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Quaternary volcanoes from the southeastern Tibetan Plateau occur at the Tengchong volcanic field (TVF). The Daliuchong volcano is the largest volcano in the TVF, which has the most felsic compositions with explosive eruptions. The eruption history and origin of the Daliuchong volcano are a matter of debate. In the present paper, we report the groundmass K-Ar ages, whole-rock Sr-Nd-Pb-Hf isotopes, zircon U-Pb ages, and Hf-O isotopic compositions for the Daliuchong volcano to constrain its eruption history and petrogenesis. The groundmass K-Ar ages and zircon U-Pb ages indicate mid-Pleistocene (0.6 Ma to 0.3 Ma) eruptions. The presence of zircon phenocrysts with enriched mantle-like O-Hf isotopes (δ18O < 6‰, and εHf about −2) suggests the involvement of mantle-derived basaltic magmas. The whole-rock Pb isotope compositions and Sr-Nd isotope modeling reveal the involvement of magma from the lower crust. The zircon xenocrysts reveal previously unrecognized 20-Ma magmatic activity at the TVF and contamination of late Cretaceous (66–80 Ma) S-type granites during the formation of the Daliuchong dacites. The dacite magma at Daliuchong was formed by mixing of the mantle-derived magma and lower-crust-derived magma and subsequently contaminated by upper crustal materials, including late Cretaceous S-type granitic rocks. [ABSTRACT FROM AUTHOR]

The Gated Recurrent Unit (GRU) neural network has great potential in estimating and predicting a variable. In addition to radar reflectivity (Z), radar echo-top height (ET) is also a good indicator of rainfall rate (R). In this study, we propose a new method, GRU_Z-ET, by introducing Z and ET as two independent variables into the GRU neural network to conduct the quantitative single-polarization radar precipitation estimation. The performance of GRU_Z-ET is compared with that of the other three methods in three heavy rainfall cases in China during 2018, namely, the traditional Z-R relationship (Z=300R1.4), the optimal Z-R relationship (Z=79R1.68) and the GRU neural network with only Z as the independent input variable (GRU_Z). The results indicate that the GRU_Z-ET performs the best, while the traditional Z-R relationship performs the worst. The performances of the rest two methods are similar. To further evaluate the performance of the GRU_Z-ET, 200 rainfall events with 21882 total samples during May–July of 2018 are used for statistical analysis. Results demonstrate that the spatial correlation coefficients, threat scores and probability of detection between the observed and estimated precipitation are the largest for the GRU_Z-ET and the smallest for the traditional Z-R relationship, and the root mean square error is just the opposite. In addition, these statistics of GRU_Z are similar to those of optimal Z-R relationship. Thus, it can be concluded that the performance of the GRU_Z-ET is the best in the four methods for the quantitative precipitation estimation. [ABSTRACT FROM AUTHOR]

Purpose anterior cervical decompression and fusion is a common surgical procedure. Traditionally, experienced doctors observe X-ray films regularly examined by patients to determine postoperative conditions by observing the tiny movements between the limited vertebral bodies. But it is not accurate. This may lead to error diagnostics and serious deterioration of the condition and secondary injury to the patient and will also put a greater financial burden on them. Doctors need a quantitative standard to determine small motion with limited vertebral landmarks after surgery. Computer vision technology is needed to match the over-extension and over-flexion cervical vertebral body to provide objective measurement data for further quantification of intervertebral activity. Based on conventional scheme, the point mean square error is used as the evaluation criterion of the matching effect, and the iterative matching scheme is proposed to improve the stability of the original scheme. The cervical X-ray films of patients from the China–Japan Friendship Hospital were collected as samples to verify the reliability of the scheme. Compared with the existing image matching schemes based on feature points, our scheme is superior in matching effect, matching speed and stability. This scheme can provide a solid foundation for further assisting doctors in the study of rehabilitation after anterior cervical fusion. [ABSTRACT FROM AUTHOR]

With the 1 h-averaged data of atmospheric precipitable water vapor (PWV) for 2015–2018 retrieved from 18 ground-based Global Positioning System (GPS) observation stations near Poyang Lake (PL), China, the diurnal variations of the PWV during midsummer (July-August) are studied by the harmonic method. Results show that significant diurnal variations of PWV are found at the 18 GPS stations. The harmonics with 24 h cycle (diurnal cycle) over PL (i.e., Duchang and Poyang) and Nanchang city only have about 50% (or even smaller than 50%) of variance contribution with the amplitude of about 0.2 mm, while above 70% (or even 80%) of variance contribution occurs elsewhere around PL, with the amplitude of about 0.9 mm. The harmonics with diurnal cycles in most stations peak from afternoon to evening (i.e., 1200-2000 LST), but one exception is Duchang site, where the diurnal cycle peaks in the morning (i.e., 1000 LST). Moreover, the harmonics with 12 h cycle (semidiurnal cycle) have the relatively uniform amplitude of about 0.2 mm, but their variance contributions show uneven distribution, with the contributions of about or above 50% in PL and Nanchang city (the semidiurnal cycles peak about 0000 LST or 1200 LST) and below 30% (or even 10%) in other areas. The preliminary diagnosis analysis shows that the diurnal variation of the low-level (below 850 hPa) air temperature (increasing after the sunrise, decreasing after the sunset, and peaking around 1400-1800 LST) may be responsible for the diurnal cycle. Moreover, in PL (Duchang and Poyang) and Nanchang city, the effects (heating or cooling) of lake and urban, the diurnal variation of the 10 m wind over PL, and the acceleration of PL on overlying air also contributed to the diurnal variation of PWV. [ABSTRACT FROM AUTHOR]

BACKGROUND: Curcumin pre-conditioning can alleviate liver injury induced by limb ischemia/reperfusion (l/R), but whether curcumin post-conditioning has protective effect against liver cold l/R injury and its mechanism are still poorly studied. OBJECTIVE: To investigate the effects of curcumin post-conditioning on hepatocyte apoptosis in rats with liver cold l/R injury in rats. METHODS: Eighty adult male Sprague-Dawley rats were randomly divided into four groups (n=20 per group) by using a random number table: sham group, l/R group, curcumin post-conditioning group (l/R+Cur group), and dexamethasone group {l/R+Dex group). The liver blood flow was completely blocked. Then the splenic vein and the adrenal vein were used as the inflow and outflow tracts to inject 0 °C compound Ringer lactate solution followed by cold perfusion for 30 minutes. After stopping cold perfusion, the proximal splenic vein and the right adrenal vein were ligated to remove the spleen, and then the blood flow in the liver restored. The cold l/R model was successfully established. After 30 minutes of cold ischemia, 60 mg/kg curcumin was injected into the rat tail vein in the l/R+Cur group, 0.5 mg/kg dexamethasone was injected into the rat tail vein in the l/R+Dex group, and the same amount of saline was injected in the other groups. Blood sample was taken from the carotid artery at 6 hours after reperfusion. Serum levels of aspartate aminotransferase and alanine transferase were detected. Then the rats were sacrificed to detect malondialdehyde level in liver tissue, observe liver pathological changes by hematoxylin-eosin staining, measure hepatocyte apoptosis index by Hoechst 33258 staining, detect expression of Bcl-2 and Bax protein by western blot, expression of caspase-9 mRNA by RT-PCR, and levels of tumor necrosis factor-α and interleukin-1β by ELISA. RESULTS AND CONCLUSION: Compared with the sham group, aspartate aminotransferase, alanine transferase, malondialdehyde levels and apoptosis index in the l/R group increased significantly (P < 0.05). Hematoxylin-eosin staining showed a large number of inflammatory cells infiltrated in the hepatic sinusoids, eosinophilic changes of hepatocytes, cytoplasmic loosening, balloon-like changes of hepatocytes, occasional patchy necrosis, and scattered punctate necrosis foci in the l/R group. The l/R group had significantly decreased expression of Bcl-2, and increased expression of Bax (P < 0.05), Caspase-9 mRNA, tumor necrosis factor-α and interleukin-1β (P < 0.05). Compared with the l/R group, aspartate aminotransferase, alanine transferase, malondialdehyde levels and apoptosis index in the l/R+Cur group decreased significantly (P < 0.05). Hematoxylin-eosin staining showed that inflammatory infiltration in the hepatic sinusoids decreased significantly, eosinophilic and balloon-like hepatocytes decreased significantly, but occasionally a small amount of scattered punctate necrosis was observed in the l/R+Cur group. There was significantly increased Bcl-2 expression, and significantly decreased Bax (P < 0.05), Caspase-9 mRNA, tumor necrosis factor-α and interleukin-1β (P < 0.05). No significant differences were observed between l/R+Cur group and l/R+Dex group (P > 0.05). In a word, curcumin-post conditioning can alleviate liver injury induced by cold l/R in rats. Its mechanism may be related to down-regulation of Bci-2/Bax ratio, inhibition of caspase-9 m RNA expression, and reduction of the release of tumor necrosis factor-α and interleukin-1β. therefore playing an anti-apoptotic role in liver protection. [ABSTRACT FROM AUTHOR]

• Magnetite-ilmenite pairs occur in Holocene Tengchong volcanics from SE Tibet. • Post-collisional Tengchong magmas are rather reducing (△FMQ = −1.8 to −0.7). • Reduced Tengchong magmas may exemplify other post-collisional magmas on Tibet. • High Fe-Ti oxide and Ti-in-zircon temperatures indicate warm storage of magmas. Rapidly cooled and well-preserved magnetite and ilmenite in young volcanic rocks provide good samples for constraining the magmatic redox conditions. We report chemical compositions of magnetite and ilmenite from the youngest Tengchong volcanoes at the southeastern margin of the Tibetan Plateau, to constrain the oxygen fugacity and temperatures for the Tengchong magmas. Oxygen fugacity values (△FMQ) relative to the fayalite-magnetite-quartz (FMQ) buffer are −1.8 ∼ −0.7 (averaging −1.1 ± 0.4) for Dayingshan; −1.3 ∼ −0.7（averaging −1.1 ± 0.3） for Maanshan; and −1.3 for Heikongshan. The temperatures for magnetite-ilmenite pairs of Tengchong lavas range from 789 to 1090 °C. The relatively reducing oxygen fugacity values (△FMQ = −1.8 ∼ −0.7) of the Tengchong magmas are significantly lower than those oxidizing arc magmas (△FMQ = +0.5 ∼ +3.5). The reduced magmas at Tengchong may exemplify other Quaternary post-collisional lavas of the Tibetan Plateau. The crystallization temperatures from mineral-liquid equilibrium are 1160–1192 °C for olivine, 1049–1110 °C for plagioclase, 978–1122 °C for clinopyroxene, 789–1090 °C for Fe-Ti oxides, 743–792 °C for zircon. The high Fe-Ti oxide temperature and Ti-in-zircon temperature indicate warm magmatic conditions (>750 °C) prior to eruptions of Tengchong magmas. [ABSTRACT FROM AUTHOR]

