抄録
The phase boundary for calcite I-II inversion was determined on the P-T plane up to 700°C and 25kb. The change in longitudinal ultrasonic velocity, which shows a remarkable minimum at the inversion point, was measured. The slope of the phase boundary is negative up to about 250°C; this coincides with the results of P.W. Bridgman and C. Wang. Above 300°C, the slope of the boundary turns to positive, and the inversion pressure rapidly rises with increasing temperature. The boundary has a minimum pressure at about 250°C. Since the boundary of calcite I and calcite II will never cross the boundary of calcite I and aragonite, there is no stable region for calcite II.
