SUBSURFACE STRUCTURE IDENTIFICATION USING AIRBORNE GRAVITY IN GEOTHERMAL POTENTIAL SURROUNDING AREA IN THE WEST OF SERAM ISLAND MALUKU

• Main Author: Budiani Septianingsih, Mela
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/70348
• Institution: Institut Teknologi Bandung

The discovery of geothermal manifestations in the form of hot water is an early indication that there is geothermal potential in the Kelapa Dua and Pohon Batu areas, western Seram. In previous studies it was estimated that there is a top reservoir at a depth of 400 m to 700 m in the Pohon batu Manifestation. The geothermal manifestations of Kelapa Dua and Pohon batu are located in the Banda arc where there is no volcanic activity, and the discovery of intrusive igneous intrusions made this research even more interesting. This study aims to identify subsurface structures around geothermal manifestations by utilizing airborne gravity data. The free air anomaly data obtained was corrected for topography using a rectangular prism approach. Spectrum analysis was performed on two measurement profiles, and a bandpass filter was performed to obtain residual anomaly. Subsurface modeling is done by 2D forward modeling. The subsurface structure obtained on the second measurement profiles is close to the geothermal manifestations of Kelapa Dua, namely the Taunusa Formation (Pzta) schist rocks with a density of 2.54 - 2.65 ????????/????????3, sandstones belonging to the Fufa formation (TQf) with a density of 2.35 ????????/????????3, phyllite rocks of the Tehoru Formation (Ptrt), and there is an Ultramafic igneous intrusion (Jku) with a density of 2.76 ????????/????????3. This igneous rock breaks through the basement with a density of 2.79 ????????/????????3 and the other three metamorphic rocks to the surface. The basement in this study is estimated to be Schist-Mica rock belonging to the Permian age Kabipoto complex. The heat source which has a density of 2.87 ????????/????????3 This nonvolcanic area is estimated to have two possibilities, namely the first comes from the decay of radioactive elements which are usually found in plutonic rocks. Second, the existence of this heat source is thought to be in the form of deformed continental crust The subsurface structure on profile four is close to the manifestation of the Pohon Batu, it is estimated that there are Silt rocks which are included in Alluvium rocks (Qa) with a density of 1.4 ????????/????????3, Schist rocks of the Taunusa formation (Pzta)with a density of 2.59 to 2.73 ????????/????????3, the Phyllite rocks of the Tehoru (Ptrt) formation with a density of 2.5 to 2.6 ????????/????????3, and there is a basement which is thought to be a Mica-Schist rock with a density of 2.72 ????????/????????3are included in the Permian age Kabipoto complex. The heat source with a density of 2.77 ????????/????????3 in the manifestation area of the Tree Rock is thought to originate from deformed continental crust. On these two profils, which are approximately 4 km from the emergence of geothermal manifestations, no permeable rocks are found that function as reservoir rocks, and no impermeable rocks that function as caprock rocks are found. However, on these two trajectories there is a normal fault in the southeastern part which is thought to be the entry point for meteoric water. Then the heat source in the geothermal manifestation area of Kelapa Dua and Pohon Batu is thought to originate from deformed continental crust because in this area there is active plate movement