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Compressive stress generated at collision fronts can propagate over long distances, inducing deformation within the continent's interior. Nevertheless, the factors governing the partitioning of intracontinental deformation remain enigmatic. The Altai Mountains serve as a type‐example of ongoing intracontinental deformation. Here, we investigate the crustal architecture of the Chinese Altai Mountains, using receiver functions obtained from newly deployed dense seismic nodal arrays. The new seismic results reveal distinct crustal features, including (a) a negative polarity discontinuity beneath Chinese Altai Mountains, suggesting a low‐velocity layer; (b) a north‐dipping mid‐crustal structure beneath the suture zone between East Junggar and Chinese Altai, indicating underthrusting of East Junggar's lower crust beneath the Chinese Altai Mountains; (c) a double Moho structure beneath East Junggar, revealing a high‐velocity lower crustal layer. In conjunction with constraints from previous multi‐disciplinary regional studies, the double Moho structures are interpreted as mafic restite from Late Paleozoic magma underplating. The addition of mafic materials can significantly enhance the rheological strength of East Junggar's crust, causing it to function as an indenter that thrust beneath the Chinese Altai Mountains during the subsequent convergence process. As a consequence, significant deformation occurs in the Chinese Altai region, resulting in the emergence of decollements, as evident by the negative polarity discontinuity. The presence of pre‐existing decollements makes the Altai Mountains region more susceptible to deformation, thereby facilitating the concentration of intracontinental deformation. These findings illuminate the evolution history of the Chinese Altai Mountains and highlight the great impacts of ancient tectonics on intracontinental deformation partitioning. Plain Language Summary: The factors that control how deformation is distributed within mountains located within continents are still not fully understood. In this study, we focused on the Altai Mountains to bring clarity to this topic. We used a new kind of seismic data to create images of the underground structures in the East Junggar‐Altai area. By combining information from previous studies in the region, we built a picture of how this area has changed since the Late Paleozoic era. During the Late Paleozoic period, the East Junggar region's crust became stronger due to a process involving molten rock moving upward and hardening beneath it. As a result, it was pushed below the Altai Mountains in a convergence event. This convergence caused extensive changes in the Altai Mountains' crust, creating a weakened section near the surface. The crustal properties and structures formed from ancient tectonic activities during the Paleozoic era have been preserved over time. This has made the Altai Mountains particularly prone to experiencing more recent deformations within the continent. Our findings emphasize how important ancient tectonic events are in determining how deformation is spread within continents. Key Points: High‐resolution images of crustal structures of the East Junggar‐Altai area were obtained from newly deployed dense seismic arraysNew constraints have emerged in the evolutionary history of the Chinese Altai‐East Junggar regions since the Late PaleozoicInherited crustal structures and properties arose from the Paleozoic tectonics govern the partitioning of the intracontinental deformation [ABSTRACT FROM AUTHOR]

[Display omitted] • The Xilinhot 316–285 Ma granitoids were evolved from coeval calc-alkaline basaltic magma. • The Linxi 525–261 Ma granites were derived from remelting of supracrustal materials. • Bidirectional subduction of the Solonker Ocean occurred until 243 Ma. • Amalgamation along the Solonker suture occurred after 243 Ma and closed the Paleo-Asian Ocean. The closure of the Paleo-Asian Ocean resulted in formation of the Central Asian Orogenic Belt (CAOB) accompanied by considerable Phanerozoic juvenile crustal growth. As an international frontier topic, whether the Solonker suture zone is the site of final closure of the Paleo-Asian Ocean and records the terminal evolution of the CAOB in Inner Mongolia is still in controversial. This study presents the geochemistry and zircon U-Pb-Hf isotopes of granitoids along the Solonker suture zone to constrain the subduction and closure processes of the Paleo-Asian Ocean. Granitoids from the Xilinhot area in the northern accretionary zone comprise diorites and granodiorites with LA-ICPMS zircon U-Pb ages of 316 ± 2 Ma, 302 ± 2 Ma, 285 ± 2 Ma and 243 ± 4 Ma, positive εHf (t) values of +2.39 to +13.31 and T DM2 model ages of 481–1191 Ma. The ca. 316–285 Ma granitoids were formed by fractional crystallization of regional coeval calc-alkaline basaltic magma in an arc-related setting and the ca. 243 Ma granitoid was generated mainly from partial melting of dominant basaltic source rocks and minor metagraywackes in the northward subduction-related setting. The granitoids from the Linxi area in the southern accretionary zone include muscovite monzogranites and monzogranites with LA-ICPMS zircon U-Pb ages of 525 ± 6 Ma, 274 ± 2 Ma and 261 ± 4 Ma. The ca. 525 Ma muscovite monzogranites have negative zircon εHf (t) values of −19.36 to −13.61 with T DM2 model ages of 2348–2711 Ma. They were generated from partial melting of Neoarchean to Paleoproterozoic supracrustal materials. The ca. 274–261 Ma monzogranites show negative zircon εHf (t) values ranging from −10.48 to −0.66 with T DM2 model ages of 1335–1942 Ma. They were derived from remelting of Paleoproterozoic to Mesoproterozoic supracrustal materials in the southward subduction zone along the northern active margin of the North China Craton. Combining our results with existing data, we infer that the early Paleozoic southward subduction of the Paleo-Asian Ocean started before ca. 525 Ma, and the northward subduction zone lasted to ca. 243 Ma, which implies the bidirectional subduction of the ocean lasted at least until ca. 243 Ma. Our work suggests that along the Solonker suture zone, the regional amalgamation may have occurred after ca. 243 Ma, which closed the Paleo-Asian Ocean. [ABSTRACT FROM AUTHOR]

Understanding the processes involved in the transformation of juvenile basaltic oceanic arc crust into mature continental crust remains a key challenge in Earth sciences. In this contribution, we present a comprehensive synthesis of in situ zircon U Pb age and Hf O isotope data for Paleozoic intrusions within the West Junggar oceanic arc, NW China. Our study reveals four distinct pulses of magmatic activity: Early Cambrian to Early Ordovician (515 to 486 Ma); Late Ordovician to Middle Devonian (445 to 392 Ma); Early Carboniferous (343 to 310 Ma) and Late Carboniferous to Middle Permian (309 to 259 Ma). These pulses have varied spatial and temporal distributions. All magmatic rocks display consistently high zircon Hf and whole-rock Nd isotope values, but substantial variations in zircon O isotopes. There are two groups of intrusions: those with high zircon δ18O (>6.5‰) and those with mantle-like zircon δ18O (ca. 5.5‰). The high zircon δ18O intrusions are predominantly concentrated in the southern West Junggar and their Hf and Nd isotopes indicate the involvement of supracrustal material and juvenile basaltic crust in their petrogenesis. Binary mixing calculations indicate a contribution from the supracrustal rocks ranging from 10% to 50%. The intrusions with mantle-like zircon δ18O are found primarily in northern West Junggar with a small amount occurring in southern West Junggar. The intrusions record a variety of magma sources and processes as demonstrated by Hf O isotope and geochemical data. These data indicate partial melting of metasomatized depleted mantle, mixing of depleted mantle and juvenile crust, and partial melting of trapped juvenile oceanic crust or mafic lower crust. Hf model ages reveal significant crustal growth in the West Junggar, characterized by three distinct episodes of crust formation occurring at approximately 656–684 Ma, 524–536 Ma, and 441–471 Ma, involving periodic remelting of igneous material derived from a depleted mantle source. This newly-formed crust maintains a mantle-like oxygen isotope composition despite being repeatedly sampled by magmas for up to 0.26 Ga. Since the timing of crustal growth occurred independently of the major magmatic pulses, the latter reflect primarily reworking and remelting processes. Two significant episodes of magmatic activity, the late Silurian to early Devonian and the late Carboniferous to early Permian, preserve a signature of ocean ridge subduction. High-temperature magmatism during these periods promoted extensive melting of the mafic lower crust, oceanic crust, and supracrustal rocks, leading to the compositional transformation from basaltic to felsic continental crust. This comprehensive compilation provides valuable insights into granite petrogenesis, crustal evolution, and the diverse processes involved in the maturation of oceanic arc crust and its contribution to continental crust formation and evolution. [ABSTRACT FROM AUTHOR]

The closure of the Paleo-Asian Ocean (PAO) is crucial for understanding the late Paleozoic–early Mesozoic paleogeography of Proto-Asia and the tectonic configuration of NE Pangea. However, the timing and mechanism for the PAO closure and final amalgamation of the Central Asian Orogenic Belt (CAOB) remain highly controversial. Available studies argue either for a pre-Carboniferous closure or eastward, scissor-style diachronous closure from late Carboniferous to late Permian. This ambiguity is mainly caused by the different criteria applied to evaluate the final closure of oceanic basins and termination of accretionary orogenesis. Here we summarize new evidence including the youngest mélange-bearing accretionary complex and provenance change of syn-orogenic sediments in order to trace the terminal closure of the PAO from Tianshan in the west, through Beishan and Alxa, to Solonker and Changchun-Yanji in the east, a total distance of ∼5000 km. The Tianshan marks the demise of the western segment of the PAO where the Tarim Craton collided with the Kazakhstan–Yili–Central Tianshan arc. Several ophiolitic mélanges from the Kyrgyz and Chinese Tianshan show the relicts of Permian–Triassic oceanic lithosphere that amalgamated during the Middle-Late Triassic. In Beishan, three ophiolitic mélanges contain Permian igneous rocks and Permian–Triassic sedimentary matrix, suggesting closure of the ocean between ∼245–222 Ma. In the Engger Us mélange of Alxa, a turbidite matrix overlying Permian ocean plate stratigraphy yields a ∼244 Ma maximum depositional age, constraining the time of emplacement of the accretionary complex. To the east, several ophiolitic mélanges in Inner Mongolia contain Permian–Early Triassic gabbro/basalt and middle-late Permian radiolarians, suggesting subduction-accretion continued into the Early Triassic. Along the Changchun–Yanji suture in NE China, several accretionary complexes yield emplacement ages of ∼246–234 Ma. Therefore, the youngest ophiolitic mélanges and accretionary complexes across the whole southern CAOB were formed during the Middle-Late Triassic. In addition, Middle-Late Triassic provenance changes have been identified in syn-orogenic sediments in Tianshan, Beishan, Alxa, Inner Mongolia and NE China. These data are in agreement with Triassic deformation and high-pressure metamorphism, which together indicate that the western, central, and eastern segments of the PAO were closed almost contemporaneously during the Middle-Late Triassic. To the south, multidisciplinary data suggest that the amalgamation between South China, Sibumasu, Indochina, Qiangtang, and North China took place between ∼230–225 Ma, which led to the closure of the Paleo-Tethys Ocean. Taken together, the Indosinian orogeny leading to the amalgamation of the East Asian blocks marks the final assembly of Pangea. The joining of East Asia in the Late Triassic maximized the land area of Pangea, which potentially fostered the dramatic climate change and formation of the megamonsoon. • Permian–Triassic ophiolitic mélanges and accretionary complexes in the southern Central Asian Orogenic Belt are reviewed. • Contemporaneous closure of the western, central and eastern segments of the Paleo-Asian Ocean in the Middle-Late Triassic. • Middle-Late Triassic orogenesis in East Asia marks the final assembly of Pangea. [ABSTRACT FROM AUTHOR]

[Display omitted] • Systematic Sr-Nd-Hf-Pb isotopic studies on sanukitoids in northern West Junggar. • Sanukitoids were generated by subducted sediment melt–mantle mixing. • Northern West Junggar experienced an initial ridge subduction in late Carboniferous. The study of Carboniferous magmatism in northern West Junggar plays an important role in understanding the tectonic evolution of that part of the Central Asian Orogenic Belt. In this study, we present petrology, zircon U–Pb geochronology, mineral and whole-rock geochemistry, and the Sr–Nd–Hf–Pb isotope compositions of volcanic rocks from the Hamutusi area of northern West Junggar. LA–ICP–MS zircon U–Pb analysis of a representative andesite yielded an early to late Carboniferous age of 324.4 ± 6.9 Ma. The volcanic rocks are calc-alkaline, with high SiO 2 (54.2–57.8 wt%), MgO (5.97–8.33 wt%), Mg# (60–69), Cr (147–448 ppm), and Ni (29.1–120 ppm) contents, and are enriched in large ion lithophile elements (LILE) and light rare earth elements (LREE), but depleted in high field strength elements (HFSE), these characteristics are similar to those of typical sanukitoids within the Setouchi volcanic belt in Japan. All samples have radiogenic initial Sr and Pb isotopic compositions, and low ε Nd (t) and ε Hf (t) values, indicating the sanukitoids were generated by partial melting of subducting sediments in which the melts interacted with the mantle. Geochemical modeling calculations indicate a proportion of 3–10% sediment melt and slab-derived fluids were mixed with the depleted mantle to produce the bulk of the Hamutusi rocks. We conclude that the studied rocks from north West Junggar record the initiation of ridge subduction related to a transition from normal subduction to subduction of young and hot oceanic lithosphere between the early and late Carboniferous. [ABSTRACT FROM AUTHOR]

