The effects of selective contamination on the early Paleozoic intracontinental mafic rocks in the South China Block: New insights from high-δ18O zircon

Abstract The petrogenesis of continental mafic rocks that are enriched in large-ion lithophile elements (LILE) and which have enriched Sr–Nd–Hf isotope compositions has long been controversial, with some models suggesting an enriched mantle source and others arguing for crustal contamination. Crustal contamination has generally not been favored as numerical models indicate that this would require the addition of significant amounts of crustal material. Here we present the first detailed study of the oxygen isotope composition of zircons from representative early Paleozoic mafic, intermediate, and felsic magmatic rocks in the South China Block (SCB), and combine this information with available geochemical data to re-examine whether crustal contamination or an enriched mantle source is the principal cause of the crustal geochemical signatures in these rocks. Zircon grains in the high-MgO mafic rocks (MgO > 8 wt%) with low eNd(t) values (