British Antarctic Survey, C/O NERC Isotope Geosciences Laboratory, Keyworth, Nottingham NG12 5GG, UK.Council for Geoscience, PO Box 900, Pietermaritzburg, 3200, RSA.Department of Geology, University of Pretoria, Hillcrest, Pretoria, 0002, RSA.Now at Council for Geoscience, Private Bag X112, Pretoria, 0001, RSA.Geowissenschaften, Universitat Bremen, Postfach 330440, 28334 Bremen, Germany.British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 OET, UKCouncil for Geoscience, Private Bag X112, Pretoria, 0001, RSA.
Abstract
New Pb, Nd, and Sr isotope data are presented for geochemically similar, ∼1.1–1.2 Ga, granitoids and tonalitic‐granitic orthogneisses from Antarctica, southern Africa, and the Falkland Islands and adjoining plateau, areas originally within the supercontinents of Rodinia and Gondwana. These data support contentions for the presence of a Mesoproterozoic (∼1.2 Ga) destructive plate margin running from Namaqua‐Natal (southern Africa), through the displaced microplates of the Falkland Plateau and Falkland Islands, the Haag Nunatak crustal block (West Antarctica) and into western Dronning Maud Land (East Antarctica). The bulk of these granitoids represent juvenile Mesoproterozoic additions to the crust, except for in parts of East Antarctica (i.e., the Sverdrupfjella) where older (Paleoproterozoic or Archean) crust was involved in granitoid generation. Our isotope data permit plate reconstructions in which southern Africa, East Antarctica, and the Falkland Islands and plateau were adjacent within Rodinia.