Geomagnetic and geochemical observations in Mt. Pandan volcano hosted geothermal area, East Java, Indonesia

Abstract

This study was carried out to identify the temporal changes of the magnetic anomaly values and geochemical data at Mt. Pandan geothermal prospect area. The results from magnetic and geochemical analysis are used to determine the geothermal energy potential in study area. The residual magnetic anomaly in 2012 and 2018 was used to compare the temporal changes of geological structures in Mt. Pandan, while geochemical data was obtained in 2 locations (Jari and Banyukuning) of hot spring. The results of magnetic observation indicate the decreasing of residual magnetic anomaly values from 2012 to 2018 due to the tectonic activities which generate the secondary structures in study area. Geochemical analysis shows the decreasing of reservoir temperature from 139°C in 2012 and 130°C in 2018. The pH of water in 2 locations also changes from neutral to acid due to the presence of new fractures, lead the water to flow and pass through the surrounding rocks that can release silica, thus providing high concentrations in water and decrease the pH to acidic water. The electrical potential of Mt. Pandan geothermal energy prospect area is 0,2378 Mwe per second.