Marbles from the Upper Calcsilicate Unit of the Reynolds Range Group, central Australia, experienced regional Proterozoic greenschist-facies metamorphism, but preserve relicts of an earlier, higher temperature assemblage. The earlier assemblage is typified by intermediate scapolite that predates regional metamorphic fabrics, and it is pseudomorphed by assemblages that were stable during regional greenschist facies metamorphism. The scapolite was formed at temperatures in excess of 540–575 °C, far higher than the regional metamorphic temperatures (400–450 ºC). Marbles and associated pelites display variable, but lower δI8O values than are typical of greenschist facies metasediments. Scapolitization and lowering of isotope ratios probably resulted from pre-regional metamorphic contact metamorphism around early granites.

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