Data for Moderately Volatile Elemental Depletion and Potassium Isotope Fractionation During Evaporation in Laser-Heating Aerodynamic-Levitation Experiments
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This is the data for manuscript "Moderately Volatile Elemental Depletion and Potassium Isotope Fractionation During Evaporation in Laser-Heating Aerodynamic-Levitation Experiments" Abstract: Moderately volatile element (MVE) depletion and isotopic fractionation are commonly observed in planetary materials. The mechanisms driving these phenomena are subject to intense debate, with some proposing evaporation at various stages of planetary formation as a potential explanation for both elemental depletion and isotopic fractionation. Studying the isotopic fractionation of MVEs can also be useful for investigating the conditions of high-temperature processes in the solar system and on Earth. Evaporation experiments to understand the behavior of isotopic fractionation under variable conditions provide a grounded context for interpreting the geochemical signatures of natural materials. Here we present new experimental data obtained from a novel approach that uses flowing gas to levitate samples and a laser to heat them. This approach offers the advantage of preventing undesired sample-container reactions at elevated temperatures and enabling ultrafast quenching. We analyzed the MVE depletion (e.g., Na, K, Cu, Zn, Ga and Rb) and potassium isotope fractionation associated with heating basalt and loess materials at temperatures up to 2046 °C under multiple oxygen fugacities. Our results show that the starting composition has a strong effect on the observed MVE depletion and K isotope fractionation factor for evaporation and we attribute different diffusion coefficients in the melts as the reason for such difference during evaporation. We additionally computed the evaporation coefficients of K and Zn across various temperature, oxygen fugacities and melt compositions, and systematically explored the relationships between evaporation coefficient and these factors. Our experiments on loess materials offer valuable insights into the formation of tektites, shedding light on the significant Cu and Zn depletion relative to K. However, our observations reveal higher levels of K isotopic fractionation in loess materials compared to basaltic materials, alongside greater isotopic fractionation under reducing conditions. These findings contrast with the minimal K isotopic fractionation observed in tektites, highlighting differences between impact-induced evaporation and static evaporation from a silicate melt, and suggesting that a much more rapid heating and quenching process is required during tektite formation.
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Institutions
- Washington University in St. Louis