In Japan considerable discrepancy exists between annual demand and domestic supply of base metals which are indispensable raw materials for industrial development. This gap has been filled with an importation of raw metals and ores. Recent trends of demand and supply and the changeable economic conditions have been exerting a serious influence on the metal-mining industry of Japan. The domestic resources of base metals, though their production ratios to demand are fairly low, have been and will be quite a stable source of supply.

Beside a long-continued subsidy policy for minor-scale mines, the national exploration program for domestic base-metal deposits was set up by the government, and put into operation in 1963 by the Metal Mining Agency of Japan under the auspices of the Ministry of International Trade and Industry. The program consists of three kinds of projects: regional geologic survey, detailed geologic exploration, and financial aid for direct exploration by companies. The principle of these projects is to promote prospecting for, and efficiently to discover, new ore deposits of copper, lead, and zinc in the districts which cover potential ore-bearing areas.

The regional geologic survey project has been and is now being carried out in the planned 48 districts where there are expected high potential resources of Kuroko, pyrometasomatic, cupriferous pyritic deposits, and ore veins of different geologic terranes. The geologic field survey, in combination with airborne magnetic survey, ground geophysical and geochemical explorations, and deep structural core drillings, is conducted by using a 1:10,000 topographic base map. The detailed geologic

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project is carried out in the target areas selected by the preceding survey in each district. Principal field work is exploratory core drilling spaced more or less regularly. Where necessary for geologic structures, ground and/or borehole geophysical prospecting and exploratory tunneling are integrated with drillings.

Geologic information and ore showings obtained by these projects are useful for interpretation and location of final target areas for advanced prospecting work of mining companies to which the government exploration fund is loaned.

During 10 years of operation of the national program, nearly 100 million tons of domestic new-ore reserves have been acquired, and operation of the program has contributed much to the progress in exploration methods and the concepts of explorationists.

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