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The tectonic evolution of the Palaeocene–Eocene Tethys Himalayan foreland basin plays a crucial role in reshaping the collisional orogenic process of the Yarlung–Tsangpo oceanic basin. However, studies examining the sedimentary response during the tectonic evolution of the foreland basin are lacking. In this study, through a detailed field investigation and analysis of Palaeocene–Eocene strata in the Tingri area, we clarified the evolution of the Tethys Himalayan tectonic regions and its sedimentary response. Carbon and oxygen isotopes, geochemistry and detrital zircon U–Pb dating demonstrated that the lower Palaeocene Jidula Formation and upper Palaeocene–lower Eocene Zongpu Formation were deposited in a coastal–shallow marine environment, with the detritus sourced from the northern Indian passive margin. The upper Eocene Pengqu Formation was deposited in a deltaic environment, with its detritus sourced from the Gangdese arc and the Yarlung–Tsangpo suture zone at the active continental margin. Combined with the nearshore subaqueous fan branch channel of the Jidula Formation and the slump deformation of the Zongpu Formation, the Palaeocene–Early Eocene southern Tethys Himalaya in the Tingri area was located in the forebulge of the peripheral foreland basin. The marine–continental interactive delta of the Pengqu Formation and its provenance from the Gangdese magmatic arc indicate that the Tingri area was situated in the foredeep of the peripheral foreland basin during the Late Eocene. The study provides valuable insights into the collisional orogenic processes between the Indian and Eurasian plates. [ABSTRACT FROM AUTHOR]

The northern continental margin of the South China Sea (SCS) is an important component of deep‐water circulation, providing excellent conditions for studying bottom currents in a marginal sea. Seismic data were employed to discern the sedimentary patterns prevalent in the deep‐water continental slope sediments on the northern continental margin of the SCS, encompassing gravity flow, contourite and mixed depositional systems. The contourite depositional system includes various types of deposits (such as separated mounded drifts, patch or channel‐related drifts, deformed sheeted drifts, composite drifts, bottom current sediment waves, plastered contourite drifts) and various morphologic erosional features eroded by the bottom current (such as moats, non‐depositional surfaces, troughs and scarps). These contourite features are related to the continental slope's morphology and its sources. The Dongsha slope exhibits distinctive characteristics marked by intense bottom current erosion and deposition, featuring separated mounded drifts and deformed sheeted drifts along its lower slope. The lower slope of the Pearl River showcases a spectrum of bottom current‐induced features, including sediment wave fields, erosion fields and contourite drifts. The southern flank of the Shenhu slope is characterised by a bottom current erosion field, a non‐depositional surface, a sediment wave field and isolated mounded drifts. On the Yingqiong slope, the contourite drifts are limited to its southern flank where gravity flow action is absent, and the complex geomorphology interacts with the bottom current, forming a complex contourite depositional system. The results of this study serve as a foundational framework for further global research on bottom current circulation and hydrodynamics. [ABSTRACT FROM AUTHOR]

We present significant findings of the Kausani Granite Gneiss within the Inner Lesser Himalayan Sedimentary Zone (iLHSZ) just north of the North Almora Thrust (NAT). The Kausani Granite Gneiss body lies within the quartzite of the Someshwar Formation and has a tectonized contact and a discordant relationship on the north side. Detailed seismic profiling across the body also confirms a similar result. Cathodoluminescence images of zircon from the Kausani body show no inheritance of older cores. The U–Pb ages from the zircon populations separated from the Kausani body give a crystallization age of 1866 ± 3 Ma. Along with the Upalda granite gneiss and Toneta granite gneiss near the Alakhnanda Thrust in the Garhwal Himalaya and the Dungeshwari granite gneiss near the Dailekh Thrust in Nepal, the Kausani Granite Gneiss north of NAT Kumaun Himalaya forms a major terrain boundary. These gneissic bodies mark the southernmost extent of felsic magmatism at NAT, rather than the Main Central Thrust. An about 1.8 billion years‐old magmatic event in the LHSZ suggests that it is a currently active continental margin inside the 'Greater India' region, now situated in the Himalayan domain. However, the Pb‐loss modelling of the U–Pb zircon data reveals thermal events during the Himalayan Orogeny (~45 Ma). [ABSTRACT FROM AUTHOR]

Whether the Yangtze Block was involved in the global late Mesoproterozoic orogeny remains contentious. The Mesoproterozoic Huodiya Group exposed in the Hannan‐Micangshan Massif on the northwestern margin of the Yangtze Block could provide sufficient evidence to further clarify the regional tectonic affinity. However, quantitative insights into the depositional age, provenance and basin tectonic setting of the Huodiya Group still lack comprehensively constraining. This study presents a combined analysis of zircon U–Pb dating for meta‐sedimentary rocks of the Shangliang Formation of the upper Huodiya Group and intruded gabbroic dykes. Intergraded dating results constrain the late Mesoproterozoic maximum depositional age at ca. 1050 Ma. Ca. 900 Ma formation age for the intruded gabbroic dyke, plus the minimum formation age of the overlying Xixiang Group at ca. 950 Ma, further suggests its deposition should be prior to ca. 950–900 Ma. Concordant detrital zircon ages define pronounced age clusters of ca. 2229–1741 and 2950–2388 Ma and few age populations of ca. 3232–3082 and 1069–1033 Ma, consistent with the tectonothermal events in proximal domains at the northwestern and northern Yangtze Block. Detrital zircon age distribution patterns and cumulative curves, coupled with the stable carbonate platform and shallow‐marine facies sedimentation, suggest a passive continental margin setting for the Huodiya Group on the Yangtze Block margin at the late Mesoproterozoic. Comparative insights into the contemporaneous passive continental margin from north to southwest argue against the existence of a late Mesoproterozoic orogeny along the exterior periphery of the Yangtze Block. [ABSTRACT FROM AUTHOR]

During the formation and evolution of the South China Sea, a series of multiscale submarine geomorphologies have been produced in the continental margin. The obvious submarine canyons and channels are widely distributed in the continental shelf and slope of the South China Sea. In the Taixinan Basin, several submarine canyons and channels termed as the Taixinan canyon‐channel system (TCCS) are distributed between the active and passive continental margins. Based on acquired ship‐borne multi‐beam bathymetry data in this study and the global GEBCO 2023 bathymetric dataset, we identify and define nine submarine canyons and seven submarine channels in the Taixinan Basin. The TCCS consists of the Dongsha, Taiwan, Jiulong, West Penghu, Penghu, Kaoping, Shoushan, Kaohsiung and the Fangliao canyons and submarine channels. The detailed geomorphological features of different submarine canyons and channels within the TCCS are analysed and summarized using multi‐beam bathymetry data and seismic reflection profiles across canyons. Based on the slope variations of the continental margin and the effects of turbidity currents and bottom currents on canyon, we propose a three‐stage evolutionary model of the TCCS. In the initial formation stage of canyon, the initial erosional grooves were created by tectonic activity on the continental slope and it represents the foundation of submarine canyons. During the growth and development stage, the submarine canyons are further evolved and the canyons began to deepen and widen from the continental slope to the deep‐water areas. It shows the weak erosion and sediment infilling within the canyons in this stage. On the northern continental slope of the South China Sea, continuous transportation and erosion of sediments led to the initial formation of grooves and it becomes the embryonic stage of submarine channels. The present stage of the TCCS was formed when the initial grooves on the continental slope have further developed and rebuilt under the erosion by the turbidity current and the scouring by the bottom current. In the last stage, the intense erosion by the turbidity current is supported by sediment waves around the submarine canyons and the migration of canyons is suggested by the cyclic steps formed within some canyons. [ABSTRACT FROM AUTHOR]

Voluminous Neoproterozoic intermediate to felsic rocks intruded the Neoarchean Douling Complex in the South Qinling Belt of Central China, which may provide new constraints on the controversial issue about the nature of the continental margin of the Yangtze Block during the Neoproterozoic. This study presents zircon U–Pb geochronology, whole‐rock geochemistry and Sr–Nd isotope of the Douling dioritic–granodioritic–granitic intrusion, aiming to clarify its petrogenesis and tectonic significance. The dioritic–granodioritic–granitic rocks yield similar zircon U–Pb ages ranging from 735 to 705 Ma. The enrichment of light rare earth elements (LREEs) and large‐ion lithophile elements (LILEs), and depletion of high‐ field‐strength elements (HFSEs) (e.g., Nb, Ta) are typical features of arc magmatic rocks. The whole‐rock Sr–Nd isotopic compositions show initial 87Sr/86Sr ratios ranging from 0.7034 to 0.7059, and εNd(t) values from −7.3 to −1.4. Elemental and isotopic data suggest that the Neoproterozoic dioritic–granodioritic–granitic rocks were co‐genetic and were generated by partial melting of lower crust materials combined with mantle‐derived melts. The granites were the derivative product of dioritic rocks by fractional crystallization of amphibolite, plagioclase, mica and zircon. Combined with literature data, we infer a subduction‐related setting for the northern margin of the Yangtze Block during the Middle Neoproterozoic, and a tectonic model of accretion along an Andean‐type active continental margin after the collision of the Douling micro‐block with the northern Yangtze Block is further proposed. [ABSTRACT FROM AUTHOR]

