Analysis of Mn nodules from cruise GH72-2

The GH72-2 shipborne survey was carried out in the northwest Pacific during 31 days under the 'Basic investigations for exploration of deep sea mineral resources' program. The sediments encountered could be classified as follows: 1) Most of the brown clays occur on the abyssal plain of the basins at depth over 4500m. 2) Calcareous oozes are predominant at the top, slope and foot of seamounts and guyots. 3) Terrigeneous sediments are distributed near islands. The concentrated zone of ferromanganese nodules was located in the Magellan seamounts area. However, the metal contents in Mn, Cu, Ni and Co for these nodules are relatively poor, and these ferromanganese deposits occur at a depth over 5000m. It is interesting to note that the shape of the nodules is sometimes nearly spherical, and that the chemical composition of the nodules is characterized by the low ratio Mn/Fe and Co/Ni.

Annotated record of the detailed examination of Mn deposits from R/V Bosei Maru Cruise GH72-2 stations

In 1972, the five years program 'Basic investigations for exploration of deep sea mineral resources' was laid out by the Agency of Industrial Science and Technology, Ministry of International Trade and Industry. The Geological Survey of Japan and the National Research Institute of Pollution and Resources undertook the first survey project. The survey team consisted of four geologists and a surveyor of the Geological Survey of Japan, and a mechanical, engineer and four mining engineers of National Research Institute of Polution and Resources. The survey started on November 11 using the "Bosei Maru" survey vessel (1100 tons) chartered from Tokai University. The cruise departed from Shimizu harbor to the Ponape and Guam islands, and terminated at the harbor of departure on December 11. The surveyed area was mainly covered the Mariana basin and the Magellan seamounts, and fifteen bottom samples were collected during the cruise. Ferromanganese nodules were obtained at several stations at a depth over 5000m.