Tungsten isotopes in eucrites revisited and the initial 182Hf/180Hf of the solar system based on iron meteorite data

We present a revised chronology for the formation and differentiation of the eucrite parent body based on 182Hf–182W chronometry. A very short (<600 kyr) time interval between metal segregation and silicate differentiation can be demonstrated. The non-cumulate eucrites formed 9.1±2.6 Myr after the start of the solar system. This is significantly later than recently proposed in the literature but in good agreement with Sr, Pb and Cr isotopic data. The comparison with Mg isotopes is complex and more data are required to discuss the consistency of the Al–Mg and the Hf–W chronometers. The Hf–W timescale is calibrated with a new estimate of the 182Hf/180Hf initial ratio of the solar system of (1.60±0.25)×10−4. This estimate, deduced from iron meteorite W isotope data, is about 50% higher than recently suggested.