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The Xiazha Formation recently identified in the Yarlung-Zangbo suture zone of southern Tibet has been considered as crucial evidence for early (pre-Cretaceous) subduction of Neo-Tethyan oceanic lithosphere. In this study, we carried out an integrated stratigraphic, petrographic, and geochemical study of the Xiazha Formation, which consists of abyssal chert, siliceous mudrocks, and calcareous turbidites deposited onto basaltic basement. Basalt geochemistry indicates alkali to tholeiitic magmas generated in a within-plate oceanic setting. The siliciclastic fraction contained in calcareous turbidites consists of plagioclase and mafic-rock fragments derived from the underlying basalts, and includes Cr-spinel grains with relatively high TiO 2 and moderate Al 2 O 3 concentrations pointing to an OIB source. Based on these data, and virtual lack of detritus of continental origin, we infer that the Xiazha Formation was deposited in oceanic island/plateau within the Neo-Tethyan domain. Its stratigraphy records an evolution from basaltic eruptions to the development of a carbonate platform surrounding the basaltic island, and finally to drowning of the atoll. The Xiazha Formation was not deposited in a subduction-related basin and, therefore, cannot be used as evidence for pre-Cretaceous initiation of the Yarlung subduction zone. • Earliest Cretaceous oceanic island developed in the Neo-Tethys Ocean. • The Xiazha Formation in the Yarlung suture shows intact stratigraphic continuity. • It was deposited on an oceanic island rather than in a subduction setting. • The Xiazha Formation records the evolution of the oceanic island through time. • The Xiazha Formation cannot be used as evidence for pre-130 Ma subduction. [ABSTRACT FROM AUTHOR]

• Explored the variation law of fracture gas-steam pressure with heat flow. • The stress intensity factors under the action of fracture gas-steam pressure and heat flow stress is established. • The influence of heat flow incidence angle and heat flow density on crack initiation is analyzed. • Provided certain theoretical guidance for engineering fractures with geothermal flow. The construction of tunnel projects in the Sichuan-Tibet region has led to the occurrence of rock fractures caused by high temperature and high humidity, which are inevitable challenges. When there is fracture water in rock fractures and it encounters a heat flow, the water vaporizes into fracture steam, which undergoes thermal expansion to generate fracture gas-steam pressure. The heat flow direction is at an angle to the crack, causing heat flow stress in the rock. To understand the mechanism of crack initiation and propagation in rocks under the joint action of uniform heat flow-induced fracture gas-steam pressure and heat flow stress, the control equation for fracture gas-steam pressure is derived and expressions for stress intensity factor, crack temperature field, stress field, and crack initiation strength criterion are established based on the theory of complex variable functions. The key parameters are analyzed and discussed, finding that under low heat flux density, small incidence angles, and large crack inclination angles, K I values are higher, and the crack initiation is mainly in tension. Under high heat flow density, large incidence angles, and crack inclination angles near 45°, K II values are higher, and the crack initiation is mainly in shear. The coupling effect of K I and K II is more sensitive to heat flow density and inclination angle. The critical initiation angle and initiation strength increase with the increase of heat flow density and incidence angle, with heat flow density being the determining factor. [ABSTRACT FROM AUTHOR]

