Pb, Nd, and Sr isotopes and REE systematics of Cambrian sediments from NewZealand: Implications for the reconstruction of the Early Paleozoic Gondwana margin along Australia and Antarctica

The Takaka Terrane of New Zealand's South Island contains a Middle to early Late Cambrian intraoceanic island are assemblage that consists of the terr igeneous to volcanogenic Haupiri Group sediments and the predominantly mafi c Devil River Volcanics. ph, Nd, and Sr isotopes, and major and trace eleme nt data are presented here for the Haupiri Group sediments. These data have implications for (1) the stratigraphy of the Takaka Terrane, (2) the recon struction of the Cambrian Gondwana margin along Australia/Antarctica, and ( 3) geochemical and isotope provenance studies in general. NJ. isotopes, Th/ Sc, and rare earth elements (REE) show that the volcaniclastic components i n the Haupiri Group, sediments reflect the concomitant island are and back- are volcanism. These sediments can probably be linked with the Early Cambri an Kanmantoo Group and Ordovician Lachlan Fold Belt sediments in SE Austral ia. To explain the Nd isotope compositions, published detrital zircon popul ations, and paleocurrent data, an Antarctic source with Grenvillian and Ros s-Delamerian age granitoids, as well as a significant portion of reprocesse d Paleo-proterozoic and/or Archean crust, is required. We adopt a bipolar s ubduction model for the Cambrian Gondwana margin along Australia/Antarctica and support the previous suggestion that the Cambrian are assemblages of t he Takaka Terrane of New Zealand and the Antarctic Bowers Terrane belong to the same are system with a paleogeographical position offshore the Antarct ic continent.