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• Classification of complex geothermal systems in the Gonghe Basin. • Geothermal gas and isotope characteristics of the Gonghe Basin. • Deep heat source indication based on fluid geochemistry. The Gonghe Basin is located in the northeast of the Tibetan Plateau and is rich in geothermal resources. In recent years, Hot Dry Rocks have been discovered in the basin, and related studies have suggested that localized melts in the middle and lower crust provide an additional heat source. However, there needs to be more conclusive evidence. In this paper, geothermal water chemistry and gas isotope samples from the Gonghe Basin and its neighboring areas were systematically collected. Comprehensive fluid geochemical analysis was carried out in conjunction with the distribution and nature of the regional fracture to propose the circulation pattern of the complex geothermal system and the source of the gas components in the Gonghe Basin. The results show that the hot water in the Gonghe Basin and its surroundings is recharged by meteoric water and can be classified into three types according to its hydrochemical and isotopic characteristics: deep-fluid type (deeper circulation depth or deeper burial of the geothermal reservoirs), runoff type (shallower circulation depth), and mixed type (shallow layered geothermal reservoirs at the center of the basin), with a gradual decrease in the temperature of the geothermal reservoirs accordingly. N 2 of atmospheric origin dominates the hot water gas. Except for the relatively high CO 2 concentration (7.44%) in the deep geothermal reservoir in the center of the basin, most of the samples contain low CO 2 concentration, which is mainly derived from decarbonization of carbonate rocks and sediments, and the contribution of mantle carbon release is almost zero; some of the hot water is detected with a slightly higher content of CH 4 , which is inferred to be of organic origin. The distribution of deep fractures provides a channel for the uplift of deep mantle-sourced volatiles, which makes some hot springs and geothermal wells show some mantle-sourced diagenesis of He, which provides some corroboration for the existence of partial melts in the crust. This understanding is significant for deepening the understanding of geothermal genesis in the northeast Tibetan Plateau and guiding future geothermal exploration in the region. [ABSTRACT FROM AUTHOR]

The Yarlung Tsangpo is the largest river draining the southern Tibetan Plateau along the Himalayan ranges. In this paper, the ions and elements in the water of the Yarlung Tsangpo were studied. In general, the water of the Yarlung Tsangpo had a fairly high buffering capacity (pH ~8.8) and oxidation environment (ORP ~190 mv). Total dissolved solids averaged approximately 157 mg L, which is higher than that of the global mean level. Under the dominant rock weathering due to the abundant carbonates around the river basin, the ionic chemistry of the Yarlung Tsangpo was mainly composed of Ca and HCO . In addition, with a large amount water discharged into the river, groundwater (e.g., numerous chloride-rich hot springs) is another potentially important source of ions that affect the water chemistry in the Yarlung Tsangpo basin. Although watercourses on the Tibetan Plateau can generally be considered pristine, concentrations of some toxic elements (i.e., Cd and Pb) were found to be higher than the WHO guideline for drinking water due to increasing influence from anthropogenic activities (e.g., tourism, mining operations and municipal wastewater discharge), which constitute a risk to human livelihoods in both local and surrounding regions. [ABSTRACT FROM AUTHOR]

The pH, EC (electric conductivity), δO and major ions in melt water, precipitation, runoff and groundwater samples which were collected in Baishui basin were analyzed. Based on chemical analysis, the characteristic variations are analyzed in this paper. The melt water, precipitation, runoff and groundwater were Ca/Mg/HCO type with similar ion compositions but showed different ion concentrations. Normally the content is high in groundwater and runoff water but low in melt water and precipitation. From the upper basin glacier downward, there was a general increasing trend for the total ion concentrations in basin. HCO and Ca accounted for more than 80 % of total ions in samples, indicating that ions mainly came from limestone and water typical of carbonate solution water. Water-rock interaction is the significant contributor to water geochemistry. The concentration of inorganic ion in melt water had an obvious diurnal variation with temperature change. The δO values increases with the altitude decrease; the similarity of δO in runoff and groundwater samples was due to their frequent transformation in karst regions. [ABSTRACT FROM AUTHOR]

