Thermodiffusion of major and trace elements in dried aluminosilicate glass

It has long been demonstrated that component redistribution by thermodiffusion that is driven by thermal gradient could lead to major element enrichment or depletion to varying degrees at the hot or cold ends of silicate glasses. However, thermodiffusion behaviors of trace elements have not been well constrained yet. Here we report the thermodiffusion for major and trace elements in-6 mm long capsules of dried aluminosilicate glass using the intrinsic thermal gradient of-38 degrees C/mm (mean temperature from 1070 degrees C to 1300 degrees C). Bulk Electron Probe Micro-Analyzer (EPMA) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) analyses across the capsules found that thermodiffusion behaviors for some major and trace elements in a long-duration run (168 h) show a slight flat pattern in concentration redistribution, but fluctuates greatly along the temperature gradient in a short-duration run (24 h). It suggests a time dependence on the thermodiffusion for major and trace element redistribution in the dried aluminosilicate melts. Overall, Si, the major network former, invariably segregates to the hot end of the capsule. In contrast, Al, Mg, Ca, Na, K, Sr, Ba, Pb, Mo, Ga, and U always show separation antithetic to Si, as these alkalies concentrate at the cold end along with the alkaline earth and large ion lithophile element. Niobium, Ta, and V that preferentially diffuse to the cold end show much faster redistribution (ST(Nb) = 0.65 x 10-3, ST(Ta) = 0.67 x 10-3, ST(V) = 0.83 x 10-3), could thus be a discriminator for thermodiffusion equilibrium. This study provides direct experimental evidence on the thermodiffusion of trace elements, and also highlights the potential role of the thermodiffusion on chemical differentiation for the aluminosilicate glass materials.