Abstract
Compressional wave velocities in an olivine nodule from Takashima Islet, Karatsu, were measured up to 900°C and 18kb. Piston-cylinder type high pressure apparatus was used. The sample showed strong elastic anisotropy, so that the velocities passing through the specimens in the three mutually perpendicular directions were observed, and the temperature derivatives of the wave velocity at constant pressure, (∂Vp/∂T)P, were determined. The average of (∂Vp/∂T)P of the three directions is about -0.73m/sec/deg. This value may give good approximation for the isotropic case. The pressure derivative of the wave velocity at constant temperature, (∂Vp/∂P)T, is 11.0m/sec/kb for the present sample. Combining both derivatives, the critical thermal gradient for the compressional wave velocity, (∂T/∂P)Vp, is 15.1deg/kb.
