The interaction between mantle plumes and the lithospheric mantle is critical for understanding the genesis of flood basalts. The Emeishan Large Igneous Province (ELIP), composed predominantly of basalts with minor picritic rocks and radiating mafic dyke swarms, offers an exceptional natural laboratory for studying this process. In this contribution, we present geochemical and Sr-Nd-Hf-Pb isotopic data for high-Ti basalts from Weng’an, at the easternmost margin of the ELIP. These basalts (TiO2 > 2.8 wt.%, Ti/Y > 500) are enriched in large ion lithophile elements (LILEs: Ba, Th, U) and slightly depleted in high field strength elements (HFSEs: Nb, Ta, Zr, Hf, Y). They exhibit initial (87Sr/86Sr)t ratios of 0.70594–0.70697, εNd(t) of +1.2 to +1.8, εHf(t) of +1.1 to +1.9, and (206Pb/204Pb)t of 18.11–18.51. Their geochemical signatures resemble those of other high-Ti ELIP basalts and ocean island basalts (OIB) but are distinct from those of depleted mantle sources. Trace element patterns and Pb–Pb isotope systematics indicate derivation from a garnet + spinel lherzolite source linked to the Emeishan mantle plume, with ~8–10% input from sub-continental lithospheric mantle (SCLM) metasomatized by slab-derived fluids during ascent. These results provide direct evidence for heterogeneous SCLM contributions to plume-derived magmas and highlight the role of lithospheric heterogeneity in shaping the composition of LIP magmatism.

The southern Central Asian Orogenic Belt (CAOB) underwent a major Early Paleozoic tectonic transition, yet its timing and mechanisms remain unclear. We present zircon U-Pb-Hf, whole-rock geochemical, and Sr-Nd isotopic data for newly identified Early Silurian (ca. 439-431 Ma) granitoids from the Liuyuan area of the southern Beishan Orogenic Belt. These high-silica, high-K calc-alkaline intrusions not only show arc-like trace-element patterns but also display elevated Ga/Al ratios and enriched Sr-Nd isotopic compositions ((Sr-87/Sr-86)(i) = 0.7158-0.7189; epsilon(Nd)(t) = -4.6 to -3.9), consistent with aluminous A(2)-type granites derived mainly from ancient crust. Their heterogeneous zircon epsilon(Hf)(t) values (-6.3 to +3.7) suggest a minor, localized input from mantle-derived mafic magmas superimposed on the dominant crustal signature. Integrating regional metamorphic constraints, we interpret this magmatism to have formed during the transition from oceanic subduction to incipient collision/continent involvement and subsequent post-subduction extension, plausibly triggered by slab break-off at the slab root (ocean-continent transition). Slab-window-related asthenospheric inflow and localized thermal perturbation could have promoted high-temperature crustal melting and facilitated Early Silurian crustal reworking in the southern CAOB.

The recycling of carbonates between the Earth's surface and its interior plays a critical role in global carbon cycling and atmospheric CO2 variations. This study investigates the fate of subducted carbonates from the NeoTethyan Ocean and their contribution to Cenozoic atmospheric CO2 through the analysis of Cenozoic alkaline basalts from the Tianshan basalt province in western China. Combining Mg-Ca-Sr-Nd-Pb isotopes, major and trace element geochemistry, numerical modeling, and through systematic evaluation of potential influences from both source lithology and magmatic processes, we demonstrate that the distinctive low delta 26Mg (-0.50 to -0.37 %o) and delta 44/40Ca (0.48 to 0.86 %o) values indicate a mantle source metasomatized by recycled marine carbonates, dominated by dolomite and magnesite. These carbonates were transported into the mantle transition zone (MTZ) via the subduction of the Neo-Tethyan oceanic slab, which stagnated and later contributed to mantle melting and magmatic CO2 degassing during the Eocene. Our calculations reveal high magmatic CO2 degassing fluxes (-0.3 - 0.5 Pg/a) from the Tianshan basalt province, comparable to those of the India-Asia collision-related magmatism. The temporal correlation between these fluxes and Cenozoic atmospheric CO2 variations suggests that the Tianshan basalt province and similar intraplate volcanic systems substantially contributed to Cenozoic atmospheric CO2 changes and paleoclimatic shifts. This study provides direct evidence for deep carbon recycling from subducted oceanic carbonates to mantle sources and highlights the importance of intraplate magmatism in regulating Earth's carbon cycle and climate.

