著者

大泉 製次

出版者

Japan Association of Mineralogical Sciences

雑誌

岩石鉱物鉱床学会誌 (ISSN:00214825)

巻号頁・発行日

vol.58, no.1, pp.31-38, 1967-07-05 (Released:2008-08-07)

参考文献数

10

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Shirataka Mine is situated between On Mountains and Dewa Hills in the southern part of Central Yamagata Prefecture. The Mine Area is underlain by Miocene strata, i.e.: 1) Yoshinogawa formation, 2) Motozawagawa formation, 3) Shimoyama formation, 4) Ose tuffaceous sandstone member and 5) Sugiyama formation. Shimoyama formation is interfingered with Yoshinogawa and Motozawagawa formations. Yoshinogawa formation is correlated to the Daijima and Nishikurosawa formations, while Motozawagawa formation is correlated to the Onnagawa formation. In the western part of the region, hornblende-biotite granodiorite basement rocks are exposed. In the northeastern part, Quaternary volcanics in the Shirataka Mountain, andesite flows and pyroclastics are found. The ore deposit is of the network type, and it is strongly controlled by geologic structures. Fractured zone generally trend N30E. Ores shoots follow the same trend, but, they dip more steeply. At the upper reaches of the Kaaehorizawa River, kaolinization and pyritization with accompanying mineralization is pronounced. This report presents the studies made on the relationship between ore deposition and structural control of volcanism inherent to the Zao-Shirataka volcanic structural line.