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The West Kunlun orogenic belt located in the northwestern margin of the Qinghai-Tibet Plateau is an important record of the formation and northward extension of the plateau, but the current research mainly focuses on the tectonic activities of the Cenozoic era, and there is still considerable controversy regarding the formation and evolutionary history of pre-Cenozoic orogenic belts. This study focuses on Cretaceous sandstone samples from the Kedong region in the piedmont belt of the West Kunlun orogenic belt. U-Pb geochronological analysis was performed on 200 detrital zircon grains from the core samples. Combined with stratigraphic data and previous research, the main provenance direction was investigated to constrain the tectonic evolutionary history of the orogenic belt's peripheral regions. The results show that the detrital zircons are aged from 290 to 208 Ma, 520-310 Ma, 810-580 Ma, 1,400-880 Ma and 2,548-1,730 Ma, reflecting the complexity of provenance in this area. Based on a comprehensive analysis of the characteristics of igneous rocks, zircon age composition and stratigraphic conditions in potential source areas, it is concluded that the primary source regions include the East Kunlun orogenic belt and the North and South Kunlun terranes, with a low likelihood of contributions from within the Tarim Basin. The evolution of the West Kunlun orogenic belt can generally be divided into two opening and two closing phases. The detrital zircon ages predominantly exhibit two peak values at 259 Ma and 459 Ma, respectively representing the ages of transition from oceanic crust subduction to continentcontinent collision for the Paleo-Tethys Ocean and the Proto-Tethys Ocean. Additionally, there is a temporal gap between the evolution of the Proto-Tethys Ocean and the Paleo-Tethys Ocean. The Triassic period marks a transitional phase in tectonic evolution, shifting into an intracontinental evolutionary stage. This study provides new geochronological evidence for the early developmental history of the West Kunlun orogenic belt. [ABSTRACT FROM AUTHOR]

The West Qinling Orogenic Belt (WQOB) in central China records the tectonic evolution and deep geodynamics process associated with plate collision on the northeastern margin of the Qinghai-Tibet Plateau. The study of the deep-seated West Qinling structure is beneficial for revealing the evolution of the West Qinling crust during the continental collision orogeny, and also has significance for mineral exploration. In this study, the crustal structure and the distribution of major faults in the West Qinling Orogen are calculated by processing geophysical aeromagnetic and ground gravity data. The density and magnetic susceptibility differences between the West Qinling crust and the upper mantle are calculated by fitting, and the depth and trend of the faults related are inferred from the gravity and magnetic inversion results. Due to the overall subduction of the lower crust of the Ruoergai to the West Qinling Orogenic Belt, the structural deformation within the West Qinling is strong, and the geophysical magnetic field and gravity field are suddenly changed. It is indicated that the formation of the Diebu-Sanhe fault may have a strong correlation with the Mianlue suture zone, and their intersection may penetrate into the lower crust at a depth of about 50 km or more. The West Qinling structure represents important conduits for migrating magmatic-derived hydrothermal fluids. During the continental collision, the West Qinling major faults provided hydrothermal migration channels for ore-forming materials in different tectonic periods. Meanwhile, multiple the geological activities led to the formation of mineral deposits related to magmatic hydrothermal fluids. [ABSTRACT FROM AUTHOR]

The study area in the West Junggar Basin is known to be rich in hydrothermal gold deposits and occurrences, even though there has been minimum exploration in the area. It is here hypothesised that this area could host more gold deposits if mineral exploration methods were to be reinforced. This research is aimed at identifying geochemical anomalies of Au, and determining possible factors and conditions which facilitate the formation of anomalies by referring to As and Hg as gold pathfinders. Geostatistical analyst techniques have been applied to 9,852 stream sediments and bedrock data collected on a total surface of 1,280 km2 of West Junggar, Xinjiang (northwest China). The kriging interpolation and quantile-quantile plot methods, combined with statistical methods, successfully identified both Au and its pathfinders’ anomalies. In the present study, median was considered as background values (10.2 ppm for As, 9.13 ppb for Hg and 2.5 ppb for Au), whereas the 95th percentile were threshold values (28.03 ppm for As, 16.71 ppb for Hg and 8.2 ppb for Au) and values greater than thresholds are geochemical anomalies. Moreover, the high concentrations of these three discovered elements are caused primarily by hydrothermal ore mineralisation and are found to be controlled mainly by the Hatu and Sartohay faults of a northeast-southwesterly direction as well as their related secondary faults of variable orientation, which facilitate the easy flow of hydrothermal fluids towards the surface resulting in the formation of geochemical anomalies. Most of anomalies concentration of Au are found near the mining sites, which indicates that the formation of new Au anomalies is influenced by current or previous mining sites through geological or weathering processes. In addition, the low concentration of gold and its pathfinders found far from active gold mine or faults indicates that those anomalies are formed due to primary dispersion of hosting rock.