The crystal‐poor rhyolitic pumice is the product of extreme magma differentiation and is characterized by highly vesicular, honeycomb‐like structure. However, little is known about the evolutionary history and the time of volatile saturation of the pumice‐forming melt. A crystal‐poor rhyolitic pumice (TVG7‐1) has been collected from the Yoron Hole hydrothermal field in the middle Okinawa Trough, a young continental margin back‐arc basin in the western Pacific. This study conducted a detailed analysis on the texture and in situ chemical composition of plagioclase, orthopyroxene and Fe‐Ti oxides to reveal the evolution process, storage state and eruption triggers of eruptible silicic melt. Texture and zoning of specific minerals and mineral populations suggest a magmatic evolution history of open system. Additionally, the hollow reentrant texture, as well as results from plagioclase‐liquid hygrometers, confirm a water‐rich melt pocket. The exsolution of volatiles (H2O, etc.), in this melt pocket, will contribute to local oxidation conditions, which may have been recorded by the concordant behaviour of FeO and An in plagioclase. Then, the overpressure caused by volatile exsolution would destabilize the magma chamber, which will eventually be broken by magma mixing/recharge, and lead to violent melt evacuation. Consequently, crystal size distribution (CSD) provides a new perspective on understanding the kinetic effect of magma mixing/recharge in the Okinawa Trough, especially on the mineral populations. Our study reveals the petrogenesis of crystal‐poor rhyolite within the framework of the mush model, refines the magma evolution history and demonstrates that pumice magma reaches volatile saturation before the eruption. [ABSTRACT FROM AUTHOR]

Submarine geohazards significantly threaten human economic activities and essential infrastructure. Based on multi‐beam data and high‐resolution 2D seismic data, two types of submarine geohazards are identified: direct and indirect geohazards on the northwestern continental slope and the Xisha Uplift of the South China Sea (SCS). Direct geohazards include submarine landslides and active faults, while indirect geohazards include buried channels, submarine canyons, pockmarks, volcanoes and magma diapirs. This study comprehensively analyzes geomorphological features, including their characteristics, genesis and distribution. Statistical analysis reveals that the gradient of the Xisha Uplift slope is steeper than the shelf break, making it a more unstable region. However, assessing disaster potential indicates that submarine geohazards at the shelf break pose a greater threat than those at the Xisha Uplift. Many factors, including tectonic activity, sediment supply and relative sea‐level changes, influence submarine geohazards' formation. These hazards do not occur in isolation but often interact with one another. The research results provide a scientific basis for predicting deep‐sea geohazards near the northern continental margin and Xisha Island in the SCS. [ABSTRACT FROM AUTHOR]

This work presents the first pressure–temperature‐deformation‐time (P–T‐d‐t) path obtained for the Lower Units (Alpine Corsica, France) including the Tenda Massif that represent fragments of the European continental margin involved in the east‐dipping Alpine subduction. The new thermobarometric data applied to metapelites and the new 40Ar/39Ar dating of syn‐kinematic muscovite sampled from metagranitoids allowed us to define the P–T conditions and the age of the metamorphism of the Venaco Unit, a Lower Unit located in the southernmost sector of the Alpine Corsica. The outcoming scenario indicates that the Venaco Unit reached the baric peak at ≈ 33 km depth, not before Bartonian time. At 35.7 Ma (i.e., during the middle Priabonian), it was exhumed to a shallower structural level (i.e., at ≈ 26 km depth), mainly through the activation of the top‐to‐W shear zones. This retrograde path suggests that the Venaco Unit experienced fast exhumation, unlike the Tenda Massif which had been involved in subduction during the Ypresian and was stationary at 25–30 km, before its exhumation in the Priabonian. [ABSTRACT FROM AUTHOR]

Large‐scale magmatic activity and associated mineralization in South China are linked to the subduction of the palaeo‐Pacific Plate, although specific processes have remained controversial including the timing of subduction initiation and lithospheric extension. We present new geochemical data and zircon U–Pb and Lu–Hf isotope measurements on volcanic rocks, granites and mafic dikes from coastal south‐eastern China along the Eurasian continental margin. The biotite monzogranites show I–type granitoid affinity and fractional crystallization with zircon εHf(t) values ranging from −10.15 to +0.50, suggesting magma derivation from the melting of lower crust with the addition of juvenile crustal or mantle components. The biotite granites are typical of highly fractionated A‐type granites with εHf(t) values ranging from −3.63 to +1.35, indicating magma hybridization between anatectic granitic and mantle‐derived mafic magmas. The diabase dikes have zircon εHf(t) values ranging from −2.99 to +1.71, with high La/Nb and La/Ta ratios. This suggests derivation from partial melting of a lithospheric mantle metasomatized by fluid from a subducting–slab, with contributions of depleted asthenospheric mantle components. Our data, combined with those from previous studies, suggest that the shallow subduction of the palaeo–Pacific Plate beneath the Eurasian continent had begun by ca. ~170 Ma at least and the subduction orientation changed to oblique with respect to the continental margin. Steepening of the subduction angle likely caused a slab rollback during the Early Cretaceous, resulting in a tectonic transition from compression to extension in South China at ca. 145 Ma. [ABSTRACT FROM AUTHOR]

The recognition of unconformities is important for stratigraphic subdivision and correlation and for determining the timing of tectonic activity and the ocean‐continent transition process. Here, we have identified a Late Palaeozoic disconformity in the Moqinwula area of the northern Junggar Block, NW China. Integrated field relationship observations and sedimentological, biostratigraphical, geochemical and detrital zircon geochronological data, suggest that the underlying Hongliugou Formation is of Devonian age and was deposited in a passive continental margin setting. The overlying Tamugang Formation formed in the Early Carboniferous and was deposited in a foreland basin setting. Integrating the published data and our new work, we suggest a new tectonic evolution model related to the Karamaili ocean‐continent transition process. During the Early Devonian, northward subduction of the Karamaili Ocean plate beneath the East Junggar Belt formed the Yemaquan arc. At this time, a passive margin sequence was deposited on the northern Junggar Block. During the Early Carboniferous, the closure of the Karamaili Ocean resulted from the collision between the Junggar Block and the East Junggar Belt. Foreland basins subsequently developed, forming an extensive unconformity in the accretionary wedge to the north and a disconformity in the relatively rigid and stable Junggar Block to the south. This significant difference in stratigraphic contact relationships confirms that regional convergence‐induced shortening deformation had no significant influence on the northern margin of the Junggar Block, suggesting the existence of a relatively rigid basement, probably an oceanic plateau, under the cover sediments of the Junggar Block. [ABSTRACT FROM AUTHOR]

SE China is regarded as one of the most important mineral resource bases in China. The spatio‐temporal distribution of the magmatism and mineralization in the area has a distinct pattern due to the uneven intensity of crust–mantle interactions. We analysed gravity, magnetic and magnetotelluric (MT) data from the study area. The lithosphere in the north‐eastern and coastal parts of South China features intense magnetic, low resistivity anomalies and low density of lithospheric mantle material components. Meanwhile, the crust in the Nanling region features high resistivity and low magnetic granitic pluton. As we view from the north‐east to the south‐west, the crust–mantle interaction in SE China weakens unevenly and the magmatic origins for ore‐forming are progressively shallow. In the continental margin area, the subducted plate partially melted and rose along deep faults, interacting with the lithospheric mantle, which created conditions for the formation of the large porphyry Cu deposits. In the inland Nanling region, the Palaeo‐Pacific Plate has subducted to a considerable depth, the influence of deep disturbances was diminished, and therefore the metallogenic magmas of W–Sn deposits are dominated by continental crust remelting granites. While the tectonic environment of the Pb–Zn–Ag polymetallic deposits is in a transitional zone between porphyry Cu deposits and W–Sn deposits, small amounts of femic magma mixed with large amounts of granitic magma to form the mineralized granites. The geophysical data provide corresponding evidence to support the mineralization dynamics model based on oblique Pacific subduction. [ABSTRACT FROM AUTHOR]

Post‐collisional processes cause uplift and exhumation of the overthickened crust together with the formation of sedimentary basins. To determine the influence of post‐collisional processes on sedimentation, we investigated the Early Mesozoic Munamdong Formation of the Yuljeon Basin in the Korean Peninsula, deposited immediately after the orogenic events caused by the collision of the North China Block and South China Block. Facies analysis shows that the Munamdong Formation was deposited in a streamflow‐dominated alluvial fan under tropical/subtropical climatic conditions. Vertically, the Munamdong Formation exhibits a fining‐upward trend with changes in stacking patterns, from highly amalgamated channel conglomerates to floodplain fines, indicating a progressive increase in the creation of accommodation space exceeding sediment supply. Moreover, the types of gravels in the conglomerate beds and the petrographic characteristics of the sandstones suggest that the sediments were supplied rapidly from nearby Precambrian high‐grade metamorphic rocks and Triassic post‐collisional plutons. These results indicate the supply of sediment from restricted sources, implying that the drainage basins did not widen even during intermittent quiescence of basin subsidence. We interpret the fining‐upward trend and uniform composition of sediments to have resulted from rapid uplift and exhumation of the orogenic crust, together with rapid tectonic subsidence, possibly aided by post‐collisional magmatism. This study shows that the Munamdong Formation reflects a close connection between surficial sedimentation and post‐collisional tectonic processes. This study will help to fill the gap of understanding between deep crustal processes and post‐collision sedimentation with insight into the Early Mesozoic tectonic environment of the East Asian continental margins. [ABSTRACT FROM AUTHOR]

