People has regarded manganese nodules as an increasingly important source of valuable metals, including nickel, cobalt, copper, and manganese. From both technical and economical points of view, it is necessary for exploitation of manganese nodules to develop a suitable metallurgical process. It is difficult to recover nickel, copper, and cobalt contained in manganese nodules by any usual process, for such metals are present as oxides and oxyhydoroxides of the manganese and iron phases. Moreover, a French institute (IFREMER-GEMONOD) estimated that the cost of processing would account for more than half of the total cost of exploitation.
Since 1989 Metal Mining Agency of Japan (MMAJ) has performed studies on the recovery of iron, manganese, copper, cobalt, and nickel from manganese nodules under the umbrella of the Ministry of International Trade and Industry's Development of Deep Ocean Minerals Program. After investigating existing processes and comparing their respective performance with the same manganese nodules, the MMAJ developed a smelting and chlorine leaching process. The process is the combination of pyrometallurgical and hydrometallurgical treatments, which enables the efficient recovery of manganese, nickel, copper and cobalt.

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This paper reports the present state of Japanese national research program-Basic technology for ocean resources (Manganese nodule mining system). It includes the object of the program, base plan, approach methods, main frame of the past research and the list of experiments.
The program started in 1981 and is going to end in fiscal year of 1997, Final experiments are now being prepared.

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Investigation of hydrothermal are deposits on the East Pacific Rise (EPR) and onits off-axis volcanoes was carried out from 1985 to 1994 by the R/V Hakurei-maru No.2. More than one and a-half hundred hydrothermal activity sites were observed in the axial rift and on the off-axis volcanoes along the courses of the investigation. The hydrothermal sites were clustered between 12°47'N and 12°51'N, and between 11°20'N and 11°36'N. Though some percentages of the sites were concentrated on the top of ridge and in the spreading center of the rift, the off-axis volcanoes are considered as the most important area in the EPR from the view point of resource potential.

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Methane hydrate accumulations (deposits) are known to exist in the ocean sediment around Japan. It is estimated that the deposits, at today's natural gas consumption, would serve for the next 100 years if successfully extracted.
Methane hydrate is a solid material composed of methane and water molecules. At low temperature and high pressure, deep ocean conditions, water molecules form a “cage” which entrap the methane molecule. The methane hydrate can be dissociated by increasing the temperature and/or releasing the pressure.
This paper explains about researches and developments on the methane hydrate, molecular structures and properties of the hydrate, today's techniques on exploration, drilling and production of gas hydrates and the future research targets to realize the gas extraction from gas hydrates.

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Importance of cobalt-rich manganese deposits on the Pacific seamounts for a future cobalt resource has currently been well recognized. Though the geological information has been well recognized, no sufficient quantitative data of the deposits is available to aid design of the mining system.
Requirements of the quantitative data for the resource assessment are summarized.Methods for clarifying microtopographic distribution characteristics of the deposits and relationship between the microtopography and morphology are introduced. Large-diameter gravity corer and the results, such as the shallow-buried deposits and the multiple layering are summarized.
Degradation of mined crusts by their substrate is simulated. Resource potential considering the shallowburied deposits is examined.
Geotechnical characteristics of crusts, substrates, nodule, and sediments are studied. On the basis of the results, requirements for design of the mining system are discussed and the mining system and seafloor miner are overlooked. Future studies for the further understanding of the deposits are presented.

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Since 1975, Metal Mining Agency of Japan (MMAJ) has been making survey of mineral resources on the deep sea floor; manganese nodules, sea floor hydrothermal deposits and cobalt crusts. For more effective survey, Deep-sea Boring Machine System (DBMS) has been developed by MMAJ. DBMS has capability of 20m coring under 6, 000m depth of water. The size of DBMS is 3.5meters wide, 4.5meters long, 5.9 meters high and the weight is 5tons. DBMS has three legs and can keep up the right position up to 25 degree inclination. The subsurface hydro control includes proportional control over the bit weight, rotary rpm, and flushing water pressure. This report describes the outlines of DBMS.

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Human beings receive great benefits from ocean resources. Therefore, it is extremely important to assess the future effects of deep seabed mining on oceanic life and environmental conservation. Under the supervision of the Ministry of International Trade and Industry (MITI), MMAJ has been carried out environmental impact research for establishing the criteria for seabed mining in close collaboration with the National Oceanic and Atmospheric Administration of the United States (NOAA) from 1989.
In order to evaluate the impact of sediment discharges upon the benthic environment, the artificial resedimentation experiment was carried out in the Japanese pioneer area in 1994 (JET: Japan Deep Sea Impact Experiment). Moreover the observation on the condition of the sea floor after disturbance was continued in 1994 and 1995 by the Deep-sea Camera and sediment sampling. As a result of our experiment, it was suggested that the effects on oceanic life was observed.

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