In the endogenous scenario, metal and silicates both originate from the same parent body. The 3D-connected structure of the metal observed by microtomography is attributed to complete melting of the metal–sulfide phase and incipient melting of the silicate phase. Indeed, the Fe–FeS eutectic at 1 bar is about 1260 K (Usselman, 1975). Some tens of degrees above this LCZ696 eutectic, silicates also start to melt and a basaltic liquid forms, at temperatures close to the ones of experimentally determined incipient melting of CR chondrites (<1400 K, Usui et al., 2010). Such temperatures may be compared to those inferred by Galy et al. (2012) for chromite equilibration (1450–1720 K) and to the temperatures proposed by Gardner-Vandy et al. (2012) for the two-pyroxene thermometer (1346±37 K1346±37 K) in Tafassasset. A formation scenario could be: the Tafassasset parent body accreted within the first million years of the solar system, with a composition similar to that of CR chondrites. Internally heated by the radioactive decay of short-lived nuclides, its temperature increased and reached a peak (1350–1400 K). These values correspond to 20–25% melting of a Fe-rich carbonaceous chondrite as predicted by the MELTS thermodynamic calculator (Asimow and Ghiorso, 1998 and Ghiorso and Sack, 1995). Such partial melting is consistent with the extent of pockets of molten material (see below) added to the lost basaltic component (Nehru et al., 2003 and Nehru et al., 2010). Further details of the MELTS calculations can be found in Appendix A2.
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