GEOCHEMICAL EVIDENCE FOR PAIRED ARCS IN THE PERMIAN VOLCANICS OF SOUTHERN NEW-ZEALAND

Although remnants of a Permian volcanic arc in the South Island of New Zealand have hitherto been considered to comprise a single volcanostratigraphic unit, recent work in the southern part of the arc has revealed the presence of two lithologically distinct terranes, only one of which is definitely Permian in age. Major and trace element analyses of representative specimens show that these terranes are geochemically distinct. Comparison with modern volcanic arcs indicates that this ancient arc in the South Island was a paired arc system made up of primitive island arc tholeiites to the east and more evolved andesitic rocks to the west. © 1979 Springer-Verlag.