HoistEM data processing for discovery of high grade manganese ore under regolith cover

Abstract

A time domain airborne electromagnetic (AEM) survey was flown with the HoistEM system over the Woodie Woodie manganese mine corridor in the east Pilbara of Western Australia. Conductivity depth image (CDI) processing and decay analysis helped to discriminate shallow, regolith related responses from conductive ore. EM conductivity mapping using CDIs correlated with about half of the known manganese ore zones, and recent drilling of several new EM targets in areas of regolith and bedrock cover discovered over 6 large tonnage manganese ore bodies to date. EMFlow has made it practical to process data gathered by HoistEM to separate the ore body response from conductive paleochannels and other conductive features related to bedrock geology or the regolith, for data editing to remove noise, and for experimentation with EMFlow parameters to produce more reliable results. The CDI results were further refined by calibration to borehole conductivity results. The survey testes and processing results demonstrate that HEM is a cost-effective method for exploration of podiform, high grade manganese ore bodies, as along as the host rocks are comparatively resistive and flight line spacing of 80m or less is used.