XXXII.—On the Manganese Oxides and Manganese Nodules in Marine Deposits

Abstract

During the “Challenger” Deep-Sea Exploring Expedition a great many peculiar-looking manganese nodules or concretions were dredged from the floor of the ocean at great depths, chiefly in the Red Clay areas of the Pacific, but also in less abundance in the Red Clays of the Atlantic. In the other varieties of Deep-Sea deposits these nodules were much less abundant than in the Red Clays.In still more recent soundings, both American and British ships have discovered in many regions of the Pacific and Indian Oceans a dark-brown coloured deposit containing a large amount of manganese dioxide, similar in character to the Red Clays from which the “Challenger” procured the largest hauls of manganese nodules. There is then every reason for supposing that manganese deposits and nodules are very widely distributed over the ocean's bed, especially in deep water at great distances from land. It was only occasionally that manganese nodules were present in any abundance in a Globigerina Ooze, and in these exceptional instances there was always much volcanic debris associated with the deposit. In the Blue Muds surrounding continental shores manganese nodules were rarely observed; still, on some rocks and boulders dredged from terrigenous deposits, a coating of manganese dioxide was observed on that portion of the stone which had projected above the surface of the mud.