The Isotopic and Chemical Characteristics of Geothermal Fluids from Two Selected Hot Spring Areas in Jiangxi Province, SE-China

Abstract

Two typical low temperature geothermal areas, the Hengjing and Gangxinan areas from Jiangxi province in SE-China, were selected for chemical and isotope studies of selected warm and cold groundwater circulating in the areas. Thermal waters from both the Hengjing and Gangxinan hot spring areas are classified as HCO3 type water. Na-K-Mg triangular diagrams indicate that the thermal waters from the Hengjing area are partially equilibrated or mixed waters, whereas those from the Gangxinan area are immature. The Na-K-Mg-Ca diagram indicates that the temperature within the Hengjing geothermal reservoir is in the range of 130~180°C. Oxygen and hydrogen isotope study of the thermal waters suggest localized precipitation origin. The recharge altitudes are around 350 m~800 m and 530 m~1460 m for hot springs in the Hengjing and Gangxinan areas, respectively. Helium and light carbon isotopes from Hengjing geothermal fluids show that they could partly be derived from the mantle, whereas those from Gangxinan are considered to be derived from the upper most crustal radiogenic production and also by addition of much depleted 13C.