Compressional wave velocities in metamorphic rocks at pressures to 10 kilobars

Abstract

Velocities of compressional waves have been measured at pressures of 100 to 10,000 bars for various metamorphic rocks which are believed to be important constituents of the earth's crust. Detailed petrographic and petrofabric analyses are reported from, thin sections cut from the specimens. The principal factors contributing to the velocities of compressional waves in igneous and metamorphic rocks are discussed. Particular attention is given to the dependence of velocity on porosity, mineral orientation, and mineral composition. The principal conclusions are: (1) the initial changes in velocity with pressure are related to the arrangement and shape of pore spaces in a rock, (2) variation of velocity with propagation direction in metamorphic rocks is a consequence of preferred mineral orientation, and (3) velocities calculated from single-crystal data agree with most of the measured velocities.