We present the whole‐rock and mineral chemical data of the Khasi meta‐mafic/basic‐trondhjemite intrusives (KMI) and meta‐tonalite‐trondhjemite (MTT) that coevally emplaced the Proterozoic Shillong Group (SG) of Shillong Plateau, northeast (NE) India and discuss their petrogenetic‐tectonic origin. The calc‐alkaline to tholeiite KMI are compositionally transitional between hornblende‐gabbro; hornblende‐diorite and minor‐hornblendite. They show Ta–Nb troughs and strong decoupling large‐ion lithophile/high field strength elements (HFSE) signature consistent with subduction zone‐related basic magmas. The calcic to calc‐alkaline, low‐Al2O3, and I‐type metaluminous Fe‐hedenbergite‐trondhjemite (KMT) exhibits similar trace and rare earth elements (REE) distribution to the KMI. The MTT on the other hand are depleted in trace elements and REE, and correspond with the I‐type granitoids, and are comparable to Proterozoic to Phanerozoic tonalite‐trondhjemite‐granodiorites. Gentle negative sloping of REE in KMI ([La/Lu]CN = 4.04 to 6.35) with moderate LREE, suggests partial melting or, fractional crystallization from a transitional source between garnet and spinel lherzolite. Although almost a flat pattern ([La/Lu]CN = 3.70 to 4.05) for MTT entails a high degree of partial melting from sources similar to Archaean Mafic Composite or Archaean Tholeiite. Trace elemental modellings ([Sr/Y] vs. Y and [La/Yb]N vs. YbN) for MTT infer low pressure (<15 kbar) and high degree partial melting of >50% in equilibrium with 10% garnet +90% amphibole residue. A relatively flat REE pattern with some elevated HREE of MTT compared to KMI suggests for depleted source. Bimodal plutonism and the prevalence of meta‐dacite‐rhyolite in SG invokes for tonalite‐trondhjemite‐dacite setting of a continental arc or, active continental margin tectonic setting. Emplacement of KMI initiated in a temporary relax‐extensional phase and MTT in a compressional regime. This is possibly caused by an over‐thickened crust later subjected to orogenic collapse, exhumation‐metamorphism, and decompressional melting. This event might have taken place between 1.0 to 0.5 Ga during the Pan‐African Orogenic crustal growth, linked to the amalgamation of Gondwana. [ABSTRACT FROM AUTHOR]

The Zhangguangcai Range is located in the junction zone of the Palaeo‐Asian and Palaeo‐Pacific tectonic regimes; Mesozoic igneous rocks in this area are considered to have been formed in an active continental margin, which is related to the western subduction of the Palaeo‐Pacific Plate beneath the Eurasian continent. However, the nature of the mantle wedge and related melting mechanism remains unclear. This paper reports zircon U–Pb data, whole‐rock geochemistry, and zircon Lu–Hf isotope for a Late‐Triassic high‐Mg andesite in the southern part of the Zhangguangcai Range. Zircons from the andesite yield a concordant 206Pb/238U age of 218.6 ± 3.3 Ma, which is contemporary with the diorite in the study area. The Lengshan high‐Mg andesite is characterized by moderate SiO2 (57.30–60.15 wt.%), high Mg# (61–67), Al2O3 (15.05–17.35 wt.%), (La/Yb)N (16.9–22.4), and variable Na2O/K2O (1.06–1.59). Its insignificant Eu negative anomalies (Eu/Eu* = 0.88–0.99) and high Sr/Y (68.4–96.4) may prove the existence of garnet or amphibole in the residual melt, where feldspar is more or less absent. The andesite is enriched in Rb, Ba and depleted in Nb, Ta, Ti, and other high‐field‐strength elements, with Nb/Ta ratios of 14.6–17.2, U/Th ratios of 0.28–0.31. In combination with its depleted zircon Lu–Hf isotopic compositions (e.g., εHf(t) = −0.48 to +13.1), it is proposed that the high‐Mg andesite formed by hydrous melting of the mantle wedge, which was metasomatized by slab‐derived adakitic melts. The subsequent assimilation of ancient crust results in the formation of some zircons with negative Eu*/Eu anomalies (0.05–0.1) and εHf(t) values (−13.8 to −18.5), which is approved by the relative evolved whole‐rock Sr–Nd isotopic compositions. [ABSTRACT FROM AUTHOR]

The Lower Congo Basin is a typical passive continental margin basin of West Africa and is currently the focus and hot spot of deep‐sea oil and gas exploration. Previous studies have focused on the deformation process and mechanism of the salt rock itself, but have ignored the interaction process between the faults and salt diapirs. The direct influence of the interaction process between the faults and salt diapirs on oil and gas exploration is reflected in the control of the reservoir distribution. In recent years, most of the oil and gas discovered in the Lower Congo Basin have been concentrated in the Oligocene–Miocene turbidite reservoirs, and the distribution of channel sand bodies is largely affected by supra‐salt tectonic activity. In this study, Block M in the Lower Congo Basin was selected for study. Based on the 3D seismic, drilling, and logging data, the typical structural styles and stress mechanisms were analysed. The 2D Move software was used to restore the tectonic evolution history and, based on this, established the interaction model of salt diapirs and faults, and summarized the action modes of diverse types of sedimentary channels. The research results are expected to lay the foundation for follow‐up studies on the laws of hydrocarbon accumulation. [ABSTRACT FROM AUTHOR]

The geochronology of tuffaceous sandstone and elemental geochemistry of mudstones in the Lower Permian Zhanjin Formation (well QZ‐5) in the Central Qiangtang Basin were studied to determine their depositional age, provenance, tectonic setting, and depositional conditions. Twenty‐six synchronous igneous zircons from tuffaceous sandstone at 596.5 m have a weighted average U–Pb age of 292.5 ± 2.5 Ma, tentatively constraining the sedimentary age of the Zhanjin Formation to the Early Permian. Low SiO2/Al2O3 and Th/Sc ratios indicate a low sedimentary recycling and compositional maturity for the source area of the Zhanjin Formation mudstones. The low Al2O3/TiO2, moderate‐high Fe2O3/Al2O3, high TiO2/Fe2O3, low‐moderate TiO2/Zr, and moderate Co/Th ratios combined with post‐Archean Australian shale‐normalized rare earth element distributions imply that the provenance of the Zhanjin Formation mudstones was mainly from the mixed mafic and felsic sources that is composed of basalt and rhyolite exposed in the Central Qiangtang Basin. The tectonic discrimination plots, low Fe2O3/TiO2, (La/Ce)N, and high Al2O3/(Al2O3 + Fe2O3) ratios reveal that the studied mudstones mostly formed in rift settings, consistent with the geologic evolutionary history of the Early Permian Qiangtang Basin. Trace element ratios (V/Cr and Cu/Zn), enrichment factors (MoEF), and δCe values combined with sedimentary features indicate that almost all the studied mudstones were deposited in an open marine environment along the continental margin, and were associated with oxic and dysoxic water columns. [ABSTRACT FROM AUTHOR]

The metasedimentary rocks of the South Liaohe Group are widely distributed along the Jiao‐Liao‐Ji Belt (JLJB) in eastern Liaoning Province. It is important to understanding tectonic setting and evolution of the JLJB by determining its sediment sources and properties of the provenances, sedimentary facies, metamorphic ages, and facies. After the detailed field geological surveys and comprehensive laboratory observation, many high‐grade metapelitic rocks are identified in the South Liaohe Group. The main rock type is sillimanite‐garnet‐cordierite‐biotite plagiogneiss. The zircon U–Pb geochronology of three samples shows that these high‐grade meta‐pelitic rocks are mainly derived from the Liaoji Granites and the Archean basement. The protolith formation ages are between 2.00 and 1.93 Ga. Subsequently, these protolithes underwent high‐pressure metamorphism resulted from collisional orogeny, with peak metamorphism at ca. 1.88 Ga. Then, at 1.88–1.84 Ga, these rocks experienced the retrograde metamorphism and exhumed to the surface during crustal uplift. Geochemical data show that the protoliths are alumina‐rich claystones and graywackes with low maturity, implying near‐source sedimentation. The chemical index of alteration (CIA) values of these samples range from 60 to 80, indicating that the protoliths underwent moderate weathering. The sediment source was mainly felsic components of the upper crust, possibly with the addition of ancient sediments. Various tectonic environment discrimination diagrams combined with previous results on metamorphism and isotope chronology of these metasedimentary rocks in the JLJB indicate that the rocks in the study area originated from an active continental margin with an evolving island arc. [ABSTRACT FROM AUTHOR]

