Honshu, Japan

Main commodities: Cu Zn FeS2
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The Takara kuroko type Cu-Zn-pyrite orebodies are hosted by Miocene volcanics in the Misaka Mountain Range, Yamanashi Prefecture, Honshu, Japan, some 90 km west of Tokyo.

The Takara deposit lies within Miocene green tuff and shale in a structurally complex part of Japan, some 550 km south of the Hokuroko Basin which hosts most of the largest of the Kuroko type deposits within middle Miocene volcanics.

For background information on the geology, setting and ore types of the Hokuroko Basin see the Hokuroko Basin - Kuroko Deposits record.

The host sequence was deposited on a basement of Cretaceous to Paleogene age and comprises a thick pile of Neogene volcano-sedimentary rocks which were overlain in turn by Quaternary volcanics.   In the Takara mine area the hosts consist of Miocene andesitic lavas, tuffs and 200 m of intermediate to acid green tuffs.   Kuroko type mineralisation is within the green tuffs and associated shale.   In the vicinity of the mine there are intercalated dark green, fine grained, pyroxene-andesitic lavas.

There are four orebodies at Takara, namely the:
Main Orebody - a north dipping cylindrical body with dimensions of 85x55 m in plan and extending down dip for 200 m at 70 to 80°.   It consists of Kieko, Oko and Kuroko ores, mainly Oko with pyrite, sphalerite, galena and minor chalcopyrite with bornite and secondary chalcocite in a clay alteration.
East Orebody - approximately 100 m east of the main orebody, occurring as a 50x15 m lens extending down dip for 130 m at around 60° N, comprising Kuroko, Oko, Keiko and Sekkoko ores.
West Orebody - located 400 m west of the Main orebody as a bedded 5 to 10 m thick lens with an 80 m strike, composed minly of pyrite (20%) and clay minerals.
North Orebody - a vein type, fracture filling occurrence with brecciated ores in a fault between black shale and green tuff, with mainly pyrite and sphalerite and minor chalcopyrite located some 200 m north of the Main orebody.

Production from1903 to 1962 totalled:
    1.56 Mt of ore for 2250 tonnes of Cu, 4985 tonnes of Zn and 0.6 Mt of pyrite.

For detail consult the reference(s) listed below.

The most recent source geological information used to prepare this summary was dated: 1975.    
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.

  References & Additional Information
   Selected References:
Maruyama S, Mori H  1974 - Geology of the Takara Mine, Yamanashi Prefecture: in Ishihara S (Ed.), 1974 Geology of Kuroko Deposits The Society of Mining Geologists of Japan   Mining Geology Special Issue 6 pp 209-211

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