Chondrules definition

The post-crystallization regime for Fe,Mg-rich chondrules is essentially quantitatively unconstrained. However, the presence of glassy mesostasis and fractionated element abundances within chondrule phases indicates that most chondrules definitively did not experience prolonged heating after they were cooled and quenched. 

The O isotopes show signihcant heterogeneity between the different meteorite classes (Fig. 8a Clayton et al. 1976, 1977). Differences are small, but, each chondrite group has a distinct bulk O isotopic composition. O isotopes also indicate the close ties between the Earth and the Moon. O therefore can be used to identify members of a family that formed from a common reservoir, which is the definition of a tracer. Such differences are also formd between chondrules within the same meteorites related to their size (Gooding et al. 1983). This is a survival of the initial isotopic heterogeneity in already high temperature processed materials like chondrules. 

Trapped and cosmogenic noble gases in chondrules offer clues to their irradiation history and formation but not definitive constraints (see Chapter 1.14). Trapped noble gases are generally absent or rare in chondrules, but significant amounts of trapped Ar, Kr, and Xe from a... 

The analysis of the statistical or preferred orientation of the crystallites in solid polycrystaUine materials is commonly referred to as texture analysis. Again, the diffraction technique allows the definition of the relationship between a microscopic property, i.e. the orientation of the crystallites defined as coherent diffraction domains, and the macroscopic physical properties of the crystal aggregate. Texture studies are of course crucial in the characterization of oriented synthetic materials such as cold-rolled metals or oxide thin films, but they are also of great relevance in the study of the formation processes of mineral assemblages. As an example, the texture features of olivine or pyroxene minerals in meteoritic chondrules yield information on the early condensation sequence... 

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