The tectonic affinity of the quartzite unit is essential for reconstructing the Cenozoic evolution of the Eastern Himalaya Syntaxis. We presented new petrographic and zircon U-Pb geochronological data from the quartzite unit collected from the western boundary of the Namche Barwa syntaxis. The maximum depositional ages indicated multiple depositional stages at >1800, 1122-1136, 885, 451-493 and 54 Ma. Detrital zircon ages spanned from 50 to 3269 Ma with dominant populations at 500-900, 950-1400, 1550-1700 and 1750-2000 Ma. These age distributions suggested that the detritus were derived mainly from the Central Indian Tectonic Zone, Shillong Plateau and the Eastern Ghats Orogeny of the northeastern Indian subcontinent, and Western Australia. This provenance signature was distinct from the typical sequences of the Lesser Himalayan Sequence, Greater Himalayan Sequence and Tethyan Himalayan Sequence in the central-western Himalayas. Integrating our results with existing data from the Nyingchi Complex in the southern Lhasa terrane and Lesser Himalayan Sequence in the Eastern Himalayan Syntaxis, we proposed that the Namche Barwa syntaxis, Nyingchi Complex and Lesser Himalayan Sequence shared common source regions. Long-lived fluvial systems likely transported detrital material from northwestern Australia and the northeastern Indian subcontinent to these tectonic units.

As the world's highest and largest plateau, the uplift of the Tibetan Plateau profoundly reconfigured Asian physiography, reorganized atmospheric circulation, and drove long-term changes in surface environments and biodiversity, serving as a unique natural laboratory for investigating coupled geological-climatic-ecological processes. Integrated Earth-system research on the Tibetan Plateau therefore provides robust scientific foundations for addressing global challenges such as climate-change adaptation and mitigation, ecosystem conservation, and sustainable resource management. The Tibetan Plateau exhibits pronounced geological heterogeneity, comprising an assemblage of amalgamated terranes that have progressively amalgamated over the past similar to 300 Myr through successive subduction of intervening oceanic basins along suture zones. These multiple subduction and collision events resulted in the formation of heterogeneous lithosphere and variable histories of crustal deformation and surface elevation change across the Tibetan Plateau. Quantitative paleoaltimetry has become the most robust approach for reconstructing the timing, magnitude, and spatial pattern of plateau growth. Mostly applied quantitative paleoaltimetries include hydrogen and oxygen isotope paleoaltimetry, clumped-isotope thermometry, nearest living relative techniques and coexistence approach based on plant and animal fossils and palynology, moist enthalpy and biomolecular proxies. Over the past three decades, extensive paleoaltimetric reconstructions of the Tibetan Plateau have been carried out by integrating diverse proxies with paleoclimate simulations, targeting major orogenic belts (e.g., Himalaya, Gangdese, Central Watershed, Kunlun) and intermontane basins (e.g., Central Tibetan Valley, Yarlung Tsangpo Valley, Hoh Xil Basin, Qaidam Basin). With that, the scientific consensus regarding the uplift of the plateau has evolved from an early paradigm of uniform (monolithic) uplift to a more refined framework emphasizing differential and spatiotemporally variable uplift processes. Present research supports an uplift scenario in which initially discrete orogenic belts progressively coalesced into a uniform high plateau. Following Neo-Tethys subduction and the onset of India-Asia collision at similar to 65 Ma, the Gangdese and Central Watershed Mountain attained elevations above similar to 4,500 m prior to similar to 50 Ma, while the intermontane Central Tibetan Valley between them remained at a relatively low elevation of similar to 1,700 m, producing a "two mountain ranges sandwiching a low elevation basin" topography. Between similar to 45 and 25 Ma, progressive lithospheric removal and isostatic readjustment drove uplift of eastern Tibetan Plateau and the Central Tibetan Valley to elevations exceeding similar to 3,000 m, producing the earliest high-altitude plateau topography. A Mediterranean-like climate emerged in eastern Tibetan Plateau-characterized by warm and dry summer and cool and wet spring-autumn-and promoted the development of biodiversity hotspots in the Hengduan Mountains represented by the Relu and Markam Basins. By the Miocene, rapid uplift of the Himalaya and northern Tibetan Plateau brought those regions to near-modern elevations and completed the formation of the present-day plateau. During this period, the South and East Asian monsoon systems stabilized into near-modern regimes, promoting the emergence of montane monsoon forests akin to contemporary ecosystems. As a result, intensified precipitation and headwater formation rendered the plateau the source region for Asia's major rivers and contributed to the development of fertile ecosystems in downstream basins, especially in modern South China. Despite these advances, ongoing research on the uplift of the Tibetan Plateau and its interactions among multiple Earth-system spheres remains limited by sparse paleoaltimetric data and mismatches between proxy reconstructions and model simulations. Future priorities include developing high-resolution regional Earth-system models, integrating proxies with simulations for systematic cross-validation, and advancing next-generation paleoaltimetric techniques to clarify the mechanistic linkages between tectonic evolution and climate change. These efforts constitute critical steps for understanding the Tibetan Plateau's Earth system and its implications for regional resources and environments.

