The isotopic composition and parameters for deuterium excess of brines, which were sampled in the Si-chuan Basin, show obvious regularities of distribution. The brine isotopic composition shows distinct two systems of...The isotopic composition and parameters for deuterium excess of brines, which were sampled in the Si-chuan Basin, show obvious regularities of distribution. The brine isotopic composition shows distinct two systems of marine and terrestrial deposits, with the Middle Triassic strata as the boundary. Brine hydrogen isotopic composition of marine deposits is lower while oxygen isotopic composition is higher than that of the SMOW, respectively, indicating that the brines were derived from seawater with different evaporating degrees at different times. From the Sinian strata, up to the Cambrian, Permian Maokou Formation and the Triassic Jialingjiang Formation, the δD values of brines tend to become relatively positive with the strata becoming younger. Brines of terrestrial deposits are considered to have been derived from precipitation and their isotopic composition is close to the globe meteoric water line (GMWL). Brines of transitional deposits between marine and terrestrial ones (the Upper Triassic Xujiahe Formation) have δD and δ18O values falling between the two end members of marine deposit brines and precipitation, indicating that the brines are a mixture of precipitation and vaporing seawater. Water samples from the brine-bearing strata of different ages show various deuterium excesses (d) with an evident decreasing trend as the age of strata gets older and older. Brine-bearing strata of the Triassic Leikoupo-Jialingjiang Formation, the Permian Maokou Formation, the Cambrian and Sinian strata are all carbonate rocks which have experienced intensive water/rock reaction and the deuterium excess essentially changes with time. All brine-bearing-strata surrounding the basin or faults, as well as those brine wells exploited for resources, have been obviously influenced by the precipitation supply. Therefore, the deuterium excesses of their brines have increased to different extents, depending on the amount of involvement of meteoric water. The variation and distribution of d values of the brines from different Triassic strata are related to the embedded depth of the strata. The deuterium excesses of brines become lower with increasing burial depth of the strata.展开更多
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.Accord...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 δ18O data of the samples,the precipitation equation is figured out as δD=8 δ18O+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 δ18O westwards and southwards.Altitudinal effect is evident here,occur-ring in both trunk stream and main branches of the Yarlung Zangbo River.The distribution of water isotopic compo-sitions 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.展开更多
文摘The isotopic composition and parameters for deuterium excess of brines, which were sampled in the Si-chuan Basin, show obvious regularities of distribution. The brine isotopic composition shows distinct two systems of marine and terrestrial deposits, with the Middle Triassic strata as the boundary. Brine hydrogen isotopic composition of marine deposits is lower while oxygen isotopic composition is higher than that of the SMOW, respectively, indicating that the brines were derived from seawater with different evaporating degrees at different times. From the Sinian strata, up to the Cambrian, Permian Maokou Formation and the Triassic Jialingjiang Formation, the δD values of brines tend to become relatively positive with the strata becoming younger. Brines of terrestrial deposits are considered to have been derived from precipitation and their isotopic composition is close to the globe meteoric water line (GMWL). Brines of transitional deposits between marine and terrestrial ones (the Upper Triassic Xujiahe Formation) have δD and δ18O values falling between the two end members of marine deposit brines and precipitation, indicating that the brines are a mixture of precipitation and vaporing seawater. Water samples from the brine-bearing strata of different ages show various deuterium excesses (d) with an evident decreasing trend as the age of strata gets older and older. Brine-bearing strata of the Triassic Leikoupo-Jialingjiang Formation, the Permian Maokou Formation, the Cambrian and Sinian strata are all carbonate rocks which have experienced intensive water/rock reaction and the deuterium excess essentially changes with time. All brine-bearing-strata surrounding the basin or faults, as well as those brine wells exploited for resources, have been obviously influenced by the precipitation supply. Therefore, the deuterium excesses of their brines have increased to different extents, depending on the amount of involvement of meteoric water. The variation and distribution of d values of the brines from different Triassic strata are related to the embedded depth of the strata. The deuterium excesses of brines become lower with increasing burial depth of the strata.
文摘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 δ18O data of the samples,the precipitation equation is figured out as δD=8 δ18O+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 δ18O westwards and southwards.Altitudinal effect is evident here,occur-ring in both trunk stream and main branches of the Yarlung Zangbo River.The distribution of water isotopic compo-sitions 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.
