Deep-sea ferromanganese deposits and their resource potential for India

Abstract

Due to rapidly depleting land-based mineral resources, oceanic mineral deposits gain greater significance. Ferromanganese deposits on the seabed (nodules) and seamounts (crusts) known for the enrichment of several transition metals were discovered during pioneering expeditions of H. M. S. Challenger during 1872–76. The metal contents in these deposits show large variations from basin to basin. For India, the Cu and Ni (1% each) in nodules and Co (0.7%) and Pt (0.5 ppm) in seamount crusts recovered from the Indian Ocean are important. The hydrogenous crusts are not only important as economically valuable deposits of Co and Pt, but also are potential paleoceanographic repositories. Ferromanganese nodule exploration by India began in 1981 and concluded with recognition by the International Seabed Authority as a Pioneer Investor in 1987. This exploration license provides India with exclusive exploration rights over an area of 150,000 km2 (Pioneer Area) in the Central Indian Ocean. Nearly 700 million tonnes of nodule resources are estimated in this mine site, which are expected to contain around 14 million tonnes of combined Cu and Ni metals valued approximately over Rs. 1000 billion at current average market rate. Quantitative resource evaluation for seamount ferromanganese crusts is not yet available due to limited exploratory work. However, a promising area of Co–Pt enriched ferromanganese crust occurrence has been discovered on the Afanasiy-Nikitin Seamounts in the Eastern Equatorial Indian Ocean by NIO scientists, which contains Co upto 0.9 % and Pt upto 1 ppm.