Seamount and Cobalt-Platinum rich Fe-Mn Crust Resources in the Indian Ocean

摘要

Ferromaganese encrustations of hydrogeneous types have beenrnknown together with manganese nodule for their Ni-Cu metalrncontent. However, ferromanganese crust formed on ancientrnvolcanoes and have a chemistry quite different than thosernassociated with nodules. They have a high level of cobalt (~1.5%)rnand platinum (~1g/ton) in addition to a series of other elementsrnsuch as, cerium and titanium, which are of strategic significance inrnterms of “new metals”. Based on the criteria of exploration,rnpotential areas within the Indian ocean most ideally suitable for therndevelopment of the crust have been suggested.rnThe substrata rocks over which the cobalt rich crust have beenrnformed are volcanic breccias, hydroclastic basalts, phosphorite,rnlimestone, volcanoclastic sandstone, mudstone and chert.rnSeveral areas in the Indian ocean have a geological environmentrnwhich is favourable for the formation of thick ferromanganeserncrusts. These areas could be grouped into:rna. Old seamounts (More than 20 million years of age).rnb. Areas with a well developed oxygen minimum zone.rnc. Areas of strong, oxygen-rich, near-bottom currents, andrnd. Areas where seamount flanks are ideally between 500 to 1500mrnwater depth, in the equatorial zone (between 15-20° latituderneach side of the equator).rnIn such exploration campaign, one has torna. Avoid areas with atolls and coral reefs.rnb. Avoid areas near continents.rnc. Select area with flat top of the seamounts for betterrnpicking/sampling and eventual detailed exploration to miningrnprospects.rnd. Select areas with an average crust thickness of more than 4 cmrnand a cobalt grade of more than 0.8%.rne. Select microphotographic areas with the wide-spreadrnoccurrence of crust, and eliminate areas of slumps, talusrndeposits and sediment cover.rnBased on these criteria, in the Indian ocean, areas close to Indiarnworth considering for exploration are (1). Lakshadweep islands,rnonly seamounts without reefs, (2) Southern tip of Kerala state, (3)rnSeamounts between 93°-96°E and 10°-13°N. The area could bernextended to the south of the Ninety-East Ridge, as well as otherrnpotential areas well within the EEZ of India.