北海道虻田鉱山産豆状硫化鉄鉱鉱石について.pdf

岩石鉱物鉱床学会誌 69, 225-232, 1974 北海道虻田鉱山産豆状硫化鉄鉱鉱石について* PISOLITIC IRON SULPHIDE ORE FROM ABUTA MINE, HOKKAIDO 五 十 嵐 昭 明(TERUAKI IGARASHI)** The mode of occurrence of pisolitic pyrite ores and the internal heterogeneities revealed by chemical etching of pyrite crystals consisting of the pisolite as well as of iron sulphide ores from the Abuta mine were studied. The pisolitic ore is generally composed of a small number of relatively large pyrite crystals and a large number of minute crystals of more or less uniform size. This indicates the conditions under which numerous nuclei of pyrite were formed but not enough growth took place. Such conditions may be realized when pyrite ore is formed from the solution with steep temperature gradient. Under low pressure, hot water lake such as Oyunuma of Noboribetsu spa may be presumed. In contrast, the internal structures of pyrite crystals consisting of ordinary ores occurring at some distance from the pisolitic ore are conjectured to have formed under higher pressure and higher temperature conditions than the pisolitic ores. した硫黄,硫 化鉄鉱,褐 鉄鉱鉱床と沈殿褐鉄鉱鉱床から 1.は し が き なる。それらの相互関係を第1図 に示す。すなわち,北 筆者は,長 年にわたり新第三紀後期～第四紀鉱化作用 方の丘陵地から南方の海岸 にかけて,第3硫 化鉄鉱鉱 の研究に従事してきたが, 1970年 秋,虻 田鉱山の硫化鉄床,第2硫 化鉄鉱鉱床,第1硫 化鉄鉱鉱床が,ほ ぼ南北 鉱鉱床中に豆状硫化鉄鉱鉱石が見出されたとの新情報に 方向に配列し,沈 殿褐鉄鉱鉱床は第1硫 化鉄鉱鉱床の上 興味をもち,た だちに現地調査をおこない,豆 状鉱石の 位に位置する。第1硫 化鉄鉱鉱床の下部は次第に遊離硫 黄の量が増加し,硫 黄鉱床に移化する。 産状を明らかにした(五 十嵐ほか, 1972a, 1972b)。 その後,さ らに鉱石の性質を検討して,こ の鉱石の位 硫化鉄鉱鉱床は,