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Abstract: We collected riverbed and suspended sediments in the upper Yangtze River (the headwaters, Jinsha, Yalong, Minjiang and Daduhe Rivers) flowing on the eastern Tibetan Plateau and analyzed their trace element concentrations. The results show that: (1) selected fractionations of different elements in the riverbed and suspended sediments indicate the influence of sedimentary sorting. Higher concentrations of transition elements V, Ti, Ni, Co, Cr, and Sc in the riverbed sediments of Jinsha River catchment from Shigu to Panzhihua imply enrichment of mafic minerals owing to high density. Enrichments of high field strength elements Zr, Hf, Nb and Ta in the riverbed sediments relative to the suspended sediments reflect the characteristics of heavy minerals accumulation into coarse-grained fraction. The lower Eu/Eu* ratios in the riverbed sediments can also be attributed to the enrichment of heavy minerals such as monazite and allanite in the processes of transportation and sorting; (2) the upper Yangtze riverbed and suspended sediments show a mixing trend of felsic and mafic endmembers. Granitoids are important source rocks for the sediments in the source area and the Permian Emeishan continental basalts dominate the geochemistry of the sediments in the Jinsha River catchment from Shigu to Panzhihua. Moreover, industrial activities in the Panzhihua City may have an important contribution to the upper Yangtze River sediments. [Copyright &y& Elsevier]

This study examines the effects of hydrologic sorting and mixing of sources on the Sr-Nd isotopic compositions of suspended sediments at different water depths. The samples were collected from three layers (surface, middle and bottom) at Datong hydrological station of Yangtze River during the flood season of 2010. Our results show that, Sr/Sr values decrease from surface to bottom, ranging from 0.730332 to 0.720857. ɛ(0) values range from −14.75 to −10.09, with surface sediments being the most negative. The isotope composition at the middle layer can best represent the mean isotopic composition of the total suspended sediments transported by a river. It is believed that the stratification of Sr-Nd isotope is attributable to mixing of sediments from different sources due to hydrological sorting. Sediments from the upper stream are found to be coarser, and tend to contribute more to the lower water column. Although Sr-Nd isotope is a well acknowledged tool to trace sediment provenance, the current study suggests that the grain size of the samples and the sampling locations should be taken into consideration when applying this method to provenance study. [ABSTRACT FROM AUTHOR]

Abstract: We collected riverbed sediments of the headwaters of the Yangtze River (Chumaer River, Tuotuo River, Gaerqu River and Buqu River), Tongtian River and Jinsha River (HTJR) flowing on the eastern Tibetan Plateau and analyzed their mineralogical features, major and trace element contents. The results show: (i) very poor correlations of Na2O, K2O, CaO, Ba, and Sr to SiO2, LREE to Th, HREE to Hf, and Ta/La to Ti, and characteristics of Eu anomaly (the ratios of (Eu/Eu*) N range from 0.60 to 0.83 with an average value of 0.71) all indicate that the Jinsha River sediments have not undergone much mineralogical sorting; (ii) illite and chlorite are predominant clay minerals, and quartz, calcite, dolomite, albite, and K-feldspar are prevailing non-clay minerals. The characteristics of mineral assemblage indicate relatively weak chemical weathering degree in these river basins; (iii) very high contents of Fe2O3, MgO, TiO2, Sc, V, Cr, Co, and Ni at Panzhihua mainly result from the huge-sized V–Ti magnetite deposits occurred in layered gabbroic intrusion; and (iv) the chemical alteration index (CIA) in the HTJR ranges from 46.5 to 69.2 and with an average value of 60.5 which indicates relatively weak weathering degree. [Copyright &y& Elsevier]

Abstract: Water and sediment samples were collected from the headwaters (the Tuotuo River and Chumaer River) of the Yangtze River, Tongtian River and Jinsha River (HTJR) originating from the Qinghai–Tibet Plateau (QTP). Sr and 87Sr/86Sr have been measured to analyze temporal and spatial variation characteristics and determine relative contributions from atmospheric inputs, anthropogenic activities and rock weathering. These results show that Sr in the HTJR waters ranges from 1.37 to 11.07 µmol L− 1, and 87Sr/86Sr from 0.70948 to 0.71409. The headwaters Tuotuo River and Chumaer River receive ~95% of their Sr from evaporite dissolution. The influence of evaporite decreases gradually downwards from source area as increase in discharge. Silicate weathering contributes 4.9%–28.2% of dissolved Sr to the Jinsha River mainstream and 11.5%–42.4% to the tributaries. 87Sr/86Sr ranges from 0.71034 to 0.71177 in the Jinsha River mainstream, which is higher than those in other reaches of the Yangtze River. In the Jinsha River suture belt, granitoids and metamorphic rocks with relatively high 87Sr/86Sr are exposed. Moreover, carbonate weathering is another important source of Sr in the Jinsha River waters. It is estimated that 15.9%–46.8% of Sr in the mainstream and 37%–64.5% of Sr in the tributaries are derived from carbonate weathering. Contribution from atmospheric precipitation to the Sr in the HTJR is from 0.75% to 6.1% and influence of anthropogenic activities is slight. The 87Srex flux forcing changes in seawater Sr isotopic composition is 1.13×106 mol a− 1 for the HTJR at Yibin, being far lower than those in the Ganges and Brahmaputra and merely accounting for 1.36% of the total carried by the global rivers. Therefore, impact of the HTJR on steady increase of seawater 87Sr/86Sr ratio since 40 Ma may be very small. [Copyright &y& Elsevier]

Abstract: Water and sediment samples were collected from the headwaters of the Yangtze River, Tongtian He and Jinsha Jiang (upstream of the Yangtze River which flows on the eastern Qinghai-Tibet Plateau). A detailed geochemical study of the river system was carried out to determine: (i) temporal and spatial variations of the major ions and their implications; (ii) contribution of carbonate, silicate and evaporite to the river dissolved load and (iii) CO2 consumption via silicate weathering. Results show that cations derived from evaporite dissolution account for 44.7–82.8% of the total cations in the headwaters of the Yangtze River and increasing from SE to NW of the drainage basin. The contribution from silicate weathering gradually increases from the headwaters due to exposure of intrusive rocks and volcanic rocks in the Jinsha Jiang suture belt. Proportion of cations derived from silicate weathering to the total cations in river waters reaches a maximum at Panzhihua City, which is consistent with the abundant exposure of Cenozoic granitoids and Precambrian high-grade metamorphic rocks around Panzhihua. The Jinsha Jiang basin has higher silicate weathering rates but lower carbonate weathering rates than the middle and lower reaches of the Yangtze River. The calculated enrichment factors of potentially harmful metals in the river sediments are within the range of 0.33–2.59, indicative of level 1 or 2 contamination. The highest enrichment factor for Co, Cr and V is found in Panzhihua City, indicating that it has been influenced by anthropogenic sources. [Copyright &y& Elsevier]