Multi-scale analysis of Proterozoic shear zones: An integrated structural and geophysical study

Structural mapping of poorly exposed shear zone outcrops is integrated with the analysis of aeromagnetic and Bouguer gravity data to develop a multi-scale kinematic and relative overprinting chronology for the Palaeoproterozoic Tallacootra Shear Zone, Australia. D2 mylonitic fabrics at outcrop record Kimban-aged (ca. 1730–1690 Ma) N–S shortening and correlate with SZ1 movements. Overprinting D3 sinistral shear zones record the partitioning of near-ideal simple shear and initiated Riedel to regional-scale SZ2 strike-slip on the Tallacootra Shear Zone (SZ2). Previously undocumented NE–SW extension led to the emplacement of aplite dykes into the shear zone and can be correlated to the (ca. 1595–1575 Ma) Hiltaba magmatic event. D4 dextral transpression during the (ca. 1470–1450 Ma) Coorabie Orogeny reactivated the Tallacootra Shear Zone (SZ2–R4) exhuming lower crust of the northwestern Fowler Domain within a positive flower structure. This latest shear zone movement is related to a system of west-dipping shear zones that penetrate the crust and sole into a lithospheric detachment indicating wholesale crustal shortening. These methods demonstrate the value of integrating multi-scale structural analyses for the study of shear zones with limited exposure.