The sulfur concentration in silicate melts at sulfide saturation (SCSS) was experimentally investigated in a temperature range from 1250ºC to 1450ºC and a pressure range from 500 MPa to 1 GPa in a piston-cylinder apparatus. The investigated melt compositions varied from rhyolitic to basaltic. All experiments were saturated with a FeS melt. Temperature was confirmed to have a positive effect on the SCSS and no measurable pressure effect was observed. Oxygen fugacity was controlled to be either near the carbon-carbon monoxide buffer or one log unit above the nickel-nickel oxide buffer, and found to positively affect the SCSS. A series of models were constructed to predict the SCSS as a function of temperature, pressure, melt composition, oxygen fugacity and sulfur fugacity of the system. The coefficients were obtained by the regression of experimental data from this study and from data in the literature. The best model found for the prediction of the SCSS is: lnSppm =-996T+9.875+0.997lnMFM+0.1901lnf O2-0.0722&parl0;PT &parr0;-0.115lnfS2 where P is in bar, T is in K, and MFM is a compositional parameter describing the melt based upon cation mole fractions: MFM=Na+K+2 Ca+Mg+Fe2+Six Al+Fe3+. / This model predicts the SCSS in anhydrous silicate melts from rhyolitic to basaltic compositions at crustal conditions from 1 bar to 1.25 GPa, temperatures from ~1200 to 1400ºC, and oxygen fugacities between approximately two log units below the fayalite-quartz-magnetite buffer and one log unit above the nickel-nickel oxide buffer. For cases where the oxygen and sulfur fugacities cannot be adequately estimated a simpler model also works acceptably: lnSppm =-5328T+8.431+1.244 lnMFM-0.01704P T+lnaFeS where aFes is the activity of FeS in the sulfide melt and is well approximated by a value of 1. Additional experiments were performed on other basalts in a temperature range from 1250ºC to 1450ºC at 1 GPa to test the models. The model predictions and the measurements of the SCSS agree within 5%. Although I cannot fix exactly the stoichiometric coefficients of the reaction controlling sulfur dissolution, my experiments and models suggest that the solution reaction for sulfur in melts saturated with sulfide is similar to: 8FeSsulfide +3FeOsilicate+4O2-silicat e+2O2gas ⇔4S2-silicate+2S 2gas+11FeOsulfide where the subscripts indicate the phase and O 2- represents "free" oxygens in the silicate melt. / Keywords. sulfur, solubility model, dissolution mechanism, silicate melts
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.98753 |
| Date | January 2006 |
| Creators | Liu, Yanan, 1981- |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Earth and Planetary Sciences.) |
| Rights | © Yanan Liu, 2006 |
| Relation | alephsysno: 002487091, proquestno: AAIMR24723, Theses scanned by UMI/ProQuest. |
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