In this study, the factors that drive the Yigong earthquake swarm in the southeastern part of the Tibetan Plateau are investigated. By analyzing the temporal and spatial characteristics of the earthquake swarm, the Xixingla fault is identified as the primary agent in driving the genesis of the earthquake swarm and the seasonal variations in seismic activity. As a significant branch of the southeastern Jiali fault, the Xixingla fault is subjected to high stress stemming from the northward compressive forces of the eastern Himalayan syntaxis. Additionally, climate variations amplify freeze-thaw cycles in glaciers and increase riverine erosion, leading to increased topographical steepness and greater fracturing of rock masses. During the monsoon season, elevated temperatures and heavy precipitation result in substantial glacial melt, causing rapid accumulation of meltwater and rainfall in Yigong Lake. This phenomenon increases the surface load acting on the fault zone, whereas infiltrating water increases pore pressure along rock fractures and faults. The stress accumulated along the fault ultimately triggers rupture, resulting in the formation of an earthquake swarm. Furthermore, the increased stress on the fault due to the 2017 Milin earthquake contributed to a higher frequency of seismic events in the Yigong region. Understanding the hydrogeological and tectonic conditions in Yigong and its vicinity is essential for predicting future seismic activity and developing effective disaster prevention strategies.

On December 18, 2023, an Ms. 6.2 earthquake occurred in Jishishan County, Gansu Province, China, causing significant casualties and triggering a major mudflow disaster in Zhongchuan township, Minhe County, Qinghai Province. This event was the largest instrumentally recorded earthquake in the Lajishan fault zone at the northeastern margin of the Tibetan Plateau. The integration of multiple datasets (interferometric synthetic aperture radar (InSAR) data, precise aftershock relocations, field investigations, and geophysical inversions) revealed the causative fault as a northeast-dipping thrust fault in the Lajishan fault zone, which exhibits a primarily thrust focal mechanism with a dextral strike-slip component and a peak slip of 0.96 m. Triggered by the Jishishan earthquake, the Zhongchuan mudflow represents an earthquake-loess liquefaction-mudflow disaster chain. Notably, the formation of this mudflow was governed by seismic ground motion amplification effects, saturated loess liquefaction, and a high groundwater table. Although analogous to the prehistoric disaster that destroyed the Lajia Ruins, distinct differences exist in terms of sediment sources and landform configurations. Furthermore, Coulomb stress change analysis revealed significant loading along the eastern Jishishan, western Jishishan, and central-southern Daotanghe-Linxia faults, suggesting that these faults warrant focused attention with respect to their future seismic hazard potential. This study provides new evidence for the destruction of the Lajia Ruins and elucidates the mechanisms underlying seismically triggered cascading hazards along the northeastern margin of the Tibetan Plateau.

Asia’s exceptional biodiversity is reflected in the Hengduan Mountains fossil record in eastern Tibet, yet the timing and drivers of mammalian diversification remain enigmatic. Here we combine U–Pb dating of mammalian bone-cavity calcite and palaeosol nodules from the Relu Basin with stable-isotope palaeoaltimetry of fossil tooth enamel. We show that the Relu mammal assemblage was buried at 39.2–38.1 Ma, making it the oldest directly dated Cenozoic mammal fauna reported from the Tibetan Plateau, and that herbivores inhabited near-modern habitat elevations of 3463 m (+819/−869). This directly dated Eocene mammalian assemblage coincided with diversification of high-elevation forests, implying that a montane biodiversity hotspot had emerged by ~39 Ma. Mediterranean-type false-ring signals in 41.5-Ma fossil wood and climate-model simulations are consistent with Eocene surface uplift contributing to a strongly seasonal, bimodal-rainfall regime that predated the modern Asian monsoon and provided environmental conditions favourable for early high-elevation biotic diversification. These results refine Tibetan mammalian chronology and provide a benchmark linking mountain-building, rainfall seasonality and biodiversity. Eocene herbivorous mammals on the Tibetan Plateau inhabited elevations of 3463 m by ~39 Ma under a bimodal-rainfall regime predating the modern Asian monsoon, coinciding with the diversification of high-elevation forests, according to direct dating and palaeoaltimetry from bone-cavity calcite, palaeosols and fossil tooth enamel, together with fossil tree-ring evidence.

