Diffusion in Magmatic Melts: New Study

Condensation of major elements during chondrule formation and its implication to the origin of chondrules

“…The distribution of Ca, as mentioned above, is unique in that it is fairly homogeneous over the length scale of the chondrules except for the enrichment near the forsterite crystals. This exceptional homogeneity is attributable to a rapid diffusion of Ca compared to Al and Si in silicate melts (Hofmann, 1980;Chekhmir and Epel'baum, 1991;Liang et al, 1996), independence of Ca diffusion from that of Al and Si, which are net-work formers for the CH5 and CH13 compositions, and no further condensation or evaporation of Ca. It is, therefore, reasonable to assume that the Ca zoning was induced mostly by forsterite crystallization.…”

“…2 and 3) are attributable to rapid crystallization of forsterite inducing diffusion of cations in the host silicate melt. Observed zoning contrast, represented by the compositional difference between glass in contact with and that far away from forsterite crystals, can be explained by compositional contrasts between forsterite and the host glass for Mg, Al, Si, and Fe and for Ca, Na, and K with additional effect of their larger diffusivity (Hofmann, 1980;Chekhmir and Epel'baum, 1991). Such zonings for Mg, Al, Si, and Ca are comparable to those developed around skeletal forsterite in dynamic crystallization experiments (e.g., Pack and Palme, 2003), supporting the inference that the growth of forsterite induced the observed zonings around forsterite.…”

Chemical diffusion of major components in granitic liquids: Implications for the rates of homogenization of crustal melts

“…In conclusion, the diffusivities of Fe and Mg at crustal anatectic conditions are probably in between those of network-former components Si and Al, and those of the more mobile components H and alkalis, as has been found in previous diffusion experiments at higher temperature (e.g. Chekhmir and Epel'baum, 1991). The fluxes of Fe and Mg might be coupled to the concentration profiles of the other elements, whereas the reverse (fluxes of the rest of components coupled to the concentration profiles of Fe and Mg) seems unlikely.…”

Dissolution, growth and survival of zircons during crustal fusion: kinetic principals, geological models and implications for isotopic inheritance

“…Silica is also 'absorbed' or 'released' by the growth or dissolution of zircon, but this component diffuses significantly faster than ZrO 2 (e.g. Baker 1991;Chekhmir & Epel'baum 1991), so it is ZrO 2 transport that limits the rate of the overall process. Preliminary computer simulations, using the constant growth rate equations of Smith et al (1955), were run to establish that no significant change in the concentrations of major components develops against a growing or dissolving zircon.…”