ABSTRACT: Ferromanganese Nodule Occurrence in Relation to Local Variations of Seafloor Topography at the Western Margin of the Clarion-Clipperton Fracture Zones, North Pacific

Kap-sik Jeong, Jung-keuk Kang, Bong-Chool Suk, Mark L. Holmes

A cooperative research cruise between Korea Ocean Research and Development Institute and the U.S. Geological Survey occurred in the western C-C Fracture Zone ferromanganese nodule field in October 1989. The cruise was designed to find the best nodule exploitation area that has not as yet been claimed. Nodules and sediments were collected, and seabottom photographic and seismic surveys were carried out.

The ferromanganese nodules in this area (named K0DOS89) show a wide range of size, from smaller than 2 cm to more than 8 cm, as determined from 19 box cores and 37 free fall grabs. A comparison between nodule occurrence and the geologic environment reveals that the nodules are most abundant (from 5 to 26.8 kg/m²) on or near smooth hills and seamounts where the transparent layer is approximately 20 m thick. In these areas, the nodules are dominantly polynucleated, irregular, spheroidal, ellipsoidal, and in places discoidal. The top surface of the nodules is smooth while the bottom surface in contact with the sediment is rough with small botryoids. The nodules occurring on the tops of seamounts and hills have an entirely smooth surface regardless of the thickness of the trans arent layer.

On the abyssal plain, however, the nodules are scarce, mostly less than 2 kg/m² and the transparent sediment layer is variable in thickness from less than 10 m to 80 m. Nonetheless, the nodules are relatively abundant, about 5 kg/m², on the abyssal plain where the transparent sediment layer is about 20 m thick. These abyssal plain nodules are mostly spheroidal, ellipsoidal, and discoidal, with rough surfaces.

AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990