Geochemical investigations of microgranitoid enclaves in the S-type Cowra Granodiorite, Lachlan Fold Belt, SE Australia

Abstract

The Cowra Granodiorite is a relatively mafic, enclave-rich, S-type pluton in the Lachlan Fold Belt, which has been cited as a type example of a restitic origin for all varieties of enclaves in Lachlan Fold Belt S-type granites. Microgranitoid enclaves from the pluton are subordinate to metasedimentary varieties and can be subdivided into two groups according to their mafic mineral assemblage: pyroxene microtonalites and biotite microgranites. No geochemical or isotopic distinction can be made between the two varieties. Petrographic evidence (acicular apatites, xenocrysts from the host granite) suggests an origin as mingled, more mafic, magmas, which have been variably contaminated by the mor..