The ophiolite assemblages of the Yarlung-Zangbo Suture Zone (YZSZ) in southern Tibet represent fragments of the Neo-Tethyan lithosphere that once separated the Indian and Asian continents and are unique among global ophiolites in their characteristic thick-mantle and thin-crust architecture. However, the petrogenetic and tectonic processes responsible for this distinctive feature remain elusive. Here, we investigate the Xiugugabu ophiolite in the western YZSZ using integrated field observations, zircon U-Pb geochronology, bulk-rock geochemistry, and zircon Hf isotopes. Mafic rocks from the Xiugugabu ophiolite yield Early Cretaceous formation ages of ca. 124-120 Ma and define two coeval but geographically and geochemically distinct groups. Group A rocks were derived from a typical N-MORB-like depleted mantle, whereas Group B rocks record contributions from an ultradepleted mantle that experienced ancient melt extraction followed by subsequent melt refertilization, as indicated by their negative Zr-Hf anomalies, sub-MORB Zr/Hf and Nb/Ta ratios, and highly radiogenic zircon epsilon Hf(t) values (up to +21.1). Immobile trace-element discriminants (e.g., Th/Yb-Nb/Yb and Ti-V systematics) indicate that the Xiugugabu mafic rocks formed in a subduction-unrelated environment, most consistent with a slowspreading mid-ocean ridge, which can account for the thick-mantle and thin-crust ophiolite pseudostratigraphy. In contrast, coeval mafic rocks from the Xigaze ophiolite in central YZSZ display subduction-related signatures and have distinct paleomagnetic positions and sedimentary covers. Taken together, these observations indicate that the YZSZ ophiolites represent a tectonic collage assembled from compositionally and spatially distinct fragments of the Neo-Tethyan oceanic lithosphere.

The Lau Basin, a rapidly opening back-arc basin in the southwest Pacific, is a critical region for investigating the the extent of the Indian-type mantle domain and its geodynamic evolution relative to the Pacific domain. To determine the nature of the upper mantle source feeding this basin, we present comprehensive major-trace element compositions and in situ Pb isotopic ratios for 27 volcanic glass samples from the Central Lau Bsa. The samples are subalkaline tholeiites exhibiting N-MORB-like trace element patterns, indicative of a predominant depleted mantle source modified by minor fractional crystallization. Critically, the Pb isotopic compositions (208Pb/204Pb = 37.8-44.3; 207Pb/204Pb = 15.53-17.25) are distinctly higher than those of Pacific MORB and plot unequivocally within the Indian Ocean MORB field, revealing a clear Dupal anomaly. This definitive Pb isotopic signature, consistent with existing regional Sr-Nd data, identifies the ambient mantle beneath the central Lau Basin as belonging to the Indian-type (Dupal) geochemical domain, not the Pacific type. Our results confirm that large-scale, southward mantle flow driven by Tonga slab rollback, has supplied Indian-type mantle to the basin, displacing prior Pacific mantle. This study provides crucial constraints on the local distribution of Indiantype mantle and highlights the dynamic interplay between deep mantle reservoirs and shallow tectonic processes in back-arc settings.