Black shales play a significant role in the global carbon cycle, serving as sites for organic carbon burial and facilitating matter and energy exchanges between the Earth's spheres. However, the mechanisms driving these processes remain controversial, particularly regarding the onset of the extensive Middle-Late Triassic organic carbon burial in the North China Craton (NCC). In this study, we summarize 5009 detrital zircon UPb ages along with five new samples integrated with seismic reflection profiles, boreholes, field outcrop and sandstone petrographic analyses. Our findings reveal a significant provenance shift in the southern NCC, transitioning from distal to proximal recycling during the deposition of the late Middle Triassic black shale. This shift was driven by coeval tectonic uplift and volcanism in the Qinling Orogenic Belt. Paleogeographic reconstructions indicate that by the Ladinian stage, the western NCC had transformed into an endorheic, underfilled lacustrine basin with potential for intermittent marine transgression. Combining our findings with previous paleoclimate and tectonic studies, we propose that intense regional tectono-thermal activity, triggered by the subduction and closure of the eastern Paleo-Tethys Ocean, rather than global climatic forcing alone, was the driver of the extensive Middle-Late Triassic organic carbon burial in the NCC. This study provides the tectonic insights into the sedimentary processes of black shales and their implications for terrestrial organic carbon burial during the Middle-Late Triassic period.

Mesozoic exotic tectonic fragments in the Yarlung Zangbo suture zone (YZSZ) preserve key records for reconstructing Neo-Tethyan evolution. This study investigates basalts and limestones from the Buma area in the central segment through petrology, calcite U-Pb geochronology, and whole-rock geochemistry. Calcite U-Pb dating of two recrystallized limestone samples yields ages of ca. 244 Ma and ca. 246 Ma. The Buma basalts are subalkaline, with SiO2 contents of 37.95-53.61 wt.% and high TiO2 (1.63-3.43 wt.%). Their rare earth elements (REEs) and trace element patterns resemble Hawaiian ocean island basalts (OIBs), and they exhibit moderately depleted Nd isotopic compositions (epsilon Nd(t) = +4.20 to +4.93). The pronounced negative Ce anomalies in limestones and the absence of terrigenous clastic components in collapse conglomerates indicate deposition in an open-ocean setting. Integrated evidence indicates that the basalt-limestone association in the Buma area represents a Neo-Tethyan ocean island-seamount system. Combined with the 253 Ma continental rift basalts from the Zhongba area, this result suggests that the opening of the Neo-Tethys Ocean in the central segment of the YZSZ occurred no later than the Early Triassic, providing key empirical evidence for the spatiotemporal framework of the early evolution of the Neo-Tethys Ocean.

Abstract The East Kunlun Orogen (EKO) on the northern margin of the Tibetan Plateau experienced complex Late Paleozoic–Early Mesozoic tectono‐magmatic activities associated with the subduction and closure of the Paleo‐Tethys Ocean. Controversies remain regarding the timing and processes of the transition from subduction to collision and post‐collision, as well as the mechanisms of continental crustal growth. This study presents zircon U–Pb ages (257–202 Ma), whole‐rock geochemical data and Sr–Nd–Hf isotopic compositions for granitoids from the Nanshankou and Yeniugou areas in the EKO. The 257–246 Ma granitoids have variable Mg# values (34.9–49.7) and εHf(t) values (−4.9 to +1.1), and contain mafic enclaves, suggesting derivation from crust‐mantle magma mixing. The ∼235 Ma granitoids have low Mg# values (30.7–32.7), and enriched Nd–Hf isotopic compositions, indicative of partial melting of mafic lower crust. The 203–202 Ma adakitic granitoids show positive εHf(t) values (0.0 to +4.7) and relatively high Mg# values (45.3–48.7), pointing to partial melting of delaminated mafic lower crust with involvement of mantle‐derived magma. Integrating our results with regional geological data, we propose that the Paleo‐Tethys Ocean in the EKO experienced long‐term subduction during 278–240 Ma, accompanied by continental arc crustal growth. Following ocean closure at ∼240 Ma, the region entered a syn‐collisional stage (240–220 Ma) dominated by crustal remelting. The EKO then evolved into the post‐collisional stage at ∼220–200 Ma, with lithospheric delamination triggering vertical crustal accretion. This study constrains the subduction, collision, and post‐collision evolution and crustal growth of the EKO from Middle Permian to Triassic.

