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This chapter presents diffusion data for a group of silicate minerals not covered by the other chapter categories. It is a diverse collection of minerals, ranging from silicate perovskite, a dominant phase in the Earth’s lower mantle, to quartz, a common crustal mineral, to melilite, an important constituent of calcium-aluminum-rich inclusions in primitive chondrite meteorites. A summary of the properties of minerals reviewed in this chapter is in Table 1⇓. This review will focus primarily on diffusion of cations, as diffusion of noble gases, hydrogen and oxygen are considered in other chapters in this volume (Baxter 2010; Farver 2010).
DIFFUSION IN QUARTZ
Quartz is among the most abundant minerals in the continental crust, found in many igneous, metamorphic and sedimentary rocks. It also has various technological applications because of its piezoelectric properties (e.g., Ramus 1989; Lang 1993). Quartz is one of the most stable minerals, resistant to chemical attack and weathering. It can contain minor amounts of aluminum, alkali elements, and transition elements; quartz color, and in some cases luminescence, can be attributed to the presence of these elements and the defects they create. For example, tiny rutile needles or TiO2 in the colloidal state may be responsible for rose and blue quartz coloring, respectively, and the coloration of citrine is due to the presence of colloidal ferric hydroxide distributed submicroscopically (e.g., Deer et al. 1992).
Diffusion of the major constituents of quartz, Si and O, has been extensively investigated under a broad range of conditions (Giletti and Yund 1984; Dennis 1984; Farver and Yund 1991; Sharp et al. 1991, Jaoul et al. 1995; Béjina and Jaoul 1996; Cherniak 2003). Since oxygen diffusion in minerals will be …