• Based on the modified MTS criterion, the rock crack initiation criterion under the combined action of thermal stress and fracture air-vapor pressure is established by the superposition method. • The expansion pressure of the fracture gas in the crack is controlled by the temperature and the gas saturation, and the temperature is the dominant effect. • K I , K II are controlled by thermal stress and fracture gas-vapor pressure, in which thermal stress is the dominant factor. • With the increase of temperature, the crack initiation form tends to be tensioned from shearing, and the gas expansion pressure promotes the tensioned part. Near the surface of the Sichuan-Tibet line tunnel surrounding rock under construction is in a sub-hot and humid environment, and long-term accumulation will produce damp-heat diseases. The significant temperature difference leads to the thermal stress of the surrounding rock, and the surrounding rock fracture water vaporizes to create fracture air-vapor pressure, which induces crack initiation. The state equation of gases, thermoelastic mechanics, and the theory of linear elastic fracture mechanics are used to study the crack initiation law of rock under the joint action of sub-elevated temperature stress and fracture air-vapor pressure. The stress intensity factor's expression under the two joint actions is derived from the superposition principle. Then the initiation criterion considering both internal influencing factors (rock properties, crack geometry parameters (inclination angle)) and external influencing factors (far-field stress, temperature, humidity factors) is derived. The theory is used to quantitatively analyze the distribution law of tangential stress at the crack tip and the crack initiation form. The effects of each parameter on critical crack initiation angle and crack initiation strength are discussed. The theoretical results are further verified by numerical simulation. The results show that in the sub-elevated temperature range, the thermal stress and the fracture air-vapor pressure jointly affect the crack initiation law, and thermal stress is the dominant factor. With the temperature increase, K I > K II , the critical crack initiation angle increases gradually, the crack initiation form changes from shear to compression-shear, and finally tends to tension. The fracture air-vapor pressure promotes the tension part. The maximum tangential stress increases linearly with temperature. The maximum tangential stress and critical crack initiation angle increase first and then decrease with the rise of crack inclination angle and reach the maximum at 45°. The research results supply a theoretical basis for preventing and treating the rock crack propagation surrounding the tunnel under sub-elevated temperatures and high humidity. [ABSTRACT FROM AUTHOR]

Podocarpium is an extinct genus in Fabaceae with rich fossil records in Eurasia dating back to the Eocene. However, the diversification and biogeographic histories of Podocarpium are poorly known due to a lack of fossils in some key regions, such as the Tibetan Plateau, an area recently shown to be crucial for floristic exchanges worldwide in the geological past. Here, we describe well-preserved fossil pods of Podocarpium from the late Eocene (~ 35 Ma) of the Lunpola Basin, central Tibetan Plateau, China. Together with detailed morphological observation and geometric morphology analysis, these fossil pods are named Podocarpium tibeticum W.-C. Li, J. Huang et T. Su sp. nov., characterized by asymmetrical elliptical valves, olecranon fruit beak, and a clearly oblique base. This material comprises the oldest fossil record of Podocarpium from the Tibetan Plateau and adjacent regions. The discovery of P. tibeticum shows Podocarpium was present in central Tibet by the late Eocene. Together with previous fossil records, it indicates that Podocarpium may have originated in East Asia, migrated into the central valley of Tibet in the late Eocene, and then spread westward to Europe through a low-latitude path of island chains along the Neotethys. Results of paleoecological niche modeling demonstrate that Podocarpium had an almost worldwide potential distribution range in the Eocene, but this sharply contracted thereafter until by the Pliocene it was restricted to a small area of East Asia. Generally, this finding further supports the idea that what is now the central Tibetan Plateau was a globally significant hub for Paleogene floristic exchange. • First report of Podocarpium in central Tibetan Plateau. • Shows a new fossil pod species of Podocarpium. • Enhances understanding of its historic distribution globally. • Podocarpium is sensitive for dry and cool climates. [ABSTRACT FROM AUTHOR]

