ABSTRACT:

The importance of cobalt-rich manganese crusts on the Pacific seamounts for future rare metal and rare earth element resources has currently been recognized. The thin layer-type deposit characteristics affect recovery efficiency of the deposit, degradation of the mined ore, and the economy of the mining venture, when the microtopographic undulation is severe. Assuming some ideal distributions of cobalt-rich manganese crusts with respect to microtopography, the recovery efficiency, degradation, and economy under existing mining technologies are examined. The important role of utilization of rare metals and rare earth elements in the crusts for the better economy of the mining is introduced.

INTRODUCTION

Cobalt-rich manganese crusts on seamounts have received attention as potential sources for strategic metals such as Co, Ni, Cu, and Mn, due to their vast distribution and higher cobalt concentration than manganese nodules (Cronan, 1980; Halbach, 1982; Manheim, 1986). The geological information on potential areas was reported (Cronan, 1984; Clark et al., 1984; Misawa et al., 1987; Pichocki and Hoffert, 1987). A systematic feasibility study for the mining was published (Hawaii DPED, 1987). From the end of 1980s, Japan has undertaken many survey cruises for cobalt-rich manganese crusts in and around the Mid-Pacific Mountains (Yamazaki et al., 1994; Usui and Someya, 1997; Yamazaki and Sharma, 1998; MMAJ, 2001). Some key technological studies for the mining and the processing also have been studied (Aso et.al, 1992; Yamazaki et al., 1995; Rokukawa, 1995; Yamazaki et al., 1996; DOMA 1998). Because the importance of cobalt-rich manganese crusts for future rare metal and rare earth element resources has currently been recognized, the effects of microtopography on recovery efficiency of the crusts and degradation of the mined ore are examined here in this study under ideal deposit and assumed mining conditions. The economy of the mining venture is also evaluated.

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