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Nanophase iron (npFe) is relatively abundant in the lunar regolith and is widely believed to have formed by reduction of Fe during space weathering (micrometeorite/cosmic ray bombardment;[1]). Iron-silicides (Fe-Si) and native silicon require more reducing conditions than Fe0, and though predicted to be present in the lunar regolith have only been reported from one lunar meteorite and one lunar regolith sample [2, 3, 4]. Fe-Si and native silicon are only stable at extremely reducing conditions and have been proposed to form by a mechanism similar to that of metallic iron [3]. The stability of native silicon requires ten orders of magnitude lower oxygen fugacity than metallic iron at temperatures above 1600 K [5].

An early study of the soil sample (61500,[6]) suggested elevated levels of carbon, and an EPMA study of the Fe-Si from this soil sample [7] suggested that carbon might be present in the Fe-Si. Because carbon …