Mineralogy of polymetallic nodules and associated sediments from the Central Indian Ocean Basin

Abstract

Todorokite is the dominant mineral phase in the nodules of the northern Central Indian Ocean Basin. These nodules are characterised by a rough surface texture, are relatively rich in Mn, Cu and Ni, and are associated with radiolarian sediments rich in montmorillonite, chlorite and illite. δ-MnO₂ is the dominant mineral phase in the nodules of the southern Central Indian Ocean Basin. These nodules have a smooth surface texture, are relatively rich in Fe and Co, and are associated with pelagic clay-sized sediments comprising keels of foraminifera, zeolite and the clay minerals chlorite and illite. The formation of these mineral phases and their composition in the nodules may have been controlled by the properties of associated sediments and the nucleus of the nodule does not influence the oxide layer mineralogy.