STUDI GEOLOGI DAN GEOKIMIA MANIFESTASI PANASBUMI DI LAPANGAN WAY RATAI, KABUPATEN PESAWARAN, LAMPUNG

• Main Author: Bagus Prabaswara, Tri
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/47254
• Institution: Institut Teknologi Bandung

This research was conducted on the southeast slope of Ratai Volcano in Padang Cermin, Pesawaran Regency, Lampung of coordinates of 9,379,000-9,389,000 mN and 514,287–520,287 mE (UTM 48S zone) with an area of 60 km2. This research was conducted to understand the geological setting and geothermal system of Way Ratai. This research was conducted by geological mapping with a scale of 1:25.000 and geochemical study of geothermal manifestations fluids. Geomorphological unit of the research area consists of 6 units, i.e. Ratai Alluvial Plain Unit, Ratai Volcanic Cone Unit, Miwang Volcanic Remnant Hills Unit, Piabung Intrusion Hills Unit, Miwang Caldera Ridge Wall Unit, and Selapan Fault Zone Hills Unit. Stratigraphy of the research area consist of 7 units and 1 deposit, i.e Andesite Tuff - Pyroclastic Breccia Unit formed in Late Eocene - Middle Oligocene, Hornblende - Pyroxene Andesite Unit and Andesite Tuff - Pyroclastic Breccia Unit formed in Late Oligocene – Early Miocene, Andesite Intrusion Unit which intrudes Andesite Tuff - Pyroclastic Breccia Unit and older units in Middle Miocene, and Hornblende-Biotite Andesite Unit, Rhyolite Lapilli Tuff Unit, Pyroxene Andesite Unit, and Alluvial Deposit which were formed in Holocene. Geologic structures in the research are consists of seven N - S normal faults and eight NE - SW and NW - SE strike-slip faults which are influenced by the Sumatran Faults System. Geothermal manifestations consist of hotpool, geyser, spouting spring, and steaming ground, which occur in four locations, i.e. Margodadi, Cempaka, Way Panas, and Padang Cermin. Hotpools have temperatures of 70 – 92°C and partially - fully equilibration chloride type. The research area is interpreted to have one geothermal reservoir at fractured Rhyolite Tuff – Pyroclastic Breccia. The reservoir has temperature at about 200 – 220°C at a depth of ±500 meter and has a hypothetical resource of 64 MW. Heat sources is interpreted to be derived from the Quaternary intrusion which associate with Mount Ratai magmatism.