The origin of manganese nodules on the ocean floor

Abstract

ABSTRACT. Ferromanganese oxide minerals are among the most common components of large areas of the ocean floor. Their chemical and mineralogical peculiarities have long stimulated considerable interest. A brief review of various theories on the origin of these minerals is presented.Petrologic studies of some of the manganese nodules from the Pacific Ocean are reported, which show the existence in the nodules of a close association between ferro· manganese oxide phases and products of submarine volcanic effusions. Such an association ean be explained admitting some genetical connection between deep-sea lava effusions and the nodules. These results, together with observations on their distribution and chemistry, do not seem to agree with the hypothesis which assumes a slow accretion of the nodules, owing to chemical deposition of manganese and related elements from normal sea water. It is instead suggested that the majority of manganese nodules from the Pacific Ocean bottom are formed as a consequence of submarine volcanism. Strong interaction between hot lavas and sea water takes place in many submarine volcanic effusions. As a result large quantities of iron, manganese, and other elements are leached out of the lava. Manganese is partially separated from iron, and the bulk of it is then precipitated on the ocean floor in the vicinity of the effusion, thus forming the nodules. Some geochemical implications of this hypothesis are also discussed briefly.