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The Central Asian Orogenic Belt (CAOB) is one of the largest accretionary orogenic collages in the world with prominent juvenile crust addition, where the southernmost margin of the CAOB located is one hot topic in the international studies. The Dunhuang Block located to the south of the Beishan Orogen is a key position for outlining the tectonic framework of the south margin of the CAOB. However, at present, the tectonic attribution of the Dunhuang Block is still controversial. In this paper, we focus on the origins and protoliths of the meta‐mafic rocks from the Hongliuxia complex in the southern Dunhuang Block for determining the tectonic attribution of the Dunhuang Block. In the field, the meta‐mafic rocks are mainly exposed as tectonic blocks within the metasedimentary rocks displaying the "block‐in‐matrix" fabrics or as tectonic slices juxtaposed by faults. Geochemically, the meta‐mafic rocks could be divided into three groups based on the rare earth elements (REE) and trace elements: the group 1 samples are depleted in the LREE relative to HREE and show flat HREE patterns, similar to the mid‐oceanic ridge basalt; the group 2 samples show flat REE patterns without obvious differentiation between the LREE and HREE, like the oceanic plateau basalt; the group 3 samples are enriched in LREE relative to LREE, and have negative Nb, Ta, and Ti anomalies, similar to the island arc basalt. Conclusively, the protoliths of the meta‐mafic rocks dominantly belong to the oceanic plate components. They were metamorphosed during Early Silurian to Middle Devonian in different depths of the subduction zone documented in previous studies. So, we suggest the Hongliuxia complex is an exhumed Palaeozoic subduction–accretion complex (SAC) formed during the oceanic plate subduction. This result confirms the Palaeozoic subduction event occurred in the Dunhuang region and indicates that the Dunhuang Block is a Palaeozoic Orogen rather than a part of Precambrian continent block. Considering the regional geology context, we speculate the Dunhuang Orogen belongs to the southernmost margin of the CAOB. [ABSTRACT FROM AUTHOR]

This paper reports in situ U–Pb ages and Hf isotopic data on detrital zircons from Palaeozoic strata in central‐eastern Jilin Province, NE China, with the aim of constraining the timing of final closure of the Paleo‐Asian Ocean and the tectonic evolution of the eastern segment of the Central Asian Orogenic Belt (CAOB). Zircons from Middle to Late Permian Fanjiatun and Yangjiagou formations in central Jilin Province are characterized by four major groups of age populations (2.5–2.3 Ga, 1.9–1.7 Ga, 1.3–1.0 Ga, and Late Palaeozoic ages). The Paleo‐Mesoproterozoic and Cambrian zircons have positive εHf(t) values, suggesting that the source was mainly locally derived from the CAOB, whereas a lesser amount of Archean zircons with positive εHf(t) values, indicating that source from the North China Craton (NCC). The Phanerozoic zircons have both positive and negative εHf(t) values indicates that material from bidirectional provenances in the CAOB and the NCC. However, Late Permian Kaishantun Formation in eastern Jilin Province contain a single group of Phanerozoic zircons with positive εHf(t) values, distinct from known igneous zircons in the NCC, suggesting a local source. These observations, along with the results of previous studies on Middle–Late Permian igneous rocks in Jilin Province, indicate that the eastern segment of the Paleo‐Asian Ocean underwent the initial closure in central Jilin Province during the Middle Permian and the final closure in eastern Jilin Province in the Late Permian–Early Triassic. The detrital zircon geochronological data clearly record two stages of tectonic evolution and the scissor‐like closure model of the Paleo‐Asian Ocean in the eastern segment of the CAOB. [ABSTRACT FROM AUTHOR]