A major current debate in Asian tectonics concerns the time of closure of the Paleo‐Asian Ocean (PAO) and the collision between the Central Asian arcs and the Tarim and North China cratons (NCC). This has led to much uncertainty about the reconstruction of proto‐Asia and tectonic configuration of northeast Pangea. Here we report Triassic provenance change in the foreland of the Alxa Block by field‐based zircon U‐Pb and Hf isotopic analysis. Nonmarine sediments, unconformable on or in fault contact, with the Alxa basement yield Precambrian and Paleozoic–Triassic detrital zircon ages with maximum depositional ages of Middle‐Late Triassic (∼244–224 Ma). Hf isotopic data indicate that Middle Triassic sandstones were sourced from the NCC basement and a continental arc, whereas Late Triassic sediments received an additional input from a juvenile arc. This provenance change in the foreland sedimentation indicates that the final closure of the PAO was in the Middle‐Late Triassic. Plain Language Summary: The Central Asian Orogenic Belt, the world's largest Phanerozoic accretionary orogen, was constructed by the amalgamation of magmatic arcs and subduction‐accretion complexes during the protracted subduction of the Paleo‐Asian Ocean (PAO). The collision between Central Asian arcs and the Tarim and North China cratons led to the final closure of the PAO and formation of proto‐Asia and northeast Pangea. Constraining when and how the PAO closed is fundamental for a better understanding of the complex history of assembly of this part of Asia and the process from accretion to collision of the accretionary orogen. We conducted geological mapping and provenance analysis of a newly discovered foreland deposition on the Alxa Block in northwest China. The results reveal a provenance change in the Middle‐Late Triassic, which we interpret as a response to collision between the juvenile Central Asian arcs and the North China Craton. Our findings combined with regional data point to final closure of the PAO in the Middle‐Late Triassic. Key Points: Discovery of Triassic syn‐orogenic sediments in the foreland of the Alxa Block, northwest ChinaDetrital zircon U‐Pb and Lu‐Hf isotopic data indicate that juvenile Central Asian arc detritus arrived in the Alxa foreland by CarnianThe provenance change constrains the time of closure of the Paleo‐Asian Ocean as Middle‐Late Triassic (Ladinian‐Carnian) [ABSTRACT FROM AUTHOR]

Subduction transformation (advancing vs. retreating) may be manifested by compositional variations of arc magmas and may result in oroclinal bending. Identifying relevant chemical and physical processes is crucial for understanding accretionary orogenesis and continental crustal evolution. The Northern Yili Block (NYB) was situated on an active margin associated with subduction of the Junggar Ocean (part of the Paleo‐Asian Ocean) and underwent perplexing accretionary orogenesis in late Paleozoic. Two episodes of subduction‐related granitoid magmatism have been identified, the first in the Late Devonian (374–369 Ma) and the second in the Late Carboniferous (ca. 304 Ma). These two episodes of granitoid magmatism exhibit contrasting features; for example, the first episode shows low εNd(t) (−6 to −2) and εHf(t) (−12 to +3) values, while the second episode displays relatively higher values (−2 to +7 and 0 to +20, respectively), suggesting increase contribution of juvenile components in the magma sources. The calculated zircon saturation temperatures are mostly <800°C for the first episode but increased to >800°C for the second episode. The (La/Yb)N ratios of the two‐episode granitoids vary from 2–17 to 1–9, indicative of the NYB crustal thinning in the Late Carboniferous. In addition, the migrations of the magmatic arc and trench in the NYB took place coevally in the Late Carboniferous and were accompanied by development of an accretionary complex and an immature back‐arc basin. We interpret that the arc magmatic variations and migrations reflect geodynamic transition from the Late Devonian advancing subduction to the Late Carboniferous retreating subduction. The retreating subduction of the Junggar oceanic plate possibly resulted in prominent oroclinal bending of the southern Kazakhstan collage system in the Late Carboniferous. Key Points: Two episodes of granitoids were derived from mixed sources of the Proterozoic basement and various Paleozoic juvenile materialsThe tectonic transformation occurred in the Northern Yili Block from advancing to retreating subduction in late PaleozoicThe subduction zone transition may account for oroclinal bending in southern limb of the Kazakhstan Orocline in the Late Carboniferous [ABSTRACT FROM AUTHOR]

The temporal–spatial framework of arc amalgamation is an important key for understanding the anatomy of orogenic collages, present and past. The Junggar‐Balkhash Ocean was a major branch of the southern Paleo‐Asian Ocean where several arcs were amalgamated. Among them, the Dananhu arc with its characteristic juvenile magmatism and lack of Precambrian basement is an efficient recorder of the evolutional history. From our U–Pb and Lu–Hf isotopic analyses of Devonian to Triassic sediments in the Dananhu arc and Permian sediments in the Yamansu‐Central Tianshan arc, we discovered two major changes in detrital zircon provenance of the Dananhu arc: (a) An increasing input of Precambrian ages from the Mongolia collage at 850, 1,850, and 2,500 Ma, together with Phanerozoic zircons ranging from 420 to 480 Ma with negative εHf(t) value since ca. 288 Ma; (b) the presence of the Yamansu‐Central Tianshan arclike Precambrian age cluster of 1,400–1,600 Ma around 243 Ma. In combination with regional tectonothermal events, these two changes correspond to the formation of the Harlik‐Dananhu composite arc in the latest Carboniferous–early Permian followed by its collision with the Yamansu‐Central Tianshan arc in the latest Permian–early Triassic, which marks the termination of the eastern Junggar‐Balkash Ocean. Analysis of the sedimentary successions within the intraoceanic arcs sheds light on the amalgamation history of the Central Asian Orogenic Belt. [ABSTRACT FROM AUTHOR]

With aim of providing constraints on the Late Paleozoic tectonic evolution of the southern Central Asian Orogenic Belt (CAOB), an integrated study was conducted on the geochronological and geochemical data for dioritic, granitic and diabase dykes from the Aqishan–Yamansu belt in the eastern Tianshan, NW China. Zircon U-Pb dating indicates that the dioritic and granitic dykes were both emplaced in the Late Carboniferous (∼311 Ma and ∼315 Ma). The dioritic dykes show adakitic characteristics and have high Na 2 O and positive ε Hf (t) values (+12 to +17), which suggest an origin from partial melts of a subducted oceanic slab. The granitic dykes have high SiO 2 and K 2 O contents and are characterized by enriched light rare earth elements (LREE) and slightly flat heavy rare earth elements (HREE), with negative Eu and Nb–Ta–Ti anomalies. These dykes are alkali-calcic and show geochemical features of highly fractionated I-type granites. Their positive ε Hf (t) values (+16 to +17) suggest that they were derived from a juvenile accreted oceanic crustal source. The coeval diabase dykes have low SiO 2 and K 2 O contents but high TiO 2 , MgO and Mg# (54–59). They are enriched in LREE and show characteristics of enriched mid-ocean ridge basalts (E-MORB). The relatively high Ba/Th, slightly low Th/Ta ratios, and negative Nb-Ta anomalies imply a mantle source metasomatised by slab-derived fluids. Thus, these basic dykes were generated likely by partial melting of the upwelling asthenosphere mantle with a slight influence of slab-derived fluids. Therefore, we suggest that the formation of these Late Carboniferous dykes were triggered by a post-collisional slab breakoff and the Aqishan–Yamansu belt was a continental arc formed by south-dipping subduction of the Kangguer oceanic plate. Image 1 • Late Carboniferous dykes were identified in the Aqishan-Yamansu belt in Eastern Tianshan • The E-MORB-like diabase dykes originated from asthenosphere mantle with influence of slab-derived fluids • The adakitic dykes were formed by partial melting of subducted oceanic slab • The granitic dykes were derived from partial melts of juvenile crustal sources • Formation of these dykes were triggered by a Late Carboniferous post-collisional slab breakoff [ABSTRACT FROM AUTHOR]

[Display omitted] • Arc-like volcanic rocks emplaced at 342–337 Ma in West Junggar. • The magmas formed by hot and hydrous melting in a mantle wedge. • A transition from cold to hot subduction in southern PAO occurred in Carboniferous. The chemical evolution and pressure–temperature conditions of subduction zone magmatism along ancient suture zones in orogenic belts can provide important information regarding plate convergence processes in paleo-oceans. Carboniferous magmatism in West Junggar is key to understanding the tectonothermal and subduction history of the Junggar Ocean, which was a branch of the Paleo-Asian Ocean, as well as the accretionary processes in the southwestern Central Asian Orogenic Belt (CAOB). We undertook a geochronological, mineralogical, geochemical, and Sr–Nd–Hf–Pb isotopic study of volcanic rocks from the Baikouquan area of West Junggar. We used these data to determine the petrogenesis, mantle source, and pressure–temperature conditions of these magmas, and further constrain the subduction and tectonic history of the Junggar Ocean. The studied volcanic rocks yielded zircon U–Pb ages of 342–337 Ma and are characterized by enrichments of large-ion lithophile elements (LILEs), and depletions in high-field-strength elements (HFSEs), indicative of an island arc affinity. The volcanic rocks have positive Ɛ Nd (t) (5.83–7.04) and Ɛ Hf (t) (13.47–15.74) values, 87Sr/86Sr (t) ratios of 0.704023–0.705658, and radiogenic 207Pb/204Pb (t) and 208Pb/204Pb (t) ratios at a given 206Pb/204Pb (t) ratio, indicative of a depleted mantle source contaminated by subduction-related materials. Geochemical modeling calculations indicate that ≤1% of a subduction component comprising fluid and sediment melt could have generated the source of the parental melts of the Baikouquan volcanic rocks. Clinopyroxene phenocrysts in the volcanic rocks are classified as high- and low-Ti clinopyroxene, and pressure–temperature calculations suggest the host rocks formed at high temperatures (∼1300 °C) and shallow to moderate depths (<2 GPa). The magma was probably generated by hot and hydrous melting in a mantle wedge in response to subduction of young, hot oceanic lithosphere. The present results, combined with published data, suggest that the Baikouquan volcanic rocks record a transition in tectonic setting from normal cold to anomalous hot subduction of young oceanic lithosphere close to a mid-ocean ridge. This indicates ridge subduction began shortly after 337 Ma. Our results provide new insights into the tectonomagmatic evolution during intra-oceanic subduction prior to ridge subduction. [ABSTRACT FROM AUTHOR]

The Central Asian Orogenic Belt (CAOB) resulted from accretion during the Paleozoic subduction of the Paleo‐Asian Ocean. The Xilinhot area in Inner Mongolia is located in the northern subduction zone of the central‐eastern CAOB and outcropped a large number of late Paleozoic mafic intrusions. The characteristics of magma source and tectonic setting of the mafic intrusions and their response to the closure process of the Paleo‐Asian Ocean are still controversial. This study presents LA‐ICPMS zircon U‐Pb ages and geochemical features of mafic intrusions in the Xilinhot area to constrain the northward subduction of the Paleo‐Asian Ocean. The mafic intrusions consist of gabbro, hornblende gabbro, and diabase. Their intrusion times can be divided into three stages of 326–321 Ma, 276 Ma and 254 Ma by zircon U‐Pb ages. The first two stages of the 326–276 Ma intrusions mostly originated from subduction‐modified continental lithospheric mantle sources that underwent a variable degree partial melting (5–30%), recording the subduction of oceanic crust. The third stage of the 254 Ma mafic rocks also show arc‐related features. The primary magma compositions calculated by PRIMELT2 modeling on three samples of ∼326 Ma and two samples of ∼254 Ma show that these mafic samples are characterized by a variable range in SiO2 (47.51–51.47 wt%), Al2O3 (11.46–15.55 wt%), ΣFeO (8.27–9.61 wt%), MgO (13.01–15.18 wt%) and CaO (9.13–11.67 wt%), consisting with the features between enriched mantle and lower continental crust. The source mantle melting of mafic intrusions occurred under temperatures of 1302–1351°C and pressures of 0.92–1.30 GPa. The magmatic processes occurred near the crust‐mantle boundary at about 33–45 km underground. Combined with previous studies, it is concluded that Carboniferous to early Permian (∼326–275 Ma) northward subduction of the Paleo‐Asian oceanic crust led to the formation of the mafic magmatism in the Baolidao arc zone. The whole region had entered the collision environment at ∼254 Ma, but with subduction‐related environments locally. The final collision between the North China craton and the South Mongolian microcontinent may have lasted until ca. 230 Ma. [ABSTRACT FROM AUTHOR]

