Experimental study of the elasticity of single crystalline calcite under high pressure (the calcite I—calcite II transition at 14.6 kbar)

Abstract

The length variations and the ultrasonic wave velocities were measured along principal single crystal calcite axes under high pressure. We have observed that six independent elastic constants undergo drastic changes at the calcite I—calcite II transition point at 14.6 kbar. Furthermore, we have determinated the length and volumetric variations in the phases I and II and during the I–II transition. These results allow us to deduce the following important points: influence of the planar CO 3 groups on the strong linear compressibility anisotropy in phase I; reciprocal relation between the decrease of elastic constants at the transition point and the anomaly of compressibility of the calcite II; compatibility of our data with the monoclinic structure of calcite II.