This paper mainly analyzed the isotopic effect of precipitation in the Yarlung Zangbo River. On the whole, the isotopic compositions of most water samples fall on the upper right of the global meteoric water line. According to δD and δO data of the samples, the precipitation equation is figured out as δD=8 δO+10, showing that they are derived from precipitation but have experienced intensive evaporation. With obvious region-continental effect (a continuous depletion in heavy isotopes in water bodies occurs with increasing distance from the coast), the water presents a reducing trend of δD and δO westwards and southwards. Altitudinal effect is evident here, occurring in both trunk stream and main branches of the Yarlung Zangbo River. The distribution of water isotopic compositions is concerned with the movement of precipitation clouds from the Bay of Bengal and the Nujiang River and is affected by the topographic and climatic conditions of the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Abstract: Water level and chemistry of Lake Qinghai are sensitive to climate changes and are important for paleoclimatic implications. An accurate understanding of hydrological and chemical budgets is crucial for quantifying geochemical proxies and carbon cycle. Published results of water budget are firstly reviewed in this paper. Chemical budget and residence time of major dissolved constituents in the lake are estimated using reliable water budget and newly obtained data for seasonal water chemistry. The results indicate that carbonate weathering is the most important riverine process, resulting in dominance of Ca2+ and DIC for river waters and groundwater. Groundwater contribution to major dissolved constituents is relatively small (4.2 ± 0.5%). Wet atmospheric deposition contributes annually 7.4–44.0% soluble flux to the lake, resulting from eolian dust throughout the seasons. Estimates of chemical budget further suggest that (1) the Buha-type water dominates the chemical components of the lake water, (2) Na+, Cl−, Mg2+, and K+ in lake water are enriched owing to their conservative behaviors, and (3) precipitation of authigenic carbonates (low-Mg calcite, aragonite, and dolomite) transits quickly dissolved Ca2+ into the bottom sediments of the lake, resulting in very low Ca2+ in the lake water. Therefore, authigenic carbonates in the sediments hold potential information on the relative contribution of different solute inputs to the lake and the lake chemistry in the past. [Copyright &y& Elsevier]

Abstract: The Tibetan Plateau covers an area of about one fourth of Europe, has an average elevation over 4000m above sea level, and is the water sources for about 40% of world''s population. In order to foresee future changes in water quality, it is important to understand what pressures are governing the spatial variation in water chemistry. In this paper the chemistry including major ions and trace elements in the headwaters of four major Asian rivers (i.e. the Salween, Mekong, Yangtze River and Yarlung Tsangpo) in the Tibetan Plateau was studied. The results showed that the content of dissolved salts in these Tibetan rivers was relatively high compared to waters from other parts of the world. The chemical composition of the four rivers were rather similar, with Ca2+ and HCO3 − being the dominating ions. The exception was the Yangtze River on the Plateau, which was enriched in Na+, Cl−, SO4 2− and Li due to silicate weathering followed by strong evaporation caused by a negative water balance, dissolution of evaporites in the catchment and some drainage from saline lakes. The concentrations of heavy metals (Cu, Co, Cr, Ni, Cd, Pb, and Hg) and As, NH4 + were generally low in all the rivers. Anthropogenic impacts on the quality of the rivers were identified at a few locations in the Mekong River and Yarlung Tsangpo basins. Generally, the main spatial variation in chemical compositions of these under studied rivers was found to be governed mainly by difference in geological variation and regional climatic-environment. Climate change is, therefore, one of main determining factors on the water chemical characteristics of these headwaters of Asian major rivers in the Tibetan Plateau. [Copyright &y& Elsevier]

