The Gold and Copper Ore Deposits of the Isobe Koyma Mine, Yamagata Prefecture
スポンサーリンク
概要
- 論文の詳細を見る
The Isobe Koyama mine is situated at about 30 kilometers northwest of Yamagata City and is producing copper and gold ores. The district is composed mainly of Miocene pyroclastic rocks and their lava flows of intermediate to acid type with some mudstone. The ore deposits of this mine consist of twelve bodies which occur in mudstone, muddy tuff, and green tuff. They are of an epithermal type and occuring veins, stockwork or as disseminating bodies. Native gold, chalcopyrite, sphalerite, pyrite, and galena, are the principal ore minerals, associated with such gangus minerals as quartz, kaolin, chlorite, barine and carbonate minerals.<BR>Native gold occurs in intimate association with quartz, kaolin, sphalerite and chlcopyrite. The ore comprising chalcopyrite, sphalerite chlorite and quartz is often so rich in gold that its gold tenor is more than one kilogram per ton. However, the grade of silver in the ore is always less than that of gold. The gold-silver ratio is a characteristic of the ore from the mine in comparison with that of the ores from the so-called epithermal gold-silver deposits in which the tenor of silver is usually ten or several ten times of that of gold.<BR>The vertical zoning of ore deposit is obvious, often divided into the following five zones from upper to lower : 1) quartz-kaolin zone, 2) quartz-kaolin-sphalerite zone, 3) sphalerite zone, 4) sphalerite-chalcopyrite zone and 5) chalcopyrite zone. The native gold occurs in the zones 1), 2), 3) and 4), especially richest in zone 4). In zone 5 ), the tenor of gold rapidly decreases to less than 2 grams, per ton. This zoning is also found in lateral derection. The central zone is the chalcopyrite zone, which may indicate a center of mineralizaton in this mine. Also, the fissures filled with ores seem to be mostly tension fractures, judging from their pattern.
- 資源地質学会の論文
資源地質学会 | 論文
- 資源情報 2008年度秋季講習会 西南北海道の中新世熱水活動と金属鉱化作用
- 飛騨帯の石灰岩類 -地質特性・構成鉱物・岩石組織とドロマイトの産状-
- 飛騨帯神岡鉱床周辺の変閃緑岩・変斑れい岩類
- 神岡鉱床周辺のいわゆる伊西ミグマタイトとスカルン鉱(杢地鉱)中の単斜輝石の組成変化
- 北部北上山地南東部, 大谷山鉱山北方地域に分布する層状マンガン鉱床の層位学的研究