Western Anatolia (WA) hosts numerous I-and S-type plutons with variable compositions. This paper presents new comprehensive geology, petrography, bulk-rock and mineral chemistry, Sr Nd isotope, zircon U Pb, biotite and hornblende Ar/Ar and first apatite U Th / He age data for seven plutons (Baklan, Evciler, Eybek, Ilıca-Şamlı, Kozak, Uludağ, Yenice) in WA. Western Anatolia granitoid plutons (WAGPs) are mainly granodiorite, with minor monzonite, diorite, quartz monzonite and granite. The dominant minerals are K-feldspar (usually orthoclase and rarely microcline), plagioclase (albite, oligoclase), amphibole (hornblende), biotite, quartz, and accessory minerals are titanite, zircon, apatite, and opaques. The crystallization temperatures are relatively uniform (640-740 °C) but pressures range from those typical of the upper crust to those typical of the mid crust. The plutons are characterized by moderate to high SiO 2 (58.1–73.7 wt%), K 2 O (2.1–6.9 wt%), and relatively low P 2 O 5 (0.03–0.60 wt%) and most are I-type and metaluminous, except for the Uludağ pluton that is S-type. They are enriched in large ion lithophile elements (LILEs e.g. U, Th, Rb, and K), light rare earth elements (LREEs) and Pb, and depleted in heavy rare earth elements (HREEs), high field strength elements (HFSE, e.g. Nb, Ti) and Sr, Ba and P relative to other LILEs. The plutons display small Eu anomalies (Eu/Eu*: 0.17–1.15) due to probaly suppression of feldspar fractionation/or partial melting of lower crust. They have relatively high initial 87Sr/86Sr = 0.705775–0.708357 and low initial 143Nd/144Nd = 0.512290–0.512581. The LA-ICP-MS 206Pb 238U age analyses of zircon in addition to 40Ar/39Ar dating of hornblendes and biotites suggest that the plutons were emplaced between 29.4 Ma and 19.8 Ma and cooled with a relatively high rate (∼363 °C/Ma). These ages correlate with the collision between the Sakarya Zone and Anatolide–Tauride Platform in Rupelian to Burdigalian time. The (U Th)/He apatite ages range from 19.8 Ma to 7.6 Ma, for the WA granitoid plutons and indicates that the crustal terrains hosting the seven plutons had complex exhumation histories within their arc environment. Consequently, these ages constrain the crystallization, cooling and exumation times of the Oligocene to Miocene plutons in a post-collisional setting on the northern margin of Gondwana. [Display omitted] • The plutons emplaced and cooled between Rupelian and Burdigalian. • They had distinct exhumation histories in a post-collisional system. • The plutons were likely formed by melting of the lower crust. • Fractional Crystallization played minor role in their evolution. [ABSTRACT FROM AUTHOR]

A method named BTREC, which is in fact an extension of tracking a radar echo by cross-correlation (TREC) method, is proposed based on the Barnes filter in this paper. BTREC is an efficient objective analysis method for smoothing the motion vectors of radar echo patterns. A comparative analysis of the BTREC vectors and the COTREC (another extension of TREC, which is restricted by the 2D continuity equation) vectors is conducted. The results show that the BTREC method corrects the noise and inconsistencies in TREC vectors (often induced by shielding, ground clutter, and rapid morphological changes of the radar patterns) more thoroughly than COTREC. Then the BTREC, COTREC, and TREC methods are applied to extrapolate the real radar echo pattern over Jiangxi Province in China for two cases (1900–2100 UTC 4 June and 0900–1100 UTC 30 June 2018). Results show that the BTREC method performs the best out of the three methods to forecast the radar echo patterns in the following 1 and 2 h, and has the least distortion. To further confirm that, 892 radar composite reflectivity mosaic images with precipitation in summer (June–August) over Jiangxi are collected to test the three methods. The results show that in the 1- and 2-h extrapolations, the mean differences of the threat score (TS), correlation (CORR), and probability of detection (POD) between BTREC and TREC are obviously more than 0, while that of the false alarm ratio (FAR) is remarkably less than 0 (the threshold to identify whether a grid is correctly predicted is set to 10 dBZ). Although the mean difference of TS, CORR, POD, and FAR between COTREC and TREC have similar variation, their magnitudes are obviously decreased (especially for the 2-h extrapolation). This further indicates that the BTREC method obviously improves the forecast of the radar echo pattern within the next 2 h compared to the COTREC and TREC methods. [ABSTRACT FROM AUTHOR]

Using echo-top height and hourly rainfall datasets, a new reflectivity-rainfall (Z-R) relationship is established in the present study for the radar-based quantitative precipitation estimation (RQPE), taking into account both the temporal evolution (dynamical) and the types of echoes (i.e., based on echo-top height classification). The new Z-R relationship is then applied to derive the RQPE over the middle and lower reaches of Yangtze River for two short-time intense rainfall cases in summer (2200 UTC 1 June 2016 and 2200 UTC 18 June 2016) and one stratiform rainfall case in winter (0000 UTC 15 December 2017), and then the comparative analyses between the RQPE and the RQPEs derived by the other two methods (the fixed Z-R relationship and the dynamical Z-R relationship based on radar reflectivity classification) are accomplished. The results show that the RQPE from the new Z-R relationship is much closer to the observation than those from the other two methods because the new method simultaneously considers the echo intensity (reflecting the size and concentration of hydrometers to a certain extent) and the echo-top height (reflecting the updraft to a certain extent). Two statistics of 720 rainfall events in summer (April to June 2017) and 50 rainfall events in winter (December 2017) over the same region show that the correlation coefficient (root-mean-squared error and relative error) between RQPE derived by the new Z-R relationship and observation is significantly increased (decreased) compared to the other two Z-R relationships. Besides, the new Z-R relationship is also good at estimating rainfall with different intensities as compared to the other two methods, especially for the intense rainfall. [ABSTRACT FROM AUTHOR]

After a tropical cyclone (TC) making landfall, the numerical model output sea level pressure (SLP) presents many small-scale perturbations which significantly influence the positioning of the TC center. To fix the problem, Barnes filter with weighting parameters C=2500 and G=0.35 is used to remove these perturbations. A case study of TC Fung-Wong which landed China in 2008 shows that Barnes filter not only cleanly removes these perturbations, but also well preserves the TC signals. Meanwhile, the centers (track) obtained from SLP processed with Barnes filter are much closer to the observations than that from SLP without Barnes filter. Based on the distance difference (DD) between the TC center determined by SLP with/without Barnes filter and observation, statistics analysis of 12 TCs which landed China during 2005–2015 shows that in most cases (about 85%) the DDs are small (between −30 km and 30 km), while in a few cases (about 15%) the DDs are large (greater than 30 km even 70 km). This further verifies that the TC centers identified from SLP with Barnes filter are more accurate compared to that directly obtained from model output SLP. Moreover, the TC track identified with Barnes filter is much smoother than that without Barnes filter. [ABSTRACT FROM AUTHOR]

Post-collisional volcanic rocks on the Tibetan Plateau and its margins contain valuable information about the geodynamic processes associated with this Cenozoic continent-continent collision. The Quaternary Tengchong volcanic field at the southeastern margin of the Tibetan Plateau formed high-potassium calc-alkaline volcanic rocks. Herein, we present comprehensive Nd-Sr-Pb-Hf isotopic and elemental data for trachybasalts, basaltic trachyandesites, and trachyandesites from four Quaternary Tengchong volcanoes (Maanshan, Dayingshan, Heikongshan, and Laoguipo) in order to understand their magma genesis and evolution as well as tectonic significance. Good correlations between SiO 2 content and the ratios 87 Sr/ 86 Sr, 143 Nd/ 144 Nd, 206 Pb/ 204 Pb, and 177 Hf/ 176 Hf for these Quaternary volcanics strongly suggest that the combined assimilation and fractional crystallization (AFC) was an important process in the origin of basaltic trachyandesites and trachyandesites. High Y and Yb contents and low Sr/Y ratios of these basaltic trachyandesites and trachyandesites are uncharacteristic of adakites that formed by partial melting of eclogitic lower crust or partial melting of basaltic oceanic crust with eclogite as a restite. A combined assimilation-fractional crystallization model is proposed for these basaltic trachyandesites and trachyandesites. Nd-Sr-Pb-Hf isotopes for the uncontaminated Tengchong magma (trachybasalts with SiO 2 < 52.5 wt.% and MgO > 5.5% wt.%) reflect a heterogeneous enriched mantle source. High Th/U, Th/Ta, and Rb/Nb ratios and Nd-Sr-Pb-Hf isotope characteristics of the uncontaminated magmas suggest that the enriched mantle beneath Tengchong formed as a result of subduction of clay-rich sediments, which probably came from the Indian continental plate. Partial melting of the enriched mantle was generated by deep continental subduction coupled with recent regional extension in the Tengchong area. [ABSTRACT FROM AUTHOR]

