Abstract
Cobalt rich manganese deposits (CRMD) are frequently discovered on tops and slopes of seamounts in the depths of 800-2,500 m in the equatorial regions of the Pacific Ocean. Because the wireline dredge bucket sampling is not effective to collect crust type samples and to detect buried deposits, the authors have developed a new type gravity corer with a stainless steel core barrel of large bore. A bottom contact camera is also installed as a trigger weight. In the practical uses, the size of the corer is 6 m of total length and 510 kg of total weight. The corer should be dropped freely form a height of 3-6 m above sea bottom. The authors carried out 21 trials on Seamount A, B and C. Results in the experiments were satisfactory. The bottom photos were useful for the recognition of sampling conditions. Maximum thickness of the sampled crust layers was 8 cm. And buried crusts were detected at three locations. In the paper, an outline of the results and some problems are described.
