Oxygen and hydrogen isotopic compositions of meteoric waters in the eastern part of Xizang

Summary

The δ¹⁸O and δD values for meteoric water samples collected from eastern Xizang and western Sichuan and Guizhou show a linear correlation and can be described by the following equation: δD = 8.22δ¹⁸O + 18.99. The isotopic compositions of these meteoric waters also exhibit obvious altitude effect. There have been found negative correlations between δ¹⁸O, δD and the elevation, which are characterized by −δO‰ = 0.0031H(m) + 6.19 and −δD‰ = 0.026H(m) + 30.20. The average δ¹⁸O and δD values for meteoric waters in the areas with an altitude of more than 4,000m above sea level are equal to -18.70 and -137.8‰, respectively. It is evident that the δ¹⁸O and δD values for plateau lake waters depend on their water supply. The δ¹⁸O and δD values for the water in lakes where the evaporation rate is greater than the recharge rate, are approximately three or four times higher than those of supply water, averaging -5.74 and -60.5‰, respectively. The oxygen and hydrogen isotopic compositions of geothermal waters as compared with those of local meteoric waters in adjacent areas show that the latter seems to be the main water-supply source.