変質鉱物としての沸石 : 輝沸石-斜プチロル沸石,モルデン沸石および方沸石-ワイラカイト

概要

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Heulandite-clinoptilolite, mordenite and wairakite-analcime are widely found as alteration products of pyroclastic materials. In this article, the mineralogical properties of these zeolites are reviewed and the relationship between chemical composition in solid solution and the condition of formation of zeolite is discussed. In heulandite group, many investigators have reported no correlation between composition and depth of burial. In rocks of the same pyroclastic bed, however, high alkali heulandite has a tendency to occur in an earlier stage of alteration. High-calcium mordenite is found in rocks of relatively higher grade part of the zeolite facies. Hydrothermal experiments indicate that the Si/Al ratio of analcime varies as a function of temperature. But the silica content of natural analcime is not solely an indicator of temperature. In the solid solution of wairakite and its sodium analogue, high-alkali wairakite occurs in rocks of lower grade part of wairakite zone.
地学団体研究会の論文
1978-05-25