On the Kaolin Deposits of the Kampaku Mine

Abstract

The Kampaku Mine is situated about 20km north of Utsunomiya City, Tochigi Prefecture. The country rock of the deposits is biotite-liparite of late Tertiary age. The ore deposits consist of a vein like kaolin mass, two gold-bearing quartz veins, which are the foot wall of the kaolin mass, two dyxe-like silicified country rocks, which are the hanging wall of the kaolin mass, and kaolinized liparite which envelopes them. The deposits are banded, striking about N 60°W, and dipping 70°N.
Field observations indicate that kaolinization occurred along a fissure after the slicification of the country rock and the formation of the gold vein. Similar phenomena occurred also in the kaolinized liparite zone which has lower grade ore but greater volume.
The various examinations (microscope, electron-microscope, differential thermal analysis, chemical analysis, staining test and X-ray analysis) of the ores related to their localities revealed that kaolinization was caused by the upward moving hydrothermal solutions or hot spring containing sulfuric acid and that the qualities of the ores and crystallinity of kaolinite are better at the upper level and poorer at the lower. The kaolin minerals composing the ores are kaolimite containing some halloysite. The purely white kaolin has hardly any impurity except a small amount of very fine grained diaspore. The other kaolin masses commonly contain alunite, ferric minerals, quartz etc.