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Sulfur Saturation Limits in Silicate Melts and their Implications for Core Formation Scenarios for Terrestrial PlanetsThis study explores the controls of temperature, pressure, and silicate melt composition on S solubility in silicate liquids. The solubility of S in FeO-containing silicate melts in equilibrium with metal sulfide increases significantly with increasing temperature but decreases with increasing pressure. The silicate melt structure also exercises a control on S solubility. Increasing the degree of polymerization of the silicate melt structure lowers the S solubility in the silicate liquid. The new set of experimental data is used to expand the model of Mavrogenes and O'Neill(1999) for S solubility in silicate liquids by incorporating the influence of the silicate melt structure. The expected S solubility in the ascending magma is calculated using the expanded model. Because the negative pressure dependence of S solubility is more influential than the positive temperature dependence, decompression and adiabatic ascent of a formerly S-saturated silicate magma will lead to S undersaturation. A primitive magma that is S-saturated in its source region will, therefore, become S-undersaturated as it ascends to shallower depth. In order to precipitate magmatic sulfides, the magma must first cool and undergo fractional crystallization to reach S saturation. The S content in a metallic liquid that is in equilibrium with a magma ocean that contains approx. 200 ppm S (i.e., Earth's bulk mantle S content) ranges from 5.5 to 12 wt% S. This range of S values encompasses the amount of S (9 to 12 wt%) that would be present in the outer core if S is the light element. Thus, the Earth's proto-mantle could be in equilibrium (in terms of the preserved S abundance) with a core-forming metallic phase.
Document ID
20070034435
Document Type
Reprint (Version printed in journal)
Authors
Holzheid, Astrid (Massachusetts Inst. of Tech. Cambridge, MA, United States)
Grove, Timothy L. (Massachusetts Inst. of Tech. Cambridge, MA, United States)
Date Acquired
August 24, 2013
Publication Date
January 1, 2002
Publication Information
Publication: American Mineralogist
Volume: 87
ISSN: 0003-004X
Subject Category
Lunar and Planetary Science and Exploration
Funding Number(s)
CONTRACT_GRANT: NAG5-13051
CONTRACT_GRANT: NAG5-4768
Distribution Limits
Public
Copyright
Other