The Liuyuan ophiolitic melange in the Beishan orogenic belt in Gansu Province, China, preserves key remnants of Paleozoic oceanic lithosphere that provide insights into the geodynamic evolution of the Paleo-Asian Ocean. We investigated clinopyroxene-rich mantle pyroxenites (wehrlite to olivine clinopyroxenite/pyroxenite) using petrographic, zircon U-Pb geochronological and Lu-Hf isotopic, whole-rock and in situ mineral geochemical, whole-rock Sr-Nd-Pb isotopic, and in situ clinopyroxene Pb isotopic methods. Zircon U-Pb ages of 430-421 Ma date a Silurian melt infiltration/pyroxenitization event during oceanic basin development. Zircon has epsilon Hf(t) = -4.65 to +8.47, indicating a variable isotopically depleted to mildly enriched metasomatized mantle source. The pyroxenites have low contents of trace elements (Sigma REE = 98.57-156.05 ppm), slight enrichment in light rare earth elements ([La/Yb]N = 1.82-5.54), positive Eu anomalies (Eu/Eu* = 0.97-2.67), and depleted high field strength elements (e.g., negative Nb anomalies). Melts in equilibrium with clinopyroxene, reconstructed using partition coefficients, plot in the oceanic basalt field but are generally closer to mid-ocean ridge basalt-like compositions and have supra-subduction zone-like depletions in high field strength elements. Whole-rock epsilon Nd(t) values of -1.6 to -1.3 and Pb isotopic data indicate these rocks have a subduction-modified mantle source with an Indian-type isotopic signature. Clinopyroxene thermobarometry indicates multi-stage equilibration from deep high-pressure-temperature conditions (augite) to shallower levels (diopside), consistent with melt focusing during lithospheric extension. We infer that the Liuyuan pyroxenites formed by open-system melt-rock interactions in an extensional supra-subduction zone/inter-arc basin that developed above northward-subducting oceanic lithosphere, prior to the final Late Triassic closure of the Liuyuan Ocean.

Low-delta O-18 magmas (delta O-18 < +5.5 parts per thousand) record the assimilation of rocks that underwent high-temperature hydrothermal alteration. This study presents an integrated analysis of oxygen isotopes and major elements of olivines, along with whole-rock geochemistry and Sr-Nd-Hf isotopes for basaltic andesites and andesites from the Quaternary Agung and Batur volcanoes in Bali, Indonesia. Agung and Batur lavas exhibit similar trace element and Sr-Nd-Hf isotopic signatures but differ in their olivine oxygen isotopic compositions. Olivine phenocrysts from Agung lavas show delta O-18 values ranging from +4.65 parts per thousand to +5.38 parts per thousand, with an average of +5.08 +/- 0.21 parts per thousand (2SD, n = 20). Olivines from Batur lavas exhibit lower delta O-18 values (+3.70 parts per thousand to +5.15 parts per thousand), with an average of +4.50 +/- 0.14 parts per thousand (2SD, n = 120), and most are distinctly below the mantle olivine values. The low delta O-18 values observed in both Agung and Batur olivines are unlikely to result from assimilation of pre-existing hydrothermally altered crustal or syn-magmatic rocks. Instead, they provide evidence for the assimilation of recycled altered oceanic crustal materials. We propose that these assimilated oceanic crustal materials could have been derived from the partial melting of low-delta O-18 lower oceanic crust, possibly induced by hot asthenospheric flow through a slab window. This study highlights that slab windows may facilitate not only the formation of rear-arc ultrapotassic lavas but also significantly influence magmatism at the volcanic front.

The Nanling region in South China contains widespread granites of variable ages. Large-scale W and Sn mineralization were closely associated with Yanshan granites, but the mineralization related to granites of other ages has been little studied. Understanding the metallogenic significance of Indosinian granites is crucial for refining exploration models, as recent discoveries suggest they may have played a greater role than previously recognized. The weighted mean zircon U-Pb age of the biotite granite from the eastern part of the Dupangling pluton is 224.7 f 4.8 Ma, while the cassiterite U-Pb age from the Babanqiao Sn-polymetallic deposit is 223.6 f 4.0 Ma. These results indicate that the Babanqiao deposit formed contemporaneously with late Indosinian granitic magmatism, suggesting that the deposit was likely associated with granitic activity during the late Indosinian period. Fluid inclusion data reveal the initial ore-forming fluids were part of a NaCl-H2O system with high to moderate temperatures and salinities, which contained CH4 f N2. Homogenization temperatures ranged from 182.1 degrees C to 381.5 degrees C in the early mineralization stage and decreased to 145.4 degrees C to 279.8 degrees C in the main mineralization stage, with corresponding salinities of 13.62-25.15 wt% NaCl equiv. and 7.45-19.76 wt% NaCl equiv., respectively. These values indicate that ore deposition occurred under reducing conditions, with a progressive decrease in temperature and salinity as meteoric water mixed with the magmatic fluids. delta 18O and delta D values show that the ore-forming fluids were magmatic waters that gradually transitioned to meteoric waters. This progressive dilution likely influenced metal transport. Integrated analysis indicates that during the Indosinian period, Sn-bearing magmatic-hydrothermal fluids migrated into closely spaced microfractures and joints, where localized boiling may have occurred, producing limited precipitation. The fluids then ascended along these structures and mixed with infiltrating meteoric water, destabilizing Sn-Cl complexes and precipitating Sn in fault zones to form quartz-vein-type Sn ore. Thus, fluid mixing was the primary mineralization mechanism at Babanqiao. These findings also highlight the exploration potential of Indosinian granites in South China as hosts of previously unrecognized W-Sn systems.

