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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 (εNd(t) values from 2.4 to −19.5, εHf(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. [ABSTRACT FROM AUTHOR]

This paper provides newly found and profound insight into the initiation mechanism of the first Baige landslide occurred on the upper reaches of the Jinsha River in October 10, 2018. The detailed geological characteristics are interpreted by comprehensive field surveys in the past year, which indicate that the Baige landslide developed in the Jinsha River tectonic suture zone, and the active tectogenesis significantly contributes to broken stratigraphic structures and complex spatial distribution of lithologies. The initiation is considered to be long-term creep under the exogenic and endogenic integration, while the active tectogenesis and the influence of serpentinite and foliation, respectively, are the primary exogenic and endogenic factors. In addition, this creep process can be analyzed within three stages: evolution and formation of failure-prone geological structures, progressive deformation and fracturing, and shear failure of the locking section. The distribution and easily degraded behavior of the serpentinite are the fundamental, enabling the formation of failure-prone structures and also responsible for the subsequent deformation evolution. The foliation controls the toppling deformation-failure mode and direction. Furthermore, this catastrophic landslide further reminds us to pay attention to the landslides along the upper reaches of the Jinsha River, and our preliminary results indicate that the distribution characteristics of landslides significantly depend on the Jinsha River tectonic suture zone and the serpentinite mélange belt and thus are always associated with tectonically induced damage. [ABSTRACT FROM AUTHOR]

Several Palaeozoic ophiolitic mélanges distributed in the West Junggar, Xinjiang, are remnants of the Paleo‐Asian Ocean evolution. They are important keys for studying the component, tectonic evolution, and crust–mantle interaction of the Central Asian Orogenic Belt (CAOB). This paper presents petrology, zircon U‐Pb chronology, geochemistry, and Hf isotope data of mafic rocks from the Dalabute ophiolitic mélange, West Junggar. The zircon U‐Pb chronology data of gabbro in the Dalabute ophiolitic mélange can be divided into two groups. The first group magmatic zircons yield a weighted mean age of 389.7 ± 7.7 Ma. It suggests that gabbros of the Dalabute ophiolitic mélange were formed during the period of Early‐middle Devonian, which represents the main period that the Dalabute back‐arc ocean basin expanded. The second group inherited zircons with ages ranging from 910 to 975 Ma were interpreted as Neoproterozoic materials of basement entered its magmatic source. Geochemical characteristics show that the mafic rocks from the Dalabute ophiolitic mélange can be subdivided into alkaline and tholeiite series. Whole‐rock and Hf isotopic data indicate that alkaline basalts have the signatures of typical OIB and formed in the oceanic island or seamount settings related to mantle plume, which were most likely derived from an enriched mantle source. Besides, tholeiitic rocks exhibit the features of MORB and generated in an immature back‐arc basin in the supra‐subduction zone. Their magmas originated from a depleted mantle that had been metasomatized by subduction‐related fluids and contaminated by materials with crustal nature. Therefore, Dalabute ophiolites are supposed to be generated from a back‐arc oceanic basin, which is relate to intra‐subduction and with mantle plumes developed within it. These results jointly provide convincing evidence for the evolution and property of the Dalabute ophiolite in the West Junggar and further supply reference and base for reconstruct the evolutionary history of the CAOB. [ABSTRACT FROM AUTHOR]

As one of the largest Phanerozoic orogens in the world, the Central Asian Orogenic Belt (CAOB) is a natural laboratory for studies of continental dynamics and metallogenesis. This paper summarizes the research progresses of the accretionary processes and metallogenesis of the CAOB since the People's Republic of China was founded, and puts forward the prospect for future research. During the early period (1950s–1970s), several geological theories were applied to explain the geological evolution of Central Asia. In the early period of China's reform and opening-up, the plate tectonics theory was applied to explain the evolution of the northern Xinjiang and Xingmeng regions, and the opinion of subduction-collision between Siberian, Kazakhstan, and China-North Korea-Tarim plates was proposed. The idea of the Solonker-Yanbian suture zone was established. In the 1990s, the study of the CAOB entered a period of rapid development. One school of scholars including geologists from the former Soviet Union proposed a multi-block collision model for the assemblage of the CAOB. In contrast, another school of scholars, led by a Turkish geologist, Celal Şengör, proposed that the Altaids was formed through the growth and strike-slip duplicates of a single island arc, and pointed out that the Altaids is a special type of collisional orogen. During this period, Chinese geologists carried out a lot of pioneering researches on ophiolites and high-pressure metamorphic rocks in northern China, and confirmed the main suture zones accordingly. In 1999, the concept of "Central Asian metallogenic domain" was proposed, and it became one of the three major metallogenic domains in the world. Since the 21st century, given the importance for understanding continental accretion and metallogenic mechanism, the CAOB has become the international academic forefront. China has laid out a series of scientific research projects in Central Asia. A large number of important scientific research achievements have been spawned, including the tectonic attribution of micro-continents, timing and tectonic settings of ophiolites, magmatic arcs, identification and anatomy of accretionary wedges, regional metamorphism-deformation, (ultra)high-pressure metamorphism, ridge subduction, plume-plate interaction, archipelagic paleogeography and spatio-temporal framework of multiple accretionary orogeny, continental growth, accretionary metallogenesis, structural superposition and transformation, etc. These achievements have made important international influences. There still exist the following aspects that need further study: (1) Early evolution history and subduction initiation of the Paleo-Asian Ocean; (2) The accretionary mechanism of the extroversion Paleo-Asian Ocean; (3) The properties of the mantle of the Paleo-Asian Ocean and their spatiotemporal distribution; (4) The interaction between the Paleo-Asian Ocean and the Tethys Ocean; (5) Phanerozoic continental growth mechanism and its global comparison; (6) Accretionary metallogenic mechanism of the Central Asian metallogenic domain; and (7) Continental transformation mechanism. [ABSTRACT FROM AUTHOR]

• Two phases of deformation occured in the south of the Shangdan suture zone across the Mianyuzui ductile strike-slip fault. • The metamorphic temperature of the early stage of shearing deformation is ∼ 600-700℃ and ∼ 300-500℃ for the late stage. • The subduction of the Shangdan Oceanic lithosphere was active till the Early Silurian, and subsequent collisions occurred during the Late Silurian. The Shangdan suture zone (SDSZ) subdivides the Qinling Orogenic Belt into North Qinling and South Qinling belts, marking the main tectonic boundary between the North China and South China Blocks. The Mianyuzi ductile strike-slip fault (MYZF) within the SDSZ separates the North China Block from the South China Block and contains valuable collisional information. This paper integrates the structural and geochronological data of the MYZF to investigate the Paleozoic tectonic evolution of the Qinling Orogenic Belt and the collision between the North China and South China Blocks. Two phases of deformation (D 1 -D 2a-b) are identified along the southern boundary of the SDSZ. The metamorphic temperature of mylonites is ∼ 600–700 ℃ for the early stage and ∼ 300–500 ℃ for the late stage of shearing deformation. U-Pb zircon analysis of the mylonites and diabase dike in the ductile shear reveals that zircons have major younger protolith populations at 480–460 Ma, 450–430 Ma, and 405–425 Ma, which suggests that rocks were probably derived from the North Qinling belt. The metamorphism and deformation cooling age from the MYZF have been constrained to be 339–328 Ma and 259 ± 1.6 Ma using U-Pb and 40Ar/39Ar dating. Combined with previously published data, we concluded that the subduction of the Shangdan Ocean was active until the Early Silurian and subsequent collisions occurred during the Late Silurian. Meanwhile, the shearing might have been related to the intraplate extension-exhumation during the Carboniferous-Late Permian in the Qinling Orogenic Belt. [ABSTRACT FROM AUTHOR]

The Hegenshan–Heihe Suture (HHS) is an important suture zone between the Xing'an and Songliao–Xilinhot blocks in the eastern Central Asian Orogenic Belt (CAOB). Many studies have examined the northern and southern parts of this suture zone, but the middle segment remains under-researched and controversial. This paper presents new research into Permian felsic rocks along the middle segment of the HHS, including alkaline granites, rhyolites, and granodiorites. Zircon U–Pb dating of these rocks yielded precise Permian ages of 300.4 ± 2.5, 292.8 ± 2.7, and 293.1 ± 2.2 Ma. The alkaline granites and the rhyolites are A-type rocks that were derived from lower crustal protoliths, with the melting of these protoliths caused by asthenospheric upwelling associated with lithospheric delamination. In comparison, the granodiorites are I-type granites were generated from a mantle-derived magmatic source. The petrogenesis of these granites also involved the assimilation of sedimentary rocks and fractional crystallization. This Permian magmatism occurred during post-collisional extension following the amalgamation of the Xing'an and Songliao–Xilinhot blocks. [ABSTRACT FROM AUTHOR]

The nature of source rocks and the pressure-temperature-hydration (P-T-H2O) condition are the two main factors that control the geochemical properties of granites. Therefore, the evolution of P-T-H2O conditions can be used to deduce the tectonic setting of granites. In this paper, we report on three Paleozoic granite plutons along the Shangdan suture that revealed increasing melting temperature and decreasing pressure from 437 to 403 Ma, suggesting a crustal thinning process. The Tieyupu granodiorites (437 ± 4 Ma) display Na-rich adakite affinity, i.e., SiO2 = 69.1-70.1 wt%, Na2O/K2O = 1.9-2.26, positive zircon εHf(t) values (+4.29 to +12.04), and high Sr/Y (137-160) and Y/Yb (9.89-10.25) ratios, implying a garnet-rich residue in their source. In combination with moderate zircon saturation temperatures (814-822 °C), we infer that the Tieyupu granodiorites were formed by melting of Neoproterozoic metabasites under high-pressure (>1.5 GPa) and moderate-temperature (HP-MT) conditions. The Liangchahe granodiorites (415 ± 8 Ma) also display Na-rich adakite affinity, i.e., higher Na2O/K2O (2.16-3.11) and lower Sr/Y (77-88) ratios, and higher zircon saturation temperatures (854-874 °C), and they are interpreted to have been derived from melting of metabasites under moderate-pressure (>1.0 GPa) and high-temperature (MP-HT) conditions. Their variable zircon εHf(t) values (-14.97 to +9.80) and the existence of zircon xenocrysts suggest that the primitive adakitic melts were assimilated by evolved crustal components. The Yaogou monzogranites (403 ± 4 Ma) have the highest K2O/Na2O (0.81-1.00) ratios and total rare earth element (ΣREE; 105-191 ppm) contents, lowest Sr/Y (14-43) ratios, positive zircon εHf(t) values (+6.79 to +12.22), and highest zircon saturation temperatures (891-973 °C), showing they were formed by high-temperature melting of intermediate rocks under low-pressure conditions (<1.0 GPa). The evolution of P-T conditions revealed by these three granites suggests that crustal growth and differentiation were related to gradual extensional and melting of mafic protoliths in the orogenic belt. [ABSTRACT FROM AUTHOR]

