Olivine grain boundaries

Figure 8.3 Heating dusty olivine grains in a reducing environment forms forsterite grains with small iron-rich blebs (

Figure 8.36. DF image formed with diffusely scattered electrons showing a band about 10 nm wide along a grain boundary between two olivine grains in a hot-pressed olivine-basalt aggregate annealed for 200 hours near 1250°C at 1 GPa. (From Vaughan and Kohlstedt 1982.)...

Ricoult, D. L., Kohlstedt, D. L. (1983). Structural width of low-angle grain boundaries in olivine. Phys. Chem. Minerals, 9, 133-8. 

The Mg is also another measure of depletion, but is more susceptible to modification by secondary metasomatic processes in the mantle, or to alteration by serpentinization and/or marine weathering. Olivine Mg is sometimes used to avoid problems of grain-boundary... 

Silicates and oxides in pallasites Olivine (F080-90). chromite, low-Ca pyroxene (En83 9i) Coarse-grained, rounded to angular Cumulates from core-mantle boundary... 

Nanoparticles may also be important within planetary interiors. For example, phase transitions within the deep Earth may generate materials that are composites of nanoparticles (e.g., within the spinel phase at the olivine-spinel transition at the 400-km discontinuity). These grain sizes may affect both kinetics and rheology (e.g., of ice in planetary interiors Stern et al. 1997). Chemical reactions in the deep Earth, perhaps between metal and silicate near the core-mantle boundary, may be impacted by nanocrystals. 

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