The Tianshan Belt, which lies in the southwest part of Central Asian Orogenic Belt (CAOB), is characterized by abundant ophiolites or ophiolitic mélanges, which are indicators of the existence of oceanic basin can be used for tracking the tectonic evolutionary history of the orogen. The Bindaban (BD) ophiolitic mélange is located in the Central Tianshan Belt, northwest China, which comprises mainly gabbros, diabases, basalts, basaltic lavas (greenschist), and cherts. This paper presents new zircon geochronology, whole‐rock major and trace elements, and Sr, Nd isotope data for mafic rocks in the BD ophiolitic mélanges. In the eastern part of BD ophiolitic mélanges, one normal (N)‐MORB‐type basalt has a U–Pb zircon age of 265.2 ± 1.8 Ma, and one enriched‐MORB‐type dolorite in the western part of BD ophiolitic mélanges has an age of 425.4 ± 3.9 Ma, respectively, indicating either an existing ocean basin from continental rifting to normal oceanic spreading with a long time span from late Silurian to Permain, or two separate ocean basins that formed in late Permian and late Silurian during the Paleo‐Tianshan Ocean evolution. In particular, the 265.2 ± 1.8 Ma age of N‐MORB‐type basalt from BD ophiolitic mélange suggests the youngest oceanic basin (late Permian) existed in southwest CAOB, which reveals that Paleo‐Asian Ocean might last to late Permian, therefore finally closed in or after the late Permian in the North Tianshan area. [ABSTRACT FROM AUTHOR]

The Kaiyuan tectonic mélange makes up the western part of the Kaiyuan–Yanji Accretionary Complex Belt, NE China, and there has been a long‐standing controversy about its age and tectonic setting. In this paper, we present new zircon U–Pb ages and geochemical data for the mafic rocks of the Lujiapuzi Formation in the Kaiyuan tectonic mélange, and these data provide insights into the tectonic setting during the late Paleozoic and the evolutionary history of the Paleo‐Asian Ocean in the eastern segment of the Central Asian Orogenic Belt (CAOB). SHRIMP U–Pb dating of zircons from samples of albite–actinolite schist and amphibolite yielded a crystallization age of 258 ± 5.5 Ma for the protoliths, suggesting that the protoliths formed during the late Permian. The albite–actinolite schists and amphibolites have similar geochemical characteristics, and they represent metamorphosed basaltic volcanic rocks. Major, rare earth and trace element data show that the mafic rocks have a close affinity with mid‐ocean ridge basalt. REE petrogenetic modelling indicates that the primary magma was generated through the partial melting of a mixed garnet‐ and spinel‐bearing mantle source, and assimilated crustal material and underwent crystal fractionation during ascent. The geochemical features and inherited/xenocrystic zircons in the mafic samples indicate that they formed in a tectonic setting similar to the back‐arc basin. These new findings, together with other previously published data, indicate that the Paleo‐Asian Ocean still existed in the eastern segment of the CAOB during the late Permian to Early Triassic. The Kaiyuan tectonic mélange formed during the Middle Triassic, and its formation may represent the timing of final closure of the Paleo‐Asian Ocean. [ABSTRACT FROM AUTHOR]

The Tulaergen magmatic Ni–Cu deposit is related to mafic‐ultramafic rocks of the Central Asian Orogenic Belt. The ore‐host rocks are lherzolite and websterite and the major ore types are net‐textured and sparsely disseminated ores. The disseminated ores host high‐Fo (82–85) olivine and hornblende with low‐Al contents, high‐rare earth element (REE) abundances and negative Eu anomalies. The net‐textured mineralized lherzolite contains low‐Fo (74–82) olivine and high‐Al hornblende, the latter characterized by low REE concentrations and no Eu anomaly. The contrasting composition of olivine and hornblende suggests two stages of magmatism. In situ analysis of pentlandite, chalcopyrite and pyrrhotite shows that platinum‐group elements contents in sulphides are low. Contrasting Ni, Co, Se, Ag, Cd, and Pb contents in sulphides from net‐textured and in disseminated ores also supports two pulses of magmas, each with a distinct chemical composition. High‐Mg basaltic magma characterized the first stage, followed by a second‐stage less basic magma with a high H2O content. Whole‐rock Sr and Nd isotopic signatures suggest that about 4–6% crustal materials were added to the depleted mantle source. The fractional crystallization of olivine and crustal contamination play important roles in sulphur segregation at Tulaergen based on sulphur content at sulphide saturation modelling. Injection of magma enriched in H2O further enhanced sulphide aggregation and deposit forming. It is proposed that two pulses of magma injections occurred at the Tulaergen deposit, with the products of the first pulse settling at the base, and of the second one with dense mineralization laying at the top of the deposit. [ABSTRACT FROM AUTHOR]

