Geochemical Genesis of Boron In Geothermal Waters: Insight From A Comparison Between Daggyai and Xiong’An Geothermal Systems In China

Boron is a soluble and incompatible element in geothermal waters, and is often used to trace the source of geothermal fluids. However, the sources of boron in geothermal waters are still highly controversial. In this study, a typical high temperature geothermal system in the Yunnan-Sichuan-Tibet Geothermal Province (Daggyai) and a typical low-medium temperature geothermal system in the North China Plain (Xiong’an New Area) were selected to investigate the geochemical origin of boron in geothermal fluids. Daggyai is a magmatic geothermal system, and the abnormally high concentration of boron in geothermal waters mainly comes from the recharge of magmatic fluids and the leaching of host rocks. In Xiong’an New Area, the boron concentrations of geothermal waters from Wumishan Formation are significantly higher than those from Guantao Formation. The boron in geothermal waters of the Guantao Formation mainly originates from the dissolution of albite in the sandstone reservoir, while that of Wumishan Formation may be recharged by ancient sedimentary waters in addition to the leaching of carbonate rocks. This study indicates that boron in geothermal waters can be used as a useful tool to identify the geological geneses of geothermal systems.