Laboratory studies on kolar rocks

Abstract

A number of Hornblende schists, and associated basic rocks collected from the Kolar Gold Fields, Mysore state, India; from different levels, have been studied in detail in the laboratory. These studies comprise the geological aspects—petrographic investigations, chemical analysis, modal analysis; and physical properties—density, porosity, compressional and shear wave velocity, anisotropy and wave attenuation. The effect of water saturation on velocity was also studied. A number of samples were subjected to axial stress (a few of them up to the breaking point) and the corresponding change in wave velocity with stress investigated. Simulataneously, static—strains (axial and lateral) were recorded and the static moduli so computed are comparable to the calculated dynamic moduli. The geological investigations indicate that these rock types are of sedimentary origin. Petrographic studies clearly reveal that these rocks are highly deformed which fact accounts for the anisotropy in wave velocity. In general, these rocks are fine-grained, dense and compact, highly metamorphosed and are traversed by innumerable veins of siliceous and calcareous material, exhibiting high values of wave velocity, low attenuation and a large bearing capacity. Anisotropy is found to increase with porosity in these rocks. A small increase in both velocity and density with increasing depth of occurrence is indicated.