Willy: A Prize Noble Ur-Fremdling from the Allende Meteorite

Abstract

Among the most exotic and complex objects found in CAI are Fremdlinge (1). The small size of these objects (typically << 50 µm) has limited their petrologic and chemical investigation, and, to date, no isotopic analyses of individual Fremdlinge have been performed. The Allende CAl 5241 contains numerous Fremdlinge, two of which are of very large size (>100 µm P) and are contained in a single melilite grain. We report on a detailed petrologic and chemical investigation of "Willy", the larger of these Fremdlinge (~150 µm Ø). Willy is compose primarily of a V-rich magnetite (V-mt), Ni-Fe metal, and troilite (FeS). Minor constituents include scheelite (CaW0_4), apatite, an Os-Ru alloy, MoS_2, and an unidentified Mg- Fe- molybdate. Willy contains a complex fluffy core of V-mt, metal, FeS, and other minor phases. The core is surrounded by a compact V-rich magnetite mantle. The mantle is surrounded by a rim composed of V-rich fassaite and V-rich spinels. This type of rimming is typical of oxide-bearing Fremdlinge in 5241 and other CAl from the Allende carbonaceous chondrite (CV3).