Density and velocity model of metamorphic rock properties in the upper and middle crystalline crust in the kola superdeep borehole (SG-3) section

Abstract

Using the experimental and calculated data as the base, a model for a depth dependence of density, compression and shear wave velocities along the Kola superdeep borehole (SG-3) section was developed down to a depth of ~25 km. The variations of the density, compression and shear wave velocities are mainly caused by the changes in the rock mineral composition. The relative reduction in the velocities of compression and shear waves with depth under the influence of increasing pressure and temperature in the range of 5-25 km is about 2%. The observed increase in seismic velocity with depth may be due to changes in the degree of metamorphic transformation of rocks.