The interplay between mantle plume-derived seamounts and subduction zones plays a pivotal role in shaping orogenic evolution, yet its long-term geological fingerprints remain understudied in ancient orogens. Here, we investigate the Mayile ophiolitic m & eacute;lange in West Junggar (Altaids) to unravel the lifecycle of a plume-modified oceanic plate and its interaction with subduction processes. Our integrated petrological, geochemical, and isotopic analyses reveal three distinct phases of magmatism tied to mantle plume and seamount subduction. The 490 Ma Type 1 assemblages (OIB-type hornblende gabbro, carbonatized basalt and basalt) exhibit NbTa enrichment (Nb/Nb* >1), transitional Pacific-to-Indian MORB Pb isotopes, and positive epsilon(Nd)(t) values (6.08-7.55), suggesting that they were derived from a mantle plume source beneath the Junggar Ocean. Hornblende thermobarometry reveals shallow melting (37-280 MPa) under anomalously high temperatures (886-938 degrees C), akin to modern plume-affected oceanic plateaus (e.g., Galapagos). These features record Late Cambrian seamount magmatism atop thinning lithosphere, analogous to Pacific intraplate volcanism. Types 2 assemblages (arc-type diabase, hornblende gabbro, carbonatized basalt and basalts) and granites mark the transition to subduction-dominated processes. Depleted Nb and Ta signatures coupled with Indian-MORB type Pb isotopes and sediment-derived PbNd isotopic components (1-2% input) reflect forearc accretion of plume-modified crust during Late Cambrian-Ordovician subduction. This geochemical shift mirrors global examples of seamount subduction (e.g., Mariana), where plume-derived components become entrained in forearc systems. This study establishes an Early Paleozoic analogue for the complete lifecycle of a plume-influenced oceanic plate: 1) Late Cambrian seamount generation atop a thinning lithosphere, 2) Ordovician southward subduction accretion of plume-modified crust, and 3) progressive mantle source contamination through sediment recycling. These findings advance our understanding of how seamount subduction processes shaped the architectural complexity of ancient oceanic terranes in the Altaids and similar accretionary orogens worldwide.

Over 90% of global heavy rare earth elements (HREEs) reserves are found in the Nanling region of China in weathering crust deposits derived from granites, a deposit type unique in the world. However, the Nanling region is heavily vegetated, where dense plant cover acts as a natural barrier, posing significant challenges to traditional mineral exploration. We applied and validated a phytogeochemical remote sensing method using the indicator plant Dicranopteris dichotoma. Through controlled pot experiments under varying rare earth element (REE) stress, we discovered that specific spectral transformations and feature parameters could reveal significant correlations between leaf reflectance and soil REE contents (Ce, Gd, Y). Our analysis identified optimal, element-specific spectral indicators, with their Pearson correlation coefficients (r) relative to soil REE contents as follows: the absorption width at 570-720 nm for Ce (r = 0.75), and the first-derivative at 603 nm for Gd (r = 0.53). Notably, the first-derivative at 1856 nm and the absorption width in the 1300-1670 nm band were both identified as optimal indicators for Y, each achieving the highest correlation (r = 0.82). We further established that support vector regression (SVR) models significantly outperformed conventional methods, yielding an average increase of 0.05 in the coefficient of determination (R2) against stepwise multiple linear regression (SMLR) and a substantial increase of 0.21 against polynomial fitting, confirming superior accuracy and robustness. Our findings validate that plant spectra can function as a reliable bio-indicator for subsurface REE enrichment. This work proposes a novel approach for REE exploration in vegetated regions, representing a critical advancement towards sustainable and efficient resource discovery.

