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The late Palaeozoic continental-arc magmatic rocks in the Gongzhuling area are located in the Liaoyuan Accretionary Belt. Here we present new zircon U–Pb ages, whole-rock major- and trace-element compositions, Li and zircon Hf isotopic compositions and oxygen fugacity of these rocks with an aim to constrain the lithium isotopic composition of the source region and origin of the magmas. These rocks were formed during 269–258 Ma in middle–late Permian time. The dioritic rocks were formed through mixing processes, with the mafic melts originating from a metasomatized mantle wedge and the felsic melts from the lower crust of a Neoproterozoic arc. The mantle wedge has been metasomatized by Li-rich fluids derived from subducted oceanic crust, as indicated by the δ7Li values of +0.4 ‰ to +3.5 ‰ and positive ϵHf(t) values (+0.7 to +13.1). Redox-sensitive Ce in the zircons indicates the fO2 of the magmas to be low to intermediate (FMQ−2.2 to FMQ+2.6; FMQ is the fayalite–magnetite–quartz redox buffer), precluding large-scale porphyry Cu–Mo mineralization. The middle–late Permian magmatic rocks represent the terminal magmatic record of the subduction of the Palaeo-Asian oceanic crust, meaning that the final closure of the Palaeo-Asian Ocean in the eastern Central Asian Orogenic Belt occurred at the end of the Permian Period. Recent identification of Mesoproterozoic (c. 1400 Ma) granites suggests some Palaeoproterozoic crustal fragments still exist in the Liaoyuan Accretionary Belt, but only in a small amount; therefore, it is concluded that the crustal growth of the Liaoyuan Accretionary Belt occurred mainly during the Neoproterozoic period.

We report new field observations, zircon U–Pb ages and geochemical data for the discrete members of the Zhaheba ophiolite complex in northeastern Junggar of the Central Asian Orogenic Belt (CAOB) with the aim to understand the accretion process of the eastern Junggar terrane. The zircon age data reveal that the cumulates of the Zhaheba ophiolite crystallized at ~485 Ma while the volcanic sequences erupted at ~400 Ma. Thus, the volcanic sequences are not members of the Zhaheba ophiolite. Chromian spinels from the serpentinite have comparable elemental compositions to those of spinels from MORB-type ophiolites. Similarly, the rift affinity of clinopyroxene and positive zircon ε Hf(t) (13–20) and mantle δ 18O (+5.37‰) values of the cumulates imply that the cumulates crystallized from primitive magmas derived from a depleted mantle source. Elemental and Nd isotopic compositions indicate that the basalts in the Zhaheba area were derived from partial melting of a mantle wedge metasomatized by adakitic melts and/or subduction-related fluids. The data presented in this contribution, together with previous studies, indicate that the Zhaheba–Almantai and Kelameili ophiolites were MORB-type, which implies that there were at least two mid-ocean ridges during Ordovician to early Devonian times in the Junggar Ocean. In the earlier stage, intra-oceanic subduction led to the formation of the intra-oceanic arc, and then the Kelameili ophiolite accreted to an intra-oceanic accretionary wedge. In the later stage, the Zhaheba–Almantai ophiolite accreted to the accretionary wedge along the southern margin of the Iritish suture zone during the roll-back of the subduction zone from north to south.

The timing of formation of the Hegenshan suture is crucial to understanding the evolution of the Central Asian Orogenic Belt (CAOB). Here we present a well‐dated paleomagnetic pole (103 samples from 15 sites, 36.7°N/29.2°E, A95 = 3.3°) that passed a positive fold test, a reversal test, and a conglomerate test from the ∼250 Ma upper Gunbayn Formation andesites in the southeastern Mongolia Block (MOB). The high‐quality paleomagnetic database may demonstrate that the MOB drifted rapidly southward and collided with the Xilinhot–Songliao Block between 256 and 250 Ma, resulting in the closure of the Hegenshan Ocean at ∼250 Ma. The Hegenshan suture and the Solonker suture were formed almost simultaneously and marked the final closure of the Paleo‐Asian Ocean. Plain Language Summary The Central Asian Orogenic Belt (CAOB) is the largest accretionary orogenic belt on earth since begin of the Phanerozoic. Since the Late Paleozoic, two prominent sutures, namely the Hegenshan and Solonker sutures, have played crucial roles in the tectonic evolution of the eastern CAOB, as they were associated with the closure of the Paleo‐Asian Ocean (PAO). The timing of the formation of the Hegenshan suture, however, remains ambiguous due to the lack of reliable paleomagnetic data. In this study, we present accurately dated paleomagnetic constraints on the paleogeographic position of the Mongolia Block (MOB), located on the northern side of the Hegenshan suture, at ∼250 Ma. By combining high‐quality Late Permian–Early Triassic paleomagnetic data with geological evidence, we propose a new reconstruction that suggests the near‐simultaneous closure of both the Hegenshan and Solonker oceans around 250 Ma. This significant event marks the final disappearance of the PAO and represents a fundamental stage in the establishment of the tectonic framework of the eastern CAOB at that time. Key Points We report a well‐dated ∼250 Ma paleomagnetic pole from the Mongolia Block The closure of both the Hegenshan and Solonker oceans at ∼250 Ma marked the final disappearance of the Paleo‐Asian Ocean