The Solonker suture zone has long been considered to mark the location of the final disappearance of the Paleo‐Asian Ocean in the eastern Central Asian Orogenic Belt (CAOB). However, the time of final suturing is still controversial with two main different proposals of late Permian to early Triassic, and late Devonian. This study reports integrated whole‐rock geochemistry and LA‐ICP‐MS zircon U‐Pb ages of sedimentary rocks from the Silurian Xuniwusu Formation, the Devonian Xilingol Complex and the Permian Zhesi Formation in the Hegenshan‐Xilinhot‐Linxi area in central Inner Mongolia, China. The depositional environment, provenance and tectonic setting of the Silurian‐Devonian and the Permian sediments are compared to constrain the tectonic evolution of the Solonker suture zone and its neighboring zones. The protoliths of the silty slates from the Xuniwusu Formation in the Baolidao zone belong to wacke and were derived from felsic igneous rocks with steady‐state weathering, poor sorting and compositional immaturity. The protoliths of metasedimentary rocks from the Xilingol Complex were wackes and litharenites and were sourced from predominantly felsic igneous rocks with variable weathering conditions and moderate sorting. The Xuniwusu Formation and Xilingol Complex samples both have two groups of detrital zircon that peak at ca. 0.9–1.0 Ga and ca. 420–440 Ma, with maximum deposition ages of late Silurian and middle Devonian age, respectively. Considering the ca. 484–383 Ma volcanic arc in the Baolidao zone, the Xuxiniwu Formation represents an oceanic trench sediment and is covered by the sedimentary rocks in the Xilingol Complex that represents a continental slope sediment in front of the arc. The middle Permian Zhesi Formation metasandstones were derived from predominantly felsic igneous rocks and are texturally immature with very low degrees of rounding and sorting, indicating short transport and rapid burial. The Zhesi Formation in the Hegenshan zone has a main zircon age peak of 302 Ma and a subordinate peak of 423 Ma and was deposited in a back‐arc basin with an early marine transgression during extension and a late marine regression during contraction. The formation also crops out locally in the Baolidao zone with a main zircon age peak of 467 Ma and a minor peak of 359 Ma, and suggests it formed as a marine transgression sedimentary sequence in a restricted extensional basin and followed by a marine regressive event. Two obvious zircon age peaks of 444 Ma and 280 Ma in the Solonker zone and 435 Ma and 274 Ma in Ondor Sum are retrieved from the Zhesi Formation. This suggests as a result of the gradual closure of the Paleo‐Asian Ocean a narrow ocean sedimentary environment with marine regressive sedimentary sequences occupied the Solonker and Ondor Sum zones during the middle Permian. A restricted ocean is suggested by the Permian strata in the Bainaimiao zone. Early Paleozoic subduction until ca. 381 Ma and renewed subduction during ca. 310–254 Ma accompanied by the opening and closure of a back‐arc basin during ca. 298–269 Ma occurred in the northern accretionary zone. In contrast, the southern accretionary zone documented early Paleozoic subduction until ca. 400 Ma and a renewed subduction during ca. 298–246 Ma. The final closure of the Paleo‐Asian ocean therefore lasted at least until the early Triassic and ended with the formation of the Solonker suture zone. [ABSTRACT FROM AUTHOR]

The Kangurtag belt in the Eastern Tianshan, connecting the Dananhu Arc with the Central Tianshan Arc, contains diagnostic rocks of accretionary origin, and thus provides key information about the evolution of the North Tianshan Ocean. The Southern Kangurtag belt is composed of two types of mélange. Type I mélange consists of Enriched Mid‐Ocean Ridge Basalt‐type pillow basalts, draped by biohermal limestones and carbonate‐siliceous sediments of a slope facies, and siliceous argillites from a hemipelagic‐pelagic environment that together make up a seamount assemblage. In Type II mélange, Normal Mid‐Ocean Ridge Basalt and ribbon cherts were dismembered and entrained in a clastic matrix, showing a "block‐in‐matrix" structure. Detrital zircons of four sandstones from Devonian and Carboniferous strata within the mélanges have a predominant age population of 410–430 Ma and a distinct Proterozoic cluster around 1.4–1.6 Ga. The εHf(t) values of Phanerozoic zircons range from −25.1 to +8.6. Such age patterns, typical of the Central Tianshan Arc, and the Hf isotopic data indicate that these sedimentary successions were deposited on the northern margin of the Central Tianshan Arc. The youngest detrital zircon age of 317 Ma provides an upper limit for the time of formation of the Southern Kangurtag accretionary complex. Therefore, we suggest that the Southern Kangurtag belt comprises an accretionary complex that developed during southward subduction of the North Tianshan Ocean beneath the Central Tianshan Arc. This subduction began in the Early Ordovician and may have lasted until the Late Carboniferous–Permian. Key Points: Two types of mélange are recognized in the Southern Kangurtag accretionary complexComposition and detrital zircon U‐Pb‐Hf isotopic data from sandstones indicate that they were deposited on the margin of the Central TianshanSouthward subduction of the North Tianshan Ocean may have lasted until the Late Carboniferous‐Permian [ABSTRACT FROM AUTHOR]

Abstract The general structure of the Chinese Altai has been traditionally regarded as being formed by five tectono-stratigraphic ' terranes ' bounded by large-scale faults. However, numerous detrital zircon studies of the Paleozoic volcano-sedimentary sequences shown that the variably metamorphosed Cambro-Ordovician sequence, known as the Habahe Group, is present at least in four ' terranes '. It structurally represents deepest rocks unconformably covered by Devonian and Carboniferous sedimentary and volcanic rocks. Calc-alkaline, mostly Devonian, granitoids that intruded all the terranes revealed their syn-subduction related setting. Geochemistry and isotope features of the syn-subduction granitoids have shown that they originated mainly from the melting of youthful sediments derived from an eroded Ordovician arc further north. In contrast, Permian alkaline granitoids, mostly located in the southern part of the Chinese Altai, reflect a post-subduction intraplate setting. The metamorphic evolution of the metasedimentary sequences shows an early MP-MT Barrovian event, followed by two Buchan events: LP-HT mid-Devonian (ca. 400–380 Ma) and UHT-HT Permian (ca. 300–270 Ma) cycles. The Barrovian metamorphism is linked to the formation of a regional sub-horizontal possibly Early Devonian fabric and the burial of the Cambro-Ordovician sequence. The Middle Devonian Buchan type event is related to intrusions of the syn-subduction granitoids during an extensional setting and followed by Late Devonian-Early Carboniferous NE-SW trending upright folding and crustal scale doming during a general NW-SE shortening, responsible for the exhumation of the hot lower crust. The last Permian deformation formed NW-SE trending upright folds and vertical zones of deformation related to the extrusion of migmatites, anatectic granitoids and granulite rocks, and to the intrusions of gabbros and granites along the southern border of the Chinese Altai. Finally, the Permo-Triassic cooling and thrust systems affected the whole mountain range from ca. 265 to 230 Ma. In conclusion, the Chinese Altai represents different crustal levels of the lower, middle and upper orogenic crust of a single Cambro-Ordovician accretionary wedge, heterogeneously affected by the Devonian polyphase metamorphism and deformation followed by the Permian tectono-thermal reworking event related to the collision with the Junggar arc. It is the interference of Devonian and Permian upright folding events that formed vertical boundaries surrounding the variously exhumed and eroded crustal segments. Consequently, these crustal segments should not be regarded as individual suspect terranes. Graphical abstract Unlabelled Image Highlights • The Altai is a Cambro-Ordovician volcano-sedimentary accretionary wedge • The Altai crust differentiated by Devonian melting and sedimentary additions • The Altai architecture results from Late Devonian to Permian deformation. [ABSTRACT FROM AUTHOR]

Abstract The architecture and mechanics of an orogen can be understood in terms of a system of collages that are characterized by a complex assemblage of multiple components, but the fundamental paleogeographic framework and the tectonic relationships between the different components are often insufficiently defined, because of unavailable data. The Central Asian Orogenic Belt (CAOB) provides an ideal opportunity to address the fundamental framework of paleogeography and tectonic relationships between the diverse and many components in this huge collage. In this paper we review several lines of available evidence, which enable us to propose a new tectonic model of huge roll-back in the formation of the accretionary tectonics of the Mongolian collage in Central Asia. In the early Paleozoic the Mongolia collage comprised the southern Siberian and the Tuva-Mongol Oroclines. The Siberia Craton and the Mongolia collage jointly formed a giant "tadpole-shape" within the Paleo-Asian and Panthanlassic oceans; its head (Siberia) was to the south, and the tail (Tuva-Mongol) to the northwest. The structures and tectonic zonation of the Mongolia collage are characteristic of multiple arcs, which have been separately described in detail in different segments southwards from the Southern Siberia-East Sayan, West Sayan-Gorny Altai-Chara, via the Lake Zone-Junggar-Tianshan, Gobi Altai-Beishan-Alxa, to the Manlay-Hegenshan-Baolidao-Solonker segments. Almost all segments underwent Early Paleozoic to Permian, or even Triassic, frontal subduction and accretion, while rifting in the Late Carboniferous to Permian or Triassic occurred in the outward/oceanward (westward) advancing Mongolian collage. Therefore, we suggest that a huge complex roll-back, active from the Carboniferous to Permian or even to late Triassic, facilitated the formation of the Mongolian collage. The outward multiple roll-back process was compatible and almost coeval with the start of the Tuva-Mongol Orocline and rotation of the Siberian Craton, as confirmed by paleomagnetic and structural data. During the roll-back processes an archipelago paleogeography was formed behind the frontal subduction and accretion, in which independent arcs or terranes were amalgamated or collided to form composite arcs or terranes either simultaneously or at slightly different times. The roll-back process was affected by the collision of the Kazakhstan collage along the Chara and Karamay zones in the Early Permian, the collision of the Tarim Craton along the South Tianshan zone in the Early Permian, the collision of the Dunhuang Block along the Liuyuan zone in the Early Permian-Triassic, the collision of the Alxa block along the Qugan Qulu zone in the Permian, and the collision of the North China Craton along the Solonker zone in the Middle-Late Triassic. The tectonic styles and architecture of accretionary orogenic belts like the CAOB are characterized both by the amalgamation of multiple terranes and by oroclinal bending. The systematic anatomy of the multiple roll-back processes and their interactions with the adjacent collages shed light on the evolving orogenic architecture and the crustal accretionary history of orogens. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Mo mineralization is hosted in the Lower Carboniferous metasedimentary rocks. • Multiple-stage hydrothermal activities are recorded in the Donggebi deposit. • The Donggebi deposit has a molybdenite Re-Os age of 234 Ma. • The porphyry Mo deposits in Eastern Tianshan were closely related to a post-collisional extensional setting. Abstract The the Donggebi porphyry Mo deposit in the eastern section of the Eastern Tianshan Orogenic Belt in the Central Asian Orogenic Belt contains Mo metal reserves of 0.5 Mt. The deposit is hosted in Early Carboniferous metasedimentary rocks, namely; metasandstone, meta-sandy mudstone. Multiple hydrothermal activities have resulted in propylitic, phyllic, and argillic alteration in this deposit. Four stages (I-IV) of hydrothermal activity are identified. Stage I is represented by a mineral assemblage of K-feldspar, quartz and wolframite. Stage II consists of quartz + magnetite+pyrite ± chalcopyrite veinlets/veins with phyllic halos. Stage III consists of quartz + molybdenite + pyrite ± galena ± sphalerite ± chalcopyrite veins that are commonly related to phyllic alteration in the altered rocks. Stage IV has an assemblage of calcite + gypsum. Molybdenite mainly occurs in Stages III. Re-Os dating results for molybdenite samples from these two stages yielded an isochron age of 234.2 ± 1.6 Ma (2σ, MSWD = 0.25, n = 8). Porphyritic granites have a SIMS U-Pb zircon age of ∼236 Ma and it was probably related to the Triassic felsic magmatism in this area. Values of δ34S of sulfides range from 1.5‰ to 3.8‰, with an average value of 2.81 ± 2.24‰ (n = 22), reflecting a deep sulfur source. Most molybdenite samples have high δ34S values (≥3.36‰) relative to other sulfide minerals (i.e., pyrite and chalcopyrite) of Stages I to III (δ34S = 1.5–3.8‰, n = 18). Based on the geological history and spatial-temporal distribution of the granitoids, it is proposed that the Mo deposits in the eastern part of the East Tianshan Orogenic Belt formed in a post-collision extensional setting in the Early Mesozoic. [ABSTRACT FROM AUTHOR]

