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Assessing fault activity in regions lacking Quaternary sedimentary constraints remains a global challenge. In this study, we used channel slope distribution to examine variations in rock uplift along faults. By comparing channel steepness with published low-temperature thermochronology and paleo-seismic data, we identified deformation changes both perpendicular to and along the Longmen Shan at various time scales. Our data revealed distinct fault segments displaying distinct thrust activities along the Longmen Shan's strike. In the southern segment, the Dachuan fault exhibited the highest activity, and its movement had persisted for millions of years. In the central segment, the Wenchuan fault was active during theearly Quaternary but has become dormant since the late Pleistocene. Within the past millions of years, the Yingxiu and Pengguan faults displayed significant vertical displacement. Fault activity in the northern Longmen Shan was relatively weak, with the Qingchuan fault transitioning from thrust movement during the Neogene to pure strike-slip activity since the Pleistocene. Overall, the Dachuan and Huya faults exhibited deformation patterns similar to the Yingxiu fault during the Quaternary. Similar to the Yingxiu fault, which triggered the Wenchuan earthquake, the Dachuan and Huya faults possess the capacity to produce significant earthquakes in the future. The variations in deformation perpendicular to and along the Longmen Shan fault system underscore the importance of upper crustal shortening in shaping the rock uplift patterns and topography of the eastern Tibetan Plateau margin. [ABSTRACT FROM AUTHOR]

Understanding the nature of parental melts for pyroxenite veins in supra‐subduction zone (SSZ) ophiolites provides vibrant constraints on melt infiltration processes operating in subduction zones. The Zedang ophiolitic massif in the eastern Yarlung–Zangbo suture zone in Tibet consists of mantle peridotites and a crustal section of gabbro, diabase, and basalt. Veins of two pyroxenite varieties cut the southern part of the Zedang massif. These pyroxenite rocks have different geochemical characteristics, where the first variety (type‐I) has relatively higher contents of SiO2 (51.82–53.08 wt%), MgO (20.08–23.23 wt%), and ΣPGE (3.42–13.97 ppb), and lower Al2O3 (1.59–2.28 wt%) and ΣREE (1.63–2.94 ppm). The second pyroxenite variety (type‐II) is characterized by SiO2 (45.44–49.61 wt%), MgO (16.68–19.78 wt%), Al2O3 (4.24–8.77 wt%), ΣPGE (14.46–322.06 ppb), and ΣREE (5.82–7.44 ppm). Pyroxenite type‐I shows N‐MORB‐like chondrite‐normalized REE patterns. Zircon U‐Pb ages of pyroxenite type‐I (194 ± 10 Ma), associated ophiolitic gabbro (135.3 ± 2.0 Ma), and plagiogranite (124.2 ± 2.3 Ma) evidently imply episodic evolution of the Zedang ophiolites. The mineralogical and geochemical characteristics of the investigated pyroxenites can be explained by subduction‐initiated hydrous melting of metasomatized sub‐arc mantle, later overprinted by sub‐slab mantle melting triggered by upwelling asthenosphere during the Jurassic–Early Cretaceous times. The geochemical variations in pyroxenite vein composition, coupled with age differences amongst the other ophiolite units, may correspond to intermittent emplacement of pyroxenite dikes and isotropic gabbroic intrusions where the geodynamic setting progressed from arc maturation and slab rollback to slab tearing and delamination. [ABSTRACT FROM AUTHOR]

The tectonic transition from oceanic subduction to continental collision is a fundamental process during orogenesis, yet the nature of such transition and associated deep geodynamic processes for the Tibetan Plateau are still controversial. The long‐lived magmatism of the Gangdese Belt of southern Tibet provides an excellent opportunity to study the tectonic transition from subduction of the Neo‐Tethys oceanic lithosphere to the continental collision between Indian and Asian plates. We present zircon U–Pb–Hf isotopes, whole‐rock geochemistry, and Sr–Nd isotopes for the intrusions from Maizhokunggar, southern Lhasa Terrane. The zircon U–Pb dating indicates that two episodes of magmatism occurred in the Maizhokunggar region, ca. 70 Ma diorites and ca. 60 Ma granitoids. The ca. 70 Ma diorites are medium‐K calc‐alkaline and characterized by pronounced high‐field‐strength element depletion and light rare earth element enrichment, similar to arc‐type rocks. They have homogeneous (87Sr/86Sr)i ratios (0.70378–0.70424) and εNd(t) values (+2.6 to +3.4), and εHf(t) (+5.9 to +13.0) with relatively young depleted mantle model ages (307–762 Ma), suggesting that they were generated from the juvenile mafic lower crust induced by the underplating of basaltic magmas from depleted mantle wedge. The ca. 60 Ma granitoids, Kajiacun (KJC) granodiorites, and Qulongxue (QLX) and Bangdacun (BDC) monzogranites are high‐K series and metaluminous to weakly peraluminous. The KJC granodiorites with high Sr/Y ratios (25–43) are adakitic and were likely derived from partial melting of a thickened lower crust. The BDC monzogranites have more evolved Sr–Nd–Hf isotopes and older Nd–Hf model ages than the QLX monzogranites. These geochemical variations were mainly controlled by the fractionation crystallization with assimilation of ancient crustal materials. We propose that at ca. 70 Ma, the subduction of the Neo‐Tethys oceanic slab triggered the partial melting of the juvenile lower crust and formed the diorites with arc affinity, and then the initial collision (>60 Ma) between the Indian and Asian plates caused locally thickened lower crust, resulting in adakitic granodiorites. Our study sheds light on the lithospheric scale magma evolution from the deep mantle to the shallow crust during the critical geodynamic transition to collision, and early uplift. [ABSTRACT FROM AUTHOR]

