Sistem Geothermal Montelago, Pulau Mindoro Filipina, Berdasarkan Kajian Geokimia Air dan Tanah
This study investigated the geothermal system of Montelago, Mindoro island, Philippines, This sudy to update information about geothermal system of Montelago which is non volcanic system by characterize the surface manifestation, water and soil gas chemistry.
Thermal manifestations in the Montelago geothermal prospect area consist of warm-hot springs (30-77oC) in Naujan Lake Montemayor and Buloc-buloc warm bubbling springs with gas seepage. These manifestation are controlled by Lugta Fault trending NE-SW from Montemayor to Naujan Lake Springs Group. The methodology of this study are water analyses of anion-cation, stable isotope of δ18O and δD, pH and Hg of soil, CO2 of soil gas to identification heat source, reservoir, upflow zone and outflow zone of the Montelago geothermal system.
The hydrogeochemical pattern of geothermal fluid in this area is divided into 2 areas, south and north areas. South reservoir is represented by Naujan manifestation with chloride type as upflow zone and Montemayor manifestation with bicarbonate-chloride type as outpflow zone. Estimation of reservoir temperature is 180-200oC. Whereas, north reservoir is represented by Buloc-Buloc manifestation with bicarbonate type.
Stable isotope δ18O and δD analyses in the study indicate that the thermal waters are originally meteoric. Also it is not influenced by volcanic-magmatic activity or sea water intrusion eventhough there are manifestation in the edge of the beach. Heat source is not influenced by magmatic fluid, but diorite intrusion. However, with Lugta Fault controling Naujan and Montemayor manifestations we can conclude that geothermal system in the area is heat sweap.
Dr. Eng Suryantini ST. Dipl. Geothermal Tech., M.Sc