182Hf-182W isotope systematics of chondrites, eucrites, and martian meteorites: Chronology of core formation and early mantle differentiation in Vesta and Mars

Nucleosynthetic Tungsten Isotope Anomalies in Acid Leachates of the Murchison Chondrite: Implications for Hafnium-Tungsten Chronometry

“…The weighted average of the W isotopic compositions of the leachates agrees with the bulk measurement (e.g., Kleine et al 2004), indicating that all important nucleosynthetic W isotope components have been tapped by the leaching experiment. (Arlandini et al 1999), but has a slightly shallower slope than that predicted by this model (Figure 2(a) (Burkhardt et al 2008), the slope of the ε 182 W i -ε 183 W correlation becomes slightly steeper than that obtained from the stellar model (Figure 2(b)).…”

“…The insoluble residue (L6) left after acid treatment was fused with a CO 2 laser, to ensure complete dissolution of all remaining presolar grains (see Burkhardt et al 2011). All samples were digested in acids (aqua regia for L1-L5; HNO 3 -HF-HClO 4 for L6) and W was purified from these samples by anion exchange chemistry in HCl-HF media (Kleine et al 2004). All W isotope measurements were performed by multicollector inductively coupled plasma mass spectrometry at ETH Zurich.…”

Tungsten Nuclear Anomalies in Planetesimal Cores

“…A few drops of HClO 4 were added, and the solution was evaporated at $200 C to get rid of carbon compounds from the sample and resin. Further purification was achieved through a series of anionexchange columns in HCl-HF medium, following the procedure of C. N. Foley (2005, personal communication) from Mü nker et al (2001) and Kleine et al (2004). A precleaned Savillex Teflon microcolumn (I:D: ¼ 6:4 mm) was filled with 2 mL (wet) AG1-X8 200Y400 mesh chlorine-form resin.…”

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

“…All chondrite groups and iron meteorites show deficits in 182 W relative to the BSE, so any late veneer would have added 182 W-depleted material to the BSE. Based on available W concentration and 182 W data (Yin et al, 2002;Kleine et al, 2004;Kleine et al, 2008;McCoy et al, 2011;Kruijer et al, 2014) and HSE data from the same samples (Table S3) (Horan et al, 2003;Fischer-Gödde et al, 2010), we calculate that subtracting an ordinary, enstatite or carbonaceous chondrite-like late veneer fraction not present in Isua's source (i.e., ~35-50%) from the present-day BSE composition would produce ε 182 W excesses for Isua of +0.04 0.02 -…”

“…During core formation, lithophile Hf separated from moderately siderophile W, causing Hf/W fractionation which, following decay of 182 Hf, led to distinct 182 W signatures in the mantle and core of planetary bodies. For instance, the present-day bulk silicate Earth (BSE) exhibits a higher 182 W/ 184 W by ~2 ε-unit (1ε = 0.01%) relative to chondrites, indicating that at least some part of Earth's core formed during the lifetime of 182 Hf (Kleine et al, 2002;Schoenberg et al, 2002;Yin et al, 2002;Kleine et al, 2004). The 182 W/ 184 W difference between Earth's mantle and chondrites not only provides constraints on the timing of core formation, but can also be used as a tracer of lateaccreted material.…”