The poly-metamorphic evolution of the Strangways Range granulites of central Australia has been constrained by the phase stability relationships of silica-saturated aluminous gneisses in KFMASH, in conjunction with geothermobarometry and equilibrium thermodynamics. Two contrasting, but overlapping, P-T paths are proposed. The first (M1, at 1800 Ma) had an ‘anticlockwise’ P-T path (i.e., increasing P/T with time) and was terminated by isobaric cooling from 850–950 °C, at 8–9 kb, to a stable crustal geotherm (<700°C). In contrast, the second granulite metamorphism (M2–M5, suggested to be at 1400–1500 Ma; Goscombe, 1992a) followed a ‘clockwise’ P-Tpath (i.e., decreasing P/T with time) terminated by decompression and cooling to ˜6–7 kb on a stable crustal geotherm. M2–M5 occurred during reworking of M, granulites by compressional orogenesis (Goscombe, 1992a). Initially, loading and prograde metamorphism accompanied non-coaxial ductile shear and fold repetition (D2–D3). Prograde metamorphism was followed by uplift and retrogression accompanying oblique transpression and shear zone development while still under compression (D4–D5) (Goscombe, 1992a). The poly-metamorphic evolution indicates that ductile deformation reworked the M1 granulites in an orogenic episode unrelated, both temporally and tectonically, to M1, metamorphism (Goscombe, 1992b).
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Ben Goscombe (1992) studied this question.