Four experiments, uniform experiment (UF) with a constant lake surface temperature (LST), spatial experiment (SP) with the space change of LST, temporal experiment (TM) with the time change of LST and spatiotemporal experiment (SP-TM) with the space and time changes of LST, were performed to explore the response of a convection over Poyang Lake (PL) in China on 12–13 August 2015 to the time and space variations of LST based on the Weather Research and Forecasting (WRF) model. Simulation results show that the spatiotemporal variation of LST significantly affects the convection. Compared with the observation, the UF and SP simulated convection advances about 3 h, with greater coverage and a more southerly location, while the TM simulated convection also advances about 3 h, with smaller coverage. The SP-TM simulated convection is well consistent with the observation in time evolution, coverage, location and intensity, improving the simulation of the convection greatly. The diagnostic analysis shows that the time and space variations of LST in PL change the atmospheric stability and low-level uplift movement by adjusting low-level air temperature, humidity and wind over PL and its nearby areas, finally affecting the development of the convection. The fact that convection, atmospheric stability and near-surface wind over the lake are sensitive to the spatiotemporal variation of LST strongly suggests the need to monitor and forecast the distribution and time evolution of LST for accurate prediction of convection over PL. • Four experiments are performed to explore the response of a convection over Poyang Lake on lake surface temperature (LST). • The spatiotemporal variation of LST can significantly affect the initiation, location and intensity of the convection. • After considering the time and space changes of LST, the model improves the simulation of the convection obviously. • The spatiotemporal variation of LST affects the convection through regulating the near surface wind, LFC and CAPE. [ABSTRACT FROM AUTHOR]

Two types of Cenozoic lavas composed of high magnesium andesites (HMAs) and high-K basalts (HKBs) occur in the northern Songliao Basin (NSB), Northeastern China. This study presents K-Ar geochronology, olivine phenocryst compositions, whole-rock major and trace element, and Sr-Nd-Pb-Hf isotopic compositions of HMAs from Menluhe and Xunke in NSB, and discuss the origin of high Nb/Ta signature and mantle source heterogeneity of these lavas. The HMAs from Menluhe and Xunke erupted between 0.20 and 1.72 Ma. These andesitic lavas display negative ε Nd (−3.2 ∼ −10.4) and ε Hf (−3.3 ∼ −19.3), elevated 87Sr/86Sr (0.7048–0.7061), and unradiogenic Pb isotopes (206Pb/204Pb = 16.50–17.10), similar to those of the high potassium basalts (HKBs) in Keluo-Wudalianchi-Erkeshan near the HMA fields. Within the HMAs, the olivine phenocrysts have high Ni contents and elevated Fe/Mn (69.1–93.9, average 78.1) compositions. The petrology index FCKANTMS (Yang et al., 2019) values range from 0.57 to 0.75. Both the olivine compositions and the petrology index support a pyroxene source. Enrichments in large ion lithophile elements (Ba, K and Sr) and depletions in high field-strength elements (Nb, Ta, Th and U), with anomalously high Nb/Ta ratios (18.9–22.6) in the andesite, are consistent with a combined metasomatism of carbonatite and silicate melts to the lithospheric mantle. HMAs tend to occur in rift basins, while HKBs tend to occur in off-rift zones, suggesting a close magmatic-tectonic correlation. Metasomatism (by carbonatite and silicate melts) and rifting may form a positive feedback mechanism, resulting in coupled HMAs, HKBs and rifts in NSB. • Carbonatite-rich and silicate-rich melts contribute to the lithospheric mantle origin of the high Mg andesites. • Carbonatite-rich melts may be an agent delivering the high Nb/Ta and EM1 signatures. • The HMAs and HKBs volcanism in the Northern Songliao Basin occur as a result of on-going lithosphere extension and thinning. [ABSTRACT FROM AUTHOR]

The Pamir-Karakorum is one of the most important regions for our understanding the Tethys evolution. Although it is commonly known that the northward subduction of the Neo-Tethys Ocean induced the formation of the magmatic arc in Southern Pamir, the temporal-spatial configuration of the arc—back-arc during the Neo-Tethys evolution remains unclear. In this study, we report sedimentary feature, petrography, zircon U Pb ages and Hf O isotope compositions as well as bulk-rock and mineral geochemistry of the well-preserved Cretaceous volcanic sequence in Chinese Wahan Corridor at South Pamir. The volcanic sequence is mainly composed of phenocrysts- bearing basalt- andesites with minor rhyolite and volcaniclastic rock. Zircon U Pb ages reveal the basalt-andesite sequence erupted at 100–98 Ma. Bulk-rock geochemistry defines their potassic calc-alkaline signature and both their rock association and elemental geochemistry share most features of the continental arc volcanic sequences. On the other hand, they have variably enriched Nd isotope compositions with ε Nd (t) varying from −5.9 to −9.6, coupled with their enriched zircon Hf isotope signature with ε Hf (t) between −13 to −8. Whole-rock geochemistry and zircon oxygen isotope compositions (average δ18O = 7.74 ± 0.14) demonstrate that the primitive magma of the basalt-andesites were derived from partial melting of a metasomatized sub-continental lithospheric mantle and underwent variable assimilation fractional crystallization. Late Jurassic to Cretaceous volcanic-sedimentary sequences and coeval voluminous arc-like granodiorite and granites are widely distributed along the Southern Pamir. In the Central Pamir and further north, late Jurassic to Cretaceous sequences resemble features of back-arc basins. Taken together, we suggest that a northward low-angle or flat subduction of the Neo-Tethys Ocean along the Shyok zone was geodynamically related to the formation of the broad magmatic arc in South Pamir-Karakorum and the back-arc basins north of the South Pamir. [Display omitted] • Arc-like Cretaceous basalt-andesite sequence in Southern Pamir (SP) erupted at ~100 Ma. • Architecture of the late Jurassic-Cretaceous arc-back-arc at Pamir was constructed. • Flat subduction of the Neo-Tethys Ocean produced the Cretaceous igneous rocks in SP. [ABSTRACT FROM AUTHOR]

The Changbai (or Baitoushan, Paektu) volcano on the China/North Korea border is best known for its climactic caldera-forming eruption of 100km3 of comendite materials 1000years (1ka) ago. The polygenetic Changbai volcano also erupted moderate-volume pre-caldera comendite lava at ~4ka and small-volume post-caldera trachyte ignimbrite at ~0.3ka. Here we report 238U–230Th disequilibrium ages of zircons from lavas and ignimbrites of the pre-caldera (~4ka), syn-caldera (1ka), and post-caldera (~0.3ka) events. The zircon isochron ages are 12.2±1.1ka (2σ) for the 4-ka comendite lava and 12.2±1.7ka for the 1-ka comendite ignimbrite. Zircons from the 0.3-ka trachyte ignimbrite exhibit 3 respective peaks at 2.6±1.8ka, 130±10ka and >230ka. The indistinguishable zircon ages for the 4-ka pre-caldera eruption of comendite lava and the 1-ka caldera-forming eruption of comendite pumice and ignimbrite suggest that the 4-ka lava provides an early sampling of a much larger magma body at depth and thus serves as a kind of petrologic early-warning signal. In addition, the 4-ka lava may represent the lowest-temperature magma in the roof zone of a thermally zoned magma chamber that usually escapes first. The distinctive multi-modal zircon age distributions of the 0.3-ka trachytic eruption, however, reveal that this post-caldera eruption tapped a different magma body and indicate that Changbai's magmatic plumbing system had changed after the 1-ka caldera-forming climactic eruption. Our results suggest very short zircon and magma residence times for the Changbai volcano (8kyr for the 4-ka eruption, 11–12kyr for the 1-ka eruption and 2.3kyr for the 0.3-ka eruption). [ABSTRACT FROM AUTHOR]

Abstract: We report U-series disequilibrium data in the youngest volcanic rocks from Maanshan, Dayingshan and Heikongshan volcanoes in the Tengchong volcanic field, representing the only 3 volcanoes from the Indo-Asian suture zone (southwestern Tibet to western Yunnan) that are young enough to preserve 238U–230Th disequilibrium. The most striking feature of these young Tengchong lavas is their extremely low (230Th/232Th) (0.303 to 0.376) and (238U/232Th) (0.289 to 0.360) activity ratios (or ultra-high Th/U concentration ratio). These young lavas also show small to moderate (4% to 10%) 230Th excesses. Such 230Th excesses, together with tomographic results, suggest that partial melting initiated at depths greater than 75km in the garnet stability field. U-series isotope data, together with major and trace element and Nd–Sr–Pb isotope data, indicate that Tengchong lavas are derived from partial melting of an enriched subcontinental lithospheric mantle. The ultra-high melt Th/U concentration ratios of 9.5±0.7 further indicate recycling of continentally derived clay-rich mature sediments or mudstones into the SE Tibetan mantle. The materials with ultra-high Th/U ratios may come from the clay-rich mature sediments from Indian Ocean or Neo-Tethyan Ocean or the mudstones/shales from the subducted Indian continental plate. [Copyright &y& Elsevier]

Highlights: [•] Basalts of the Sugetbrak Formation yield two ages of 615.2±4.8Ma and 614.4±9.1Ma. [•] Tarim may have involved in the breakup of Rodinia at its late stage. [•] The Sugetbrak basalts represent low-degree meltsproduced in a rifting environment. [•] The new ages put a constraint on the timing of the Yuermeinak glaciation in Tarim. [•] We correlate the Yuermeinak glaciation with other glaciations around the world. [ABSTRACT FROM AUTHOR]

The rare occurrences of active volcanoes on the Tibetan Plateau provide a unique opportunity to investigate time scales of magma chamber processes for post-collisional potassic volcanism. This research utilizes high-spatial resolution U–Th disequilibrium dating methods to date zircons from the active Dayingshan volcano, Tengchong, SE Tibetan Plateau, which erupted last during the Holocene. Zircon crystal ages can be used to provide constraints on the magma chamber storage time. Measured zircon interiors yielded an isochron age of 87.5±6.5ka, while zircon outermost rims yielded an isochron age of 58±13ka. The calculated zircon crystal storage time for the most recent eruption is 48ka. At least two separate late Pleistocene zircon crystallization events have occurred where the older age population represents antecrysts remobilized from an earlier magmatic episode, but protracted crystallization cannot be ruled out. Regardless, the similarity in zircon age populations between Dayingshan volcano and Maanshan volcano 13km apart in the Tengchong volcanic field suggests a synchronous thermal history of the magma reservoir, possibly in an extensive interconnected magma chamber beneath the Tengchong volcanic field. [ABSTRACT FROM AUTHOR]

