K-Ar dating on the host rocks of the Taro mine, Iwate Prefecture

Ueda, Y.; Yamaoka, Kazuo; Onuki, Hitoshi

doi:10.2465/ganko1941.63.259

Cited by 2 publications

(1 citation statement)

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“…Radiolarian fossils in a clastic matrix of the accretionary complex near the Taro mine were identified to be of late Middle Jurassic age (ca. 160 Ma) (Matsuoka & Oji 1990), and sericite-quartz rocks from the Taro deposit were dated by the K-Ar method at 128 Ma (recalculated average age, Ueda et al 1970). Therefore, the time gap between the beginning of Cretaceous felsic magmatism and the cessation of Jurassic subduction processes in the Taro area was shorter than 32 Ma.…”

Section: Crustal Control On Redox State Of Granitoid Magmasmentioning

confidence: 99%

Crustal control on the redox state of granitoid magmas: tectonic implications from the granitoid and metallogenic provinces in the circum-Japan Sea Region

Sato¹,

Kovalenko²,

Romanovsky

et al. 2004

Earth and Environmental Science Transactions of the Royal Socie

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Felsic magmatism has occurred over a large region of East Asia since Jurassic times and has provided important mineral resources such as tin, tungsten, base metals and gold. The circum-Japan Sea region preserves various geological records of active continental margins, including Jurassic to Early Tertiary magmatic arcs and subduction zones and pre-Jurassic continental basements, which were separated by the opening of the Japan Sea during the Miocene. The felsic magmatism in this region shows a wide variation in terms of redox state and related mineralisation, encompassing east–west contrasts around the Pacific Ocean. A review of granitoids and associated ore deposits in this region indicates that the character of the crust, sedimentary versus igneous, is an essential factor to control the redox state, and a tectonic setting may be an additional factor in some cases.The reduced-type granitoids, characterised by tin mineralisation, were generated in carbonbearing sedimentary crust which was composed mainly of accretionary complex material and not influenced by previous magmatism. Involvement of sedimentary materials is corroborated by oxygen, sulphur and strontium isotope data. The oxidised-type granitoids, characterised by gold or molybdenum mineralisation, were generated in igneous crust which was depleted in reducing agents as a result of previous magmatism. Granitoid magmatism in a given area tends to become more oxidised with time.Jurassic accretionary complexes in East Asia are thought to have been largely displaced from the original place of accretion and stacked up against the northeastern margin in the Khingan and Sikhote–Alin Mountains. This region, dominated by sedimentary crust, was subsequently subjected to Cretaceous felsic magmatism and converted to a large province of reduced-type granitoids and tin–tungsten mineralisation. Diverse geodynamic processes, including the change of the arc-trench system, the creation and collapse of the back-arc basin and the collision of continents, may have prepared many favourable sites for the generation of reduced-type granitoids in northeast Asia. These processes may have resulted in a remarkable contrast with the Pacific margin of North America, where repeated arc magmatism during the Mesozoic formed granitoid batholiths of the oxidised-type.The granitoid types may also be controlled by the tectonic setting and mode of magma emplacement. In the northern Kitakami area of Northeast Japan, Early Cretaceous episodic magmatism occurred in a Jurassic accretionary complex, and formed the oxidised-type granitoids accompanied by submarine bimodal volcanism associated with kuroko mineralisation. Granitoids of fissure-filling type emplaced under extensional environments may be oxidised, irrespective of basement geology, because of insignificant crustal input.

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Section: Crustal Control On Redox State Of Granitoid Magmasmentioning

confidence: 99%

Crustal control on the redox state of granitoid magmas: tectonic implications from the granitoid and metallogenic provinces in the circum-Japan Sea Region

Sato¹,

Kovalenko²,

Romanovsky

et al. 2004

Earth and Environmental Science Transactions of the Royal Socie

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Metallogenesis in the Japanese island arc system

Ishihara¹

1978

JGS

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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.

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K-Ar dating on the host rocks of the Taro mine, Iwate Prefecture

Cited by 2 publications

References 1 publication

Crustal control on the redox state of granitoid magmas: tectonic implications from the granitoid and metallogenic provinces in the circum-Japan Sea Region

Crustal control on the redox state of granitoid magmas: tectonic implications from the granitoid and metallogenic provinces in the circum-Japan Sea Region

Metallogenesis in the Japanese island arc system

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