Abstract
In the Miocene formations distributed in the east and the north of the Iide mountainland there occur many black-ore type deposits which are mainly composed of gypsum containing pyrite, chalcopyrite, galena, sphalerite, anhydrite, barite and calcite. These ore-deposits can be found in several formations and they clearly cross the bedding plane. Moreover, the structures of mother rocks are sometimes left in the massive alabaster ore body. In the rhyolite covering the upper part of the deposits, network ore-vein and impregnated ore can sometimes be found. From these facts it is considered that the gypsum ore deposits in this area may be formed by the hydrothermal solution genetically related to the igneous action which occurred after the country rocks had been formed.