Abstract Geophysical observations reveal a low velocity layer atop the slab in the circum‐Pacific subduction zones at a depth of 100–250 km, whose origin is not well constrained. The presence of blueschist may potentially cause the low velocity layer. To test this hypothesis, we measured sound velocities in glaucophane‐the dominant mineral in blueschist‐using the ultrasonic interference method at pressures up to 9.9 GPa and temperatures up to 673 K. High‐temperature finite strain fitting of the data yielded the following elastic properties: . These results show that the elastic properties of glaucophane (e.g., its relatively low bulk‐to‐shear modulus ratio) differ significantly from those of most other minerals in subducting slabs. Combining the elastic properties of the subducting slab with our experimental data, we calculated the velocities of several blueschist mineral assemblages consisting of glaucophane and lawsonite. Our estimates indicate that an assemblage of 63.9% glaucophane and 36.1% lawsonite closely matches the seismic observations of the low‐velocity layer.

The Nanling metallogenic belt in South China is a world-class W-Sn province characterized by polyphase mineralization during the Caledonian, Indosinian and Yanshanian orogenies. However, compared to the extensively studied Yanshanian events, the Late Triassic mineralization remains relatively poorly constrained. The Dawan Sn-polymetallic deposit, located in the northeastern Dupangling composite batholith, hosts orebodies in the exocontact zone of a highly fractionated biotite monzogranite. Based on the regional geological context, the Dawan deposit was selected to investigate its potential genetic link to Late Triassic mineralization. This study employs cassiterite U-Pb dating, trace element analysis, fluid inclusion microthermometry, laser Raman spectroscopy and H-O-S isotopic analysis to elucidate its ore-forming processes. We obtained a cassiterite U-Pb age of 214.7 +/- 3.2 Ma, confirming that the mineralization occurred during the Late Triassic. This timing is coeval with regional post-collisional lithospheric extension and the emplacement of A-type granites in the western Nanling Range. Fluid inclusion data reveal an initial medium-high temperature, moderate-salinity H2O-NaCl-CO2 +/- CH4 system. Hydrogen and oxygen isotopes (delta D = -81.9 parts per thousand to -75.3 parts per thousand; delta 18OH2O = 3.7 parts per thousand-5.1 parts per thousand) indicate that the ore-forming fluids were predominantly magmatic in origin and gradually mixed with limited amounts of meteoric water. Notably, Sulphur isotopic compositions and cassiterite trace element chemistry collectively indicate that the ore-forming materials were derived from Indosinian highly fractionated granitic magmatic-hydrothermal fluids. We propose that fluid boiling initiated early cassiterite precipitation, while the continuous cooling and limited influx of meteoric water during the main stage triggered the oxidation of Sn2+-Sn4+, leading to large-scale mineralization. The Dawan deposit represents a critical component of the Indosinian Sn system in the western Nanling Range, associated with A-type granite emplacement during the tectonic transition from compression to lithospheric extension. These findings provide essential evidence for the 'West-strong and East-weak' extensional model and support the regional 'West Sn-East W' metallogenic zonation across the Nanling Range.

The melting behavior of a mixture of altered oceanic crust (AOC) and antigorite is experimentally investigated at 3 GPa and 680-1180 degrees C, aiming to simulate the melting process of serpentinite-dominated melange. Our results indicate that the melting of AOC produces silica-rich melt with residues of clinopyroxene and garnet. In the experiments of MA20 (80 wt% AOC and 20 wt% antigorite), high-Mg# orthopyroxene forms as a result of silicarich melt consumption. In the experiments of MA50 (50 wt% AOC and 50 wt% antigorite), the proportion of melt is low, and the products are mainly garnet, clinopyroxene, and orthopyroxene. Except for alkali elements, the compositions of melt produced are analogous to those of arc magmas. The partial melting of melange that incorporates serpentinite, altered oceanic crust, and sediment produces melts matching the average composition of global arc magmas. Our results indicate that partial melting of serpentinite-dominated melange may serve as a mechanism for the accumulation of harzburgite in some mantle wedges.

