Journal
EARTH AND PLANETARY SCIENCE LETTERS
Volume 482, Issue -, Pages 490-500Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.epsl.2017.11.034
Keywords
IAB iron meteorites; Hf-W chronometry; Pt isotopes; multi-collector ICP-MS; Planetesimals; thermal histories
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Funding
- European Research Council under the European Union's Seventh Framework Programme/ERC [279779]
- ETH Research Grant [ETH-17 13-1]
- Swiss National Science Foundation
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The short-lived Hf-182-W-182 decay system is a powerful chronometer for constraining the timing of metal-silicate separation and core formation in planetesimals and planets. Neutron capture effects on W isotopes, however, significantly hamper the application of this tool. In order to correct for neutron capture effects, Pt isotopes have emerged as a reliable in-situ neutron dosimeter. This study applies this method to IAB iron meteorites, in order to constrain the timing of metal segregation on the IAB parent body. The epsilon W-182 values obtained for the IAB iron meteorites range from -3.61 +/- 0.10 to -2.73 +/- 0.09. Correlating epsilon Pt-i with epsilon W-182 data yields a pre-neutron capture epsilon W-182 of -2.90 +/- 0.06. This corresponds to a metal-silicate separation age of 6.0 +/- 0.8 Ma after CAI for the IAB parent body, and is interpreted to represent a body-wide melting event. Later, between 10 and 14 Ma after CAI, an impact led to a catastrophic break-up and subsequent reassembly of the parent body. Thermal models of the interior evolution that are consistent with these estimates suggest that the IAB parent body underwent metal silicate separation as a result of internal heating by short-lived radionuclides and accreted at around 1.4 +/- 0.1 Ma after CAIs with a radius of greater than 60 km. (C) 2017 The Authors. Published by Elsevier B.V.
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