scholarly journals ANALYSIS OF COMPLEX APPARENT RESISTIVITY DATA CONJUGATING SPECTRAL INDUCED POLARIZATION AND ELECTROMAGNETIC COUPLING

2018 ◽  
Vol 36 (3) ◽  
pp. 1
Author(s):  
Taíla Crístia Souza Sant’Ana ◽  
Edson Emanoel Starteri Sampaio
Keyword(s):  
Apparent Resistivity ◽  
Mineral Exploration ◽  
Electromagnetic Coupling ◽  
Synthetic Data ◽  
Polarization Characteristic ◽  
Induced Polarization ◽  
Forward Modelling ◽  
New Approach ◽  
Spectral Induced Polarization ◽  
Geological Information

ABSTRACT. The induced polarization characteristic is to provide geophysical and geological information via geoelectric parameters, making possible mineral discrimination in the scope of mineral exploration. Although represents one of the main noises in measurements of this method, electromagnetic coupling between current and potential electrodes also contributes to the understanding of the geological scenario. Thus, the most appropriate way to deal with such data is an integrated study of these two phenomena, taking into account their particularities. Forward modelling and Gauss-Newton inversion of the mutual impedance in the frequency domain provide the analysis of the complex apparent resistivity considering both spectral induced polarization and electromagnetic coupling for homogeneous and one-dimensional, non-polarizable and polarizable Earth models. Besides synthetic data, this new approach was applied to data from the Copper District of Vale do Curaçá, Bahia, Brazil. The results reveal the ability of the method to distinguish between induction, dominant at the highest frequencies, and induced polarization, which varies with depth and frequency. It also may constitute a basis for mineral discrimination with the analysis of analogous circuit parameters, a fundamental tool in the search for metallic targets in mineral exploration.Keywords: Forward Modelling, Geophysical Inversion, Electromagnetic Method, Mineral Exploration.RESUMO. A polarização induzida espectral se destaca por fornecer diversas informações geofísico-geológicas através dos parâmetros geoelétricos, viabilizando a discriminação mineral no âmbito da exploração mineral. Embora constitua um dos principais ruídos nas medidas desse método, o acoplamento eletromagnético entre eletrodos de corrente e potencial também auxilia na compreensão do cenário geológico. Dessa forma, a maneira mais adequada de lidar com tais dados espectrais é o estudo integrado desses dois fenômenos, levando em conta suas particularidades. A modelagem direta e a inversão Gauss-Newton da impedância elétrica mútua no domínio da frequência proporcionam a análise da resistividade complexa aparente considerando tanto a polarização induzida espectral como o acoplamento eletromagnético para modelos de terra homogênea e uni-dimensional, polarizável e não-polarizável. Além do dado sintético, essa nova abordagem foi aplicada a dados reais do Distrito Cuprífero do Vale do Curaçá, Bahia, Brasil. Os resultados revelam a capacidade do método em distinguir o efeito indutivo, dominante nas mais altas frequências, e a variação da polarização induzida com a profundidade e frequência. Isso contitui um estudo base para a discriminação mineral por meio da análise de parâmetros de circuitos análogos, uma ferramenta fundamental na investigação de alvos em exploração mineral.Palavras-chave: Modelagem direta, Inversão Geofísica, Método Eletromagnético, Exploração Mineral. 1Universidade

Investigating cable effects in spectral induced polarization imaging at the field scale using multicore and coaxial cables

Geophysics ◽  
2020 ◽  
pp. 1-49
Author(s):  
Adrian Flores Orozco ◽  
Lukas Aigner ◽  
Jakob Gallistl
Keyword(s):  
Signal To Noise Ratio ◽  
Electromagnetic Coupling ◽  
Induced Polarization ◽  
Coaxial Cable ◽  
Imaging Method ◽  
Data Sets ◽  
Phase Lag ◽  
Imaging Data ◽  
Measuring Device ◽  
Spectral Induced Polarization

