Airborne IP: examples from the Mount Milligan deposit, Canada, and the Amakinskaya kimberlite pipe, Russia

Abstract

There have been multiple occurrences in the literature in the past several years of what has been referred to as the induced polarisation (IP) effect in airborne time domain electromagnetic (TDEM) data. This phenomenon is known to be responsible for incorrect inversion modelling of electrical resistivity, lower interpreted depth of investigation (DOI) and lost information about chargeability of the subsurface and other valuable parameters. Historically, there have been many suggestions to account for the IP effect using the Cole-Cole model. It has been previously demonstrated that the Cole-Cole model can be effective in modelling synthetic TDEM transients. In the current paper we show the possibility of extracting IP information from airborne TDEM data using this same concept, including inverse modelling of chargeability from TDEM data collected by VTEM, with field examples from Canada (Mt Milligan deposit) and Russia (Amakinskaya kimberlite pipe).

There has been evidence of the IP effect in TDEM data. This phenomenon is known to be responsible for incorrect inversion modelling of electrical resistivity, lower DOI and lost information about chargeability. In the current paper, we show the possibility of extracting IP information from VTEM data using Cole-Cole modelling.

Key words::

• airborne EM, airborne IP, inversion, kimberlite, mineral exploration, modelling, porphyry.

Acknowledgements

We would like to thank Alrosa for providing us with the VTEM data from north-eastern Russia. We would also like to thank Geoscience BC for providing the VTEM dataset over the Mt Milligan deposit in western Canada.