Oscillatory zoned fayalitic olivine from the Lewis Cliff 90500 CM2 meteorite

A grain of fayalitic olivine with oscillatory Fe-rich and Fe-poor zoning occurs in the Antarctic Lewis Cliff 90500 CM meteorite, suggesting reaction via diffusion. This grain is continuously enclosed by a fine-grained rim ranging from 20 to 100 μm in thickness. Phyllosilicates and other hydrous phases occur at three broken edges of the grain as well as within its surrounding rim, suggesting in situ alteration via aqueous processes. This olivine grain plus its rim provides evidence for both anhydrous reaction that predated the accretion of the meteorite parent body and hydrous alteration that presumably occurred on the parent body.