Abstract: The Changbaishan (Tianchi) volcano extending across the border of northeast China and North Korea erupted ~100km3 peralkaline rhyolites around 1000AD. This Millennium eruption of the Changbaishan volcano is one of the two largest explosive eruptions in the past 2000years. Here we report the results of uranium–thorium dating of zircons from the Changbaishan volcanic rocks. Our data indicate that the rhyolitic magmas were stored in the crust for only 8.2±1.2ka prior to eruption. Based on titanium-in-zircon geothermometer and alkali feldspar-glass geothermometer, the rhyolitic magmas were formed at a relatively low temperature (~740±40°C). This storage time is very short compared with other large volume catastrophic silicic eruptions. This work demonstrates that peralkaline rhyolitic magmas from the Changbaishan volcano can develop into a catastrophic eruptive phase quite quickly. [ABSTRACT FROM AUTHOR]

Abstract: Throughout the Cenozoic, post-collisional potassic volcanism has been widespread in the Tibetan Plateau, but Holocene (<10ka) volcanism is rare and has only been reported from three volcanoes near Tengchong (Yunnan Province, China) within the southeastern Tibetan Plateau. Some of the Holocene volcanic rocks are differentiated lavas with SiO2 contents of 58wt.% and contain zircon crystals. These zircon-bearing differentiated lavas provide a unique opportunity for studying magma chamber processes in an environment of thickened continental crust by using short-lived uranium–thorium (U–Th) isotopes. Here we report U–Th zircon ages from Maanshan volcano (one of the three Holocene volcanoes from Tengchong) measured by secondary ion mass spectrometry ion microprobe (SIMS) techniques. A novel part of the zircon U–Th dating is the use of shallow depth profiling of the outermost rims and its comparison to traditional “core & rim” spot analyses. The U–Th ages of zircon interiors from Maanshan volcano show bi-modal distributions. The zircon interiors from Maanshan yield an apparent U–Th isochron age of 83.5−9.0 +9.8 ka (2 sigma), with a mean square of weighted deviates (MSWD) of 5.1 that is outside the 95% confidence interval expected for a single age population. Based on mixture modeling of zircon age data, the Maanshan zircons may represent a bi-modal population with ages of 55±7ka and 91±6ka in proportions of 23% and 77%, respectively. SIMS shallow depth profiling of unpolished euhedral zircon outermost rims yield a U–Th isochron age of 53.6−5.0 +5.3 ka (MSWD of 0.92). Thus depth profiling of unpolished zircon grains to discern the age of the outermost rims is consistent with the younger of the two peaks on the bi-modal distribution. The older ∼91ka peak represents remobilized zircon antecrysts derived from an earlier episode of andesitic magmatism. The younger 55ka peak represents zircon phenocrysts that grew in the eruptible magma body itself in the build-up to the eruption. The zircon storage time in the eruptible magma body beneath Tengchong is thus about 45ka. Almost comparable temperatures and compositions between cores and rims indicate closed system evolution, rather than polybaric crystallization. [Copyright &y& Elsevier]

Abstract: Extensive (about 5000km3) basaltic magmas erupted on the Hainan Island, south China, mostly during the past 1millionyears. U–Th disequilibrium data as well as Nd, Sr, Pb isotopes and major and trace element concentrations were measured on the youngest lavas from Maanling volcano and Leihuling volcano of the Hainan Island. All the Holocene Hainan basalts display light rare earth element (LREE) enriched patterns and ocean island basalt (OIB)-type incompatible element distributions. Their ε Nd values range from +4.1 to +4.8, 87Sr/86Sr ratios vary from 0.7039 to 0.7042, and 206Pb/204Pb ratios range from 18.63 to 18.71. The Hainan lavas are characterized by their depleted Sr–Nd isotopic compositions and Dupal-like EM2 (enriched mantle 2) Pb isotope signatures with time-integrated high Th/U and 235U/Pb. The olivine tholeiites from Maanling display 18–20% 230Th excesses and the alkali olivine basalts from Leihuling show 22–32% 230Th excesses. The pronounced 230Th excesses in the Holocene basalts indicate that the Holocene Hainan lavas were produced by melting of a mantle source in the garnet stability field (>75km). Since the lithosphere thickness beneath the Hainan Island is thin (55km), the garnet peridotite mantle source for the Hainan basalts is not located in the lithospheric mantle. The Nd isotopic compositions do not indicate a highly depleted asthenospheric mantle source. We thus suggest that the EM2 mantle source for the young Hainan basalts is in the mantle transition zone or more likely lower mantle, which is consistent with a plume origin. The significant 230Th excesses also suggest slow (<1cm/year) upwelling, possibly indicative of a weakly buoyant mantle plume. The older EM2 Cenozoic basalts from Hainan, South China Sea Basin and adjacent areas may also originate from partial melting of lower mantle materials in the rising Hainan plume. [Copyright &y& Elsevier]

Abstract: Young (300 to 5500years old) dispersed intraplate volcanism characterized by small volume of melt and large compositional variability, occurred over NE China at Jingbohu, Long-gang, Tianchi and Wudalianchi. These young volcanic rocks provide ideal opportunities for investigating the mechanism of dispersed continental volcanism using short-lived uranium-series isotopes. We present systematic U-series, Nd, Sr, Pb isotope and trace element analyses of the young lavas from NE China. Jingbohu lavas display variable extents of 230Th excesses (10 to 28%) and moderately depleted Nd isotopic compositions (ε Nd = + 1.5 to + 3.3). Long-gang lavas have pronounced (33 to 35%) 230Th excesses and slightly depleted Nd isotopic compositions (ε Nd = + 0.5 to + 0.7). The Tianchi lavas display moderate (12%) 230Th excesses and slightly enriched Nd isotopic compositions (ε Nd = − 1.0 to − 1.1). 230Th enrichments in all these volcanic rocks are uncharacteristic of melts generated by subduction. The strongest evidence against the involvement of subduction-related fluids is derived from the Long-gang lavas having more than 30% 230Th excesses, low U/Th, Sr/Th and Ba/Th ratios, and positive Nb and Ta anomalies. The fluids released from the subduction of the Pacific plate under the Eurasian plate might have already been completely lost before the slab reached the mantle beneath NE China. We postulate that, in addition to the convective circulation process, the continuous piling up and upward thickening of stagnant Pacific slab in the mantle transition zone may help drive a broad asthenosphere upwelling far from the trench, leading to mantle partial melting and the formation of the young volcanoes in NE China. In addition, our U–Th disequilibrium data provide constraints on magma evolution time. The magma evolution time from low SiO2 (47.5%) basalt to higher SiO2 (50.4%) basalt at Long-gang is within 10 thousand years (10ka). The magma evolution time from trachyte to rhyolite at Tianchi volcano is also less than 10ka. If the Tianchi silicic rocks were evolved from Long-gang basaltic magmas with minor crustal assimilation, then the magma evolution time from basaltic magma to silicic magmas is less than 110 thousand years. [Copyright &y& Elsevier]

We report isotopic and chemical compositions of unusual tridymite–hercynite xenoliths in middle Miocene Niutoushan tholeiites from the southeast coastal area of China. These xenoliths are characterized by positive cerium (Ce) anomalies and extremely high Al2O3 (32–34 wt.%) and total iron oxide (20–22%). They have 87Sr/86Sr of 0.7050–0.7058, #x03B5;Nd(0) values of +3.2 to +4.2, 206Pb/204Pb ratios of 18.8–19.1, and δ18O values of +5.2‰ to +6.1‰. Their chemical and isotopic compositions suggest that these xenoliths represent preserved aluminous lateritic paleosols that are not genetically related to host tholeiites. These lateritic paleosols with strongly desilicated minerals were formed by intense chemical weathering under warm and humid tropical conditions (with annual average temperature of >19 °C and the annual rainfall of >165 cm) in SE China during the interval from 17 to 15 Ma. The formation age of the paleosols corresponds to a period characterized by slow uplift of the Himalayan–Tibetan Plateau region (and thus less consumption of CO2) after 17 Ma, and eruptions of 17–15 Ma Columbia River flood basalts, the Vogelsberg basalts, and eastern China basalts (and thus more input of CO2 into the atmosphere). The tridymite–hercynite xenoliths in the Niutoushan basalts thus preserve evidence of extraordinary climatic greenhouse conditions in the middle Miocene that would otherwise have been lost by the erosion of paleosols. [Copyright &y& Elsevier]

The only historic eruptions of potassic basalts on the Earth reported so far took place in 1719–1721 AD in the Wudalianchi area of northeast China. These historic potassic basalts are characterized by significant 230Th excesses [(230Th/238U)=1.24–1.33], and low 143Nd/144Nd (&epsiv;Nd=−5.0 to −3.7) and 206Pb/204Pb (16.8–17.1). Strong 230Th excesses, low CaO+Al2O3, and large bulk partition coefficients (D) in Rb, K, and Zr (DRb(DK>DZr>DYb>DSm) inferred from a melt-normalized spider diagram suggest phlogopite-bearing garnet peridotites as dominant source rocks. The presence of garnet peridotites as mantle source, combined with negative &epsiv;Nd in basalts and the geophysically determined lithosphere thickness in the study region (120 km), indicates the generation of these basalts at the depth of 80–120 km in the subcontinental lithospheric mantle. Dynamic melting inversion (DMI) of between-magma trace element concentration ratios and U–Th disequilibrium data suggests low-degree partial melting (5–7%) of a slow upwelling (<1.6 cm/year) mantle source, although extremely low-degree batch partial melting (0.3–0.5%) of a static source is also possible. Source Nd model ages suggest that the source rocks for the Wudalianchi basalts were metasomatized at 1.0 Ga, provided that it has not experienced multistage enrichment history. Lithospheric extension since late Tertiary in the study region was responsible for slow decompression melting of phlogopite-bearing garnet peridotites in deep subcontinental lithospheric mantle. Recent (<350 ka) subduction of the Pacific Plate may have produced lithospheric extension in the study region, but did not directly contribute subduction-related fluids to the source rocks for these potassic basalts because 230Th enrichments are uncharacteristic of melts generated by subduction. The subducted slab may have lost fluids released from subducted sediments before the slab can reach the mantle beneath NE China. [Copyright &y& Elsevier]