• The back-arc and arc-type magmatisms (ca. 838–748 Ma) were newly identified in the Rutong and Shiquanhe region, west of Tibet. • The North Lhasa terrane may separat from the Indian continent, finally constituted the northern segment of the East African Orogen during the Neoproterozoic. • The BNSZ retains geological records of the evolution of the Mozambique Ocean in the Neoproterozoic. Due to limited exposure of the Precambrian rocks in the Tibetan Plateau, their affinities and evolutions are inadequately studied. Here we report the newly identified Neoproterozoic metabasites (including metagabbros and metadolerites) at the western end of the Bangong-Nujiang suture zone (BNSZ) and the west part of the North Lhasa terrane. The Rutong Dong (RTD) metagabbros and Shiquanhe Nan (SQN) metadolerites yield zircon U-Pb ages of 838 Ma and 748 Ma, respectively. The RTD metagabbros are tholeiitic and exhibit both MORB- and arc-like geochemical characteristics, and we consider these to have formed in a back-arc basin setting. Combined with positive zircon ε Hf (t) (+6.3 to +13.8) and whole-rock ε Nd (t) (+4.4 to +5.3) values, the geochemical features of the RTD metagabbros indicate that they originated from a depleted mantle source enriched by subduction-related components (e.g., Th and U). The SQN metadolerites are mainly of transitional character (between tholeiitic and calc-alkaline), as well as representing typical calc-alkaline basalts. Their arc-like geochemical characteristics, as well as low positive whole-rock ε Nd (t) (+1.7 to +3.4), and positive zircon ε Hf (t) (+4.3 to +5.9) values, indicate generation by partial melting of an enriched subduction components modified mantle in an arc-type setting. Based on previous research, we propose that the North Lhasa terrane likely separated from India at ca. 925–860 Ma by the opening of the Mozambique Ocean. As the subduction zones were active at ca. 838–730 Ma in this ocean, a series of subduction-related magmatic events occurred, that is recorded in this study of the Rutong-Shiquanhe region, and other parts of the BNSZ and North Lhasa terrane. Consequently, we suggest that the BNSZ not only preserves information of the Meso-Tethys but also retains geological records of the Neoproterozoic Mozambique Ocean. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Shiquanhe-Yarlun Zangbo geothermal field enriched in rare alkali metal resources. • Himalayan leucogranite are typical of S-type granites. • Partial melting of metasediments and intense water–rock interaction promote RAMs enrichment. • Strong adsorption controls the hyper enrichment of rare metals during silica precipitation. Geothermal waters in the Shiquanhe-Yarlun Zangbo geothermal field of southern Tibet are highly enriched in rare alkali metals (RAMs), which form a globally unique geyserite Cs-deposit. Boron isotopes, together with the geochemistry of a local leucogranite, geothermal springs and geyserite were investigated to constrain the migration and accumulation of RAMs in the geyserite cesium deposit. The δ11B values of −9.7‰ to −8.4‰ in tourmalines from the Himalayan leucogranite have shown typical S-type granites. A mass balance calculation indicates that the magma of the S-type granite contained < 10 % dehydrated fluid, which resulted in an enrichment of RAMs by 4–5 times during the partial melting of crustal materials, compared to that in the UCC. The linear relationships of ΣRAMs vs. B and Na + K vs. soluble Si, indicate that further enrichment of RAMs in the geothermal fluids was promoted by intense water–rock interaction at temperatures of 210 to 250 °C in the geothermal system reservoir. A strong adsorption process controlled the hyper enrichment of RAMs (especially Cs) during silica precipitation from the upwelling geothermal water, with the sharp decreases in temperature and pressure leading to the enrichment of Cs in fresh geyserites. Despite loss of RAMs during dehydration of the geyserite during phase transformation from opal-A, opal-CT, and chalcedony to quartz, freshly deposited geyserites have great potential for exploration of RAMs resources in this area. [ABSTRACT FROM AUTHOR]

In this study, three strains of lactic acid bacteria isolated from Tibetan kefir grains, including two strains of Lactobacillus pentosus LZ-R-17 and L. helveticus LZ-R-5, and one strain of Lactococcus lactis subsp. lactis LZ-R-12. The ability of three strains to produce exopolysaccharide (EPS) was tested, and L. pentosus LZ-R-17 was found to have the highest EPS yield. One EPS (R-17-EPS) was isolated from the fermented milk by L. pentosus LZ-R-17 and purified by DEAE-52 anion exchange chromatography. Furthermore, R-17-EPS preliminary structure and macrophage immunomodulatory activity in vitro were investigated. On the basis of the analytical results of ultraviolet-visible spectrum, Fourier transform-infrared spectrum, monosaccharide composition analysis and one-dimensional and two-dimensional nuclear magnetic resonance (NMR) spectra, R-17-EPS was found to have an average molecular weight of 1.20 × 106 Da and was composed of galactose and glucose residues with a molar ratio of 1.00:3.15. NMR analysis revealed that the R-17-EPS was a linear hetero-galactoglucan containing repeating units of →2)-α-D-Gal p -(1 → 4)-β-D-Glc p -(1 → 4)-β-D-Glc p -(1 → 4)-β-D-Glc p -(1→. In addition, R-17-EPS could effectively enhanced the proliferation, phagocytosis, nitric oxide and cytokines production of RAW264.7 cells, suggesting that R-17-EPS had potent immunostimulatory activity and could be explored as immunomodulator in functional food and/or medicine fields. [Display omitted] • Three LAB strains were isolated from Tibet kefir and characterized. • Lactobacillus pentosus LZ-R-17 was the best EPS producer among three LAB strains. • A novel exopolysaccharide (R-17-EPS) was obtained from L. pentosus LZ-R-17. • R-17-EPS was a linear hetero-galactoglucan with average Mw of 1.20 × 106 Da. • R-17-EPS exhibited significant immunomodulatory activity. [ABSTRACT FROM AUTHOR]