The Spectral Induced Polarization (SIP) method has emerged as a well-suited laboratory technique to characterize hydrogeological and biogeochemical parameters in soil samples. However, field applications of the SIP imaging method are still rare, which can be attributed to the particular care required to minimize the contamination of the data by electromagnetic coupling. To date, field procedures rely on the use of two different cables separating the current and potential dipoles to improve the quality of the SIP readings, although this increases the efforts in the field and might reduce the depth of investigation or the spatial resolution of the data. To overcome these limitations, we investigate here the use of a single coaxial cable, as an alternative to improve data quality and simplify field procedures. We present a thoughtful evaluation of SIP imaging data collected with the same measuring device using a coaxial cable and a combination of multicore cables of different length and manufacturers. Data sets collected with a single coaxial cable reveal a significantly lower number of outliers and high spatial consistency between the phase-lag readings, even for measurements collected with a coaxial cable five times longer than the length of the profile. Furthermore, the data collected with coaxial cables reveal an improved quality for deeper measurements (with lower signal-to-noise ratio) in comparison to data sets collected with separated cables. Our results demonstrate that the use of coaxial cables might permit the collection of SIP readings with high quality and similar field procedures to those used in resistivity surveys.

Cable arrangement to reduce electromagnetic coupling effects in spectral-induced polarization studies

Geophysics ◽  
2014 ◽  
Vol 79 (2) ◽  
pp. A1-A5 ◽  
Author(s):  
Myriam Schmutz ◽  
Ahmad Ghorbani ◽  
Pierre Vaudelet ◽  
Amélie Blondel
Keyword(s):  
Coupling Effect ◽  
Electromagnetic Coupling ◽  
Induced Polarization ◽  
Electrode Spacing ◽  
Coupling Effects ◽  
Array Type ◽  
Spectral Induced Polarization ◽  
Computer Codes ◽  
Lateral Offset ◽  
Phase Angles

Spectral-induced polarization (SIP) is widely used for environmental and engineering geophysical prospecting and hydrogeophysics, but one major limitation concerns the electromagnetic (EM) coupling effect. The phase angles related to EM coupling may increase even at frequencies as low as 1 Hz, depending on the ground resistivity, the array type, and the geometry. Most efforts to understand and quantify the EM coupling problem (e.g., theory and computer codes) have been developed for dipole-dipole arrays. However, we used a Schlumberger array to acquire SIP data. We found that with this array, the use of an appropriate cable arrangement during data acquisition can reduce EM coupling effects in the same proportion as for the use of a dipole-dipole array, which is the pure response of the studied earth. To measure the influence of the cable layout, four cable configurations with the same electrode spacing were compared for modeling and experimental data. We discovered that the classical DC inline array was the worst one. As soon as the cables were arranged in another shape (triangle or rectangle), the coupling effect decreased significantly. The best configuration we checked was the rectangular one with an acquisition unit located at a lateral offset of 100 m from the electrode line, even if there was still some difference between the modeled and measured data.

scholarly journals Spectral Induced Polarization imaging to investigate an ice-rich mountain permafrost site in Switzerland

2021 ◽  
Author(s):  
Theresa Maierhofer ◽  
Christian Hauck ◽  
Christin Hilbich ◽  
Andreas Kemna ◽  
Adrián Flores-Orozco
Keyword(s):  
Electromagnetic Coupling ◽  
Spectral Response ◽  
Induced Polarization ◽  
Swiss Alps ◽  
Spatial Extent ◽  
Data Uncertainty ◽  
Monitoring Site ◽  
Imaging Data ◽  
Spectral Induced Polarization ◽  
Talus Slope

Abstract. Spectral induced polarization (SIP) measurements were collected at the Lapires talus slope, a long-term permafrost monitoring site located in the Western Swiss Alps, to assess the potential of the frequency dependence (within the frequency range of 0.1–225 Hz) of the electrical polarization response of frozen rocks for an improved permafrost characterization. The aim of our investigation was to (a) find a field protocol that provides SIP imaging data sets less affected by electromagnetic coupling and easy to deploy in rough terrains, (b) cover the spatial extent of the local permafrost distribution, and (c) evaluate the potential of the spectral data to discriminate between different substrates and spatial variations in the volumetric ice content within the talus slope. To qualitatively assess data uncertainty, we analyze the misfit between normal and reciprocal (N&R) measurements collected for all profiles and frequencies. A comparison between different cable setups reveals the lowest N&R misfits for coaxial cables and the possibility to collect high-quality SIP data in the range between 0.1–75 Hz. We observe an overall smaller spatial extent of the ice-rich permafrost body compared to its assumed distribution from previous studies. Our results further suggest that SIP data help to improve the discrimination between ice-rich permafrost and unfrozen bedrock in ambiguous cases based on their characteristic spectral behavior, with ice-rich areas showing a stronger polarization towards higher frequencies in agreement with the well-known spectral response of ice.

