Abstract
The Akeshi mine, located in the southern Satsuma Peninsula, Kyushu is the one of the Nansatsu or high sulfidation type gold deposits in Japan which is currently in operation, and has produced approximately 6.5 tons of gold since its discovery in 1880. The gold mineralization occurs in massive silicified bodies hosted by Neogene andesitic rocks. In the Akeshi mine area three silicified ore bodies are distributed linearly along a NNE-SSW direction and appears to be controlled by the existing regional stress field of southern Kyushu.
The Akeshi deposit has a mushroom shape with an areal direction of 300×200m2 and approximately 270m in depth. It is composed of leached vuggy and/or compact silicified rock enveloped by a narrow argillic zone with kaolinite, dickite, smectite and alunite. Four ore bodies are emplaced within the silicified zone. The dominant ore minerals are pyrite, goethite, luzonite and native gold. Northeast-southwest fractures are closely related with the ore bodies with high Au grade. Gold mineralization may have been formed by neutralized and low saline fluid after the silicification stage which is characterized by more acid fluids.
An exploration with program aimed NE-SW trending fractures led to the discovery of No.4 ore body. Further study and exploration in the lower portion of the deposit will provide additional information and, hopefully, make a clear picture of the entire hydrothermal system responsible for the gold mineralization.
