Highly siderophile element composition of the Earth’s primitive upper mantle: Constraints from new data on peridotite massifs and xenoliths

Highly siderophile element and 182 W evidence for a partial late veneer in the source of 3.8 Ga rocks from Isua, Greenland

“…1) (Becker et al, 2006), and are higher than all known chondrite types. Given the debate on the interpretation and reliability of the BSE Ru/Ir and Pd/Ir fractionations (e.g.…”

“…In contrast to the basaltic samples, ultramafic samples have broadly chondritic relative HSE abundances, with absolute concentrations that fall at the low end or below the range of modernday peridotites, at 40 to 75% of the estimate for the BSE (Becker et al, 2006) …”

“…Os, Pt, Re, Au) in Earth's mantle, which are higher than expected for metal-silicate equilibration during core formation (Brenan and McDonough, 2009;Mann et al, 2012). Moreover, the HSE in the mantle occur in broadly chondritic relative proportions, which is unexpected for metal-silicate partitioning (Meisel et al, 1996;Becker et al, 2006). These observations have led to the idea that the elevated HSE abundances in Earth's mantle reflect the late addition of broadly chondritic material (the 'late veneer') to the mantle after core formation was complete (e.g.…”

Modeling fractional crystallization of group IVB iron meteorites

“…The chemical-separation techniques used in this study for Re-Os isotopic analysis and isotope dilution analysis of Ir, Ru, Pt and Pd have been previously published (Shirey and Walker, 1995;Rehkämper and Halliday, 1997;Cook et al, 2004;Becker et al, 2006 Ru,194 Pt and 105 Pd, approximately 4 g of concentrated HNO 3 and 2 g of concentrated HCl were frozen into quartz or Pyrex TM Carius tubes, sealed and heated at 240°C for more than 24 h to obtain complete sample-spike equilibration. Osmium was purified using a carbon tetrachloride (CCl 4 ) solvent extraction technique (Cohen and Waters, 1996) follow by microdistillation purification (Birck et al, 1997).…”

Late accretion history of the terrestrial planets inferred from platinum stable isotopes

“…However, if the core formed under these conditions, the Pt depletion in the pre-late-veneer mantle would be significantly reduced (e.g., Pt ~ 0.1 ng g -1 in pre-late-veneer mantle as compared with ca. 7 ng g -1 in the primitive upper mantle; Becker et al, 2006), and a combination of high-pressure and -temperature core formation with a chondritic late-veneer can explain both the Pt concentrations and Pt stable isotope data. Mixing calculations modelling the effect of addition of chondritic late-veneer (with δ 198 Pt ~ -0.14 ‰ and 1 µg g -1 Pt) to a hypothetical pre-late-veneer mantle can reproduce our Pt isotope and concentration data for Isua and post-Archean mantle if we assume a pre-late-veneer mantle with 0.14 ng g -1 Pt (using partition coefficients for core formation at high-pressure and -temperature), Pt isotopic fractionation during core formation of ~4 ‰, and a final amount of late-veneer equating to 0.5 wt.% of Earth's mass ( Fig.…”