High-Mg andesites (HMAs) typically originate in subduction-related tectonic settings, including active continental margins and island arcs, and studies of HMAs can constrain the tectonic evolution of the South China Block and Paleo-Tethyan Ocean. This paper presents new chronological and geochemical data for high-Mg gabbroic diorites in the Funing area, southern South China. The gabbroic diorites yield ages of 254-249 Ma, and have moderate SiO2 contents (51.3%-57.8%), high MgO contents (4.6%-10.2%) and Mg# values (52-75), enrichment in large-ion lithophile elements and light rare earth elements, and depletion in high-field-strength elements-collectively displaying geochemical signatures typical of sanukites. The gabbroic diorites have radiogenic initial Sr and Pb isotopic compositions, and negative epsilon Nd(t) and epsilon HF (t) values. These characteristics distinguish the Funing gabbroic diorites from subduction-related igneous rocks in the Paleo-Pacific tectonic domain. Instead, they are isotopically similar to HMAs and basalts along the Paleo-Tethys suture. We propose the high-Mg gabbroic diorites and basaltic andesites in Funing area share a common mantle source, linked to subduction and rollback of the Paleo-Tethyan plate beneath the South China Block, which triggered back-arc rifting and partial melting of the metasomatized lithospheric mantle during the Late Permian to Early Triassic.

As a common product of hydrothermal ore-forming activities,calcite not only contains abundant fluid inclusions but also accommodates various kinds of trace elements such as Fe,Sr,Mn,REEs,and U within its crystal lattice.Importantly,the elemental and isotopic compositions of the calcite and its fluid inclusions are highly sensitive to the hydrothermal process.Thus,calcite is a key mineral for studying the mineralization processes and genetic mechanisms of hydrothermal deposits.In recent years,with the rapid development of analytical techniques with high spatial resolution,calcite has been used to have played an increasingly important role in the metallogenetic studies of ore deposits,including the source and evolution of ore-forming fluids and ore-forming chronology,and in the mineral exploration practices.However,there is still a lack of systematic review on the indicative significance of calcites in hydrothermal deposits for understanding the metallogenesis of deposits and guiding exploration of mineral resources.Therefore,in this paper,based on the summary of common occurrence characteristics of calcites in hydrothermal deposits,we have analyzed their geological implications at first.Subsequently,by integrating elemental-isotopic and fluid inclusion characteristics of those calcites,we have emphatically elucidated the applications of calcites in fields for tracing the source of ore-forming fluids,reconstructing the ore-forming processes,revealing the mineralization mechanisms,and constraining the ore-forming ages.Then we have explored the indicative significances of elemental-isotopic compositions of calcites for delineating the mineralization zones and guiding the mineral exploration.The latest research findings show that calcite plays a pivotal role in metallogenetic studies and mineral exploration of hydrothermal deposits.Nonetheless,how to identify and distinguish different types(paragenesis/stages)of calcites,how to determine whether the elemental-isotopic compositions of calcites had been reset by late-stage geological processes,and how to improve the spatial resolution and analytical precision of instrumental techniques are the main challenges faced in the research of calcites.

