Significant geologic and metallogenic features of polymetallic vein deposits in Japan
published: Jan 1, 1991
ArtNo. ESP136000304002, Price: 19.00 €
Significant geologic and metallogenic features of subvolcanic Sn-W-bearing polymetallic vein deposits, together with those of plutonic W-Sn-Cu vein deposits in Japan are reviewed and discussed on the order of metallogenic province, ore field, and ore body. (1) As for the inner zone of southwest Japan, the petrographic provinces, San'yo and San'in belts, and the metallogenic provinces, tungsten and molybdenum provinces, are established. The tungsten and molybdenum provinces are in accord with the San'yo and San'in belts respectively. The plutonic W-Sn-Cu veins, those of Otani and Kaneuchi mines, are genetically related to late Cretaceous ilmenite-series granitoid in San'yo belt. The vein deposits of Ikuno and Akenobe mines, representative large-scale subvolcanic Sn-W-bearing polymetallic (Cu, Zn, Pb, Bi) vein deposits in Japan, occur in the inner zone of southwest Japan, and are genetically chiefly related to dike rocks of Paleogene age. The geologic setting and mineralogy of subvolcanic Sn-W-bearing polymetallic vein deposits of Ikuno and Akenobe mines are quite different from those of the plutonic W-Sn-Cu vein deposits. The K-Ar ages (63.0 to 65.6 Ma, MMAJ, 1983) of the copper ore from subvolcanic Sn-W-bearing polymetallic veins of Ikuno mine are definitely younger than those (93 Ma) of the plutonic W-Sn-Cu veins of Otani and Kaneuchi mines. The Delta 34S values of sulfide minerals from subvolcanic Sn W-bearing polymetallic veins of Ikuno and Akenobe mines are in the range from -3.5 to + 1.2 %0, while those of plutonic W-Sn-Cu veins are characterized by larger negative values ranging from -10.5 to -7.1 %0 (Miyoshi et al., 1988). (2) A common feature of both subvolcanic and plutonic polymetallic vein deposits in Japan is the fracturing and reopening event during process of mineralization. A marked polyascendent hypogene zoning developed in the subvolcanic Sn-W-bearing polymetallic vein deposits on the order of ore field and ore body is structurally controlled by the intersecting structures of faults, fractures, dikes and other structural elements. (3) The subvolcanic Sn-bearing polymetallic (Cu, Zn, Pb, As, Bi) vein deposits of the Ashio mine, the largest copper mine in Japan, occur in the so-called "Green Tuff" region in the inner zone of northeast Japan and are hosted by rhyolitic volcanics of Miocene age. The volcanic vent in depth seems to have controlled the localization of emplacement of Sn-bearing polymetallic deposits on the order of ore field and larger units.