Abstract: The timing of final subduction and closure of the Paleo‐Asian Ocean (PAO) is controversial. Located in a key position within the southern Central Asian Orogenic Belt, the Alxa Tectonic Belt (ATB) provides a crucial window to evaluate the final subduction processes of the PAO. This study presents field and geochronological data for Permian volcano‐sedimentary rocks from the southwestern ATB. Field observations revealed a syntectonic unconformity between the Middle and Upper Permian strata. Detrital zircon U‐Pb analyses show a major peak at ~273 Ma and a subordinate peak at ~440 Ma for the Middle Permian sample. The Upper Permian samples show consistently unimodal age spectra with single peaks at ~261 and ~263 Ma, respectively. The Permian zircons from the analyzed samples yield predominately positive εHf(t) values, indicating major juvenile magmatic processes mixed with limited recycled Precambrian basement. The diagnostic zircon U‐Pb‐Hf isotopic characteristics and ubiquitous intermediate and felsic volcanic detritus in these rocks indicate rapid sediments accumulation sourced from a proximal magmatic terrane in a suprasubduction zone environment. The Paleozoic zircon U‐Pb age peaks from this study are comparable to those for the Permian arc‐related sediments along the Solonker Suture Zone, thus linking the Alxa active margin with the northern margin of the North China Craton during Middle‐Late Permian times. Our study thus provides key constraints for the final subduction processes of the PAO, documented within the ATB, before the terminal amalgamation of the southern Central Asian Orogenic Belt. [ABSTRACT FROM AUTHOR]

The Beishan and East Tianshan Orogenic Collages in the southernmost Central Asian Orogenic Belt (CAOB) record the final stages of evolution of the Paleo-Asian Ocean. These collages and their constituent arcs have an important significance for resolving current controversies regarding their tectonic setting and age, consequent accretionary history of the southern CAOB, and the closure time of the Paleo-Asian Ocean. In this paper, we present our work on the southern Mazongshan arc and the northern Hongyanjing Basin in the Beishan Orogenic Collage (BOC), and our comparison with the Bogda arc and associated basins in the East Tianshan Orogenic Collage. Field relationships indicate that the Pochengshan fault defines the boundary between the arc and basin in the BOC. Volcanic rocks including basalts and rhyolites in the Mazongshan arc have bimodal calc-alkaline characteristics, an enrichment in large ion lithophile elements such as Rb, Ba, and Pb and depletion in high field-strength elements (e.g., Nb and Ta), which were probably developed in a subduction-related tectonic setting. We suggest that these bimodal calc-alkaline volcanic rocks formed in rifted arcs instead of post-orogenic rifts with mantle plume inputs. By making detailed geochemical comparisons between the Mazongshan arc and the Bogda arc to the west, we further propose that they are similar and both formed in arc rifts, and helped generate a Carboniferous archipelago of multiple arcs in the southern Paleo-Asian Ocean. These data and ideas enable us to postulate a new model for the tectonic evolution of the southern CAOB. [ABSTRACT FROM AUTHOR]

The paper reviews and integrates geological, geochronological, geochemical and isotope data from 21 intra-oceanic arcs (IOA) of the Paleo-Asian Ocean (PAO), which have been identified in the Central Asian Orogenic belt, the world largest accretionary orogeny. The data We discuss structural position of intra-oceanic arc volcanic rocks in association with back-arc terranes and accretionary complexes, major periods of intra-oceanic arc magmatism and related juvenile crustal growth, lithologies of island-arc terranes, geochemical features and typical ranges of Nd isotope values of volcanic rocks. Four groups of IOAs have been recognized: Neoproterozoic – early Cambrian, early Paleozoic, Middle Paleozoic and late Paleozoic. The Neoproterozoic – early Cambrian or Siberian Group includes eleven intra-oceanic arcs of eastern and western Tuva-Sayan (southern Siberia, Russia), northern and southwestern Mongolia and Russian Altai. The Early Paleozoic or Kazakhstan Group includes Selety-Urumbai, Bozshakol-Chingiz and Baydaulet-Aqastau arc terranes of the Kazakh Orocline. The Middle Paleozoic or Southern Group includes six arc terranes in the Tienshan orogen, Chinese Altai, East-Kazakhstan-West Junggar and southern Mongoia. Only one Late Paleozoic intra-oceanic arc has been reliably identified in the CAOB: Bogda in the Chinese Tienshan, probably due to PAO shrinking and termination. The lithologies of the modern and fossil arcs are similar, although the fossil arcs contain more calc-alkaline varieties suggesting either their more evolved character or different conditions of magma generation. Of special importance is identification of back-arc basins in old accretionary orogens, because boninites may be absent in both modern and fossil IOAs. The three typical scenarios of back-arc formation - active margin rifting, intra-oceanic arc rifting and fore-arc rifting were reconstructed in fossil intra-oceanic arcs. Some arcs might be tectonically eroded and/or directly subducted into the deep mantle. Therefore, the structural and compositional records of fossil intra-oceanic arcs in intracontinental orogens allow us to make only minimal estimations of their geometric length, life span, and crust thickness. [ABSTRACT FROM AUTHOR]

The Central Asian Orogenic Belt (CAOB) is one of the largest and most complex accretionary collages and responsible for considerable Phanerozoic juvenile crustal growth. The Xilingol Complex is a key tectonic unit within the eastern CAOB and consists of strongly deformed quartz-feldspathic gneisses with lenticular or quasi-lamellar amphibolites. Whether the complex in the belt represents Precambrian basement is controversial and here a combined analysis of petrology, geochemistry and geochronology of quartz-feldspathic gneisses from the complex is reported. The rocks belong to upper amphibolite facies and three stages of metamorphism are recognized based on mineral assemblages: prograde metamorphism (Bt-I + Ms-I + Pl + Qz + Mag), peak metamorphism (Alm + Sil + Kfs), and retrograde metamorphism (appearance of Bt-II + Ms-II). Both Precambrian and Paleozoic age populations are identified from each sample. The Precambrian zircons are sourced from magmatic rocks and the crystals display a wide range of 207 Pb/ 206 Pb ages from 3141 ± 17 Ma to 837 ± 24 Ma, and significant variation in εHf (t) values from − 17.84 to + 10.57 with T DM2 model ages from 3209 to 1389 Ma. The Paleozoic zircons have 206 Pb/ 238 U ages from 494 ± 14 Ma to 402 ± 10 Ma, variation in εHf (t) values from − 12.82 to + 7.72 and T DM2 model ages from 2252 to 960 Ma. The biotite 40 Ar- 39 Ar dating yields a plateau age of 301.2 ± 1.9 Ma with a low temperature step age 288.1 ± 1.7 Ma. The samples have a wide range of whole-rock SiO 2 (63.7–89.3%) and Al 2 O 3 contents (5.66–16.3%), with Fe 2 O 3 T varying from 0.60% to 6.06%. All of them have trace element compositions consistent with those of the upper continental crust. The protoliths of paragneisses in the Xilingol Complex are wackes and litharenites, representing a part of fore-arc sedimentary sequence ( > 319 Ma) with a major phase of diagenesis age between ca. 387 and 382 Ma in an active continental margin of the South Mongolian microcontinent. The Precambrian zircons from the complex are proposed to have been originally derived from the South Mongolian or those similar microcontinents in the CAOB. These microcontinents have been originally derived from the Tarim craton, instead of the Siberia or North China cratons or Gondwanaland. The prograde biotites from the paragneisses with ages of ca. 312–301 Ma recorded the beginning of the accretionary wedge-continent collage during the northward subduction of the Paleo-Asian Ocean, which may last to ca. 282 Ma recorded by the retrograde biotites. Detrital materials from the South Mongolian microcontinent and the Baolidao arc instead of the North China craton were deposited in the fore-arc basin indicating the presence of the Solonker zone separating the northern subduction zone from the southern subduction zone in the CAOB. The CAOB is formed as the model of multiple subduction zones with different subduction polarities. [ABSTRACT FROM AUTHOR]

The Central Asian Orogenic Belt (CAOB) formed mainly in the Paleozoic due to the closure of the Paleo-Asian oceanic basins and accompanying prolonged accretion of pelagic sediments, oceanic crust, magmatic arcs, and Precambrian terranes. The timing of subduction–accretion processes and closure of the Paleo-Asian Ocean has long been controversial and is addressed in a geochemical and isotopic investigation of mafic rocks, which can yield important insight into the geodynamics of subduction zone environments. The Xilingol Complex, located on the northern subduction–accretion zone of the CAOB, mainly comprises strongly deformed quartzo-feldspathic gneisses with intercalated lenticular or quasi-lamellar amphibolite bodies. An integrated study of the petrology, geochemistry, and geochronology of a suite of amphibolites from the complex constrains the nature of the mantle source and the tectono-metamorphic events in the belt. The protoliths of these amphibolites are gabbros and gabbroic diorites that intruded at ca. 340–321 Ma with positive εHf (t) values ranging from + 2.89 to + 12.98. Their T DM1 model ages range from 455 to 855 Ma and peak at 617 Ma, suggesting that these mafic rocks are derived from a depleted continental lithospheric mantle. The primitive magma was generated by variable degrees of partial melting of spinel-bearing peridotites. Fractionation of olivine, clinopyroxene and hornblende has played a dominant role during magma differentiation with little or no crustal contamination. The mafic rocks are derived from a Late Neoproterozoic depleted mantle source that was subsequently enriched by melts affected by slab-derived fluids and sediments, or melts with a sedimentary source rock. The Carboniferous mafic rocks in the northern accretionary zone of the CAOB record a regional extensional event after the Early Paleozoic subduction of the Paleo-Asian Ocean. Both addition of mantle-derived magmas and recycling of oceanic crust played key roles in significant Late Carboniferous (ca. 340–309 Ma) vertical crustal growth in the CAOB. Amphibolite–facies metamorphism (P = 0.34–0.52 GPa, T = 675–708 °C) affected these mafic rocks in the Xilingol Complex at ca. 306–296 Ma, which may be related to the crustal thickening by northward subduction of a forearc oceanic crust beneath the southern margin of the South Mongolian microcontinent. The final formation of the Solonker zone may have lasted until ca. 228 Ma. [ABSTRACT FROM AUTHOR]

The Beishan Orogenic Collage (BOC) is located in the southeast of the Central Asian Orogenic Belt (CAOB) and formed during final consumption of the Palaeoasian Ocean in the late Palaeozoic. This study applies low temperature thermochronology to constrain the Meso-Cenozoic history of the BOC. Apatite fission track and U–Th–Sm/He data obtained for granitoid samples along a north–south transect through the BOC indicate three distinct phases of exhumation during (1) the late Triassic–early Jurassic (~ 225–180 Ma), (2) early Cretaceous (~ 130–95 Ma) and (3) late Cretaceous–early Palaeogene (~ 75–60 Ma). Samples from the northern BOC reveal a more profound early Cretaceous signal and a weaker late Triassic–early Jurassic signal than those in the southern BOC. A possible explanation for this discrepancy is the presence of crustal-scale fault zones in the northern BOC that are interpreted to have undergone repeated reactivation throughout the Mesozoic, exposing deeper exhumed sections of the BOC. These faults may thus have acted as a major control on exhumation in the region. This pattern is consistent with results from elsewhere in the CAOB, such as in the Tianshan and the Altai, where regional widespread exhumation occurred since the early Cretaceous while major fault zones record localised exhumation during the late Cretaceous and Cenozoic. Late Cretaceous–early Palaeogene cooling ages were found only in the south of the BOC, suggesting that exhumation at that time was more localised and did not reach the northern margins of the study area. The Meso-Cenozoic cooling events described here are thought to be related to the progressive closure of the (Palaeo-)Tethys ocean to the south. Associated collision and accretion of micro-continental blocks and island–arcs at the southern Eurasian margin are interpreted to have induced more widespread reactivation and exhumation in Central Asia than previously anticipated, extending to the northern margin of the Tarim Craton. This observation hence refines the existing tectonic history models for Central Asia. [ABSTRACT FROM AUTHOR]

