Formation Mechanisms and Formation Environment of Seaflor Hydrothermal Ore Deposits

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The purposes of this Scientific Research Project are to solve the tectonic situation and depositional mechanism of colcanogenic massive sulfide ore deposits. The main objects of the ore deposits are one of the most representative Kuroko deposits of the Miocene age and the seafloor hydrothermal deposits of modern age. Descriptive geology on ores and related igneous rocks and up-to-date geochemical investigation are indispensable and the combination of both research procedures makes possible for the generalized earth scientific interpretation on ore genesis.In this study, the significance of geology and metal resources are examined first for the Hokuroku district in Akita Prefecture where the large scale Kuroko deposits were primarily developed. The second object is the presentatation for some volcano-stratigraphic points the area on the volcanogenic background of the Kuroko deposits.The siliceous mound in the Kosaka-Uchinotai deposit, one of the typical Kuroko deposits, are precisely in … More vestigated for the mode of occurrences. Geochemical characteristics are examined for ores from some Kuroko-and Besshi-type volcanogenic massive sulfide deposits, and the change of ore textures are studied from primary to successive diagenetic stages. The investigation of stable isotopic geology revelas that the carbonates from the Kosaka-Uwamuki deposit are formed by the reaction with hydrothermal fluid and carbonate in biogenic origin.Researches on seafloor hydrothermal deposits in modern age reveals that magmatic activities are important as the origin of hydrothermal fluids in the western Pacific region. Besides, seafloor sediments of the modern Kuroko-type deposits in the Okinawa Troughare investigated for the chemical and mineralogical compositions. In the seafloor hydrothermal deposits, the textures and structures of ores and the compositions of minirals are representing the generation circumstances, and those of Miocene Kuroko ores could be give some valuable hints for the consideration on primary features, preservation of ores and diagenetic processes. Less