Volcanostratigraphy Study of Way Ratai Geothermal Prospect in Pesawaran Regency, Lampung Province

Abstract

Way Ratai geothermal area is volcanogenic geothermal system located in Pesawaran Regency, Lampung Province, Indonesia. The presence of the geothermal system in this area is indicated by the distribution of geothermal manifestations such as hot pools and hydrothermal alteration. Understanding the geological setting of this area plays an important role in considering the prospect of geothermal resources. This paper aims to determine the prospect of the geothermal area by investigating the relationship between volcanic units, geological structures, and geothermal systems in the Way Ratai. The study was conducted with remote sensing analysis and volcanostratigraphy study to interpret the stress regime, the permeability zone analyzed by the lineament density, the lithological unit, and the dimension of the volcanoes. Three groups of structural lineaments are identified from remote sensing analysis: NW-SE trend, NNE-SSW trend, and circular feature. Mount Ratai Volcanic Crown consists of 19 lithological units such as lava dome, lava flow, pyroclastic products, and surface deposit. The estimation of the volcanic product dimension is about 55 km3 that widespread radially which indicates the presence of a significant heat source beneath the surface. The volcanic activities occurred during the Pleistocene to Holocene with andesitic composition. Based on the lineament density extraction, the prospect area located on the southern flank of Mount Ratai has good permeability. Lineament maps that are overlaid by volcanic rock distribution maps will result in the relationship between the volcanostratigraphy units and the geological structure pattern of the area. From this study, the characteristics of the area show that this area has a good geothermal prospect to be developed and needs further investigation.