The source of A-type magmas in two contrasting settings U–Pb, Lu–Hf and Re–Os isotopic constraints.pdf

Chemical Geology 351 (2013) 175–194 Contents lists available at SciVerse ScienceDirect Chemical Geology journal homepage: www. else vi er. com/ locate /chemgeo The source of A-type magmas in two contrasting settings: U–Pb, Lu–Hf and Re–Os isotopic constraints M.J. Pankhurst a,⁎, B.F. Schaefer a, S.P. Turner a, T. Argles b, C.E. Wade c a Australian Research Council Centre of Excellence GEMOC, Macquarie University, Sydney 2109, Australia b Department of Earth and Environmental Sciences, The Open University, Milton Keynes MK7 6AA, UK c Geological Survey of South Australia, Department for Manufacturing, Innovation, Trade, Resources and Energy (DMITRE), GPO Box 1264, Adelaide, South Australia 5001, Australia a r t i c l e i n f o a b s t r a c t Article history: The sources of post-orogenic A-type magmas from two distinct geodynamic settings are compared. The end Received 28 January 2013 of the ca. 514–480 Ma Delamerian Orogeny, southeastern South Australia, was marked by ~10 Myr of bimod- Received in revised form 10 May 2013 al A-type magmatism, driven by convective removal of thickened lithosphere. Initial Os and Hf isotope ratios Accepted 14 May 2013 record a heterogeneous lithospheric mantle source, with some input from aesthenospheric mantle. Mafic pa- Available online 25 May 2013 rental melts fractionated to produce the granites. In contrast, initial Os isotope ratios of the A-type magmas Editor: David R. Hilton that comprise the ca. 1