Evaluation of geothermal resource by melt inclusion analysis : Example from Shirasawa Caldera, Miyagi prefecture

Abstract

In this study, the purpose is to establish a geothermal resource evaluation method using the magma temperature and pressure by the analysis of melt inclusions. Crystallization depth estimated by the norm composition of the melt inclusions and the eutectic phase diagram of Qtz-Ab-Or is suggested to be 1.6~10km. The trace element concentration of inclusion in a single crystal shows correlation with the crystallization depth, indicating differentiation during ascent. Major crystallization pressure is 150~250 MPa, and presence of huge magma chamber was suggested at 5~8km. The current magma chamber estimated from seismic exploration is deeper depth, thus it has deepened for 7My.