saussuritization

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saussuritization The complete or partial alteration of calcium-rich plagioclase to a fine-grained aggregate of secondary, sodicrich plagioclase, epidote, muscovite, calcite, scapolite, and zeolites. The process commonly takes place during the low-grade regional metamorphism of gabbros and basalts, both of which contain plagioclase as an essential component.