中国地方の花崗岩に伴う2，3のカオリン鉱床について

The granitic rocks occurring in Chugoku District are classified into three units, that is the granitic rocks belonging to the "Yakuno Intrusive Rocks", the "Ryoke Granitic Rocks" and the "Chûgoku Batholith". The last one is divided further into three groups or plutonic complexes : the Hiroshima granitic complex, the central plutonic group and the San'in granitic complex. Most of the kaolin deposits within Hiroshima and Shimane Prefectures are found in the "Chûgoku Batholith"; they have hitherto been found in the central plutonic group and the San'in granitic complex. While a small number of kaolin deposits showing similar occurrence are also observed in other kind of rocks, for instance, at Toyosaka and Kôtachi. Genetic relation between pyrophyllite deposits prevailing in rhyolitic rocks of Chûgoku District and the kaolin deposits remains not ascertained. On the basis of altered states of the surrounding rocks, the deposits in question are infered to have been formed by ascending spring containing CO2 along with surface weathering. The minerals of the deposits have been identified to halloysite, sericite, secondary quartz, kaolinite, relics of primary quartz, and unaltered feldspars by means of chemical analysis, differential thermal analysis, X-ray analysis and electron-microscopy.