Geophysical Journal | 2001 volume 23 ╣2

Studies of elastic constants of gravitoids and anisotropy of elastic body wave propagation herein

© Prodaivoda G.T., Alexandrov K.S., Vyzhva S.A.

The invariant - polarization ultrasonic method was used to measure phase velocities of isonormal waves, namely a quasi-longitudinal, a "fast" and "slow" quasi - transverse waves in samples of granitoids of different formation conditions. The samples had the form of cuberhombododecahedrons and the size of 30x30x30 mm3. The elastic fluctuation frequency was 0,6 ╠Hz. To smooth the fluctuation component of the effective phase velocities of the elastic waves we applied a balancing procedure using the properties of the first invariant of acoustic tensor. From the balanced phase - velocity values the regular and the fluctuation components of the effective acoustic and elastic tensors were calculated by the iteration method. The basis of the standard acoustic system of coordinates in which the elastic constants are presented coincided with the directions of the proper vectors of the acoustic tensor. The elastic constants were calculated in triclinic approximation which provided the best agreement between calculated and the experimental values of phase velocities. The elastic symmetry of the texture of granitoids is rhombic or triclinic (axial or planer). The textures with monoclinal symmetry were not distinguished. Using the method of relative moments we determined the effect of the form of anisotropic inclusion in an anisotropic matrix on the effective elastic constants of granitoids. The low elastic symmetry of the granitoid texture is explained by the non - coaxial predominant crystallographic orientation and orientation by the form of biotite, plagioclase, microcline and quartz as well as by the presence of intergrain microcrack systems. The elastic symmetry and anisotropy of granitoids is controlled by the conditions of their formation and the superposed deformations by their movement to the surface as a result of geodynamic processes.

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