Snow on the Tibetan Plateau (TP) is an important signal for the prediction of East Asian climate. In this study, the relationship between the TP spring snowmelt and spring and summer precipitation in Northwest China (NWC) was investigated, along with the possible mechanisms linked to the impacts of snowmelt on precipitation. The results showed that the TP spring snowmelt had significant impacts on spring and summer precipitation in NWC. For example, when there was a large spring snowmelt in the central- eastern TP, the spring and summer precipitation in the Hexi Corridor and southeast NWC was excessive, especially in summer; when there was a large spring snowmelt in the northern TP, the spring and summer precipitation was deficient across the whole of NWC, while a large spring snowmelt in the western TP led to deficient spring and summer precipitation in eastern NWC but excessive precipitation in western NWC. The possible mechanisms for this included the fact that more spring snowmelt over the TP led to higher soil moisture contents, which further resulted in weakened subtropical westerly and enhanced ridge over Xinjiang. By changing the TP thermal forcing, these anomalous atmospheric circulation conditions transported water vapor into NWC, thus creating excessive summer precipitation in that region. [ABSTRACT FROM AUTHOR]

• Principles and procedures of a modified semiempirical fingerprinting strategy were clarified. • Error-ambiguity decomposition theory was valid for semiempirical fingerprinting. • Cropland was the main source of suspended sediment in the Nianchu River Basin. • Contribution from grassland was positively correlated with rainfall intensity. Quantitative information on suspended sediment sources is an important aspect of clarifying soil erosion and sediment transport processes. Sediment source fingerprinting has been a principal method used to estimate such information, and the semiempirical fingerprinting strategy is a new research direction that requires more exploration. Taking the Nianchu River Basin as a case study, this study collected suspended sediment and source soil samples. Virtual sediment mixtures were utilized as samples to train the integrated un-mixing model under the framework of the AdaBoost.RT algorithm. The effectiveness and suitability of this semiempirical fingerprinting framework in improving model accuracy were evaluated. One main finding was that if a potential base learner, i.e., the mass conservative un-mixing model with a composite fingerprint, had a correlation coefficient of the mean absolute error (MAE) with the optimal base learner less than 0.7 (high diversity) and its average MAE ranking was before the first quartile among all base learners on the training dataset (high accuracy), the model accuracy could be effectively improved through the training process. Moreover, cropland close to the river channel with an area ratio of only 8.6% consistently contributed more than 50% of the suspended sediment in the Nianchu River Basin during the wet period. Moreover, the relative contributions from the cropland and grassland showed a negative and positive linear relationship with rainfall intensity, respectively, indicating increased sediment connectivity from grasslands to river channels under rainfall conditions. This study confirmed that the error-ambiguity decomposition theory is valid in the context of the semiempirical fingerprinting framework. The diversity and accuracy of the potential base learners should be the key aspects to simultaneously consider in determining whether to use a theoretical or semiempirical fingerprinting strategy. [ABSTRACT FROM AUTHOR]

