ABSTRACT:

The Kuroko-type seafloor massive sulfide deposits found in the western Pacific have been considered to have potentials for economic recovery of Au, Ag, Cu, Zn, and Pb. The technical and economic feasibility of mining is preliminary evaluated in this case study. The Sunrise Deposit of Myojin Knoll on Izu-Ogasawara Arc in the Japanese EEZ is selected as the target. It is concluded that commercial mining may have a chance, if a smaller production scale is applied to the development. Quantitative information necessary for a more accurate evaluation is discussed.

INTRODUCTION

The Kuroko-type seafloor massive sulfides (SMS) in the western Pacific have received much attention as sources for economic recovery of gold (Au), silver (Ag), copper (Cu), zinc (Zn), and lead (Pb). Since the end of the 1980s, the Kuroko-type SMS have been found in the back-arc basin and on oceanic island-arc areas. In the Okinawa Trough and on the Izu-Ogasawara Arc near Japan (Halbach et al., 1989; Kato, et al., 1989; Iizasa et al., 1999), in the Lau Basin and the North Fiji Basin near Fiji (Fouquet et al., 1991; Bendel et al., 1993), and in the East Manus Basin near Papua New Guinea (Kia and Lasark, 1999) typical representatives are found. They yield a higher concentration in Au and Ag than the SMS found in ocean ridge areas (Haymon and Kastner, 1981; Malahof, 1981; Hekinian et al., 1983; Rona et al., 1984; Hekinian and Bideau, 1985; Rona, 1985). Similar formation processes with the Kuroko ore deposits on-land in Japan have been expected and outlined by many researchers (Sillitoe, 1982; Scott, 1985; Halbach et al., 1989; Iizasa et al., 1999). The higher Au and Ag contents in one of the areas have increased the chances for profitable mining operation, which is under consideration by a private company (Malnic, 2001).

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