Abstract
Liesegang ring has been well known as typical periodic precipitation pattern formed during diffusion process of chemical elements in gel and/or solution. Liesegang rings (several milimeters to a few centimeters in width) are characteristically developed in pyrophyllite ore deposits in Shobara district, Hiroshima prefecture, Southwest Japan. The mode of occurrence and mineralogical and chemical characteristics of the Liesegang ring were examined by means of optical microscope, X-ray diffraction, Xray fluorescence, electron microprobe and nuclide luminoscope. The Liesegang ring characterized by distinct alternate of deep and light color rings is developed in the extensively altered rocks which consist of pyrophyllite, sericite, interstratified mineral of mica and smectite, kaolinite, quartz and hematite. Hematite rings are characteristically observed in the both rings, particularly in deep color ring. Two types of rings are recognizable, one is perpendicular and the other is paralel to the flow structure of host rhyolitic rocks, respectively. The former is observed in close to pyrophyllite ore, the latter mainly in the marginal part of ore. These facts suggest that the formation mechanism of Liesegang rings relates intimately to the regional pyrophyllitic alteration of the district.
