Geochemistry of Rajgir-Munger Metasedimentary Springs of Bihar, India

Abstract

Present investigation is based on the chemical composition of springs located along the Rajgir-Munger metasedimentary belt of Munger, Nalanda and Gaya district of Bihar. Thermal springs of Rajgir area are issuing through the quartzites hills of 358-420 Ma age. The pH of the thermal springs of Rajgir area are slightly acidic in nature (pH = 5.3 to 5.8 at 25 °C) with surface temperature range between 35 to 50 °C, whereas the cold springs of Munger are near neutral in nature. Piper diagram suggests that the water type of thermal and cold springs are Ca-HCO3 type, due to their circulation through sedimentary formations. Na/K, Na/Ca and Cl/HCO3 ratio suggests that the both thermal springs at Tapoban in Rajgir are fed by the same reservoir. Estimated reservoir temperature based on silica geothermometer in the range of 61 to 95 °C, which indicates a low enthalpy geothermal system. Rajgir thermal springs are characterized by the negative gravity anomaly (-50 mGal) and it shows that the circulation of the thermal springs are through the fault surface. Since this area is characterized as low enthalpy geothermal field, therefor it can be used for other geothermal uses like aquaculture, agricultural drying, bathing etc.