HYDROGEOCHEMISTRY OF THE GEOTHERMAL SYSTEM OF MOUNT SEMINUNG AND SURROUNDING AREAS, SOUTH SUMATRA-LAMPUNG

• Main Author: Nadya Angelia Siregar, Naomi
• Format: Theses
• Language: Indonesia
• Subjects: Teknik (Rekayasa, enjinering dan kegiatan berkaitan)
• Online Access: https://digilib.itb.ac.id/gdl/view/87895
• Institution: Institut Teknologi Bandung

Mount Seminung, located south of Lake Ranau, is a post-caldera volcano within the Kumering Segment, part of the Great Sumatra Fault. The geothermal potential of this region is characterized by the presence of hot spring manifestations around the lake's edges, which are the northern and western parts of the mountain. This study aims to analyze the hydrogeochemical characteristics of geothermal fluids, evaluate subsurface processes, and visualize the hydrogeochemical model of Mount Seminung. Data were obtained through field surveys and previous studies, including measurements of physical water parameters (temperature, pH, TDS, salinity, and conductivity), chemical analysis of anions and cations, stable isotopes (?¹?O and ?²H), mineral alteration, and soil gas surveys (CO? and Hg). The results indicate that the manifestations exhibit bicarbonate water type, diluted with meteoric water. Stable isotope diagrams reveal isotopic enrichment due to fluid interactions with subsurface rocks. Geological structures, such as the Talang Kedu and Wai Uluhan faults, act as permeability pathways for fluid to reach the surface. Anomalies of Hg and CO? in soil gas were identified in Kota Batu and Talang Kedu, suggesting hydrothermal activity. The northern cluster of manifestations shows fluid discharge through the Wai Uluhan Fault, while the western cluster is influenced by the Talang Kedu Fault. Groundwater originates from the summit of Mount Seminung at elevations of approximately 1547–1597 masl, infiltrating shallow depths. The bicarbonate water flows from higher to lower elevations and emerges as hot springs along the lake’s edges. These hot springs result from the depression zone between Mount Seminung and Lake Ranau. The geothermal system’s hot springs represent an outflow, with the subsurface temperature distribution estimating reservoir depths between –677 and –725 masl.