The closure of the Paleotethyan Ocean in the northern Tibetan Plateau formed a world-class rare-metal (Li, Be, Rb, Nb, and Ta) pegmatite metallogenic belt within the Dahongliutan-Hohxil-Songpan-Ganzi terrane of western China. Spodumene-rich pegmatites are hosted in the folded Triassic turbidites and often associated with Late Triassic−earliest Jurassic I-type and S-type granites. However, the parental affinity of these spodumene-rich pegmatites—whether from I-type or S-type granites—remains debated. To resolve this, we conducted geochronological and geochemical analyses of diorites, granodiorites, leucogranites, spodumene-free pegmatites, and spodumene-rich pegmatites from the Bailongshan ore field. Zircon U-Pb dating results show that the diorites intruded at 217.5−210.1 Ma, granodiorites at 212.3−205.0 Ma, and leucogranites at 215.1−196.2 Ma. Columbite U-Pb ages indicate emplacement of spodumene-free pegmatites at 220.9−196.2 Ma and spodumene-rich pegmatites at 213.9−194.7 Ma, suggesting synchronous magmatism during the Late Triassic−earliest Jurassic. Geochemically, hornblende-rich diorites and hornblende-bearing granodiorites show low SiO2, high MgO, metaluminous to weakly peraluminous signatures (Alumina Saturation Index [A/CNK] = 0.59−1.13), and calc-alkaline characteristics, and are typically I-type granites. Leucogranites containing muscovite, garnet, and tourmaline exhibit high SiO2, low MgO, strongly peraluminous signatures (A/CNK = 1.16−1.34), and high-K, calc-alkaline affinities. They are typically S-type granites, which show higher Rb/Sr and Rb/Ba ratios, indicating sedimentary rocks as their protoliths. Isotopically, S-type granites [87Sr/86Sri = 0.7111−0.7149; εNd(t) = −11.0 to −10.3; εHf(t) = −8.4 to −2.7] and pegmatites [87Sr/86Sri = 0.7182−0.7189; εNd(t) = −11.7 to −10.7; εHf(t) = −9.2 to −0.9] exhibit more enriched isotope compositions, similar to those of the wall-rock turbidites [87Sr/86Sri = 0.70803−0.7173; εNd(t) = −13.1 to −3.2], and are distinctly different from I-type granites [87Sr/86Sri = 0.7084−0.7098; εNd(t) = −6.8 to −6.3; εHf(t) = −6.2 to +0.9]. This implies that the pegmatites are derived from the S-type granites, not the I-type granites. The low temperatures (<750 °C) estimated by the Ti-in-zircon thermometer for both I- and S-type granites suggest that S-type granites were likely derived from fluid-fluxed melting of the Triassic turbidites, favoring extraction of rare metals from staurolite, biotite, and muscovite in metaturbidites during anatexis. The coeval I-type granites provided the external heat and exotic volatiles, promoting staurolite and mica breakdown in the metaturbidites and thus facilitating the release of rare metals into the S-type leucogranitic melts. This suggests that although rare-metal pegmatite mineralization in Bailongshan is primarily related to S-type granites, I-type granites also played a contributing role. The formation of the coeval Late Triassic−earliest Jurassic barren I-type and fertile S-type granites in Bailongshan is attributed to final bidirectional subduction, slab rollback, and delamination of the Paleotethyan oceanic slab.

