AN EXPERIMENTAL STUDY OF Fe-Mg PARTITIONINGS BETWEEN ORTHOPYROXENE AND CORDIERITE IN THE Mg-RICH PORTION OF THE Mg_3Al_2Si_3O_<12>-Fe_3Al_2Si_3O_<12> SYSTEM AT ATMOSPHERIC PRESSURE : CALIBRATION OF ITS GEOTHERMOMETRY FOR HIGH-TEMPERATURE GRANULITES AND IGNEOUS ROCKS
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AN EXPERIMENTAL STUDY OF Fe-Mg PARTITIONINGS BETWEEN ORTHOPYROXENE AND CORDIERITE IN THE Mg-RICH PORTION OF THE Mg_3Al_2Si_3O_<12>-Fe_3Al_2Si_3O_<12> SYSTEM AT ATMOSPHERIC PRESSURE : CALIBRATION OF ITS GEOTHERMOMETRY FOR HIGH-TEMPERATURE GRANULITES AND IGNEOUS ROCKS
Division of Earth Sciences, Department of Biosphere and Geosphere Sciences, Faculty of Science, Ehime University
Division of Earth Sciences, Department of Biosphere and Geosphere Sciences, Faculty of Science, Ehime University
抄録(英)
Exchange reactions of Fe^<2+> and Mg^<2+> between orthopyroxene and cordierite (abbreviated to Opx and Crd, respectively) : [chemical formula] were experimentally investigated in the Mg-rich portion of the pyrope (Mg_3Al_2Si_3O_<12>)-almandine (Fe_3Al_2Si_3O_<12>) system at temperatures from 1000℃ to 1325℃ under atmospheric pressure. Combining the volume data, the distribution coefficient of Fe-Mg partitionings between these phases, K_D(=[numerical formula]), was formulated as ln K_D=(1424+7.02P)/T-0.619,where P and T are in kbar and K. This reaction is temperature-dependent and would be a useful geothermometer. The applications of this orthopyroxene-cordierite thermometer to some Antarctic granulites yield equilibration temperatures of 100℃-200℃ lower than the previous estimations. This suggests that the exchange reaction of Fe^<2+> and Mg^<2+> between orthopyroxene and cordierite continued down to closure temperatures of 500℃-600℃ caused by subsequent cooling after the peak of metamorphism. Temperature estimations using the present orthopyroxene-cordierite thermometer for the igneous suites including S-type tonalite, rhyolite and granulitic xenoliths in andesite are in good agreement with those obtained from other thermometers.
雑誌書誌ID
AA1072335X
雑誌名
Proceedings of the NIPR Symposium on Antarctic Geosciences
AN EXPERIMENTAL STUDY OF Fe-Mg PARTITIONINGS BETWEEN ORTHOPYROXENE AND CORDIERITE IN THE Mg-RICH PORTION OF THE Mg_3Al_2Si_3O_<12>-Fe_3Al_2Si_3O_<12> SYSTEM AT ATMOSPHERIC PRESSURE : CALIBRATION OF ITS GEOTHERMOMETRY FOR HIGH-TEMPERATURE GRANULITES AND IGNEOUS ROCKS
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概要
