Calculated Phase Relations in High-Pressure Metapelites in the System NKFMASH (Na2O-K2O-FeO-MgO-Al2O3-SiO2-H2O) |
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Authors: | WEI CHUNJING; POWELL ROGER |
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Institution: | 1 SCHOOL OF EARTH AND SPACE SCIENCES, BEIJING UNIVERSITY, BEIJING 100871, P.R. CHINA
2 SCHOOL OF EARTH SCIENCES, THE UNIVERSITY OF MELBOURNE, VIC. 3010, AUSTRALIA |
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Abstract: | Using an internally consistent thermodynamic dataset and updatedmodels of activitycomposition relation for solid solutions,petrogenetic grids in the system NKFMASH (Na2OK2OFeOMgOAl2O3SiO2H2O)and the subsystems NKMASH and NKFASH have been calculated withthe software THERMOCALC 3.1 in the PT range 536kbar and 400810°C, involving garnet, chloritoid,biotite, carpholite, talc, chlorite, kyanite/sillimanite, staurolite,phengite, paragonite, albite, glaucophane, jadeite, with quartz/coesiteand H2O in excess. These grids, together with calculated AFMcompatibility diagrams and PT pseudosections, are shownto be powerful tools for delineating the phase equilibria andPT conditions of Na-bearing pelitic assemblages for avariety of bulk compositions from high-P terranes around theworld. These calculated equilibria are in good agreement withpetrological studies. Moreover, contours of the calculated phengiteSi isopleths in PT pseudosections for different bulkcompositions confirm that phengite barometry is highly dependenton mineral assemblage. KEY WORDS: phase relations; HP metapelite; NKFMASH; THERMOCALC; phengite geobarometry |
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Keywords: | : phase relations HP metapelite NKFMASH THERMOCALC phengite geobarometry |
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