The Early Chemical Characteristics of Geothermal Surface Features of Mount Lompobattang-Bawakaraeng, Gowa and Bantaeng Regency, South Sulawesi, Indonesia

Abstract

The Early study of surface geothermal features characteristics, based on surface chemical characteristics fluids is compulsory for understanding the geothermal system. The geothermal area of Mount Lompobattang-Bawakaraeng is mostly located in Gowa and Bantaeng Regency, South Sulawesi and these data were taken in 2018. The stratigraphy is composed of Tertiary Volcanic Sediments and Lompobattang-Bawakaraeng Quaternary Volcanic. The geological structures consist of caldera rim on the peak of Mount Lompobatang-Bawakaraeng and the fault structure of southwest-northeast and northwest-southeast which controls the appearance of geothermal manifestations on the surface. The active thermal manifestations are only warm springs, i.e., Batu Belerang, Pencong, and Parangloe warm springs. Batu Belerang warm spring is situated at an altitude of around 1400 masl, while Pencong and Parangloe warm springs are about 24 km from Batu Belerang warm springs with a lower altitude of around 168 masl. The temperature of the warm springs is around 31- 49.2 °C. There is one inactive surface geothermal manifestation, i.e., the Cold Acid Crater Lake Blue Luraya (Danau Biru Luraya) at the elevation of 1561 masl, the water temperature of 17 °C. The result of water analysis shows that warm springs Pencong and Parangloe have more dominant HCO3. The Batu Belerang and the Cold Acid Crater Lake Blue Luraya (Danau Biru luraya) are more dominated by SO4. In the triangular diagram that compares the relative concentrations of Na, K, Mg shows that the Pencong group (Pencong and Parangloe warm springs) is plotted in the lower boundary zone of partial equilibrium, while Lompobattang group (Batu Belerang warm springs and Cold Acid Crater Lake Blue Luraya (Danau Biru Luraya) is plotted in the corner of Mg (immature waters zone). The temperature of the system is probably only estimated at the shallow part of the system by SiO2 geothermometer about 125 °C and the Batu Belerang could be more than 125 °C.