^(17)O anomalies in sedimentary silica and oxides

Abstract

Recent oxygen isotope measurements demonstrate small but significant deviations from a single mass dependent fractionation line among terrestrial materials [1, 2]. These anomalies confirm theoretical expectations of variation in the δ^(17)-δ^(18) relationship for equilibrium and kinetic isotope fractionations such that kinetic processes result in a relatively shallow slope (0.513) and equilibrium procesess result in a steeper slope (0.529) [3]. Here we present Δ^(17)O data for sedimentary silica and oxides, including cherts and banded iron formation (BIF) materials. We report Δ^(17)O relative to a reference line (δ^(17)O-δ^(18)O), slope 0.530 ± 0.003 (95% conf, MSWD = 1.07 [4]), that we produced from analysis of igneous and high-grade meta-igneous garnet, albite, pyroxene, olivine and quartz. This slope is higher than slopes previously generated for garnets (0.527 ± 0.001) and quartz (0.524 ± 0.001) in other laboratories [2], but within error of the slope predicted for equilibrium fractionation (0.529).

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