West Junggar is an important part of the Central Asian Orogenic Belt, which is the evolutionary product of the Palaeo‐Asian Ocean (PAO). In this area, sporadically distributed ophiolitic mélanges and associated Palaeozoic stratal succession provided research materials revealing the reduction and closure of the PAO. Based on the systematically reviewed Ordovician strata in the northern West Junggar, we find that the Lower Ordovician is mainly composed of ultramafic and mafic rocks of ophiolitic mélanges, the Middle Ordovician is made up of island arc volcanic rocks and pelagic sedimentary rocks from the ophiolitic mélanges, and the Upper Ordovician consists of coarse volcaniclastic turbidites. The geochemical characteristics of the Middle Ordovician radiolarian‐bearing siliceous rocks show that these deposits formed in a limited oceanic basin controlled by terrestrial sources, and that the basin‐filling succession began with the occurrence of the Upper Ordovician proximal turbidites. The above shows that the Ordovician PAO underwent an evolutionary process from oceanic basin to limited oceanic basin and to marginal sea in northern West Junggar, and constrains the age of the ocean–continent transformation to the Middle–Late Ordovician transition, with northern West Junggar entering the evolutionary stage of marginal sea in the Late Ordovician. [ABSTRACT FROM AUTHOR]

We undertook an integrated approach incorporating whole‐rock geochemistry and detrital zircon U‐Pb geochronology from Permian sedimentary rocks in the Solonker area of central Inner Mongolia, China with the aim of constraining the tectonic evolution of the eastern segment of the Central Asian Orogenic Belt. Geochemical analysis reveals a close relationship between the sedimentary and volcanic rock suites in the study region. Detrital zircons from seven samples collected from the Zhesi Formation yield U‐Pb ages that cluster around 309–275 Ma and 464–435 Ma, with two main age peaks of ~452 and ~288 Ma. However, additional detrital zircons with ages in the range of 2,634–543 Ma are sparse and with no obvious age peaks. The results suggest that the deposition of the Zhesi Formation occurred from the Middle to the Late Permian and from two major age provenances: the Precambrian basement of the North China Plate (~1,880 Ma and ~2,520 Ma) and the Paleozoic Southern orogenic belt along the northern margin of North China (~288 Ma and ~452 Ma). In this contribution, we suggest that the Zhesi Formation in the Solonker area formed in response to the Early to Middle Permian subduction tectonic setting of the Paleo‐Asian Ocean (PAO), probably formed in a forearc basin and that the final closure of the PAO occurred after the Late Permian. [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]

The final closure of the Junggar–Balkhash Ocean resulted in the amalgamation of the circum‐Balkash–Junggar segments of the south‐western Central Asian Orogenic Belt, but the exact timing of its closure remains uncertain. Here, we use zircon U–Pb and whole‐rock chemical data for the adakitic rocks and fractionated I‐type granitoids in the Alashankou area of the southern West Junggar terrane (WJT) to investigate their petrogenesis and tectonic implications for the closure of the Junggar–Balkhash Ocean. The adakitic rocks were emplaced at 313–295 Ma and exhibit high Sr/Y ratios of 121–229. Their low MgO contents (0.91–2.09 wt%), Co, Cr, and Ni concentrations, initial 87Sr/86Sr ratios, and high εNd(t) values, indicate an origin from partial melting of juvenile lower crust under garnet‐amphibolite‐facies conditions triggered by basaltic underplating. By comparison, the fractionated I‐type granitic plutons (283–273 Ma) are weakly peraluminous and distinctive in terms of their low MgO contents (0.31–0.39 wt%) and strongly negative Nb, Ta, P, Eu, and Ti anomalies. These features, along with their higher initial 87Sr/86Sr ratios and lower εNd(t) values, suggest derivation by partial melting of a depleted mantle source and/or of newly underplated lower crust with crustal contamination. Given the Late Carboniferous depositional hiatus and post‐orogenic strike‐slip faulting and absence of post‐Devonian ophiolites and post‐Palaeozoic magmatic events in the WJT, the widespread occurrence of Late Carboniferous to Permian compositionally diverse granitoids (including the adakitic rocks, high‐Mg dioritic rocks, and I‐ and A‐type granitoids) and coeval mafic dykes can be best explained by a post‐collisional slab breakoff model. Together with other lines of geological evidence in the circum‐Balkash–Junggar area, we propose that the Junggar–Balkhash Ocean should have been closed at the beginning of the Late Carboniferous (~320 Ma), consistent with the closure time (~325–300 Ma) for regional major ocean basins. [ABSTRACT FROM AUTHOR]

