Chemistry and Growth History of Central Pacific Mn-Crusts and their Economic Importance

Hydrogenetic ferromanganese deposits from seamount areas of the Central Pacific Basin should be seriously evaluated as sites for economic development. MIDPAC exploration cruises in 1981 and 1984 have shown that crust thickness varies between 0.5 and 10 cm and that best qualities of metals of primary interest such as Mn (average 26%), Co (average 0.9%) and Ni (average 0.55%)and trace concentrations in Pt (average 0.5 ppm) are found between depths of 1,000 and 2,000 meters. Two generations of crust growth occur: an apatite phase is present either in an impregnated form in the older crust generation, or as discrete apatite layer in the older crust generation, and in between the older and younger generations. 10Be dating helps better understanding of the origin and growth history of the Mn-crusts.