The bulk modulus ‐ attenuation ‐ viscosity systematics of diopside‐anorthite melts

Ultrasonic measurements of Q p −1 and V p for An and Di .64 An .36 melts are reported in the frequency range 3 – 20 MHz and in the temperature range from melting to 1934K and 1831K5 respectively. When Q p −1 and shear viscosity are normalized to their respective liquidus temperature values, they have the same linear dependence on reciprocal homologous temperature. From the Arrhenius temperature dependence of Q p −1 , the activation energies calculated for An and Di .64 An .36 melts are on the order of 216 and 302 kJ/mol, respectively. Although there is insufficient data for An, the activation energy of Q p −1 for Di .64 An .36 is in excellent agreement with its activation energy of viscosity. The relaxed adiabatic bulk modulus, derived from relaxed velocities, for An at 1893K is 20.4 ± 0.2 GPa and for Di .64 An .36 at 1677K is 23.0 ± 0.1 GPa. These values fall into a general trend of decreasing bulk modulus with increasing Al 2 O 3 .