We report [sup 230]Th-[sup 238] disequilibrium data on mid-ocean ridge basalts recovered 5 to 40 kilometers off the ridge axis near 9°30'N of the East Pacific Rise. These data indicate near-symmetrical eruptions of normal mid-ocean ridge basalts (NMORBs) and incompatible element-enriched mid-ocean ridge basalts (EMORBs) as far as 20 kilometers off axis. Our results suggest Large-scale subsurface Lateral transport of NMORB melt at 19 to 21 centimeters per year and also provide constraints on the petrogenesis of EMORBs of off-axis origin. [ABSTRACT FROM AUTHOR]

Young zircons from volcanic rocks provide ideal samples for evaluating whole-rock and zircon Hf isotope equilibrium. We report zircon and whole-rock Hf isotopic compositions for Holocene post-collisional lavas (trachyandesites and trachytes) from Dayingshan volcano, SE Tibetan Plateau. Individual zircon ε Hf values differ from the host whole-rock value by up to 7.4ε units, and average zircon ε Hf values in individual samples are about 3ε units lower than the corresponding whole-rock ε Hf values, indicating discrepancy of zircon and whole-rock Hf isotopes. δ18O values for Dayingshan zircons vary from 6.1 to 7.8‰ and are negatively correlated with zircon ε Hf values. The decoupling of zircon/whole-rock Hf isotopic compositions is attributed to open-system magmatic processes rather than disequilibrium partial melting, as indicated by the negative correlation of zircon Hf-O isotopic compositions, as well as the correlations between whole-rock SiO 2 content and Nd-Sr-Hf isotope ratios. The decoupling of zircon/whole-rock Hf isotopic compositions in Dayingshan lavas suggest that care must be taken when using individual zircon ε Hf values to study crust-mantle evolution. This Hf isotope decoupling might be more common than previously thought in continental post-collisional volcanic rocks where open-system magmatic processes are common. • We study the youngest post-collisional volcanism on the SE Tibetan Plateau. • Average zircon ε Hf values are ~3ε units lower than their bulk-rock ε Hf values. • Zircons from Dayingshan volcano (SE Tibet) have high δ18O (6.1 to 7.8‰). • Zircon O-Hf isotopic compositions are negatively correlated. • Open-system magmatic processes in the crust occurred at Dayingshan volcano. [ABSTRACT FROM AUTHOR]

The Tengchong volcanic field in southwestern China represents rare Quaternary volcanic eruptions and associated active geothermal activities on the southeastern margin of the Tibetan plateau. The reported eruption ages for the 3 youngest Tengchong volcanoes (Heikongshan, Dayingshan, Maanshan) are highly variable (3.0–482 ka) because of the challenge to accurately and precisely date young volcanic rocks by radiometric methods. Here we use high-resolution 238U-230Th-226Ra disequilibria to constrain the eruption ages and magma evolution timescales. All 3 young volcanoes exhibit whole-rock (226Ra/230Th) disequilibrium ranging from 1.27 to 1.71, indicating eruption ages of <8 ka (5 half-lives of 226Ra). Eruption ages of 2.9–5.1 ka for Heikongshan, 3.3–4.0 ka for Dayingshan, and 2.9–3.6 ka for Maanshan are constrained by (226Ra/230Th) evolution models. This study thus suggests Holocene eruptions for all 3 volcanoes and represents the first Holocene radiometric age for Dayingshan. We also measured 238U 230Th ages of zircons from Heikongshan, Dayingshan, and Maanshan. Zircon age populations are 54.6 ± 13 ka and 94.9 ± 4.1 ka for Heikongshan, 59.6 ± 5.8 and 90.1 ± 8.4 for Dayingshan, and 53.8 ± 8.7 ka and 76.5 ± 11 ka for Maanshan. Magma residence times for all 3 volcanoes are ~50 kyr for a shallow stage and 85 kyr for a deep stage in a two-stage magma chamber system below Tengchong. The similar zircon age distributions for the 3 volcanoes from Tengchong indicate simultaneous magmatism at 90 ka and 55 ka and imply interconnected nature of these volcanoes. • We report bulk Ra Th isotope and zircon U Th isotope data for Tengchong volcanoes. • Ra Th isotopes indicate 3 Tengchong volcanoes are Holocene volcanoes. • We obtain zircon age pulses of ~55 ka and ~90 ka for these 3 volcanoes. • The magma chambers for Heikongshan, Dayingshan, and Maanshan are interconnected. • Magma residence time is 50 kyr for a shallow magma chamber and 85 kyr for a deep one. [ABSTRACT FROM AUTHOR]

We present major element, trace element and Sr-Nd-Pb-Hf isotopic compositions of the late Cenozoic basaltic rocks from Dalinor, Inner Mongolia, on the west of the Greater Hinggan Mountain Range in Northeast Asia, and discuss the origin of mantle source heterogeneity beneath Northeast Asia. The early-stage volcanoes (EV) from Dalinor produced predominantly quartz tholeiitic and olivine tholeiitic basalts whereas the late-stage volcanoes (LV) produced alkali basalts. Variations in the degree of partial melting and in fractionation crystallization could explain most of the changes in major and trace element compositions within individual groups. Trace element ratios and Sr-Nd-Pb-Hf isotope ratios between the EV and LV groups indicate a heterogeneous mantle source. The EV group is characterized by an ocean island basalt (OIB)-like spider diagram and positive anomalies of Sr, Ba and K, moderately LREE-enriched pattern ((La/Yb) N = 5.7–8.2), high Ba/Nb (10.2–16.5), and negative correlation between Dy/Yb and SiO 2. Two thirds of the EV samples have low Nb/U (<37). The source rock for the EV lavas was amphibole-bearing metasomatized lithospheric mantle. The LV lavas have high TiO 2 content (2.57–3.65 wt%), high Nb/U (42.4–58.8) and Indian-MORB-like Sr Nd isotopic compositions, indicating their asthenospheric origin. The Sr-Nd-Pb isotopic compositions of the Dalinor lava overlap those of the Southeast China basalts, and are consistent with source mixing between a depleted mantle component (DM) and an enriched mantle EM2 component. The western part of the trans-Greater Hinggan Mountain Range mantle source profile has a DM + EM2 signature, whereas the eastern part of the profile has a DM + EM1 signature. This lateral mantle source heterogeneity cannot be explained by the stagnant Pacific slab in the mantle transition zone. Instead, we propose that the EM2 component originated from the descending slab during a slab avalanche in the lower mantle near the westernmost leading edge of stagnant slab, before finally residing in the lithospheric mantle. • The mantle sources for Dalinor volcanoes are metasomatized lithosphere mantle and asthenosphere. • The lateral mantle heterogeneity has resulted in the contrasting nature of magmatism across the Greater Hinggan Mt. Range. • Originated from the lower mantle, the EM2 component affected the magma source lateral variations. [ABSTRACT FROM AUTHOR]

Post-collisional potassic volcanic rocks on the Tibetan Plateau are widespread, but geologically young (<375 ka) volcanism suitable for 238U-230Th geochronology is rare on the plateau. The geologically young Ashikule volcanic field from northern Tibet offers an excellent opportunity for studying high-resolution timescales of magmatism in continental collision zones. Here we report U-Th crystallization ages of zircons from Ashishan volcano and Wulukeshan volcano within the Ashikule volcanic field. In this study, we have identified 3 pulses of zircon crystallization at circa 70 ka, 105 ka, and 290 ka for Ashishan volcanic rocks and 1 pulse of zircon crystallization at circa 115 ka for Wulukeshan. Comparison of high-resolution zircon crystallization ages of 70 ka and 105 ka with respective eruption ages indicate that the zircon crystal residence time for the Ashishan volcano is short (<5 kyr). The presence of 290-ka zircon in a different Ashishan lava flow suggests the 270-ka volcanic pulse previously reported for other volcanoes in Ashikule volcanic field also occurred at Ashishan. The zircon crystallization age of ~115 ka for Wulukeshan volcano suggests that Wulukeshan volcano erupted later than previously inferred. Similar zircon age spectrums of ~105–115 ka for Ashishan and Wulukeshan volcanoes suggest a common interconnected subsurface magma reservoir for these two young volcanoes during Pleistocene time. Our new high-resolution U-Th zircon age data reveal that post-collisional potassic magmas below northern Tibet erupted soon after their formation (<5 kyr), in spite of their passage through thick continental crust. The high abundance (~60%) of geologically old (>375 ka) zircons demands for crystal-scale isotope studies of the widespread post-collisional lavas in continental collision zones, as the complexities cannot be resolved by bulk analysis methods alone. • We date zircons from the youngest post-collisional lavas from Tibetan Plateau. • We obtain zircon crystallization ages of 70 ka, 105 ka and 290 ka for Ashishan. • There might be an interconnected subsurface magma reservoir for 2 volcanoes. • Zircon and magma residence times for these potassic volcanism are short (<5 kyr). • Abundant (60%) of old (>375 Ka) zircons demand for crystal-scale isotope studies. [ABSTRACT FROM AUTHOR]

Olivine grains from Songshugou mylonitized peridotite massif record δ18O both lower and higher than in pristine mantle samples in North Qinling Orogen, Central China. Olivines from dunites exhibit large variations in δ18O (4.03–7.07‰), and some porphyroclasts display negative correlations between δ18O and forsterite content {Fo; [100×Mg/(Mg+Fe2+)]}. The porphyroclast cores have low-δ18O values, indicating that they formed in the oceanic lithospheric mantle prior to subduction. We attribute low-δ18O values to seawater-peridotite interaction under high-temperature conditions. The porphyroclast rims and small olivines exhibit high-δ18O values. These features suggest that high-δ18O olivines formed during mylonitization in the exhumation process. Olivines reacted with 18O-rich melt/fluids released from subducted altered oceanic basalts and continental sediments at low temperature (<610–680 °C). The 18O-rich melt/fluids selectively affected porphyroclast rims and small olivine grains. Unlike the olivines in the dunites, the olivines and orthopyroxenes in the harzburgites show limited variations in δ18O (4.21–5.45‰ and 5.5–5.8‰, respectively), due to orthopyroxene exchange with melt/fluid at a slower rate than the coexisting olivine. The preservation of the low-δ18O signature in olivines indicates a short residence time (<20 Ma) for subducting peridotites to mantle depths. [ABSTRACT FROM AUTHOR]