The Tibetan and Iranian plateaus are the two most prominent orogenic plateaus on the present Earth built by continental collision. However, the timings of initial collision and suturing in the Himalaya and Zagros remain debated. In this Review, we summarize the timings, similarities and differences between the India–Eurasia collision and the Arabia–Eurasia collision, by comparing their sedimentary, magmatic, metamorphic, structural and palaeomagnetic records. The India–Eurasia collision is tightly constrained to have initiated in the central Himalaya at 65–59 Ma, possibly progressing towards the western and eastern Himalayas by 55–50 Ma. By contrast, the initial collision in the Zagros is loosely constrained to ~34 Ma, with a possibility of diachronous collision, younging to the southeast. Similarities between the two collisions include pre-collisional accretionary tectonism and magmatism, syn-collisional deformation and sedimentation, and crustal thickening. Apparent differences in lithospheric dynamics, deformation styles and metamorphism are attributed to variations in convergence rates, durations and magnitudes. Future research should focus on data-driven modelling and geophysical imaging beneath the Tibetan and Iranian plateaus to further quantify the geodynamic processes and driving forces contributing to continuous plate convergence, plateau formation and their surface impacts. The collision of the Indian, Arabian and Eurasian plates formed the Tibetan and Iranian plateaus, but its timing and processes remain debated. This Review explores the evidence behind initial collision estimates and discusses the tectonic and geodynamic implications.

The Sanchakou, Keteli, and Tielemu skarn tungsten (W) deposits have recently been discovered in the East Kunlun Orogenic Belt, northwestern China. However, the formation ages and petrogenesis of the W-fertile intermediate-felsic intrusions remain poorly constrained. In this study, zircon UPb dating results show that the intrusions formed in two epochs, Middle Triassic (similar to 250-238 Ma) and Late Triassic (similar to 230 Ma). The first epoch of intermediate-felsic intrusions (the similar to 242 Ma Sanchakou and Tielemu monzogranites and the similar to 238 Ma Keteli granodiorite) is closely associated with skarn W mineralization, except for the slightly older (similar to 247 Ma) and barren garnet-bearing monzogranite at Keteli. The similar to 250-238 Ma intrusions are mainly metaluminous and belong to the calc-alkaline to high-K calc-alkaline series. They show LREE-rich patterns with weak negative to positive Eu anomalies (La-N/Yb-N = 3.66-41.9 and Eu/Eu* = 0.52-1.10), enrichments in LILEs (e.g., Rb, K, Th, and U), and depletions in HFSEs (e.g., Nb, Ta, Ti, and P). In comparison, the similar to 230 Ma syenogranite exhibits similar geochemical characteristics, except for more pronounced negative Eu anomalies (Eu/Eu* = 0.20-0.28). All studied intrusions reveal a negative correlation between SiO2 and P2O5, indicating an evolutionary trend of I-type granitic melts. The two epochs of intrusions have relatively consistent zircon Hf isotopic compositions (epsilon(Hf)(t) = -7.7 to 3.2 and - 4.5 to -0.8, respectively), suggesting that they may have been derived from the partial melting of Meso-Proterozoic basement rocks with a minor addition of mantle-derived material. Moreover, the W-fertile intrusions show hydrous and weakly oxidized features, evidenced by relatively low zircon saturation temperatures (738-789 degrees C), Zr/Sr (0.11-0.70), and fO(2) values (triangle FMQ = 0.07-0.55). Based on new geochemical data and regional geological investigations, we propose that the Middle Triassic intrusions (similar to 250-238 Ma) formed during the late-stage of northward subduction of the Paleo-Tethys oceanic plate. In contrast, the Late Triassic (similar to 230 Ma) syenogranite was generated in a local extensional setting related to oceanic slab rollback following the collision between the East Kunlun and the Hoh-Xil-Songpan-Ganzi terranes.

The Qaidam Basin, the largest intermountain basin in Northern Tibet, has recently gained attention for a newly proposed depositional age, specifically for the Lulehe Formation (Fm). Two contrasting models currently exist: the traditional interpretation places its deposition during the Paleocene or Eocene, while more recent age models suggest deposition during the Oligocene. This significant conflict hampers understanding of the timing of activity of the surrounding fault systems, and the uplift and growth mechanism of the northern Tibet. In this study, we sampled tubular carbonate veins and abundant paleosol calcareous nodules from the Lulehe Fm. Using calcite UPb dating and clumped isotopes, we obtained an average age of 50.8 f 2.8 Ma and formational temperatures of the nodules ranging from 39.6 f 2.3 degrees C to 43.2 f 3.4 degrees C in the Honggou section, and 28.2 f 0.7 degrees C to 34.3 f 4.2 degrees C in the Hongshan West section. Furthermore, by applying elevation-dependent isotopic and clumped temperature lapse rates, we reconstructed the paleoelevation of the Qaidam Basin during the early Eocene to be 1.6 f 0.98 km. Our findings align more closely with the traditional stratigraphic framework of the Lulehe Fm, indicating that initial sedimentation in the Qaidam Basin occurred during the early Eocene. Moreover, we provide a quantitative estimate of the basin's paleoelevation during its early stage. While our data may suggest the possibility of southward growth in northern Tibet, alternative interpretations cannot be ruled out, and further research is required to better constrain the uplift patterns.

