit in East Junggar , Xinjiang and has achieved great success . As a result , we discovered the Kubusu gold mineralized belt . delineated prospective area - estimated total resources of gold in the belt and found out Kubusu gold deposit .

The Ophiolitic Mélanges in Strike-slip Fault Zones in West Junggar,Xinjiang,NW China

The West Junggar region of western China,located in the far eastern end of the Kazakhstan orocline,occupies the junction of the Siberia,Tarim and Kazakhstan blocks,which is crucial for palinspastic reconstruction of the CAOB.The principal rock assemblages in West Junggar include Paleozoic ophiolitic mélanges and a thick,undeformed Upper Devonian–Lower Carboniferous sedimentary succession as the boundary of the mélanges,both of which are intruded by sub-circular Upper Carboniferous granitoid plutons and intermediate-basic-mafic dykes.On the basis of the sedimentary structures like cross bedding and convolute bedding and the geochronology data,the Upper Devonian–Lower Carboniferous sedimentary successions were identified as the Tailegula,Baogutu,and Xibeikulasi formations from the bottom up,which is an apparent shallowing-upwards ocean basin fill succession,from radiolarian cherts through 2000 meters of flysch to a more neritic Baogutu Formation to a fluvial Xibeikulasi Formation.At the bottom of the Tailegula Formation there is a peperite-bearing unit:a succession of extrusive mafic rock,mainly basaltic lava,with interbeds or blocks of sedimentary rocks including carbonate,radiolarian chert,calcareous siltstone and minor fine-grained tuffaceous sandstone.Peperites in the Tailegula are thickest and best developed as the type section.Four types of peperites were identified based on of the volcanic clast shapes and sediment-matrix properties in Tailegula:(1)arbonatesediment-hosted fluidal peperites,(2)sandstone-hosted fluidal peperites,(3)tuff-hosted mixed fluidal and blocky peperites and(4)carbonate-sediment-hosted blocky peperites.Zircon LA-ICP-MS U-Pb dating of a tuff lens enclosed by lava showed that the peperites formed in the Late Devonian(ca.364 Ma).The widespread peperitebearing succession in the Tailegula Formation is of variablethickness at different sites in West Junggar,such as the Tailegula,Baijiantan,Kalaxiuka,Saertuohai,Dagun,west of the Akebastaw granite and Shinaizha areas.The peperite-bearing unit is generally undeformed in contrast to the highly deformed slices of ophiolite,and is continuously distributed as a stratigraphic section regionally on either side of the Darbut and Baijiantan ophiolitic belts.It can be taken as a mark layer to demonstrate the existence of a shallow remnant ocean basin from the end of Devonian in West Junggar,which is an important component of oceanic crust in the remnant ocean basin.Peperite,underlying Devonian or earlier oceanic crust developed in the spreading process of the ocean basin,and overlying Carboniferous remnant ocean basin-fill succession constitute the complete evolution sequence of the remnant ocean basin.The Darbut and Baijiantan ophiolitic belts should not be interpreted as significant plate boundaries and represent the underlying ocean crust uplifted along tectonic lineaments within a continuous shallow remnant ocean basin.The Baijiantan and Darbut ophiolites are both steep fault zones(>70°)of serpentinite mélange,in contact on either side with regionally distributed and undeformed Upper Devonian–Lower Carboniferous ocean-floor peperitic basalts and overlying sedimentary successions.Ultramafic rocks is serpentinized and foliated to form the matrix of mélange.Some small blocks of peridotite are mylonitic and strongly foliated.Blocks of gabbro generally underwent prehnitization,epidotization and chloritization and many are metasomatized to rodingite.Pods of medium to fine grained amphibolites are encased in serpentinite and display relict gabbroic textures and amphibolite-facies assemblages.The Baijiantan ophiolitic mélange also includes amphibolite brecciasconsistingofcentimeter-sizedmylonitic amphibolite clasts embedded within a serpentinite matrix.Basalt lavas cropping out in the Baijiantan ophiolitic mélange are of two types:type 