秋田県大葛地区における黒鉱探査について
2001 年 51 巻 1 号 p. 7-18
詳細
2001 年 51 巻 1 号 p. 7-18
The Okuzo prospect is located 20 km southeast of Odate city, Akita prefecture. The Metal Mining Agency of Japan (MMAJ) discovered Kuroko-style mineralisation accompanying lead, zinc, gold and silver during a regional geological survey of the area.
The Okuzo prospect is located on the southeastern rim of the Hokuroku Kuroko Basin, which is closed along a line extending from the Gacchimaeda fault to the boundary of the southern rim of the Gattsu basin based on geological and gravity data. As a result of the geological survey by the MMAJ, a fragment of Kuroko ore with a diameter of 15cm was discovered in an outcrop of volcaniclastic rock; analysis returned 0.75g/t Au, 160g/t Ag, 0.2% Cu, 5.2% Pb, 23.0% Zn and 39.5% BaSO4.
Based on induction polarization and drilling surveys, the characteristics or hanging-wall and foot-wall alteration associated with Kuroko mineralisation were identified as the presence plagioclase and chlorite-sericite, respectively. It is proposed that volcanic activity had been continuous at the middle Miocene after the Kuroko mineralisation and resulted in the formation of vent breccia.