This article expands upon detrital zircon geochronology with a sampling and analysis strategy dating variably tectonized granitoid conglomerate clasts. Its purpose is to elucidate details of the provenance's tectonomagmatic history from deformation-relative age distributions. The method involves bulk samples of clasts, sorted based on the degree of internal ductile deformation. Isolating granitoid clasts, we divide them into three subsets: undeformed, slightly deformed, and deformed. Laser ablation, inductively coupled plasma mass spectrometry U-Pb geochronology is performed on zircon separates of each subset. Our case study, involving the Permian Hongliuhe Formation in the southern Central Asian Orogenic Belt, analyzes each of the three clast subsets, as well as sandstone detrital samples, at three stratigraphic levels and yields a profile of the unroofed provenance. Clast age distributions exhibit different, wider-age spectra than sandstone samples, an effect of proximity to the respective provenance. They indicate a minimal lag time, implying rapid exhumation rates, whereas sandstone data alone would indicate a 90 Myr lag time. Early Paleozoic arc-building episodes appear as Ordovician peaks in sandstone data and Silurian-Devonian peaks in clast data, indicating a younging of magmatism toward proximal provenance. A magmatic hiatus starts in the Devonian, correlating with the latest age of deformed clasts, interpreted as timing of collisional tectonics. The detailed age spectra provide regional tectonic context and interpretation of processes, as well as more robust provenance interpretation than could be determined from sandstone samples alone. The variably tectonized clast detrital geochronology method removes human sampling bias and the practical limits of studying regional granitoid distributions. [ABSTRACT FROM AUTHOR]

Magmatic arcs ascribed to oceanic lithosphere subduction played a dominant role in the construction of the accretionary Central Asian Orogenic Belt (CAOB). The Beishan orogenic collage, situated between the Tianshan Orogen to the west and the Inner Mongolia Orogen to the east, is a key area to understanding the subduction and accretionary processes of the southern CAOB. However, the nature of magmatic arcs in the Beishan and the correlation among different tectonic units along the southern CAOB are highly ambiguous. In order to investigate the subduction-accretion history of the Beishan and put a better spatial and temporal relationship among the tectonic belts along the southern CAOB, we carried out detailed field-based structural geology and LA-ICP-MS zircon U-Pb geochronological as well as geochemical studies along four cross-sections across crucial litho-tectonic units in the central segment of the Beishan, mainly focusing on the metamorphic assemblages and associated plutons and volcanic rocks. The results show that both the plutonic and volcanic rocks have geochemical characteristics similar to those of subduction-related rocks, which favors a volcanic arc setting. Zircons from all the plutonic rocks yield Phanerozoic ages and the plutons have crystallization ages ranging from 464 ± 2 Ma to 398 ± 3 Ma. Two volcanic-sedimentary rocks yield zircons with a wide age range from Phanerozoic to Precambrian with the youngest age peaks at 441 Ma and 446 Ma, estimated to be the time of formation of the volcanic rocks. These new results, combined with published data on ophiolitic mélanges from the central segment of the Beishan, favor a Japan-type subduction-accretion system in the Cambrian to Carboniferous in this part of the Paleo-Asian Ocean. The Xichangjing-Niujuanzi ophiolite probably represents a major suture zone separating different tectonic units across the Beishan orogenic collage, while the Xiaohuangshan-Jijitaizi ophiolitic mélange may represent a Carboniferous back-arc basin formed as a result of slab rollback ascribed to northward subduction of the Niujuanzi oceanic lithosphere. Subduction of this back-arc basin probably took place in the early Carboniferous, generating the widespread arc-related granitoids including adakitic plutons, and overlapping earlier arc assemblages. The Beishan orogenic collage is not the eastern extension of the Chinese Central Tianshan, but it was generated by the same north-dipping subduction system separated by the Xingxingxia transform fault, as revealed by available regional data. This contribution implies that in addition to fore-arc accretion, back-arc accretion ascribed to opening and closure of a back-arc basin may also have been a common process in the construction of the CAOB, resembling that of the Mesozoic-Cenozoic subduction-accretion system in the SW pacific. [ABSTRACT FROM AUTHOR]

The Palaeozoic orogenic process in the North Tianshan of the southern Central Asian Orogenic Belt is controversial. Systematic field study indicates that the ophiolitic fragments of the North Tianshan are mainly thrust slices and blocks of a late Palaeozoic accretionary complex, which was intruded by granitoids. U-Pb zircon dating of plagiogranites from the North Tianshan ophiolite yielded a mean age of 343.1 ± 2.7 Ma. These are typical oceanic plagiogranites but with a supra-subduction zone (SSZ) signature. Ophiolitic basalts display N-MORB, E-MORB, and OIB compositions. One gabbro with an age of 301.9 ± 2.2 Ma shows E-MORB geochemistry mixed with N-MORB and OIB. Some andesites show clear island arc characters indicated by enrichment of LILEs relative to HFSEs. Mean ages of 344.9 ± 4.2 and 298.7 ± 2.4 Ma were obtained for a granite porphyry and a mylonitic granite, respectively. The two granitoids display an island arc geochemical signature evidenced by enrichment of LILEs and depletion of HFSEs. Combined with an eastward migration of Late Devonian to Carboniferous arc magmatism and related Cu-Au-Mo deposits, we propose that trench retreat and slab roll-back took place during subduction of the Junggar Ocean spreading ridge beneath the North Tianshan arc, and that the accretion may have lasted into early Permian time, an important late stage of the long-lived accretionary orogenesis in the southern Central Asian Orogenic Belt. [ABSTRACT FROM AUTHOR]

The Early Permian strata of the Hongliuhe Formation are located in the Beishan orogenic collage, a tectonically significant region between the Tianshan orogen and the Southern Mongolian accretionary system, of the Central Asian Orogenic Belt (also called the Altaids). Stratigraphic reconstruction of the formation shows a general fining upwards sequence of rhythmically interbedded sandstones and siltstones with thick basal successions of conglomerates, all unconformably overlying an earlier mid-Paleozoic volcanic assemblage. The clast lithotypes of conglomerates successively change from being polymictic metamorphic tectonites at the base to a nearly monomictic granitoids mid-section, illustrating the unroofing sequence of an arc-related provenance. The intra-oceanic Gongpoquan composite arc that comprises most of the central Beishan fits the clast-lithotype profile of the conglomerates, and is the most probable provenance. The Hongliuhe Formation stratigraphy experienced a thin-skinned fold-and-thrust belt style of deformation that has a consistent southward vergence. Deformation in the lower stratigraphic levels created thrust imbrication of formation-scale blocks, each separated by steep, north-over-south brittle–ductile shear zones. The blocks are internally deformed with large-scale folding, with one significant block containing a sheath fold 15 km in breadth. The upper stratigraphic levels accommodated strain through low-angle thrust ramping, shear folding, imbricate fanning and duplexing. This indicates that the Hongliuhe Formation was syn-orogenically deposited in a progressively deepening terrestrial- to nearshore environment within the Gongpoquan composite arc. Our observations and data indicate that the basin overlies an earlier Paleozoic suture zone. This implies that the northern half of the Gongpoquan composite arc overrode the southern half in a fault system reactivation centered about this zone of weakness, and created a stratigraphic and structural response consistent with a subduction- or collision-driven fold-and-thrust belt. Its southward structural vergence is supporting evidence of a north-dipping subduction-related fault system under the northern Gongpoquan. The timing of both the genesis of the Hongliuhe Formation and this deformation event coincides with the subduction of the Liuyuan Ocean or docking of the Dunhuang block further south, at the southern margin of the Gongpoquan composite arc. [ABSTRACT FROM AUTHOR]

Abstract: The architecture of accretionary orogens is a key to understand continental growth. Here we present an overview of the orogenic components and their amalgamation in the western Central Asian Orogenic Belt (CAOB). The CAOB records the convergence and interactions among various types of orogenic components including the Japan-type, Mariana-type, and Alaska–Aleutian-type arc systems, as well as the active marginal sequences of the Siberia Craton, which incorporated wide accretionary complexes and accreted arcs and terranes. During construction of the CAOB, the Kazakhstan arc chain was characterized by multiple subduction, whereas the northern fringe of the Tarim Craton remained mostly as a passive margin. The multiple convergence and accretions among these various orogenic components generated huge orogenic collages in the late Paleozoic and even in the early Triassic, involving parallel amalgamation, circum-microcontinent amalgamation and oroclinal bending. The preservation of trapped basins played a significant role in orogenesis with some parts of the oceanic plate being subducted and others behaving as rigid units. The orogenesis in the CAOB was long-lived, lasting for more than 800m.y., involving multiple-subduction and long, continuous accretion, and featuring the complexity of accretionary orogenesis and continent growth. [Copyright &y& Elsevier]

Abstract: The southern Central Asian Orogenic Belt (CAOB) is characterized by multiple and linear accretionary orogenic collages, including Paleozoic arcs, ophiolites, and accretionay wedges. A complex history of subduction–accretion processes makes it difficult to distinguish the origin of these various terranes and reconstruct the tectonic evolution of the southern CAOB. In order to provide constraints on the accretionary history, we analyzed major and trace element compositions of Paleozoic graywackes from the Huangcaopo Group (HG) and Kubusu Group (KG) in East Junggar. The HG graywackes have relatively low Chemical Index of Alteration (CIA) values (50 to 66), suggesting a source that underwent relatively weak chemical weathering. The identical average Index of Compositional Variability (ICV) values (~1.1) for both the KG and HG samples point to an immature source for the Paleozoic graywackes in East Junggar, which is consistent with an andesitic–felsic igneous source characterized by low La/Th ratios and relatively high Hf contents. These graywackes are geochemically similar to continental island arc sediments and therefore were probably deposited at an active continental margin. U–Pb dating of detrital zircons from the lower subgroup of the HG yielded a young age peak at ~440Ma, indicating a post-Early Silurian depositional age. However, the youngest populations of detrital zircons from the KG graywackes and the upper subgroup of the HG yielded 206Pb/238U ages of ~346Ma and ~355Ma, respectively, which suggest a post-Early Carboniferous depositional age. Because of similarities of rock assemblages, these two units should be incorporated into the Early Carboniferous Nanmingshui Formation. The detrital zircon age spectrum of the Early Paleozoic HG graywackes resembles that of the Habahe sediments in the Chinese Altai, which suggests that the ocean between East Junggar and the Chinese Altai was closed before the deposition of the sediments and that the Armantai ophiolite was emplaced prior to the Early Devonian. The differences in age spectra for detrital zircons from the post-Early Carboniferous graywackes in East Junggar and the Harlik arc indicate that the emplacement of the Kalamaili ophiolite postdates the Early Carboniferous. Therefore, a long-lasting northward subduction–accretion process is suggested for the formation of East Junggar and the reconstruction of the Early Paleozoic evolution of the southern CAOB. [Copyright &y& Elsevier]

Abstract: The Alegedayi Ophiolitic Complex (AOC) was discovered in the northwestern part of Altai, Xinjiang, China. Strips of mafic rocks including gabbro, diabase, pillow basalt and pyroxenite, all deformed, mostly underwent low-grade metamorphism, are intercalated with marine-facies sedimentary strata consisting of shale, siltstone and chert. SHRIMP zircon dating of a metagabbro sample gave an age of 439±17Ma. In terms of whole-rock geochemistry, the AOC is composed of three distinct groups. Whereas the majority has transitional or enriched mid-ocean ridge basalt (T-/E-MORB) affinity, varieties with oceanic island basalt (OIB) and supra-subduction zone (SSZ) affinities were also identified. Our data show that the petrogenesis of this mafic complex involved interaction among depleted mantle, enriched component, recycled sediments, slab-derived fluid, and metasomatized mantle wedge. Taking into account the coeval adakites and high-Mg rocks to the southwest and a slightly older arc to the northeast, we suggest that the AOC reflects an intra-arc spreading event that occurred in response to an early Silurian ridge subduction which had profound effects on the tectonic evolution of the Chinese Altai. [Copyright &y& Elsevier]

