Internal texture and chemical composition of manganese micronodules in deep sea sediments from the Central Pacific Basin

Abstract

The abundance, mineralogy, internal texture and chemical composition of manganese micronodules in deep sea sediments from six areas in the Central Pacific Basin were studied by means of ore microscopy, X-ray diffraction and EPMA.
(1) Abundance of micronodules ranging from 50 to 500 mesh sieve tends to decrease with increasing grain size. Micronodules were not found in the size fraction greater than 50 mesh sieve.
(2) Constituent ferromanganese minerals of micronodules may be 10 Å-manganate and δ-MnO₂.
(3) Based on internal texture of micronodules, they are classified into two types; Type-I with dendritic or cuspate textures and Type-II with stratified or columnar textures.
(4) Type-I micronodules are characterized by high contents of Mn, Ni and Cu, while Type-II are characteriz-ed by high contents of Fe and Si.
(5) Type-I and Type-II micronodules are resemble to r-type and s-type of manganese nodules with respect to internal texture, chemical composition, constituent minerals, and probably depositional environments.