The Maoming meteorite, which fell in Guangdong Province, China, on May 28, 2025, represents the second-largest witnessed meteorite recovery event in China since 1949, with a total recovered mass of 423 kg. This study presents an integrated analysis of its petrology, mineral chemistry, and aerodynamic behavior to reconstruct the complete atmospheric entry-to-impact sequence. Fresh samples were examined using optical microscopy, electron probe microanalysis, and density measurements, while the entry trajectory was simulated using a fourth-order Runge-Kutta model constrained by impact crater morphology and atmospheric data. Based on mineralogical homogeneity and shock-weathering features, Maoming is classified as an L5 ordinary chondrite (shock stage S3, weathering grade W1) with a double-layered fusion crust indicating peak temperatures of 1410 degrees C-1615 degrees C. Aerodynamic modeling, based on a constrained initial velocity of similar to 15 km/s, yields an entry angle of 13.9 degrees and a terminal impact velocity of 267.23 m/s at a trajectory angle of 65 degrees. The simulated penetration depth (2.98 m) closely matches field observations (similar to 3 m), validating the reconstructed dynamics. Despite its friable, fractured structure, the meteoroid survived atmospheric passage without catastrophic disruption, contrasting with typical fragmentation-dominated entries. This case provides critical empirical constraints on the survival of moderately strong, fractured ordinary chondrites under moderate entry conditions. The combined petrological and aerodynamic approach presented here provides a framework for rapid trajectory reconstruction and impact effect quantification. This framework also offers empirical constraints on the trajectory and cratering mechanics of meter-scale, moderately strong meteoroids.

Understanding subduction initiation and mantle plume dynamics is central to plate-tectonic evolution but remains poorly constrained in ancient orogens. The tectonic evolution of the North Tianshan paleo-ocean basin, a key segment of the Paleo-Asian Ocean of the Altaids, has long been debated owing to the scarcity of diagnostic ophiolitic records. Here we present a systematic study of the Bayingou ophiolite that identifies two temporally and genetically distinct magmatic suites: a forearc-type ophiolitic assemblage (cumulate gabbro, gabbro, and plagiogranite; Group 1) and plume-related seamount basalts (Group 2). Zircon U-Pb geochronology indicates that Group 1 cumulate gabbro crystallized in the middle Cambrian (ca. 505 Ma), whereas Group 1 gabbro and plagiogranite record Early Carboniferous magmatism (ca. 345−330 Ma), implying episodic forearc magmatic activity. Group 1 rocks display major and trace element patterns and depleted Sr-Nd-Hf isotopic compositions comparable to those of typical Izu−Bonin−Mariana forearc basalts, while their Pb isotopes overlap Pacific mid-oceanic-ridge basalt (MORB) and Paleo-Asian MORB-type ophiolites, indicating derivation from a Pacific-type low-Th/U depleted mantle. Thermobarometric modeling suggests shallow (<8 kbar) and high-temperature (∼1156 °C) decompression melting of upwelling asthenosphere, consistent with extension-induced asthenospheric ascent in forearc settings. In contrast, Group 2 basalts are enriched in Nb, Ta, Ti, and light rare earth elements [(La/Yb)N = 4.6−6.6] and exhibit a pronounced DUPAL anomaly (first documented by Dupré and Allègre, 1983), indicating an enriched, plume-related deep-mantle source analogous to global hotspots (e.g., Hawaii, USA, North Pacific Ocean, and St. Helena, South Atlantic Ocean). Integrating these results with regional geology, we infer early Cambrian forearc development linked to subduction initiation, followed by sustained intra-oceanic subduction beneath the Yili−Central Tianshan block from the Early Carboniferous (ca. 345−265 Ma), accompanied by supra-subduction zone−type ophiolite formation. Widespread plume-related seamount volcanism produced composite oceanic lithosphere that later accreted into the orogenic complex. This study provides crucial constraints on forearc magmatism and plume activity, serving as a vital analogue for tectonic evolution in ancient orogenic systems.

A diverse range of dikes in the western Lhasa-Qiangtang collision zone provides constraints on the evolution of post-collisional tectonomagmatic processes and the growth of the Tibetan Plateau. We report geochronological, geochemical, and Sr-Nd-Hf isotopic data for granitic dikes in the Rebang area of the Northern Lhasa Block, northern Tibet. Zircon U-Pb dating of the granitic dikes reveals abundant inherited zircons with ages ranging from 1869 to 98.8 Ma, and the youngest age groups (83.9-82.0 Ma) indicate that they formed during the Late Cretaceous. The granitic dikes are characterized by high Sr and low Y contents and high Sr/Y ratios, and they have adakitic geochemical affinities and variable zircon epsilon Hf(t) (-6.01 to +9.82) and whole-rock epsilon Nd(t) (-0.55 to +1.43) values. These features, together with the high Mg# values, suggest that the Rebang granitic dikes are derived by partial melting of thickened juvenile lower crust with variable degrees of contamination by mantle peridotite. The co-occurrence of widely distributed dikes and thick-bedded terrestrial molasses in the Late Cretaceous suggested that the central Tibet underwent post-collisional extensional collapse, which was triggered by lithospheric delamination. We favor that isostatic rebound in response to delamination induces rapid surface uplifting and gravitational collapse in the Lhasa-Qiangtang collision zone. Additionally, our research proposes that the post-collision extensional collapse in the Late Cretaceous plays an important role in the vertical growth of the Tibetan Plateau.

