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GARCIA-CASCO ANTONIO; HAISSEN FAOUZIYIA; CASTRO ANTONIO; EL-HMIDI HASSAN; TORRES-ROLDAN RAFAEL LUIS; MILLAN GUILLERMO 《Journal of Petrology》2003,44(10):1727-1757
We document experiments on a natural metapelite in the range650775°C, 614 kbar, 10 wt % of added water,and 700850°C, 410 kbar, no added water. Staurolitesystematically formed in the fluid-present melting experimentsabove 675°C, but formed only sporadically in the fluid-absentmelting experiments. The analysis of textures, phase assemblages,and variation of phase composition and FeMg partitioningwith P and T suggests that supersolidus staurolite formed at(near-) equilibrium during fluid-present melting reactions.The experimental results are used to work out the phase relationsin the system K2ONa2OFeOMgOAl2O3SiO2H2Oappropriate for initial melting of metapelites at the upperamphibolite facies. The PT grid developed predicts theexistence of a stable PT field for supersolidus staurolitethat should be encountered by aluminous Fe-rich metapelitesduring fluid-present melting at relatively low temperature andintermediate pressures (675700°C, 610 kbarfor XH2O = 1, in the KNFMASH system), but not during fluid-absentmelting. The implications of these findings for the scarcityof staurolite in migmatites are discussed. KEY WORDS: metapelites; migmatites; partial melting; PT grid; staurolite 相似文献
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