Recent Progress in Characterization of Phyllosilicates and Related Minerals in Meteorites by Electron Microscope

Abstract

Recent progress in characterization of phyllosilicates and related minerals in carbonaceous chondrites is reviewed.
Detailed mineralogical investigations of matrix phyllosilicates and related minerals in carbonaceous chondrites have been carried out especailly by the use of high resolution electron microscope (HREM) with energy dispersive Spectrometer (EDS) for a last decade. It has been clarified that the platy phyllosilicates in carbonaceous chondrite matrix are mostly Fe-rich serpentine. In chondrule groudmass, the presence of 14 Å chlorite was recently confirmed. Another topic on the matrix minerals in carbonaceous chondrite was the discovery of 11 Å and 17 Å phase, which were suggested to be tochilinite and tochilinite-serpentine, respectively. The geneses of these minerals were discussed.
Recently unique C2 chondrites of Y-793321 and B-7904 were found. They do not contain normal phyllosilicates, but intermediate minerals, the presence of which suggests transformation from serpentine to olivines. The possible genesis of this thermal event was discussed.