The Neutral High-Cl Thermal Springs of Java, Indonesia

Abstract

A limited number of neutral high-Cl thermal springs are found on Java, Indonesia. Only one of them appears related to a known exploitable deep neutral-Cl geothermal reservoir and that is the Sarimaya springs at Awibengkok. Only two of the other groups of springs appear related to undrilled, possibly exploitable systems. One may be sourced from the Sunda caldera just north of Bandung. Springs at Ngebel may also be related to a high temperature system, but with a sedimentary reservoir that may limit exploitation. Springs at Cilayu and Ungaran appear to be neutralised outflows from magmatic vapour cored systems that may have limited associated exploitable resources. Springs at Kromong, Sangkan Hurup and Lawu do not fit into the above categories. They are interpreted to be from systems in which the weight of the volcanic pile has deformed underlying sediments to create permeability to allow deep circulation of meteoric waters that become saline upon being heated under the regional temperature gradient of Java and thus are unlikely to be associated with high temperature resources. Understanding this and the resulting spring chemistry, provides an additional tool for assessing geothermal development potential.