| Abstract |
Hydrothermal alteration around the Okuaizu geothermal system was studied in the field and by microscope observation, X-ray diffraction and the calculation of saturation conditions for the alteration minerals based on previously reported analytical data of the geothermal fluid. Three stages of hydrothermal alteration were recognized : 1) middle Miocene submarine hydrothermal alteration, 2) late Miocene caldera-related hydrothemal alteration, and 3) hydrothermal alteration by the present Okuaizu geothermal system. |