Early Carboniferous granitoids, distributed in the Yining and Central Tianshan blocks, Chinese western Tianshan, are important for deciphering their tectonic contexts and evolutionary history of the South Tianshan Ocean. Here we present LA-ICP-MS zircon U-Pb ages, in situ Hf isotopic data, and whole-rock geochemical data of the monzogranites and syenogranites from the Kalejun Mountains, southern part of the Yining Block, aiming to constrain their petrogenesis and geodynamic background. The results reveal that these monzogranites and syenogranites were emplaced at 356 Ma and 344 Ma, respectively. Geochemically, they are characterized by high SiO2 (68.74–75.76 wt.%) and K2O (4.58–6.18 wt%), low MgO (0.14–0.76 wt.%) and P2O5 (0.04–0.24 wt.%) contents. In addition, they are depleted in Ba, Sr, Eu, Ti, Nb, and Zr, and enriched in Rb, Cs, Th, and U. These features indicate that the Kalejun granites are high-silica I-type granites. The low positive εHf(t) values (+1.1 to +8.2) and old T D M 2 H f model ages (1294 to 827 Ma) of the studied zircons imply that the parental magma of these granites were derived from the reworking of Proterozoic basement with minor involvement of juvenile materials. Combined with the Late Devonian to Early Carboniferous magmatic activities in the Yining and Central Tianshan blocks (e.g. the discovery of A-type bubble rhyolites and high-Mg andesites), it is suggested that the Kalejun granites were likely related to the roll-back of the South Tianshan oceanic slab. Finally, we argue that the subduction of South Tianshan Ocean probably terminated at the end of the Early Carboniferous. [ABSTRACT FROM AUTHOR]

Massive Late Palaeozoic magmatic rocks are well developed along the northern margin of the Chinese western Tianshan. Previous studies mainly focused on the Carboniferous to Permian magmatism, and the Devonian magmatic rocks were rarely reported. Thus, this study presents new zircon U-Pb dating, whole-rock geochemistry and Lu-Hf isotopic data for the Late Devonian granitic plutons from the Kekesala area of the Chinese western Tianshan, aiming to elucidate their ages, petrogenesis, and tectonic settings. The Kekesala granitic plutons comprise granodiorites, monzogranites and syenitic granites. Zircon U-Pb dating results show they were emplaced in Late Devonian (ca. 372 Ma). Geochemically, the granodiorites and monzogranites are characterized by high-K calc-alkaline I-type series, and have low Ni and Cr, and weakly positive εHf(t) values, interpreted to be predominantly derived from partial melting of a lower crust with minor addition of mantle-derived materials; The syenitic granites with medium-K calc-alkaline features, exhibit high Sr and low Y and Yb, likely originated from partial melting of a subducted slab involving some mantle peridotites. The Kekesala I-type granitic plutons provide robust evidence for the existence of a subduction regime for the northern part of the Chinese western Tianshan in the Late Devonian. Based on the studied results, together with available data, we conclude that initial subduction of the North Tianshan Ocean began at least in the Middle Ordovician and terminated at the beginning of the Late Carboniferous rather than in the Middle Silurian. [ABSTRACT FROM AUTHOR]

