A multiple parameter extraction and electromagnetic coupling correction technique for time domain induced polarisation full waveform data

ABSTRACT

The time domain induced polarisation (TDIP) method is characterised by a simple explanation and operational approach, and is used widely to prospect for various metal sulfide deposits. However, the existing TDIP method is parameterised with fewer interpretive output attributes than the frequency domain induced polarisation (FDIP) method, and there has been far less emphasis on electromagnetic (EM) coupling in the TDIP method. A new and simple method has been devised for the extraction of multiple parameters and the suppression of EM-coupling responses in full waveform TDIP data. The essence of this approach is the transformation of the TDIP rectangular wave into the fundamental wave and a series of odd harmonics using a discrete Fourier transform. By using real and imaginary components of the fundamental and odd harmonics, we can calculate various FDIP parameters, including the per cent frequency effect (PFE) and the phase. The decoupled PFE coefficients and decoupled phases can then be used to remove the EM-coupling response. This new method has been applied to a data set collected near a poly-metallic mine in the Tibetan Plateau. A comparison between the TDIP and FDIP methods with central gradient arrays was performed. The results indicate that the TDIP apparent chargeability results are affected greatly by the EM-coupling response. The PFEs and phases extracted from the TDIP full waveform data are in good agreement with those obtained from the FDIP data. Moreover, the locations of the high decoupled PFE coefficients and the large negative decoupled phases are consistent with the locations of known ore veins. This method can provide additional parameters for the subsurface media, improve the practical application effect and enrich the functionality of TDIP methods.

KEYWORDS:

• induced polarisation
• time domain
• frequency domain
• electromagnetic-coupling correction
• full waveform data

Acknowledgments

We acknowledge support by the National High Technology Research and Development Program (serial number: 2014AA06A610), Special funds for basic scientific research business expenses of the Chinese Academy of Geological Sciences (serial number: YYWF201632), National Key R&D Program of China (serial number: 2018YFC0603201) and the National Major Scientific Instruments and Equipment Development Projects (serial number: 2011YQ050060). We are grateful to Dr Changzheng Liu, Fifth Institute of Geology and Mineral Resources of Qinghai Province, for help. Thanks to all the staff members involved in the data collection and processing.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

We acknowledge support by the National High Technology Research and Development Program (serial number: 2014AA06A610), Special funds for basic scientific research business expenses of the Chinese Academy of Geological Sciences (serial number: YYWF201632), National Key R&D Program of China (serial number: 2018YFC0603201) and the National Major Scientific Instruments and Equipment Development Projects (serial number: 2011YQ050060).