U-Pb zircon studies of mid-crustal metasedimentary enclaves from the S-type Deddick Granodiorite, Lachlan Fold Belt, SE Australia

High-grade metasedimentary, enclaves in granites can be used to directly ch aracterize the lower and mid crust. Enclaves in the Silurian S-type Deddick Granodiorite,SE Australia, have chemical and Nd-Sr isotopic compositions b roadly similar to Ordovician-Silurian clastic sedimentary, rocks throughout the fold belt. SHRIMP U-Pb ages of detrital zircons in the enclaves indica te Early Ordovician maximum depositional ages for their psammitic-pelitic p recursors. Patterns of zircon inheritance show the same similar to 500 and 1100 1200 Ma peaks commonly observed in Palaeozoic Gondwana margin sediment ary, sequences in eastern Australia, New, Zealand and East Antarctica. U-Pb ages for metamorphic zircon rims and Sin-Nd dating of garnet indicate that metamorphism in enclave precursors was coeval with granitic magmatism at s imilar to 430 Ma. The enclaves represent metamorphic equivalents of the vol uminous Lachlan Fold Belt Palaeozoic turbidites. After tectonic transport t o the mid crust and attendant amphibolite-facies metamorphism during the Be nambran Orogeny (440-430 Ma), these Palaeozoic metasediments became the sou rces for extensive Silurian magmatism. S-type granite magmas in the eastern Lachlan Fold Belt are therefore derived from Ordovician turbidites with po ssible contributions from Cambrian volcano-sedimentary ('greenstones') sequ ences and from contemporaneous, mantle-derived magmas.