新潟県佐渡小木町江積産沸石類

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Phillipsite, analcime, chabazite, gmelinite, calcite, and smectite are found in vesicles and fissures of basaltic hyaloclastite, pillow and ordinary lavas at the locality. The first and second form monominerallic aggregates, respectively, or aggregates of two. The third and fourth simulate a single crystal composed of their epitaxial intergrowth. The anhydrous empirical formulae of the first to fourth zeolites are respectively, Na_<8.62>K_<5.54>Ca_<0.79>Al_<15.97>Si_<32.09>O_<96>, Na_<14.86>Al_<15.75>Si_<32.48>O_<96>, Na_<11.93>K_<3.17>Ca_<0.13>Al_<15.14>Si_<32.80>O_<96> and Na_<13.07>K_<2.16>Ca_<0.24>Al_<15.37>Si_<32.55>O_<96>, where all are normalized to O=96. Phillipsite and chabazite are low in CaO content, especially the latter is one of the most siliceous low Ca chabazite. Gmelinite is high in K_2O content, extending the known compositional range. The vesicles and the deformed ones are resided by calcite, phillipsite, analcime and smectite, whereas the fissures have phillipsite, analcime, chabazite-gmelinite intergrowth and smectite therein. Some of fissures cut vesicles. Above association means that more watery zeolites with looser structures appeared later within a single rock. All the described zeolites have Si/Al about 2,which corresponds to the point between SiO_2 saturation and undersaturation states in zeolites. Those with above 2 are able to co-exist with silica minerals, whereas those with below 2 are not.
国立科学博物館の論文
1995-12-22

新潟県佐渡小木町江積産沸石類

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