2-D Audiomagnetotelluric Modelling of Ore Deposits - Improvements of Model Constraints by Inclusion of Borehole Measurem

Abstract

Summary A combination of audiomagnetotelluric (AMT) ground and borehole measurements can be expected to reduce the ambiguity in models of electrical resistivity as compared to models computed from ground data. We consider a synthetic 2-D model with a dipping mineralisation zone of ~ 1 Ohmm resistivity and 1.5 km depth extent embedded in a resistive host of 10000 Ohmm underneath weathered overburden of 100 Ohmm. 2-D inversion models derived from combinations of surface impedance measurements and borehole measurements in the form of horizontal magnetic transfer functions and vertical magnetic and electric transfer functions are compared. We observed that combinations of ground and borehole AMT measurements yield inversion models that have better pronounced resistivity contrasts at depth than models computed exclusively from surface measurements. To record the types of borehole AMT data suggested by us, 3-component borehole magnetometers sufficiently sensitive to the AMT magnetic field need to be developed. A miniaturised 3-component SQUID magnetometer may be a promising solution.