Reassessing the timing of high strain deformation in the Strangways Metamorphic Complex, central Australia, by in-situ Mica Rb-Sr and Titanite U-Pb geochronology

Dating the timing of deformation within shear zones is critical to quantifying orogenic processes and developing time-resolved regional tectonic frameworks. Such work requires the integration of detailed microstructural analysis with in-situ geochronology to quantify when deformation mechanisms were active at the microscale. The Proterozoic, granulite-facies Strangways Metamorphic Complex was exhumed during the Devonian to Carboniferous intracontinental Alice Springs orogeny. New microstructural observations, quartz c -axis orientation analyses, mica chemistry, Ti-in-biotite thermometry, and in-situ mica Rb-Sr and titanite U-Pb geochronology outline a detailed history of ductile shearing across the complex. Movement along the north boundary shear zone of Strangways Metamorphic Complex appears to have initiated ca. 382 Ma, preceding peak metamorphism in the area during the Alice Springs orogeny. Widespread reverse-sense ductile shearing occurred within the Strangways Metamorphic Complex between ca. 365 and 355 Ma and correlates with rapid cooling of the region. Late-stage ductile deformation is recorded at ca. 335 Ma, likely reflecting the terminal exhumation of the Strangways Metamorphic Complex. Finally, the new in situ muscovite and biotite Rb-Sr data collected herein permit comparison with previous two-point mica Rb-Sr isochrons and 40 Ar- 39 Ar dates from the same specimens. In the rocks analyzed, the biotite Rb-Sr system returned dates similar to the previous 40 Ar- 39 Ar white mica dates, perhaps indicating a similar effective closure temperature. Supplementary material: https://osf.io/yjp24/?view_only=0bf5bec9f5c94a1aa4fb413320ec24e8