Article ID Journal Published Year Pages File Type
4706432 Geochimica et Cosmochimica Acta 2005 11 Pages PDF
Abstract

Models for thermodynamic behavior of FeO-bearing liquids are required for understanding the separate roles of evaporation, condensation and crystallization in the formation of free-floating silicate liquid droplets in the early solar nebula. These droplets, frozen as chondrules, are common in chondritic meteorites. Evaporation coefficients for Fe and FeO of ∼0.2 are calculated here from existing data using silicate liquid activity models. These models, used to describe gas-liquid-solid equilibria and to constrain kinetic processes, are compared and found similar, and the effects of liquid non-ideality are assessed. A general approach is presented for predicting the evaporation behavior of FeO-bearing Al2O3-CaO-SiO2-MgO liquids in H2-rich gas above 1400 K at low total pressure. Results are vapor pressure curves for Fe, FeO and other gas species above typical chondrule liquids, suitable for predicting compositional trajectories of residual liquids evaporating in a hydrogen-dominated vapor. These predictions are consistent with chondrule formation in the protoplanetary disk in heating events of short duration, such as those expected from shock wave or current sheet models.

Related Topics
Physical Sciences and Engineering Earth and Planetary Sciences Geochemistry and Petrology
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