The Hohonu Batholith of North Westland, New Zealand: Granitoid compositions controlled by source H2O contents and generated during tectonic transition

Abstract

Geochemical studies on the Hohonu Batholith, of the West Coast, South Island, New Zealand, have recognised two distinct but chemically related suites of mid-Cretaceous granitoids. The suites are characterised by restricted radiogenic isotopic compositions (Sr(i) = 0.7062 to 0.7085; εNd(i) = -4.4 to -6.1), and represent melting of a mafic lithosphere source followed by interaction with Ordovician metasediments. The two suites (Te Kinga Suite and Deutgam Suite) are distinguished by contrasting contents of Al2O3, Na2O, Sr, Ba, Eu and HREE, attributable to different residual assemblages controlled by differing H2O contents during melting of a metabasaltic source. The relatively mafic, metalumino..