STUDI GEOLOGI DAN GEOKIMIA SEPANJANG ALIRAN SUNGAI BANYUPAHIT, KABUPATEN BONDOWOSO, JAWA TIMUR

• Main Author: Fauzan Al Ghozali, Muhammad
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/85714
• Institution: Institut Teknologi Bandung

The Banyupahit river flows 12 km in the Ijen caldera, Bondowoso regency, East Java. This research was carried out along the Banyupahit river, i.e. from the upstream area around the crater lake to the Blawan warm springs on the north wall of the Ijen caldera. The purpose of this research is to determine geological conditions and the presence of geothermal system along the Banyupahit river stream using water characteristic data. The methods used in the research were literature study, DEM (Digital Elevation Model) image analysis, geological mapping, direct measurement of the physical characteristics (i.e. temperature, pH and electrical conductivity) of waters, sampling and chemical analysis of cold and hot waters, and direct measurement of soil gas (i.e. CO2, H2S, and SO2). Analysis of the DEM images and field mapping indicate, that the lithology along the Banyupahit River is composed of 8 rock units. These units, from old to young, are the Blawan Pyroclastic Breccia, Limestone, Blawan Andesite Pyroxene, Plalangan Tuff, Mount Blau Andesite, Mount Papak Pyroclastic Breccia, Ijen Crater Andesite Pyroxene, and Mount Kukusan Pyroclastic Breccia units. The results of geological structure mapping and soil gas measurements indicate, that there are 3 geological structures trending southwest-northeast in the research area. Geothermal manifestations discharge as Ijen Crater Lake (41°C and pH <1) in the Banyupahit River upstream and Blawan Warm Spring (40-50°C and pH ~6,4) in the downstream. The Banyupahit river-water characteristics have temperature ranging between 21 and 24°C, pH ranging between 0.7 and 5 (become more neutral downstream), SO4 types, and rich in dissolved Cl, F, B, and SiO2. Those characteristics indicate, that along the Banyupahit river stream there are 3 geothermal systems, i.e. Kawah Ijen, Mount Blau, and Blawan systems.