First evidence of dmisteinbergite (CaAl2Si2O8 polymorph) in high-grade metamorphic rocks
نویسندگان
چکیده
Abstract We identified dmisteinbergite, the rare trigonal polymorph of CaAl2Si2O8, for first time in high-grade metamorphic rocks. Dmisteinbergite occurs as a crystallization product silicate melt inclusions (nanogranitoids) garnet from three host rocks with different protoliths and re-equilibration conditions, i.e., 1.0 to 4.5 GPa. Raman spectra compositions dmisteinbergite here investigated are overall identical those previously characterized artificial natural dmisteinbergite. In nanogranitoids, this phase coexists other metastable polymorphs feldspar (kumdykolite, kokchetavite) SiO2 (quartz, cristobalite), recently interpreted result undercooling, supersaturation rapid confined micrometric pore. formation likely results similar process, thus it should be regarded kinetically controlled phase. Moreover, investigation well offers new insights into behavior materials under non-equilibrium conditions.
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ژورنال
عنوان ژورنال: American Mineralogist
سال: 2022
ISSN: ['0003-004X', '1945-3027']
DOI: https://doi.org/10.2138/am-2022-8505