Greenfield Exploration of Hidden Magmatically Driven Geothermal Systems in Active Subduction Zones: Case Study Lamongan (Eastern Java, Indonesia)

Abstract

Magmatic settings involving active volcanism are potential locations for economic geothermal systems due to high temperature and steam pressure. Indonesia, located along active plate margins, hosts numerous areas of active volcanism and, therefore, belongs to the regions with greatest geothermal potential worldwide. However, tropical conditions and steep terrain reduce the spectrum of applicable exploration methods, in particular in remote areas. As an example to conceptualize perspective geothermal systems in those settings, results of a case study from the Lamongan volcanic field in East Java are presented. The study integrates field-based data on the regional structural geology, composition and stable-isotope patterns of thermal waters, and the mineralogy and geochemistry of volcanic rocks. Results would indicate infiltration of seawater through faults from the 20 km nearby coast along a NW-SE striking lineament identified by satellite imagery. The possible heat source based on recent geophysical surveys (Chaussard and Amelung, 2012) and our assumptions could be located at quite shallow depth.