GEOLOGY OF GEOTHERMAL SYSTEM IN COMPLEX METAMORPHIC SETTING IN THE AREAS OF PATAH RIVER, RESO RIVER, AND PEMALI RIVER, BURU ISLAND

• Main Author: Jati Pamungkas, Kharits
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/69641
• Institution: Institut Teknologi Bandung

Geothermal system associated with metamorphic rocks are rare, one of which is in the Jinlun Geothermal Field, Taiwan. In Jinlun Geothermal Field, the heat source comes from hot rocks and high-angle geological structures become the dominant permeability controller. The geothermal system in the metamorphic complex is significantly different from the geothermal system associated with volcanoes, although the presence of magma as a heat source can be found in metamorphic areas. The research area which is located on Buru Island is a geothermal system associated with metamorphic rocks. The geothermal potential is characterized by the appearance of thermal manifestation, e.g., hot spring, fumarole, steaming ground, and altered rocks. The geological survey conducted by PSDG was carried out in 2007, however, detailed geological mapping in the Patah, Reso, and Pemali Rivers areas are not yet to be completed. The purpose of this research is to understand the geological setting that controls the geothermal system in Buru Island, especially those aspects related to lithology, hydrothermal alteration, and its influence on the geothermal system and permeability. This research focuses on the Patah, Reso, and Pemali Rivers in Buru Island. The methods used are satellite image analysis, petrological and petrographic analysis, and mineral spectral analysis. Satellite imagery analysis was used to create a map of geomorphological units that will aid in the delineation of units in geological maps, alteration zones, and interpretation of geological structures. Based on the geomorphological analysis, the research area consists of Alluvial Fan, Colluvial Fan, Flood Plain, Alluvial Plain, Talus Deposition Hill, Undulated Hill, Fault Ride Complex, Fault Hills 1. The result of the petrology and petrographic analysis shows that the research area consists of 6 lithological units, i.e., Garnet-Biotite Schist, Biotite-Muscovite Schist, Chlorite-Muscovite Schist, Alluvial 1, Alluvial 2, and Alluvial 3. The geological structure that was developed in the study area is a northwest-southeast fault with a high-angle on the surface with gradually flattens below the surface and a southwest-northeast fault. According to the result of remote sensing, petrographic, and spectral analysis, there are three alteration zones, i.e., Tourmaline Zone (relic), Chlorite-Illite Zone, and Alunite Zone (associated with the present-day system). The result of the study indicates that the geothermal system in the Patah River, Reso River, and Pemali River areas are a non-volcanic and fault-controlled geothermal system. The heat source is considered as a deep heat flow because there is no direct evidence of magmatic activity on the surface. Hydrothermal fluid flows from the reservoir through the damage zone of faults in metamorphic rocks, then discharges as surface manifestations around the Pemali River. The existence of alteration zones in the Patah and Reso Rivers indicates the presence of hydrothermal fluids in the past.