The western part of the Arunta Inlier, central Australia, consists of major northward-tilted blocks separated by major thrust faults - the Anmatjira, Napperby, Redbank-Mount Zeil and Mount Sonder-Mount Razorback faults-associated with major Bouguer gravity anomalies. The Redbank-Mount Zeil thrust zone (RTZ) separates a granulite-facies suite to the north from a paragneiss-migmatite-orthogneiss suite to the south. This fault is marked by major radiometric, magnetic, and morphological discontinuities, and consists of northward-dipping protomylonite, mylonite, ultramylonite, and phyllonite, formed under a heterogeneous ductile shear- regime. Kernels of granulite, paragneiss, and migmatite abound. The RTZ truncates all other structures and postdates all juxtaposed units. Dynamothermal activity along the RTZ about 1000-900 Ma ago may be reflected by possibly reset Rb-Sr ages in blastoporphyritic gneisses and migmatite to the north and south, respectively. Major Palaeozoic movements are indicated by Devonian fanglomerate (Brewer Conglomerate), while younger reactivation is suggested by morphological features. Two alternative models are considered: (1) an antecedent of the RTZ formed an early boundary between an older igneous-dominated granulite block to the north and a younger amphibolite-facies paragneiss belt to the south prior to about 1600 Ma ago; or (2) contemporaneous granulite and paragneiss terrains representing different depth zones within a vertically zoned crust were allochthonously juxtaposed by the thrusting. The uplift of basic granulites along the RTZ is estimated from thermobarometric measurements to be at least 20 km, accounting for the Papunya Bouguer anomaly high of more than 500 µm/s2 . The emplacement of deep-seated basic intrusions, the ensuing geothermal rises, and crustal anatexis may have been genetically and temporally related.
