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

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Abstract
Ultrasonic measurements of Qp−1 and Vp for An and Di.64An.36 melts are reported in the frequency range 3 – 20 MHz and in the temperature range from melting to 1934K and 1831K5 respectively. When Qp−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 Qp−1, the activation energies calculated for An and Di.64An.36 melts are on the order of 216 and 302 kJ/mol, respectively. Although there is insufficient data for An, the activation energy of Qp−1 for Di.64An.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.64An.36 at 1677K is 23.0 ± 0.1 GPa. These values fall into a general trend of decreasing bulk modulus with increasing Al2O3.