U–Pb dating and Hf isotopes of detrital zircons from the Nanhua System in Longsheng, northern Guangxi, were investigated to determine the depositional age and provenance of the Nanhua System and the early crustal evolution stages of the South China. U–Pb ages of detrital zircons from the Chang'an Formation of the Nanhua System in Longsheng, northern Guangxi, are mainly 0.66 ~ 0.72 Ga and 0.72 ~ 0.90 Ga, with εHf(t) ranging from −17.05 to 12.79. The dominant provenance is composed of Neoproterozoic magmatic rock from the southeastern margin of the Yangtze Block and the Nanhua period detrital material from Cathaysia Block. U–Pb ages of detrital zircons from the Fulu Formation can be divided into four major groups, that is, 0.64 ~ 0.72 Ga, 0.72 ~ 0.90 Ga, 1.80 ~ 2.20 Ga, and 2.30 ~ 2.80 Ga, with εHf(t) ranging from −27.66 to 11.68. The main provenance is Neoproterozoic magmatic rock from the southeastern margin of Yangtze Block, followed by the Nanhua period detrital material from the Cathaysia Block and geological body equivalent to the assembly of the Columbia Supercontinent. U–Pb age of detrital zircons from Lijiapo Formation is concentrated in 0.72 ~ 0.90 Ga, with εHf(t) ranging from −16.02 to 11.87, and the main provenance comes from Neoproterozoic magmatic rock in the south‐east margin of Yangtze Block. The second‐stage Hf model age (TDM2) of the Nanhua System is 0.84 ~ 4.51 Ga, with two obvious peak intervals of 0.90 ~ 1.30 Ga and 1.40 ~ 2.10 Ga, and two secondary peak intervals of 2.40 ~ 3.00 Ga and 3.10 ~ 3.60 Ga, which can be interpreted that the research area has experienced four stages of crustal growth: 3.10 ~ 3.60 Ga, 2.40 ~ 3.00 Ga, 1.40 ~ 2.10 Ga, and 0.90 ~ 1.30 Ga. The detrital zircon age spectra indicate that the Chang'an Formation and Fulu Formation of the Nanhua System contain more detrital zircons which is contemporaneous with strata due to the Xuefeng orogeny, while the Lijiapo Formation contains a very small amount of detrital zircon which is contemporaneous with strata, suggesting that the tectonic setting has shifted to a passive continental margin or pull‐apart basin during the period of the Lijiapo Formation. [ABSTRACT FROM AUTHOR]

The Indian Plate began drifting northward after the Gondwana breakup and collided with the Eurasian Plate during the Early Cenozoic, resulting in the consequential development of the Himalayan–Tibetan Orogeny. Several microcontinents were rifted from Gondwana and amalgamated with the Indian Plate, resulting in magmatism along the continental margin. The Abor volcanic rocks (AVRs) in the eastern Himalaya represent one of such magmatism, the emplacement mechanism, and the timing of which is still a topic of debate. The AVR comprises mafic and silicic rocks; the present study concerns the petrography and geochemistry of the mafic rocks. U–Pb geochronology on three samples shows the weighted mean age of 130 ± 1 Ma, 143 ± 1.2 Ma, and 155 ± 16 Ma. Whole‐rock geochemistry of eight samples shows Mg# of 45.48 to 57.7, except for one sample with 37.4, variable contents of CaO (4.4–9.5 wt%), K2O (0.1–2.6%), Lost on ignition (LOI) (0.9–3.6 wt%; average 2.4), and K2O/Na2O ratios (0.02–0.6 with a single one 1.0), Y/Nb (0.55–1.66, with one value of 2.44), and medium to high Zr/Nb (10.1–14.1) and Zr/Y (5.4–18.14). The Sr‐isotopic results from 11 samples show that the initial 87Sr/86Sr ratios vary between 0.7049 and 0.7110, and εNd(t) values range from +1.176 to −2.250. Geochemical and isotopic data suggest that the studied AVRs (mafic) are of subalkaline tholeiitic affinity. These volcanic rocks have continental intraplate characteristics and are sourced from the metasomatized mantle during the rifting event of the Indian subcontinent from Gondwana during Late Jurassic to Early Cretaceous. [ABSTRACT FROM AUTHOR]

This paper studies the major, trace, and rare earth elements (REEs) in fluvial sediments from the Yarlung Zangbo River (YZR) on the Tibetan Plateau, China, with the aim of investigating their provenances, sediment maturity, weathering conditions, and tectonic settings. All samples and analytical techniques are based on Environmental Geochemical Monitoring Networks, which are a crucial part of IGCP259/360 (Global Geochemical Baseline). The results show that the YZR sediments consist of greywacke and litharenite with low‐moderate maturities of textures and minerals. The chemical index of alteration (CIA) (49–71), plagioclase index of alteration (49–77), and index of compositional variability (ICV) values (0.82–1.54) indicate that both mature and immature sediments are present in the YZR and have experienced weak to moderate weathering with little intense weathering in the source area, which is also confirmed by the ICV‐CIA, A‐CN‐K, A‐CNK‐FM, and MFW plots. Moreover, the provenance discrimination diagrams suggest that the YZR sediments are predominantly derived from felsic rocks that are close to the upper continental crust and from acid intermediates, and the tectonic settings of the YZR source rocks were associated with active continental margins and continental island arcs. The overall sediment types, weathering conditions, and tectonics of the YZR were consistent with those of the Brahmaputra River and Meghna River during the Himalayan–Tibetan orogeny, while the sediments of the Brahmaputra River are characterized by recycled‐quartzose sources when compared with the other two Himalayan rivers due to the contributions of quartzolithic composition. [ABSTRACT FROM AUTHOR]

Newly recognized Late Carboniferous volcanic rocks occur in Ongniud Banner on the northern margin of the Sino‐Korean palaeoplate, including rhyolite, dacite, and related volcaniclastic. The volcanic rocks have for a long time been considered to form in the Early Permian. Our new LA‐ICP‐MS U–Pb zircon dating of two rhyolite samples and one dacite sample yielded ages of 305.6 ± 1.6 Ma, 312.2 ± 2.3 Ma, and 305.3 ± 1.7 Ma, respectively, corresponding to the Late Carboniferous. The volcanic rocks are enriched in light rare earth elements (LREEs) and large‐ion lithophile elements (LILEs) and depleted in heavy rare earth elements (HREEs) and high‐field‐strength elements (HFSEs, e.g., Nb, Ta). The positive zircon εHf(t) values (+6.64 to +9.49) of the volcanic rocks and the high Mg# values (47.05–51.47) of some samples indicate the contribution of mantle materials to the sources. Integrated with geological, geochemical, and Lu–Hf isotopic studies, it is considered the volcanic rocks formed in a subduction‐related continental margin arc setting. Combined with the studies in the southeastern part of the Central Asian Orogenic Belt on the ophiolitic mélanges, magamatic belts and sedimentary environment of the Late Palaeozoic, collision‐related granites, and so on; it is suggested that the southward subduction for the eastern segment of the Palaeo‐Asian Ocean beneath the northern margin of Sino‐Korean palaeoplate was still occurring in the Late Carboniferous. [ABSTRACT FROM AUTHOR]

Zircon (ZrSiO4) trace elements are commonly used to distinguish the tectonic settings of their host rocks. The Chinese Altay is a key area for deciphering the accretionary history of the Central Asian Orogenic Belt (CAOB), and its tectonic setting during the Devonian is debated. In this study, we describe the systematic investigations of the magmatic and metamorphic rocks from the Qiemuerqieke and Qinghe areas situated to the west and east of Southern Altay, respectively. In doing so, we present the first attempt to elucidate the Devonian tectonic setting of the Southern Altay based on zircon trace elements. Zircon U–Pb geochronological studies on the magmatic and metamorphic rocks in Southern Altay yielded ages of 395–360 Ma, which indicate that these metamorphic rocks formed in the Devonian rather than the Precambrian. Furthermore, most of the zircons from these rocks were concentrated in the arc‐related orogenic setting of the discrimination diagrams of Th/U versus Nb/Hf and Th/Nb versus Hf/Th, and in the continental field of the discrimination diagrams of Yb versus U, Hf versus U/Yb, Y versus U/Yb, and Nb/Yb versus U/Yb. These results are consistent with the geochronology and whole‐rock geochemistry of Devonian granitoids in Southern Altay. Therefore, we propose that the continental arc along the Southern Chinese Altay was triggered by the active continental margin of the Altay‐Mongolian Terrane during the Devonian. [ABSTRACT FROM AUTHOR]

The crystalline basement of Cathaysia Block is commonly believed to have formed before the Middle Neoproterozoic; however, the basement rock has seldom been reported in the eastern Cathaysia. Recently, numerous siliceous and femic rock blocks distributed in the diatexitic host granite were observed on the rocky beach of Fuhu Hill in the southwestern Guangdong, China. The results of geological and geochemical investigations of these rock blocks revealed that the protolith of siliceous rock blocks (SRBs) was marine silicalite deposited in a pelagic environment between the ridge‐proximal and continental margin, and the femic rock blocks (FRBs) geochemically corresponded to trachybasalt and monzogabbro, pertaining to OIB/E‐MORB types in the Ce/Y‐Zr/Nb and Zr/Y/Nb systems. 206Pb/238U ages of 995 and 1,002 Ma were obtained from zircon U–Pb dating of the FRBs. The host rocks of the SRBs and FRBs were mainly diatexitic granite that was intruded and sometimes hosted by massive granite. The zircon 206Pb/238U age gained from the diatexitic granite was 991 Ma whereas that from the massive granite was 239 Ma. It may be concluded that SRBs and FRBs were derived from a spilite‐keratophyre formation formed during 1,005–995 Ma and disintegrated around 991 Ma due to crustal anataxis. These SRBs, FRBs, and their diatexitic host granite blocks might have been brought up to the shallow crust by granitic magma in the Indosinian period or due to fault activity in the late stage. Moreover, the southwest part of the eastern Cathaysia possessed a similar basement as the western Cathaysia. [ABSTRACT FROM AUTHOR]

A series of tectonic activities induced by the subduction of the Palaeo‐Asian Ocean (PAO) in the Palaeozoic have been recorded in the North China Craton (NCC). Sedimentary strata provide some precious records to reconstruct the basin evolution in the NCC. In this study, we carried out detrital zircon LA‐ICP‐MS U–Pb dating, sandstone modal analysis, bulk‐rock major, and trace elemental measurements for the Sunjiagou and Liujiagou formations in the eastern Ordos Basin to trace the material source. The results show that the sedimentary rocks were mostly sourced from active continental margins. The detrital zircon ages of the Sunjiagou and Liujiagou formations spread from >3,000 to 250 Ma with peaks of main age populations at 2,508, 1,890, 430, and 270 Ma. Based on the age comparison and the southward palaeocurrents, we consider that the source material of these sedimentary rocks comes from the northern margin of the NCC. This in turn indicates that the amalgamation of the PAO and the NCC should have finished at least by the end of the Late Permian. [ABSTRACT FROM AUTHOR]