• The mineral deposits in the Chinese West Tianshan can be categorized into five major types. • The Cu-Ni deposits, occurred in the South Tianshan oceanic slab beneath the YCTB. • The large volumes of granites were widely distributed in the NTAS and YCTB. The Chinese West Tianshan has a prominent position in China, with respect to mineral resources and mineral production including copper, nickel, molybdenum, iron, gold, zinc and many other mineral resources. These resources are represented by a vast array of mineral systems and deposit styles in their respective terranes spanning the Precambrian and Phanerozoic geological history. These mineral systems include VMS iron–zinc, orogenic gold, magmatic copper-nickel, porphyry copper and copper–molybdenum, and epithermal gold deposits. Some of the deposits are large and superlarge including the well-known Axi gold and Dunde iron-zinc deposits, the Zhibo, Chagangnuoer, Beizhan iron deposits, and the Katebahasu gold deposit. Apart from the above-mentioned giant deposits, several others are poorly known and/or unknown to western geoscience. The study of these mineral systems can significantly contribute to our further understanding of the metallogeny of cratons and orogenic belts, orogenic collages, and anorogenic settings. This provides additions to, and further development of, existing classifications and genetic models of mineral systems, allowing researchers to elucidate unknown or poorly studied mineral systems and formation styles found in the Chinese West Tianshan, and to discover some other important styles that appear to be missing, although they are present in other regions with similar geological and tectonic settings. Based on the study of the of the West Tianshan domain, five types of endogenous metal deposits are identified: (1) Magmatic Cu-Ni deposits; (2) Porphyry Cu-Mo deposits; (3) VMS iron deposits; (4) Epithermal Au deposits; and (5) Orogenic Au-Cu deposits. Tectonically, the development of these metal deposits was closely associated with accretionary and convergent processes that occurred in the Chinese western Tianshan collage. The formation of the deposits involved three main stages, briefly described as follows: The Jingbulake intrusion associated with the Cu-Ni deposits suggests subduction of the South Tianshan oceanic lithosphere beneath the YCTB. During the Early to Late Carboniferous, the north-dipping subduction led to the development of porphyry Cu-Au deposits, epithermal gold deposits and VMS iron deposits. In the earliest Late Carboniferous, the south Tianshan oceanic crust was probably consumed, leading to the collision between the YCTB and the Tarim Craton. The large suites of granites were widely distributed in the NTAS and YCTB, accompanied by the formation of orogenic Au-Cu deposits. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Oligocene-Pliocene sediments in north Junggar mainly sourced from North Tianshan. • Accretion of Cimmerian blocks triggered two episodes of Mesozoic cooling in Tianshan. • Onset of the modern Tianshan orogeny commenced in Late Oligocene-Early Miocene time. • Ongoing India indentation caused rapid cooling between 11–3 Ma by stress propagation. Abstract It is generally accepted that the Tianshan was reactivated repeatedly throughout Meso-Cenozoic time. However, the extent of these episodes has not been fully understood. Using a previous magnetostratigraphic baseline, this study reports a detrital zircon U–Pb and apatite fission track dating study along the ~4 km thick Cenozoic Jingou River section at the southern margin of the Junggar Basin. Our results provide direct insight into the denudation history of the bordering Tianshan Mountains and suggest that they experienced two phases of rapid cooling in the Jurassic and Cretaceous. These cooling phases are attributed to tectonic events at distant plate margins such as the Late Triassic-Cretaceous accretion of peri-Gondwanan blocks (e.g. Qiangtang and Lhasa). The detrital zircon U–Pb ages range widely from ∼58 to 3055 Ma with a majority falling between ∼58 and 600 Ma. They can be statistically separated into two primary age peaks at 300–290 Ma and 450–410 Ma, as well as two secondary peaks at 170 Ma and 850 Ma. Detrital zircon U–Pb dating results suggest that the Central Tianshan may have still shed detritus into the Junggar Basin during the Early Palaeogene. In the Late Oligocene-Early Miocene, the modern North Tianshan started to form a topographic barrier that blocked all northward rivers flowing from the Central Tianshan to the Junggar Basin. Progressive northward indentation of India into Eurasia, caused a final intense phase of cooling and denudation of the Tianshan between ∼11 and 3 Ma, leading to deposition of the Xiyu Formation, a widely distributed thick conglomerate. [ABSTRACT FROM AUTHOR]

The Beishan orogenic collage is an ideal setting for investigating the temporal and spatial relationships between extensional tectonics in the Central Asian Orogenic Belt and the rifting of Gondwana. This study presents new geochemical and geochronological data for Devonian igneous rocks and the Zhangfangshan ophiolitic mélange in the southern Beishan region. The Zhangfangshan ophiolitic mélange contains a Late Devonian gabbro block (ca. 369 Ma) with extremely depleted zircon Hf isotopic compositions (ε Hf [t] = +16.5 to +22.4). The Lucaogou diorites (ca. 367 Ma) have low MgO and compatible element contents, low Sr/Y and La/Yb ratios, and positive zircon ε Hf (t) values, indicative of derivation by dehydration melting of Mesoproterozoic mafic igneous rocks in a high-temperature and medium- to low-pressure environment. The Lucaogou K-feldspar granites (ca. 374 Ma) and Dundunshan silicic volcanic rocks (ca. 375 Ma) have A-type granite affinities, and were probably derived from magmas formed by mixing between Neoproterozoic orthogneiss-derived melts and depleted mantle-derived mafic magmas in a high-temperature shallow-crustal environment. Compiled geochronological data for subduction-related magmatism and supra-subduction zone-type ophiolites are consistent with protracted subduction–accretion until the early Carboniferous along the northern margin of the Dunhuang Block. Slab retreat in this long-lived subduction zone led to the generation of oceanic lithosphere in the southern Beishan region. Furthermore, Devonian extensional tectonics in the southern Beishan area coincided with the opening of the Paleo-Tethys Ocean, indicating that protracted subduction retreat caused the separation of the Dunhuang Block from East Gondwana. • Devonian igneous rocks were produced in an extensional setting in southern Beishan. • The slab rollback caused Devonian crustal extension in southern Beishan. • Retreating subduction caused the separation of Dunhuang Block from East Gondwana. [ABSTRACT FROM AUTHOR]

Magnesian (Mg# > 45) and/or Nb-rich (Nb > 6 ppm) dioritic-andesitic rocks have been identified in the Mayile area of southern West Junggar, Northwest China. A systematic petrological, geochronological, whole-rock geochemical, Sr–Nd–Hf isotope, and clinopyroxene chemistry study was conducted to constrain the petrogenesis, mantle source, and P–T conditions of magmas as well as the tectonomagmatic processes in the southern Paleo-Asian Ocean subduction zone. Mayile dioritic-andesitic rocks generated in the Late Carboniferous (306–312 Ma) have a high SiO 2 content (52.3–63.2 wt%) and high Mg# (46–66) as well as sanukitic-like low La N /Yb N and Sr/Y ratios. They have high Nb contents (6.27–11.6 ppm) and Nb/U (9–18) ratios and are Nb-enriched sanukitic high-Mg andesites (HMAs). Clinopyroxene thermobarometry indicates that the parental magma of the Mayile HMAs experienced a high-temperature (1137–1199 °C) and shallow-level (0.8–0.17 GPa) partial melting in a mantle wedge. They have ε Nd (t) (+5.14 to +6.42), ε Hf (t) (+8.8 to +14.4), and zircon ε Hf (t) (+9.4 to +15.8) values and a slightly high (87Sr/86Sr) t ratio ranging from 0.703214 to 0.704140 relative to normal mid-ocean ridge basalt (N-MORB). The results suggest that West Junggar was dominated by continuous records of sanukitic rocks hinting at multiple ridge subduction processes in the southern Altaids. We reconstructed the subduction history of the Junggar Ocean in the Carboniferous-Permian from these particular observations in West Junggar, and gained insight into the gradual evolution of the tectonic setting, which transitioned from normal intraoceanic subduction to hot subduction of the young oceanic lithosphere from the Early to Late Carboniferous, with subsequent ridge subduction occurring mainly in the Late Carboniferous. [Display omitted] • Mayile dioritic-andesitic rocks are Nb-enriched sanukitic high-Mg andesites. • Magma formed by a high-temperature and low-pressure partial melting. • An enriched MORB mantle component mixed with subducting sediment melts. • Southern Altaids experienced multiple ridge subductions in late Carboniferous. [ABSTRACT FROM AUTHOR]

The Beishan orogenic belt is an important tectonic unit and a suitable target to investigate and understand the Paleozoic tectonic framework of the Central Asian Orogenic Belt. Paleozoic granitic rocks are widely distributed in the area and closely related to the tungsten deposits at Hongjianbingshan, Guoqing, Yingzuihongshan and Yushan. To understand the petrogenesis of the intrusions, we performed SIMS zircon U-Pb, O and whole rock major-trace element contents and Sr-Nd isotopic analyses. Two major suites of granitic intrusions associated with tungsten mineralization have been recognized during 424–314 Ma and 286–244 Ma. The former suite shows variable Sr-Nd and O compositions (average ( 87 Sr/ 86 Sr) i = 0.7149 or 0.7034, εNd (t) = −6.3 or 7.6, T 2DM = 1.68 or 0.41 Ga, δ 18 O = 9.3 or 5.9‰) indicating an ancient crust or a juvenile lower crust origin, whereas the latter suite shows A-type affinity, and the Sr-Nd and O compositions (average ( 87 Sr/ 86 Sr) i = 0.7125, εNd (t) = −4.5, T 2DM = 1.42 Ga, δ 18 O = 6.9‰) suggest the Precambrian metasedimentary strata may have exerted a significant role in the magma source. The proposed magma sources, combined with the geochemical differences between these two suites of intrusions, indicating the Silurian-Carboniferous mineralization such as Hongjianbingshan, Guoqing and Yingzuihongshan are closely associated with subduction-accretion and generation of Gongpoquan arc-accretionary system, while the Permian mineralization including Yushan deposit are attributed to continuing accretion and subsequent post collision. These tungsten-related granitic rocks are enriched in LREE and depleted in HREE and Ba, Sr, Nb, P, Eu and Ti, suggesting they may have experienced advanced fractional crystallization. Furthermore, a spectacular tetrad effect in their REE distribution patterns has been discovered, showing the granites are highly evolved rocks with strong hydrothermal interaction. The prolonged fractional crystallization and magmatic-hydrothermal interactions have contributed to the formation of the Silurian-Permian tungsten mineralization. [ABSTRACT FROM AUTHOR]

[Display omitted] • The augen granites in the Central Tianshan were formed at early Neoproterozoic. • The granites formed in a circum-Rodinia subduction-related extensional setting. • Central Tianshan Block had a different crustal evolution with the Tarim Craton. Neoproterozoic igneous rocks associated with the assembly and configuration of the Rodinia supercontinent are widely distributed in the Central Tianshan Block, southwestern Central Asian Orogenic Belt (CAOB), northwest China. The Central Tianshan Block is an important geological unit in tectonic reconstructions of the CAOB and Rodinia. However, the early Neoproterozoic tectonic framework and evolution of the Central Tianshan Block are poorly understood. Here we present a geochronological, mineral and whole-rock geochemical, and Nd–Hf isotopic study of early Neoproterozoic augen granites from the Bingdaban area. In situ zircon U–Pb dating shows that the augen granites have crystallization ages of 1002–992 Ma. The augen granites have high SiO 2 (70.46–76.24 wt%) and K 2 O (3.36–4.96 wt%) contents, and FeOT/(FeOT + MgO) ratios (0.76–0.84), low Mg# values (29–39), slightly enriched light rare earth element patterns, enriched large-ion lithophile elements, depleted high-field-strength elements (e.g., Nb, Ta, and Ti), and high 10,000 × Ga/Al ratios (2.3–8.3) and Zr + Nb + Ce + Y contents (256–408 ppm). The augen granites have geochemical features typical of A 2 -type granites, variable εNd (t) values of –1.64 to +6.87 and Nd model ages of 1.78–1.08 Ga, and zircon εHf (t) values of −1.96 to +6.42 with Hf model ages of 1.98–1.48 Ga. These data indicate the granites had a juvenile crustal-dominated source, with subordinate input of ancient crustal components, and formed in a subduction-related extensional setting. The extension might have been related to slab break-off beneath Rodinia. The early Neoproterozoic igneous rocks in the Central Tianshan and adjacent microcontinental blocks in the southwestern CAOB formed at or near an active continental margin, possibly part of the circum-Rodinian subduction zone during or after the assembly of Rodinia. Similar Neoproterozoic magmatism in the Central Tianshan and Yili blocks suggests that they had a comparable crustal evolution and a close tectonic and paleogeographic relationship during the Neoproterozoic. However, significant age and isotopic differences characterize the Central Tianshan–Yili blocks and Tarim Craton, suggesting that the Central Tianshan–Yili blocks were not separated from the Tarim Craton during the early Neoproterozoic. [ABSTRACT FROM AUTHOR]

