Blueschist and eclogite in tectonic melange, Port Macquarie, New South Wales, Australia

Abstract

Abstract The Rocky Beach Metamorphic Melange contains metre-scale phacoids of high- P low- T metamorphic rocks embedded in chlorite-actinolite schist. The phacoids include eclogite, glaucophane schist and omphacitite and provide evidence for four episodes of metamorphism with mineral assemblages: M 1 = actinolite-glaucophane-titanite-apaite, M 2 = almandine-omphacite-lawsonite ±quartz, M 3 = phengite- glaucophane-K-feldspar-quartz, and M 4 = chlorite-actinolite-calcite-quartz-titanite-white mica ± albite ± talc. M 1 -M 3 occurred at a Neoproterozoic-Early Palaeozoic convergent plate boundary close to the eastern margin of Gondwana. Peak metamorphic conditions were attained during the static phase M 2 , with temperatures of ~560°C and pressures in excess of 1.8 GPa, equivalent to a depth of burial of at least 54 km.