The Petrogenetic Grid and Subfacies for Middle-temperature Metapelites |
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Authors: | KEPEZHINSKAS K B; KHLESTOV V V |
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Institution: | Institute of Geology and Geophysics, Siberian Branch of the Academy of Sciences of the USSR Novosibirsk-90, USSR |
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Abstract: | All a priori possible types of PT diagrams for medium-temperaturequartz- and muscovite- bearing metapelites, are deduced theoreticallyon the base of analysis of the concentration diagram for thesystem SiO2-AI2O3-Fe2O3-FeO-MgO-CaO-K2O-Na2O-H2O. Comparisonswith all known mineralogic observations permitted one to choosethe most probable type of diagram for all those derived. PTcalibration of this paragenetic grid is given as based on experimentaldata. It is established, that the Fe/Mg ratio decreases in mineralsof all the univariant associations with increase of pressure.The same is true of divariant associations at constant temperature. The suggested new scheme of subfacies permits the detailingof estimates of the PT conditions for the medium-temperatureregion (in the first place with respect to pressure). |
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