¹D. J. Wilson, ¹B. T. Gänsicke, ²D. Koester, ¹O. Toloza, ¹A. F. Pala, ¹E. Breedt,³S. G. Parsons

¹Department of Physics, University of Warwick, Coventry CV4 7AL, UK
²Institut für Theoretische Physik und Astrophysik, University of Kiel, D-24098 Kiel, Germany
³Departamento de Física y Astronomía, Universidad de Valparaíso, Avenida Gran Bretaña 1111, Valparaíso 2360102, Chile

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Reference
Wilson DJ, Gänsicke BT, Koester D, Toloza O, Pala AF, Breedt E, Parsons SG (2015)
The composition of a disrupted extrasolar planetesimal at SDSS J0845+2257 (Ton 345). Monthly Notices of the Royal Astronomical Society 451, 3237-3248.
Link to Article [doi: 10.1093/mnras/stv1201]

¹Aaron S. Bella, ¹Charles Shearera, ²J. Maarten deMoor, ¹Paula Provencio
¹Institute of Meteoritics and Department of Earth and Planetary Sciences, University of New Mexico
²OVSICORI, Universidad Nacional, Heredia, Costa Rica

In this work, we investigate the compositions and origin of metasomatic fluids responsible for the formation of sulfide replacement textures in Mg-Suite lithologies of lunar samples 67915-149 and 67915-150. We have constructed a quantitative thermodynamic model of the composition of the metasomatic fluid using fO2, fS2, and temperature constraints derived from a thermodynamic analysis of the metasomatic fluid-mineral reactions and the measured compositions of the phases in the sulfide assemblages. Results from this modeling indicate that the metasomatic fluid responsible for the formation of the sulfide replacement textures was likely dominated by a combination of H2 and CH4, with minor abundances of H2O, CO, and H2S. The modeling indicates that H2S was, by orders of magnitude, the dominant S-species present in the metasomatic fluid and S isotopes in the replacement sulfides suggest that the fluid experienced significant removal of H2S by sulfide precipitation. The calculated H2 and H2O contents of the metasomatic fluid are consistent with those that might be expected for the late stage degassing of shallowly emplaced, intrusive magma bodies.

Reference
Bell AS, Charles Shearera, deMoor JM, Provencio P (2015) Using the Sulfide Replacement Petrology in Lunar Breccia 67915 to Construct a Thermodynamic Model of S-bearing Fluid in the Lunar Crust. Geochimica et Cosmochimica Acta (in Press)
Link to Article [doi:10.1016/j.gca.2015.08.002]

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