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Low- P granulite facies metapelitic migmatites in the Wuluma Hills, Strangways Metamorphic Complex, Arunta Block, preserve evidence of polyphase deformation and migmatite formation which is of the same age of the c. 1730 Ma Wuluma granite. Mineral equilibria modelling of garnet-orthoproxene-cordierite-bearing assemblages usingthermocalc is consistent with peak S3 conditions of 6.0–6.5 kbar and 850–900 °C. The growth of orthopyroxene and garnet was primarily controlled by biotite breakdown during partial melting reactions. Whereas orthopyroxene in the cordierite-biotite mesosome shows enrichment of heavy-REE (HREE) relative to medium-REE (MREE), orthopyroxene in adjacent garnet-bearing leucosome shows depletion of HREE relative to MREE. There is no appreciable difference in major element contents of minerals common to both the mesosome and leucosome. The REE variations can be satisfactorily explained by decoupling of major element and REE partitioning, in the context of appropriate phase-equilibria modelling of a prograde path at ∼6 kbar. Sparse garnet nucleii formed at ∼760 °C, along with concentrated leucosome development and preferentially partitioned HREE. Further heating to ∼800 °C at constant or subtly increasing pressure conditions additionally stabilized orthopyroxene and decreased the garnet mode. Orthopyroxene in the leucosome inherited an REE pattern consequent to the partial consumption of garnet, it being distinct from the REE pattern in mesosome orthoproxene that was mostly controlled by biotite breakdown. Such within-sample variability in the enrichment of heavy REE indicates that caution needs to be exercised in the application of common elemental partitioning coefficients in spatially complex metamorphic rocks. [ABSTRACT FROM AUTHOR]

Pods of granulite facies dioritic gneiss in the Pembroke Valley, Milford Sound, New Zealand, preserve peritectic garnet surrounded by trondhjemitic leucosome and vein networks, that are evidence of high- P partial melting. Garnet-bearing trondhjemitic veins extend into host gabbroic gneiss, where they are spatially linked with the recrystallization of comparatively low- P two-pyroxene-hornblende granulite to fine-grained high- P garnet granulite assemblages in garnet reaction zones. New data acquired using a Laser Ablation Inductively Coupled Plasma Mass Spectrometer (LA-ICPMS) for minerals in various textural settings indicate differences in the partitioning of trace elements in the transition of the two rock types to garnet granulite, mostly due to the presence or absence of clinozoisite. Garnet in the garnet reaction zone (gabbroic gneiss) has a distinct trace element pattern, inherited from reactant gabbroic gneiss hornblende. Peritectic garnet in the dioritic gneiss and garnet in trondhjemitic veins from the Pembroke Granulite have trace element patterns inherited from the melt-producing reaction in the dioritic gneiss. The distinct trace element patterns of garnet link the trondhjemitic veins geochemically to sites of partial melting in the dioritic gneiss. [ABSTRACT FROM AUTHOR]