The South Tianshan Orogenic Belt (STOB) is situated in the southwest margin of the Central Asian Orogenic Belt and is characterized by the distribution of ophiolitic mélanges and metamorphic rocks. In this study, we focus on 5 ophiolitic mélanges with ocean island basalt (OIB) and aim to discuss the tectonic evolution of the South Tianshan Ocean. The Kynda, Kainar, Uchkel, Heiyingshan, and Guluogou ophiolitic mélanges in STOB mainly consist of metamorphic peridotite, gabbros, basaltic lavas (pillows), abyssal radiolarian cherts, and limestones. The basaltic rocks mainly occur as tectonic blocks within the mélanges. These basaltic rocks are characterized by LREE enrichment and HREE depletion, very weak or no Eu anomalies, and no obvious Nb, Ta, and Ti negative anomalies, positive εNd(t) values, relatively high initial 87Sr/86Sr ratios, and wide 206Pb/204Pb ratios, showing the signature of OIB. The OIB‐type rocks from Kynda, Kainar, and Guluogou are likely to be derived from garnet lherzolite by relatively high degrees of melting (10% to 20%). But the basaltic rocks of Uchkel and Heiyingshan formed at significantly lower degrees of partial melting (1% to 5%) of spinel and/or garnet lherzolite. The OIB‐type rocks in these ophiolitic mélanges are considered as accreted seamount fragments and may represent mantle plume‐related magmatism within the South Tianshan Ocean. In combination with previous work, we suggest an updated model, which is bidirectional oceanic subduction with seamounts accretion and subduction system, is suitable for Palaeozoic tectonic evolution of the South Tianshan Ocean. [ABSTRACT FROM AUTHOR]

We present zircon U–Pb and Hf isotopic and whole‐rock geochemical data for late Paleozoic igneous rocks in the central Great Xing'an Range, northeast China, to constrain the late Paleozoic amalgamation history of the united Xing'an–Erguna and Songnen–Zhangguangcai Range massifs. Based on zircon U–Pb dating, we ascertain three main stages of magmatic events: Late Devonian (381–364 Ma), early Carboniferous (360–341 Ma), and late early Carboniferous–early Permian (328–271 Ma). Late Devonian rhyolites originated from partial melting of Meso‐proterozoic accreted lower crust. The crust‐derived rhyolites and coeval mantle‐derived basalts constitute a bimodal volcanic association in the west. Early Carboniferous igneous rocks include syenogranites, monzogranites, gabbro diorites, and gabbros. The granitoids are derived from partial melting of Meso‐proterozoic accreted lower crust. The gabbros and gabbro diorites show the spatial variation in zircon εHf(t) values (−0.53 to +0.84 in the east and +12.3 to +13.5 in the west), which imply that they were mainly derived from metasomatized mantle wedge and asthenosphere mantle, respectively. These characteristics indicate that northwest‐towards high‐angle subduction of the Paleo‐Asian Ocean plate beneath the united Xing'an–Erguna Massif induced arc magmatism in the east and back‐arc magmatism (similar to back‐arc rift) in the west during the Late Devonian to early Carboniferous. Late early Carboniferous–early Permian sub‐alkaline and alkaline igneous rocks are characterized by multiple sources, such as the depleted mantle, juvenile lower crust, and thickening lower crust. Their temporal variations in geochemical characteristics imply that the central Great Xing'an Range was situated under a transitional setting from syn‐collisional to post‐collisional during the late early Carboniferous to early Permian. Using the combined insight from lithofacies palaeogeography and regional magmatisms, we suggest amalgamation of the united Xing'an–Erguna and Songnen–Zhangguangcai Range massifs occurred during the late early Carboniferous to late Carboniferous. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]