scholarly journals An experiment of spectral induced polarization

1994 ◽  
Vol 37 (5 Sup.) ◽  
Author(s):  
B. Balia ◽  
G. P. Deidda ◽  
A. Godio ◽  
G. Ranieri ◽  
L. Sambuelli ◽  
...  
Keyword(s):  
Grain Size ◽  
Apparent Resistivity ◽  
Mineral Content ◽  
Test Site ◽  
Induced Polarization ◽  
Mineral Deposits ◽  
Axial Dipole ◽  
Spectral Induced Polarization ◽  
And Inversion ◽  
Phase Spectra

A Spectral Induced Polarization (SIP) survey was carried out in a mining test site in Sardinia (Italy). Measurements were developed along a profile by using an axial dipole-dipole array with 10 AB positions and 6 MN positions for cach AB. The amplitude and phase spectra of the apparent resistivity were acquired in the 0.25-4096 Hz frequeney range. The results obtained through the processing and inversion step seem to confirm that, with respect to the classical TD/FD Induced Polarization, SIP allows better discrimination of some important characteristics of mineral deposits such as mineral content and grain size.

Mineralogical and textural controls on spectral induced polarization signatures of the Canadian Malartic gold deposit: Applications to mineral exploration

Geophysics ◽  
2019 ◽  
Vol 84 (2) ◽  
pp. B135-B151 ◽  
Author(s):  
Charles L. Bérubé ◽  
Gema R. Olivo ◽  
Michel Chouteau ◽  
Stéphane Perrouty
Keyword(s):  
Gold Deposit ◽  
Mineral Exploration ◽  
Sedimentary Rocks ◽  
Sulfide Mineral ◽  
Induced Polarization ◽  
Spectral Induced Polarization ◽  
Mineral Phases ◽  
Mineralized Zone ◽  
Mineral Interfaces ◽  
Liberation Analysis

Applications of the spectral induced polarization (SIP) method to mineral exploration are limited by our knowledge of the relationships among rock texture, mineral composition, and electrical properties. Laboratory SIP responses were measured on rock samples from the Canadian Malartic gold deposit. Field SIP responses were also measured at the outcrop scale, along a profile that intersects a well-studied mineralized zone. The mineralogy and the texture of sedimentary rocks from this deposit were quantitatively determined with mineral liberation analysis. A systematic decrease (Pearson [Formula: see text]) in total chargeability with increasing fraction of the sulfide mineral interfaces associated with feldspar minerals (namely, K-feldspar and albite) was observed. On the other hand, total chargeability increased with the fraction of sulfide mineral interfaces associated with carbonates and micas (Pearson [Formula: see text]). At Canadian Malartic, proximal alteration in the mineralized zones is marked by rocks that lack a foliation plane and that were subjected to pervasive K-feldspar, albite, and pyrite alteration. In contrast, distal alteration in sedimentary rocks is marked by biotite, albite, carbonate, and pyrite that are oriented along the regional [Formula: see text] foliation. In the least-altered (LA) sedimentary rocks, quartz and biotite are associated with pyrrhotite and ilmenite as the main sulfide and oxide mineral phases, respectively. SIP measurements conducted at district and outcrop scales and along a drill core indicated that proximally altered sedimentary rocks were characterized by low total chargeability values ([Formula: see text] to [Formula: see text] in the laboratory and [Formula: see text] in the field). In contrast, the LA sedimentary rocks were characterized by total chargeability values up to [Formula: see text] in the laboratory and [Formula: see text] in the field. We conclude that mineralized zones associated with this type of ore deposit are characterized by low chargeability anomalies.

Markov-chain Monte Carlo estimation of distributed Debye relaxations in spectral induced polarization

Geophysics ◽  
2012 ◽  
Vol 77 (2) ◽  
pp. E159-E170 ◽  
Author(s):  
John Keery ◽  
Andrew Binley ◽  
Ahmed Elshenawy ◽  
Jeremy Clifford
Keyword(s):  
Porous Media ◽  
Monte Carlo ◽  
Markov Chain ◽  
Markov Chain Monte Carlo ◽  
Physical Properties ◽  
Relaxation Times ◽  
Synthetic Data ◽  
Induced Polarization ◽  
Posterior Distributions ◽  
Spectral Induced Polarization

