Is full 3-D Inversion Necessary for Interpreting EM Data?

Stolz, Ned; Raiche, Art; Sugeng, Fred; Macnae, James

doi:10.1071/eg995167

Cited by 4 publications

(3 citation statements)

References 11 publications

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“…For EM methods, Kambalda-style models have been the subject of previous 3-D EM forward modeling studies such as Stolz et al (1995) and Zhdanov et al (2000). However, there are specific limitations on EM methods for the practical exploration of Kambalda-style NiS exploration in Australia and these are imposed by the following factors (Trench and Williams, 1994): a) the generally small size of the deposits (0.5 to 3.0 Mt); b) the extreme depth of weathering in the regolith; and c) the abundance of anomalous responses from noneconomic targets.…”

Section: The Generalized Minimal Residual Methodsmentioning

confidence: 99%

New Geophysical Technique for Mineral Exploration and Mineral Discrimination Based on Electromagnetic Methods

Zhdanov¹

2009

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The research during the first two years of the project was focused on developing the foundations of a new geophysical technique for mineral exploration and mineral discrimination, based on electromagnetic (EM) methods. The developed new technique is based on examining the spectral induced polarization effects in electromagnetic data using effective-medium theory and advanced methods of 3-D modeling and inversion.The analysis of IP phenomena is usually based on models with frequency dependent complex conductivity distribution. In this project, we have developed a rigorous physical/mathematical model of heterogeneous conductive media based on the effective-medium approach. The new generalized effective-medium theory of IP effect (GEMTIP) provides a unified mathematical method to study heterogeneity, multi-phase structure, and polarizability of rocks. The geoelectrical parameters of a new composite conductivity model are determined by the intrinsic petrophysical and geometrical characteristics of composite media: mineralization and/or fluid content of rocks, matrix composition, porosity, anisotropy, and polarizability of formations. The new GEMTIP model of multi-phase conductive media provides a quantitative tool for evaluation of the type of mineralization, and the volume content of different minerals using electromagnetic data.We have developed a 3-D EM-IP modeling algorithm using the integral equation (IE) method. Our IE forward modeling software is based on the contraction IE method, which improves the convergence rate of the iterative solvers. This code can handle various types of sources and receivers to compute the effect of a complex resistivity model. We have demonstrated that the generalized effective-medium theory of induced polarization (GEMTIP) in combination with the IE forward modeling method can be used for rock-scale forward modeling from grain-scale parameters. The numerical modeling study clearly demonstrates how the various complex resistivity models manifest differently in the observed EM data. These modeling studies lay a background for future development of the IP inversion method, directed at determining the electrical conductivity and the intrinsic chargeability distributions, as well as the other parameters of the relaxation model simultaneously. The new technology introduced in this project can be used for the discrimination between uneconomic mineral deposits and the location of zones of economic mineralization and geothermal resources.

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Section: The Generalized Minimal Residual Methodsmentioning

confidence: 99%

New Geophysical Technique for Mineral Exploration and Mineral Discrimination Based on Electromagnetic Methods

Zhdanov¹

2009

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“…As described by Stone and Masterman (1998), Kambalda-style orebodies occur at, or close to, the basal contact between the lowermost komatiite flow (ultramafic) and footwall metabasalts (mafic). The NiS ore is comprised of basal massive, matrix and disseminated sulfide ores within which the nickel grade decreases upward.…”

Section: -D Modelsmentioning

confidence: 99%

Section: -D Modelsmentioning

confidence: 99%

New Geophysical Technique for Mineral Exploration and Mineral Discrimination Based on Electromagnetic Methods

Zhdanov¹

2005

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The research during the first year of the project was focused on developing the foundations of a new geophysical technique for mineral exploration and mineral discrimination, based on electromagnetic (EM) methods. The proposed new technique is based on examining the spectral induced polarization effects in electromagnetic data using modern distributed acquisition systems and advanced methods of 3-D inversion.The analysis of IP phenomena is usually based on models with frequency dependent complex conductivity distribution. One of the most popular is the Cole-Cole relaxation model. In this progress report we have constructed and analyzed a different physical and mathematical model of the IP effect based on the effective-medium theory. We have developed a rigorous mathematical model of multi-phase conductive media, which can provide a quantitative tool for evaluation of the type of mineralization, using the conductivity relaxation model parameters. The parameters of the new conductivity relaxation model can be used for discrimination of the different types of rock formations, which is an important goal in mineral exploration. The solution of this problem requires development of an effective numerical method for EM forward modeling in 3-D inhomogeneous media. During the first year of the project we have developed a prototype 3-D IP modeling algorithm using the integral equation (IP) method. Our IE forward modeling code IN-TEM3DIP is based on the contraction IE method, which improves the convergence rate of the iterative solvers. This code can handle various types of sources and receivers to compute the effect of a complex resistivity model. We have tested the working version of the INTEM3DIP code for computer simulation of the IP data for several models including a southwest US porphyry model and a Kambalda-style nickel sulfide deposit. The numerical modeling study clearly demonstrates how the various complex resistivity models manifest differently in the observed EM data. These modeling studies lay a background for future development of the IP inversion method, directed at determining the electrical conductivity and the intrinsic chargeability distributions, as well as the other parameters of the relaxation model simultaneously. The new technology envisioned in this proposal, will be used for the discrimination of different rocks, and in this way will provide an ability to distinguish between uneconomic mineral deposits and the location of zones of economic mineralization and geothermal resources.

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Block modelling as a check on the interpretation of stitched CDI sections from AEM data

Macnae

Xiong

1998

Exploration Geophysics

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Is full 3-D Inversion Necessary for Interpreting EM Data?

Cited by 4 publications

References 11 publications

New Geophysical Technique for Mineral Exploration and Mineral Discrimination Based on Electromagnetic Methods

New Geophysical Technique for Mineral Exploration and Mineral Discrimination Based on Electromagnetic Methods

New Geophysical Technique for Mineral Exploration and Mineral Discrimination Based on Electromagnetic Methods

Block modelling as a check on the interpretation of stitched CDI sections from AEM data

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