Early Permian supra-subduction assemblage of the South Island terrane, Percy Isles, New England Fold Belt, Queensland

Ultramafic-intermediate rocks exposed on the South Island of the Percy Isle s have been previously grouped into the ophiolitic Marlborough terrane of t he northern New England Fold Belt. However, petrological, geochemical and g eochronological data all suggest a different origin for the South Island ro cks and a new terrane, the South Island terrane, is proposed. The South Isl and terrane rocks differ from ultramafic-mafic rocks of the Marlborough ter rane not only in lithological association, but also in geochemical features and age. These data demonstrate that the South Island terrane is genetical ly unrelated to the Marlborough terrane but developed in a supra-subduction zone environment probably associated with an Early Permian oceanic arc. Th ere is, however, a correlation between the South Island terrane rocks and i ntrusive units of the Marlborough ophiolite. This indicates that the two te rranes were in relative proximity to one another during Early Permian times . A K/Ar age of 277 +/- 7 Ma on a cumulative amphibole-rich diorite from th e South Island terrane suggests possible affinities with the Gympie and Ber serker terranes of the northern New England Fold Belt.