This paper reports lithium concentrations and isotopic compositions of olivines in the oceanized subcontinental lithospheric mantle (SCLM) peridotites of the Tibetan Yunzhug ophiolite. The results show systematic Li isotope changes with distance from the rim of olivine grains. δ7Li values of olivine in dunites decrease from + 10.46 to + 1.33‰ with increasing distance to olivine rim from 26.15 to 124.71 μm. A negative correlation of δ7Li and Li content in olivine from dunite and harzburgite indicates recent diffusive ingress of Li into the peridotites. The extremely heavy Li isotopic composition requires the seawater or seawater alteration endmember in the mixing model, and reveals Li diffusion from seawater into olivine. As in dunites, olivines in a harzburgite sample show similar variations in δ7Li as a function of distance from the grain rim (e.g., 6.01 to 1.73 in sample 14YZ13). We suggest that the behavior of Li in the oceanized SCLM peridotites may be controlled by Li diffusion from seawater, as Li activity in the liquid state is higher than the solid state in transporting Li through the olivines in the peridotites. This study supports that seawater Li diffusion is one of the important factors for the heterogeneity of mantle Li isotopes in ophiolites. [ABSTRACT FROM AUTHOR]

This paper reports lithium concentrations and isotopic compositions of olivines in the oceanized subcontinental lithospheric mantle (SCLM) peridotites of the Tibetan Yunzhug ophiolite. The results show systematic Li isotope changes with distance from the rim of olivine grains. δ7Li values of olivine in dunites decrease from + 10.46 to + 1.33‰ with increasing distance to olivine rim from 26.15 to 124.71 μm. A negative correlation of δ7Li and Li content in olivine from dunite and harzburgite indicates recent diffusive ingress of Li into the peridotites. The extremely heavy Li isotopic composition requires the seawater or seawater alteration endmember in the mixing model, and reveals Li diffusion from seawater into olivine. As in dunites, olivines in a harzburgite sample show similar variations in δ7Li as a function of distance from the grain rim (e.g., 6.01 to 1.73 in sample 14YZ13). We suggest that the behavior of Li in the oceanized SCLM peridotites may be controlled by Li diffusion from seawater, as Li activity in the liquid state is higher than the solid state in transporting Li through the olivines in the peridotites. This study supports that seawater Li diffusion is one of the important factors for the heterogeneity of mantle Li isotopes in ophiolites. [ABSTRACT FROM AUTHOR]

Objective: This study aims to construct an artificial intelligence (AI) model capable of effectively discriminating between abdominal Henoch‐Schönlein purpura (AHSP) and acute appendicitis (AA) in pediatric patients. Methods: A total of 6965 participants, comprising 2201 individuals with AHSP and 4764 patients with AA, were enrolled in the study. Additionally, 53 laboratory indicators were taken into consideration. Five distinct artificial intelligence (AI) models were developed employing machine learning algorithms, namely XGBoost, AdaBoost, Gaussian Naïve Bayes (GNB), MLPClassifier (MLP), and support vector machine (SVM). The performance of these prediction models was assessed through receiver operating characteristic (ROC) curve analysis, calibration curve assessment, and decision curve analysis (DCA). Results: We identified 32 discriminative indicators (p <.05) between AHSP and AA. Five indicators, namely the lymphocyte ratio (LYMPH ratio), eosinophil ratio (EO ratio), eosinophil count (EO count), neutrophil ratio (NEUT ratio), and C‐reactive protein (CRP), exhibited strong performance in distinguishing AHSP from AA (AUC ≥ 0.80). Among the various prediction models, the XGBoost model displayed superior performance evidenced by the highest AUC (XGBoost = 0.895, other models < 0.89), accuracy (XGBoost = 0.824, other models < 0.81), and Kappa value (XGBoost = 0.621, other models < 0.60) in the validation set. After optimization, the XGBoost model demonstrated remarkable diagnostic performance for AHSP and AA (AUC > 0.95). Both the calibration curve and decision curve analysis suggested the promising clinical utility and net benefits of the XGBoost model. Conclusion: The AI‐based machine learning model exhibits high prediction accuracy and can differentiate AHSP and AA from a data‐driven perspective. [ABSTRACT FROM AUTHOR]

Reanalysis data play a vital role in weather and climate study as well as meteorological resource development and application. In this work, the East Asia Reanalysis System (EARS) was developed using the Weather Research and Forecasting (WRF) model and the Gridpoint Statistical Interpolations (GSI) data assimilation system. The regional reanalysis system is forced by the European Centre for Medium-Range Weather Forecasts (ECMWF) global reanalysis ERA-Interim data at 6 h intervals. Hourly surface observations are assimilated by the Four-Dimension Data Assimilation (FDDA) scheme during the WRF model integration; upper observations are assimilated in three-dimensional variational data assimilation (3D-VAR) mode at the analysis moment. It should be highlighted that many of the assimilated observations have not been used in other reanalysis systems. The reanalysis runs from 1980 to 2018, producing a regional reanalysis dataset covering East Asia and surrounding areas at 12 km horizontal resolution, 74 sigma levels, and 3 h intervals. Finally, an evaluation of EARS has been performed with respect to the root mean square error (RMSE), based on the 10-year (2008–2017) observational data. Compared to the global reanalysis data of ERA-Interim, the regional reanalysis data of EARS are closer to the observations in terms of RMSE in both surface and upper-level fields. The present study provides evidence for substantial improvements seen in EARS compared to the ERA-Interim reanalysis fields over East Asia. The study also demonstrates the potential use of the EARS data for applications over East Asia and proposes further plans to provide the latest reanalysis in real-time operation mode. Simple data and updated information are available on Zenodo at 10.5281/zenodo.7404918 (Yin et al., 2022), and the full datasets are publicly accessible on the Data-as-a-Service platform of the China Meteorological Administration (CMA) at http://data.cma.cn (last access: 19 May 2023). [ABSTRACT FROM AUTHOR]

• Diverse Cambrian metavolcanic rocks were reported in the NE Pamir. • The orogenesis in the NE Pamir occurred during the early Jurassic. • Building of the Cambrian accretionary complex at the NE Pamir. • Tectonic evolution from Proto-Tethys to Paleo-Tethys in the NE Pamir. The Pamir Plateau contains critical information on the tectonic evolution from the Proto- to Paleo-Tethys. In this contribution, we report geochronology, geochemistry and Sr-Nd isotopic compositions of diverse metavolcanic rocks in the Bulunkuole Group (BG) in the NE Pamir, to construct the architecture of the thick Cambrian volcanic-sedimentary sequence in the NE Pamir and to provide new insights into the tectonic evolution from Proto-Tethys to Paleo-Tethys. Our newly obtained zircon U-Pb ages combined with ages from literature reveal that these volcanic-sedimentary sequences were deposited during the Cambrian and metamorphosed during the Early Jurassic. The bimodal volcanic rocks (ca. 530 Ma) at the lowest BG show typical arc-like geochemical features, representing the initial arc produced by the southward subduction of the Proto-Tethys Ocean. Amphibolites (ca. 526 Ma) from the Maeryang area show an OIB-like affinity with high Nb/La ratios (0.75–1.01) and positive ε Nd (t) values (4.19–4.76), representing a seamount component in the Proto-Tethys Ocean. High-pressure mafic granulites to the north of Tashkorgan County exhibit E-MORB geochemical features. Combined with recent advances in the NE Pamir geology, we suggest that the southward subduction of the Proto-Tethys slab under the Mazar-Tianshuihai terrane initiated earlier than 530 Ma. Subsequent trench retreat led to the formation of the massive early Paleozoic accretionary wedge (BG) followed by the northward migration of arc magmatism to the BG. The Proto-Tethys Ocean at Pamir did not close in the early Paleozoic. Instead, it was finally closed during the early Mesozoic as revealed by the Early Jurassic amphibolite-facies metamorphism in the BG. [ABSTRACT FROM AUTHOR]

Liver fibrosis is a chronic liver disease with the presence of progressive wound healing response caused by liver injury. Currently, there are no approved therapies for liver fibrosis. Exosomes derived from human adipose mesenchymal stem cells (hADMSCs-Exo) have displayed a prominent therapeutic effect on liver diseases. However, few studies have evaluated therapeutic effect of hADMSCs-Exo in liver fibrosis and cirrhosis, and its precise mechanisms of action remain unclear. Herein, we investigated anti-fibrotic efficacy of hADMSCs-Exo in vitro and in vivo, and identified important metabolic changes and the detailed mechanism through transcriptomic and metabolomic profiling. We found hADMSCs-Exo could inhibit the proliferation of activated hepatic stellate cells through aggravating apoptosis and arresting G1 phase, effectively inhibiting the expression of profibrogenic proteins and epithelial-to-mesenchymal transition (EMT) in vitro. Moreover, it could significantly block collagen deposition and EMT process, improve liver function and reduce liver inflammation in liver cirrhosis mice model. The omics analysis revealed that the key mechanism of hADMSCs-Exo anti-hepatic fibrosis was the inhibition of PI3K/AKT/mTOR signaling pathway and affecting the changes of metabolites in lipid metabolism, and mainly regulating choline metabolism. CHPT1 activated by hADMSCs-Exo facilitated formation and maintenance of vesicular membranes. Thus, our study indicates that hADMSCs-Exo can attenuate hepatic stellate cell activation and suppress the progression of liver fibrosis, which holds the significant potential of hADMSCs-Exo for use as extracellular nanovesicles-based therapeutics in the treatment of liver fibrosis and possibly other intractable chronic liver diseases. [ABSTRACT FROM AUTHOR]

