Highly siderophile element composition and Re-Os age of Cretaceous oceanic crust

Abstract

To understand the chemical composition of the whole oceanic crust and magmatic processes beneath mid-ocean ridges, it is essential to investigate deeper lithologies of mature oceanic crust. In this study, we report highly siderophile element (HSE) compositions and whole-rock Re-Os isochron ages for ten mafic xenoliths collected from a petit-spot volcano in the northwestern Pacific. Os, Ir, Ru, and Pt show positive correlations with Mg#, whereas Re exhibits a negative correlation, preserving the signature of the crystal fractionation trend. The obtained Re-Os isochron age of ~140 Ma is consistent with the paleomagnetic age of the oceanic crust below the petit-spot volcano, suggesting that the xenoliths are fragments of the Cretaceous oceanic crust formed through a series of magmatism at the mid ocean ridge. Our data provide new constraints on the behavior of HSEs during oceanic crust formation, which has remained poorly understood.