Olivine Oxygen Isotope Evidence for Intracontinental Recycling of Delaminated Continental Crust

Abstract

AbstractThis paper reports the oxygen isotope compositions of olivine from dunite, wehrlite, harzburgite, and lherzolite xenoliths entrained by the Early Cretaceous high‐Mg diorites and Late Cretaceous basalts in the central and eastern North China Craton, with the aim of constraining processes that happened in the lithospheric mantle. Olivine oxygen isotope compositions were analyzed in situ using secondary ion mass spectrometry. Olivine δ18O of harzburgite and lherzolite xenoliths hosted in the Fushan and Tietonggou diorites with Archean and Paleoproterozoic rhenium‐depletion model ages ranges from 5.1‰ to 5.8‰, similar to olivine from spinel lherzolite xenoliths in the Late Cretaceous Fuxin basalts (olivine δ18O = 5.2–5.4‰) and typical mantle olivine. In contrast, olivine δ18O from dunite and wehrlite xenoliths ranges from 6.1‰ to 7.7‰, significantly higher than the typical mantle values. The olivine oxygen isotope data, combined with the petrologic observations, mineral compositions, and whole‐rock trace element and Sr‐Nd‐Os isotope compositions of the peridotite, suggest that the peridotites in Early Cretaceous high‐Mg diorites had been affected by interaction with melt derived from delaminated continental crust. These data provide compelling evidence for the recycling of continental crust in an intracontinental setting.