The Central Asian Orogenic Belt (CAOB) was formed by the aggregation and collage of numerous Paleozoic subduction‐accretion assemblages and Precambrian microcontinental blocks. However, the tectonic nature of the southeastern CAOB remains controversial, which complicates the reconstruction of the Paleo‐Asian Ocean. To address this issue, a deep seismic reflection survey was initiated across the southeastern CAOB and reveals broad gentle sub‐horizontal reflectors in the middle‐lower crust and a relatively transparent zone in the upper crust. Combining with the Precambrian geological outcrops and other geophysical features, we support a microcontinental block, the Xilinhot Block, existed in the Paleo‐Asian domain. Thus, the Paleo‐Asian Ocean was separated into two branches that underwent north‐dipping and double‐dipping oceanic plate subduction, respectively, to form the Hegenshan‐Heihe and Solonker sutures. Multiple relics beneath Hegenshan‐Heihe Suture indicate that multiple sets of unidirectional oceanic subduction‐accretion and magmatism were important mechanisms of continental growth. Plain Language Summary During the consumption of the Paleo‐Asian Ocean, a great number of Paleozoic subduction‐related accretionary complexes were developed and combined with pre‐existing Precambrian continental fragments to form the Central Asian Orogenic Belt (CAOB). However, research on the tectonic evolution of this area has been limited, and the tectonic nature of the southeastern CAOB remains controversial. A deep seismic reflection survey along the southeastern CAOB shows the crustal architecture in detail. The broad gentle sub‐horizontal reflectors and a relatively transparent zone in the profile reveal a Precambrian continental fragment existed in the North Orogenic Belt of CAOB. The Paleo‐Asian Ocean was further separated into two parts, the fossil subduction zones of which show northward and bidirectional dipping characteristics beneath the Hegenshan‐Heihe and Solonker sutures, respectively. Several relics of the unidirectional subduction beneath the Hegenshan‐Heihe Suture indicate that multiple sets of unidirectional oceanic subduction‐accretion and magmatism were important mechanisms of continental growth. Key Points A preserved microcontinental block has been revealed in the North Orogenic Belt of Central Asian Orogenic Belt The Paleo‐Asian Ocean was separated into two branches, which were closed respectively by north‐dipping and double‐dipping subduction Multiple unidirectional subduction‐accretion and oceanic magmatism may contribute to continental growth

The Central Asian Orogenic Belt (c. 1000-250 Ma) formed by accretion of island arcs, ophiolites, oceanic islands, seamounts, accretionary wedges, oceanic plateaux and microcontinents in a manner comparable with that of circum-Pacific Mesozoic-Cenozoic accretionary orogens. Palaeomagnetic and palaeofloral data indicate that early accretion (Vendian-Ordovician) took place when Baltica and Siberia were separated by a wide ocean. Island arcs and Precambrian microcontinents accreted to the active margins of the two continents or amalgamated in an oceanic setting (as in Kazakhstan) by roll-back and collision, forming a huge accretionary collage. The Palaeo-Asian Ocean closed in the Permian with formation of the Solonker suture. We evaluate contrasting tectonic models for the evolution of the orogenic belt. Current information provides little support for the main tenets of the one- or three-arc Kipchak model; current data suggest that an archipelago-type (Indonesian) model is more viable. Some diagnostic features of ridge-trench interaction are present in the Central Asian orogen (e.g. granites, adakites, boninites, near-trench magmatism, Alaskan-type mafic-ultramafic complexes, high-temperature metamorphic belts that prograde rapidly from low-grade belts, rhyolitic ash-fall tuffs). They offer a promising perspective for future investigations.