Geochemical characteristics of sedimentary rocks play an important role in indicating depositional environments and tectonic backgrounds. In this article, the major and trace elements of the Daohugou Formation are measured, which shows that the quartz and silicate minerals are abundant; trace elements, except for Rb, are depleted than that of the upper crust; the rare earth elements (REE) curves incline to the right with Eu negative anomaly and slight Ce negative anomaly. The Daohugou Formation is continental deposits with freshwater and oxic conditions, and the climate changes from warm and humid to hot and dry. The source rock of the Daohugou Formation is granite which experienced an intermediate chemical weathering under wet and warm conditions, and the tectonic background of the Daohugou Formation is a passive continental margin. It is deduced that the provenance of the Daohugou Formation is Archean gneiss in the south of the Daohugou Basin. [ABSTRACT FROM AUTHOR]

The structural setting and tectonic evolution of the Marguareis Massif (located at the boundary between the Maritime and Ligurian Alps) has long been matter of debate. After new meso‐ and micro‐structural studies and field investigations, the tectonic unit interplay outlines a finite structural architecture more complex than that proposed in previous interpretations. We depict a stack of Briançonnais Units stemming from the Europe continental margin, and the Helminthoid Flysch Unit, detached from its original basement whose original palaeogeographic domain is still a matter of debate. Our results highlight for the first time that each unit recorded different pre‐stacking folding events progressively developed at different structural levels. The events occurred during the stacking of the units produced shear zones with top‐to‐SW sense of movement. After the syn‐stacking tectonics achieved during the Late Eocene‐Early Oligocene collisional events, the whole stack recorded the same post‐stacking deformation history here represented by a fold system with sub‐horizontal axial planes and faults. Similar tectonic evolution was documented in other sectors of the Western Alps by previous authors. [ABSTRACT FROM AUTHOR]

The Middle Triassic succession of the Sichuan Basin contains key information about the Early Indosinian Movement, during which it has changed from extensional to compressional. In order to clarify the relationship between the evolution of the Sichuan Basin during the Indosinian Movement, the Middle Triassic tectonostratigraphic environment should be determined. Detailed stratigraphy and facies analysis integrated with structural and basin analysis, allowed a full reconstruction of the tectonic and depositional environments for the Middle Triassic strata of the Sichuan Basin. Six facies associations from two rock systems of: (a) carbonate–evaporite system and (b) a mixed carbonate–siliciclastic system, were characterized. Four depositional stages highlighted by the lithostratigraphic members of the Leikoupo (Lei) and Badong (Ba) formations were divided: (a) stable subsidence and deposition of the Lei‐1/Ba‐1 Member, leading to an embryonic 'uplifts and sags' configuration; (b) inherited deposition of the Lei‐2/Ba‐2 Member, with the platform margin belt extended; (c) rapid deposition of the Lei‐3/Ba‐3 Member, characterized by an eastward shift of the depositional centre and formation of the central anhydrite‐rich lagoon; and (d) intensification of cratonic tectono‐sedimentary differentiation during the Lei‐4/Ba‐4 deposition, that resulted in subaerial exposure along the Luzhou–Kaijiang uplift zone and a hydrodynamically restricted depression along the western platform. The Middle Triassic tectonic framework of the Sichuan Basin was dominated by compression in the east and extension in the west. The western margin was a passive continental margin, inheriting an early rifting event, while the eastern area within the craton showed an 'uplift‐sag' pattern, which is a response to intracontinental tectonic movement of the Xuefengshan uplift belt. The basin evolved from incipient low‐relief uplifts and sags within the intracratonic depression to subsequent isolated foreland and restricted depression during the Middle Triassic. [ABSTRACT FROM AUTHOR]

Rare earth elements (REEs) record a large amount of geological information, and serve as a good geological indicator that can effectively predict the palaeoclimate, palaeoenvironment, and palaeotectonic evolution of the sedimentary rocks. The REEs and major elements of 94 marine shale samples obtained from the Late Ordovician to the Early Silurian at Shuanghe (SH) and Qiliao (QL) sections in Sichuan Basin were analysed in this study. Results showed that the major elements of Al2O3, K2O, and TiO2 were mainly controlled by clay minerals associated with terrigenous detrital, but the SiO2 and Na2O were not influenced by clay minerals. In addition, ΣREE values obtained at Shuanghe and Qiliao sections during the Late Ordovician–Early Silurian were close to those of North American Shale (NASC) composites (173.2 ug/g). REEs were characterized by light rare earth elements enrichment, but heavy rare earth elements depletion. Furthermore, the NASC‐normalized REE patterns were similar with a little difference at Shuanghe and Qiliao sections. The following conclusions were drawn by studying REE indicators associated with source, redox condition and the mechanism of organic matter enrichment: (a) ΣREE showed strong positive correlations with TiO2, Al2O3, K2O, and Na2O, but exhibited relatively poor correlations with Fe2O3 and P2O5. These results suggested that REEs in the marine shale mainly occurred in clay minerals, but also were influenced by pyrite, phosphates, and other minerals. (b) Ce/Ce* showed that marine shale during the Late Ordovician–Early Silurian was mainly deposited under anoxic condition in Sichuan Basin and the reduction intensity at Qiliao section was stronger than Shuanghe section. (c) The diagram between La/Yb and ΣREE and the Ce/Ce* values indicated that the detrital minerals in the marine shale were mainly derived from the sedimentary rocks and deposited in the same continental margin environment with a complex composition. (d) The controlling factors of organic matter enrichment were different at Shuanghe and Qiliao sections and the depositional environment controlled the organic matter accumulation and preservation of the organic‐rich marine shale. [ABSTRACT FROM AUTHOR]

Submarine landslide is a widespread marine geohazard and an important part of the global 'source to sink' system. In this article, multi‐channel seismic and topographic data are utilized to investigate the distribution, calculate the geomorphologic parameters, and discuss the genesis of the submarine landslides in the northeastern South China Sea. In the study area, which can be divided into two tectonic provinces: passive continental margin province and accretionary wedge province, 101 landslides are identified, with a total size of 2,358.22 km2. Statistics show that most landslides are of small sizes (<15 km2) and developed along small slope gradient regions. There is a high correlation between the slope gradient and the ratio of headscarp height to runout distance. The size and runout distance of landslide also correlate well. However, there is a low correlation coefficient including slope gradient versus runout distance and slope gradient versus size. The distribution of submarine landslides is consistent with that of bottom simulating reflections (BSRs) and seabed activities, which may imply a possible inner correlation among them. The calculated base of gas hydrate stability zone (BGHSZ) pinches out the seafloor at about 555–556 m below the sea level, where most of the landslide headscarps are located. And the BGHSZ depths are often shallower than the BSRs bottom depths in the upper slope area. Combined with previous studies, we consider that the influence factors of submarine landslides in the study area are earthquakes, canyons, seabed fluid activities, and gas hydrate dissociation. Gas hydrate dissociation is a global influence factor in the study area. In the passive continental margin province, the submarine landslides are mainly canyon‐associated landslides. While in the accretionary wedge province, they are mainly controlled by seabed fluid activities and earthquakes. [ABSTRACT FROM AUTHOR]

The south‐east margin of the Xing'an–Mongolian Orogenic Belt (SM‐XMOB) is a tectonic junction that is characterized by widespread Late Palaeozoic to Early Mesozoic igneous rocks. To determine the tectonic settings and provide new constraints on the regional tectonic evolution, petrological, geochronological, geochemical, and Hf isotope analyses have been conducted on the Permian volcanic rocks along the SM‐XMOB. Zircon U–Pb geochronological data indicate that these rocks were formed at 271.4 ± 3.2 Ma and 268.3 ± 3.2 Ma during the Early–Middle Permian. Geochemical results suggest that the volcanic rock samples have 61.5–66.4 wt% SiO2 and 0.98–1.71 wt% MgO, and belong to the calc‐alkaline series, suggesting an affinity with fractionated I‐type granite. They also exhibit positive zircon εHf (t) values ranging from + 8.6 to + 14.7, indicating that the primary magmas were dominantly derived from partial melting of Early Palaeozoic juvenile lower crustal. These volcanic rocks show an enrichment in large‐ion lithophile elements (LILEs; e.g., Rb, Th, and U) and depletion in high‐field‐strength elements (HFSEs; e.g., Nb, Ta, Ti, and P), similar to that from an active continental margin setting. We therefore propose that the widespread Permian volcanic rocks in the SM‐XMOB were closely associated with the southward subduction of the Palaeo‐Asian Ocean (PAO) Plate to the lithosphere beneath the XMOB, and that the PAO had not closed prior to the Middle Permian in the SM‐XMOB. [ABSTRACT FROM AUTHOR]

