Spectral time domain induced polarization : factors affecting spectral data information content and applicability to geological characterization

University essay from Lunds universitet/Geologiska institutionen

Abstract: The geo-electrical survey (resistivity and induced polarization) with different settings, arrangements, time base, spreads and waveforms (50% and 100% duty cycle waveform) was carried out over the Liikavaara depo-sit, near the Aitik mine, in northern Sweden and all the measured data was inverted in two different softwares: Res2Dinv and AarhusInv. Surveys of induced polarization (IP) often contain data of low quality, due to the high sensitivity against noise sources and coupling effects. Measured data with the new method (applying 100% duty cycle waveform), which is much faster than the conventional one (50% duty cycle waveform), present significant improvements in the quality of IP-data. It was also attempted to increase the data quality by separating current and potential cables and restrict the capacitive coupling, which normally occurs between transmitting current and pot-ential receiving wires. Moreover, conceptual models from different measurements were correlated to boreholes close to the survey line, in order to find geological correlation between the models and logging data. There was also a possibility of modeling Tau and C parameters by the newly developed software (AarhusInv) which gave us more detailed information about the mineralization texture (grain size and grain size distribution). They were also compa-red in different measurements and it appears that Tau and C are sensitive to the duration of current injection. However, lack of reference data for interpretation, made the interpretation of these two parameters, difficult and ambiguous.

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