Abstract :

Since 1975, Metal Mining Agency of Japan (MMAJ) has been surveyed of mineral resources on deep-sea floor: manganese nodules (1975–1996), submarine hydrothermal deposits (1985-) and cobalt-rich manganese crust deposit (1987-). In 1999, the MMAJ has been conducting drilling surveys at the Suiyo seamount in the IzuOgasawara Arc, Japan using the Deep-sea Boring Mashine System (BMS) which was developed by the MMAJ. The seamount is located about 24 km northwest of Chichi Island and is characterized by submarine hydrothermal polymetallic mineralization of the back-arc basin type. Three of five drill holes intersected polymetallic mineralized parts enriched in Cu and Zn and characterized by pyrite, chalcopyrite and zincblende, making it the first recovery of a modern hydrothermal deposit. This paper describes the outline of the current activities on the exploration of submarine hydrothermal deposits in the Suiyo seamount.

Introduction

The Metal Mining Agency of Japan (MMAJ) has been conducting surveys of submarine hydrothermal deposits since 1985. The exploration of submarine hydrothermal deposits must define the distribution of potential mineral resources in the vertical section and the grades of the deposits. To meet such a demand, in 1996, the MMAJ developed the Boring Mashine System (BMS) for deep-sea exploration which has a capacity of 20m core drilling at a depth of 6000m as shown in Fig. 1 (Matsumoto and Sarata,1996; Sarata et al., 1999). During the period of twenty days from December 8 to 27, 1999, using the BMS, an exploration of submarine hydrothermal deposit was conducted at the Suiyo seamount in the Izu-Ogasawara Arc. As the result, three of five drill holes intersected polymetallic mineralized parts enriched in Cu and Zn and characterized by pyrite, chalcopyrite and zincblende, making it the first recovery of a modern hydrothermal deposit at an oceanic island-arc (Sarata and Matsumoto,2000).

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