Important geological events that influenced the global environment occurred during the mid‐Cretaceous period. Dramatically increasing temperatures not only triggered oceanic anoxic events (OAEs) but also led to the aridity of terrestrial environments in East Asia. This study provides evidence for the aridity of a terrestrial East Asian environment during the mid‐Cretaceous and provides an example of the influence of the Cretaceous greenhouse climate on a terrestrial lake system in correspondence with the OAE 1a event. Palaeosalinity indexes (B, B/Ga, Sr/Ba, and Couch's palaeosalinity) and palaeoclimate proxies (Sr/Cu, Rb/Sr, Al2O3/MgO, and clay mineral compositions) of shale and mudstone from the Laiyang Group of the Jiaolai Basin in Eastern China were analysed. The results demonstrate that the palaeoclimate in the Wawukuang Formation was relatively warm and humid but became extremely dry and hot in the Shuinan Formation during the OAE 1a event before becoming warm and humid again in the Longwangzhuang and Qugezhuang formations. As a result, the palaeosalinity of the Jiaolai Basin increased from 4% in the Wawukuang Formation to 30% in the Shuinan Formation before decreasing to 0.48% in the Longwangzhuang and Qugezhuang formations. The following conclusions are from combining the distributional characteristics of the saliferous strata and its palaeontology, the palaeogeographic background, and the aeolian sandstone in eastern China. (a) The East Asian continental margin was influenced by the Cretaceous greenhouse climate, which resulted in the salinization of the Jiaolai Basin. (b) The significant increase of the palaeosalinity in the Shuinan Formation was an effect of the OAE 1a event on the terrestrial lake system, which further suggests the OAE 1a event was global. (c) Influences of the hothouse climate on the continental lakes changed the palaeosalinity of the water bodies. [ABSTRACT FROM AUTHOR]

Cherts, radiolarites, and radiolarian cherts are one of the most important components of accretionary complexes, and much used in the reconstruction of imbricated sections of ocean plate stratigraphy, and of the palaeogeographic and tectonic settings of ophiolitic mélanges. There has been little research on radiolarian cherts in the Kyrgyz South Tianshan, and the tectonic setting and temporal framework of the South Tianshan ocean are controversial. Here, we report well‐preserved radiolarians in ribbon‐bedded cherts in an ophiolitic mélange of the Atbashi accretionary complex (South Tianshan, Kyrgyzstan), which provide key evidence of ambient Palaeozoic oceanic conditions. The hydrofluoric acid technique was used to extract from the cherty rocks siliceous radiolarian, which yielded an age of late Early Carboniferous. Analyses of major, trace, and rare‐earth elements of four cherts indicate they are biogenic and deposited with little hydrothermal influence in a hemipelagic to continental margin environment. Our fossil ages and geochemical results of the radiolarian cherts from the Atbashi accretionary complex indicate that the South Tianshan ocean was still open in the Late Carboniferous, implying that it was a wide, long‐lived, major ocean that closed by northward subduction. [ABSTRACT FROM AUTHOR]

We carried out an integrated study of zircon U–Pb geochronology, Hf isotopes and geochemistry on the paragneisses and amphibolites from the Chencai area, South China. The detrital zircon ages of four paragneisses range from 2974 to 501 Ma with the main peak at ca. 820 Ma. The detrital materials with Neoproterozoic age may derive from the Jiangnan Orogen and those of Palaeo–Mesoproterozoic age may come from the Wuyi terrane. The youngest age indicates that the protoliths of the paragneisses were formed after ca. 501 Ma. The εHf(t) values (−20.6 to +20.9) of the detrital zircons suggest that the detrital materials of the protoliths are composed of old crustal and juvenile materials. The geochemical characteristics suggest that the protoliths of the paragneisses are greywackes, which formed in an active continental margin or continental island arc environment. The metamorphic ages of the three amphibolites are 428 ± 4, 430 ± 4, and 438 ± 3 Ma. The protoliths of the amphibolites are tholeiites, which can be divided into two groups. Group 1 is characterized by low ∑REE contents and (La/Yb)N ratios showing left‐inclined REE patterns and Nb, Ta depletion which resembles N‐MORB. Group 2 has higher ∑REE contents and (La/Yb)N ratios, with Eu negative anomalies showing affinity to E‐MORB. The data show that the Chencai Group is composed of oceanic crust remnants and continental crust materials, indicating it should be a subduction accretionary complex rather than a metasedimentary sequence and thus it cannot be regarded as the Precambrian basement of the Cathaysia Block. [ABSTRACT FROM AUTHOR]

The Cenozoic evolution of SE Asia is marked by thousands of kilometres extension on the continental margin, including normal faults, half‐grabens, and volcanic rocks, but dating of brittle faults in the shallow crust is difficult because of a lack of synkinematic minerals. The Cenozoic extension in the Youjiang fold‐thrust belt in southwest China is marked by brittle normal faults and half‐grabens filled with Paleogene sediments in the region. Here, we identified a strongly weathered mafic sill that was truncated by normal faults in the fold‐thrust belt and present the age and chemistry of zircons from a weathered sill. The zircons from the sill yielded a mean age of ~35 Ma. Integrating cross‐cutting relationship and zircon U–Pb dating suggest that the Cenozoic extension was initiated later than ~35 Ma in Youjiang fold‐thrust belt in southwest China. Combined with structural analysis and previous fission track data in the region, we suggest that the normal faults in this study provide evidence of surface fault activity of Cenozoic extension in SE Asia caused by retreat of a trench system. Furthermore, this study provides a case study to discuss how to decipher brittle normal faulting using zircon geochronology and structural and textural analysis from the mesoscale to the microscale. [ABSTRACT FROM AUTHOR]

Sedimentological study into the architecture of continental margins reveals its importance in predicting the partition of sediment budget between the shelf and the deep‐water settings. The sediment delivery towards the deep‐water basin during sea‐level lowstands can be hindered along rift margins. Here we use a 2D seismic survey from the northern Okinawa Trough to identify a set of clinoform seismic units elongating along the western slope, where the rifting activity occurred later than the late Pleistocene. The clinoform units are interpreted as a shelf‐margin delta complex based on the following observations: (a) the sediments clearly prograde across the eroded paleo‐shelf on the dip‐oriented sections; (b) there is some negative relief along two extensively traceable reflections, indicating the probable existence of paleo‐channels working as the potential pathways of sediment delivery for the shelf‐margin deposits; and (c) an eroded surface is easily recognized in the seismic data, possibly marking the sea‐level lowstand during which the shelf‐margin delta formed. The oxygen isotopes of the core QZ01 are taken as a proxy for the variation of the relative sea level and indicate its fast fluctuation in the past 180 kyr. We interpret how the shelf‐margin delta evolved during the late Pleistocene and propose that the subsidence and the rift faulting lead to the starvation of sediments near the shelf edge. As a result, there could be more sediments depositing along the active rift margin, while few of them would be transported to the deep‐water basin and re‐deposit as turbidites. [ABSTRACT FROM AUTHOR]

Devonian is a critical period for reversal of arc polarity and transition of continental margins from passive to active settings in the northern margin of the North China Block (NCB). However, the evolution processes during this period are still poorly constrained due to limited distributions of Devonian magmatism and sedimentary records in the NCB. In this paper, we present new zircon U–Pb geochronological, whole‐rock geochemical and Sr–Nd–Hf isotopic data of some recently identified Devonian volcanic rocks from the Jiefangyingzi area in the northeastern margin of the NCB. The Jiefangyingzi volcanic rocks display a bimodal composition and consist predominantly of amphibolite (meta‐basaltic andesite) and meta‐rhyolite and rhyolitic tuff with minor meta‐andesite. New SHRIMP and LA‐ICP‐MS zircon U–Pb dating results show that the volcanic rocks erupted during the early‐middle Devonian period (397–389 Ma). Geochemical and Sr–Nd–Hf isotopic data indicate that the mafic‐intermediate components were mainly derived from an enriched lithospheric mantle source, and the parental magma experienced fractional crystallization during magma ascent. The felsic rocks were mainly originated by partial melting of ancient lower continental crust, with mixing of some mantle‐derived mafic magmas. The occurrence of Devonian bimodal volcanic rocks, combined with the Devonian alkaline magmatic belt, suggesting that the northern margin of the NCB was a post‐collisional extension environment during the early‐middle Devonian period. In addition, the Sr–Nd–Hf isotopic results of the Devonian felsic volcanic rocks suggest that the Jiefangyingzi area is located in the North China Craton (NCC) rather than the Bainaimiao arc belt, and the orogen‐craton boundary between the northern NCC and Central Asian Orogenic Belt (CAOB) is located in some areas north to the Jiefangyingzi area. [ABSTRACT FROM AUTHOR]

The Okinawa Trough (OT) is a back‐arc basin located in the eastern edge of the Eurasian Plate. The stage of back‐arc spreading and the exact crustal thickness of the OT are still controversial. To determine the crustal nature and lithospheric structure of the OT, the Moho discontinuity depth of the OT is calculated through the Parker–Oldenburg iterative inversion method based on the Bouguer gravity anomaly data in this article. The result shows that the crustal thickness of the OT is 15–27 km, thinner than those of the typical continental crust, and thicker than those of the normal oceanic crust. In this study, the formation and evolution of marginal basins or back‐arc basins is divided into four stages based on the crustal thickness of the basin. By comparing crustal thickness and heat flow of typical marginal basins located in global passive continental margins and continental rift, it can be inferred that the OT is at a stage later than continental drift. We suggest that the southern and middle OT are at the early stage of back‐arc spreading, while the northern OT is still at the ocean–continent transitional stage. There may have been initial oceanic crust developed at the spreading center in the southern OT. The tomographic images of the OT show that there is low‐velocity anomalous mantle beneath the OT, providing deep geophysical evidence for back‐arc spreading of the OT. [ABSTRACT FROM AUTHOR]