Remnants of seamounts in association with ophiolites have been identified in some accretionary complexes of the Central Asian Orogenic Belt (CAOB). The nature of these seamounts and ophiolites will enable us to better understand continental growth and accretionary history of the CAOB. Here we provide an outline of the ophiolitic mélanges in West Junggar, NW China, with an aim of clarifying the geodynamic model and geological effect of seamount accretion and subduction. The ophiolitic mélanges in West Junggar with the age ranging from late Neoproterozoic to early Carboniferous display typical 'block-in-matrix' structures, and contain seamounts fragments. This study reconstructs the stratigraphic framework of seamount, which show similar lithological associations, including pillow basalt, volcanic breccia, limestone, chert, and clastic rocks, and compatible with the composition of seamounts exposed in modern oceans. Three different geodynamic models of seamount accretion were identified in West Junggar, including accretion in the accretionary prism, underplating to the overriding crust, and collision. The notable examples are related to Mayile and Hebukesaier ophiolitic mélange, Darbut and Karamay ophiolitic mélange, and Tacheng oceanic plateau, respectively. Moreover, the geological effects of seamount accretion in West Junggar are mainly involved in forearc deformation and uplift patterns, trench migration and jumping, magmatism at subduction zone, as well as geodynamics of oroclinal bending. A tentative model is thus proposed, in which the Kazakhstan orocline that involves asymmetric roll-back in response to seamount subduction and accretion, followed by bending associated with the convergence of Siberian and Tarim cratons. [ABSTRACT FROM AUTHOR]

Oroclines are map‐view deformation of Earth's crust resulting from bending of quasi‐linear elements. The Central Asian Orogenic Belt (CAOB) is one of the largest and long‐lived accretionary orogens in the world and mainly consists of the Kazakhstan and Tuva–Mongolian oroclines. However, the mechanism of the oroclines is still in debate. Therefore, in this paper, we combine some investigation of high bathymetric relief resistance to subduction, review oroclinal bending models of the Kazakhstan Orocline, and propose a tentative model that involves asymmetric rollback in response to seamounts subduction and accretion, followed by bending associated with the convergence of the Siberian and Tarim cratons. Moreover, the role of pinning due to seamount and ridge subduction is probably more important than the convergence of continents in the CAOB. This model is compatible with the occurrence of seamounts, the spatial migration of intra‐oceanic arcs, and the development of multiple rollback processes during amalgamation of Eurasia. However, only geochemical and geochronological data will enable definition of the seamounts in CAOB so far, without much matching structural data. So we need more work to understand seamounts subduction and accretion as well as orocline bending in CAOB. [ABSTRACT FROM AUTHOR]

The Carboniferous is an important period for understanding tectonic evolutionary history and subduction processes of Chinese western Tianshan orogen. Here, we present results of petrologic, geochemical, and in situ LA‐ICP‐MS zircon U–Pb and Hf isotope data from an Early Carboniferous mafic dike–syenitic granite association in Atengtao Mountain, Yili Block, aiming to constrain their ages and petrogenesis and tectonic significance. Zircon U–Pb dating results reveal that the mafic dikes and syenitic granites were coevally emplaced at ca. 345–349 Ma. Geochemically, the mafic dikes contain high MgO, Nb, TiO2, and Ta contents, low SiO2 contents, and high Na2O/K2O ratios, showing Nb‐enriched affinities. Additionally, they are enriched in LILEs, relatively depleted in HFSEs, and positive εHf(t) values (+1.2 to +8.7), likely representing melts derived from partial melting of a depleted mantle wedge metasomatized by subducted slab‐derived fluids, with minor involvement of asthenospheric components. Compared with mafic dikes, the coeval syenitic granites display calc‐alkaline I‐type features and have high SiO2, Al2O3, and low MgO, Mg# (<40), Ni, and Cr contents, considered to have been derived from the reworking of the Precambrian basement with an input of mantle‐derived components. These mafic dike–syenitic granite associations likely formed in an arc‐related setting rather than postcollision or mantle plume setting. In addition, pronouncedly higher zircon saturation temperature of the syenitic granites, compared with the coeval I‐type granitoids from western Tianshan, imply the occurrence of a thermal anomaly in this period (ca. 345 Ma). With these studied results, together with previously published data, we argue that a slab break‐off model was likely responsible for the mafic dike–syenitic granite association, and related rocks, in the western Yili Block during Early Carboniferous. [ABSTRACT FROM AUTHOR]

