Preliminary AEM study of the microstructure and composition of metal particles in ordinary chondrites

The purpose of this study is to examine the microstructure and composition of the metal particles in ordinary chondrites using analytical electron microscopy (AEM) techniques. Since the phases produced within the metal particles are very fine, the application of various AEM techniques for structural and chemical characterization is critical. However, thin specimen preparation for AEM study has proven very difficult because of the matrix silicate which is present. This is the first AEM study of the metal particles in chondrites. A type 6 chondrite, Saint Severin (LL6), was selected for examination because the metal phases have been reheated into the single phase taenite region (greater than 700 C), and cooled slowly to lower temperatures. A combination of electron optical instruments was employed including a field emission gun (FEG) JEOL 840F high resolution scanning electron microscope (HRSEM), a JEOL 6300F FEG-HRSEM, a Philips 400T AEM, and a JEOL 733 electron probe microanalyzer (EPMA).