The Proterozoic geological records in eastern South China preserve a history linked to the Columbia and Rodinia supercontinent cycles and provide key constraints in understanding the geodynamic evolution of East Asia. However, it is uncertain if SW Hainan, Yangtze and Cathaysia were located in the interior or periphery of the Precambrian supercontinents, how they were connected prior to the formation of a united South China, whether the early Neoproterozoic Proto-Huanan subduction was long- or short-lived, and how and when Yangtze and Cathaysia were assembled along the Jiangnan Orogen. This paper provides an overview of key geological observations for the eastern Yangtze and Cathaysia with respect to Proterozoic tectonics. Our synthesis shows that the SW Hainan in the Mesoproterozoic (ca. 1.45 Ga) developed in a non-orogenic rift setting in the interior of Columbia. SW Hainan, together with SW Yangtze, drifted to the margin of Rodinia by ∼1.05 Ga. Furthermore, SW Hainan might have been part of the Mesoproterozoic Albany Fraser Orogen at ca. 1.30–1.05 Ga. Cathaysia and eastern Yangtze display distinct geological signatures in the early Neoproterozoic and Cathaysia remain separated from Yangtze until at least ca. 1.0 Ga. The ca. 1.0–0.9 Ga felsic igneous rocks in Cathaysia to the east of the Jiangshan-Shaoxing suture zone are mostly characterized by negative ε Hf (t) values, and distinct from those in the coeval Shuangxiwu arc to the west of the Jiangshan-Shaoxing suture zone, which have positive ε Hf (t) values. Igneous rocks dated at ca. 870–830 Ma (mainly ca. 850–830 Ma) are extensive in the Huaiyu and Jiangnan Orogen but poorly developed in Cathaysia. Neoproterozoic sedimentary rocks of Cathaysia contain abundant ca. 980 Ma detrital grains but only minor ca. 860–830 Ma grains. In contrast, in the Jiangnan and Huaiyu, the sedimentary rocks contain a dominant ca. 860–830 Ma detrital zircon age-peak but ca. 980 Ma grains are scare. Rift-related bi-model igneous rocks, ranging in age from ca. 810 Ma to ca. 750 Ma, represented by the Banxi, Likou and Mamianshan groups and their equivalents, are extensively developed in Cathaysia and Huaiyu, and the Jiangnan Orogen. These rift-related successions are separated from the Cangshuipu and Luojiamen conglomerates across an angular unconformity, which are in turn unconformable on the Lengjiaxi and Xikou groups. It is herein proposed that an early Neoproterozoic (ca. 1.0–0.9 Ga) accretionary orogen developed within the Cathaysia and lay along strike from the synchronous Eastern Ghats Orogen of India. A long-lived Neoproterozoic (ca. 0.97–0.83 Ga) Proto-Huanan arc-trench system resulted in the development of the ca. 0.98–0.88 Ga Shuangxiwu intra-oceanic arc, ca. 0.87–0.83 Huaiyu continental arc and ca. 0.87–0.83 Jiangnan intra-continental back- arc basin in response to the ongoing westward-subduction beneath the eastern Yangtze. At ca. 0.87 Ga, the arc-trench system switched from an intra-oceanic to a continental Andean margin setting. Such a system might be compatible to the NW India South Delhi Orogen at the periphery of Rodinia. Our synthesis shows that the united proto-South China was finally created by the ca. 830–810 Ma assemblage of the Yangtze with Cathaysia along the Jiangnan Orogen and was followed by the post-orogenic rifting due to the breakup of Rodinia. [ABSTRACT FROM AUTHOR]

The Central Asian Orogenic Belt (CAOB) was generated through multiple collisional and accretionary events in the Paleo-Asian Ocean, a major global ocean that existed from the late Neoproterozoic into the late Paleozoic. Nevertheless, the question of when the Paleo-Asian Ocean finally closed has notoriously been enigmatic, especially due to the absence of large-scale investigations. The South Tianshan-Solonker Suture, is the largest and southernmost suture within the CAOB, and records the ultimate collision between the Tarim-North China cratons with the Siberia craton, and is commonly interpreted as marking the eventual closure of the Paleo-Asian Ocean. In this paper, we synthesize and evaluate relevant Chinese papers on the area, which are not readily available to an international audience, and extend this across the full length of the suture zone. Based on this review, we can divide the suture zone into four distinct segments, which are, from west to east: the South Tianshan Belt, the Beishan Belt, the Solonker Belt and the Yanji Belt. This enables us to provide a more systematic understanding of the nature and development of the South Tianshan-Solonker suture. Geochronological data from Paleozoic cover rocks and high-pressure metamorphic rocks show that during the late Carboniferous, the western section of the Paleo-Asian Ocean closed when the Tarim Craton moved northward to collide with the Kazakhstan-Yili Block, thus marking the initial development of the South Tianshan Belt. The Beishan Belt to the east formed when the Dunhuang-Alxa blocks were transported northward to collide with the Tuva-Mongolia Block, with the youngest zircon U Pb data from ophiolites indicating that closure of the local Beishan Ocean was in the early-middle Permian, although its final closure may not have been until the early late Permian along the northern margin of the Alxa Block, thus making it slightly younger than the South Tianshan Belt. Further to the east, the available petrographic, geochronological and paleontological data from the Solonker Belt indicate that this belt was formed in the middle-late Permian, during which time bi-directional subduction occurred and the North China and Siberia cratons were amalgamated during an 'Appalachian-type' orogeny. Furthermore, we observe that a transition in polarity from northward to bi-directional subduction occurred along the boundary between the Beishan and Solonker belts, which may be related to the East Gobi Transform Fault. In contrast, under the influence of the westward subduction of the Paleo-Pacific Ocean, the Jiamusi-Khanka Block moved southwestward along the Yilan-Yitong Fault in the middle-late Triassic (230–220 Ma) to amalgamate with the North China Craton. The formation of the South Tianshan-Solonker Suture can be characterized by four distinct west-to-east accretion/collision events that lasted from the late Carboniferous to the late Permian. The South Tianshan Belt, the Beishan Belt and the Solonker Belt therefore demarcate, respectively, the amalgamation between the Tarim Craton and the Kazakhstan-Yili Block, the Dunhuang-Alxa Block and the Tuva-Mongolia Block, and the North China Craton with the Siberia Craton, representing the final closure of the Paleo-Asian Ocean. During the middle-late Triassic, the Yanji Belt in the far east was influenced by the Paleo-Pacific tectonic domain as a result of amalgamation between the Jiamusi-Khanka Block and the North China Craton. • South Tianshan-Solonker Suture marks the final collision between Tarim-North China and Siberian cratons. • The Suture includes four segments, and closed form Late Carboniferous to Middle Triassic from west to east, respectively. • The Yanji belt was influenced by the Paleo-Pacific tectonic domain during the Middle Triassic. [ABSTRACT FROM AUTHOR]

[Display omitted] • Depleted continental mantles occur with different mineral chemistry and occurrence. • Mafic dikes were formed from melts via low-degree melting of asthenosphere mantles. • Orthopyroxenites were formed from reaction between SiO 2 -rich melts and peridotites. • Ophiolites were formed in a continental margin that was related to the Meso-Tethys. Whether the ophiolites in the southeast margin of the Gaoligong tectonic belt are related to subduction or rift is hotly debated. The aim of this paper is to present the geological and geochemical data of these ophiolitic blocks in order to understand the significance of these in the tectonic evolution of the Meso–Tethys. The peridotites in the ophiolites are dominantly harzburgites with high Mg# (88.7–92.2) and low Al 2 O 3 (<0.8 wt%) and CaO (<0.5 wt%) contents, and display U-shape chondrite-normalized rare-earth element patterns. However, they show two different groups of mineral chemistries and occurrences. Group I are with olivine Fo 90.6–92.3, orthopyroxene Mg# 91.0–92.6, clinopyroxene Mg# 91.1–93.3, and spinel Cr# 42.1–67.4 and Mg# 62.8–71.6. They exhumed adiabatically and were intruded by mafic dikes from the melts through low-degree melting of asthenospheric mantles and by orthopyroxenites in the Early Jurassic. Group II are with olivine Fo 89.8–95.3, orthopyroxene Mg# 91.3–94.6, and spinel Cr# 62.4–94.1 and Mg# 19.5–51.0. They underwent brittle deformation and medium- to low-temperature fluid replacement. The two group's peridotites have experienced the similar partial melting degrees and are the fragments of subcontinental lithospheric mantles. Extensive continental affinity tholeiites erupted in the Middle Jurassic, coeval with the primary spreading time of the Bangonghu–Nujiang Ocean in the central Tibet. The peridotites, mafic rocks, and marine-facies sediments represent the opening products of the Meso–Tethys in the Jurassic as ophiolites in a continental margin. [ABSTRACT FROM AUTHOR]

The Late Palaeozoic Solonker‐Xar Moron‐Changchun‐Yanji Suture (SXCYS) is considered to mark the location of the final closure of the Paleo‐Asian Ocean, which separated the North China Craton to the south and the amalgamated blocks to the north in Northeast China. There has always been controversy about its eastern extension in Northeast China and the final closure time of the Paleo‐Asian Ocean. To explore this issue, we collected gabbro and quartz‐diorite samples in the Hunchun area for the genesis of mafic magma and age dating, and five groups of Permian to Triassic sandstones belonging to both sides of the potential suture locations in the middle and east Jilin Province for the provenance analysis to discuss the final closure time of the Paleo‐Asian Ocean and the possible positions of the eastward termination of the SXCYS. The gabbro reveals a Middle Permian concordia average age of 266.9 ± 5.2 Ma, and the quartz diorite reveals a Late Permian Concordia average age of 258.8 ± 4.8 Ma. Lithological and geochemical analysis reveal the two rock samples belong to low‐K arc tholeiites from the oceanic island and calk‐alkaline volcanics from the active continental margin, respectively, which implies that during the middle to late Permian, the SW margin of the Jiamusi–Khanka Block (JB) continuously experienced the subduction process from the Paleo‐Asian Ocean Plate. The final closure time of the Paleo‐Asian Ocean should be later than the Late Permian. Meanwhile, four groups of sandstone from the east Jilin reveal typically Jiamusi–Mongolia Block (JMB) provenance features, with age components of ~500 Ma, ~0.9–1.5 Ga implying that the Wangqing, Hunchun, Kaishantun area belongs to the northern part of the SXCYS from late Early Permian to Middle Triassic, with youngest age components of 288.2 ± 2.8, 275.5 ± 1.8, 250 ± 1.7, and 244.9 ± 1.7 Ma, respectively. The late Early Permian sandstone from the middle Jilin reveals the youngest age component of 273.8 ± 3.4 Ma and the age component of 487 ± 3 Ma also revealing JMB feature. Comparing to previous studies, we propose that the Paleo‐Asian Ocean finally closed during Middle to Late Triassic. A possible ENE fault separates the eastern extension of SXCYS into two parts, which means the possible position of the eastward extension of the SXCYS should go along the Wangqing‐Kaishantun with NNW direction in the west, Hunchun‐Laoheishan with NW direction in the east. [ABSTRACT FROM AUTHOR]