As an important part of the Central Asian Orogenic Belt (CAOB), Chinese western Tianshan contains voluminous Late Palaeozoic volcanic rocks. Here, we present geochronological, geochemical, and in situ Lu–Hf isotopic data from the Atengtao sanukitic high‐Mg andesites (HMAs) of the western Yili Block. LA‐ICP‐MS zircon U–Pb analyses indicate that the Atengtao high‐Mg andesites were generated in the Early Carboniferous (346 ± 2 Ma). All the studied rock samples are characterized by high MgO (3.30–5.45 wt.%), SiO2 (53.25–60.10 wt.%), Cr (90.3–157 ppm), and Ni (31.0–46.7 ppm) contents, with geochemical characteristics analogous to those of sanukitoids of the Setouchi Volcanic Belt (SVB), SW Japan, and Bieluagaxi area, West Junggar. The Atengtao sanukitic HMAs are enriched in LILE and LREE but depleted in HFSE, similar to those of typical arc‐related magmatic rocks. They are also characterized by high Nb (11.4–15.8 ppm) concentrations, high Th/La (0.3) and Th/Yb (2.6–4.0) ratios, and varying zircon εHf(t) values (−2.3 to +4.3). These features are suggested to result from the partial melting of a relatively enriched mantle wedge metasomatized by subducting oceanic slab‐derived sediments. Considering the occurrence of sanukitic HMAs, combined with the contemporaneous special rock assemblages (such as slab‐derived adakite, Nb‐enrich basalt, A‐type granite/rhyolite, and bimodal volcanic rocks) found in the western part of Yili Block, we propose that the generation of the Carboniferous sanukitic HMAs in Atengtao Mountain were most likely related to the slab break‐off following the southern Tianshan Ocean slab northward subduction beneath the Yili–Central Tianshan Block. This mechanism not only produces intense magmatism with compositional diversity but also gives rise to a local extension in the western part of Yili Block. The slab break‐off model may play an important role in the crustal growth of the CAOB in Phanerozoic time. [ABSTRACT FROM AUTHOR]

The Eastern Tianshan region is a critical segment of the Central Asian Orogenic Belt (CAOB), one of the largest Phanerozoic accretionary orogenic belts in the world. Several pulses of isotopically depleted Late Palaeozoic calc‐alkaline and high‐K calc‐alkaline granitoid magmatism are known to be associated with the collisional orogeny in the CAOB. However, no systematic studies have been conducted on the peraluminous granites that were formed during the Late Palaeozoic collisional orogeny in Eastern Tianshan. Here, we present major and trace element characteristics, whole‐rock Sr–Nd isotopes, and zircon U–Pb and Lu–Hf data from the Jing'erquanbei pluton in the eastern part of Eastern Tianshan. Zircon grains from the granite yield a weighted mean U–Pb age of 250 ± 4 Ma, which is consistent with the previously determined 40Ar–39Ar age of muscovite in the associated ore body, suggesting Late Permian magmatism. The pluton shows a wide range of Sr isotope ratios (87Sr/86Sr = 0.705777–1.308836) but depleted Nd (εNd(t) = +6.71 to +8.21) and Hf (εHf (t) = +12.6 to +14.6) isotopic values. The Nd and Hf isotopic values are also consistent with the Nd and Hf isotopic values of the Carboniferous mafic volcanics (εNd(t) = +5.50 to +9.66, εHf (t) = +6.3 to +13.2) in Eastern Tianshan. The whole‐rock Nd model age (TDM2 = 350–480 Ma) and zircon Hf model age (TDM2 = 342–451 Ma) as well as the Carboniferous inherited zircon (341 ± 5 Ma) suggest that original magma was derived from young and depleted juvenile crust source. The granite is characterized by high SiO2 (74.50%–75.80%), enriched alkali contents with high sodium values (K2O + Na2O = 5.65%–8.20%, Na2O/K2O = 1.24–2.74), concentration of peraluminous elements (Al2O3/(CaO + Na2O + K2O) [A/CNK] = 1.18–1.24), high large‐ion lithophile element content, low Nb/Ta (9.97–10.64) ratio, variable Rb/Sr (0.18–16.11) ratios, and negative Eu anomalies (Eu/Eu* = 0.05–0.81). These features suggest that some minerals, such as biotite, plagioclase, and apatite, underwent fractional crystallization during the formation and evolution of the pluton. Considering the regional magmatic activity as well as tectonic evolution, we speculate that peraluminous granites of the Huangshan–Jing'erquan area of Eastern Tianshan were generated during the postcollisional extension in the Late Permian. Dehydration and melting of the Carboniferous mafic volcanics through heat input from mafic–ultramafic magma in the Middle Permian is considered to have generated the peraluminous granites. [ABSTRACT FROM AUTHOR]