| Abstract |
The research area has two geothermal systems, i.e. Gede-Pangrango and Pancar, which cover Cianjur, Sukabumi, and Bogor districts, West Java. Determination of the geothermal systems’ conceptual model and recharge areas are the purpose of this research. The main data are stable isotope 18O, 2H, and tritium from cold springs and river water, also complementary secondary data. The Gede-Pangrango geothermal system has two hot springs, chloride-sulfate water (51oC) and chloride-bicarbonate water (40oC). Solfatara (167oC) and fumarole (70oC) are at the Mt. Gede’s peak. Its reservoir has a temperature of (tNa-K)=275-295oC, chloride concentration: 3144 mg/kg and at elevation 250 to -500 m. The clay rock is at elevation 1,000 to 250 m. The Pancar geothermal system has two hot springs, sulfate water (54oC) and chloride-sulfate (66oC). Its parent fluid has a temperature of (tNa-K)=190-210oC, chloride concentration: 4055 mg/kg and at elevation -1,000 to -1,750 m. The clay rock is at elevation 0 to -1,000 m. The 18O and 2H isotope analysis shows that the recharge area of the Gede Volcano geothermal system is at elevation 1,100-1,200 m, latitude 9,263,000-9,263,500 mS, located in a high FFD zone (30-60 km/100 km2), and volcanic rock, while the recharge area of the Pancar Volcano geothermal system is at elevation 850-900 m, latitude 9,263,500-9,263,800 mS, located in a medium FFD zone (20-30 km/100 km2) and sedimentary rock. The value of cold water tritium in the study area is 2.04-3.66 TU, indicating that cold water in the research area is a mixture of submodern groundwater (infiltrated before 1952) and groundwater which recently infiltrated the ground. |