1986 Volume 36 Issue 200 Pages 459-474
The Hokusatsu district of southern Kyushu has been known as one of the most mineralized districts of gold in japan, and many epithermal gold-silver quartz vein deposits occur especially in the Hokusatsu district. Recently special attention has been paid to this district by exploration geologists because of extremely gold-rich veins discovered at Hishikari by Metal Mining Agency of Japan (MMAJ) in 1981.
In this paper, regional characteristics of physiography and tectonic elements were analyzed with special reference to the gold-silver mineralization in the Hokusatsu district, using topgraphic maps, Landsat Imagery and gravity data, as well as geologic information. The results are as follows.
Many collapsed basins were observed and it was found that major gold-silver deposits tend to occur at outer fringes of those basins. The following three stages were destinguished for the development history of those volcanismrelated basins.
1st. stage (Miocene): Relatively small scaled collapsed basins were formed, and many steep inclined fractures were associated, providing the most suitable environment for the vein-type mineralization.
2nd. stage (Pliocene-Early Pleistocene): The Hokusatsu-type collapsed basins were formed in association with a series of violent volcanism mainly in the Hokusatsu district. The gold-sivler mineralization occured at the fringe of the collapsed basins formed by the volcanism of this stage.
3rd. stage (Late Pleistocene-Holocene): The center of main volcanic activity moved eastward along Kagoshima Bay. The Kagoshima Bay-type collapsed basins known as a so-called Quaternary caldera were formed along Kagoshima Bay. Volcanism of this stage is still active and some geothermal systems are associated. Gold mineralization is also expected to have formed in relation to the volcanism of this stage.