The Central Asian Orogenic Belt (CAOB) is a Phanerozoic accretionary orogen with a complex formation process. This study imaged the three‐dimensional electrical structure of the lithosphere using the magnetotelluric data collected covering the southern margin of the CAOB. The resistivity model shows alternating high and low resistivities along the southern margin of the CAOB in the north, with the low resistivities in the middle and lower crust interpreted as remnants of the subducted crust of the Paleo‐Asian Ocean (PAO). The belt‐like low‐resistivity body encased by high‐resistivity bodies on both sides is interpreted as residual back‐arc oceanic crust. The Alxa Block (AB) in the south exhibits overall high‐resistivity characteristics, but a large low‐resistivity area exists near the southeastern connection to the Ordos block. Based on the characteristics of the resistivity model, we propose that the final closure position of the PAO in the southern margin of the CAOB is the Enger Us fault zone, with a north‐south bidirectional subduction mode. The widespread low‐resistivity anomaly near the Badain Jaran fault zone is interpreted as residual subduction of the back‐arc oceanic crust. The subduction of the PAO is a typical “trench‐arc‐basin” model. The variation in the subduction angle of the PAO along the strike may indicate that the later stage of the southern margin of the CAOB was subjected to the convergence effect of northeast‐directed stress from the northeast margin of the Tibetan Plateau and the associated tectonic activities. Plain Language Summary We deployed 210 magnetotelluric (MT) stations across the central section of the Central Asian Orogenic Belt, encompassing the Alxa Block and its surrounding areas. After processing and performing a three‐dimensional inversion of the collected MT data, we constructed a 3D electrical conductivity model of the lithosphere in the study area. Integrating our findings with previous research, we inferred that the Paleo‐Asian Ocean experienced bidirectional subduction, ultimately closing along the Enger Us suture zone. Furthermore, we propose that the significant contrast in electrical conductivity between the eastern and western regions of the study area is a consequence of the uplift of the Tibetan Plateau. Key Points The bidirectional subduction of the Paleo‐Asian Ocean (PAO) culminated in its closure along the Enger Us suture zone The PAO closure is characterized by a classic oceanic‐continental subduction system with a trench‐arc‐basin structure The electrical differences from the eastern to western parts of the central Central Asian Orogenic Belt were caused by the uplift of the Tibetan Plateau

Northeast Asia is a complex tectonic collage bounded by Paleozoic–Mesozoic internal and peripheral orogens, whose distribution and continuity are obscured by later deformation and magmatic overprinting. Here we present zircon data from granites and xenoliths in the Yeongdeok area, southeastern Korea, which suggest the presence of a long-lived ( ca . 30 Myr) late Paleozoic volcanic arc system. Zircon cores yield U–Pb ages of 278–255 Ma, while rim ages cluster around 250 Ma, corresponding to the emplacement of the Yeongdeok adakite pluton and associated hydrothermal alteration. The 18 O depletion (δ 1 ⁸O = 4.7–0.6‰) observed in many zircons, along with core-to-rim decreases, is interpreted as the result of recycling of hydrothermally altered volcanic carapace material. Negative zircon ε Hf (t) values commonly observed in the xenolith-hosted zircons contrast with the consistently positive values of the host Yeongdeok pluton. These unradiogenic Hf signatures resemble those of detrital zircons from the Pyeongan Supergroup, deposited in an arc-related foreland basin. Our findings suggest a protracted late Paleozoic volcanic arc system—now largely eroded except for its plutonic roots—and, when integrated with data from the northern North China Block and Hida Belt of southwest Japan, provide new constraints on the configuration of the Central Asian Orogenic Belt.

Continental intraplate magmatism remains a fundamental challenge in Plate Tectonics. Triassic magmatism represents a critical phase in the evolution of the Central Asian Orogenic Belt and continues to provoke debate about its tectonic setting. This study presents an integrated analysis of field, petrographic, geochronologic, geochemical, and isotopic data from two newly identified Triassic granitoids in the Bogda Range: an adakitic porphyry and a low‐Sr/Y granite porphyry. Zircon U‐Pb dating yields nearly coeval crystallization ages of 221–220 Ma and 219–217 Ma, respectively. Both granitoids are characterized by high SiO2 and K2O content, low MgO (Mg#) and Ni content, and elevated K2O/Na2O and Th/Nb ratios. They have also depleted whole‐rock Sr‐Nd and zircon Hf isotopic compositions, indicative of juvenile crustal sources. The adakitic porphyry exhibits high Sr/Y and (La/Yb)N ratios, low Rb/Sr ratios, and weak Eu anomalies, suggesting derivation from garnet‐stable mafic lower crust. In contrast, the granite porphyry displays low Sr/Y and (La/Yb)N ratios, consistent with a plagioclase‐stable source. By integrating these results with regional data, we propose that the diversity of Triassic magmatism in the Eastern Tianshan is due to the reworking of juvenile and ancient crust at different depths and temperatures, resulting in arc‐like geochemical signatures. This process was associated with transcurrent tectonics and variable mantle contributions in a continental intraplate setting.

