秋田県銀山黒鉱鉱床の鉱石鉱物

Abstract

The Ginzan mine is situated at approximately 40°28' north latitude and 140°48' east longitude. The ore deposits of the Ginzan mine belong to the Kuroko-type. The present paper deals with the characteristics of the mode of occurrence, chemical and mineral compositions, mineral paragenesis of ores, properties of minerals and fluid inclusions.The ore deposits are composed of several unit orebodies, such as sulphide, Keiko and Sekko-ko bodies. The ores of the sulphide bodies are complicated ores consisting of Kuroko, Oko and Ryukako. Rare minerals found in the ores are electrum, native silver, argentite, pearceite, enargite, cosalite, gersdorffite and so on. The Keiko bodies occur on a small scale in some parts of the ore deposits. The Sekko-ko bodies consist mainly of anhydrite with minor amounts of gypsum.Bi-, Ni- and Co-content of sulphide ores are approximately 300, 30 and 20 ppm in average respectively. And Sr-content of anhydrite from the sulphide bodies is approximately 7 ppm and that from the Sekko-ko bodies is approximately 12ppm in average.The ranges of the homogenization temperature and the salinity of fluid inclusions in sphalerite from the sulphide bodies are from 182°to 287°C (241°C in average) and from 2.9 to 7.4 wt.%(equivalent to NaCl).Some genetical considerations on the ore deposits, and the similarities and differences between the ore mineralogy from the Ginzan ore deposits and that from other Kuroko deposits are also described.