In-situoxygen isotope records of crustal self-cannibalization selectively captured by zircon crystals from high-δ26Mg granitoids

Zircon oxygen-hafnium and biotite magnesium isotopic compositions of Late Cretaceous to Oligocene (88–27 Ma) granitoids from the Gyeongsang continental arc, southeastern Korea, collectively provide a new insight into shallow magma petrogenesis. Zircon crystals extracted from eight calc-alkaline or alkaline plutons commonly contain xenocrystic cores and typically show magmatic cathodoluminescence zonings and sharp Raman spectra. Most zircons have positive eHf values plotting below the mid-ocean-ridge basalt evolution path, indicating that the arc magmatism was dominated by the recycling of juvenile crustal materials. Zircon δ18O values shifted upward or downward from the mantle range attest to the O isotopic exchange of crustal protoliths with surface waters at various temperature conditions. Small (