群馬県碓氷郡松井田町碓氷峠産のスコレス沸石

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Zeolites in the fissures of altered andesite (or andesitic ruff breccia) near Usui-toge, Matsuida, Gunma Prefecture, Japan, were investigated. Scolecite, chabazite, laumontite, epistilbite and heulandite were found on andradile formed on the wall of the fissures. The scolecite occurs as large spherule up to 5 cm in diameter. It consists of acicular scolecites at the center, slender prismatic scolecites and fibrous scolecites at the margin, with chabazites on its surface. And laumontites often penetrate the spherules. In a few centimeters along the fissures the rock is altered almost completely, except clinopyroxene phenocrysts, and there occur grossular, fine grained clinopyroxene, chabazite and epistilbite. The clinopyroxene phenocrysts are partially substituted by secondary amphiboles. The chemical compositions of scolecite by the x-ray microanalyzer depend on the position analyzed, and for example, the Na2O contents vary from 0.5l to 2.70 wt%. The average atomic proportion of scolecite are almost Cao.858 Na0.220 Al1.939 Si3.059 O10.000. ･4.07H2O. The unit cell constants of scolecites separated from a spherule also depend on the sample. These results show that scolecite has a wider range in chemical composition than that reported so far. The chemical compositions and the unit cell constants of chabazite, laumontite, andradite, grossular and clinopyroxene(phenocryst) are also reported. Zeolites and skam minerals in this place were probably formed in relation to the intrusion of Kumanotaira igneous rock.
群馬大学教育学部の論文

群馬県碓氷郡松井田町碓氷峠産のスコレス沸石

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