1 and type 2 lavas.The type1 lavas occur within the fault zones as small blocks withinthe matrix of ultramafic rocks,tectonically juxtaposed against other rocks.The type 2 basalt lava came from the peperite-bearing unit.Besides the ultramafic rocks,gabbros,and basalt lavas,the other supracrustal rocks in the ophiolitic mélange include sandstone,chert,tuff,and very rare limestone.Sandstones predominate and most of them are tuffaceous;their characteristics are consistent with the sandstones from surrounding Lower Carboniferous sedimentary formations.Sandstone blocks within the mélanges also have detrital zircon age distributions(300-400 Ma)and characteristics similar to surrounding Carboniferous sediments.The rock assemblages in the mélanges indicate the ophiolitic mélanges consist of locally derived rocks,in contrast to conventional ophiolitic mélanges.The ophiolitic mélanges show classic structural features of strike-slip shearing regimes,including subhorizontal slickenside lineations(<20°),consistent steeply dipping foliation(>75°)in the matrix,and elongated shapes of blocks aligned parallel to the shear zone.Consistent shear-sense indicators including slip-fiber lineations,Riedel shears,asymmetric blocks,shear band cleavages and veins indicate a horizontal sinistral sense of movement.The occurrence of the amphibolite and ultramafic mylonite in the mélanges probably record early,deep-seated strike slip,indicating that the fault zones extended downward through the oceanic crust.The amphibolite-facies metamorphism then was superimposed by brittle deformation at a shallow level to form fault breccias during the mélange formation.So the ophiolitic mélanges originated from crustal-scale sinistral strike-slip fault zones,not as major plate boundaries or subduction-suture zones.The youngest units of the mélanges are the deformed blocks of Lower Carboniferous basin-fill sedimentary rocks,indicating that the ultimate formation of the mélanges was after deposition of the Lower Carboniferous strata(detrital zircon age modes:320-330 Ma),but before the age of the intruding granite and the dike cutting the mélanges(~310 Ma).Based on above discussions and taking into consideration of the previous studies,a tectonic evolution scenario is proposed for the Devonian to Carboniferous in the West Junggar region.In the middle Devonian or earlier(>390Ma),a paleo-ocean basin existed,stretching across North Xinjiang from Darbut-Baijiantan area in West Junggar to the Kalamaili area in East Junggar.This basin was most likelyaback-arcbasinrelatedtothe Boshchekule–Chengiz–Yemaquan arc.Subduction ended in thepaleo-oceanbasinrepresentedbythe Hongguleleng-Kujibai-Armantai ophiolite belt by late Devonian(375-360 Ma),leading to slab break-off and upwelling of asthenosphere under the remnant ocean basin,which induced The OIB-like basalts in West Junggar.The oceanic basin started to receive sufficient sediment deposition into which OIB-like basalts flows could bulldoze to form the regional distributed peperites(~360 Ma).A little later,in the early Carboniferous(~340 Ma),continent-continent collision took place between the Junggar block and the Yemaquan arc,and Kalamaili ophiolite obduction occurred in the eastern part of Junggar block.The remnant ocean basin was preserved in the western part of the Junggar Block.Accompanying the relative motion between Junggar block and ocean basin in West Junggar during collision,a series of NW trending sinistral strike-slip faults were triggered and activated parallel to the western boundary of the Junggar block.During the late stage of the Early Carboniferous(~320 Ma),the remnant ocean basin was almost filled with sediments.The collision between the Yili and Junggar blocks at the beginning of the late Carboniferous reactivated the strike-slip faults,which disrupted the oceanic crust and basin-fill successions and caused diapirs of serpentinite to form the Baijiantan and Darbut ophiolitic mélanges.The emplacement of Upper Carboniferous(~310 Ma)stitching A-type granitoid plutons indicates the evolutionary history of the remnant ocean basin and strike-slip fault zone ophiolitic mélanges terminated by that time.