Geothermal Exploration Using Geochemical Data; Study Case: Parang Wedang Geothermal Field, Indonesia

Along Java Island, there are more than 20 geothermal areas, including the Parang Wedang geothermal field. This field is classified as a non-volcanic geothermal system, because it is not associated with any active volcano. Permeable fault zones play an important role in fluid pathway occurrences. However, what is the source of the fluid is still debatable. Here we show results of geochemistry data analysis to determine the characteristics of Parang Wedang geothermal fluid. Cl-HCO3-SO4 ternary diagram of the Parang Wedang geothermal fluids reveals that the fluids contain high chloride. Additionally, Na-K-Mg ternary diagram of the fluid samples shows a character of partial equilibrium. It is possible that the geothermal fluids originate from magmatic activity related to the subduction process upward and mix with meteoric water. And then, these mixed water move upward further to the surface before the water reach full equilibrium. Our interpretation is consistent with seismology tomography studies that indicate magmatic fluid pathway from the subduction of Eurasian and Australian plates.