抄録
Variations of mineral composition and exchangeable interlayer cation composition of clay minerals from altered rocks of Kuroko deposits have been determined by using samples obtained from eleven drillholes around the Matsumine, Shakanai, and Matsuki mines in the Hokuroku District, Japan. The composition of exchangeable interlayer cations of clay minerals, in particular the Ca/Na ratio, may have been strongly controlled by the chemical composition of hydrothermal solution in the site. Sericite/montmorillonite interstratified minerals occur in the mordenite, analcime, and K-feldspar zones as well as in the sintermediate zone between the montmorillonite and the sericite-chlorite zones. Such interstratified minerals contain comparatively large amounts of alkali metal cations as exchangeable interlayer cations. The variation of expandability in the interstratified minerals and the corresponding concentration of alkali metal cations in the minerals which were observed in the column of a drillhole are related to the percolation of hydrothermal solution containing large amounts of alkali metal cations.
