Hf-W chronology of the eucrite parent body

Abstract : The Hf-182-W-182 systematics of 12 whole-rock eucrites, including basaltic and cumulate samples, have been investigated. The Hf-W isotope systematics of both basaltic and cumulate eucrites are consistent with derivation from a single mantle source characterized by a strongly suprachondritic Hf/W ratio (Hf-180/W-184 of similar to 19). The elevated Hf/W of this mantle source was established by core formation within similar to 1 Ma after CAI formation or, alternatively, represents that of the residual melt of a magma ocean from which the eucrites ultimately formed. In the latter case the time of core formation is more uncertain and core formation may have occurred slightly later than similar to 1 Ma. The investigated basaltic eucrites fall into three distinct age groups with Hf-W ages of similar to 4 Ma (Stannern), similar to 11 Ma (Bereba, Bouvante) and similar to 22 Ma (Camel Donga, Juvinas) after CAI formation and provide evidence for a protracted history of magmatism and crustal metamorphism on the eucrite parent body, lasting for at least similar to 20 Ma. Evidence for even later activity is provided by the cumulate eucrites, which exhibit only small if any variations in W-182/W-184 in spite of variable Hf-180/W-184, indicating cooling below the Hf-W closure temperature when Hf-182 was nearly extinct. On the basis of three cumulate eucrites, a Hf-W age of 38 +/- 21Ma is inferred, but even younger ages would also be consistent with the Hf-W data. (C) 2015 Elsevier Ltd. All rights reserved.
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Mathieu Touboul, Peter Sprung, Sarah M. Aciego, Bernard Bourdon, Thorsten Kleine. Hf-W chronology of the eucrite parent body. Geochimica et Cosmochimica Acta, 2015, 156, pp.106-121. ⟨10.1016/j.gca.2015.02.018⟩. ⟨hal-02341061⟩

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