Northeast (NE) China is located in the eastern Central Asian Orogenic Belt (CAOB) and evolved from the amalgamation of several microcontinental blocks, which, from west to east, include the Erguna, Xing'an, Songliao, and Jiamusi-Khanka blocks. Since the Paleozoic, NE China has undergone multiple stages of subduction–accretion and tectonic destruction under the tectonic domains of the Paleo-Asian Ocean, Panthalassa, and the Paleo-Pacific Ocean. This complexity has resulted in uncertainty surrounding the amalgamation processes of the various microcontinents. Fortunately, several suture zones in NE China, including the Toudaoqiao–Xinlin Suture, the Hegenshan–Heihe Suture, the Solonker–Xar Moron–Changchun Suture, and the Jilin–Heilongjiang High-pressure Belt contain information that provides key constraints on the tectonic evolution of NE China. This paper reviews the spatial distribution, composition, and formation ages of these suture zones based on published geological records. Our temporal and spatial analyses of these suture zones enable the evolution of NE China to be assigned to those three tectonic domains: (1) In the earliest of these, the Paleo-Asian Ocean tectonic domain (650–250 Ma), the Erguna Block amalgamated with the Xing'an Block along the Toudaoqiao–Xinlin Suture during the Late Cambrian (ca. 500 Ma); the Erguna–Xing'an Block then collided with the Songliao Block along the Hegenshan–Heihe Suture during the Late Carboniferous (ca. 300 Ma), whilst the combined Erguna–Xing'an–Songliao Block amalgamated with the North China Craton along the Solonker–Xar Moron–Changchun Suture at the End-Permian (ca. 250 Ma). (2) in the Panthalassa tectonic domain (315–230 Ma), the subduction of Panthalassa (or locally, the Mongol-Okhotsk Ocean) was initiated in the eastern Jiamusi-Khanka Block during the Late Carboniferous (ca. 315 Ma), resulting in back-arc extension in the western Jiamusi-Khanka Block, which evolved into the Heilongjiang Ocean separating the Jiamusi-Khanka and Songliao blocks during the Late Permian to Late Triassic (260–230 Ma). (3) in the Paleo-Pacific Ocean tectonic domain (230–130 Ma), the first stage of westward subduction of the Paleo-Pacific oceanic plate occurred during the Late Triassic (ca. 230 Ma), causing the Jiamusi-Khanka Block to amalgamate with the North China Craton during the Late Triassic (ca. 230 Ma) and subsequently with the Songliao Block during the Late Triassic to Early Jurassic (210–180 Ma), forming the Jilin–Heilongjiang High-pressure Belt, whereas the second stage of subduction induced the emplacement of the Nadanhada Terrane during the Early Cretaceous (ca. 130 Ma). This represented the final assembly of NE China in the eastern CAOB. • NE China can be divided into three tectonic domains of the Paleo-Asian Ocean, the Panthalassa, and the Paleo-Pacific Ocean. • The assembly of NE China was accomplished through the generation of five suture zones, which formed from ∼500 Ma to ∼130 Ma. • NE China recorded multiple stages of activity of the Paleo-Asian, Panthalassa (Mongol-Okhotsk), and the Paleo-Pacific oceans. [ABSTRACT FROM AUTHOR]

The South China Craton formed after collision between the Yangtze and Cathaysia Blocks. The suture zone between these two blocks is the crux of understanding the geological evolution of South China. Due to the relative paucity of high-resolution subsurface data, the location of the suture zone in the southwestern region remains uncertain. To find the suture zone, we created a high-resolution model of the crust and upper mantle structure using 27 months of continuous waveform data acquired from 457 stations in South China. The model uses extracted phase velocity dispersion curves of Rayleigh waves at 4–40 s from ambient noise cross-correlation functions, to perform a direct inversion for an azimuthal anisotropic V SV model. In the crust a prominent belt of strong azimuthal anisotropy exists between the Yangtze and Cathaysia Blocks. The fast polarization axes in this belt correspond to the NE-trending orogen between the two blocks. In the deeper crust of the Cathaysia Block we image multiple areas of diffuse low-velocity anomalies. As defined by the margins of the strongly anisotropic belt, the Yangtze–Cathaysia suture zone is delineated by lines that traverse: Shaoxing–Jiangshan–Pingxiang–Longsheng–Hechi and Shitai–Jiujiang–Yueyang–Dayong–Jishou. Further analysis of the seismic data links deep low velocities with widespread Late Mesozoic magmatism in the Cathaysia Block. The deep low velocities are likely a result of dehydration of the subducting Pacific Plate causing mantle upwelling and underplating. [ABSTRACT FROM AUTHOR]

Most of the major rivers in the eastern margin of the Tibetan Plateau are distributed along the tectonic suture zone, where many giant landslides are present. The catastrophic Baige landslide that occurred in 2018 developed in the Jinsha River tectonic suture zone. What is the geo-structure prone to sliding in the Jinsha River tectonic suture zone? How does it control landslide evolution? A special soft rock/soil, altered clay, is found in the Jinsha River tectonic suture zone, and this altered clay may play an important role in giant landslide initiation. To understand the mechanism of the strength weakening of the altered clay and its effect on the formation of giant landslides, taking the Baige landslide as a typical case study, detailed field surveys and laboratory experiments were performed, and the process and mechanism of the transformation of altered clay into sliding zone soil were analyzed. The results indicate that (1) the altered clay is rich in platy layer clay minerals, so it has strong water sensitivity and expansibility. Furthermore, it has significant strain-softening behavior and extremely low residual strength due to the directional arrangement of clay minerals. (2) The evolution process of the Baige landslide was controlled by altered clay and rock mass discontinuities. Altered clay developed along ophiolite discontinuities and formed the weak interlayer of the slope. Due to long-term gravity creep, intermittent rainfall, and earthquakes, the strength of the altered clay was continuously weakened, and the sliding zone gradually penetrated, which finally led to the failure of the Baige landslide. The results of this manuscript are helpful for understanding the evolution mechanism of giant landslides in tectonic suture zones around the world. [ABSTRACT FROM AUTHOR]

Subduction and closure of the Proto-Tethys and Palaeo-Tethys oceans were important events in the assembly of Eurasia, and created the Central China Orogenic Belt (CCOB). This paper presents a new tectonic model for the CCOB in which we propose that elongate Precambrian basement blocks within the CCOB were originally part of a single ribbon continent, here named K-Qubed after the K unlun- Q aidam- Q ilian- Q inling regions. K-Qubed separated from the South China Block in the Neoproterozoic. Dextral-oblique subduction of the Proto-Tethys Ocean took place southwards (present co-ordinates) under K-Qubed in latest Precambrian - Cambrian times (ca. 550–500 Ma). Subduction-accretion complexes were generated alongside the basement, while arc magmatism overprinted both basement and accretionary crust. Initial collision of the northern side of the ribbon continent and the North China and Tarim blocks occurred at ca. 500 Ma. High-pressure and ultrahigh-pressure metamorphism resulted by ca. 490 Ma, in the North Qilian, South Altun/North Qaidam and North Qinling regions. Collision triggered a flip in subduction polarity, and caused a subduction-accretion complex and magmatic arc to build out southwards from K-Qubed, as Palaeo-Tethys was consumed northwards in the Ordovician. Magmatic timings were similar between different tectonic units; twin peaks in magmatism at ca. 500–490 Ma and ca. 440–430 Ma occurred in several terranes. Oblique subduction caused strain partitioning, in turn causing slivering and across-strike repetition of basement and accretionary crust. Tectonic units in the Qilian Shan and Kunlun can be partly correlated with equivalents in the Qinling Orogen. We suggest a match between the North Qilian Orogenic Belt and the Erlangping Unit, between the Central Qilian Block and the North Qinling Belt, between the South Qilian Accretionary Belt and the Shangdan Suture Zone. Basement terranes of the Qaidam region and the East Kunlun Orogen have no obvious lateral equivalents in the Qinling, and are truncated at the eastern margins by the West Qinling Belt. There are similar ages for peak metamorphism at ca. 440–420 Ma in an eclogite belt in the North Qaidam Ultra High-pressure Metamorphic Belt (NQUB) and eclogite localities in the East Kunlun Orogen. We interpret this metamorphism to be result of slab break-off beneath the K-Qubed continent, with metamorphic rocks repeated across-strike by dextral shear. The component of Precambrian crust in the Kunlun diminishes westwards into the West Kunlun, where Early Palaeozoic accretion of crust was more continuous. A magmatic gap throughout the CCOB between ca. 370 and ca. 290 Ma was possibly related to extremely oblique and/or slow plate convergence, or represents a time through which subduction stopped. Renewed northwards subduction of the Palaeo-Tethyan Ocean took place under the south side of the Kunlun and Qinling in the Permian, completed by Triassic collisions of the Qiangtang and South China blocks with the southern side of the CCOB. This model for the CCOB is an alternative to collisional and accretionary end members for orogeny, whereby oblique subduction and collision of a ribbon continent produces interleaving of basement and more juvenile terranes. Closure of Proto-Tethys did not involve multiple, separate and synchronous subduction zones, or repetition of a subduction zone by oroclinal bending, as previously proposed. [ABSTRACT FROM AUTHOR]

The western segment of the suture zone between the Yangtze and Cathaysia blocks, which is the most important tectonic boundary related to the formation and rifting of south China, is enigmatic and not fully understood due to the sporadic exposure of Precambrian strata and ophiolites. Three‐dimensional electrical resistivity models derived from inversion of magnetotelluric data identified a lithospheric‐scale conductive zone extending northeastwards beneath the Youjiang basin, which was interpreted as the western segment of the suture zone. The high conductivity and coincident high magnetic anomalies closely match the location of Carlin‐type gold deposits, which can be explained by fluids and gold‐bearing sulfide minerals in a fossil suture zone. Inconsistent with the southeast‐dip resolved at the eastern segment of the suture zone (the Jiangshan‐Shaoxing fault) in the earlier study, the slightly north‐dipping geometry at the western suture zone implies the reactivation by northward subduction and closure of the Paleo‐Tethys Ocean. Plain Language Summary: Suture zones are tectonic scars that mark the subduction, collision, and amalgamation of different tectonic units. Imaging suture zones is critical because they are first‐order tectonic boundaries and can play a guiding role in continental rifting and breakup. The suture zone between the Yangtze and Cathaysia blocks is the most important tectonic boundary in south China. While the eastern segment of this suture zone is agreed to be located along the Jiangshan‐Shaoxing fault, the western segment of this suture zone is under debate. This study used magnetotelluric method to image the deep earth structure beneath the western boundary of the Yangtze and Cathaysia blocks. We identified a high‐conductivity zone from the subsurface to a depth of 80 km and interpreted this zone as being caused by fluids and gold‐bearing sulfide minerals in a fossil suture zone. The conductivity pattern observed in this suture zone differs from that in the earlier study about the eastern segment of the suture zone. This implies that the western suture zone has been modified after the initial collision of the two continents, perhaps by northward subduction and closure of the Paleo‐Tethys Ocean. Key Points: Magnetotelluric array data were inverted to obtain the lithospheric resistivity structure in southwestern ChinaThree‐dimensional resistivity model images a Precambrian suture beneath the Youjiang basinThe geometry resolved at the suture zone implies the reactivation by northward subduction and closure of the Paleo‐Tethys Ocean [ABSTRACT FROM AUTHOR]

