Volatility of oxides from silicate melt and the origin of moldavites

Abstract

SUMMARY. The volatilities of SiO~, Na~O, and Fe~Oa x increase with increasing thermal function within the range 1600 to 2100 ~ during the melting of a sandy-silty clay. The remaining melt is to some extent enriched in Al~O3, K,O, CaO, and MgO. Chemical analyses of the sandy-silty clay, of the glasses melted from the latter, of the silicate material evaporated and newly condensed and their correlation with increasing thermal function and bulk density of glasses, as well as with the hitherto known quantitative data on moldavites, testify to the fact that in moldavites evaporated and newly condensed silicate material substantially prevails over material that passed directly from a solid to a fluid state. Evaporation of the silicate material from the rocks of the impact crater caused a significant change in relations between major oxides compared to the original relations in the source rocks. Thus, the hypothesis that tektites are directly remelted rocks of the Earth's crust, based on over-all chemical similarities of tektites and some rocks in major oxides, appears incorrect.MOLDAVITES are inhomogeneous silicate glasses belonging to tektites; they occur in southern Bohemia and Moravia, Czechoslovakia. Studies that contributed to a more detailed knowledge of moldavites were made by

The fate of moderately volatile elements in impact events—Lithium connection between the Ries sediments and central European tektites

“…). Several authors (Philpotts and Pinson ; Konta and Mráz ) suggested that the changes in element ratios (e.g., Na/Fe, Ca/Fe) resulted from chemical fractionation during evaporation and condensation processes. von Engelhardt et al.…”

Solubility of chromium oxide in binary soda-silicate melts

“…Appropriate amounts of the reagent powders were weighed and mixed, then introduced in a Pt 95 Au 5 crucible and heated in a muffle furnace. In order to minimise the sodium loss by volatilisation [19,20], not less than 200 g of glass was melted and the thermal cycle was defined as follows: 1200°C for 2 h, 1400°C for 2 h and then 1100°C for 24 h. The melts were then quenched and finally crushed. Glass compositions were systematically checked by electron probe microanalysis: the aimed and obtained glass compositions are reported in Table 1.…”

“…(17) and (18)), and by replacing logK ox , logK red and log aO 2− (Eqs. (20) and (21)) by their respective expressions, B and C parameters can be written as:…”

Redox‐Control Solubility of Chromium Oxide in Soda‐Silicate Melts

“…The reagents were weighted, grinded, and heated in a Pt 95 –Au 5 crucible. In order to minimize sodium loss by volatilization, 13,14 not <200 g of glass was melted once, and the thermal cycle was defined as follows: 2 h at 1200°C, 2 h at 1400°C, and then 24 h at 1100°C. Then, the crucible was removed from the furnace and quenched in air.…”