Accretion and differentiation of achondritic parent bodies

Until recently, it was generally believed that the chondrites, which consist of relatively unaltered nebular material and thus are primitive objects, accreted early, whereas the differentiated meteorites (achondrites, irons, pallasites), which have had a history of melting 

5 Myr after CAIs (Lugmair and Shukolyukov, 1998). High-precision 26Al-26Mg studies of eucrites and diogenites indicate that extensive melting and differentiation occurred 

5 Myr after CAIs formed (Bizzarre et al., 2005). Taken together, these data imply that differentiation and crust formation began on the HED parent body 2.5-3 Myr after CAIs formed (Fig. 9.9). This, in turn, implies very rapid accretion, heating, and melting in Vesta, probably within 1 Myr of the origin of the solar system. 

Chronology of the solar system from radioactive isotopes 

The LAB-IIICD irons are non-magmatic irons that often contain silicate inclusions. Tungsten is significantly more radiogenic in these meteorites than in the IIAB irons because 

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