In a new study, Wu, Wang, Zhou, Zhao, Haproff, et al. (2022, https://doi.org/10.1029/2022GC010662) present a comprehensive study of the North Margin Orogen of the North China Craton (NCC), showing that older accreted rocks in this belt preserve a record of active margin magmatism from 2.2 to 2.0 Ga, followed by collisional tectonics, marked by mélange and mylonitic shear zones, then granulite facies metamorphism at 1.9–1.8 Ga, marking the final collision of the NCC with the Columbia Supercontinent. The multidisciplinary studies presented in this work support earlier suggestions that the North China Craton amalgamated during accretionary orogenesis in the Neoarchean to earlier Paleoproterozoic, and that the late widespread 1.85 Ga high‐grade metamorphism is craton‐wide in scale, and not confined to a narrow orogen in the center of the craton. This new understanding creates new possibilities for refining reconstructions of one of Earth's earliest, best documented supercontinents, showing a globally linked plate network at 1.85 Ga, and suggests drastic new correlations and models for mineral resource exploration. Key Points: The Paleoproterozoic collisional orogen of the North China Craton with Columbia Supercontinent is positively identifiedThis "North Margin Orogen (NMO)" changes reconstructions of the oldest well‐established supercontinentCorrelations of the NMO with the gold‐rich Birimian of West Africa suggest a new mineral exploration strategy for China [ABSTRACT FROM AUTHOR]

The North Qilian Orogen is considered as a representative oceanic suture zone formed by the closure of the North Qilian Ocean, which forms the northern part of the Proto-Tethys Ocean along the northern margin of the eastern Gondwana during the Early Paleozoic. However, the time interval of Early Paleozoic subduction system remains controversial, especially the part along the northwest margin where it is connected to the Alxa Block. Here we explored the whole rock geochemistry and LA-ICP-MS zircon U–Pb geochronology on a suite of tuff and clastic rocks from the Angzanggou Formation in the west margin of the North Qilian Orogen. Zircon U–Pb dating of tuff samples yielded the eruption ages of ca. 438 Ma. Detrital zircon from clastic rocks have revealed three age populations: 0.4–0.6 Ga (peak at 438 Ma), 0.7–0.9 Ga (peak at 875 Ma), and 0.93–1.1 Ga (peak at 984 Ma). Zircons with U–Pb ages of 0.4–0.6 Ga are markedly different from those of North China Block and Alxa Block, but are similar to zircon ages determined for Qilian Paleozoic arc-related magmatic rocks. Based on previous geochemical and geochronological data from the early Paleozoic igneous and clastic rocks, we believed that the subduction-accretion processes in North Qilian Orogen lasted until the Angzanggou Formation in the Early Silurian, thus leading to the formation of a fore-arc basin. [ABSTRACT FROM AUTHOR]

The eastern Paleo-Tethyan Jinshajiang–Ailaoshan–Song Ma orogenic belt in the Southeast Tibetan Plateau represents the tectonic boundary between the Indochina and South China blocks. Regional Cenozoic lithospheric strike-slip movements caused by the India–Asia collision have modified many of the pristine geological records associated with the Indosinian orogeny. The lack of reliable petrological evidences, particularly of high-pressure (HP) metamorphism, has hindered the tracing of the evolutionary history of the Paleo-Tethyan orogenic belt. We report the mineralogy, geochemistry, geochronology and thermodynamic modelling of eclogite lenses/blocks and their host garnet–phengite schists from the Song Ma Suture Zone of Northwest Vietnam and reveal their protolith origins and metamorphic evolution. The eclogites are geochemically similar to mid-ocean ridge basalt, showing weak depletions in high field-strength elements, positive to slightly negative whole-rock ɛNd(t) ratios (−1.69 to +5.15) and slightly high 87Sr/86Sr(t) ratios (0.70466–0.70834). The igneous protolith of the eclogites formed in the late Silurian (425.4 ± 3.6 Ma; igneous zircon dating, 638–459 Ma TDM dating), which makes them the oldest known mid-ocean ridge mafic rocks in an ancient Paleo-Tethyan Ocean. Various eclogites preserve similar peak mineral assemblages (garnet + omphacite + phengite + rutile + quartz ± epidote/clinozoisite ± kyanite ± winchite) under indistinguishable peak conditions. Their prograde P–T trajectories show a uniform pattern of progressive heating and weak compression along a geothermal gradient of 8°C–10°C/km, indicating a warm subduction setting at a low angle that contrasts with the cold oceanic subduction recorded in the adjacent Paleo-Tethyan suture zones. Combined with detrital U–Pb ages from previous studies, our geochronological data indicate that the host schists originated from continental crust within the South China Block and underwent a pervasive Triassic HP metamorphism related to the Indosinian orogeny. The eclogites and host schists yielded HP metamorphic ages of 239–234 Ma and retrogressive amphibolite-facies metamorphic ages of 231–229 Ma, suggesting rapid cooling (14.0°C–21.6°C/Myr) and exhumation (6.4 km/Myr) from the mantle to the crust. The Song Ma eclogites and their host schists formed when the final ocean closure transitioned to the initial Indochina–South China collision. The Song Ma eclogites and their host schists provide essential information on the opening and closure of the eastern Paleo-Tethys and the subsequent amalgamation of Southeast Asian continental fragments. [ABSTRACT FROM AUTHOR]

The Luobei Complex in Northeast (NE) China lies in the northern Heilongjiang Complex and comprises a sequence of low-temperature–high-pressure metamorphic rocks distributed along the N–S-oriented suture zone between the Jiamusi and Songliao blocks. However, the timing of formation and tectonic setting of the Luobei Complex remain poorly constrained. Here, we present petrological, geochronological, and geochemical data for metasedimentary rocks from the Luobei Complex to elucidate its origin and tectonic setting. The Luobei Complex is characterised by the occurrence of serpentinite, blueschist, greenschist, amphibolite, and marble, which form lenses or interlayers in a matrix of two-mica schist, albite schist, quartz schist, and granitic gneiss. Zircon U–Pb dating of four metasedimentary rocks yields consistent Late Triassic maximum depositional ages (ca. 214 Ma). Detrital zircons from the Luobei Complex yield ages ranging from 1889 to 202 Ma, with age peaks at 504, 350, 265, and 214 Ma. The ages prior to 350 Ma exist in both the Jiamusi Block and the Central Asia Orogenic Belt (CAOB), indicating that the syn-deposition of Luobei Complex, meanwhile, the lack of ages younger than 350 Ma suggests that the Jiamusi Block rifted eastward from the CAOB. Geochemical data indicate that the studied metasedimentary rocks were formed in a continental island arc setting. These results, together with the Early Jurassic metamorphism reported by previous studies, constrain the timing of final collision to Late Triassic–Early Jurassic after subduction of the Jiamusi Block beneath the Songliao Block. Combining our new results with previous findings, we propose a new tectonic model: (1) during the latest Carboniferous to Late Triassic, the Jiamusi Block rifted from the CAOB as a result of Mongol–Okhotsk oceanic plate subduction; and (2) during the Late Triassic and Early Jurassic, the Jiamusi Block was reunited with the Songliao Block, and the Heilongjiang Complex formed, as a result of Paleo-Pacific plate subduction. [ABSTRACT FROM AUTHOR]

[Display omitted] • The depositional age of the Xiufeng Formation was estimated as 159 Ma. • The Mohe Formation has a bidirectional provenance from 150 Ma. • The tectonic setting transformed from compression to extension during 135–128 Ma. • A series of E-W and NE-SW-trending normal faults occurred since the Early Barremian. • The final closure of the Mongol-Okhotsk Ocean has been limited to 150–135 Ma. The Mohe basin is located to the south of the eastern Mongol–Okhotsk suture belt and contains critical stratigraphic records and thrust-nappe structures for understanding the closure of the eastern Mongol–Okhotsk Ocean. This paper discusses the formation ages, provenance, and tectonic setting of the Xiufeng and Mohe formations, and further reveals the timing of the final closure of the Mongol–Okhotsk Ocean and the tectonic evolution of the Mohe basin. The weighted mean 206Pb/238U ages for the youngest zircon of these samples indicate that the maximum depositional ages of the Xiufeng, Mohe and Tamulangou Formations were conservatively estimated at 159 Ma, 150 Ma and 128 Ma, respectively. From Late Triassic to Late Jurassic (150 Ma), the Mongol-Okhotsk Ocean was consumed by bidirectional subduction expressed by subduction under the Siberian Craton and the Erguna Block, respectively. The intense subduction led to the compression of the continental arc and the basement uplift of the Erguna Block, which provided abundant clastic sediments to the Xiufeng-Ershierzhan Formations. During the Late Jurassic-Valanginian (150–135 Ma), the Mongol-Okhotsk Ocean closed rapidly, which finally caused the collision between the Erguna Block and the Siberian Craton. Meanwhile, the southern margin of the Siberian Craton was uplifted and started furnishing sediments into the Mohe-Kaikukang Formations, which may have a bidirectional provenance. The subsequent crustal shortening associated with collision between the Erguna Block and the Siberian Craton led to nappe structures, syn‐collisional folds, and nearly N-S-trending reverse and oblique-slip faults occurred along the northwestern margin of the Mohe basin. Between 135 and 128 Ma, the Mohe basin entered the stage of tectonic setting transformation, which is the crucial period for the Mohe basin to transform from compression to extension. Since the Early Barremian (ca. 128 Ma), the compressional environment was transformed into a post-orogenic extensional tectonic environment, and a series of nearly E-W and NE-SW-trending normal faults occurred, which might have been controlled by the slab rollback of the Paleo-Pacific Plate and detachment of the Mongol-Okhotsk oceanic plate after the closure of the Mongol-Okhotsk Ocean. [ABSTRACT FROM AUTHOR]