There is growing interest in the link between electrical polarization and physical properties of geologic porous media. In particular, spectral characteristics may be controlled by the same pore geometric properties that influence fluid permeability of such media. Various models have been proposed to describe the spectral-induced-polarization (SIP) response of permeable rocks, and the links between these models and hydraulic properties have been explored, albeit empirically. Computation of the uncertainties in the parameters of such electrical models is essential for effective use of these relationships. The formulation of an electrical dispersion model in terms of a distribution of relaxation times and associated chargeabilities has been demonstrated to be an effective generalized approach; however, thus far, such an approach has only been considered in a deterministic framework. Here, we formulate a spectral model based on a distribution of polarizations. By using a simple polynomial descriptor of such a distribution, we are able to cast the model in a stochastic manner and solve it using a Markov-chain Monte Carlo (McMC) sampler, thus allowing the computation of model-parameter uncertainties. We apply the model to synthetic data and demonstrate that the stochastic method can provide posterior distributions of model parameters with narrow bounds around the true values when little or no noise is added to the synthetic data, with posterior distributions that broaden with increasing noise. We also apply our model to experimental measurements of six sandstone samples and compare physical properties of a number of samples of porous media with stochastic estimates of characteristic relaxation times. We demonstrate the utility of our method on electrical spectra with different response characteristics and show that a single metric of relaxation time for the SIP response is not sufficient to provide clear insight into the physical characteristics of a sample.

Induced Polarization and Resistivity of Second Potential Differences (SPD) with Focused Sources Applied to Environmental Problems

2019 ◽  
Vol 24 (1) ◽  
pp. 49-61
Author(s):  
Aide E. López-González ◽  
Andrés Tejero-Andrade ◽  
Jejanny L. Hernández-Martínez ◽  
Blanca Prado ◽  
René E. Chávez
Keyword(s):  
Apparent Resistivity ◽  
Electromagnetic Coupling ◽  
Random Noise ◽  
Horizontal Layer ◽  
Induced Polarization ◽  
Masking Effect ◽  
Synthetic Model ◽  
Survey Results ◽  
Agricultural Site ◽  
Noise Contamination

A novel technique is proposed to improve shallow induced polarization (IP) and resistivity survey results. We propose the apparent resistivity and apparent chargeability of second potential differences (SPD), employing two focused sources (FS) mathematically manipulated by superposition. To test the idea, a synthetic model is developed with two bodies. The first body is a small shallow heterogeneity which is above the second and larger body. This synthetic model illustrates the shape and response of the apparent resistivity and chargeability for FS under the random noise and masking effect. These processes reduce electromagnetic coupling, telluric noise, contamination in channel links, and small heterogeneous responses. A field test of the SPD for FS was carried out in an agricultural site irrigated with wastewater, where contaminated water laden with metals has been accumulating for years in the soil. Soil samples were collected and analyzed throughout the geophysical survey to correlate the resistivity-IP results. Soil laboratory analysis included metal content, moisture content and texture. The parameters computed after applying the SPD for FS depicted a better lateral resolution where vertical and horizontal boundaries of the anomaly zones were well defined. It was possible to determine the low permeability horizontal layer made of clay-soil (called tepetate), which is a barrier for water and metals.

scholarly journals Apparent resistivity and spectral induced polarization in the submarine environment

2001 ◽  
Vol 73 (3) ◽  
pp. 429-444 ◽  
Author(s):  
HERCULES DE SOUZA ◽  
EDSON E. S. SAMPAIO
Keyword(s):  
Electric Field ◽  
Apparent Resistivity ◽  
Sea Water ◽  
Induced Polarization ◽  
Sea Surface ◽  
Spectral Induced Polarization ◽  
Sea Bottom ◽  
Different Levels ◽  
Research Show

Relatively few investigations have employed electrical methods in the submarine environment, which may be promising for mineral deposits or threatened by environmental problems. We have measured the electric field using both disk and bar electrodes in the sea water at three different levels: sea surface, seven meters deep, and sea bottom at a depth of ten meters, employing a 2 m spacing dipole-dipole array with 7 array spacings of investigation, and 13 values of frequencies at steps of (2N hertz, N = -2, -1, 0, 1, 2,.....10). The measurement allowed the analysis of the electric field as a function of frequency and spacing, and of the spectral induced polarization. Modelling and interpretation of the apparent resistivity yielded a good fit with previous drilling data. Analysis of the spectrum of the complex apparent resistivity and the comparison with equivalent circuits, provided information about the grain size, the mineral composition and the major induced polarization phenomenon occurring below the sea. Therefore the result of the present research show the feasibility of measuring the variation of seawater resistivity in situ, as well as the resistivity of sea bottom sediments.

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