Olivine chemistry

The weathering of silicates has been investigated extensively in recent decades. It is more difficult to characterize the surface chemistry of crystalline mixed oxides. Furthermore, in many instances the dissolution of a silicate mineral is incipiently incongruent. This initial incongruent dissolution step is often followed by a congruent dissolution controlled surface reaction. The rate dependence of albite and olivine illustrates the typical enhancement of the dissolution rate by surface protonation and surface deprotonation. A zero order dependence on [H+] has often been reported near the pHpzc this is generally interpreted in terms of a hydration reaction of the surface (last term in Eq. 5.16). 

Schott, J., and R. A. Berner (1985), "Dissolution Mechanism of Pyroxenes and Olivines During Weathering", in J.l. Drever, Ed, The Chemistry of Weathering, NATO ASI SERIES C 149, 35-53. 

If we consider the seven components in tables 5.12 and 5.13 as representative of the chemistry of natural olivines, it is clear that 21 regular binary interaction parameters (disregarding ternary and higher-order terms) are necessary to describe their mixing properties, through a combinatory approach of the Wohl or Kohler type (cf section 3.10). In reality, the binary joins for which interactions have been sufficiently well characterized are much fewer. They are briefly described below. 

Figure 5JO Experimentally observed intracrystalline disorder in (Mg,Fe)2Si04 mixture, compared with theoretical distribution curves generated by interionic potential calculations. = Aikawa et al. (1985) = Smyth and Hazen (1973) = Brown and Prewitt (1973) 0,0, A = Ottonello et al. (1990). From G. Ottonello, F. Princivalle, and A. Della Giusta, Temperature, composition and/o effects on intersite distribution of Mg and Fe in olivines. Physics and Chemistry of Minerals, 17, 301-12, copyright 1990 by Springer Verlag. Reprinted with the permission of Springer-Verlag GmbH Co. KG.

Bostrom D. (1988). Experimental studies of (Ni,Mg)—and (Co,Mg)—olivine solid solutions by single crystal X-ray diffraction and solid state emf method. Ph.D. thesis. Department of Inorganic Chemistry, University of Umea, Umea, Sweden. 

Brown G. E. (1970). The crystal chemistry of the olivines. Ph.D. Dissertation, Virginia Polytechnic Inst, and State University, Blacksburg, Virginia. 

Schott, J., and Berner, R. A. (1985). Dissolution mechanisms of pyroxenes and olivines during weathering. In The Chemistry of Weathering (J. I. Drever, ed.), pp. 35-53. Reidel Publ., Dordrecht, The Netherlands. 

Ghose, S., Wan, C., Okamura, F., Ohashi, H. Weidner, J. R. (1975) Site preferences and crystal chemistry of transition metal ions in pyroxenes and olivines. Acta Cryst., A31, S76. 

King, T. V. V. Ridley, W. I. (1987) Relation of the spectroscopic reflectance of olivine to mineral chemistry and some remote sensing implications. J. Geophys. Res., 92,11457-69. 

Papike J. J. (1998) Comparative planetary mineralogy chemistry of melt-derived pyroxene, feldspar, and olivine. In Planetary Materials, Reviews in Mineralogy (ed. J. J. Papike). Mineralogical Society of America, Washington, DC, vol. 36, chap. 7, pp. 7-10-7-11. 

Swindle T. D., Kring D. A., Burkland M. K., Hill D. H., and Boynton W. V. (1998) Noble gases, bulk chemistry, and petrography of olivine-rich achondrites Eagles Nest and Lewis Cliff 88763 comparison to brachinites. Meteorit. Planet Sci. 33, 31-48. 

There are two types of refractory inclusions calcium- and aluminum-rich inclusions (this section) and amoeboid olivine aggregates (Section 1.07.5.3). Since the mineralogy, chemistry and isotope chemistry of refractory inclusions were reviewed by MacPherson et al. (1988), many new analyses have been made of CAIs in CV, CM, CO, CR, CH, CB, ordinary and enstatite chondrites that provide important constraints on physicochemical conditions, time, and place of CAI formation. CAIs are addressed in detail in Chapter 1.08, the role of condensation and evaporation in their formation in Chapter 1.15, and their clues to early solar system chronology in Chapter 1.16. 

Rietmeijer F. J. M. (1989) Ultrafine-grained mineralogy and matrix chemistry of olivine-rich chondritic interplanetary dust particles. Proc. 19th Lunar Planet. Set Conf. 513-521. 

Cr-poor variety widespread, locally abundant (e.g.. Monastery). Garnets, clino- and orthopyroxenes, phlogopite and ihnenite most common, zircon and olivine rarer. Debatable whether phlogopite and olivine are members of Cr-poor suite. Wide range in chemistry but Cr-poor, Fe-Ti-rich relative to type I (low-Z) peridotite minerals. Mineral chemistry and estimated equilibration P/Ts overlap those of type V (high-Z) Iherzolites. Some Slave craton Cr-poor megacrysts show mineral chemistry links to type II megacrystalline pyroxenite xenoliths. See review of Schulze (1987). 

P-type inclusions high-Cr, low Ca garnet, Cr-diopside, Fo-rich olivine, orthopyroxene, chromite, wustite, Ni-rich sulfide, have restricted, high Mg, high Ni chemistry. Equilibration temperatures 900-1,100 °C. 

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