CAIs texture

On the other hand, fine-grained CAIs consist of aggregates of nodules with a concentric structure consisting of spinel cores surrounded by melilite, anorthite, and diopside, or melilite cores surrounded by anorthite and diopside (Fig. 7.5). The sequence of minerals in the nodules is consistent with a condensation sequence. However, the textures of the overall objects are complicated and often indicate extended and multistage histories. For... 

Figure 8.5 Different textural types of chondrules and a Type-B CAI shown in backscatter electron microscope images samples from A through D suffered increasing levels of heating (A) agglomeratic chondrules (scalebar 100 pm) (B) Type-IA (scalebar 100 pm) (C) Type-IIA (scalebar 100 pm) (D) compound barred chondrule set (scalebar 100 pm) (E) layered chondrules with fine grains (scalebar 500 pm) (F) a Type-B CAI (scalebar 1mm).

Figure 9 Combined elemental maps of (a) the C03.1 carbonaceous chondrite Kainsaz and (b) ungrouped CO/CM-like carbonaceous chondrite Acfer 094. Kainsaz contains abundant small chondrules, CAIs, and AOAs. Acfer 094 is texturally and mineralogically similar to CO chondrites, but contains higher abundance of matrix. AOA = amoeboid ohvine aggregate BO = barred olivine chondrule PO(P)i n = type I (II) porphyritic olivine (pyroxene) chondrule.

Olivine-rich, accretionary rims around CAIs, which have grain sizes >5-20 pm, were first described in the altered CV chondrite Allende by MacPherson et al (1985). In this meteorite, the accretionary rims have four layers that differ in texture and mineralogy. The innermost layer... 

Oxygen-isotopic compositions of aluminum-rich chondrules from CR and CH chondrites (Krot et al, 2003c) are plotted in Figure 15(b). Three out of six chondrules analyzed exhibit large internal-isotopic heterogeneity, whereas others are iso-topically uniform all chondrules have porphyritic textures. In contrast to aluminum-rich chondrules in ordinary chondrites, oxygen isotopic heterogeneity is due to the presence of relict CAIs (Krot and Keil, 2002). 

Matrix material is best defined as the optically opaque mixture of mineral grains 10 nm to 5 p.m in size that rims chondrules, CAIs, and other components and fills in the interstices between them (Scott et al, 1988). Matrix grains are generally distinguished from fragments of chondrules, CAIs and other components by their distinctive sizes, shapes, and textures. Minerals found in matrices include silicates, oxides, sulfides, metallic Fe,Ni, and especially in type 2 chondrites, phyllosilicates and carbonates (Table 5). Matrices are broadly chondritic in composition though richer in FeO than chondrules and have refractory abundances that deviate more from bulk chondrite values (McSween and Richardson, 1977 Brearley, 1996). Matrix typically accounts for 5 -50 vol.% of the chondrite (Table 1). 

The mineralogy of CAIs is commonly described in terms of what might be called primary and secondary minerals. Although useful, these terms are relative and potentially misleading. Primary refers to a phase that apparently formed when the inclusion itself first formed, for example, by direct condensation, melt solidification, or solid-state recrystallization. Secondary is a petrographic term for any phase that texturally appears to be replacing another phase e.g., one that not only mantles... 

Clear textural evidence for evaporation is surprisingly rare. In the case of most CAIs, for which evaporation has been suggested to modify elemental and isotopic compositions (Grossman et al., 2000), the CAI is believed to have been... 

What are the conditions in the early solar system that could produce significant evaporation of the CAIs The most studied CAIs are the type Bs. The characteristic coarse-grained igneous textures of these inclusions indicate a high degree of partial melting by a reheating event that raised... 

Further investigations of growing epitaxial layers on porous Si by LPCVD compared the growth on planar and textured substrates, which was carried out for APCVD by Kuchler et al. (2000). The porous Si layers were annealed at 1,050 °C for 30 min in H2 atm at a pressure of 3 x 10 Pa for the heat up period at a heat up slope of 10 ° C/min up to 1,100 ° C. Silane was used as a precursor gas and during deposition the pressure was kept below 100 Pa. A textured epitaxial Si layer with a weighted reflectance of 13.8 % was fabricated (Cai et al. 2010). 

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