Читать книгу Isotopic Constraints on Earth System Processes - Группа авторов - Страница 35

Richter et al. (2017) ran laboratory experiments similar to those discussed in the previous section whose purpose was to document isotopic fractionation as lithium diffused into olivine. They found that lithium diffusion in olivine also resulted in large isotopic fractionations that were fit by model calculations with β _Li = 0.4 ± 0.1. Richter et al. (2017) used the same model calculations to fit lithium concentration and isotopic fractionation data that had been measured by Xiao et al. (2015) across a natural olivine grain from a peridotite xenolith from the Eastern North China Craton. The Xiao et al. (2015) lithium isotopic fractionation data can be fit using β _Li = 0.30 when lithium was assumed to occupy two sites in the olivine or with β _Li = 0.36 for lithium in just one site. The Xiao et al. (2015) data were not sufficiently detailed to distinguish whether lithium was in one or two sites, but the fact that the values β _Li that fit the isotope data in both cases are quite similar to those of the laboratory experiments is evidence that the diffusion of lithium did have a significant role in producing the zoning of the olivine grain studied by Xiao et al. (2015).