Mineralogical Study of Hydrothermal Sulfide in the Okinawa Through

The study of hydrothermal sulfide in the Okinawa Through can help to uncover the hydrothermal mineralization characteristics of back-arc basins that are in the early expansion. In this study, the mineralogical characteristics of the sulfide from the midland and south of the Okinawa Through are carried out. First of all, using optical microscope and electron microscope to confirm the mineral composition, characteristics of crystal shape, syntagmatic relation and crystallization order. Analyze the chemical composition in virtue of electron probe. Then the crystallization order, hydrothermal mineralization stage and hydrothermal mineralization feature can be discussed on the base of abundant date. The result shows that the sulfide in the midland of the Okinawa Through is Zn-rich type consist of sphalerite, pyrite, chalcopyrite and a few of gelenite. Crystallization order is pyrite → sphalerite(chalcopyrite)→pyrite. There is only one mineralization stage: polymetallic sulfide stage. The sulfide in the south of the Okinawa Through is mainly composed of barite, a few of sphalerite, pyrite, chalcopyrite, gelenite and covellite are included. Crystallization order is barite→pyrite→sphalerite(chalcopyrite, gelenite) →covellite. The sulfide in the area can be divided into two mineralization stages, i.e. barite stage and polymetallic sulfide stage. The chemical study of the mineral shows that sulfide in the midland of Okinawa is the result of high-temperature mineralization and the wide range of mineral chemical composition reflect instability of the mineralizing setting.