A transmission electron microscopic study of the Bethany iron meteorite

Abstract

The Bethany iron meteorite which is a part of the Gibeon shower is a fine octahedrite with zoned plessite fields of various sizes. The optically irresolvable microstructural details inside the plessitic fields have been studied by transmission electron microscopy, and the crystallographic relationships between the primary kamacite (α) and the parent taenite (γ), and between the α and γ particles in the coarse plessite, have been examined using electron diffraction. In the case of primary kamacite the orientation-relationship with γ was close to the Nishiyama-Wasserman relationship, whereas, for the plessitic α, the orientation-relationship with γ was close to Kurdjumov-Sachs. It was also found that the (111)_γ and (110)_α planes were not strictly parallel. Additionally, measurements of the composition profile through the zoned plessite have been made using STEM microanalysis technique, and related to microstructure.