Hepatocellular carcinoma (LIHC) accounts for 90% of all liver cancers and is a serious health concern worldwide. Long noncoding RNAs (lncRNAs) have been observed to sponge microRNAs (miRNAs) and participate in the biological processes of LIHC. This study aimed to evaluate the role of the ST8SIA6-AS1-miR-142-3p-HMGA1 axis in regulating LIHC progression. RT-qPCR and western blotting were performed to determine the levels of ST8SIA6-AS1, miR-142-3p, and HMGA1 in LIHC. The relationship between ST8SIA6-AS1, miR-142-3p, and HMGA1 was assessed using luciferase assay. The role of the ST8SIA6-AS1-miR-142-3p-HMGA1 axis was evaluated in vitro using LIHC cells. Expression of ST8SIA6-AS1 and HMGA1 was significantly upregulated, whereas that of miR-142-3p was markedly lowered in LIHC specimens and cells. ST8SIA6-AS1 accelerated cell growth, invasion, and migration and suppressed apoptosis in LIHC. Notably, ST8SIA6-AS1 inhibited HMGA1 expression by sponging miR-142-3p in LIHC cells. In conclusion, sponging of miR-142-3p by ST8SIA6-AS1 accelerated the growth of cells while preventing cell apoptosis in LIHC cells, and the inhibitory effect of miR-142-3p was abrogated by elevating HMGA1 expression. The ST8SIA6-AS1-miR-142-3p-HMGA1 axis represents a potential target for the treatment of patients with LIHC. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study is to explore how pedicle screws (PSs) and cortical bone trajectory (CBT) screws differ in fixation strength when implanted in L1–L5 with osteoporosis, providing support for choosing implants and trajectories in spine internal fixation surgeries. Methods: We filtered 30 lumbar segments out from CT images of eight osteoporotic participants and simulated PS or CBT screw implantation in each segment, generating 60 vertebra-screw assembly FE models. To evaluate the fixation effect, we performed a pull-out force test simulation in each model and analyzed the maximal pull-out force, pull-out stiffness, and equivalent stress of vertebrae and screws. Results: The maximal pull-out force of PS and CBT screws in L1–L5 was in the range of 905–1552 (N) and 587–1012 (N), while the pull-out stiffness was in the range of 1990–2617 (N/mm) and 1007–1681 (N/mm). The fixation strength of PS in L4 and L5 was higher (p < 0. 0 5), while in L1–L3 PS and CBT screws are similar (p > 0. 0 5). The maximal stress of vertebrae and screws when PS was pulled at 0.25 mm was larger than that of CBT screws. Conclusions: For patients with moderate osteoporosis, it is recommended to insert PS into L4 and L5 to attain better fixation strength, but vertebrae are more prone to fracture. Consequently, under severe osteoporosis, the implantation of CBT screws should be considered first. Bone cement injection may be necessary to consolidate the screw-vertebrae interface with osteoporosis. [ABSTRACT FROM AUTHOR]

The Pamir Plateau contains critical information on the tectonic evolution of the Tethys domain. In this study, we report geochronology, geochemistry, and Sr-Nd-Hf isotopic compositions of the Cenozoic adakitic monzogranite in the Reskam and Taxkorgan areas, NE Pamir, to provide new insights into the post-collisional tectonic evolution following the India-Eurasian collision. Zircon U Pb ages reveal these granitoids were emplaced at ca 12–8 Ma. Geochemically, they exhibit relatively uniform whole-rock major and trace element compositions, and share typical adakitic signatures with high SiO 2 (68.55–73.30 wt%), moderate Al 2 O 3 (14.11–15.84 wt%), elevated Sr (399–1710 ppm) and La (34–182 ppm), but low Y (5.53–15.10 ppm) and Yb (0.39–1.26 ppm), and thus in high Sr/Y (32−200) and (La/Yb) N ratios (20–236). Isotopically, these adakitic rocks show significantly enriched whole-rock Sr Nd (ε Nd (t) = −7.97 to −5.76; 87Sr/86Sr(t) = 0.7072–0.7110) and zircon Hf (mostly ε Hf (t) -5 to −2) isotopic compositions. Elemental and isotope signatures indicate their origin from partial melting of mafic-intermediate sources under high pressure, with a residuum of negligible feldspar but dominant garnet. Integrating the new findings with reported data of granitoids in the Pamir, we estimate the crustal thickness variations from the Cretaceous to Miocene. The crustal thickness in the Pamir region largely remained no more than 45 km before India-Asia collision, after which a significant increase in crustal thickness occurred, reaching a peak of 80–100 km around 10 Ma. We propose that the break-off of the subducted Neo-Tethys oceanic slab (ca. 40 Ma) and lithospheric delamination (ca. 25 Ma) led to two-stage rapid continental uplift events in Pamir Syntax. • Miocene adakitic monzogranites are identified in the NE Pamir. • The adakitic rocks are generated by melting of thickened lower crust. • Crust thickness variation in Pamir Syntax during 120–10 Ma is estimated. [ABSTRACT FROM AUTHOR]

Abstract: The Nuomin volcanic field (NM for short) in northern Greater Xing'An Mountains is dominated by Quaternary monogenetic eruptions, forming lava flows covering an area of about 600km2. The lavas range from tephrite and basanite to trachybasalts, with high K2O contents between 2.6wt.% and 4.3wt.%, and K2O/Na2O between 0.78 and 1.08. These NM lavas are generally magnesian (Mg# between 0.59 and 0.78) and may contain useful information on the origin of potassic magmas in NE China. The NM lavas are characterized by relatively high (La/Yb)N (21.6–41.9) and enrichments in large ion lithophile elements (LILEs), but low in high field strength element (HSFE) concentrations. The NM lavas have negative εΝd(−0.8–−3.0), 87Sr/86Sr between 0.704661 and 0.704880, 206Pb/204Pb between 17.0 and 17.2, 207Pb/204Pb between 15.41 and 15.43, and 208Pb/204Pb between 37.0 and 37.3. Their trace element spider diagram and chondrite-normalized rare earth element (REE) diagram are similar to those of Wudalianchi lavas, but are different from the Halaha–Chaoer river lavas in central Greater Xing'An Mountains. Their REE characteristics indicate that the NM lavas originate from garnet stability field. Based on petrological and geochemical data, we propose that the delamination of K-rich lithosphere mantle trigger the Quaternary potassic volcanism in Northeastern China. [Copyright &y& Elsevier]

The early Paleozoic orogen in South China Block is an intracontinental orogen, and synchronous magmatism (440–390Ma) is mainly acidic with minor intermediate-mafic magmatism. Previous studies suggest that most of the early Paleozoic granites in South China belong to peraluminous S-type genesis while amphibole-bearing I-type granites are subordinate. However, our results indicate that considerable amounts of these early Paleozoic granites have characteristics of both S- and I-type granites. Thus, we propose to divide these granites into two groups: fewer of them are Group A with relatively high ε Hf(t) values (clustering within −3.0 to +9.0) and ε Nd(t) values (−5.2 to +1.3) as well as higher initial temperatures at 810–850°C, and most of them are Group B with relatively low ε Hf(t) values (clustering within −16.0 to −1.0) and ε Nd(t) values (−13.2 to −4.1) as well as relatively low initial temperatures at 700–830°C. The Xiawan monzogranite and Duntou granodiorite are typical Group A granitoids and yield zircon U–Pb ages of ca. 410Ma. These two granites are characterized by high SiO2 (between 67.59 and 74.87wt.%), metaluminous to peraluminous (A/CNK=0.96–1.48) compositions, and a negative correlation between P2O5 and SiO2. Their biotites belong to magnesium biotites, indicating that they have partial features of either I- or S-type granites. Duntou granodiorites exhibit higher ε Hf(t) values (clustering within +1 to +8) and ε Nd(t) values (−3.0 to +1.1) while Xiawan monzogranites show relatively low ε Hf(t) values (clustering within −1 to +5) and ε Nd(t) values (−5.0 to −3.7). Group B granitoids are represented by the Miao'ershan–Yuechengling batholith, which are characterized by high SiO2 (between 64.57 and 77.37wt.%), metaluminous compositions (A/CNK=0.90–1.24), and a negative correlation between P2O5 and SiO2. Yuechengling porphyritic amphibole-bearing biotite granites in this batholith contain abundant amphibole, indicating that they are I-type granites. Miao'ershan–Yuechengling batholith also exhibits relatively low ε Hf(t) values (−12.7 to −1.8) and ε Nd(t) values (−8.9 to −6.7). Geochemical and isotopic analyses on early Paleozoic granites, mafic enclaves and mafic to intermediate rocks demonstrate that the Group A granitoids including Xiawan and Duntou granites may be generated by AFC processes with interactions between asthenosphere-derived magma and metasedimentary rocks, and the Group B granitoids may be formed by AFC processes with interactions between synchronous basaltic magma and metamorphic basement. The post-collisional delamination and asthenospheric upwelling directly participate in the generation of Group A granitoids but indirectly induce the formation of Group B granitoids. [ABSTRACT FROM AUTHOR]

This paper presents the first 40Ar/39Ar age data, new bulk-rock major-trace element compositions and Nd Sr isotope geochemistry, combined with detailed geological mapping of Galatia Volcanic Province (GVP) in the northwest Central Anatolia (Turkey). Here, there are voluminous extrusive rocks in a wide compositional range: a basalt, andesite and trachyte suite, and their pyroclastic equivalents. 40Ar/39Ar dating of two whole-rock samples from the GVP yielded plateau ages of 21.76 ± 0.8 Ma and 20.97 ± 0.5 Ma, constrain the volcanic activity at ca. 21 Ma (Aquitanian). The samples show by sub-parallel light rare earth element (LREE)-enrichment and relatively flat heavy rare earth element (HREE) patterns and moderate fractionation [average (La/Yb) N = 13.5]. Their initial 87/86Sr values vary between 0.704619 and 0.704998, while initial 143/144Nd values lie between 0.512673 and 0.512755. Integration of the geochemical and geochronological with geological data we propose that the volcanic rocks in the northern area of GVP with calc-alkaline affinity were produced by a lithospheric mantle magma in an extensional setting. • The volcanics erupted the earliest Miocene (Aquitanian). • The volcanism took place in an active continental arc. • FC and minor crustal contamination played role in their evolution. [ABSTRACT FROM AUTHOR]

