Geology and hydrothermal alterations, and those correlations to physical properties obtained from gravity and resistivity measurements in the Mataloko geothermal field

Abstract

Several geoscientific studies were conducted to delineate the geothermal structure in the Mataloko geothermal field, central part of Flores, where geothermal energy is expected to be abundant and has not commercially developed yet. From the surface geologic features, various types of hydrothermal alteration zones are recognized in the areas including Mataloko, Wolo Bobo, Wolo Rhea and Gou fields. All these thermal fields are situated in a caldera-like structure (referred as "Bajawa Caldera") derived from gravity contours and geographical features. Thermal manifestations in Mataloko are distributed at the southeast margin of the Bajawa Caldera. The alteration mainly consisting of kaolinite and alunite extends in the NW-SE direction about 1,200 m long. A very low resistivity zone is extensively distributed coincidentally with those thermal manifestations and expected high temperature near the surface. Therefore, the subsurface around the site at southeast margin of the Bajawa Caldera, where the Wae Luja fault trending NW-SE intersects the N-S electrical and gravity lineaments, is expected to form a major geothermal reservoir.