Phase relations,Structure and Thermodynamic Properties of Na-Majorite:Experimental and Computer Modeling

Na-majorite is observed as an inclusion in mantle-derived diamonds and as mineral of rare ultra-deep xenoliths in kimberlites.Our experiments in different alumosilicate and carbonate-silicate systems at 7.0 and 8.5 GPa suggest that Na is incorporated in pyrope-rich garnet via the coupled substitution like Mg+Al=Si+Na.Thus,the mechanism of the Na-majorite formation assumed on mineralo-