Measured and calculated compressional wave velocities of crustal and upper mantle rocks in the Central Zone of the Limpopo Belt, South Africa - implications for lithospheric structure

Abstract

Experimental compressional wave velocity (Vp) measurements were performed on felsic metasedimentary and igneous lithologies belonging to the Beit Bridge Group, and other amphibolite facies rocks, found in and around the Venetia Kimberlite pipes, which intrude the Central Zone of the Limpopo Belt. Xenoliths of eclogite, granulite, gabbronorite and garnet-quartz, which represent the major crustal and upper mantle lithologies found in the kimberlite host rock were too small for experimental measurements. Compressional wave velocities for these samples were calculated, based on their modal mineralogy and end member mineral compositions. Compressional wave velocities were corrected for in-situ conditions based on estimated equilibration temperatures and pressures, and the resulting velocities were compared with the seismic refraction model of the Limpopo Belt, in order to construct a lithologic column of the crust and upper mantle below the Venetia Mine.