Copper and iron isotopic signatures in sulfide and silicate minerals are important genetic indicators in magmatic sulfide deposits. Kalatongke is a large‐scale magmatic Cu‐Ni sulfide deposit in the Central Asian Orogenic Belt, and one that experienced multiple stages of magmatism and contamination. It is an ideal deposit in which to study Cu‐Fe isotopic fractionation during multiple stages of magmatism and sulfide mineralization processes. The Kalatongke sulfide orebodies are hosted by three small mafic intrusions in which pyroxene and sulfides (pyrrhotite, pentlandite, and chalcopyrite) are the most common Fe‐rich minerals, and chalcopyrite is the dominant Cu‐rich mineral. Sulfide liquid and silicate melt ▵56FeSul‐Sil (0.03–0.19‰) and ▵65CuCcp‐Sil (−0.78–0.74‰) values are indicative of non‐equilibrium fractionation. Most of the Cu isotope compositions in the sulfide ores at Kalatongke can be modeled as subduction‐ metasomatized, oxidized mantle source‐derived silicate melt (initial δ57Fe = 0.15‰, δ65Cu = −0.07‰) that underwent lower crustal contamination, and then reacted with silicate melt, having an R factor of 100–1,000. Rapid silicate melt and sulfide liquid Fe isotope exchange and re‐equilibration between chalcopyrite and pyrrhotite in the massive ores is reflected in the similarity of their δ56Fe values. Sulfide in disseminated ores shows a range of Fe isotope ratios, influenced by the proportions of monosulfide solid solution (MSS) and intermediate solid solution (ISS) formed. Copper isotopes can be utilized to characterize crustal contamination and silicate melt‐sulfide liquid interaction, while the Fe isotope ratios of sulfide minerals record sulfide liquid segregation and evolution in magmatic sulfide deposits. Key Points Sulfide δ65Cu and δ56Fe signatures reflect crustal contamination, sulfide and silicate melt reactions, and sulfide liquid segregation Copper isotopes can record the source and crustal contamination, sulfide liquid and silicate melt reaction, and sulfide segregation Various range of sulfide minerals Fe isotopes influenced by the segregation of MSS and ISS and their ratios

Many orogenic belts in the world exhibit accretionary and collisional orogenic phases to varying extents. How accretion evolves into collision of the Central Asian Orogenic Belt (CAOB), the largest Phanerozoic accretionary orogenic belt, is an intriguing question. In this paper, we present new U-Pb age, geochemical and isotopic data for Permian-Triassic granitoids from middle Inner Mongolia, Northern China in the southeastern CAOB, and delineate the magmatic transition from subduction to (soft) collision. The magmatic record of soft collision is identified and characterized by thickened lower crust-derived high Sr/Y granitoids with a sub-linear distribution along the Solonker suture zone. Granitoids from Early Permian to Late Permian became more enriched in whole-rock Nd and zircon Hf isotopic compositions ( ε Nd ( t ) values from 2.4 to −19.5, ε Hf ( t ) values from 11.6 to −33.7), indicating increasing incorporation of old crust. The change in peak timing of magmatism from west (ca. 264 Ma) to east (ca. 251 Ma) along the Solonker suture zone implies “scissor-like” closure of the Paleo-Asian Ocean. Integrated with previous studies, a three-stage tectonic model from the Permian to Triassic by accretion leading to collision on the south-eastern margin of CAOB is proposed. (1) Early Permian (> ca. 285 Ma): Juvenile magmatism on an active continental margin with double-sided subduction of the Paleo-Asian Ocean; (2) Middle Permian to Middle Triassic (ca. 285–235 Ma): Magma source transition from juvenile to old crust induced by a tectonic switch from arc to “scissor-like” closure and subsequent intra-continental orogenic contraction; (3) Late Triassic (< ca. 235 Ma): A-type and alkaline magmatism in response to post-collisional extension.