Calculated mineral equilibria for eclogites in CaO–Na₂O–FeO–MgO–Al₂O₃–SiO₂–H₂O: application to the Pouébo Terrane, Pam Peninsula, New Caledonia

Abstract

The high‐ P , medium‐ T Pouébo terrane of the Pam Peninsula, northern New Caledonia includes barroisite‐ and glaucophane‐bearing eclogite and variably rehydrated equivalents. The metamorphic evolution of the Pouébo terrane is inferred from calculated P–T and P–T – X H2O pseudosections for bulk compositions appropriate to these rocks in the model system CaO–Na 2 O–FeO–MgO–Al 2 O 3 –SiO 2 –H 2 O. The eclogites experienced a clockwise P–T path that reached P ≈19 kbar and T ≈600 °C. The eclogitic mineral assemblages are preserved because reaction consequent upon decompression consumed the rocks’ fluid. Extensive reaction occurred only in rocks with fluid influx during decompression of the Pouébo terrane.