Regularly Interstratified Chlorite—Dioctahedral Smectite in Dike-Intruded Shales, Montana

Abstract

Abstract--Corrensite or 'corrensite-like' minerals occur in dike-intruded shales and siltstones of the Montana Group and Colorado Group (Early Cretaceous) in Western Montana. The < 1/xm size fraction of one specimen of this "corrensite-like" material has been studied in detail. X-ray diffraction data and chemical analysis indicate that this specimen is a regular or nearly regular interstratification of chlorite and dioctahedral smectite. Also described are other samples, which contain corrensite and additional phases. These samples were taken at several localities where basic dikes have intruded these shales and siltstones.

Comparisons Between the Diagenesis of Dioctahedral and Trioctahedral Smectite, Brazilian Offshore Basins

“…It commonly occurs in volcanogenic sequences and associated clastic sediments (Stephen and MacEwan, 1951;Kubler, 1973;Iijima and Utada, 1971;Wilson, 1971;Kubler et aL, 1974;Pevear and Whitney, 1982). Similar material has been reported in mafic intrusions (Sigvaldason and White, 1961;Harvey and Beck, 1962;Tomasson and Kristmannsdottir, 1972;Blatter et al, 1973;Furbish, 1975). Experimentally (Iiyama and Roy, 1963;Wyart and Sabatier, 1966;Velde, 1977;Whitney, 1983)corrensite has been formed from smectites.…”

Reaction Series for Dioctahedral Smectites

“…Their reaction products were, however, trioctahedral. A natural tosudite-chlorite association has been reported in Montana by Blatter et al (1973) in a metasomatic occurrence associated with a dike intruding chloritic shales. Tosudite was found next to the dike, grading into chlorite with increasing distance from the dike.…”

Corrensite of Hydrothermal Origin from Veitsivaara, Eastern Finland

“…The corrensite occurs as a thin layer on the vein walls, whereas calcite is mainly concentrated in the interior of the vein (Figure 2). Spherulitic textures, previously described in corrensite by Blatter et al (1973), are present in the fine-grained matrix. The material studied was hand-picked under a stereomicroscope.…”