Eucrites

Figure 8. Figure (a) after Clayton et al. (1976, 1977). The scales are as in Figure 1. The O isotopic compositions of the different meteorite classes are represented ordinary chondrites (H, L, LL), enstatite chondrites (EFl, EL), differentiated meteorites (eucrites, lAB irons, SNCs) and some components of the carbonaceous chondrites. As the different areas do not overlap, a classification of the meteorites can be drawn based on O isotopes. Cr (b) and Mo (c) isotope compositions obtained by stepwise dissolution of the Cl carbonaceous chondrite Orgueil (Rotaru et al. 1992 Dauphas et al. 2002), are plotted as deviations relative to the terrestrial composition in 8 units. Isotopes are labeled according to their primary nucleosynthetic sources. ExpSi is for explosive Si burning and n-eq is for neutron-rich nuclear statistical equilibrium. The open squares represent a HNOj 4 N leachate at room temperature. The filled square correspond to the dissolution of the main silicate phase in a HCl-EIF mix. The M pattern for Mo in the silicates is similar to the s-process component found in micron-size SiC presolar grains as shown in Figure 7.

Quitte G, Birck JL, Allegre CJ (2000) Hf- W systematics in eucrites the puzzle of iron segregation in the early solar system. Earth Planet Sci Lett 184 63-74... 

Srinivasan G, Goswami JN, Bhandari N (1999) A1 in eucrite Piplia Kalan plausible heat source and formation chronology. Science 284 1348-1350... 

Steele I. M. and Smith J. V. (1982). Ion probe analysis of plagioclase in three howardites and three eucrites. Geochim. Cosmochim. Acta, 42 959-971. 

It was soon discovered that there were other solar system objects that were older and had more primitive strontium than the basaltic achondrites. Table 8.3 compares the (87Sr/86Sr)o value determined for BABI with those from some other important samples from the early solar system. If Allende, Angra dos Reis, and the basaltic achondrites formed directly from the solar nebula, then the time intervals shown in the right-hand column of Table 8.3 are valid. Note that the uncertainties on these time intervals, a few million years, are much smaller than the uncertainty in the eucrite isochron shown in Figure 8.9 ( 260 Myr). However, the validity of the time intervals determined from the initial ratios depends completely on the validity of the idea that they all formed directly from the bulk material of the solar nebula. 

Blichert-Toft, J., Boyet, M., Telouk, P. and Albarede, F. (2002) 147Sm-143Nd and 176Lu-176Hf in eucrites and the differentiation of the HED parent body. Earth and... 

Patchett, P. J. and Tatsumoto, M. (1980) Lu-Hf total-rock isochron for eucrite meteorites. Nature, 288, 571-574. 

Shukolyukov, A. and Begemann, F. (1996) Pu-Xe dating of eucrites. Geochimica et Cosmochimica Acta, 60, 2454-2471. 

Shukolyukov, A. and Lugmair, G. W. (1993b) 60Fe in eucrites. Earth and Planetary Science Letters, 119, 159-166. 

Noncumulate eucrites (Init. Sr) Cumulate eucrites (Init. Sr)... 

Noncumulate eucrites whole-rock isochron (Rb-Sr) --------------------------- — Eucrites internal isochrons (Rb-Sr) -... 

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

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