We have located a total of 232 local earthquakes using data recorded by the SANDWICH seismic network from November 2013 to October 2014 in central Tibet across the Bangong-Nujiang suture (BNS). The focal depths of all earthquakes are shallower than 30 km and therefore are in the upper crust. The absence of lower crust earthquakes may imply a weak, ductile lower crust in central Tibet. Moreover, these earthquakes are dispersed throughout conjugate strike-slip fault zones, indicating that evenly distributed upper crustal deformation might predominate in central Tibet. This observation agrees with the hypothesis that conjugate fault zones accommodate coeval east-west extension and north-south contraction via continuous deformation. Moreover, the focal mechanisms show that strike-slip and normal faulting are the dominant types of deformation and that the extension in central Tibet is oriented approximately east-west. Despite some anomalies, the kinematics implied by most of the focal mechanisms correlate well with those of the surface structures. [ABSTRACT FROM AUTHOR]

The Jurassic Gangdese arc hosts the giant Xietongmen (Xiongcun) porphyry Cu Au magmatic-hydrothermal centre. In order to understand the tectonomagmatic framework of the arc and its controls on the origin and temporal-spatial distribution of porphyry mineralization we conducted extensive major and trace, and isotopic analysis on a suite of samples collected regionally. Geochemical variations were observed across the Jurassic arc from south to north, controlled by northward subduction of the Neo-Tethyan oceanic plate and overlying Lhasa lithosphere. In the frontal arc (latitude 29°–29.55°N), the magmas had high Ba/La and Ba/Th ratios, high εNd (t) (+ 3 to + 7) values, and their zircons have high εHf (t) (+ 10 to + 18) values, and heterogeneous O isotopic compositions (δ 18 O = + 3.6 to + 6.6‰). The low titanium-in-zircon temperature and zircon saturation temperature (both average = ~ 700 °C) suggest that a greater flux of dehydration fluids from the subducting slab triggered partial melting of the mantle wedge in the southern arc. High zircon Eu/Eu* and Ce/Nd ratios (> 0.4 and > 20, respectively) indicate highly oxidized, fertile magmas, from which the Xietongmen porphyry Cu Au deposit formed. In contrast, the interior arc (north of latitude 29.55°), close to the ancient Tibetan basement, shows low Ba/La and Ba/Th ratios, low εNd(t) (− 0.1 to + 2.5) and zircon εHf (t) (+ 2 to + 12) values, and less heterogeneous zircon O isotopic compositions with higher δ 18 O values. Higher titanium-in-zircon and zircon saturation temperatures (mostly > 750 °C) suggest that less water was involved during the partial melting of mantle wedge in this region. Low zircon Eu/Eu* and Ce/Nd ratios (mostly < 0.4 and < 20, respectively) point towards less oxidized magmatic conditions. We conclude that across-arc geochemical and fluid-flux variations controlled the formation and spatial distribution of Jurassic porphyry deposits in the Gangdese belt. [ABSTRACT FROM AUTHOR]

