ORE MINERALS FROM KUROKO TYPE DEPOSIT OF TOYA-TAKARADA MINE, HOKKAIDO, JAPAN
Abstract
Toya-Takarada mine is Au- and Ag-rich Kuroko-type deposit located in Takarada, Toya-mura, southwest Hokkaido, Japan. The deposits were hosted in rhyolitic tuff and mudstone of Middle Miocene age. Ore samples of fine-grained black ore, vuggy black-yellow ore, granular vuggy black ore, quartz-sulfide ore and massive quartz-barite ore were studied to identify the ore minerals association in the Toya-Takarada mine. The ore minerals are dominated by sphalerite, galena, chalcopyrite and pyrite with fewer amounts of electrum, tetrahedrite-tennantite, and other sulfosalt minerals with secondary mineral of covellite.
The quantitative chemical analysis of ore minerals by EPMA indicated that FeS contents in sphalerite is low (0.3-1.2 mol.%) in all kinds of ore samples. Small grains of electrum as inclusions in pyrite are identified in vuggy black-yellow ore with Ag content around 32-33 atm %.
In general, the silver minerals in Kuroko-type deposits occurred mainly in the black and yellow ores zone dominantly composed of sphalerite, galena, pyrite, chalcopyrite and barite as a form of electrum and/or argentian tetrahedrite-tennantite series. Thus, the massive quartz-barite ore sample of Toya-Takarada mine are also contain some rare silver sulfosalt minerals such as proustite, Cu-rich pearceite, geocronite-jordanite and fizelyite. Those minerals were found together in association with sphalerite. It seems that sphalerite was crystallized first followed by proustite and Cu-rich pearceite, then geocronite-jordanite and fizelyite are crystallized later.
Sphalerites from quartz-sulfide ore of Toya-Takarada contain some fluid inclusions and measured homogenization temperatures are in the range of 164-247°C (av. 208°C) with salinity ranging from 1.9 to 4.7 wt.% NaClequiv. (av. 3.9 wt.% NaClequiv.). The mineral assemblage, iron content in sphalerite and silver content in electrum were indicated that sulfur fugacity was slightly higher during ore mineralization in Toya-Takarada mine.
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References
Marumo, K., 1985. Geological and mineralogical studies on alteration zones of Lake Toya area, Southwestern Hokkaido. Mining Geologi, 35, 5, p.331-344, in Japanese with English abstract.
Marumo, K. and Sawai, O., 1986. K-Ar ages of some vein-type and Kuroko-type deposits in southwestern Hokkaido, Japan. Mining Geologi, 36, 1, p.21-26, in Japanese with English abstract.
Roedder, E., 1984. Fluid Inclusions. Reviews in Mineralogy, 12, Mineralogical Society of America, Washington D. C, 644p.
Ohmoto, H., 1996. Formation of volcanogenic massive sulfide deposits: The Kuroko perspective. Ore Geology Reviews, 10, p.135-177.
Pisutha-Arnond, V. and Ohmoto, H., 1983. Thermal history, and chemical and isotopic compositions of the ore-forming fluids responsible for the Kuroko massive sulfide deposits in the Hokuroku district of Japan. International Journal of Economic Geology, Monograf, 5, p523-558.
Sato, T., 1977. Kuroko deposits: their geology, geochemistry and origin. Journal of Geological Society, Special Publications, 7, p153-161.
Sawai, O. and Itaya, T., 1993. K-Ar ages of Kuroko-type deposits in the Shakotan-Toya district, Southwest Hokkaido, Japan. International Journal of Resource Geology, 43, 3, p.165-172.
Scott, S. D. and Barnes, H. L., 1971. Sphalerite geothermometry and geobarometry. International Journal of Economic Geology, 66, p653-669.
Shikazono, N. and Shimizu, M., 1988. Electrum: chemical composition, mode of occurrence and depositional environment. University of Museum, University Tokyo Bulletin, 32, 81p.
Urabe, T. and Marumo, K., 1991. A new model for Kuroko-type deposits of Japan, Episodes, 14, 3, p246-251.
Yuningsih, E. T. and Matsueda, H., 2013. Silver sulfosalt minerals from the Toya-Takarada mine, Southwest Hokkaido, Japan. 63rd Annual Meeting of the Society of Resource Geology (abstract vol.), P-04, p.64.
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