The Ailaoshan orogenic belt, located in the SE margin of the Qinghai–Tibet Plateau, is an important Paleo-Tethys suture zone in the eastern margin of the Sanjiang Tethys tectonic domain. The areas of Mojiang and Zhenyuan, located in the middle part of the Ailaoshan orogenic belt, are the key parts of the Ailaoshan Paleo-Tethys Ocean closure and collision orogeny. The rhyolites outcropped in the Mojiang area, and the granite porphyries outcropped in Zhenyuan area, are systematically studied for petrology, isotope geochemistry and geochronology. The Zircon U-Pb geochronology of rhyolites and granite porphyries give weighted average ages of 253.4 ± 4.2 Ma and 253.3 ± 2.0 Ma, respectively, both of which were formed in the late Permian period. The rhyolites belong to potassic calc-alkaline to subalkaline series. The patterns of the rare earth elements (REE) show a right-inclined seagull-type distribution, and the trace elements plot is right-inclined. The granite porphyries are high potassic calc-alkaline to subalkaline. The REE patterns show a right-inclined distribution, and the trace elements plot is right-inclined, which is consistent with the typical patterns observed in the crust. The peraluminous, highly differentiated and high ASI values suggest that rhyolites and granite porphyries are S-type granites. The zircon εHf(t) of the rhyolites range from −7.22 to −0.72, and two-stage Hf zircon model ages are (TDMC) 1771–2352 Ma, indicating that the magma source area is mainly crust-derived. The zircon εHf(t) of the granite porphyries range from −0.97 to 4.08, and two-stage Hf zircon model ages are (TDMC) 1336–1795 Ma, indicating that the magma is derived from a depleted mantle source and the partial melting of ancient crustal materials. The rhyolites and granite porphyries were possibly formed in the syn-collisional tectonic setting during the late Permian, and their ages limited the time of the final closure of the Ailaoshan Ocean and the initiation of collisional orogeny. [ABSTRACT FROM AUTHOR]

Zircon Hf-isotopic mapping can be regarded as a useful tool for evaluating the coupling relationship between lithospheric structure and metallic mineralization. Hence, this method shows important significance for mineral prediction. To explore this potential, the published granite zircon Hf isotope data from the Sanjiang Tethyan Orogen were systematically compiled. This study uses the Kriging weighted interpolation in the Mapgis software system to contour Hf isotopes, revealing a relation between the crustal structure and metallogenesis. The mapping results suggest that the Changning–Menglian suture zone is the boundary between ancient and juvenile crust, viz., the western terranes have ancient crust attributes, whereas the eastern terranes exhibit the properties of new juvenile crust. In addition, this study also found that the mineralization and element types in the Sanjiang Tethyan Orogen have a coupling relationship with the crustal structure. The distribution of porphyry Cu-Mo-Au deposits is mainly controlled by the new juvenile crust, whereas the magmatic-hydrothermal Sn-W and porphyry Mo-W(-Cu) deposits are closely related to the reworked ancient crust. The results of zircon Hf isotope mapping prove that the formation and spatial distribution of deposits are related to the composition and properties of the crust. Hf isotope mapping can reveal the regional metallogenic rules and explore metallogenic prediction and metallogenic potential evaluation. [ABSTRACT FROM AUTHOR]

This study was conducted to define the background structure and petrogenetic significance of the Early Cretaceous magmatic rocks in the Badaguan area of northern Daxing'anling and to explore the Late Paleozoic tectonic evolution of the Mongol-Okhotsk suture zone. The Early Cretaceous magmatic rock was systematically investigated using zircon U-Pb dating and geochemical and petrological analyses. The results show that the rock: mainly consists of granites and rhyolites; has an age of 125–140 Ma; has a strong MgO, Al2O3, and total alkali content; has a SiO2 content of 61.68 wt% to 77.41 wt%; and contains Rb, Th, U, and light REEs with depleted levels of of Sr, P, Ti, and heavy REEs. When combined with the Hf isotopic characteristics of the Early Cretaceous magmatic rock from the Erguna Massif, these results suggest that the magma originated from the partial melting of basal crustal materials during the Neoproterozoic–Phanerozoic period and that various mineral forms (including hornblende, plagioclase, and apatite) underwent fractional crystallization processes during the evolution of the magma. The Early Cretaceous magmatic rock from the Badaguan area recorded the extensional environment of the lithosphere after the closure of the Mongol-Okhotsk Ocean, and this hypothesis is consistent with the results of previous studies on the tectono-magmatic activities in Northeast China during the same period. [ABSTRACT FROM AUTHOR]

Abstract: Accretionary complexes record critical information about the history of subduction and accretion along the southern margin of Asia prior to the India–Asia collision. This paper presents detailed field mapping, petrographic and detrital zircon U–Pb data from an accretionary complex within the Yalung–Zangpo suture zone, southern Tibet. From structurally higher to lower levels, the accretionary complex consists of a serpentinite mélange, the chert-matrix Tangga mélange, the mud-matrix Pomunong mélange, and the coherent Rongmawa Formation. The Tangga mélange consists of Late Triassic–Early Cretaceous abyssal chert and siliceous shale with blocks of chert and mafic to ultra-mafic rocks. The Tangga mélange was accreted beneath ophiolitic rocks during the Aptian. The Pomunong mélange consists of a Late Jurassic–Early Cretaceous hemipelagic siliceous shale and chert matrix with blocks from Early Permian seamounts and from Late Cretaceous trench-fill sandstones; it was accreted beneath the Tangga mélange after the Aptian but prior to 71Ma. Structurally beneath these mélanges to the south, the uppermost Cretaceous Rongmawa Formation consists of turbiditic sandstone, pelagic chert, and siliceous shale and records a transition in depositional setting from lower abyssal plain to upper trench. Detrital zircons from sandstone blocks of the Pomunong mélange and the coherent Rongmawa Formation display similar U–Pb age spectra and are dominated by peaks at 71–231Ma, 481–693Ma, and 701–1372Ma. These age peaks overlap with igneous crystallization ages and detrital zircon ages from sedimentary strata in the Lhasa terrane. Our data indicate that the serpentinite mélange, Tangga mélange, Pomunong mélange and Rongmawa Formation comprise a southward-younging accretionary complex that developed during the northward subduction of Neo-Tethyan oceanic lithosphere beneath the south margin of the Lhasa terrane and that all exposed ophiolitic and accretionary complex assemblages were accreted to the Asian margin prior to the India–Asia continental collision. [Copyright &y& Elsevier]

Abstract: The extension of the suture zone between the Siberian and Kazakhstan continents in China has been a matter of debate because few outcrops of ophiolitic mélange have been found so far. The recently found Tuerkubantao ophiolitic mélange, which is located east of the Kekesentao Mt. in the Buerjin County of the Chinese Altay, provides an important clue for this problem. This paper presents the results of field investigation, petrology, U-Pb isotope dating of zircons and bulk-rock geochemistry of the Tuerkubantao mélange rocks. The mélange consists of fault-contacted ultramafic rocks, gabbro, diabase, basalt, flysch and granitoids. The ultramafic-mafic rocks are Mg-rich (#Mg = 4.25–6.35) and w(SiO2) spans 38.8%–46.8%. Basalt and gabbro are geochemically similar and are characterized by low w(FeOt) (10.9%), total alkali w(Na2O + K2O) = 2.58%) and w(TiO2) (1.17%) and affinity to the Mg-rich tholeiite series. The flat REE and trace-element patterns of the ultramafic-mafic rocks are indicative of their ophiolite origin, i.e., formation in a mid-oceanic ridge setting. The fragments of low-K gneissic granite formed in suprasubduction or syn-collisional setting. Zircons from gabbro and gneissic granite yielded U-Pb ages of 363 and 355 Ma, respectively, suggesting Late Devonian mid-oceanic spreading and oceanic subduction accompanied by suprasubduction magmatism. The Tuerkubantao ophiolite together with the Qiaoxiahala and Buergen ophiolites of the Kekesentao belt define an ophiolitic mélange belt extending along the Erqis fault. This belt probably belongs to the Ural-Zaisan-South Mongolian suture-shear zone formed during the subduction of the Paleo-Asian Ocean and subsequent collision of the Siberian and Kazakhstan continents. [Copyright &y& Elsevier]

Abstract: Despite more than 30 years’ studies in the Yarlung Zangbo Suture Zone (YZSZ), southern Tibet is still a region of discovery and the geological evolution of the Neo-Tethys here remains controversial. In this paper we present the new field observation, petrography, zircon U–Pb dating and geochemistry of the Zhongba mafic rocks in the western segment of the YZSZ. Zircon U–Pb analyses from a diabase using SIMS (Secondary Ion Mass Spectrometry) yielded a concordant age of 125.7±0.9Ma. All the Zhongba mafic rocks exhibit LREE enrichment (LaN/YbN =4.7–15.8) without Eu anomalies (δEu=0.97–1.01). Their Primitive-Mantle-normalized trace element patterns are similar to those of the average OIB and Hawaii alkaline basalts, as well as other OIB-type rocks already reported in the central-western YZSZ. These observations lead us to suggest the existence of a series of seamounts within the Neo-Tethys during the Early Cretaceous. These OIB-type rocks could be originated from (1) hotspot mantle; (2) near-ridge seamounts by melting-induced mixing of two distinct mantle sources; (3) late-stage magmatism fed by melts that originated from an asthenospheric window due to slab delamination. Combining literature data from the entire YZSZ, which include studies of the MORB- and IAB-type rocks and mantle peridotites, we prefer the third explanation that the OIB-type rocks represent a late-stage magmatic activity above an intra-oceanic supra-subduction zone within the Neo-Tethys. [Copyright &y& Elsevier]

Abstract: The observation data for radon from national geochemical observation points have been collected and analyzed following the Ms 8.0 Wenchuan earthquake on 12th May, 2008 and a post-seismic effect of radon was observed. It has provided the most abundant record since the radon observation network had been set up in china. In this paper, the behaviour of the post-seismic effects of radon gas and water radon is reported. The results were obtained that observation points recording post-seismic effects of radon release were distributed mainly along the extended line of Longmenshan faults, and located on the boundary faults of regional tectonic blocks (Category II) and inside some tectonic blocks (Category II). The pattern of variation in radon emission observed was largely in the form of rising steps. A comparison was made with the variation of water level and flow observed simultaneously with radon measurement, to investigate a dynamic link with post-seismic radon with underground water conditions. This study confirmed a response of radon concentration to the seismic wave, and also raised other scientific issues, such as the dynamic association between geochemical composition of underground water and medium parameter variation of aquifers under dynamic loading, which may support the study of the mechanism of earthquake precursors of radon. [Copyright &y& Elsevier]

