Multifrequency electromagnetic response of a shielded conductor

Abstract

Multifrequency electromagnetic response of a composite overburden-ore system, theoretically represented by a concentric spherical two-shell model (in nongalvanic contact), has been obtained. Qualitative and quantitative comparisons of the total electromagnetic response of the composite system to the individual responses of the ore body (inner shell) and the overburden (outer shell) have been investigated for different parameteric combinations. Differential and/or relative contributions from the ore body and the overburden are predominantly reflected in the argand representation and gradient versus frequency variation curves. Argand diagrams have also been used to identify frequency zones characterizing complete shielding of the ore body and almost transparency of the overburden formations. Results may provide an aid:
(i) In understanding the shielding behaviour of the upper crustal formations (more particularly for delineating sulphur deposits buried in the ocean; exploring porphyry copper ores of alterations and mineralization zoning, and providing useful informations for the proper choice of the bore holes; mine openings, tunnellings, etc.) and
(ii) In the interpretation of the data collected by multispectral electromagnetic induction systems (viz. Geoprob EMR - 14).