Abstract: The Late Cretaceous bimodal Yunshan (Yongtai) volcanics in Fujian province contain peralkaline rhyolites, the only presence of such rhyolites in southeastern China. Whole-rock and mineral chemical compositions are analyzed for the coexisting aluminous (metaluminous to weakly peraluminous)-peralkaline high-silica rhyolites from the Yunshan volcanics. They are sparsely porphyritic, and contain K-feldspar, ferromagnesian minerals, quartz, magnetite, and titanomagnetite phenocrysts, as well as accessory minerals such as fayalite, chevkinite, apatite and zircon. The mineral assemblage indicates an oxidizing pre-eruption condition. These rhyolites exhibit diagnostic geochemical features of A-type granites, such as elevated 104 *Ga/Al (mostly greater than 2.6) and FeOT/(FeOT +MgO) ratios, enrichment in high field strength elements (HFSE) such as Zr (>400ppm) and Nb, and strong depletion in Al2O3 (<13wt%), CaO, Ba and Sr. On the basis of their petrographic and geochemical characteristics, it is suggested that the rhyolite magmas are derived from partial melting of H2O-poor (meta) granitic igneous rocks in the deep crust, and cannot be fractionated from the coeval Yunshan mafic magmas. Geochemical variations of major and trace elements indicate the possible fractionation of K-feldspar, calcium-rich pyroxene, Fe–Ti oxides and minor chevkinite during the magma evolution. In peralkaline rhyolites, we found that the pre-existing Fe–Ti oxide and hedenbergite phenocrysts had been transformed into aegirine+oxide and aegirine+oxide+fluorite assemblages, respectively. These mineral assemblages are the products of the subsolidus reaction of pre-existing phenocrysts and extraneous Na–F-rich fluids. Such Na–F-rich fluids may be derived from the degassing of the subvolcanic rocks. The reactions indicate that the Yunshan peralkaline rhyolites could be generated through the reaction of highly fractionated aluminous silica magmas and Na–F-rich fluids. [Copyright &y& Elsevier]

Abstract: Zircon U–Pb and Hf isotope compositions have been systematically measured to constrain the timing and petrogenesis of the Late Mesozoic volcanic sequences in southeastern Zhejiang, SE China. The Early Yanshanian (Jurassic) volcanism took place at 177Ma and formed scattered volcanic rocks in the region. In contrast, the large-scale Late Yanshanian (Cretaceous) volcanism, with multiple eruptive stages between 140 and 88Ma, formed the widespread lower and upper volcanic series. Two volcanic hiatuses were clearly identified at 120–110Ma between the lower and upper volcanic series and at 128–122Ma between the two subdivided cycles within the lower series. In addition, the magnitude of the two volcanic cycles in the lower series is significantly different. The cycle I of the lower series (140–128Ma) occurred in the largest scale, which is much larger than the cycle II (122–120Ma) as well as the whole upper series (110–88Ma). Petrogenetically, the widespread Late Mesozoic volcanic rocks were mainly derived from the partial melting of the Paleoproterozoic crustal basement materials, with obvious addition of juvenile materials after 122Ma. The analyzed zircons of the Early Yanshanian volcanic rocks show crustal model ages (T DM2) mainly of 2.00–2.16Ga, and weighted mean ε Hf(t) value of −13.4. The ε Hf(t) and T DM2 values are ca. −10 and 1.67–2.00Ga for zircons from the cycle I volcanic rocks, −11.4 to −1.4 and 1.27–1.90Ga for those from the cycle II volcanic rocks, −9.3 to −2.7 and 1.33–1.78Ga for those from the acidic rocks of the upper series, respectively. The characteristics of the Late Mesozoic volcanic sequences indicate the varying influence of the subduction of the paleo-Pacific plate. Our study supports that the subduction style changed from low-angle to intermediate-angle forward subduction at the first hiatus of 128–122Ma and then dramatically changed to rapid high-angle rollback subduction at the second hiatus of 120–110Ma. [Copyright &y& Elsevier]

Abstract: The Neoproterozoic Quruqtagh Group in the Tarim Block, NW China, contains multiple diamictites in the Bayisi, Altungol, Tereeken, and Hankalchough formations. These diamictites may represent three or possibly four discrete glaciations, although evidence for a glacial origin of the Bayisi and Altungol diamictite is ambiguous. To constrain their age and duration, we dated three volcanic beds (V1, V2, and V3) in the Quruqtagh Group using the SHRIMP (sensitive high-resolution ion microprobe) zircon U–Pb method. Volcanic bed V1 near the base of the Bayisi diamictite yields a 740±7Ma age, volcanic bed V2 near the top of the Bayisi Formation gives a 725±10Ma age, and volcanic bed V3 between the Tereeken and Hankalchough diamictites yields a 615±6Ma age. V1 and V2 have overlapping ages, and together these dates suggest that the Bayisi diamictite was deposited at around 730Ma. The Tereeken and Altungol diamictites were deposited between 725±10Ma and 615±6Ma, and the Hankalchough diamictite between 615±6Ma and ∼542Ma (i.e., the Neoproterozoic–Cambrian transition). These dates and previously published chemostratigraphic data are consistent with (but doe not require) the correlation of the Tereeken and Hankalchough diamictites with the 635Ma Nantuo and 582Ma Gaskiers glaciations, respectively. However, the new dates are inconsistent with a single and globally synchronous Sturtian glaciation that occurred in the pre-Nantuo Neoproterozoic Era. Instead, currently available data necessitate that either multiple glaciations occurred, or a globally diachronous glacial event developed during a protracted period between ∼750Ma and ∼650Ma. [Copyright &y& Elsevier]

Abstract: Integrated geochemical and Sr–Nd–Pb isotopic studies of the Early Jurassic Nandaling flood basalts (NFB) in the Yanshan belt, northern margin of the North China Craton (NCC), are presented in this paper. These sub-alkaline basalts evolved from a more magnesium-rich parental magma through fractional crystallization of olivine and clinopyroxene. The primitive magma of the NFB originated from 2–5% partial melting of spinel to garnet transitional peridotite at about 70–80 km depth in the Mesozoic lithosphere mantle. The NFB contain a distinctive lithospheric component, characterized by Nb (Ta), Th, U and Ti depletions, LREE enrichments, moderate Sr, and low Nd and Pb initial isotopic ratios, as a result of an interaction between lower crust (15–25%) and primitive magma evoked by magmatic underplating at crust–mantle boundary. The Early Jurassic NFB extruded in an intraplate extensional setting related to post-orogenic collapse in the northern margin of the NCC, indicating an event of lithospheric modification earlier than that in the southern margin (Early Cretaceous). The temporal similarity of the Jurassic–Cretaceous mantle-derived mafic rocks to lower crust replacement, and the decoupling of surface shortening with lithospheric thinning during the Late Jurassic–Early Cretaceous, suggest the important role of magmatic underplating and subsequent crust–mantle interaction accompanied by asthenosphere upwelling on the evolution of the Mesozoic lithosphere of the NCC. The correlation between lithospheric thinning and magmatic underplating may be an important process in continental rifting. [Copyright &y& Elsevier]

• Anomalously low 87Sr/86Sr values in Ediacaran carbonates. • Positive εNd(t) values in the Ediacaran carbonates. • Profound overprints by juvenile hydrothermal fluids. Secular variation of 87Sr/86Sr in carbonate strata has been widely used in regional and global chemostratigraphic correlations. Typically, diagenesis results in higher 87Sr/86Sr signals relative to their primary composition due to the alteration by Rb-rich fluids and radiogenic decay of 87Rb to 87Sr. Surprisingly, 87Sr/86Sr values in the Ediacaran limestones from Saudi Arabia (from 0.7029 to 0.7059) are significantly lower than typical Ediacaran seawater values (mostly from 0.7080 to 0.7090) based on a global compilation. Understanding the origin of these anomalies is important insofar as early macrofossils are preserved in these strata. Two hypotheses have been independently evaluated in this study. The first hypothesis shows a low temperature scenario with isolated oceans or lakes in proximity to a mafic source. The second hypothesis is characterized by a high temperature scenario with profound overprints by juvenile hydrothermal fluids. Integrated Sr and Nd isotope data reveal that the 87Sr/86Sr anomalies are closely coupled with positive εNd(t = 560 Ma) values (up to +4.1). Clear covariations between 87Sr/86Sr, εNd, TOC, δ13C carb , δ13C org , and δ18O carb were found. Based on multiple lines of petrographic, field, and geochemical evidence, the second hypothesis (i.e., hydrothermal alteration by juvenile fluids) is preferred in this study. Thermogenic breakdown of organic matter in host sediments may have caused the increasingly low TOC abundance and high δ13C org signals of the residual organic matter. We argue that the concept that the Ediacaran biotic radiation took place in an isolated lake environment should be treated with caution. These remarkably low 87Sr/86Sr signals have neither temporal nor biogeochemical significance. Sr isotope chemostratigraphy in this particular region may not be a reliable tool for stratigraphic correlations. [ABSTRACT FROM AUTHOR]

Neoproterozoic layered mafic intrusions occur along the northern margin of the Yangtze Block in South China. In this paper, we report the chemical compositions of clinopyroxene, plagioclase, and olivine from two major mafic intrusions at Bijigou (BJG) and Wangjiangshan (WJS), to constrain the parental magma characteristics and geodynamic setting. The olivine and plagioclase compositions indicate that the parental magma for BJG and WJS was an evolved tholeiitic magma with high FeO T /MgO ratios. An origin of arc magmatism is not supported by the following mineralogical and petrological observations: (1) the strong rift-affinity indicated by olivine, plagioclase and clinopyroxene geochemistry, (2) the absence of high anorthite in the cumulate rocks, (3) the paucity of abundant cumulus hornblende crystals, and (4) the lack of voluminous intermediate rocks in the rock associations. We propose that the BJG and WJS mafic-ultramafic intrusions formed under a rift extensional setting during 820–780 Ma. The subduction process ceased before 820 Ma and did not directly contribute to the generation of the BJG and WJS mafic-ultramafic intrusions. The arc-like Nb Ta depleted trace element pattern in the parental magma is inherited from the mantle metasomatized by earlier subduction processes. • The parental magma was evolved tholeiitic magma with an arc-like Nb-depleted nature. • Mineral chemistry and petrology suggest a rift extensional setting during 820–780 Ma. • The arc nature in the parental magma is inherited from earlier subduction processes. • The tectonic regime had changed from compression to extension prior to 820 Ma. [ABSTRACT FROM AUTHOR]