Abstract: Along the Qinling–Dabie–Sulu orogenic belt in China crops out the world''s largest terrane composed of ultrahigh-pressure (UHP) metamorphic rocks. Differences in the timing and mechanisms of oceanic and continental subductions are assumed to be responsible for different ages of high-pressure (HP) and UHP slices in different parts of the belt. The western part of the Dabie orogen (western Dabie terrane) holds a key to understanding of the transition from oceanic to continental subduction. This paper reports geochronological results to test a two-stage tectonic model for the exhumation of HP/UHP rocks in western Dabie. This model involves two different stages and types of extrusion for exhumation of the HP/UHP rocks in east-central China. Mica Ar/Ar ages, ranging from 241 to 231Ma, indicate a general middle Triassic cooling probably driven by early upward extrusion during the collision between the North and South China Blocks. Late Triassic–Early Jurassic cooling was associated with later eastward extrusion, ranging from 200 to 184Ma. The second event is recorded also in mica in the region that was not affected by later deformation and magmatism. The lateral movement along lithosphere-scale faults resulted in the eastward extrusion of the HP–UHP metamorphic terrane, which was followed, in the Late Triassic–Early Jurassic time, by a major compressive event. These two extrusion events are correlative with the two stages of Triassic exhumation of the western Dabie HP–UHP rocks, respectively. Wintin the framework of the Qinling–Dabie–Sulu orogenic belt, it is suggested for western Dabie that the subduction/exhumation of blueschist-facies unit is related to the Mianlue suture, whereas the subduction/exhumation of HP/UHP eclogite-facies units is related to the Shangdan suture. [Copyright &y& Elsevier]

Abstract: The Qilian Shan, located in the northern Tibetan Plateau of NW China, has an excellent record of early to middle Paleozoic subduction–accretion that resulted from convergence between the Alax and Qaidam blocks, but there is no consensus about its detailed tectonic history. This paper summarizes its tectonic divisions and discusses its tectonic evolution from the Cambrian to Devonian. The belt has the following tectonic divisions: In the far north the southern passive margin of the Alax block is juxtaposed against an early Cambrian to Ordovician, Marianan-type intra-oceanic arc (North Qilian). The North Qilian arc is separated from a Japanese-type arc (Central Qilian) to the south by a high-pressure metamorphic belt composed mostly of ophiolitic slices and oceanic crusts. The Central Qilian is bounded to the south by a wide mélange zone (South Qilian), consisting of ophiolitic slices and continental margin sequences. Farther to the south lies the Oulongbuluk microcontinent that is separated from the Qaidam block and farther south by an ultrahigh-pressure metamorphic belt. Tectonostratigraphic analysis, together with geochemical, geochronological, and geophysical data, indicates a complex evolution by subduction–accretion processes from the Cambrian to the Devonian before final amalgamation and docking to the northern Alax block. This model solves the long-lasting discussion on the polarity of subduction in Paleozoic time; this multiple subduction–accretion history sheds light on the continuity of Paleozoic sutures along the Qilian Shan and the nature of the Altyn Tagh fault, and thus contributes to an improved understanding of the tectonic architecture of Central Asia. [Copyright &y& Elsevier]

Abstract: This paper presents a reappraisal of the tectonic evolution of the Zanhuang Massif that lies at the eastern margin of the Trans-North China Orogen, a continent–continent collision belt that marked the amalgamation of the North China Craton in Late Paleoproterozoic. Detailed field work with focus on geometries of structures and kinematics was performed. This was completed with LA-ICP-MS U–Pb analyses on zircon, EPMA U–Th/Pb dating on monazite and 40Ar/39Ar dating on amphibole. These studies led us to propose a new three-fold litho-tectonic subdivision of the massif: The Western Zanhuang Domain (WZD) made of TTG, migmatite and pink anatectic granite is correlated to the Fuping Massif that crops out to the north-west. Both areas represent a continental block, called the Fuping Block, which acquired most of its architecture around 2100Ma ago. The Eastern Zanhuang Domain (EZD) made of TTG and migmatite represents the western edge of an Eastern Neoarchean Block. In between, the Central Zanhuang Domain (CZD) is a NE–SW trending stack of supracrustal, gneiss and mafic magmatic rocks thrust sheets displaced toward the ESE upon the Eastern Block. The lithological features suggest that the CZD represents the remnant of an oceanic basin, called the Taihang Ocean that closed during the amalgamation of the Eastern Block and the Fuping Block around 1880–1850Ma. In agreement with recent work done along the western margin of the belt, in the Lüliang Massif, this study documents the amalgamation of the North China Craton in response to the closure of two oceanic basins, namely the Lüliang Ocean and the Taihang Ocean. West-dipping subductions and collisions involving three distinct continental blocks, called the Western, the Fuping and the Eastern Blocks, took place around 1880–1850Ma. [Copyright &y& Elsevier]

China has the largest antimony (Sb) resources, products and consumption in the world, which plays an important role in the global antimony trade. Chinese Sb deposits are characterized by large resources, concentrated distributions, primary deposits dominating, and associating with numerous valuable elements and minerals. In China, most of Sb deposits are located at the edges of various geotectonic units and are constrained by plate suture zones or large deep fault belts. There are 5 Sb metallogenic belts were distinguished in this paper including the Tianshan-Xingmeng Sb ore belt, Qin-Qi-Kun Sb ore belt, Qiangtang-Sanjiang Sb ore belt, South China Sb ore belt and South Tibet Sb ore belt. Sb deposits are hosted in Mesoproterozoic to Quaternary formations, but most of them were occurred in Precambrian, Devonian and Triassic strata. The ages of mineralization of Sb deposits in China are mainly concentrated in the Indosinian, Yanshanian and Himalayan, while the large-scale mineralization is restricted within the Jurassic to Cretaceous of the Yanshanian. Antimony deposits have multiple sources of ore-forming metals and fluids, of which Precambrian basement strata may be one of the most important. The magmatic activity caused by asthenosphere upwelling may be the main evocator for driving the circulation of groundwater to extract mineralized elements. According to the results of China National Mineral Resources Potential Assessment Project (NMRP), China delineated 94 Sb prospect areas, in which, 15.43 million tons of unproven Sb metal were predicted within 2 km below the surface. Among the 5 Sb ore belts, the South China Sb Ore Belt has the largest number of deposits, identified resources and resources potential, showing strongest mineralization intensity. The Qiangtang-Sanjiang Sb Ore Belt followed, where may become the future antimony resource-base of China. [Display omitted] • The Sb deposits in China are distributed throughout five metallogenic belts. • The Sb metallogenic mainly occurred during Yanshanian in China. • Deep magmatism is the main driving force of the ore fluid circulation. • China has estimated 15.43 million tons Sb metal in 94 prospect areas. [ABSTRACT FROM AUTHOR]

As the remnant of the South Qilian Ocean, the South Qilian suture zone recorded abundant information on the Cambrian–Ordovician subduction history of the southern branch of the Proto-Tethyan Ocean. However, the closure timing of the South Qilian Ocean and subsequent collision are poorly constrained. In this study, we report early Silurian (433–435 Ma) U–Pb ages of felsic subvolcanic rocks from Lianhuashan, Ayishan and Shihuiyao of the Lajishan district within the South Qilian suture zone. They intruded the Late Ordovician – Silurian sedimentary or Late Ordovician volcanic rocks and have high SiO2 (61.43–73.06 wt%), Sr/Y ratios with significant different rare earth elements (REEs) and trace-element spider diagrams, and Sr–Nd isotopic compositions, probably implying that they were formed through distinctly different generation mechanisms. Geochemistry of the Lianhuashan dacites reveals compositions typical of adakitic rocks derived from partial melting of lower crust in a thickened setting. The Ayishan dacites were derived from partial melting of crustal materials with the involvement of minor peridotite mantle, and the Shihuiyao rhyolites were derived from partial melting of felsic crust. The similar geochemical characteristics of coeval post-collisional igneous rocks in the Central Qilian and South Qilian blocks indicates that the lower Silurian subvolcanic rocks were generated in a thickened crust of post-collisional setting. Considering their intrusive contacts with Late Ordovician – Silurian retro-foreland basin and Late Ordovician collisional volcanic rocks, we propose that the South Qilian suture zone was at a transitional stage from collisional to post-collisional during the early Silurian Period. [ABSTRACT FROM AUTHOR]

The middle reaches of the upstream of Jinsha River (MRUJR) is located in the eastern segment of the Jinsha River suture zone on the southwest of China. A study of the MRUJR based on tectonic geomorphology is noteworthy for providing a profound understanding of the tectonic transition between the Sichuan‐Yunnan and Qamdo blocks and active tectonics in various subbasins. Based on the global digital elevation model Shuttle Radar Topography Mission 1 (30 m resolution) data and geographic information system techniques, four geomorphic indices, the hypsometric integral, stream length‐gradient, drainage basin asymmetry, and drainage basin shape were calculated and analysed. Combined with geologic evidence from field surveys and fault slip rates estimated, the tectonic activities and mechanisms were discussed. Through the specific analytical comparisons, the variations in the geomorphic indices were unlikely affected by lithology and climate but showed changes in relevant tectonic activity. The analysis results of geomorphic index value manifested related strong activities in the northwestern and southeastern regions of MRUJR, tilt directions are mainly SW–NE and NE–SW, respectively. The MRUJR is undergoing rapid uplift. These results are consistent with the field evidence. [ABSTRACT FROM AUTHOR]

The 'green-bean rock' (GBR) is a greenish or yellowish green Triassic potassium-rich felsic tuff containing prominent bean-like quartz grains, which is widespread in the Yangtze platform and Nanpanjiang basin, South China. This paper studies the age, origin and tectonic setting of the GBR from the western margin of the Yangtze platform through whole-rock geochemistry and zircon U--Pb geochronology and Hf isotopes. In contrast to the Nanpanjiang basin, where multiple GBR layers are developed and encompass the Olenekian-Anisian boundary (OAB), which is constrained to be at 247.1–247.3 Ma, the age of the single GBR layer in the western margin of the Yangtze platform and its relationship with the OAB have not been determined. U--Pb dating on zircons from the GBR in this study yielded an age of 247.49 ± 0.68 Ma, which is considered to be comparable to that of the OAB, and thus the GBR may be used as a marker for regional stratigraphic correlation. The volcanic ashes of the GBR have been previously suggested to be derived from the Siberian Traps Large Igneous Province or from the Shiwandashan-Qingfang suture zone to the south of the Nanpanjiang basin. However, the whole-rock geochemistry of the GBR, especially enrichment in LREE, Th and U and depletion in Nb, Ta, Sr, Ba, K, Rb and Ti, and strong to moderate negative Eu anomalies (δ Eu = 0.16–0.20), suggest that the volcanic ashes are more likely derived from the adjacent Sanjiang Orogen to the southwest. The zircon geochemistry, especially the negative ε Hf (t) values (−16.4 to −5.1) and old two-stage Hf model (T DM2) ages (1.60–2.30 Ga), are also similar to those from the Early-Middle Triassic felsic volcanic rocks in the Sanjiang Orogen. The subduction of the Paleo-Tethys Ocean was previously inferred to have started between Early Permian and Middle Triassic. The data obtained in this study, in combination with those compiled for igneous rocks and volcanic ashes from Middle Permian to Late Triassic from the region, suggest that the subduction initiation of the Paleo-Tethys Ocean began no later than ~254 Ma, in middle Late Permian. • The new zircon U--Pb age of 247.49 ± 0.68 Ma was obtained for the GBR. • The GBR can be used as a marker for the Olenekian-Anisian boundary (OAB). • The GBR are derived from the Sanjiang Orogen. • The subduction of the Paleo-Tethys Ocean started at 254.8 Ma. [ABSTRACT FROM AUTHOR]