The Central Asian Orogenic Belt (CAOB, also known as the Altaid Tectonic Collage), one of the largest and long-lived accretionary orogens in the world, developed from ca. 600 Ma to 250 Ma by multiple accretions of terranes of different origin. Despite extensive research aimed at understanding tectonic evolution of the CAOB and the evolution of the Paleo-Asian Ocean, the subduction–accretion mechanism of the CAOB remains controversial. The West Junggar, northwestern China, is located in the southwest of the CAOB and consists of Paleozoic ophiolitic mélanges, arcs and accretionary complexes. The ophiolitic mélanges in West Junggar are generally complicated and usually consist of metamorphic peridotite (serpentinite), cumulates, gabbros, basaltic lavas (pillows), and abyssal radiolarian cherts. However, sheeted dike complexes are extremely rare and, where present, usually form small, isolated bodies. The formation age of ophiolitic mélanges in West Junggar has been determined generally as early Paleozoic except for the Darbut and Karamay ophiolitic mélanges with the age ranging from Early–Middle Devonian to Late Carboniferous. The Darbut and Karamay ophiolitic mélanges have distinct unconformable or fault contacts with Lower Devonian to Lower Carboniferous volcano-sedimentary rocks consisting mainly of sandstone, basalt, tuff and volcanic breccia. The strata deposited on the Tangbale and Mayile ophiolitic mélanges are early Paleozoic and dominated by Ordovician–Silurian volcano-sedimentary rocks. The alkaline basalts in the Tangbale, Mayile, Darbut and Karamay ophiolitic mélanges occur as tectonic blocks within the mélanges which are composed of pelagic limestones, siliceous mudstone and radiolarian chert, possessing formation characteristics of seamounts (oceanic islands/plateaus). The alkaline basalts are characterized by LREE enrichment and HREE depletion, very weak or no Eu anomalies, and no obvious Nb, Ta and Ti negative anomalies, suggesting typical OIB affinity. The OIB-type rocks in ophiolitic mélanges are considered as accreted seamount fragments in West Junggar accretionary complex, and may represent mantle transition zone plume-related magmatism within the Paleo-Asian Ocean. Therefore, we propose the following tectonic evolutionary history of the West Junggar. The seamounts formed in West Junggar as well as the Paleo-Asian Ocean at Neoproterozoic. With progressive evolution of the Paleo-Asian Ocean, subduction of the oceanic lithosphere commenced during late Cambrian to early Ordovician, resulted in the seamounts eventually accreted in the fore-arc with oceanic fragments forming the Tangbale and Mayile ophiolitic mélanges. As retreat of the subducting slab, the subduction–accretion processes may have continued in the late Paleozoic, given rise to form the Darbut and karamay ophiolitic mélange with the OIB-type rocks from seamounts. Based on our observations, and in combination with previous work, we suggest that the intra-plate magmatism in the CAOB might generally continuous during the development of the Paleo-Asian Ocean from the Late Neoproterozoic to the Mesozoic. Therefore, we present a new model that is multiple intra-oceanic subduction with seamount accretion for the CAOB, which can better explain the tectonic evolution of the CAOB. [ABSTRACT FROM AUTHOR]

The Asian interior contains the Central Asian Orogenic Belt (CAOB, the longest accretionary orogen on Earth), the largest mid-latitude desert, and the most widespread late Cenozoic airborne dust deposits (Red Clay) in the Chinese Loess Plateau. This Quaternary loess deposit is underlain by aeolian Red Clay, which has a basal age of ~7 Ma throughout most of the Loess Plateau (except for several sites with latest Oligocene age in its western margin). By integrating the most recent knowledge of the reactivation and uplift history of the CAOB and the northeastern (NE) Tibetan Plateau with the magnetostratigraphic ages of the aeolian Red Clay, we provide evidence for coeval timing between the reactivation of the CAOB-NE Tibetan Plateau and the accumulation of the Red Clay, both of which began at ∼7 Ma. We suggest that the reactivation of the CAOB and the NE Tibetan Plateau played an important role in the deposition of the Red Clay in the latest Miocene-Pliocene through its control of the production of vast amounts of silt-sized debris created by frost weathering and of the transportation by the enhanced strength of the northwesterly wind systems. Detrital zircon ages demonstrate that the source materials of the late Cenozoic Red Clay were mainly derived from a mixed provenance of enlarged alluvial fans coherently linked to the late Cenozoic uplift of the CAOB and the NE Tibetan Plateau. These relations provide the basis for understanding the connections between the deep Earth (lithosphere) and surface processes and their impact on the ecosystem in Asia. • Coeval timing between reactivation of the CAOB-NE Tibetan Plateau and accumulation of the aeolian Red Clay began at ∼7 Ma • Uplift of the CAOB-NE Tibetan Plateau generated source material for the Red Clay and intensified the NW winter monsoon • Coupling between tuplift of mountain belts and aeolian deposition offers connections of lithospheric and surface processes [ABSTRACT FROM AUTHOR]

Abstract: The eastern Tianshan district occupies the middle of the Central Asian Orogenic Belt and has great economic potential for polymetallic mineralization. More than 20 medium to large ore deposits have been discovered in this region since the late 1980s. The timing of mineralization was previously thought to be Hercynian, but, Mesozoic ages for intrusions and mineralization have been repeatedly reported in recent years. Based on geochronological data and regional geological evidence, it is suggested that the mineralization in the eastern Tianshan was formed during multiple events. The mineralization processes are related to an subduction-island arc stage (∼360–320Ma) with porphyry-type and volcano-sedimentary copper deposits, a collisional-accretionary stage (∼300–280Ma) with orogenic-type gold deposits, a post-collisional-extension stage (∼280–245Ma) with mafic–ultramafic copper–nickel and epithermal gold deposits, and an intracontinental extensional stage (∼240–220Ma) that gave rise to the Jinwuozi gold deposit, Xiaobaishitou skarn W–Mo deposit and Baishan porphyry Mo–Re deposit. [Copyright &y& Elsevier]

The Permian magmatism in the Alxa region provides critical geological evidence to constrain the geodynamic processes in the southern Central Asian Orogenic Belt. The Shouji batholith is located in the southern Langshan, eastern Alxa region, and contains monzogranites, K-feldspar granites, and gabbros. New zircon U Pb age data show that the Shouji batholith formed at 282–268 Ma. The Shouji granites have high (Na 2 O + K 2 O), Nb, and Zr contents, and high 10000∗Ga/Al, FeO T /(FeO T + MgO), Yb/Nb, and Yb/Ta ratios, similar to the values of A 2 -type granites. The Shouij granites exhibit enrichment in light rare earth elements (LREE) and large ion lithophile elements (LILE); depletion in Nb, Ti, and Sr; and enriched isotopic compositions. These Shouji granites were generated by partial melting of dehydrated tonalite–trondhjemite–granodiorite rocks of the Diebusige Complex in the lower crust. The Shouji gabbros are sodium-rich and low-K calc-alkaline rocks. They are enriched in LREE and LILE, depleted in high field strength elements, and have enriched isotopic compositions. These Shouji gabbros were generated by partial melting of a lithospheric mantle source metasomatized by melts derived from an ancient continental crust in an active continental margin. Roll-back of the Enger Us subducting slab accounts for generations of the Shouji A 2 -type granites and gabbros. The zircon U Pb ages of Carboniferous–Permian magmatism show a younging trend toward the northwest in the southern Alxa region. Evidence from late Paleozoic magmatism and arc-derived sediments indicates that the southern Alxa switched from an active continental margin to an intra-oceanic arc during the early Carboniferous–Late Permian as a result of retreat of the subducting Enger Us slab. • Permian association of A 2 -type granites and gabbros are identified in the Langshan. • Permian magmatism resulted from a slab rollback in an active continental margin. • An active continental margin switched to an intra-oceanic arc in the southern Alxa. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The CAMD is one of the most important porphyry-type deposit domains on earth. • CAMD porphyry deposits are associated with the evolution of three Paleo-oceans. • MASH and slab melting models can explain the genesis of some PCDs in the CAMD. • A new model involves 'enriched lower crust and relictic oceanic ridge subduction' • Melting of juvenile lower crust was essential for Mo mineralization. Abstract A series of porphyry-type Cu-(Mo)-(Au) deposits including some giant world-class deposits such as Kounrad, Aktogai, Kal'makyr, Oyu Tolgoi and Chalukou occur in the Central Asian metallogenic domain (CAMD). The outline of the CAMD almost overlaps with that of the Central Asian orogenic belt (CAOB), which is located between the East Europe, Siberia, Tarim and North China cratons. The CAMD comprises sparsely exposed tectonic slices of Precambrian high-grade metamorphic basement rocks that are sandwiched between Phanerozoic accretionary complexes and arc rocks. According to geological, metallogenic, geochronological and tectonic setting characteristics, the CAMD comprises three metallogenic provinces: (1) the Kazakhstan Cu-Au-Mo, (2) the Mongolia Cu-Au and (3) the Northeast China Mo-Cu metallogenic provinces. Early Paleozoic (∼490 to 440 Ma) and Late Paleozoic (∼330 to 295 Ma) large scale porphyry-type mineralization in the Kazakhstan metallogenic province is intimately associated with the evolution of the Central Tianshan–Yili–Northern Tianshan–Kokchetav–Chingiz Paleozoic arc system which was terminated by the late Permian closure of the western segment of the Paleo-Asian Ocean. In contrast, the ∼370 Ma and ∼240 Ma porphyry-type mineralization of the Mongolia metallogenic province is related to the Tuva–Mongolia arc collage system that was formed during the evolution of the Paleo-Asian Ocean in the Paleozoic and the Mongol–Okhotsk Ocean in the early Mesozoic. Furthermore, the Northeast China metallogenic province was affected by three distinct geodynamic processes that were associated with the Paleo-Asian, Mongol–Okhotsk and Paleo-Pacific Oceans during the Paleozoic (>250 Ma), the early Mesozoic (>200 Ma) and the late Mesozoic (200–90 Ma), respectively. Except for the Early Paleozoic Cu mineralization at Duobaoshan (∼480 Ma) and Bainaimiao (440 Ma), the porphyry-type mineralization of this metallogenic province is predominantly characterized by widespread Mesozoic Mo mineralization. In general, porphyry-type deposits of the CAMD have geological, structural, metallogenic, alteration and fluid characteristics, which are consistent either with those related to the oceanic subductional arc settings of the Circum-Pacific metallogenic domain or with those of the continental collisional environment in the Tethyan metallogenic domain. The involvement of highly oxidized intermediate to felsic magmas is fundamental for the formation of porphyry deposits. Even though the prevalent MASH and slab melting models can be employed to interpret the genesis of some porphyry Cu deposits in the CAMD, a here newly suggested model, which is based on 'pre-enriched mafic lower crust and the subduction of a relictic mid-oceanic ridge', is thought to explain the large scale copper mineralization in the Balkhash–West Junggar metallogenic belt of the Kazakhstan metallogenic province. Nevertheless, most of the porphyritic suites associated with the Mo deposits in the Northeast China metallogenic province have relatively depleted mantle-like neodymium and hafnium isotopic compositions, suggesting that the ore-forming granitic magma may have predominantly been derived from juvenile lower crust. Upwelling of asthenosphere may have triggered the melting of the lower crust during post-collisional extension subsequent to the closure of the Paleo-Asian Ocean in the Triassic, the subduction of the Paleo-Pacific ocean in the Jurassic and the thinning of the lithosphere caused by rollback of the Paleo-Pacific plate in the Cretaceous. Ancient crustal components were only locally found to have been involved in the magma source of several medium-large Mo deposits. [ABSTRACT FROM AUTHOR]

