High-grade Paleoproterozoic reworking in the southeastern Gawler Craton, South Australia

SHRIMP U-Pb geochronology and monazite EPMA chemical dating from the southeast Gawler Craton has constrained the timing of high-grade reworking of the Early Paleoproterozoic (ca 2450 Ma) Sleaford Complex during the Paleoproterozoic Kimban Orogeny. SHRIMP monazite geochronology from mylonitic and migmatitic high-strain zones that deform the ca 2450 Ma peraluminous granites indicates that they formed at 17252 and 17213 Ma. These are within error of EPMA monazite chemical ages of the same high-strain zones which range between 1736 and 1691 Ma. SHRIMP dating of titanite from peak metamorphic (1000 MPa at 730C) mafic assemblages gives ages of 17128 and 170812 Ma. The post-peak evolution is constrained by partial to complete replacement of garnet-clinopyroxene-bearing mafic assemblages by hornblende-plagioclase symplectites, which record conditions of 600 MPa at 700C, implying a steeply decompressional exhumation path. The timing of Paleoproterozoic reworking corresponds to widespread deformation along the eastern margin of the Gawler Craton and the development of the Kalinjala Shear Zone.