Abstract: We have conducted a whole-rock geochemical, U–Pb zircon geochronological, and in situ zircon Hf–O isotopic compositional study of rocks in southern Tibet from the Langxian igneous suite (including a lamprophyre dyke, mafic enclaves, a granodiorite, and a two-mica granite) and the Nuri igneous suite (a quartz–diorite). U–Pb zircon dating indicates that the timing of crystallization of the mafic enclaves and host granodiorite of the Langxian suite are ca. 105Ma and 102Ma, respectively, that the Langxian lamprophyre dyke and the two-mica granite were emplaced at ca. 96Ma and 80–76Ma, respectively, and that the Nuri quartz–diorite was emplaced at ca. 95Ma. With the exception of the lamprophyre dyke and mafic enclaves in the Langxian area, felsic rocks from the Langxian and Nuri igneous suites all show signs of a geochemical affinity with adakite-like rocks. The high Mg-numbers, high abundance of compatible elements, high εNd(t) (2.7 and 2.8) and δ18O (8.9 and 9.2‰) values, elevated zircon εHf(t) (11.0–17.0) values, and low 87Sr/86Sr(i) ratios (0.7040), collectively indicate that the Nuri adakite-like quartz–diorite was derived from partial melting of the low temperature altered Neo-Tethyan oceanic crust, and that these dioritic magmas subsequently interacted with peridotite as they rose upwards through the overlying mantle wedge. The observation of identical differentiation trends, similar whole-rock Sr–Nd and zircon Hf isotopic compositions, and consistently low (Dy/Yb)N ratios among the Langxian igneous suite rocks, indicates that the adakite-like granodiorite was produced by low-pressure fractional crystallization of precursor magmas now represented by the (relict) mafic enclaves. However, relatively high Al2O3 contents, low MgO, Cr and Ni contents, and low (La/Yb)N and (Dy/Yb)N values indicate that the two-mica granite was derived from partial melting of the southern Tibetan mafic lower crust in the absence of garnet, while isotopic data suggest that at least 70% of the magma source region was juvenile materials. Combined with the presence of HT (high temperature) charnockitic magmatism, HT granulite facies metamorphism, and large volumes of Late Cretaceous batholiths, the oceanic-slab-derived Nuri adakitic rocks indicate a substantial high heat flux in the Gangdese batholith belt during the Late Cretaceous, which may have been related to subduction of a Neo-Tethyan mid-ocean ridge system. According to this model, hot asthenosphere would rise up through the corresponding slab window, and come into direct contact with both the oceanic slab and the base of the overlying plate. This would cause melting of both the oceanic slab and the overlying plate by the addition of heat that was ultimately linked with peak magmatism and the significant growth and chemical differentiation of juvenile crust in southern Tibet during the Late Cretaceous (105–76Ma). In addition, the petrogenesis of the Langxian adakite-like two-mica granite indicates that the southern Tibetan crust was still of normal thickness prior to the emplacement of these intrusions at ca. 76Ma. This probably means that large parts of southern Tibet were not very highly elevated prior to the Indian–Asian collision. [Copyright &y& Elsevier]

Abstract: Tectonic models for the evolution of the Himalayan orogen interpret the Greater Himalayan crystalline complex (GHC) to be the result of either thick-skinned thrusting involved Indian basement, thin-skinned thrusting involving exotic terranes, middle-crustal ductile flow, or wedge extrusion of the Indian crust during India–Asia collision. Two key pieces of information needed to test the validity of these models is the temporal–spatial distribution of, and the identification of the dynamic mechanisms involved in, regional melting under southern Tibet. Here, we document an Eocene–Oligocene melting event in southern Tibet, which forms a 150-km-long, NW–SE-trending granitoid belt along the Zedong–Lhunze traverse between the Indus–Yarlung suture (IYS) and the south Tibetan detachment (STD). U–Pb dating of magmatic zircons indicates that this granitoid belt youngs northward from ∼46Ma (in Lhunze) to ∼30Ma (in Zedong). 40Ar/39Ar dating of deformed biotite within 42–46Ma granitoids constrains the timing of shearing to ∼39–41Ma. The granitoid belt of southern Tibet is dominated by Eocene two-mica granites in the Tethyan Himalaya, with minor ∼30Ma granodiorites along the IYS and ∼35Ma granites in the Yelaxiangbo dome, where Indian mid-crustal rocks are exposed. The ∼35Ma granites are characterized by variable Na2O/K2O ratios (1.03–4.44), relatively high Sr concentrations, and high Sr/Y (14.0–126.3) and La/Yb (11.1–42.8) ratios, which distinguish these granitoids from Miocene leucogranites in the Himalaya. Comparison of the Sr–Nd isotopic compositions of these granites with mid-crustal amphibolites exposed in the Yelaxiangbo dome suggests that the granites were derived from melting of the amphibolites at ∼880°C and ∼10kbar. The ∼30Ma granodiorites and ∼42–46Ma two-mica granites are Na-rich and peraluminous, and are adakitic. They contain inherited Proterozoic zircons, and have a much wider range in ε Nd(t) of –14.9 to –2.5 and (87Sr/86Sr) i of 0.7062–0.7188, and have a Nd isotopic model age of 1486–1978Ma, indicating that these magmas were derived from a thickened Indian lower crust and were subsequently mixed with amphibolite-derived granite melts or were contaminated by the middle crust under southern Tibet. An apparent northward-younging age trend and shearing of the Eocene–Oligocene granitoids requires the southward migration of slices of middle crustal material, in which the Eocene granitoid magmas were emplaced and stored. Our data, along with structural, metamorphic, and intrusive histories of the Himalaya, lead us to propose a model for crustal anatexis and tectonic evolution of the Himalayan orogen, controlled by a number of large-scale events, such as slab break-off, buoyancy-driven uplift, lateral movement, and subsequent exhumation of slices of the subducted Indian crust during Indo-Asia collision at 55–40Ma. [Copyright &y& Elsevier]