Understanding the Cenozoic growth history of the Himalaya-Tibetan Plateau (HTP) is essential for elucidating the underlying geodynamic mechanism and interactions among topography, biosphere and atmosphere. However, the spatial-temporal evolution of the HTP, especially that of the Paleogene Central Tibetan Valley (CTV), remains hotly debated. In this study, through radiometric geochronology, plant assemblages, oxygen and clumped isotope paleoaltimetries, we reconstruct the uplift history of the east-west-oriented Luolong Basin in eastern Tibet. Results show that the Luolong Basin was at 0.6 (+0.2/-0.4) km at ca. 54-46 Ma, then rose to 2.9 ± 0.9 km at ca. 44 Ma. The newly discovered Luolong Flora indicates the Eocene CTV extending into eastern Tibet, and that the valley was higher in the east, sloping to the west, inferring a westward progressive rise of the valley floor. Integrated evidence from paleomagnetism, magmatism and seismic tomography suggests that the birth of the near modern plateau is attributed to the stepwise delamination (drip) of the subducted Lhasa lithosphere from east to west.

The Nagaland Ophiolite Complex (NOC) is exposed at the eastern margin of the Indo-Burma Range, which represents the suture zone between the Indian and Burmese Plates. The NOC that contains a complete mantle and crustal lithological assemblage can provide important information regarding the tectonic evolution of the NeoTethys Ocean. The studied basaltic rocks from the NOC can be classified into two groups according to their geochemical results. The Group I rocks are geochemically comparable with the E-MORB, which have slight LREE enrichment ((La/Yb)N = 1.45-1.96). The Group II rocks share geochemical characteristics with typical N-MORB and exhibit LREE depletion, with (La/Yb)N of 0.47-0.69. All samples showed slightly positive or insignificant anomalies in high-field-strength elements. The Group I and Group II rocks were derived from the partial melting of spinel-facies mantle peridotite, and the degrees of partial melting of the former (approximately 5 %) are lower than those of the latter (approximately 10 %). Both groups of basaltic rocks are characterized by high positive epsilon Nd(t) values (+7.0 - +7.6 and + 5.4 - +8.3, respectively). Our study revealed that the Group I rocks were predominantly derived from a MORB-like asthenospheric source that was variably enriched by OIB-type components, whereas the Group II rocks were derived from a depleted asthenospheric mantle source without the contribution of OIB-type components. The heterogeneous asthenospheric mantle sources contributed to the geochemical complexities of the basalts from the NOC. These results, combined with regional geological records, suggest that the basalts from the NOC were mainly generated in a mid-ocean ridge setting during the evolution of the Neo-Tethys Ocean.

Global ice losses will likely continue with ongoing climate warming, culminating in an almost ice-free planet analogous to that which persisted throughout much of the Cretaceous. Despite extensive research, Early Cretaceous cryosphere responses to temperature and atmospheric P CO 2 fluctuations over short, human, timescales remain uncertain. Here, we show rapid late Valanginian (~133 million years ago) seasonal fluctuations in sea surface temperature (SST) and δ 18 O mainly driven by atmospheric P CO 2 . Two distinctive features emerge: large seasonal variability of up to 15.9° ± 4.9°C in Southern Hemisphere mid-latitudes, comparable to that found today, a positive sea surface δ 18 O value related to evaporation (expressed as salinity increases), and the existence of polar ice. Model-predicted patterns of SST change match with high statistical confidence those derived from clumped isotopes in well-preserved oyster fossils from Madagascar and display consistent warm/cold seasonality. Given its relative coolness in a Cretaceous context, the late Valanginian is a valuable analog for Earth’s future climate.

