Grossular

All of the Type A and B inclusions studied are surrounded by a layered rim sequence of complex mineralogy [21] which clearly defines the inclusion-matrix boundary. Secondary alteration phases (grossular and nepheline, especially) are also a common feature of these inclusions, suggesting that vapor phase reactions with a relatively cool nebula occurred after formation of inclusions. Anorthite, in particular, is usually one of the most heavily altered phases the relationship between Mg isotopic composition and alteration is discussed below. (See [12] for striking cathodoluminesce photographs of typical Allende alteration mineralogy.) Inclusion Al 3510 does not fit the normal pattern as it has no Wark-rim and does not contain the usual array of secondary minerals. 

The Type A melilite data also reinforce earlier arguments about the absence of any connection between mineralogical alteration and Mg isotopic behavior. Melilites in 3529-45 are extensively altered, mainly to grossular and Na-rich plagioclase, yet show much less evidence for a disturbed Mg isotopic composition than relatively pristine melilites from B1 inclusions. B1 melilites exhibit much larger deviations from the standard isochron than anorthites (see also [1]). 

Broadband LIBS spectra for three garnet types - the Mg-AI pyrope type, the Ca-AI grossular type, and the Mn-AI spessartine type are shown in Figure 1. 

Fig.1. Example broadband LIBS spectra for a pyrope, grossular, and spessartine garnet. The clear differences observed in the broadband spectra reflect the chemical differences in the composition of the three garnets.

Fig. 5. Confusion matrix for the HDPCA analysis of the four grossular garnets. The nth row and column correspond to the nth grossular type truth and HDPCS statistical assignment, respectively.

Leitner et al. (1980) showed that the bulk moduli of terms of pyrope-almandine-grossular and andradite-grossular mixtures vary with chemical composition in a perfectly linear fashion (within the range of experimental incertitude). This behavior is also implicit in the generalization of Anderson (1972). 

Table 5.24 lists selected data concerning entropy and isobaric heat capacity, covering andradite, grossular, pyrope, and almandine terms, compared with results of calculations based on the Kieffer model (Ottonello et al., 1996). 

Figure 11.30 Reduced partition function for various minerals calulated by Kieffer (1982) through equation 11.61 plotted against T. Heavy curve labeled H20(l) is reduced partition function of water according to Becker (1971). Dashed curve is a extrapolation of high-r reduced partition curve for quartz. Mineral abbreviations Qtz (quartz), Calc (calcite), Albt (albite), Muse (muscovite), Enst (clinoenstatite), Anor (anorthite). Diop (diopside), Pyrp (pyrope), Gros (grossular), Zron (zircon), Fors (forsterite), Andr (andra-dite), Rutl (rutile). Reprinted with permission from Kieffer (1982), Review of Geophysics and Space Physics, 20, 827-849, copyright 1982 by the American Geophysical Union.

Bass X D. (1989). Elasticity of grossular and spessartite garnets by Brillonin spectroscopy. J. Geophys. Res., 94 7621-7628. 

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