Notes on Piezo-Remanent Magnetization of Igneous Rocks II

Abstract

Various characteristics of piezo-remanent magnetization of igneous rocks are experimentally demonstrated in small magnetic fields, H=0∼10 Oe., and under uniaxial compression comparable to the earth's crust stress, 0∼100 kg/cm2. The main characteristics observed are as follows: (a) “After-effect” of uniaxial compression: JR(P+P0H+H0). After a rock sample is uniaxially compressed in a non-magnetic space by a pressure P larger than a certain critical value (Pc), its IRM, JR(P+P0H+H0), becomes larger than the ordinary IRM, JR(H+H0), without such a pressure treatment. This after-effect of pressure takes place in both cases of P//H and P⊥H. Here [d/dPJR(P+P0H+H0)]H=const>0 for P>Pc. (b) “Pressure demagnetization” effect: JR(H+H0P+P0). After uniaxially compressing a rock sample having IRM, JR(H+H0), in a non-magnetic space, the residual magnetization, JR(H+H0P+P0), becomes appreciably smaller than the original intensity of JR(H+H0) in both cases of P∥H and P⊥H. Here [formula omitted] (c) “Non-commutativity” of P and H. An inequality relationship expressed as [formula omitted] holds for all samples. In a magnetic field larger than a certain critical value, H*, [formula omitted]. JR(H+P+P0H0) and JR(P+H+P0H0) are always larger than JR(H+H0). The above argument holds in both cases of P∥H and P⊥H. © 1969, Society of Geomagnetism and Earth, Planetary and Space Sciences. All rights reserved.