The Qilian Shan, located along the northeastern margin of the Tibetan Plateau, has experienced multiple episodes of tectonic deformation, including Neoproterozoic continental breakup, early Paleozoic subduction and continental collision, Mesozoic extension, and Cenozoic intracontinental orogenesis resulting from the India-Asia collision. In the central Qilian Shan, pre-Mesozoic ophiolite complexes, passive-continental margin sequences, and strongly deformed forearc strata were juxtaposed against arc plutonic/volcanic rocks and ductilely deformed crystalline rocks during the early Paleozoic Qilian orogen. To better constrain this orogen and the resulting closure of the Neoproterozoic-Ordovician Qilian Ocean, we conducted an integrated investigation involving geologic mapping, U-Th-Pb zircon and monazite geochronology, whole-rock geochemistry, thermobarometry, and synthesis of existing data sets across northern Tibet. The central Qilian Shan experienced two phases of arc magmatism at 960-870 Ma and 475-445 Ma that were each followed by periods of protracted continental collision. Integrating our new data with previously published results, we propose the following tectonic model for the Proterozoic-Paleozoic history of northern Tibet. (1) Early Neoproterozoic subduction accommodated the convergence and collision between the South Tarim-Qaidam and North Tarim-North China continents. (2) Late Neoproterozoic rifting partially separated a peninsular Kunlun-Qaidam continent from the southern margin of the linked Tarim-North China craton and opened the Qilian Ocean as an embayed marginal sea; this separation broadly followed the trace of the earlier Neoproterozoic suture zone. (3) South-dipping subduction along the northern margin of the Kunlun-Qaidam continent initiated in the Cambrian, first developing as the Yushigou supra-subduction zone ophiolite and then transitioning into the continental Qilian arc. (4) South-dipping subduction, arc magmatism, and the convergence between Kunlun-Qaidam and North China continued throughout the Ordovician, with a trenchparallel intra-arc strike-slip fault system that is presently represented by high-grade metamorphic rocks that display a pervasive right-lateral shear sense. (5) Counterclockwise rotation of the peninsular Kunlun-Qaidam continent toward North China led to the closure of the Qilian Ocean, which is consistent with the right-lateral kinematics of intra-arc strike-slip faulting observed in the Qilian Shan and the westward tapering mapview geometry of Silurian flysch-basin strata. Continental collision at ca. 445-440 Ma led to widespread plutonism across the Qilian Shan and is recorded by recrystallized monazite (ca. 450-420 Ma) observed in this study. Our tectonic model implies the parallel closure of two oceans of different ages along the trace of the Qilian suture zone since ca. 1.0 Ga. In addition, the Qilian Ocean was neither the Proto- nor Paleo-Tethys (i.e., the earliest ocean separating Gondwana from Laurasia), as previously suggested, but was rather a relatively small embayed sea along the southern margin of the Laurasian continent. We also document >200 km of Cenozoic north-south shortening across the study area. The observed shortening distribution supports models of Tibetan Plateau development that involve distributed crustal shortening and southward underthrusting of Eurasia beneath the plateau. This India-Asia convergence-related deformation is focused along the sites of repeated ocean closure. Major Cenozoic left-slip faults parallel these sutures, and preexisting subduction-mélange channels may have facilitated Cenozoic shortening and continental underthrusting. [ABSTRACT FROM AUTHOR]

Precipitation is one of the most important hydrometeorological components of the Tibetan Plateau (TP). The relationships between precipitation and topography in the TP were investigated using 17 years of Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) data and 2 years of Global Precipitation Measurement (GPM) dual-frequency precipitation radar (DPR) data. First, the retrieval and total errors of the two radars were quantified in the TP using ground-based precipitation datasets. The TRMM PR and GPM DPR both significantly underestimate the precipitation, with total errors up to 40% and 53%, respectively. Then, precipitation of the two radars was corrected prior to effective application. The correction was separately performed for each river basin in the TP by adding total errors. Finally, precipitation–topography relationships were documented using corrected radar data. The main findings on precipitation–topography relationships are: (1) precipitation generally decreases with increasing elevation from 2 to 6 km in the TP. However, the trend is inverse in the Qaidam Basin which is characterized by extremely low precipitation in the interior basin and high precipitation along the windward slopes of surrounding mountains; (2) quantitative relationships between precipitation and elevation can be depicted for most exorheic basins in the TP using exponential fitting. The coefficients of determination for the fitting are higher than 0.9 in six basins; (3) the relationships based on GPM DPR data are less robust due to its fewer samples, whereas the GPM DPR probably resolves the problem of overestimating precipitation in some grid pixels with high elevation, compared to the TRMM PR; (4) three typical mountains (i.e., Himalaya, Hengduan, and Tianshan mountains) exhibit significantly negative correlation between precipitation and elevation. Particularly, there are two bands of precipitation maxima along the southern slopes of the central Himalayas (78°E–88°E), corresponding to the two-step topography, which affects the vegetation distribution. This study provides insights into the precipitation–topography relationships in the TP and its surrounding regions based on data from spaceborne precipitation radars. [ABSTRACT FROM AUTHOR]

The topography evolution of the southeastern Tibetan Plateau provides a constraint for evaluating various geodynamic models of plateau formation. We reconstruct the Paleocene to Eocene paleoelevation of the Cenozoic Gonjo basin in the Qiangtang terrane, using oxygen and carbon stable isotopic results from pedogenic carbonates of the lower Ranmugou Formation. Lithofacies associations indicate that the lower Ranmugou Formation was deposited in alluvial fan and fluvial floodplain environments. U-Pb dating of volcanics within the middle Ranmugou Formation constrains the deposition of the lower Ranmugou Formation as prior to 43.2 Ma. Paleoelevations are calculated using both a thermodynamic model and an empirical relationship. The empirical relationship of elevation-δ 18 O is determined from a series of modern water samples. Calculated paleoelevations indicate that the Gonjo basin attained a minimum average elevation of 2100–2500 m in the early Eocene. Together with recent paleoaltimetry studies in the region, it can be concluded that the crust of southeastern Tibetan Plateau was already thickened by that time. The calculation is based on the section in northern Gonjo basin, where δ 18 O values of paleosol nodules appear to be unaltered, but we cannot rule out the possibility that δ 18 O values of the pedogenic carbonates had been partially reset. Our preliminary results favor tectonic models compatible with pre-Miocene uplift of the SE-central Tibetan Plateau. [ABSTRACT FROM AUTHOR]