Prograde and Retrograde Eclogites in the Sambagawa Metamorphic Belt, Besshi District, Japan

Abstract
The hornblende garbenschist horizon of the Lower Schieferhulle series (LSH) in the SW Tauern Window, Austria, contains the assemblage hornblende + kyanite + staurolite + garnet + biotite + epidote + plagioclase + ankerite + quartz + rutile + ilmenite, with either chlorite or paragonite present in all samples. These assemblages are divariant in the system SiO2-Al2O3-TiO2-Fe2O3-MgO-FeO-MnO-CaO-Na2O-K2O-H2O-CO2. Garnet-biotite geothermometry yields temperatures of final equilibration of ˜550 °C, and garnet-plagioclase-kyanite-quartz geobarometry indicates pressures of 6–8 kb for the matrix assemblage and 9–10 kb for plagioclase inclusions in garnet. Quantitative modelling of zoned garnet, hornblende, and plagioclase indicates growth and equilibration along a decompression path from ˜530 °C, 10 kb to ˜550 °C, 7 kb. Fluid inclusion data constrain the uplift path to have passed through a point at ˜ 375 °C, 1.5 kb.

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