The Mahanadi river basin (MRB) is one of the eight major fluvial basins of India. This paper presents a very first systematic study of geochemical characteristics, including rare earth elements of surface sediments collected from the riverbed at different parts of this basin to infer the chemical weathering, provenance, and tectonic settings. Lower mean values of major elements (except for SiO2 and K2O) are observed compared with that of the upper continental crust (UCC). It is attributed to the dominance of quartz and orthoclase in sediments and removal of mobile elements from the sediment during the transportation. The concentrations of Rb, Ba, Cu, Th, and Pb are elevated with respect to the UCC. The higher concentration of K2O and Rb, the ratio of Al2O3 to TiO2, and other bivariant plots indicate that the sediments are derived mostly from acidic to intermediate igneous rock. Majority of the sediments have geochemical similarity with the arkose and litharenite sandstones. The chemical index of alteration (CIA) values of the MRB sediments varies between 52 and 69 with most of the samples having CIA < 60 suggesting the lower degree of weathering which is further supported by the mineralogy. The eroded sediments have compositional maturity comparable to sediments deposited under semi‐arid climatic conditions. Sediments show both positive and negative Eu anomalies based on the source rock. Based on the commonly used discrimination diagrams, it is concluded that the MRB has a tectonic setting similar to the passive continental margin. [ABSTRACT FROM AUTHOR]

The Mohe Basin, to the south of Mongol–Okhotsk suture belt (MOSB) closely, is a good window into investigations of the evolution of the Mongol–Okhotsk Ocean during the Late Mesozoic. Sandstone samples of the Upper Jurassic Series in the Mohe Basin, Mohe, and Kaikukang formations are studied in detail in terms of petrography, geochronology, and geochemistry. All samples have low compositional and textural maturity, which are located in the areas of dissected arc and basement uplift in Dickinson's discrimination diagrams. LA‐ICP‐MS U–Pb zircon dating yields the youngest concordant ages of 173 ± 4 Ma and 157 ± 3 Ma for the Mohe and Kaikukang formations, respectively, which constrain the maximum sedimentary periods of them. The peak ages of all concordant ages correspond identically to the regional magmatic activities on both the Siberian Craton and Erguna Block. All samples demonstrate geochemical characteristics not so different from the upper continental crust, whose provenance is felsic in lithology and is situated in active continental margins. Thus, a Mohe foreland basin and its binary provenance are strongly suggested, with the Erguna Block – a southern source and the Siberian Craton – a northern one. Based on all the evidence above, a simple tectonic model of the evolution of the Mongol–Okhotsk Ocean is raised, that is, from the Triassic to the Middle Jurassic; the Mongol–Okhotsk oceanic plate continued to subduct under the Siberian Craton and the Erguna Block, triggering intense magmatism in these areas. In the Late Jurassic, the rapid closure of the Mongol–Okhotsk Ocean caused the basement uplift and intense denudation which provided abundant sources of dissected arc and basement materials for the Mohe Basin. [ABSTRACT FROM AUTHOR]

This work aims to unveil the origin, geodynamic significance, and diagenetic history of pyroclastites and associated chert documented within the Upper Anisian volcano‐sedimentary succession of the Ivanščica Mt. in Central Europe. An abundance of pyroclastic material points to polyphase volcanic activity and deep‐water sedimentation along the rim of an oceanic realm. Radiolarian‐based dating revealed Illyrian age of chert intercalated with pyroclastites. The latter are largely vitro‐crystalloclastic and were emplaced as airborne tuff. The crystalloclasts of sanidine, plagioclase, altered pyroxene, and amphibole are principal tuff constituents merged in the altered glassy matrix consisted of palagonite, clay minerals, and calcite. Variations in alteration assemblages reflect an extensive in situ eogenesis in an open hydrologic system that gradually evolved toward a restricted fluid percolation environment. Mineralogy, chemistry, and occurrence of andesitic tuff clearly denote an explosive volcanic activity formed at the top of suprasubduction zone. Such scenario presumes a complex genesis outlined in following steps: (a) partial melting and dehydration of down‐going Palaeotethyan slab which gave rise to the subduction‐related magmatism {LILE, Th, and LREE [(La/Lu)cn = 6.51−9.42] enrichment; negative anomalies of Nb‐Ta, P, and Ti [e.g., (Nb/La)n = 0.31−0.44]}; (b) magma contamination via interaction with continental crust during magma uplift along tectonically weakened zones of upper crust [positive Pb spikes, negative εNd (−4.18 to −4.44), and 147Sm/144Nd ≤ 0.113175]. This is in favour of geodynamic evolution that hypothesizes the existence of an active, ensialic, and mature volcanic arc developed along the southern active continental margins of Euramerica (Laurussia) during Late Anisian subduction of Palaeotethyan lithosphere. [ABSTRACT FROM AUTHOR]

Bhowmik suggested two stages of orogenesis at the southern margin of the Central Indian Tectonic Zone (CITZ): (a) an accretionary orogenesis type at ca. 1.6–1.5 Ga that formed a proto‐Greater Indian Landmass (GIL) through the assembly of arc, back‐arc and continental margins, (b) a Himalayan‐style continental collision event between 1.06 and 0.93 Ga that finally stitched the North and South India blocks to produce the final configuration of the GIL and (c) an intervening phase of extension between 1.5 and 1.06 Ga that led to the opening up of the Sausar Basin and deposition of the Sausar Group of rocks. [ABSTRACT FROM AUTHOR]

Significant sedimentary and tectonic information is preserved in the geochemical characteristics of the Middle Triassic Zhifang Formation in the southern Ordos Basin, North China. In this paper, elemental geochemical analysis is performed for 12 mudstone and siltstone samples from the Zhifang Formation of the Liangzhai River–Liulinchuan section of Tongchuan City, Shaanxi Province, with a major element analysis performed via X‐ray fluorescence spectrometry, trace element and rare earth element (REE) analyses performed via inductively coupled plasma mass spectrometry (ICP‐MS). The palaeoenvironment and tectonic backgrounds of the study section are also studied by analyzing the elements and elemental ratios sensitive to palaeoenvironmental conditions. The geochemical proxies, including the concentrations of U, and ratios of Fe2O3/FeO, U/Th, V/(V + Ni), V/Cr, and Ni/Co indicate that the depositional environment of the Zhifang Formation was likely an oxic–dysoxic condition without strong lake‐water stratification. The oxic–dysoxic condition is interpreted as one of the key controlling factors for the poor development of source rocks in the Zhifang Formation, although this formation is dominated by black fine‐grained sediments. Because of the Qinling orogenic belt, the geochemical characteristics reflect a tectonic background of the provenance area that was an active continental margin related to the continental island arc. [ABSTRACT FROM AUTHOR]

The deep‐water Niger Delta continental slope is a prolific petroleum province. A key challenge in unlocking the potential of such petroleum provinces is in understanding the internal architecture and associated controlling factors of deep‐water depositional systems. Here, we used high‐resolution 3D seismic data to analyse the development of a submarine system on the midslope of the Niger continental margin: the Bakama Submarine Depositional System (BSDS). Over 18 km down dip, the BSDS evolves from lobes through straight channels to lobes again. The fills of intraslope Minibasin I comprised three overlapping lobe complexes varying in size from 1,200 to 4,000 m in width, 15 to 30 m in thickness, and 8 to 11 km in length. During the development of these three lobe complexes, Minibasin I and adjacent growth faults interacted with a variety of deep‐water depositional process, which directly influenced the sediment distribution on this slope and the evolution of whole BSDS. Downstream of Minibasin I, ten straight, sub‐parallel adjacent channels occurred on a significantly increased slope (from <2° to >3°). They deeply incise the underlying strata and are small in scale, 150 to 200 m in width, 30 to 45 m in depth with aspect ratios of 4 to 5. On a more gentle slope section (<2°) within the linked downslope intraslope basin (Minibasin II), these adjacent channels are replaced by two attached lobe complexes that are some 2,100 to 3,100 m in length, 600 to 1,700 m in width, and 10 to 30 m in thickness. Therefore, it could be concluded that localized slope gradients play an important role in the development of straight channels and their attached lobes. [ABSTRACT FROM AUTHOR]

The major, trace, and rare earth element (REE) compositions of sediments from the Meghna River in Bangladesh have been examined to infer their sediment type, compositional maturity, chemical weathering intensity, provenance, and tectonic setting. Geochemically, the sediments are classified as litharenites, shale, and wacke. The ICV (Index of Compositional Variability) values (0.92 to 1.10) indicate that the sediments have low compositional and mineralogical maturity. Major and trace element abundances display marked depletion of Na2O, CaO, MgO, K2O, Fe2O3T, Sr, and Ba relative to UCC (upper continental crust), suggesting loss of feldspars during chemical weathering in the source. Zirconium, Th, Ce, and Y are enriched relative to UCC, indicating that these elements are primarily controlled by resistant heavy minerals. The CIA (Chemical Index of Alteration), PIA (Plagioclase Index of Alteration), and Rb/Sr and K2O/Rb ratios of the river sediments suggest low to moderate intensity of chemical weathering in the source area. Chondrite‐normalized REE patterns show that high LREE enrichment, nearly flat HREE fractionation (LaN/YbN = 7.62 to 8.73) and marked negative Eu anomalies (Eu/Eu* = 0.49 to 0.69) suggesting a felsic source provenance. Several discriminant function diagrams and immobile trace element ratios (Th/Sc, Zr/Sc, Ce/Sc, and Ti/Zr) and REEs (∑LREE/HREE, Eu/Eu*, and GdN/YbN) parameters indicate that the river sediments were primarily derived from a common felsic source rock, with composition close to the average rhyolite, granodiorite, granite, and UCC. Tectonic setting signatures of the Meghna River sediments are both active continental margin and passive margin environments. [ABSTRACT FROM AUTHOR]

