Elastic properties of polycrystalline magnesium, iron, and manganese carbonates to 10 kilobars

Compressional- and shear-wave velocities to 10 kb and the chemistry for naturally occurring polycrystalline aggregates of magnesite MgCO3, siderite FeCO3, and rhodochrosite MnCO3 are reported. Velocity-density relationships for the magnesite-siderite series show a dependence on mean atomic weight similar to that observed for the olivine series. Iron substitution for magnesium in carbonates decreases the shear modulus and increases Poisson's ratio. The bulk modulus, however, changes relatively little with iron substitution. Manganese substitution, in carbonates affects the velocities and elastic parameters in much the same way as iron.