Diffusion in Pyroxene, Mica and Amphibole

By D. Cherniak, A. Dimanov. 2010

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This chapter presents an overview of diffusion data for pyroxenes, amphiboles and micas. These minerals are grouped together since amphiboles and micas are closely related in structure to pyroxenes, with amphiboles essentially constructed of alternating layers with structures of mica and pyroxene. We begin with discussion of diffusion in pyroxenes, for which an extensive literature exists, with diffusion studies of major, minor and trace elements. We consider diffusion mechanisms in light of present understanding of defect chemistry, and discuss various crystal-chemical factors that may affect cation diffusion. The last section of the chapter presents a review of diffusion data for amphiboles and micas. Selected Arrhenius relations for these all these mineral phases are summarized in the Appendix Tables A1⇓, A2⇓, A3⇓ and A4⇓. This chapter focuses primarily on cation diffusion, since oxygen, hydrogen and noble gas diffusion are discussed in other chapters; readers interested in more detailed discussion of diffusion of these species in pyroxene, amphibole and mica are directed to Chapters 10 (Farver 2010, this volume) and 11 (Baxter 2010, this volume). View this table: Table A1. Diffusion data for major cations in pyroxenes where D = D ( p O2) m exp( n·X Fe) exp(− Q / RT ) = D ′exp(− Q / RT ). View this table: Table A2. Arrhenius relations for trace and minor elements in pyroxenes, of the form D = D exp(− E a/ RT ). View this table: Table A3. Activation energies, pre-exponential factors, and activation volumes for diffusion of Ce and Yb in diopside over the pressure range 0.1-2.5 GPa (data from Van Orman et al. 2001). View this table: Table A4. Diffusion in micas and amphiboles. Since the early 1970s, solid state diffusion of cations in pyroxenes has been recognized to play a fundamental role in numerous geodynamical, petrological and geochemical processes involving mass transport. Knowledge …

Subfields: Environmental Engineering, Geophysics, Mechanics of Materials

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