| Abstract |
West Java have about 20 geothermal prospects which have been reported. Eight of them are existing geothermal field such as Kamojang, Darajat, Wayang Windu, and Salak-Awibengkok. The rest of geothermal prospects were still in exploration stage to get to know their geothermal system with geological, geophysical, and geochemical survey. Geochemical survey is used to evaluate characteristic of manifestastions, type fluid, and geothermometers. During this time, water geochemistry are used just to know geothermometers without consider an equilibrium of fluid and understand fluid process in either deep or shallow levels. This study focus on evaluation water geochemistry with Na-K-Mg ternary, Na-K/Mg-Ca and K-Mg/Quartz diagram to compare temperature equilibration each other, to consider the equilibrium of fluid, and deep and shallow process in some of West Java geothermal prospects such as Tanggeung, Jampang, Tangkuban Perahu, Papandayan, Mt. Kromong, Mt. Ciremai, and Panulisan. The K-Mg/Quartz diagram was compared two low temperature geothermometers to eliminate invalidity of each geothermometer which are caused by dilution process, equilibration with amorphous silica, or some residual effect of an acid zone. The Na-K/Mg-Ca diagram combines the Na-K geothermometer with equilibration of the system Mg-Ca. Both of them usually use to know the influence of shallow and low temperature processes. The preliminary results show a part of hot or warm springs in West Java geothermal prospects have fluids which do not come from reservoir and undergone dilution or mixing process. Other part of thermal discharges are a brine which come from deep liquid geothermal water with small influence of dilution or mixing process. Three graphical techniques were showing the shallow and deep temperature of each prospect with some explanation about equilibrium and processes of fluids rise from deep to surface. |