Hydrothermal alteration and mineralogy characterization at the Lake-Assal and the Hatchobaru geothermal fields

Abstract

Twenty-one samples were collected from Lake-Assal and Otake-Hatchobaru fields. The samples were analysed by petrography and XRD to identify clay minerals, and XRF to identify to chemical constituents. In Addition, thin Section observation of two samples from Assal and one sample Otake-Hatchobaru. Results indicate that plagioclase, forsterite and fayalite, are the main primary minerals while chl/Sme, Illite/sme and hematite are the prominent secondary alterations. Advanced argilic surface alterations composed of alunite, cristobalite, and kaolin were also noted to have developed due to the alteration by steam-heated waters.