Quantitative estimation of intrinsic induced polarization and superparamagnetic parameters from airborne electromagnetic data

Macnae, James

doi:10.1190/geo2016-0110.1

Cited by 27 publications

(12 citation statements)

References 27 publications

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“…Inversion of the induction transients in terms of horizontally layered earth with σ * (ω) described by the Cole-Cole model has become a routine procedure (Kozhevnikov and Antonov, 2008;Kozhevnikov et al 2014;Seidel and Tezkan, 2017). In recent years, great progress has been made in the quantitative interpretation of airborne TEM surveys by taking into account the IP effects (Macnae 2015b(Macnae , 2016Viezzoli and Kaminski 2016). In recent years, great progress has been made in the quantitative interpretation of airborne TEM surveys by taking into account the IP effects (Macnae 2015b(Macnae , 2016Viezzoli and Kaminski 2016).…”

Section: Discussion a N D C O N C L U S I O N Smentioning

confidence: 99%

“…Some publications report on the inversion of TEM responses in terms of the three-dimensional distribution of frequency-dependent conductivity (Marchant et al 2013;Marchant, Haber and Oldenburg 2014). In recent years, great progress has been made in the quantitative interpretation of airborne TEM surveys by taking into account the IP effects (Macnae 2015b(Macnae , 2016Viezzoli and Kaminski 2016).…”

Section: Discussion a N D C O N C L U S I O N Smentioning

confidence: 99%

“…8(b) demonstrate the responses of a non-polarisable (m = 0) ring for both of the limiting conductivity values: σ 0 = 0.1 S/m and σ Ý = 0.2 S/m. According to Macnae (2016), these two conductivity values are referred to as, respectively, "steady or direct current" and "electromagnetic inductive" limits. On turning-on as well as turning-off the primary electric field, the current decays exponentially with a time constant of 4 μs (direct current limit) and 8 μs (electromagnetic inductive limit).…”

Section: N D U C T I V E L Y I N D U C E D P O L a R I Z A T I O Nmentioning

confidence: 99%

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Current and voltage source induced polarization transients: a comparative consideration

Kozhevnikov

Antonov

2017

Geophysical Prospecting

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The article discusses the excitation of transient induced polarization responses using current and voltage sources. The first method has found a wide application in induced polarization surveys and—directly or indirectly—in the theory of the induced polarization method. Typically, rectangular current pulses are injected into the earth via grounding electrodes, and decaying induced polarization voltage is measured during the pauses between pulses. In this case, only the secondary field is recorded in the absence of the primary field, which is an important advantage of this method. On the other hand, since the current injected into the ground is fully controlled by the source, this method does not allow studying induced polarization by measuring the current in the transmitter line or associated magnetic field. When energising the earth with voltage pulses, the measured quantity is the transient induced polarization current. In principle, this method allows induced polarization studies to be done by recording the transmitter line current, the associated magnetic field, or its rate of change. The decay of current in a grounded transmitter line depends not only on the induced polarization of the earth but also on the polarization of the grounding electrodes. This problem does not occur when induced polarization transients in the earth are excited inductively. A grounded transmitter line is a mixed‐type source; hence, for a purely inductive excitation of induced polarization transients, one should use an ungrounded loop, which is coupled to the earth solely by electromagnetic induction.

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Section: Discussion a N D C O N C L U S I O N Smentioning

confidence: 99%

Section: Discussion a N D C O N C L U S I O N Smentioning

confidence: 99%

Section: N D U C T I V E L Y I N D U C E D P O L a R I Z A T I O Nmentioning

confidence: 99%

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Current and voltage source induced polarization transients: a comparative consideration

Kozhevnikov

Antonov

2017

Geophysical Prospecting

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“…Even though it was interesting from a scientific standpoint, extracting meaningful information from those negative data remained challenging at the time. This is still an area of active research (Kang and Oldenburg, 2015;Viezzoli et al, 2015;Macnae, 2016), and the processing and interpretation of airborne IP data will be addressed in the final study of this three-part series on TKC. For the remainder of this paper we shall work only with data that we feel are not severely contaminated with IP signals.…”

Section: Tem Datamentioning

confidence: 99%

Inversion of airborne geophysics over the DO-27/DO-18 kimberlites — Part 2: Electromagnetics

et al. 2017

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We focus on the task of finding a 3D conductivity structure for the DO-18 and DO-27 kimberlites, historically known as the Tli Kwi Cho (TKC) kimberlite complex in the Northwest Territories, Canada. Two airborne electromagnetic (EM) surveys are analyzed: a frequency-domain DIGHEM and a time-domain VTEM survey. Airborne time-domain data at TKC are particularly challenging because of the negative values that exist even at the earliest time channels. Heretofore, such data have not been inverted in three dimensions. In our analysis, we start by inverting frequency-domain data and positive VTEM data with a laterally constrained 1D inversion. This is important for assessing the noise levels associated with the data and for estimating the general conductivity structure. The analysis is then extended to a 3D inversion with our most recent optimized and parallelized inversion codes. We first address the issue about whether the conductivity anomaly is due to a shallow flat-lying conductor (associated with the lake bottom) or a vertical conductive pipe; we conclude that it is the latter. Both data sets are then cooperatively inverted to obtain a consistent 3D conductivity model for TKC that can be used for geologic interpretation. The conductivity model is then jointly interpreted with the density and magnetic susceptibility models from a previous paper. The addition of conductivity enriches the interpretation made with the potential fields in characterizing several distinct petrophysical kimberlite units. The final conductivity model also helps better define the lateral extent and upper boundary of the kimberlite pipes. This conductivity model is a crucial component of the follow-up paper in which our colleagues invert the airborne EM data to recover the time-dependent chargeability that further advances our geologic interpretation.

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“…Investigations presented here compare the theoretical sensitivity of inductive AIP using a concentric loop system operated at 25 or 30 Hz with galvanic ground IP operated at 0.125 Hz. Macnae (2016) and Macnae and Hine (2016) tested this model on VTEM data sets from Tasmania and New South Wales, and showed that allowing for AIP effects greatly improved the error of fit to the data, and provided coherent maps of the Cole-Cole IP parameters chargeability m IP , time constant τ IP and frequency dependence c.…”

Section: Introductionmentioning

confidence: 99%

Airborne IP detects only fine-grained minerals when compared to conventional IP

Macnae

2016

ASEG Extended Abstracts

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Using a thin-sheet model, it is possible to predict Cole-Cole parameters of polarizable materials in the near-surface from airborne EM data. With the high frequency of AEM systems, typically more than 100 times higher than ground IP systems, most conventional IP targets will often not show an AIP response. Very fine-grained minerals, around 0.1 mm in average dimension, are however good sources for AIP responses. In 6 examples from Tasmania and NSW comparing AIP with ground IP, 5 have AIP responses that are not coincident with ground responses, but may detect finer grained minerals in the periphery of the alteration system associated with a mineral deposit.

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Quantitative estimation of intrinsic induced polarization and superparamagnetic parameters from airborne electromagnetic data

Cited by 27 publications

References 27 publications

Current and voltage source induced polarization transients: a comparative consideration

Current and voltage source induced polarization transients: a comparative consideration

Inversion of airborne geophysics over the DO-27/DO-18 kimberlites — Part 2: Electromagnetics

Airborne IP detects only fine-grained minerals when compared to conventional IP

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