AOAs composition

Bulk chemical compositions of CAIs, AOAs, and chondrules, compared to trends for calculated total condensed solids formed by equilibrium condensation of a hot solar gas at two different pressures. Condensed minerals are corundum (Cor), hibonite (Hib), end members of melilite series gehlenite (Geh) and akermanite (Ak), anorthite (An), diopside (Di), and forsterite (Fo). Modified from MacPherson etal. (2005). 

The most primitive chondrites consist of coarse-grained (mm-sized) mineral assemblages embedded in fine-grained (10 nm-5 pm) matrix material (see Fig. 1.2). The coarse-grained chondritic components are diverse in their composition and mineralogy and include calcium-aluminum-rich inclusions (CAIs), amoeboid olivine aggregates (AOAs), Al-rich chondrules, Fe-Mg chondrules, Fe-rich metals, and iron sulfides. The CAIs are composed largely of calcium, aluminum, and titanium... 

Another argument that the 0-rich end-member was a ubiquitous component of primitive solids is that it is found in many different chemical forms (different minerals) in many classes of meteorites CAls and amoeboid olivine aggregates (AOAs) from Efremovka (CV3) (Aleon et al., 2002 Fagan et al., 2002), AOA from a CO chondrite, Y 81020 (Itoh et al, 2002), and CAl and AOA from CM and CR chondrites (Krot et al., 2002). This isotopic composition can also serve as an end-member for the chondrule mixing line in Figure 2. 

Figure 11 Compositions of olivine in AO As from the reduced CV chondrites Vigarano (a), Leoville (b), Efremovka (c), oxidized CV chondrite Allende (d), CR chondrites (e), CH and CB chondrites (f), unique carbonaceous chondrites Adelaide (g), and Acfer 094 (h). Olivines in CRs, Adelaide, and Acfer 094 are magnesium-rich compared to olivines in CV AO As. Fayalite contents in olivines from CV AO As increase in the order Leoville and Vigarano, Efremovka, Allende this is correlated with the degree of secondary alteration and thermal metamorphism experienced by CV chondrites. Data for Allende AO As are from Hashimoto and Grossman (1987) and for Efremovka, Leoville, and Vigarano AOAs from Komatsu et al (2001).

A The relationship between chondrules, CAIs, and AOAs The contrasting mineralogy of CAIs and chondrules indicates that they formed at different nebular temperatures and perhaps in different nebular environments. This is confirmed by oxygen isotope studies which show that there are significant oxygen isotope compositional differences between chondrules and refractory CIAs and AOAs. Chondrules from C and O chondrites also have different oxygen isotope compositions and appear to have formed in different nebular environments. In contrast, CAIs from all chondrite types and AOAs are isotopically similar and share the... 

It occurs in white or grayish, amorphous masses odorless . alkahne caustic almost infusible sp. gr. 2.3. With HaO it gives off great heat and is converted into the hydroxid (slacking). In iiir it becomes air-slacked, falling into a white powder, having the composition CaCOs.CaH-aOa. 

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