| Title | Geology and Geothermal System in Rajabasa Volcano South Lampung Regency, Indonesia (Approach to Field Observations, Water Geochemistry and Magnetic Methods) |
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| Authors | I Gede Boy DARMAWAN, Lucas Donny SETIJADJI, Djoko WINTOLO |
| Year | 2015 |
| Conference | World Geothermal Congress |
| Keywords | Rajabasa volcano, geothermal, water geochemistry, reservoir, magnetic methods |
| Abstract | The existence of geothermal manifestations in Rajabasa volcano indicate the potential of geothermal energy in this area. Some geothermal manifestations are found in the north and south foothills of Rajabasa, such as hot springs and fumaroles. This research conducted to determine the geology and geothermal system in Rajabasa volcano based on interpretation of geological field observations, water geochemistry and magnetic methods. Geological observations conducted to determine the geological and structural conditions that affect the existence of geothermal manifestations in Rajabasa volcano. The result of petrographic analysis of fresh rock samples show that Rajabasa volcano dominated by andesitic lava with the main composition of plagioclase and clinopyroxene. While the XRD analysis of altered rock samples show the existence of minerals such as alunite, smectite, kaolinite, albite and chlorite. Water sampling conducted in the area of geothermal manifestations such as Way Belerang, Way Merak, Kecapi Simpur, Rajabasa and Mount Botak. Surface temperature are varied, Rajabasa hot spring around 30°C, Kecapi Simpur hot spring around 56°C, Way Belerang and Way Merak around 90°-95°C, while in Mount Botak around 102°-105°C. Water type analysis show the Kecapi Simpur dan Rajabasa hot spring manifestation is bicarbonate water (HCO3-), Sulfate water (SO42-) for Way Belerang and Chlorite water(Cl-) for Mount Botak manifestation. Three dimentional modeling of magnetic data has resulting an areas that have very low magnetic susceptibility at a depth of 1500m. This result was also confirmed by the results of water chemical analysis with geothermometer method that estimates of reservoir temperatures around 260°C and statistical reservoir temperature methods of geothermal drilling in several locations in Indonesia were estimated reservoir depth of about 1500m. |