• Three magnetotelluric profiles were obtained at the western margin of Songliao Basin. • Two low-resistivity strips with opposite dips are developed in this region. • The Nenjiang-Balihan fault is arranged in en echelon pattern in the plane. • The formation of Nenjiang–Balihan fault was controlled by two main tectonic events. Located in the famous gravity gradient belt ranging from the Mt. Great Xing'an through Mts. Taihang and Wuling in East China, the Nenjiang-Balihan (NJBLH) fault is important for the understanding of the formation and evolution of Mesozoic and Cenozoic basins in NE China. The distribution and deep structure of the middle and northern segments of this fault are poorly known because of thick sedimentary cover. In this paper, an electrical structure across the western margin of the Songliao Basin and eastern margin of the Great Xing'an Range is revealed on the basis of three magnetotelluric (MT) sounding survey profiles. The results show the development of a low-resistivity layer (L2) and two low-resistivity strips with opposite dip (L1 and L3) in the lower portion of the small-scale basins or sags. The west-dipping low-resistivity strip L1 is considered to be the trace of a paleo-suture zone. The transverse low-resistivity layer L2 may reflect the Palaeozoic sedimentary strata in the basin, and the east-dipping low-resistivity strip L3 represents the NJBLH fault, the presence of which exhibits a gentle sloping tendency from the shallow to the deep portion of the fault cut through the Moho. The NJBLH fault is segmented on the plane, with an overall left-slip NE-trending en echelon arrangement. Presumably, the NJBLH fault began to form during the Jurassic under the influence of the closure of the Mongolia–Okhotsk Ocean in the northwest, and the fault subsequently experienced left-lateral strike-slip movements due to the NW-trending subduction of the Paleo-Pacific Izanagi Plate toward the Eurasian Plate. [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]

The Qinling orogen is a key area for understanding the processes of subduction and collision between the South China Block (SCB) and North China Block (NCB). The Wuguan Complex, distributed along the southern margin of the Shangdan suture zone, can provide important constraints on the age of collision between NCB and SCB and the tectonic evolution of the Qinling orogen in Late Paleozoic. Detrital zircons from meta-sedimentary rocks of the Wuguan Complex in the Danfeng-Shangnan area have an age spectrum with two main peaks at ~448 Ma and ~819 Ma, and two subordinate peaks at ~938 and ~1440 Ma, respectively, and are interpreted to have been derived from the North Qinling terrane (NQT). The petrographic and geochemical characteristics of the meta-sedimentary rocks indicate that they were deposited in a fore-arc basin along the southern margin of the NQT. The youngest detrital zircons yield a weighted mean age of 378 ± 3 Ma, indicating that the fore-arc deposition was continuing at least to this time, which implies that the Paleo-Qinling Ocean between the NCB and SCB was not finally closed until at least the late Devonian. In combination with regional data, we propose that sedimentary rocks of the Wuguan Complex might once have been a sequence of late Ordovician to late Devonian strata with intercalated mafic rocks, which has been dismembered by the later tectonic activity. It was metamorphosed during northward subduction of the Paleo-Qinling Ocean at ca. 320 Ma, and slowly cooled through ca. 350°C at ca. 247 Ma (muscovite 40Ar/39Ar age). It has recorded the detailed processes of subduction and collision between the NCB and SCB. [ABSTRACT FROM AUTHOR]

In the deep mining areas of western China, there exist ultrathick and weak cementation strata in the overburdens above the Jurassic coal seams, and the overburden lithology is generally moderately a little weaker than the medium-hard strata. Yet, the practical measurement indicates that the surface movement rule in this area displays the specialty that is apparently inconsistent with its lithology, which increases the uncertainty of safe production in coal mines. In this study, the similar material and numerical simulations were conducted to investigate the movement rule and failure pattern of the ultrathick and weak cementation overburden. In addition, the photographing scale transformation-time baseline parallax (PST-TBP) method was used to monitor the similar material model to makeup for the lacks of Xi'an Jiaotong University Digital Close-range Industrial Photogrammetry System (XJTUDP) software. The findings of this study can be summarized as follows. (1) To some extent, the PST-TBP method can makeup for the deficiency of the XJTUDP software because the measurement accuracy of the PST-TBP method is 0.47 mm. (2) The height of the caving zone is approximately 66 m, and the height of the water suture zone is about 112 m, which is obviously larger than that of the medium-hard and soft overburden in eastern-central China. (3) The first breaking span of the immediate roof reaches 120 m, the cyclic fracturing length is about 60 m, and the separation occurred at 43 m and 66 m above the coal seam. (4) The failure pattern of the ultrathick and weak cementation overburden is "beam-arch shell," and the failure boundary is arch. (5) The Zhidan group sandstone and Jurassic sandstone formations have strong control effects. The Zhidan group sandstone is the main control stratum and the Jurassic sandstone formation is the secondary-control stratum. The research results provide an insight into guiding the safe mining of deep coal in the ultrathick and weak cementation overburden. [ABSTRACT FROM AUTHOR]

Paleomagnetic studies on the syncollisional magmatic eruptions provide a direct way to understand when and where the Paleo‐Tethys closed. We report a well‐dated paleomagnetic pole from the southern Lancangjiang volcanic belt in western Yunnan of China. Stable Characteristic Remanent Magnetizations (ChRMs) were isolated from 21 sites at high temperatures following step‐wise thermal demagnetization. The data pass fold, reversal, and conglomerate tests and are interpreted to be primary thermal remanent magnetizations. The new paleomagnetic pole (46.1°N/176.2°E, K=44.9, A95=4.8°, N=21) yields a paleolatitude of 26.0 ± 4.8°N at the reference site (23.0°N/100.4°E) in the southern Lancangjiang area. This direct paleo‐latitudinal constraint on the Paleo‐Tethys suture zone in western Yunnan indicates that the north branch of the Paleo‐Tethys Ocean closed no later than the Carnian Age of Late Triassic, and confirms a geographic linkage between the North Qiangtang and Indochina Blocks at least during the Early Permian to Late Triassic. Plain Language Summary: The Asian continent is formed by the amalgamation of continental blocks such as the Tarim, North China, South China, Indochina, and Qiangtang. However, questions remained to answer: When did the ocean between them close? How did they drift from the south hemisphere to the north? In this study, we present a paleomagnetic constraint on the Paleo‐Tethys suture zone to quantify when and where the Paleo‐Tethys Ocean closed. The Paleo‐Tethys Ocean closed no later than the early Late Triassic at ~26°N. The Indochina and North Qiangtang drifted together from the south hemisphere to the north during the Permian‐Triassic. Key Points: The southern Lancangjiang volcanic belt formed at a paleolatitude of ~26ºN during the Carnian Stage of the Late TriassicThe north branch of the Paleo‐Tethys closed no later than the Carnian Stage of the Late TriassicA Permo‐Triassic geographic linkage between Indochina and N‐Qiangtang is confirmed [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]

Dating ultra‐high–pressure (UHP) metamorphic rocks provides important timing constraints on deep subduction zone processes. Eclogites, deeply subducted rocks now exposed at the surface, undergo a wide range of metamorphic conditions (i.e. deep subduction and exhumation) and their mineralogy can preserve a detailed record of chronologic information of these dynamic processes. Here, we present an approach that integrates multiple radiogenic isotope systems in the same sample to provide a more complete timeline for the subduction–collision–exhumation processes, based on eclogites from the Dabie–Sulu orogenic belt in eastern China, one of the largest UHP terranes on Earth. In this study, we integrate garnet Lu–Hf and Sm–Nd ages with zircon and titanite U–Pb ages for three eclogite samples from the Sulu UHP terrane. We combine this age information with Zr‐in‐rutile temperature estimates, and relate these multiple chronometers to different P–T conditions. Two types of rutile, one present as inclusions in garnet and the other in the matrix, record the temperatures of UHP conditions and a hotter stage, subsequent to the peak pressure ('hot exhumation') respectively. Garnet Lu–Hf ages (c. 238–235 Ma) record the initial prograde growth of garnet, while coupled Sm–Nd ages (c. 219–213 Ma) reflect cooling following hot exhumation. The maximum duration of UHP conditions is constrained by the age difference of these two systems in garnet (c. 235–220 Ma). Complementary zircon and titanite U–Pb ages of c. 235–230 Ma and c. 216–206 Ma provide further constraints on the timing of prograde metamorphism and the 'cold exhumation' respectively. We demonstrate that timing of various metamorphic stages can thus be determined by employing complementary chronometers from the same samples. These age results, combined with published data from adjacent areas, show lateral diachroneity in the Dabie–Sulu orogeny. Three sub‐blocks are thus defined by progressively younger garnet ages: western Dabie (243–238 Ma), eastern Dabie–northern Sulu (238–235 Ma) and southern Sulu terranes (225–220 Ma), which possibly correlate to different crustal slices in the recently proposed subduction channel model. These observed lateral chronologic variations in a large UHP terrane can possibly be extended to other suture zones. [ABSTRACT FROM AUTHOR]

The field revision of the Carboniferous and Lower Permian stratigraphy of the northern Bogdashan (South Junggar, Northwest China) shows that the Lower to Middle Carboniferous island arc volcanic rocks, widely developed in this region, are overlapped everywhere by carbonate and terrigenous-carbonate sediments, containing occasional lava flows and overlain up the section by thick terrigenous series practically devoid of volcanic rocks. The deposition of limestone occurred at the stage of dying off of a volcanic arc, and the question of their age is of fundamental importance for dating this event. Carbonates are represented by facies of lagoons, shoals, and bioherms that formed on the leveled surface of the arc and on the slopes of the last active volcanoes. Bioherms are Waulsortian mounds and are mainly composed of algal limestones and carbonate mud. There are no framestones composed of corals and sponges (chaetetids) typical of the tropical zone. The facies of shallow crinoid-fusulinid limestones typical of the adjacent territories of the Southern Tien Shan and Tarim are poorly represented. Paleogeographically, the position of bioherms corresponds to the northern boundary of the realm of Pennsylvanian reefs. On the basis of foraminifers, brachiopods, and corals, the age of carbonates is early Moscovian (ca. 315–310 Ma). Cessation of island-arc volcanism, followed by the accumulation of limestone in Bogdashan, occurred sub-synchronously with formation of the West Junggar (Bayingou) suture and may reflect docking of the Bogdashan arc to the Yili active margin of the Kazakhstan continent. Further subsidence of Bogdashan and adjacent regions of the Junggar and Turfan basins, which was somewhat slower at the end of the Carboniferous and more intense in the Early and Middle Permian, may reflect the development of the foreland basin that formed along the northern flank of the Tien Shan orogen. Marine facies were locally preserved in this basin until the Artinskian (ca. 285 Ma), and later the Junggar and Turfan basins lost connection to the ocean and developed in continental environments. [ABSTRACT FROM AUTHOR]

