The triple oxygen isotope composition of the Earth mantle and understanding ΔO17 variations in terrestrial rocks and minerals

- We present a new technique for high-precision triple isotope analyses of rocks and minerals.
- We present new data on reference materials, the Earth and various crustal rocks.
- We present a new framework for understanding and utilization of triple isotope measurements in terrestrial rocks.

It has been shown in numerous studies that terrestrial rocks and minerals fall on a line with slope ∼0.52 in a δO17 vs. δO18 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 ΔO17 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 ΔO17. The difference in δO18 and ΔO17 between seawater and oceanic crust is discussed with respect to the effects of low- and high-temperature water-rock interaction.