滋賀県野洲花崗岩体?熱水変質閃長岩中の磁鉄鉱

摘要

Magnetite was found from hydrothermally altered granite, or hydrothermal syenite, in the Yasu Granite pluton, Shiga Prefecture, central Japan. The hydrothermal syenite consists of several types of rock facies. Hydrothermal secondary silicate minerals in the syenite are dominantly of potassium feldspar and albite, and subordinately of quartz and an assemblage of chlorite, hydrobiotite and biotite. The syenite is associated with mineralization forming sulfide minerals such as sphalerite and pyrite. The magnetite was found in the hydrothermal syenite facies of dark green color. This report describes the occurrence, chemical compositions and XRD data of the magnetite, which was found for the first time at least in Japan from hydrothermal syenites.