Discontinuously Zoned Garnet in Sambagawa Schist from Central Shikoku, Japan
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The garnets in the Sambagawa siliceous pelitic schist from Tomisato, Central Shikoku,Japan, which have been described in this paper, belong to the type of reverse-zoned garnet. From zoning profiles for MnO and FeO and electron beam scanning images, individual garnet grains appear to be divided into four zones, core, intermediate zone, mantle and reverse zone in the rim. And the chemical composition changes discontinuously by about 9% for MnO between the outer part of the core (=ca. 32% for MnO) and the inner part of the intermediate zone and by about 7.2-16.5% for MnO between the outer part of the intermediate zone (=ca. 19.5-10.1% for MnO) and the inner part of the mantle. The garnets in the present specimen, therefore, will be newly designated as discontinuously zoned garnet.
Journal of science of the Hiroshima University. Series C. Geology and mineralogy