Tectonic magnetic fabrics in pure and simple shear : experimental investigations

Abstract

Triaxial compression tests were preformed such that changes in the magnetic susceptibility anisotropy with strain would be represented by experimental approximations of simple shear and pure shear. Both types of tests were performed on artificial materials of high magnetic susceptibility at room temperature and atmospheric pore fluid pressure. Experimental displacement-rates and strain-rates were computer controlled during testing. Two different shear zone materials were employed for the "simple shear" testing, a sand-cement mixture and a calcite-cement mixture. Three series of simple shear tests were conducted on the sand-cement material at various confining pressures; Series A, at 0.689 kbars, Series B at 1.0 kbar and Series C at 1.5 kbars. Two series of simple shear tests were conducted on the calcite-cement material, Series 1, at 1.0 kbar confining pressure and Series 2 at 1.5 kbars Pc. For both materials a constant axial displacement-rate of 5.0x10-6 inches, s-1 (corresponding to a slip displacement-rate on the shear zone walls of 8.7x10-6 inches, s-1) was employed.