Interstratified mica/smectite in the Ten-ei district, Fukushima Prefecture

Abstract

Three samples of interstratified mica/smectite were found in the argillized veins in the hydrothermally altered tuff and andesite in the Ten-ei district Fukushima Prefecture. The types of interstratifications of these minerals are g=2, g=3 and g ?? 3, and the proportions of the expandable layers are approximately 30%, 5% and 2%, respectively. Chemical analyses for these minerals, argillized rocks including these minerals and their wall rocks show the chemical compositions of these minerals considerably differ, with respect to Si/Al ratio in the tetrahedral layer, number of Fe in the octahedral layer and Na in the interlayer, and these differences of chemical compositions seem to be not related to those of their wall rocks. This result probably suggests the variations of the chemical compositions were influenced by those of hydrothermal solutions during the formation processes of these minerals.