2015 年 124 巻 3 号 p. 397-409
Olivine crystal grains have various crystallographic orientations within a peridotite, resulting in a crystallographic fabric as well as a texture. Six types of fabrics have been identified in mantle peridotites: A, B, C, D, E and AG types. These fabric types have unique seismic properties such as P-wave and S-wave velocity anisotropy. A new method is proposed to classify olivine fabrics based on P-wave velocity structure on a Vp-Flinn diagram. Three P-wave velocities (V1, V2, V3) are used, two of which are the maximum (V1) and minimum (V3) velocities, and the third (V2) is the velocity perpendicular to the orientations of these two velocities. Relationships between V1/V2 and V2/V3 classify fabrics into three types: A type (equivalent to B, C and E types), D type and AG type. Moreover, taking into account structural framework such as foliation and lineation, the Vp-Flinn diagram can be expanded to identify all types of fabrics. This method is successfully applied to fabrics previously studied in Oman ophiolite.