Geochemistry of a Non Volcanic Geothermal Area in Maranda, Poso Regency, Central Sulawesi, Indonesia

Abstract

Indonesia has many geothermal areas which are associated with non volcanic environment. One of them is Maranda geothermal area, Poso Regency, Central Sulawesi. There are several manifestation such as hot springs, mud pots, and steaming ground. The temperatures of manifestations are around 42-100 oC (Maranda-6, Maranda-7, steaming ground, and mud pots have highest temperature), the pH is around 6,4-9,5. It is associated with the youngest magmatic activity, occured in the Plio-Pleistocene (granite intrusion). The geological structure controlling the Maranda geothermal area is dominated by north-south trending structures associated with reverse faulting of Poso which is in the west and the pattern structure relative east-west trending. The Maranda geothermal system has chloride type of waters based on Cl-SO4-HCO3 diagram and plots in partial equilibrium zone based on Na-K-Mg diagram. The temperature of reservoir is about 160-180oC from water geothermometry.