Compositional zoning

Wide compositional zoning and heterogeneity in a tetrahedrite-tennantite grain are common (Yamaoka, 1969 Yui, 1971 Yamaoka and Nedachi, 1978a). 

Compositional zoning in electrum grain is common (Shimazaki, 1974 Imai et al., 1981). The Ag content of rim of electrum grain is higher than that of core. Although Ag content varies widely, it is generally lower than that of epithermal vein-type deposits. 

Yamaoka, K. and Nedachi, M. (1978a) Compositional zoning of tetrahedrite from Kuroko deposits. Abst. Assoc. Mineral., Petrol., Econ. Geol., 93 (in Japanese). 

No compositional zoning in sphalerite grain is observed, suggesting original zoning has been homogenized by thermal metamorphism (Mizuta, 1988). 

Aluminium distribution in A and B1 intermediate and final phases Various compositional zonings have been reported in silica-rich ZSM-5 zeolites prepared under particular conditions (11-13,19,26, 27,31,32,59,68) while other studies provided evidence for homogeneous A1 distribution throughout the crystallites (69-71). Obviously, the distribution of aluminium in ZSM-5 must depend on its mechanism of crystallization. 

These systems were referred to by Clausse t a (21) as Type U systems. On the other hand, with cofurfactants with chain length Cg to Cy (Figur 3 e-g), the Winsor IV domain is split into two disjointed areas that are separated by a composition zone over which viscous turbid and birifringent media are encountered. This second class of systems was referred as Type S systems (24). It can also be seen that the Winsor IV domain reaches its maximum extension at reducing in size below and above C. Moreover, at C, one observes a small monophasic region near the W apex (probably o/w microemulsion of the Schulman s type) which vanishes as the alcohol chain length is increased to Cg. 

Figure 6.2 represents the behavior of quasi-monodisperse double emulsions in (C , (pf) coordinates, where (pf is the initial volume fraction of droplets in the globules. Sorbitan monooleate (SMO) was used for the stabilization of the primary W/O emulsion and sodium dodecyl sulfate (SDS, CMC = 8 10 mol/1) was used for the stabilization of the oil globules in the external aqueous phase. Three different compositions zones, referred to as A, B, and C can be defined they differ by their qualitative behavior observed via microscopy. Moderate internal droplet volume fractions are considered first (cpf < 20%). If Ck = CMC/10, the system does not exhibit any structural evolution after a few days of storage (zone A). If C is... 

Frondel, C. (1985). Systematic compositional zoning in the quartz fibers of agates. Amer. Min. 70 975—979. 

This study has been conducted with the objectives 1) to analyze and determine the effect of the free convective mixing in the melted zone upon the over-all solute transfer process in zone refining under various conditions and 2) to take into account the solute transfer both in the melted zone and in the adjacent P.S.Z. (mushy region) in predicting the rate of over-all solute transfer. The temperature distribution, composition, zone travel speed, zone dimension and other important parameters are considered in this study. 

Some minerals display miscibility gaps. If the boundary between two compositional zones corresponds to a miscibility gap, then there will be both partitioning and diffusion across the boundary. Because the miscibility gap widens as temperature decreases, the concentrations on the two sides are further separated rather than smoothed out. Figure 5-25b shows a hypothetical example. Wang et al. (2000) used this property to make the first direct observation of immisci-bility in garnet. 

Ganguly J., Yang H., and Ghose S. (1994) Thermal history of mesosiderites quantitative constraints from compositional zoning and Fe-Mg ordering in orthopyroxenes. Geochim. Cosmochim. Acta 58, 2711-2723. 

Ganguly J., Dsasgupta S., Cheng W., and Neogi S. (2000) Exhumation history of a section of the Sikkim Himalayas, India records in the metamorphic mineral equilibria and compositional zoning of garnet. Earth Planet. Sd. Lett. 183, 471-486. 

Loomis T.P. (1983) Compositional zoning of crystals a record of growth and reaction history. In Kinetics and Equilibrium in Mineral Reactions (ed. S.K. Saxena), pp. 1-59. New York Springer-Verlag. 

W. J. Staudt, R. J. Reeder, and M. A. A. Schoonen, Surface structural control on compositional zoning of SO and SeO in synthetic calcite single crystals, Geochim. 

Helderberg carbonates are extensively cemented by clear equant calcite cement that postdates marine cement and fills most of the original pores. These cements are compositionally zoned as shown by cathodoluminescence and trace element analyses. These precipitates include nonluminescent, bright and dull cements. The luminescent cement is the earliest generation of cement followed by... 

Microprobe analysis of HZSM-5 samples from a Li-NH -TPA system (sample A), see Figure 7, gave rise to a characteristic compositional zoning of A1 in the outer rim of the crystals. HZSM-5 from alkaline-free processes (sample B), see Figure 8, had a more homogeneous aluminium distribution throughout the crystals. 

Brearley A. J., Hutcheon I. D., and Browning L. (2001) Compositional zoning and Mn-Cr systematics in carbonates from the Y791198 CM2 carbonaceous chondrite. In Lunar Planet. Sci. XXXII, 1458. The Lunar and Planetary Institute, Houston (CD-ROM). 

Matsunami S., Ninagawa K., Nishimura S., Kubono N., Yamamoto I., Kohata M., Wada T., Yamashita Y., Lu J., Sears D. W. G., and Nishimura H. (1993) Thermolumines-cence and compositional zoning in the mesostasis of a Semarkona group A1 chondrule and new insights into the chondrule-forming process. Meteoritics 57, 2101—2110. 

The compositions of the planets in the solar system and those of chondritic meteorites provide a guide to the bulk Earth composition (see Chapter 2.01). However, the rich compositional diversity of these bodies presents a problem insofar as there is no single meteorite composition that can be used to characterize the Earth. The solar system is compositionally zoned planets with lesser concentrations of volatile elements are closer to the Sun. Thus, as compared to Mercury and Jupiter, the Earth has an intermediate uncompressed density (roughly a proportional measure of metal to rock) and volatile element inventory, and is more depleted in volatile elements than CI-chondrites, the most primitive of all of the meteorites. 

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