摘要
The geothermal waters from the Rehai magmatic hydrothermal system, located in the Tengchong volcanic region, south-western China, are characterized by diversified hydrochemical types and a wide range of pH values. The neutral hot springs in Rehai generally have much higher arsenic concentrations than the acid hot springs. Further inspection shows that the acid, sulfate-rich springs are essentially locally-perched groundwaters heated by H2S-rich steam separated from deep geothermal fluid. Hence, the dissolution of near-surface rocks at moderate temperatures is the sole source of arsenic in the steam-heated acid springs. In comparison, the arsenic in the neutral hot springs, which represent the deep-circulating geothermal fluids, comes from long-term water-rock interactions at much higher reservoir temperatures. Moreover, the possibility that magmatic fluid is a potential arsenic source for the neutral springs in Rehai cannot be ruled out.