Preliminary investigation results on fabrics and related physical properties of an anisotropic gneiss

In order to evaluate the fabric-dependent anisotropy of a particular gneiss type, we assessed the quartz lattice and shape preferred orientations as w ell as the microcrack pattern statistics. In the rock mechanics laboratory, several strength and deformability tests on drilled rock samples were run and the seismic wave propagation properties along the rock's principal stra in axes were determined. In the mechanical tests it turned out that despite a distinct stretching lineation with initially extreme grain elongation, t he rock performs for the larger part as a transversely isotropic material w ith the schistosity as plane of isotropy. The anisotropy in seismic wave pr opagation within the plane of schistosity is attributed primarily to a high ly anisotropic microcrack pattern, the distinct gneissose banding and to a lower degree to the LPO of quartz. (C) 2000 Elsevier Science Ltd. All right s reserved.