The cadmium and zinc isotope compositions of the silicate Earth – Implications for terrestrial volatile accretion

Zinc and Cd isotope compositions are presented for a comprehensive suite of terrestrial rocks to constrain the extent Zn fractionation during igneous processes better define ?66Zn ?114Cd values silicate Earth (the ? denote per mille deviations 66Zn/64Zn from JMC Lyon 114Cd/110Cd NIST SRM 3108 Cd). Analyses spinel lherzolites provide bulk (BSE) ?114CdBSE value –0.06 ± 0.03 ‰ (2SD). For Zn, peridotite data current previous studies mean ?66ZnBSE = 0.20 0.05 Komatiite analyses this published investigations yield similar values, which suggests that mantle remained fairly constant since Archean. Data loess upper continental crust 0.10 0.23 0.07 ‰. The abundance peridotites oceanic basalts in accord with observation array, having higher concentrations than peridotites. To first order, reflects slightly incompatible behaviour melting melt differentiation associated enrichment heavy isotopes phase. Cadmium is marginally more also display minor relative However, secondary produce significant variability both melts peridotites, obscuring primary array. estimates resemble CV CO carbonaceous some enstatite chondrites. In contrast, BSE has lower This implies composition was either fractionated accretion or Earth’s inventory not exclusively acquired material related Importantly, delivery solely by CI CM chondrites meteorite stable these elements.