Seafloor topography is highly important in marine science as a crucial physical background field. Seafloor topography inversion mainly relies on marine gravity data to supplement missing bathymetry data in areas lacking ship measurements. However, existing inversion algorithms often overlook the geophysical properties and spatial differences of seafloor topography. As an improvement, we develop a new seafloor topography inversion algorithm based on topographic heterogeneity partitioning where different parts having different densities. It consists of three steps: First, by quantifying the slope of observed vertical gravity (VG), a 94% change rate as the threshold for partitioning topographic heterogeneity, and a quadtree spatial indexing algorithm is used to segment the observed sea area into sub-regions. Secondly, the constrained ship soundings data and the optimal reference density contrast for each subregion, derived by minimizing the misfit between observed and calculated ship soundings data, are used as inputs for the VG inversion. Finally, a geographically weighted linear equation system is derived from the observed gravity data, and the least squares method is employed to solve for the inversion of seafloor topography. A case study in the western Pacific Ocean shows that the RMSE between the inversion results and the bathymetry data is 83.6 m, representing an 11.5% reduction compared to the traditional GGM that does not consider topographic segmentation. Compared to the GEBCO_2024 model, this algorithm reduces the overall RMSE by 38%.

Widely distributed Oligocene-Miocene ultrapotassic volcanic rocks in the Lhasa terrane of southern Tibet have been associated with the melting of the lithospheric mantle, plateau uplift, and porphyry Cu-Au mineralization. This study presents the mineral chemistry of olivine and clinopyroxene phenocrysts, whole-rock major and trace element data, and zircon U-Pb geochronological and Hf isotopic data for the Sailipu primitive ultrapotassic volcanic rocks. The Sailipu volcanic rocks exhibit high MgO (5.6-11.4 wt%), Cr (386-981 ppm), Co (22-43 ppm), and Ni (95-423 ppm) concentrations and have highly fractionated rare earth elements [REEs; (La/Yb)N = 23-73] and high-Fo (89.1-90.8) olivine phenocrysts containing elevated NiO (up to 0.59 wt%), which suggests a pyroxenitic mantle source that partially melted in the garnet stability field. Their high K2O contents (4.8-8.0 wt%) and global subduction sediment-like trace element patterns suggest that the metasomatic agents, which reacted with mantle peridotites to form phlogopite-bearing pyroxenites, were dominantly derived from the melting of subducted continental sediments. Their high whole-rock Ba/La and Th/Nd ratios are consistent with this hypothesis. The Sailipu ultrapotassic volcanic rocks also exhibit low initial 176Hf/177Hf ratios that resemble those of Himalayan leucogranites, and high Ca contents in olivine phenocrysts, which is consistent with contributions from the sub- ducted carbonate-rich sedimentary strata on top of the thinned Greater Indian continental crust. The zircon U-Pb chronological data yielded concordant ages of 24.33 +/- 0.19 Ma, 21.20 +/- 0.62 Ma, and 17.05 +/- 0.31 Ma for different exposures of the Sailipu volcanic rocks, which establishes a maximum age of ca. 24 Ma for these rocks. The northwest-southeast spatial distribution and the southeastward decrease in age (80 degrees E-90 degrees E) suggest west-to-east tearing of the thinned Greater Indian slab, which caused asthenospheric upwelling and melting of the Tibetan lithospheric mantle. Geothermometric calculations show relatively high primary magma temperatures (similar to 1250 degrees C) that are consistent with asthenospheric upwelling. We propose a mechanism that could genetically link the coeval Cu-Au ore-forming granitoids with the ultrapotassic magmatism of the Gangdese belt. The ultrapotassic rocks supply a large-volume of external magmatic volatiles, particularly H2O, which could trigger melting of the Tibetan lower crust and lead to the generation of the ore-forming granitoids and the establishment of oxidizing conditions for porphyry deposits. The oxygen fugacity (log & fnof;O2 values of OFMQ) of the primitive Sailipu ultrapotassic volcanic rocks (OFMQ = 0.48 +/- 0.51 based on the Dol/melt V oxybarometer and OFMQ = 0.33 +/- 1.19 according to the magmatic zircon U-Ce-Ti oxybarometer) is slightly lower than that of porphyry Cu-Au ore-forming granitoids in the eastern Gangdese (OFMQ = +0.8 to +2.9), which suggests that the direct injection of ultrapotassic melts into ore-forming granitoids played a limited role in changing oxygen fugacity, but more oxidized fluids/ volatiles exsolved from these ultrapotassic melts may have facilitated the remelting of sulfide-bearing lower crust and/or directly scavenged sulfides from the mush-state reservoirs of the ore-forming granitoids in the middle-upper crust.

