福島県石ケ森鉱山吹屋石膏鉱床の構造と母岩の変質について
1971 年 87 巻 999 号 p. 389-394
詳細
1971 年 87 巻 999 号 p. 389-394
The Fukiya gypsum deposit occurs in pale green tuffs of rhyolitic composition of the Middle Miocene age. The deposit has two unit-body groups, each consisting of four overlapping, lenticular gypsum beds. The gypsum beds are concordant with stratification of wall rocks and have a direction of elongation parallel to the structural weak zone. The total vertical extent of the deposit reaches about 140m.
Each gypsum bed has one or more centers of mineralization, where the deposition of gypsum might have exceeded the sedimentation of pyroclastic materials.
The gypsum deposition was associated mainly with chloritization of tuffs ands sporadic dissemination of pyrite in the deposit accompanied the sericitization. Diagenetic montmorillonitization seems to have affected rocks of much lower formations than the gypsum horizon, but it is not recognized in the chlorite-sericite zone of the gypsum deposit. This might suggest the stability of the zone against the diagenetic alteration.