Middle Jurassic mudstones from the Yangye Formation are widely exposed in the Kashi Sag and regarded as significant potential source rocks. Geochemical characteristics of mudstones in the Keziletao Depression have been analysed to decipher their source‐area weathering, provenance, tectonic setting, and depositional environment that have received significantly little attention. Mudstones are characterized by high Ca, U, Th, and REE contents when compared to those of PAAS. Their total REE abundances range from 155.2 to 234.2 ppm, with the enrichment of LREEs and distinct negative Eu anomalies, implying a principal felsic provenance. Various indicators (e.g., CIA, Th/Sc, ICV, and Rb/Sr) and A‐CN‐K ternary diagram suggest parental rocks experienced a moderate to intense chemical weathering degree and simple recycling and sorting. Furthermore, paleoenvironmental indexes (e.g., B, "S," Sr/Ba, "C," Sr/Cu, and V/(V + Ni)) indicate that they were likely deposited in a suboxic to anoxic freshwater setting, with semi‐arid to semi‐humid paleoclimatic conditions during the deposition of Yangye Formation. The geochemical data also demonstrate that the provenances were derived predominantly from the unroofing of felsic rocks with a minor intermediate supply. These parental rocks were commonly formed in the continental island arc, active continental margin, and/or collision tectonic settings. The results of this study, combined with published data, suggest the West Kunlun Orogen and thrusting zone to the west and south‐west of the basin were probably arrested to provide substantial detritus for sediments, stimulating a better understanding for the formation mechanism of the Yangye Formation sediments (especially for potential source rocks) in the Kashi Sag. [ABSTRACT FROM AUTHOR]

Rocks in extensional settings are generally sensitive to destruction and erosion, resulting in poor preservation potential and accumulation of their eroded components. The South China margin was dominated by a prolonged extensional setting from Late Mesozoic to Early Cenozoic, and this geological history is exactly archived in sediments within and surrounding the present South China Sea. However, the sedimentary evolution of the region, especially prior to the continental breakup and oceanic spreading, remains an issue of uncertainty and controversy, mostly due to limited borehole penetration and poor seismic reflection data for deeply buried sequences, as well as the lack of reliable regional stratigraphic framework. Here, we illustrate the Cretaceous–Palaeogene sedimentary evolution of the South China Sea region by synthesizing relevant data from previous literature and our own observations and displaying the evolution of lithofacies in sequential palinspastic reconstructions. The preferred palaeogeographic scenarios incorporate the latest interpretations of the conjugate relationship between continental margins as well as the birth and demise of the hypothetical Proto‐South China Sea. The patterns of lithofacies and depositional environments at regional scales, along with available provenance data, clearly reveal sedimentary responses to the significant Mesozoic–Cenozoic transition of plate geodynamics and magmatism along the Asian margin and provide implications for the potential mechanism of Cenozoic extension represented by distinct yet continuous processes of continental rifting and oceanic spreading. [ABSTRACT FROM AUTHOR]

This study reports new LA‐ICP‐MS U–Pb zircon ages from the Xinghuadukou Complex from the Erguna Block, NE China. A suite of the Palaeoproterozoic orthogneiss and a suite of the Vendian to Cambrian paragneiss are recognized with the co‐magmatic age of 2,464 ± 26 Ma and the maximum depositional age of 561 ± 10 Ma for their igneous and sedimentary protolith, respectively. The trace element geochemical analysis suggests a strong arc affinity for our orthogneiss, characterized by the enriched LREE and LILE, the elevated incompatible and fluid‐mobile elements and the depleted yet negligible fractionated HREE and HFSE. By comparing our samples with a suite of Cenozoic mantle‐derived granitoids from Hokkaido and a suite of Mesozoic active continental margin volcanics from NE China, it is suggested that the igneous protolith of our near Archaean orthogneiss formed in an arc environment and probably derived from the prior arc crust. The trace element features of the paragneiss highly resemble that of the orthogneiss, showing arc affinity, which suggests an arc basin environment for the sedimentary protolith of our Vendian to Cambrian paragneiss. Based on the synthesized evidence from the Xinghuadukou Complex, a new tectonic scenario is proposed that the basement of the Erguna Block might be forged by the accretion and collision of multi‐episodic igneous arcs and their correlated arc basins, which was probably lasting through the Proterozoic and followed by the Pan‐African period high‐grade metamorphism. The consolidated Erguna Block was later involved into the CAOB tectonic domain, modified and disrupted with the assembly of NE China. [ABSTRACT FROM AUTHOR]

The Central Tianshan microcontinent (CTM) in the southern Central Asian Orogenic Belt is characterized by Precambrian crustal basements and widespread Palaeozoic granitic rocks. However, the Palaeozoic tectonic process and associated crustal evolution of the CTM have not been well constrained. In this paper, we report whole‐rock geochemistry, zircon U–Pb ages, Hf isotopes, and trace elements for the Late Carboniferous granodiorite and monzogranite from the Hongliujingbei area of the eastern CTM. These data were further integrated with previously published whole‐rock geochemistry and zircon Hf isotopic data of the intensive Late Carboniferous (327–300 Ma) magmatic rocks in the CTM in order to gain more insights into the crustal and tectonic evolution of the CTM during the Late Carboniferous. LA‐ICP‐MS zircon U–Pb dating results indicate that the granodiorite and monzogranite from the Hongliujingbei area were emplaced at ~320 Ma. Their highly variable zircon εHf(t) values (−0.1 to +12.9) suggest that the magmas of these rocks were formed by the mixing of mantle‐ and crustal‐derived magmas. The Late Carboniferous magmatic rocks from the CTM, as a whole, show a wide range of zircon εHf(t) values (−3.7 to +13.4) and geochemical characteristics typical for magma evolution in an active continental margin setting. Therefore, we suggest that the Late Carboniferous magmatic rocks in the CTM were probably generated in a continental arc formed by the southward subduction of the North Tianshan Ocean Plate beneath the CTM, and their mostly depleted zircon Hf isotopic compositions indicate that juvenile crustal growth was a dominant process in the CTM during the Late Carboniferous. [ABSTRACT FROM AUTHOR]

The position of structures of Mongolia during Rodinia break‐up and Paleo‐Asian Ocean opening is debatable, and reconstructions between them are poorly known. In this paper, we apply an integrated approach to the not widely known yet distinctive structure (ribbon‐like) of the Lake and Mongolian Altay zones in western Mongolia, relating these with the surrounding Tuva–Mongolian and central Mongolian microcontinents (CMMs) development within the Central Asian Orogenic Belt (CAOB) and Paleo‐Asian Ocean evolution. We present a summary of the Neoproterozoic–early Palaeozoic tectonic development of western Mongolia and the CAOB and suggest a new comprehensive model for its evolution. The Lake zone of Mongolia is a major zone of ophiolite and arc complexes within the CAOB. The main sections of ophiolites are located along the west margin, bordering with Precambrian crystalline basement of the CMM. The ophiolites are distributed from north to south and have been dated to have similar ages. A classic oceanic plate stratigraphy section is preserved in the Lake zone. Serpentinite mélange and other volcanogenic‐terrigenous assemblages from the Lake zone are characterized by a system of nappe sheets thrust over the Dzavkhan block of the CMM. The ribbon‐like structure that the southern part of the Altay–Lake zone preserves at present provides an explanation for the development between the Gondwana‐derived microcontinent and Paleo‐Asian Ocean. During the pre‐Neoproterozoic, convergence accretion between Siberia and the CMM formed the Tuva–Mongolian belt, which later converted to the Altay–Lake collision zone associated with the thrusting of its eastern margin. All well‐known ophiolites of western Mongolia (Agardag, Khantayshir, and Dariv) as well as ophiolites of the Erdene Uul area mostly correspond to an "open‐ocean" phase with drifting microcontinents between 655 and 540 Ma or Neoproterozoic. In the early Neoproterozoic, the Altay peninsula‐like ribbon microcontinent after rifting of East Gondwana gradually drifted to Siberia. In this time, the east margin of the Paleo‐Asian Ocean was developed as a passive margin with the Dzavkhan Block. The Paleo‐Asian ocean plate simultaneously drifted to the CMM, whereas the Altay microcontinent moved into Siberia‐CMM. In middle‐upper Neoproterozoic times, the eastern part of the Paleo‐Asian ocean plate was thrusted over the CMM, obducting ophiolites (e.g., Tas Khairkhan), in the early Cambrian time, an oceanic spreading centre (?) of the Paleo‐Asian Ocean reached the CMM and stopped obduction. In the Neoproterozoic, the west margin of the Paleo‐Asian Ocean was developed as an active continental margin, with subduction under the Gondwana‐derived microcontinent. In the early Cambrian, there was significant subduction rollback and accretion of seamounts (Turgen). Later, in middle Cambrian–early Ordovician times, a large turbidite sequence was deposited in Altay. During the Devonian to Carboniferous, the Paleo‐Asian Ocean was preserved as a remnant ocean or big sea (Lake zone), accumulating marine deposits after collision of Siberia and the Altay microcontinent by late Cambrian. [ABSTRACT FROM AUTHOR]