An Overview of Hydrothermal Alteration & Subsurface Geology in Dieng Geothermal Field, Central Java, Indonesia as Potential Area of Energy Efficiency 2020

Abstract

The Dieng geothermal field is located in central Java Island approximately about 80 kilometers northwest of the city of Yogyakarta surrounded by mountainous terrain. Dieng geothermal is a two-phase system which occurs in a caldera on the eastern margin of the Dieng volcanic complex. The Dieng field is the only geothermal area in Central Java that has been exploited and it is currently producing 60MW of electrical power. Manifestations of thermal activities are extensive in this field and consist of solfatara, fumaroles, hot springs, mud pools, phreatic explosion craters and altered grounds. This paper tries to describe the subsurface geology and hydrothermal alteration of the Dieng geothermal field. Geothermal field in Dieng comprised of three prospect areas namely, Sileri, Sikidang and Pakuwaja blocks. In this study, the results of hydrothermal alteration in Sikidang block can be grouped into four zones which include, from shallow to greater depths, smectite + cristobalite + kaolin zone, smectite + quartz + kaolin zone, interlayered illite/smectite + corrensite + epidote-clinozoisite zone and illite + chlorite + epidote-clinozoisite zone.