High-Grade Reworking of Central Australian Granulites: Metamorphic Evolution of the Arunta Complex |
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| Authors: | GOSCOMBE BEN |
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| Institution: | Geology Department, University of Melbourne, Parkville 3052, Victoria Australia |
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| Abstract: | The poly-metamorphic evolution of the Strangways Range granulitesof central Australia has been constrained by the phase stabilityrelationships of silica-saturated aluminous gneisses in KFMASH,in conjunction with geothermobarometry and equilibrium thermodynamics.Two contrasting, but overlapping, P-T paths are proposed. Thefirst (M1, at 1800 Ma) had an ‘anticlockwise’ P-Tpath (i.e., increasing P/T with time) and was terminated byisobaric cooling from 850–950 C, at 8–9 kb, toa stable crustal geotherm (<700C). In contrast, the secondgranulite metamorphism (M2–M5, suggested to be at 1400–1500Ma; Goscombe, 1992a) followed a ‘clockwise’ P-Tpath(i.e., decreasing P/T with time) terminated by decompressionand cooling to {small tilde}6–7 kb on a stable crustalgeotherm. M2–M5 occurred during reworking of M, granulitesby compressional orogenesis (Goscombe, 1992a). Initially, loadingand prograde metamorphism accompanied non-coaxial ductile shearand fold repetition (D2–D3). Prograde metamorphism wasfollowed by uplift and retrogression accompanying oblique transpressionand shear zone development while still under compression (D4–D5)(Goscombe, 1992a). The poly-metamorphic evolution indicatesthat ductile deformation reworked the M1 granulites in an orogenicepisode unrelated, both temporally and tectonically, to M1,metamorphism (Goscombe, 1992b). |
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