Enon and Puente del Zacate: A duo of primitive-silicate-bearing magmatic irons

A duo of primitive-silicate-bearing magmatic irons. For guidance on citations see FAQs. c [not recorded] Version: Version of Record Copyright and Moral Rights for the articles on this site are retained by the individual authors and/or other copyright owners. For more information on Open Research Online's data policy on reuse of materials please consult the policies page. Introduction: In a previous LPSC abstract [1], we presented new electron microprobe and oxygen isotopic analyses for Enon, which is currently classified as an ungrouped iron. We highlighted how its apparent affinities to multiple meteorite groups made its classification complex but concluded that its achondrite-like texture and the primitive-composition of its silicates were perhaps indicators that it was best described as a primitive achondrite. Here we reevaluate those analyses and those of previous authors and suggest that Enon is actually a IIIAB silicate-bearing iron, which would make it the second IIIAB that contains primitive silicate material [2]. Puente del Zacate: Puente del Zacate was classified as a member of the IIIAB iron meteorite group-based upon the composition of its metal [3]. The identification of a primitive silicate inclusion by [2] came as quite a surprise. They noted that the chondritic nature of the silicate minerals contrasted with the formation models for the magmatic (differentiated) IIIABs. However, their analyses of the whole-rock oxygen isotope composition of the silicate clast were consistent with other oxygen-bearing phases within IIIAB irons [2], supporting its initial classification. They admitted that it was hard to explain the formation of such primitive material embedded within a magmat-ic iron matrix. Enon and the IIIABs: The suggestion that Enon is related to the IIIAB irons is not a new one, it was first put forward by [4], who recognized that his measured Ga/Ni and Ge/Ni ratios were similar to the IIIAB irons. [5] also noted that, if you compared the Ni-content in Enon's metal component with other meteorites , several of the rare earth elements (Ga, Ge, As, Au) were equivalent to that of a IIIAB iron. However, this idea was not seriously entertained because of the chondritic silicates it contains. Enon is approximately equal parts silicate, sulfide, and metal. When examining textural relationships within Enon, combined with the high abundance of sulfide, it is reasonable to suggest that this small meteorite (763g total known weight) is sampling part of a larger sulfide nodule. These nodules are not uncommon in IIIAB irons, …