Pankhurst, M.J.Schaefer, B.F.Turner, S.P.Argles, T.Wade, C.E.2019-02-072019-02-072013Chemical Geology, 2013; 351:175-1940009-25411872-6836http://hdl.handle.net/2440/117659The sources of post-orogenic A-type magmas from two distinct geodynamic settings are compared. The end of the ca. 514–480 Ma Delamerian Orogeny, southeastern South Australia, was marked by ~ 10 Myr of bimodal A-type magmatism, driven by convective removal of thickened lithosphere. Initial Os and Hf isotope ratios record a heterogeneous lithospheric mantle source, with some input from aesthenospheric mantle. Mafic parental melts fractionated to produce the granites. In contrast, initial Os isotope ratios of the A-type magmas that comprise the ca. 1598–1583 Ma Mesoproterozoic Gawler Felsic Large Igneous Province, central South Australia, record a dominant evolved lower crust component. However, initial Hf isotope ratios from these samples are depleted, indicating a mantle source for lithophile elements. This voluminous, bimodal magmatism lasted for ~ 15 Myr, and ended the Wartakan Orogeny. In both cases the homogenisation of chemical (rheological) heterogeneities, inherited from terrain amalgamation and orogenic thickening, strengthened the lithosphere. The contemporaneous fusion of heterogeneous mantle ± crust may represent a common, stabilising influence on the lithospheric column regardless of tectono-magmatic setting.en© 2013 Elsevier B.V. All rights reserved.Re-Os isotopes; A-type; Lu-Hf isotopes; post-orogenic; geodynamics; lithospheric stabilisationJournal article003010166410.1016/j.chemgeo.2013.05.0100003228575000142-s2.0-84879009232445223Wade, C.E. [0000-0003-2569-2771]