The triple oxygen isotope composition of the Earth mantle and understanding variations in terrestrial rocks and minerals

It has been shown in numerous studies that terrestrial rocks and minerals fall on a line with slope ∼0.52 in a δ O 17 vs. δ O 18 diagram. In this study, we present new data on the triple isotope composition of the Earth mantle, crustal materials and low-T aqueous precipitates. Crustal materials show distinct variations in Δ O 17 suggesting that the concept of a single terrestrial mass fractionation is invalid on small-scale. Observable variations in individual fractionation slopes θ are interpreted as temperature effects. We show that the Earth mantle is isotopically homogeneous and confirm the recent finding that the Earth mantle has a negative Δ O 17 . The difference in δ O 18 and Δ O 17 between seawater and oceanic crust is discussed with respect to the effects of low- and high-temperature water–rock interaction.