Abstract: Bioenergy is the major domestic energy for rural households in developing countries due to its cheap or easy-getting characteristics. Productive use of bioenergy is an important strategy for rural households to improve not only their income, but also their health, living environment and so on. In Tibet of China, which is rich in cattle dung and firewood as the major energy sources for rural households, the efficiency of energy utilization is just about 10%. In order to improve energy utilization efficiency and the living conditions for rural residents, the Tibet Autonomous Region government introduced residential biogas model (RBM) to local households, which was a comprehensive utilization system of energy integrated with residential biogas digester, vegetable greenhouse and livestock shed. This paper aims to show the productive use of the bioenergy by the RBM, which could be depicted as the feasibility and the benefits on economic, eco-environmental and social aspects of biogas utilization, based on household questionnaires in Panam County. In RBM, biogas digester works as the biomass material supplement loop to transform originally biomass flow from single-direction to recycling-direction. The results indicate that the output of unit biogas digester could replace 1.44t of firewood, 1.65t of agricultural residues and 1.75t of cattle dung, respectively. The net incremental benefit of RBM could reach 5550.72 Yuan in 15 years. The reduced amount of CO2 emission when substituted by biogas in other agricultural areas and the areas of semi-agricultural and semi-husbandry in Tibet could be (76.66–79.89)×104 t/year and the capability for nitrogen storage could achieve (0.39–0.99)×104 t/year. The amount of cattle dung replaced by biogas could reach 78.29×104 t/year; this means that the saved cattle dung, 3.51t/hm2, could be reallocated back to cultivated land to improve the soil fertility and to keep the balance of nutrient elements in cultivated land. Biogas utilization reduces the labor opportunity costs of women compared to use of traditional bioenergy sources. It could be concluded that the productive use of bioenergy through RBM in this area has its capability to release the current pressures on biomass sources by adjusting patterns of rural energy consumption, and to improve the conditions of health, environment, economy and energy conservation. [Copyright &y& Elsevier]

In this study, a yeast-like fungal strain (LG-8), newly isolated from spontaneous Tibet kefir in China, was identified as Geotrichum candidum on the basis of its morphological characteristics and ITS5.8S gene sequence. Interestingly, the strain was able to remove more than 99% of Pb2+ ions in water at low concentrations and a maximum of 325.68 mg lead/g of dry biomass. The results of selective passivation experiments suggested that phosphate, amide and carboxyl groups on the cell wall contributed to lead removal. Scanning electron microscopy (SEM) photomicrographs revealed that large amounts of micro/nanoparticles formed on the cell wall, and energy dispersive X-ray spectroscopy (EDX) results further indicated the presence of lead along with phosphorus and chlorine in the particles. Furthermore, the results of Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses revealed that the particles were composed of pyromorphite [Pb 5 (PO4) 3 Cl], a highly insoluble lead mineral. Importantly, this is the first time that the biomineralization of lead into pyromorphite has been observed as the major mechanism for lead removal by G. candidum LG-8, providing a new strategy to scavenge heavy metals from aquatic environment in an eco-friendly manner. Image 1 • A lead-tolerant Geotrichum strain LG-8 newly isolated from kefir milk was identified. • The strain removed at least 99% of lead from water with low lead levels. • Phosphate, amide and carboxyl groups are involved in lead removal. • Nanoparticles formed on cell wall surface. • Biomineralization of lead into pyromorphite is the major mechanism for lead removal. [ABSTRACT FROM AUTHOR]