Study on the genesis of sulfide-rich textures in symplectite of the Howardite NWA 14701
Symplectites are rare in HED meteorites.The study of secondary textures in them is helpful to understand the metamorphism of minerals after the magmatic stage of its parent body,and even reveal the metasomatic process related to volatile-bearing fluid.In this work,two sulfide-rich textures,namely,the"Ca-rich augite-troilite-SiO2(SRT-Ⅰ)"and the"hypersthene-troilite-a small amount of SiO2(SRT-Ⅱ)",have been found in the three-phase symplectite of Howardite NWA 14701.Sulfide-rich replacement textures also appear in some tridymites(SRT-Ⅲ)adjacent to the symplectite.Based on the detailed analysis of petrographic and mineralogical characteristics of the symplectite lithic clasts,we suggest that the two sulfide-rich textures of SRT-Ⅰand SRT-Ⅱ in the symplectite lithic clasts of NWA 14701 are the products of sulfidation between the S-rich vapor and the primary metastable Fe-rich pyroxene or the Fe-rich olivine in symplectite,respectively.The S-rich vapor also metasomatized the adjacent tridymite grains to form SRT-Ⅲ.In this work,traces of sulfidation of three minerals have been found in the symplectite lithic clasts of the HED meteorites.Sulfidation may occur at different time periods during the evolution of the HED's parent body,in which the sulfidation of Fe-rich pyroxene should be a relatively early process,while the sulfidation of Fe-rich olivine should be a relatively late process.
HowarditeSymplectiteSulfide-rich texturesPetrology and mineralogySulfidation
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