The uplift of the Tibetan Plateau has caused the development of many high-enthalpy geothermal fields that are rich in exploitable rare and dispersed resource elements. However, the mechanism of the unusual enrichment of these resource elements is still unclear. From a geochemical viewpoint, including major chemical compositions, some rare and dispersed resource elements and trace elements in geothermal water and some river samples from the northern Lhasa block (saline lake area), the southern Lhasa block (Gangdise volcanic belt) and Tethyan Himalaya in Tibet, this study provides new insights into the mechanism of the hydrochemical evolution of the Tibetan geothermal system. The Cl-type geothermal waters in the Gangdise volcanic belt and Tethyan sedimentary area show similar chemical characteristics that are apparently different from that of surface cold waters. The concentrations of Sb, Tl, As, K, Cs, Li, Rb, Ga, B, Cl, Th, Sc, Mn, V, and Ti in Cl-type geothermal waters are at least one order of magnitude higher than those in surface cold waters, but the concentrations of Ca, Mg, Ni, Cr, Zn, Fe, Co, Cu, Pb, and U in Cl-type geothermal waters are slightly higher or even lower than those in surface cold waters. Some rivers and streams in Tibet also show high concentrations of toxic elements. These rivers and streams are mainly polluted by geothermal spring discharge and are unsuitable for drinking. Some ions and elements (such as Ca, Mg, Ba, Sr, SO and Mn) in HCO -type geothermal waters from sedimentary rocks are affected by the availability of soluble minerals such as calcite, dolomite and gypsum. However, the other dissolved elements in HCO-type geothermal waters show the characteristic of mixing Cl-type geothermal waters with surface cold waters. The origin of deep fluids in Cl and HCO-type springs is related, and this origin probably involves the contribution of crustal partial melting rather than single rock leaching. Thus, deep circulating groundwater mixes with residual magmatic fluids and evolves into the unusual enrichment of geothermal mineral resources. [ABSTRACT FROM AUTHOR]

A total of 31 river water samples were collected from the headwater of the Yangtze River and its tributaries across Shigu Town to Mt. Tangula region. Water chemistry analysis was carried out to investigate water quality in the upstream Yangtze River. The results show that the headwaters of Yangtze River are turbid and have an alkaline environment with pH ranges from 8.3 to 9.3. The oxidation reduction potential (ORP) of the water varies from −77.1 to −134.2 mv with an average of −88.8 mv, indicating an anoxic water surface. Based on the ions analysis, the water chemistry of headwaters of the Yangtze River is affected by mineral (magnesium and calcium sulfate) weathering, evaporation-crystallization processes and ground water discharge. Concentrations of ions and elements except Hg in the headwaters of Yangtze River presented a trend of decreasing with the downward of altitude. All heavy metals and other toxic elements concentrations in this study were under the WHO and GB (China national standards) guidelines. But attention should be given to Hg because the concentration of Hg (2.6 ng/l) was much higher than the world average (0.07 ng/l) and it increased as the river flows down, which may become a threat to the inhabitants in the downstream area of the river. [ABSTRACT FROM AUTHOR]

The often extraordinary shell forms and shapes of gastropods found in palaeolakes, such as the highly diverse Gyraulus fauna of the famous Steinheim Basin, have been puzzling evolutionary biologists for centuries, and there is an ongoing debate whether these aberrant shell forms are indicative of true species (or subspecies) or ecophenotypic morphs. Interestingly, one of the Steinheim Gyraulus morphs - a corkscrew-like open-coiled shell - has a recent analogue in the Lake Bangong drainage system on the western Tibetan Plateau. Therefore, a combination of morphological, molecular, palaeolimnological, and ecological analyses was used in this study to assess whether the extraordinary shell shape in Gyraulus sp. from this drainage system represents a (young) ecophenotypic phenomenon or if it has been genetically fixed over an extended period of time. Our morphological, ecological, and palaeolimnological data suggest that the corkscrew-like specimens remain restricted to a small pond near Lake Bangong with an elevated pH value and that the colonization may have occurred recently. The phylogenetic reconstruction based on two gene fragments shows that these nonplanispiral specimens cluster within the previous described Tibetan Plateau Gyraulus clade N2. A network analysis indicates that some haplotypes are even shared by planispiral and nonplanispiral specimens. Given the ephemerality of the phenomenon, the compact network patterns inferred, the likely young phylogenetic age of the aberrant Gyraulus shells studied, and the ecological peculiarities of the study site, we suggest that the evolution of the aberrant shell forms on the Tibetan Plateau could likely be considered as a rapid ecophenotypic response, possibly induced by ecological stress. This finding may thus have implications for the ongoing debate about the processes that have caused the extraordinary shell diversity in palaeolakes such as the Steinheim Basin. [ABSTRACT FROM AUTHOR]