STUDY OF FORMATION MECHANISM OF INTERSTRATIFIED CHLORITE/SMECTITE

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Some samples of interstratified chlorite/smectite were collected from altered tuff breccia in Hiwaki-cho, alteredandesites in the Doyama area, Aira-cho, hydrothermally altered volcanic rocks in the Maurazaki area and Bonotsu area, altered andesites in the Fuke mine, Okuchi, and Kinzan, Yokogawa-cho, Kagoshima Prefecture. Interstratified chlorite/smectite samples were collected by sedimentation method, and analyzed by X-ray diffraction method. Altered minerals in the Doyama area could be divided into three zones, ZoneI, ZoneII and ZoneIII by the differences of mineral assemblage. The ZoneI is characterized by chlorite. The ZoneII is by interstratified chlorite/mont morillonite, and the ZoneIII is by montmorillonite. Altered rocks in Hiwaki-cho could be divided into three zones, inner, intermediate and outer zone, by the differences of mineral associations. The intermediate zone is divided into two subzones (A and B). Inner zone is characterized by kaolinite-chlorite-sericite-calcite, in … More termediate zone A is by kaolinite-chlorite-randomly interstratified mica/montmorillonite-calcite, intermediate zone B is by kaolinite-randomly interstratified mica/montmorillonite-randomly interstratified chlorite/montmorillonite,and outer zone is by montmorillonite-heulandite-mordenite. In the Okuchi area, chlorite zone(inner), mixed-layer chlorite/montmorillonite zone(intermediate), and montmorillonite zone (outer) are observed surrounding intruded hornblende andesite. Hydrothermally altered volcanic rocks are widely distributed in the southern part of the Bonotsu area. Clay minerals such as chlorite, smectite, sericite, interstratified mica/smectite and interstratified chlorite/smectite are formed in the altered rocks. In the Makurazaki area, hydrothermally altered andesites are widely distributed, and clay minerals in the altered rocks are kaolinite, interstratified mica/smectite, interstratified dioctahedral chlorite/smectite, dioctahedral smectite, trioctahedral chlorite, interstratified trioctahedral chlorite/smectite and trioctahedral smectite. Concerning the origin of the interstratified chlorite/smectite, the Makurazaki sample was probably formed from smectite in intermediate stage in the transformation of smectite to chlorite, whereas other samples were formed from chlorite on the process of transformation of chlorite into smectite. Less