High precision iron isotope measurements of terrestrial and lunar materials

摘要: We present the analytical methods that have been developed for first high-precision Fe isotope analyses clearly identify naturally-occurring, mass-dependent fractionation. A double-spike approach is used, which allows rigorous correction of instrumental mass Based on 21 an ultra pure standard, external precision (1-SD) measuring isotopic composition ±0.14 ‰/mass; demonstrated reproducibility samples, this exceeds by at least order magnitude previous attempts to empirically control instrumentally-produced fractionation (Dixon et al., 1993). Using method, 15 terrestrial igneous rocks range in from peridotite rhyolite, 5 high-Ti lunar basalts, Fe-Mn nodules, and a banded iron formation analyzed their composition. The same compositions as providing reference Earth Moon. In contrast, nodules sample vary over relatively wide range, δ56Fe = +0.9 −1.2 ‰; times errors our technique. These natural fractionations are interpreted reflect biological (“vital”) effects, illustrate great potential studies studying modern ancient processes.