Accretion of Primitive Planetesimals: Hf-W Isotopic Evidence from Enstatite Chondrites

Abstract
Enstatite chondrites have often been considered to be closely related to the material from which Earth accreted. However, tungsten isotopic data reveal clear differences. Moreover, the silicate and metal fractions define distinct initial 182 Hf/ 180 Hf corresponding to a 13.8 ± 5.3 million year apparent age difference. Internal reequilibration does not provide a ready explanation for this result. Larger scale redistribution of tungsten is more likely, such as may have occurred during collisions between planetesimals.