Evaporation of moderately volatile elements from metal and sulfide melts: implications for volatile element abundances in magmatic iron meteorites

Steenstra, ES; Renggli, JC; Berndt, J; Klemme, S

Research article (journal)

Abstract

Volatile element abundances in magmatic iron meteorites provide fundamental insights into the processing of volatile elements in the early solar system. Although Cu, Ge and Ag concentrations of magmatic iron meteorites deviate up to 4 log units between different magmatic iron meteorite groups, the role of evaporation on these volatile abundances is poorly constrained. Here, we for the first time experimentally assess the volatility of Cu, Ge, Ag, S, Cr, Co, Ni, Mo, Ru, Pd, W, Re and Ir from metal and sulfide melts as a function of pressure (10−4 and 1 bar), temperature (1573−1823 K) and time (5−120 min) for two end-member compositions (Fe versus FeS). These novel experiments demonstrate that the presence of S is a major parameter in establishing the volatility of Ge, Mo, Ag, Ru, W, Re and Ir. At constant P-T and time, the volatility of Ge, Mo, Ru, W, Re and Ir are greatly increased in the presence of S, whereas Ag is less volatile in the presence of S. At 1773 K and ~0.001 bar, the volatility of S is sufficiently high that the degassed FeS liquid showed immiscibility of a S-rich sulfide and a S-poor Fe melt. Combining the novel results allowed for deriving empirical equations that predict the volatility of Cu, Ge, Mo, Ag from Fe and/or FeS liquid as a function of temperature and time. A comparison of our volatility sequences with commonly applied 50% condensation temperature models shows that the latter models cannot be applied to sulfur-bearing Fe liquids and therefore magmatic iron meteorites. Application of our new models on previously derived depletions of the elements of interest in the IVB parent body shows that evaporation, if it occurred, cannot have taken place under S-rich conditions, as it would result in a depletion of Mo, which is not observed for the IVB irons. However, evaporation of a S-poor/S-free Fe liquid reproduces the observed volatility depletion trend for IVB irons under a wider range of temperature and evaporation times, demonstrating the importance of evaporative loss on the IVB parent body

Details zur Publikation

Release year: 2023
Language in which the publication is written: English
Link to the full text: https://www.sciencedirect.com/science/article/pii/S0012821X23004193?via%3Dihub