Geochemical Exploration of Geothermal Manifestations: Study Case of Bajawa Volcanic Complex, Flores Island, East Nusa Tenggara Province

Abstract

Currently Indonesia occupy third place in the World demand of geothermal energy with using of 1375 Mwe (Mega Watt electrical). Energy utilization is only used around 4 – 5 % of geothermal energy capacity owned by Indonesia. Surely, this fact encourages many researcher to develop geothermal field with multidisciplinary sciences. One of potential geothermal areas is Nage geothermal field located in Bajawa City, Ngada District, East Nusa Tenggara Province. Four hot springs and fumarole were founded in the area. The Exploration using geochemical analysis in the form of descriptive method and analysis of geothermal fluid data. Based on regional geology, Bajawa volcanic complex composed of three periods of volcanic, first is old volcanic that formed Nage Caldera and Old Inierie volcanoes, then formed Bajawa Cinder Cone unit with North – South and North East – Southwest alignment, this alignment surely controlled as a linear eruptions. And the last is Inierie unit, this unit is active stratovolcano. The results of data obtained from one fumarole and four hot springs sample were taken from Wolo puti fumarole, Bena hotspring, Keli hotspring, Nage I hotspring and Nage II hotspring. Based on the relationship of chemical element ratio and plotting of triangular Giggenbach diagram shows that Keli and Bena hot springs are sulphate type, this hotspring controlled by Wolo puti fumarole as upflow of the geothermal system then Keli and Bena hot springs are in the outflow zone, which has mixed by meteoric water. Nage I and Nage II hot springs are chloride type, which has different geothermal system from Keli and Bena hot springs. Based on the geothermometer calculation of the Na-K-Mg diagram, the temperature of reservoir is 220° - 340° C, which is included of high enthalpy geothermal system.