We present new zircon U-Pb and Hf isotopic as well as whole-rock geochemical data for volcanic rocks from the eastern margin of the Xing’an Massif, Northeast China, in order to further our understanding of the suture location between the Xing’an and Songnen-Zhangguangcai Range massifs. Zircon secondary ion mass spectrometry U-Pb dating indicates that the volcanic rocks formed during the Early-Middle Ordovician (473-463 Ma). Compared with the coeval Moguqi basalts (rare earth element [REE] = 171-183 ppm; εHf(t) = +0.3 to +2.7; TDM1 = 1074-977 Ma), the Duobaoshan andesites exhibit lower overall REE abundances (109-131 ppm) with relatively high heavy REE contents, stronger high-field-strength element depletion, higher εHf(t) values (+13.0 to +14.8), and much younger TDM1 ages (559-484 Ma). This suggests that the primary magma for the andesites was generated by the partial melting of a relatively depleted mantle wedge that was metasomatized by subduction-related fluids. The primary magma for the basalts in the Moguqi area was probably derived from the partial melting of a relatively enriched lithospheric mantle that was also modified by fluids sourced from a subducted slab. These interpretations suggest that the andesites in Duobaoshan formed in a newly accreted island arc setting, whereas the coeval basalts in Moguqi formed along an active continental margin. We therefore attribute the Early-Middle Ordovician volcanism along the eastern margin of the Xing’an Massif to the northwestward subduction of the Nenjiang-Heihe oceanic plate beneath the Xing’an Massif. Furthermore, considering coeval igneous activity in the southern parts of the Xing’an Massif, we suggest that a magmatic arc existed along the margin of the Xing’an Massif in the early Palaeozoic (490-420 Ma). We conclude that the location of the suture between the Xing’an and Songnen-Zhangguangcai Range massifs runs from Airgin Sum, via south of Xilinhot, to Ulanhot, Moguqi, Nenjiang, and finally Heihe. [ABSTRACT FROM AUTHOR]

The history of convergence between the India and the Asia plates, and of their subsequent collision which triggered the Himalayan orogeny is recorded in the Yarlung Zangbo suture zone. Exposed along the southern side of the suture, turbidites of the the Jiachala Formation fed largely from the Gangdese arc have long been considered as post-collisional foreland-basin deposits based on the reported occurrence of Paleocene-early Eocene dinoflagellate cysts and pollen assemblages. Because magmatic activity in the Gangdese arc continued through the Late Cretaceous and Paleogene, this scenario is incompatible with U-Pb ages of detrital zircons invariably older than the latest Cretaceous. To solve this conundrum, we carried out detailed stratigraphic, sedimentological, paleontological, and provenance analyses in the Gyangze and Sajia areas of southern Tibet, China. The Jiachala Formation consists of submarine fan deposits that lie in fault contact with the Zongzhuo Formation. Sandstone petrography together with U-Pb ages and Hf isotope ratios of detrital zircons indicate provenance from the Gangdese arc and central Lhasa terrane. Well preserved pollen or dinoflagellate cysts microfossils were not found in spite of careful research, and the youngest age obtained from zircon grain was ∼84 Ma. Based on sedimentary facies, provenance analysis and tectonic position, we suggest that the Jiachala Formation was deposited during the Late Cretaceous (∼88-84 Ma) in the trench formed along the southern edge of Asia during subduction of Neo-Tethyan oceanic lithosphere. [ABSTRACT FROM AUTHOR]

The Baer ophiolitic massif is located in the northern sub-belt of the western segment of the Yarlung Zangbo Suture Zone (YZSZ) and mainly consists of a lherzolite-dominant mantle suite, dolerite intrusions and limited crustal outcrops. The dolerites show sub-ophitic texture and light rare earth element-depleted chondrite-normalized rare earth element patterns similar to normal-mid-ocean ridge basalts (N-MORB); though, they display enrichments in fluid-mobile elements (Rb, Ba, and Sr) and marked depletions in Th and Nb. The U–Pb ages of several magmatic zircon grains recovered from two dolerite samples indicate that the intrusion of the dikes into the Baer lherzolitic mantle occurred at 125.6–126.3 Ma, consistent with the widespread mafic magmatism between 120 and 130 Ma in the Yarlung Zangbo ophiolites. The dolerites have slightly more radiogenic87Sr/86Sr ratios (0.7043–0.7054) in comparison to N-MORB, whereas they show143Nd/144Nd values (0.513067–0.513114) similar to N-MORB and high zircon Hf-isotope compositions. They have a limited range of Nd-isotope (εNd(t) values: +8.2 to +9.1) and juvenile Hf-isotope compositions (εHf(t) values: +8.4 to +14.2 and +10.0 to +15.1) indicating derivation from mantle melts. The moderate spread in theεHf(t) values of zircons indicates derivation of the dolerites parental magma from a weakly contaminated spinel-bearing mantle source. This is also corroborated by the geochemical signatures of the Baer dolerites (enrichment in LILE and depletion in HFSE) suggesting minor slab input to the mantle source of the dike-filling melt. We suggest that the genesis of the dolerite dike-forming melt happened at a stage of subduction initiation in a sub-oceanic mantle domain mildly affected by fluids emanating from the downgoing slab. Our data combined with literature data allow us to presume that the intrusion of the dolerites into the Baer mantle corresponds to an early phase of subduction initiation beneath a developing forearc basin. [ABSTRACT FROM AUTHOR]

The Yellow Sea Transform Fault ( YSTF), the boundary between the Korean Peninsula and the South China Plate was a repeatedly reactivated ancient fault, extant since 1 Ga or more ago. Similarly polycyclic continental collisions along the Qinling-Dabie-Sulu ( QDS) suture dispatched the lateral (vectorial) collisional effects eastwardly toward the Korean Peninsula across YSTF, the east end of the QDS belt. The Korean Peninsula, coexisted with YSTF, has been a promontory of the Sino-Korean Plate ( SKP) at least since the Rodinia assembly, ca 1 Ga. The Jarly Paleozoic rift origin of the Okcheon Trough, a major aulacogen developed within the Korean Peninsula of the Sino-Korean Plate is attributed to the transform role of the YSTF. Euring the Middle Paleozoic, the Yangtze Plate, an inherent component of the South China Plate, collided SKP so mildly and enduringly that SKP had to develop the Late Ordovician-Early Carboniferous 'great hiatus' over the cratonic SKP. Contemporaneously, the clustered aulacogens were formed over an area near the YSTF. It is envisioned that during the middle Paleozoic, the compressed part of the SKP by the eastward-pushing Yangtze Plate formed an extensional upper crust where the aulacogens formed. The Yangtze sea invaded the aulacogens where the clastic sediments of the mixed environment were dominated by the supply from the Yangtze Plate as witnessed by the clastic zircon grains showing the Yangtze-akin isotope dates. The development of both the middle Paleozoic 'great hiatus' and the clustered aulacogens represents the Caledonian tectonic phase though scarcely accompanied deformations or an orogeny. The Carboniferous-Permian metamorphism recorded in the Middle Paleozoic aulacogens represents the Hercynian (Variscan) phase, but without obvious structural deformations. The deepest subduction and the most intensive collision of the Yangtze Plate along the Paleotethyan suture was made in the late Permian-mid-Triassic time, the Indosinian phase. The coeval Songnim Orogeny in Korea was similarly intensive, though it was a derived, secondary, orogeny propagated ultimately from the QDS collision belt. Because of the eastward compression derived then from the QDS collision belt, YSTF was so deformed and considerably pushed eastward that it now occurs as a deformed-dislocated fault zone called the West Marginal Fault of Korean Peninsula ( WMF in Fig. 1). The location of the mid-Triassic Korean Peninsula was inserted between the eastwardly compressing marginal Yangtze Plate and the counter balancing Permian-Triassic subduction-metamorphic-accretionary complex of the Japanese Pacific. Such a sandwich tectonics effectively intensified the Indosinian Songnim Orogeny of Korea. [ABSTRACT FROM AUTHOR]

We studied the geochemical characteristics of three types of Mesozoic igneous rocks from the Luzong volcanic basin: basaltic trachyandesite at Shuangmiao, pyroxene monzonite at Bajiatan, and quartz-syenite (A-type granite) at Huangmeijian. Based on analyses of whole-rock major elements, all investigated rocks are enriched in K, Na, Ti, Al, but depleted in Ca, representing a shoshonitic series. Trace element analyses show that these rocks are characterized by enrichments of large-ion lithophile elements and high field strength elements. Positive Nb and Ta anomalies in the chondrite-normalized spider diagram indicate that the shoshonitic volcanic rocks share similar features with Nb-enriched basalts, which are different from normal island-arc volcanical rocks (they are typically strongly depleted in Nb and Ta). Bulk-rock chemical compositions and Sr–Nd isotopes indicate that the three types of igneous rocks are geochemically comagmatic, suggesting that the melts were derived from an enriched mantle reservoir. We postulate an extensional tectonic setting for the formation of Luzong volcanic basin, possibly related to subduction of a palaeo-Pacific plate beneath the east Chinese continent during the Yanshanian period (Cretaceous). Therefore, the petrogenetic features of those volcanic rocks as well as A-type granites in the Luzong basin indicate that the regional large-scale Fe–Cu–Au mineralization was associated with oceanic slab melting, but not delamination or recycling of the ancient lower continental crust, as previously proposed. [ABSTRACT FROM AUTHOR]

Accurate knowledge of formation pore pressure is a key requirement for safe and cost-effective drilling in overpressured formations. Tectonic compression is an important type of overpressure mechanism, in addition to undercompaction and fluid expansion. However, there is not a valid approach for overpressure estimation in tectonic compression zones. Actually, two lateral stresses are too large to be ignored in tectonic environments. As a consequence, the conventional overpressure estimation methods are not accurate enough for tectonic compression mechanism. This article presents a new approach called the root mean square (RMS) principal stress method that modifies the estimation of pore pressure for tectonic compression zones. The RMS method better considers the characteristics of a 3D stress state. It has been tested in the Kuqa thrust belt of Tarim oil field where significant tectonic compression commonly exists. Pore pressure estimation of this region shows that the RMS method provides more precise pore pressure estimates than conventional methods. [ABSTRACT FROM AUTHOR]

This article presents a study on the variation of mineral composition, fabric and oxygen fugacity from massive to foliated eclogites from the North Qilian suture zone in Northwestern China. These eclogites in the North Qilian zone are said to be low-temperature, high-pressure metamorphic rocks of ocean crust protolith occurring both in massive and foliated types. Included are the investigations on the petrography, microstructure and LPOs of omphacite, and rutile in these low-temperature eclogites.