Crustal evolution and the genesis of gran ite are closely linked to anatexis in the lower or middle crust, followed by the ascent of gra nitic magmas to the upper crust. The Daqing shan complex in the North China Craton is characterized by the extensive development of Precambrian migmatites and granites re sulting from crustal anatexis. Understanding the controls on the geochemical diversity of these granitic magmas during their forma tion and extraction would enhance our un derstanding of crustal evolution from the late Neoarchean to early Proterozoic. In this study, we investigated the diverse types of migmatite and granitic rock related to par tial melting in the Daqingshan complex us ing systematic petrographic, wholerock geo chemical and Sr-Nd isotopic compositions, and zircon U-Pb-Hf isotope analyses. Our new results, combined with data from the lit erature, allow reconstruction of the complete process of magma formation, extraction, and evolution for migmatites in the study area. The following new insights are obtained. (1) The Daqingshan migmatites record two main periods of metamorphism (at ca. 2.45 Ga and ca. 2.37 Ga) and one period of anatexis (at ca. 2.37 Ga). (2) The migmatites originated from the Daqingshan supracrustal rocks via dehy dration melting of biotite. (3) During magma extraction, decomposition of the magma was controlled predominantly by the entrainment of residuum; incongruent melting of plagio clase and its earlystage crystallization and compaction led to the fractionation of pla gioclase and Kfeldspar within the in situ to semi in situ magmatic accumulation site. (4) Factors such as protolith composition, rock and mineral melting mechanisms, residuum entrainment, fractional crystallization, com paction, and the assimilation of surrounding rocks played crucial roles from initial melt ing to magmatic evolution and collectively contributed to the chemical diversity of mig matites and granitoids in the southwestern margin of the Daqingshan complex. (5) From the late Neoarchean to early Paleoprotero zoic, substantial fractionation of plagioclase and Kfeldspar during dehydration melting of metasedimentary rocks can resulted in the efficient migration of Krich melt from the anatectic source. This migration may have provided the source magma for Krich gran ite in the upper crust and contributed to the differentiation of continental crust from Pla gioclaserich to Kfeldsparrich components.

The North Qilian Orogen experienced a series of late Neoproterozoic to early Paleozoic tectonic events, including the opening and closure of the Proto-Tethyan Qilian Ocean, as well as post-subduction processes. This study investigated the Shandan adakites in the Longshoushan area of the North Qilian Orogen, focusing on zircon U–Pb geochronology, whole-rock geochemistry, and Sr–Nd–Hf–O isotopic compositions. The Shandan adakites yield ages of ca. 446–440 Ma, suggesting they crystallized during the collision between the Alxa and Qilian blocks following the closure of the Proto-Tethyan North Qilian Ocean. High Sr/Y (40.9–117) ratios and enrichments in light rare earth elements indicate that the Shandan adakites were formed by partial melting of thickened magnesian lower crust. They have relatively rich εNd (t) (−7.66 to −6.32), εHf(t) (3.30 to −12.4), and δ18O (5.34‰–7.52‰). Zircon Hf–O and whole-rock Sr–Nd isotopes confirm significant contributions from the ancient crust and mantle-derived melts, suggesting complex crust–mantle interactions in their magma sources. We propose that the Shandan adakites formed during the (early) post-collisional stage of orogenesis. Based on regional geological evidence and previous studies, we suggest the Alxa and Central Qilian blocks collided during ca. 446–440 Ma, leading to the thickening of the lower crust. After ca. 440 Ma, the tectonic setting of the Northern Qilian Orogen transitioned from a collisional to a post-collisional stage.