HELPING REDUCE THE RISK AND COST OF EXPLORATION UNDER COVER: INTRODUCING NEW CASE STUDY RESULTS FROM THE ONGOING DEVELOPMENT OF A SULFIDE TARGETING TOOL

Adrok have developed new hardware and processing methodologies to measure rock specific properties in the sub-surface prior to drilling and with an emphasis on delineating the presence of base metal sulfides.

This low frequency pulsed electromagnetic geophysical technique involves the measurement and interpretation of resonant energy responses of natural (or synthetic) materials to the interaction of the pulsed electromagnetic radio waves. Specifically, the technique measures and provides data on (i) dielectric permittivity; and (ii) spectral response (energy, frequency and phase). This is an exciting new field for geoscience as it provides a potential means of helping obtain critical information about, for example, the presence or absence of sulfides or water prior to drilling.

The EM waves are emitted by the transmitter antenna (Tx), and the reflected waves are recorded by the receiver antennae (Rx) at a scanning frequency range of between 1-70MHz. Both dielectric permittivity Ɛᵣ (related to EM wave velocity ν) and electrical conductivity σ (related to the attenuation of the EM wave α) can be linked to geologically relevant parameters, such as sulfide content. Over the past 10 years, Adrok have collected geophysical responses from across a swath of deposit types including, VHMS, SEDEX, Orogenic Gold and Porphyry. For each case, the host rock types are very different, but the presence of sulfides is a common feature of all sites. After collating the results, the signal response from the sulfides has be extracted from the variable background host-rock signal. Real-world examples from mine and exploration (brownfields) sites are presented showing specifically, the application of the new sulfide-specific targeting results is presented. The current iteration of the technique uses a set of correlation criteria, similar to the weights of evidence (WofE) technique, to provide a probability of sulfides at depths of up to and sometimes greater than 1000m depending on host rock type. The technique may prove useful for helping delineate the presence of sulfides prior to drilling new targets and therefore save exploration companies the time, expense and and potential environmental consequences of drilling brownfields- or potentially even greenfields-class targets. This research presents an exciting new and developing area for mineral or water exploration under cover.