Oxidation state and occurrence of Fe in olivine from lherzolite xenolith in Oki Islands, Japan, were investigated. 57Fe Mössbauer spectral analysis and EMPA methods of fresh olivine on the central part of the xenolith resulted in the existence of 0.02-0.03 apfu Fe3+ in olivine. HRTEM observation and electron diffraction data of the olivine indicated that olivine has pure olivine structure, suggesting that the Fe3+ in olivines in the xenolith exists within the olivine structure. In contrast to the olivine in the core part of the xenolith, contacting with the host alkali basalt, contain fine precipitates on the rim and along fractures. Although observation using TEM indicated inclusion-like domains in this area, the domains are indentified as olivine. However, electron diffraction spots showed weak streak along c axis. These facts suggest the existence of two olivine structures with slightly different structural properties.
