Geochemistry and Origin of Ananai Stratiform Manganese Deposit in the Northern Chichibu Belt, Central Shikoku, Japan |
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| Authors: | Koichiro Fujinaga Tatsuo Nozaki Takazumi Nishiuchi Kiyoko Kuwahara Asuhiro Kato |
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| Institution: | Department of Resources and Environmental Engineering, Waseda University, 3–4-1 Okubo, Shinjuku-ku, Tokyo 169–8555, Japan [e-mail: ];Department of Geosystem Engineering, University of Tokyo, Hongo, Tokyo 113–8656, Japan;Department of Geosciences, Osaka City University, Sugimoto, Osaka 558–8585, Japan |
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| Abstract: | Abstract. Major and trace element contents are reported for Permian manganese ore and associated greenstone from the Ananai manganese deposit in the Northern Chichibu Belt, central Shikoku, Japan. The manganese deposit occurs between greenstone and red chert, or among red chert beds. Chemical compositions of manganese ore are characterized by enrichments in Mn, Ca, P, Co, Ni, Zn, Sr and Ba, and negative Ce and positive Eu anomalies relative to post-Archean average Australian Shale (PAAS). Geochemical features of the manganese ore are similar to those of modern submarine hydrother-mal manganese deposits from volcanic arc or hotspot setting. In addition, geochemical characteristics of the greenstone closely associated with the Ananai manganese deposit are analogous to those of with-in plate alkaline basalt (WPA). Consequently, the Ananai manganese deposit was most likely formed by hydrothermal activity related to hotspot volcanism in the Panthalassa Ocean during the Middle Permian. This is the first report documenting the terrestrially-exposed manganese deposit that was a submarine precipitate at hotspot. |
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| Keywords: | geochemistry manganese deposit greenstone hydrothermal hotspot within-plate alkaline basalt (WPA) accre-tionary complex |
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