Observations on Some Manganese Nodules from the Central Pacific

Abstract

Manganese nodules have been studied under the microscope with the use of reflected light and scanning electron microscope. Around the nucleus accretion of the diagenetically derived material is seen to take place giving rise to columnar or dendritic texture. Away from the nucleus textural variation and abrupt discontinuity in the nodule growth is observed indicating changes in depositional characteristics of ferromanganese oxides as the nodule grew. The intermingling of manganese oxides and silicate minerals, and sometimes iron oxides is common, generating discontinuities within the nodule texture. Scanning electron microscopic observations indicate that the material deposited on the surface is crystalline, non-crystalline, inorganic. organic or detrital in nature giving rise to different surface features such as botryoidal, consolidated compact layering or unconsolidated porous surface appearance.