Abstract Geological evolution of the Eastern Tianshan in the Late Paleozoic is significant to understanding the multiple accretions and final formation of the southern Central Asian Orogenic Belt. Here, we report new whole-rock geochemical and Sr–Nd isotopic data, and in situ zircon U–Pb ages for three typical A-type granitic intrusions (syenogranite, K-feldspar granite and monzonitic granite) and one dioritic pluton in the central Eastern Tianshan, NW China, in order to constrain their petrogenesis, tectonic setting and geodynamic evolution. Zircon LA-ICP-MS U–Pb ages indicate that the syenogranites and K-feldspar granites were both formed during a short time interval in the Early Permian (284–286 Ma), whereas the diorites were crystallized at 293 ± 6 Ma. The monzonitic granites were generated at 307 ± 3 Ma, earlier than the other two granitic intrusions. The three kinds of granites (syenogranite, K-feldspar granite and monzonitic granite) have high HFSE, HREE and Y/Nb ratios (1.68–2.84), and remarkably low Sr and Ba contents, with the absence of aluminium-rich minerals and show metaluminous to weakly peraluminous natures, indicating geochemical characteristics of aluminous A 2 -type granites. These granites show negative ε Nd (t) (−3.32 to −4.40) values and Mesoproterozoic two stage Nd model ages (T DM 2 = 1.36 to 1.43 Ga), which suggest a relatively old crustal source for these rocks. The Sr–Nd isotopic compositions imply that the Mesoproterozoic metamorphic basement of the Central Tianshan Block can be considered as a potential magmatic source for these aluminous A 2 -type granites. In addition, they have geochemical characteristics similar to the experimental melt that was derived from partial melting of crustal metaigneous rocks at the depth of middle to lower crust levels. Therefore, the granites were most likely produced by partial melting of metaigneous rocks in a post-collisional extensional setting. The diorites have low SiO 2 and high MgO, with uniform (87Sr/86Sr) i values (~0.7055), negative ε Nd (t) values (−4.11 to −4.59) and Mesoproterozoic two stage Nd model ages (T DM 2 = 1.41 to 1.45 Ga). They have higher Ti/Zr (42.8–46.7) and Ti/Y (280–359) ratios than continental crust and show negative Nb-Ta-Ti anomalies, which can be explained by partial melting of a relatively fertile mantle modified by old crustal materials of the Central Tianshan Block. The formation of the dioritic pluton was induced by an upwelling asthenosphere in an extensional geodynamic setting. Based on the zircon saturation temperatures of these A-type granites and the distribution of Late Carboniferous to Early Permian mantle-derived intrusions, a slab breakoff model is suggested to interpret the formation of the studied A-type granites and diorites. We infer that the slab breakoff was initiated in the Late Carboniferous and ended in the Early Permian. Highlights • Early Permian A2-type granites were identified in the Central Tianshan Block. • The Early Permian diorites were produced by partial melting of a fertile mantle. • These rocks were formed in a post-collisional extensional geodynamic setting. • The extension setting was triggered by a Late Carboniferous-Early Permian slab breakoff. [ABSTRACT FROM AUTHOR]

The Chinese Tianshan is located in the south of the Central Asian Orogenic Belt and formed during final consumption of the Paleo-Asian Ocean in the late Palaeozoic. In order to further elucidate the tectonic evolution of the Chinese Tianshan, we have established the temperature-time history of granitic rocks from the Chinese Tianshan through a multi-chronological approach that includes U/Pb (zircon), 40 Ar/ 39 Ar (biotite and K-feldspar), and (U-Th)/He (zircon and apatite) dating. Our data show that the central Tianshan experienced accelerated cooling during the late Carboniferous- to early Permian. Multiple sequences of complex multiple accretionary, subduction and collisional events could have induced the cooling in the Tianshan Orogenic Belt. The new 40 Ar/ 39 Ar and (U-Th)/He data, in combination with thermal history modeling results, reveal that several tectonic reactivation and exhumation episodes affected the Chinese central Tianshan during middle Triassic (245–210 Ma), early Cretaceous (140–100 Ma), late Oligocene-early Miocene (35–20 Ma) and late Miocene (12–9 Ma). The middle Triassic cooling dates was only found in the central Tianshan. Strong uplift and deformation in the Chinese Tianshan has been limited and localized. It have been concentrated in around major fault zone and the foreland thrust belt since the early Cretaceous. The middle Triassic and early Cretaceous exhumation is interpreted as distal effects of the Cimmerian collisions (i.e. the Qiangtang and Kunlun-Qaidam collision and Lhasa-Qiangtang collision) at the southern Eurasian margin. The Cenozoic reactivation and exhumation is interpreted as a far field response to the India-Eurasia collision and represents the beginning of modern mountain building and denudation in the Chinese Tianshan. [ABSTRACT FROM AUTHOR]

The Central Asian Orogenic Belt is a gigantic tectonic collage of numerous accreted terranes. However, its geodynamic evolution has been hotly debated primarily due to incomplete knowledge on the nature of these enigmatic terranes. This work presents new detrital zircon U–Pb and Hf isotopic data to constrain the crustal nature and origin of the Russian Altai, a critical segment of Altai-Mongolian terrane. The youngest zircon 206 Pb/ 238 U ages of 470 Ma constrain that the Terekta Formation, previously envisaged as Precambrian basement, was actually deposited after the Middle Ordovician. As for the three more sedimentary sequences above the Terekta Formation, they have youngest zircon 206 Pb/ 238 U ages of 425 Ma, 440 Ma and 380 Ma, respectively, indicating their depositions likely in the Late Silurian to Devonian. From all analyses, it is noted that many zircon U–Pb ages cluster at ca. 520 Ma and ca. 800 Ma, and these zircons display oscillatory zoning and have subhedral to euhedral morphology, which, collectively, suggests that adjacent Neoproterozoic to Paleozoic igneous rocks were possibly dominant in the sedimentary provenance. Additionally, a few rounded Archean to Mesoproterozoic zircon grains are characterized by complex texture, which are interpreted as recycling materials probably derived from the Tuva–Mongolian microcontinent. Precambrian rocks have not been identified in the Russian Altai, Chinese Altai and Mongolian Altai so far, therefore, Precambrian basement may not exist in the Altai-Mongolian terrane, but this terrane probably represents a large subduction–accretion complex built on the margin of the Tuva–Mongolian microcontinent in the Early Paleozoic. Multiple episodes of ridge–trench interaction may have caused inputs of mantle-derived magmas to trigger partial melting of the newly accreted crustal materials, which contributed to the accretionary complex. During accretionary orogenesis of the CAOB, formation of such subduction–accretion complex is likely ubiquitous, indicating continental crust growth by both lateral accumulation and vertical basaltic injection. [ABSTRACT FROM AUTHOR]

The Hongliuhe ophiolite is a fragment of the early Paleozoic oceanic crust situated in a suture zone central to the Beishan orogenic collage, which is a subset to the Central Asian Orogenic Belt in Northwest China. It has lithologic, geochemical and chronological similarities to the Yueyashan–Xichangjing ophiolite 400 km east, along strike, allowing for correlative interpretations of marginal seafloor spreading processes. The Hongliuhe ophiolite is explored in this study with complete petrologic, geochemical and structural descriptions. The ultramafic body comprises cumulate-layered lherzolite and gabbro plutonic lithologies, tectonized with syn-magmatic extension. A U–Pb age of 520.3 ± 5.8 Ma was obtained by SHRIMP analysis of zircons from a pegmatitic gabbro. The ultramafic rocks are variably depleted and some show refertilization of LILE’s consistent with slab dehydration in a supra-subduction mantle wedge. Mineral chemistry shows high Cr# (36–82) populations of spinel, and wide-ranging lower Mg# (8–50), consistent with known forearc peridotite chemistry partially re-equilibrated by tectonism or through staged magmatism. Olivine and pyroxene chemistries are consistent with this interpretation. A thin volcanic cover is interlayered with red cherts, and has a bimodal set of geochemical signatures, both island-arc tholeiite and calc-alkaline. They bear distinct Nb–Ta anomalies consistent with slab-derived fluid initiated melting in a supra-subduction environment. Coarse volcaniclastic turbidites infilled paleo-topography along the ophiolite, and they are interbedded with quartzofeldspathic sandstones, indicating an initial proximity to an arc. The sandstones contain detrital spinel with analyses showing relation to both the ophiolite and possibly a secondary alkalic volcanic source. The supracrustal sequence continues with a thick, contiguous covering of margin-related rocks, including interlayered limestone, pyroclastic and siliciclastic rocks, and basalts. As a constraint on emplacement we provide an U–Pb Zircon SHRIMP date (413.6 ± 3.5 Ma) from an undeformed granitoid body intruded within the overlying stratigraphy. The entire analysis paints a picture of subduction rollback-related extension affecting the margin of an emerging or mature arc just prior to a known magmatic cycle that ended with a collision in the Devonian at the latest. This suture is one of many in the Beishan, and our interpretation provides evidence in a long running debate supporting accretionary orogenesis in an island-arc archipelago as the main system for growing sialic crust in the Paleozoic central Asia. [ABSTRACT FROM AUTHOR]

The South Tianshan Belt has recorded the evolution of the south branches of the Paleo-Asian Ocean and is pivotal for understanding the formation of the southernmost part of the Central Asian Orogenic Belt. In order to place constraints on the tectonic evolution of the South Tianshan Ocean, three highly deformed granitic plutons (monzonitic granites, biotite K-feldspar granites and two-mica granites) exposed in the Kumishi area were collected for geochronological and geochemical studies. Zircon LA-ICP-MS U–Pb dating of the gneissic granites from the three plutons yielded crystallization ages at 446.2 ± 2.2 Ma, 431.0 ± 2.8 Ma and 407.3 ± 3.1 Ma. All of these gneissic granites have geochemical characteristics of calc-alkaline igneous rocks. The biotite monzonitic granites (446 Ma) are slightly peraluminous, LREE-enriched and show relatively flat HREE patterns mostly with negative Eu anomalies. The rocks have positive Pb and negative Nb, Ta, Ti anomalies. In combination with their negative ε Hf ( t ) values (−7.9 to −11.6) and the corresponding old T DM c ages (1.93–2.16 Ga), we suggest that the monzonitic granites were mainly derived from partial melting of the middle-lower crust dominated by Precambrian basement rocks. The biotite K-feldspar granites (431 Ma) are characterized by high K 2 O, low Fe 2 O 3 and MgO contents. They show REE patterns similar to the monzonitic granites, as well as the Nb, Ta, Ti depletions, but have more enrichment in U, Pb, Zr, and Hf. Their depleted ε Hf ( t ) values (+0.7 to +5.4) and young T DM c ages (1.07–1.37 Ga) imply significant input of mantle-derived juvenile materials, and thus suggest that the K-feldspar granites were possibly derived from a K-enriched crustal source mixed significantly with mantle-derived juvenile materials. The two-mica granites (407 Ma) show a typical S-type granite affinity with high Al 2 O 3 /TiO 2 , low CaO/Na 2 O and K 2 O/Al 2 O 3 ratios, suggesting a pelitic source. These characteristics, together with their positive ε Hf ( t ) values (−0.2 to +3.1) and relatively young T DM c ages (1.20–1.41 Ga), indicate that the two-mica granites were most likely generated by partial melting of a pelitic source with less input of juvenile materials. All of the samples from the three plutons show same geochemical characteristics of felsic magmatic rocks formed in an arc-related tectonic setting. Together with the northward thrusting tectonics and the arc magmatic rocks exposed along the South Nalati–Kawablak Fault, a northward subduction of the South Tianshan Ocean is suggested to interpret the formation of the three granitic plutons. Taking into account the distinct tectonic polarity and distribution of magmatic rocks in the western and eastern South Tianshan Belt, we suggest that the South Tianshan Ocean probably underwent different subduction processes in its western and eastern parts. A single northward subduction and a divergent bidirectional subduction are further proposed to interpret the formation of the western and eastern South Tianshan Belt, respectively. [ABSTRACT FROM AUTHOR]