The Bangong-Nujiang Ocean played an important role in the formation of the Tibetan Plateau prior to the Cenozoic India-Eurasia collision. However, there are still uncertainties about the subduction polarity and timing of the Lhasa-Qiangtang collision. We conducted sandstone petrologic and detrital zircon U-Pb-Hf isotopic analyses on the Cretaceous Wada melange, trench-fill strata and Duoni Formation in the Basu area in the eastern Bangong-Nujiang Suture Zone. The Wada melange (-114 Ma) exhibits block-within-matrix features and a detrital zircon U-Pb age spectrum characterized by multiple peaks at 114-180 Ma, 200-300 Ma, and 1800-2000 Ma. The trench-fill strata consist of coherent chert, sandstone, and mudstone, with a detrital zircon age spectrum dominated by a single peak at -120 Ma. The epsilon Hf(t) values of the 110-300 Ma detrital zircon grains in the Wada melange and trench-fill strata range from -20 to +10 and are consistent with those of the South Qiangtang Terrane. The epsilon Hf(t) values of the -120 Ma detrital zircons are all negative, and these grains were likely derived from a remnant Cretaceous arc in the South Qiangtang Terrane to the north. These data suggest that the accretionary wedge was derived from the South Qiangtang Terrane during the northward subduction of the Bangong-Nujiang Ocean. The Duoni Formation (-113 Ma) represents peripheral foreland basin deposits with the Lhasa Terrane as the basement. Provenance analysis indicates that these deposits received clastic material mainly from the South Qiangtang Terrane and to a lesser degree from the North Lhasa Terrane. Our results suggest that the Lhasa-Qiangtang collision occurred in the Early Cretaceous (-113 Ma) in the eastern segment of the Bangong-Nujiang Suture Zone.

Understanding the evolution of continental crust is crucial for comprehending the Earth's structure and exploring the development of plate tectonics and orogenic belts.In convergent plate margins,large-scale igneous rocks are generated,and their geochemical features are closely related to their formation depth.Consequently,these rocks are widely used in reconstructing crustal thickness and interpreting paleoaltitudes in orogenic belts.In this paper it reviews the establishment and development of methods that utilize geochemical information to investigate crustal thickness.It evaluates the advantages,disadvantages,and applications of various methods,and summarizes their use in different orogenic belts and their role in paleoaltitude reconstruction.As a complement to quantitative paleoaltimetric techniques,the geochemical approach provides more continuous reflections of crustal thickness over time.Combined with rapidly accumulating geochemical databases,this method can offer deeper insights into paleoaltitude estimates,and the tectonic evolution of orogenic belts,and effectively promote the development of Earth system science.

The East Kunlun-Qaidam Block, situated in the northeastern margin of the Qinghai-Tibet Plateau, preserves numerous geological records associated with the evolution of the Rodinia supercontinent. However, the Precambrian tectonic evolutionary history and continental affinity of the East Kunlun-Qaidam Block have long been controversial. In the present study, the results of zircon U-Pb dating reveal that the precursor rocks of the granitic gneisses from the East Kunlun-Qaidam Block were formed between 935 and 928 Ma. The geochemical and Nd-Hf isotope data of these granitic gneisses, coupled with the fact that they contain Paleo-Mesoproterozoic inherited zircons and Al-rich minerals, reveal that their protoliths are S-type granites formed through the partial melting of the Paleo-Mesoproterozoic sedimentary rocks. Combined with available regional geological data, we suggest that the protoliths of the studied granitic gneisses most likely formed in syn-collisional settings during the amalgamation of Rodinia. The 1.0-0.9 Ga granitic magmatism in the East Kunlun-Qaidam and Qilian areas recorded tectonic conversion from oceanic subduction, continental collision, and post-collision. The detrital zircon ages of the studied Mesoproterozoic metasedimentary rocks in the North Qaidam ultrahigh-pressure metamorphic belt show a major age population at 1.97-1.72 Ga, and the Yangtze Block might be the dominant sedimentary provenance, contributing a large volume of the exotic detritus. The Mesoproterozoic metasedimentary rocks from the Shaliuhe Group might have been deposited in a passive continental margin environment during the late Mesoproterozoic. The youngest detrital zircon ages (713-618 Ma) from the Neoproterozoic metasedimentary rocks in the East Kunlun-Qaidam Block suggest that they were most probably formed in the middle-late Neoproterozoic era. Zircons from the Neoproterozoic strata both have a major age cluster of 1.0-0.9 Ga, which were mainly derived from the East Kunlun-Qaidam Block. The Neoproterozoic strata were deposited in a continental rift setting during the breakup of Rodinia. Our study further supports that the East Kunlun-Qaidam Block has a tectonic affinity with the western Yangtze Block from late Mesoproterozoic to Neoproterozoic.