AL-FE3+ SUBSTITUTION IN SAMBAGAWA PYRALSPITE GARNET

Pyralspite garnet with a minor andradite component is recognized in th e Sanbagawa metamorphic belt, Japan. Such garnet can be classified int o two types with respect to the chemistry. The first is normally zoned with an Mn-rich core, and the second type is chemically sector-zoned almandine. A negative correlation between Al and Mn recognized in the normally zoned type suggests that high Mn content as well as high oxyg en fugacity favours the formation of Fe3+-bearing pyralspite garnet. D istinct Al deficiency in the chemically sector-zoned garnet may be a r esult of the growth under disequilibrium conditions.