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Iwato |
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Kyushu, Japan |
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Au
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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Iwato is a relatively small low sulphidation acid sulphate alteration associated gold deposit in the Nansatsu District of southern Kyushu, Japan, some 7 km east of the Kasuga gold deposit.
The deposit is developed within the 300 m thick Nansatsu Upper Volcanics, composed of 6.4 to 5.9 Ma pyroxene-hornblende andesite flows and pyroclastics. This unit has been strongly leached and variably silicified over a length of 2 km and widths of 200 to 400 m. The eastern 750 m of the siliceous zone contains all of the orebodies, which occur exclusively within the zone of silification and are defined by a 2 g/t Au cut-off. The larger of these bodies are around 100 to 200 m in diameter and persist to depths of 100 m. In detail the orebodies look like upward coalesced mushrooms.
The siliceous rock is composed of fine grained quartz, minor rutile and secondary quartz crystals with finely disseminated pyrite throughout. Other sulphides, sulphosalts and ore minerals are fine grained and disseminated and comprise native gold, electrum, argentite, pyrargyrite, canfieldite, chalcopyrite, bornite, chalcocite, enargite, native copper, sphalerite, galena, molybdenite, stannite, cassiterite, and native sulphur.
For detail, consult the reference(s) listed below.
The most recent source geological information used to prepare this decription was dated: 1993.
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.
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Hayashi T 2001 - Geology and gold exploration in the Nansatsu district, southern Kyushu, Japan: in Feebrey CA, Hayashi T, Taguchi S, 1994 Epithermal Gold Mineralization and Modern Analogues, Kyushu, Japan Society of Economic Geologists, Guidebook Series v. 34 pp 127-132
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Hedenquist J W, Matsuhisa Y, Izawa E, White N C, Giggenbach W F, Aoki M 1994 - Geology, geochemistry, and origin of high sulfidation Cu-Au mineralization in the Nansatsu District, Japan: in Econ. Geol. v 89 pp 1 - 30
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