Metallogenesis in the Japanese island arc system

Abstract

Ore deposits in the Mesozoic and Cenozoic orogenic belts of the Japanese island arc system consist essentially of stratabound, vein and skarn types. The stratabound base-metal deposits, which are the main source of copper, are divided into the lead-free, chalcopyrite-pyrite, Besshi-type, which occur mainly in glaucophane schists (metamorphosed basaltic pyro-clastic rocks) of the Sanbagawa belt, and the lead-bearing, polymetallic, massive sulphide, Kuroko-type, associated with rhyolite extrusion. Both types are regarded as having been formed syngenetically in a submarine environment. Vein-type deposits are widely distributed and economically the most important for metals, containing more than 50 per cent of the available tin, tungsten, molybdenum, gold, silver and manganese. The ore deposits are genetically related to either 'geosynclinal basalt' or an andesite-dacite-rhyolite and plutonic association of island arc magmatism. Special attention is given to deposits of plutonic affinity. Most Japanese plutons are granitoids. Ore deposits associated with Cretaceous-Palaeogene granitoids in southwest Japan constitute two metallogenic provinces, characterised by W-Sn-Cu and Mo-Pb-Zn veins and skarns. Northeast Japan shows a similar, but reversed, zoning, with no tin. Miocene granitoids in southwest Japan are accompanied by tin and some copper mineralization. The Japanese granitoids consist of approximately equal proportions of magnetite-series and ilmenite-series rocks. The magnetite-series is thought to be derived from a parental magma generated from mafic igneous rocks of the upper mantle—lower crust and related to major subduction. The ilmenite-series, with which tin deposits may be associated, is ascribed to magma originating in the lower crust from sedimentary, metamorphic and granitoid rocks. These magma types appear to be the most important factors in producing the various metallogenic provinces in Japan.

K-Ar ages of base and precious metal mineralization in the Tungsten Province, Southwest Japan.

“…In conclusion, the previous results by SHIBATA and ISHIHARA (1974), YAMAOKA and UEDA (1974), ISHIHARA (1978) and newly obtained data show that in the W Province, the base metal mineralization such as associated with Cu occurred later than the major tungsten mineralization, but somewhat earlier than the precious metal mineralization and the base and precious metal mineralization in and around the Ikuno-Akenobe Province.…”

Manganese formations in the accretionary belts of Japan: Implications for subduction–accretion process in an active convergent margin

“…These deposits were considered to have formed syngenetically in relation to submarine volcanism in geosynclinal belts (e.g. Tatsumi et al, 1970;Watanabe et al, 1970a;Ishihara, 1978). However, microbiostratigraphic and tectonic studies (Isozaki et al, 1990;Isozaki and Maruyama, 1991) suggested that the major deposits associated with chert and basalt are of oceanic origin and are allochthonous to the continental margin environment.…”

Mid–Cretaceous Episodic Magmatism and Tin Mineralization in Khingan‐Okhotsk Volcano–Plutonic Belt, Far East Russia

“…The Sn-associated reduced-type felsic magmatism is thought to have been caused by the subduction of the hot back arc basin and the significant crustal melting (Fig. 8) in a similar manner to the Middle Miocene Sn-associated reduced-type granitoid magmatism in the Cretaceous to Paleogene Shimanto accretionary zone of Southwest Japan (e.g., Ishihara, 1978;Ishihara et al, 1992). The Middle Miocene magmatism could have been caused by the interaction of Southwest Japan arc with the very young, and presumably hot, Shikoku Basin due to the opening of Sea of Japan (e.g., Kobayashi and Sato, 1979;Takahashi, 1986;Furukawa and Tatsumi, 1999).…”