Geologic Analysis of the Fushime Geothermal Field, Kyushu, Japan

Abstract

Fushime geothermal system is characterized by high temperature (over 300), existence of temperature inversion around the depth of 1,000 m and high salinity of geothermal fluid. Geothermal structure of this field was geologically interpreted with data acquired from sugace surveys and more than twenty wells. Two types of permeable zones are recognized in this field One is related to a dacite intrusion which is distributed in the center of the field. The other is related to fault ZQWS. The main reservoir exploited for tk power station occurs in a fractured zone developed around the dacite intrusion and permeable zones related to faults are utilized for reinjection. One of these fadt zones trending northwest to southeast is found to be associated with an andesite dik swarm related to the Takeyama volcano.