Ferromanganese oxides from Mid-Indian Ridge, seamounts and abyssal plains from the Indian Ocean

Abstract

Mineralogical and chemical investigations show that todorokite is the only Mn mineral in the Mid-Indian Ridge ferromanganese, coatings, delta <i>δ</i> MnO₂ in the seamount crusts, and well crystallised todorokite and minor amounts of delta <i>δ</i> MnO₂ in the abyssal nodules. Enrichment of Mn, Cu, Ni and Mn/Fe ratio is in the sequence, abyssal nodules > seamount crusts > Mid-Indian Ridge samples. Fe is highest in the Mid-Indian Ridge samples followed by seamount crusts and abyssal nodules. Co is enriched (up to 0.47 %) in the seamount crusts. The ferromanganese oxides from the Mid-Indian Ridge, seamount crusts and abyssal nodules appear to be of hydrothermal, hydrogenous and early-diagenetic in origin respectively.