Homogenization Temperature Measurements of Fluid Inclusions in Quartz and Anhydrite from the Hatchobaru Geothermal Field, Japan, and its Applications for Geothermal Development

Abstract

A homogenization temperature have been measured on the fluid inclusion in hydrothermal quartz and anhydrite from the Hatchobaru geothermal field, Kyushu, Japan. The obtained values are well in accordance with all three kinds of chemicals estimated temperatures, TSiO2, TNa/K and TNa-K-Ca. This fact and some other consideration suggest that the pressure correction of the homogenization temperature is unnecessary in the field. However, the uncorrected inclusion data are 130-170°C higher that the temperature measured in the course of drilling, and even 50-90°C higher than the temperature obtained 120 hours after stopping the mud circulation. In spite of such a large difference in temperature, the shape of the geothermal gradient given by the fluid inclusion data is fairly similar to that shown by the temperatures measured during drilling. then, it can be concluded that the fluid inclusion data are likely to indicate directly the present well temperature at a young active field as Hatchobaru, and that they will also service to know the thermal history of the fields that may already have cooled down to some extent.