The interpretation of induced polarization surveys.

Current interpretation methods, research and field practice are reviewed, followed by a description of laboratory apparatus and methods for time and frequency domain measurements on samples and models, and a 300 watt time domain field unit. Time domain measurements on 69 samples indicate the following. The rate of change in polarizability with varying changing time or current density is greater for membrane than for metallic polarizers. The changing time behavior is significantly different and may be of diagnostic value. Fluvioglacial sands have similar I.P. properties to alluvial sands studied by other workers. A theoretical function given by Anderson and Keller (1964), relating polarizability and clay content of such sands is empirically verified. Serpentine and chlorite minerals in altered basic igneous rocks can give rise to large polarizabilities. Metallic polarizers rarely have R values in excess of 2.36 where R is the ratio of the 1 second and 5 second transient voltages, Membrane R values can exceed this figure but are also commonl lower. 94 scale model cases are presented. A number of empirical relationships useful for direct interpretation of gradient array polarizability anomalies are derived. They agree with analogous theoretical functions for simple charge configurations derived using elementary potential theory. These functions are equivalent to the magnetic case. It is demonstrated that direct techniques of total or vertical field interpretation can be applied. Scale model transient R values vary both from place to place over a body with a constant geometry of polarization, and with changing geometry of polarization. At the present sensitivity of I.P. field gear the method is not applicable to the field study of glacial deposits due to the lack of a widespread polarizing lithology. A scheme for the interpretation of multilayer resistivity and polarizability Wenner depth probes is given.