Late paleo-mesoproterozoic plate margin deformation in the southern Gawler Craton: insights from structural and aeromagnetic analysis

Abstract: The integration of structural analysis of outcrop and aeromagnetic interpretation has revealed a complex tectonic evolution for the southern Gawler Craton that reflects the regional tectonic signal during the late Paleo- to early Mesoproterozoic. Results suggest that exposures at Yarlbrinda Hill comprise the margin of a highly deformed St Peter Suite pluton emplaced within the southwestern Gawler Craton at ca. 1611 Ma. D, at outcrop records east- to northeast-directed ductile thrusting. Regionally, this deformation overprints north-south trending dextral Yarlbrinda Shear Zone fabrics within ca. 1622 Ma St Peter Suite granite and ca. 1690-1670 Ma Tunkillia Suite granite. Progressive east to northeast directed thrust movements led to exhumation of the deformed ca. 1611 Ma granite. D-2 deformation is recorded by the brittle reactivation of first generation mylonitic fabrics, accompanied by cataclasis, alteration and pseuclotachylite development. D-3 records a switch to similar to northwest-southeast shortening, which led to the folding and tear faulting of the D1-2 shear zone. A switch to extension and subsequent rotations of the principle stress axes led to Hiltaba Suite granite emplacement and contemporaneous faulting under similar to east-west extension during D-4 and west-northwest-east-southeast extension during D-5.