title: Geochemistry: how well can Pb isotopes date core formation?
abstract: Timescale and the physics of planetary core formation are essential constraints for models of Earth's accretion and early differentiation. Wood and Halliday use the apparent mismatch in core-formation dates determined from tungsten (W) and lead (Pb) chrono-meters to argue for a two-stage core formation, involving an early phase of metal segregation followed by a protracted episode of sulphide melt addition. However, we show here that crust-;mantle Pb isotope systematics do not require diachronous core formation. Our observations indicate that very early (< or = 35 Myr) core formation and planet accretion remain the most plausible scenario.
authors.affiliation: Department of Earth Sciences, Laurentian University, Sudbury, Ontario P31 6B5, Canada.
authors.forename: Balz S
authors.initials: BS
authors.lastname: Kamber
authors.forename: Jan D
authors.initials: JD
authors.lastname: Kramers