Using the sulfide replacement petrology in lunar breccia 67915 to construct a thermodynamic model of S-bearing fluid in the lunar crust

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• 作者：Aaron S. Bell^a ; ^{asbell@unm.edu" class="auth_mail" title="E-mail the corresponding author} ; Charles Shearer^a ; J. Maarten deMoor^a ; ^b ; Paula Provencio^a
• 刊名：Geochimica et Cosmochimica Acta
• 出版年：2015
• 出版时间：15 December 2015
• 年：2015
• 卷：171
• 期：Complete
• 页码：50-60
• 全文大小：1906 K

文摘

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.