菱刈鉱山の鉱脈深部の特徴と探鉱適用への検討

抄録

The Hishikari low-sulfidation epithermal gold-silver deposits, located in northern Kagoshima, Japan, consist of the Honko and Sanjin deposits hosted in the Cretaceous Shimanto Supergroup and the Quaternary Hishikari Lower Andesite, and the Yamada deposit hosted in the Hishikari Lower Andesite. Fluid inclusion microthermometry on the Zuisen-6 vein was conducted for understanding gold mineralization in the deeper part of the deposit. Homogenization temperatures of fluid inclusions in the Zuisen-6 vein do not change with depth, suggesting that the hydrothermal fluid moved to the shallower part of the vein without cooling. The increased salinity in the shallow part and the presence of truscottite and bladed quartz in the deeper part suggest that the hydrothermal fluid may have been continuously boiling, and the deepest depth of gold mineralization can be estimated by determining the deepest boiling depth. The estimated deepest depth limit of gold mineralization of the Zuisen-6 vein is -105 to -150ML, which is consistent with the results of drilling data in the surrounding area. This suggests a relationship between hydrothermal boiling and gold mineralization at the depth of the gold deposit such as the Hishikari low-sulfidation epithermal gold-silver deposits, providing new insights into estimating the lower limit of gold mineralization depth using the boiling depth. This indicator might be effective in the exploration at the deeper part of the deposit.