Elemental Abundances in the NWA 8785 Anomalous EL3 and the Compositional Diversity of Enstatite Chondrites

The enstatite chondrites (EC) are remarkable in having stable isotopic compositions similar to Earth-Moon, suggesting they formed in the inner solar system and were potentially among the building blocks of the terrestrial planets. EL3 are of particular importance being identified as the best candidates for Earth’s building blocks. However, the EL3 group represent a range of materials with well known anomalous samples. To better understand these primitive meteorites, we have begun to analyze their whole rock chemistries to re evaluate their classification and decipher the nature of their parent bodies.

Since Keil's landmark paper at least two major groups of EC have been identified, now known as EH and EL, suggesting at least two parent bodies for EC. Unfortunately, the EC are a relatively small meteorite class making up less than 2% of all known chondrites with less than 25 unequilibrated (type 3) individuals known. However, even within this meager suite, the EL group shows a wide range of petrologic features with samples that do not fit easily into EH or EL groups, suggesting potential new EC groups exist [e.g., 6,7].

How many EC parent bodies? Kong et al. argued for a single parent for EH and EL based on continuities in their bulk chemical data. More recently, based largely on Cr contents of troilite as a measure of thermal history, division of EH and EL each into subgroups a and b has been proposed and sourcing from four to eight parent bodies has been suggested for the EC class. Here we present the whole rock chemical composition of the anomalous EL3 NWA 8785, explore compositional diversity of EC and discuss implications for EC parent bodies.