Gravity Interpretation of the RUW (Rendingan-Ulubelu-Waypanas) Geothermal System in Tanggamus Regency, Lampung, Indonesia

Abstract

Gravity interpretations have been done in the Rendingan-Ulubelu-Waypanas (RUW) geothermal system. A combination of both detailed data within the geothermal system and large-scale data from its surrounding, have been prepared by Pertamina, then processed and interpreted. Density determination is conducted by measuring the cores and cuttings and interpreted using the Nettleton method.
The gravity model shows the groups of volcanic lavas and pyroclastics occur across the RUW geothermal system. The basalt group of the Mt. Kukusan basaltic andesite lavas (KkBAl) in the southwest part of the study area, have average thickness is about 1000 m. The Mt. Rendingan andesite lavas (RdAl) in the northern part of the area with thickness about 1600 m underneath the Mt. Rendingan area, and 300 m within the Ulubelu caldera. The Mt. Rendingan pyroclastics (RdPr) in the north central area, the thickness is between 200 m and 300 m. The Mt. Duduk dacite lavas (DdDl) which occur in the north central area underneath the Mt. Rendingan pyroclastics, the thickness is between 800 m and 1000 m. The Mt. Sulah andesite lavas (SlAl) in the western part of the study area have thickness about 150 m.