Geography ETDs

Geochemistry of Metal Segregation in Aubrites, and The Origin of Their Metallic Phases

Igncaio Casanova


The study of aubritic metal can provide important clues about the origin and ingenious and metamorphic history of the enstatite achondrite parent body. In this work, I have carried out petrographic and geochemical study of the metallic particles present in aubrites with the aim of constraining ideas about their origin and evolution. The extremely low oxygen fugacities under which enstatite meteorites formed (e.g. Larimer and Buseck, 1974; Fogel et al., 1989) and their consequent unique composition make interpretations difficult due to the lack of experimental data on highly reducing systems. I have tried to overcome the paucity of experimental data by using a theoretical thermodynamic approach to study the significance of such unique compositions based on three main themes: (1) the conditions of formation of the high-Si Fe,Ni alloys found in aubrites, (2) the study of the partitioning behavior of siderophile elements and their abundances relative to chondritic metal, and (3) the significance of perryite formation, which is unique to enstatite meteorites.