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Minerals
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Using Geophysical Inversion for Mineral Exploration: Methods and Applications
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Using Geophysical Inversion for Mineral Exploration: Methods and Applications

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Exploration Methods and Applications".

Deadline for manuscript submissions: closed (25 December 2023) | Viewed by 11089

Special Issue Editors

Dr. Vikas C. Baranwal

E-Mail Website
Guest Editor
Geological Survey of Norway (NGU), 7491 Trondheim, Norway
Interests: integration of geophysical methods; airborne geophysics; mineral exploration; environmental and geohazard applications
Dr. Bjørn Henning Heincke

E-Mail Website
Co-Guest Editor
Geological Survey of Denmark and Greenland (GEUS), 1350 København, Denmark
Interests: mineral exploration geophysics; near-surface geophyics; joint and constrained inversion
Dr. Dikun Yang

E-Mail Website
Co-Guest Editor
Department of Earth and Space Sciences, Southern University of Science and Technology, Shenzhen 518055, China
Interests: electromagnetic methods; geophysical modeling and inversion; resource exploration

Special Issue Information

Dear Colleagues,

The shift to green technology enormously increases the global demand for critical commodities. This makes it necessary to improve nowadays mineral exploration techniques and strategies to both increase the success rate for finding new economic deposits and to exploit resources that were inaccessible in the past. To achieve this, many different types of geoscience data and information are combined in advanced multi-methodologically approaches to develop complex high-resolution exploration models in modern mineral exploration. Geophysical methods play a central role in such kind of exploration since they allow non-invasive systematic surveying, and often have a significant depth penetration. They provide insightful geological information as 2D and 3D physical models. Sometimes, geophysical anomalies are even directly sensitive to the target mineralization and can give information about the location, size, shape, and type of a deposit.

Most geophysical methods that have been successfully used in mineral exploration for a long time use the concept of inversion to reconstruct physical parameter distributions in the subsurface from the measured data. Geophysical inversion techniques are developing very fast for providing useful models for geological interpretations and in defining the targets for mineral exploration from various geophysical data. With an increasing capability of computing devices, 3D inversion of large geophysical datasets is possible now, which was a very difficult task few decades ago. Geophysical inversion methods and their use in mineral exploration stretch to a vast area of local (iterative and linearized inversion) and global optimization inversion (stochastic inversion) and consider even applications of machine learning—both directly in the inversion or indirectly in interpretation of the inverted data. Much effort has also been made to improve the resolution of inversion results and accordingly to make their models more reliable for geological interpretation by combining data either from different geophysical methods (joint inversions) or by integrating geophysical data with other geoscience data (e.g., constrained inversions).   

In this special issue, we are inviting papers that deal with geophysical inversion developments (e.g., improved resolution, meaningful geological constraints, joint inversion) to all types of geophysical methods (e.g., gravity, magnetic, electrical and electromagnetic methods, seismic methods and even remote sensing methods such as hyperspectral imaging) and surveys (e.g., airborne, ground, offshore and borehole) and their applications in defining the mineral exploration targets in case studies. This also includes contributions for inversion techniques applied for deep-seated and unconventional mineral deposits e.g., marine sulfides.

Dr. Vikas C. Baranwal
Dr. Bjørn Henning Heincke
Dr. Dikun Yang
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Minerals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • electrical and electromagnetic methods
  • gravity and magnetic methods
  • Induced polarization (IP)
  • seismic methods
  • airborne geophysics
  • ground-based and borehole geophysics
  • 3-D inversion
  • inversion-guided interpretations
  • joint and constrained inversions
  • integrated geophysical approaches
  • onshore and offshore mineral exploration
  • deep sea mining
  • non-conventional deposit

Published Papers (7 papers)

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Research

18 pages, 35994 KiB  
Article
A Case History of Graphite Exploration in North Norway Integrating Various Geophysical Surveys
by Vikas Chand Baranwal, Jan Steinar Rønning, Bjørn Eskil Larsen, Yang Su, Bo Zhang, Yunhe Liu, Xiuyan Ren, Håvard Gautneb and Jomar Gellein
Minerals 2024, 14(3), 266; https://doi.org/10.3390/min14030266 - 2 Mar 2024
Viewed by 982
Abstract
Graphite is considered to be one of Europe’s most critical minerals. It is necessary for the transition from hydrocarbon fuel to electricity due to its use in batteries that power electronic devices and electric transport. In the past, high-quality exposed graphite was found [...] Read more.
Graphite is considered to be one of Europe’s most critical minerals. It is necessary for the transition from hydrocarbon fuel to electricity due to its use in batteries that power electronic devices and electric transport. In the past, high-quality exposed graphite was found in Norway without today’s advanced geophysical and geological methods. Norway is a key destination in Europe for graphite production. With an increasing demand for graphite, there have been efforts to systematically survey the country using modern geophysical and geological methods to find hidden graphite deposits. Among the various geophysical survey methods, electrical and electromagnetic (EM) methods are the first choice for the exploration of graphite due to the material’s high electrical conductivity. Airborne surveys are often used to cover a large area for a regional reconnaissance survey to locate the sites with potential mineral deposits before performing ground geophysical and geological surveys. Therefore, frequency-domain helicopter EM (HEM) and airborne magnetic surveys were performed in Northern Norway to locate interesting anomalies which were followed by ground surveys such as electrical resistivity tomography (ERT), charged-potential (CP), self-potential (SP), ground EM, and geological surveys. Some locations were also investigated with drilling and petrophysical core-sample analysis. In this paper, we present helicopter EM and magnetic data, 3D inversion of HEM data, and a successful ground follow-up survey result from the Vesterålen district in Northern Norway. The HEM survey identified previously known and new graphite occurrences, both partially exposed or buried, which were confirmed using ground surveys, drilling, and laboratory analysis of the samples. Full article
(This article belongs to the Special Issue Using Geophysical Inversion for Mineral Exploration: Methods and Applications)
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19 pages, 9441 KiB  
Article
Estimation of Geotechnical Parameters for Coal Exploration from Quasi-3D Electrical Resistivity Measurements
by Rupesh Rupesh, Prarabdh Tiwari and Shashi Prakash Sharma
Minerals 2024, 14(1), 102; https://doi.org/10.3390/min14010102 - 17 Jan 2024
Cited by 1 | Viewed by 967
Abstract
Geotechnical parameters are crucial for mine planning and operation at different stages of development. However, estimating these parameters requires a large number of boreholes and subsequent detailed analysis of the samples, making it a cumbersome exercise. Moreover, even after conducting these studies, it [...] Read more.
Geotechnical parameters are crucial for mine planning and operation at different stages of development. However, estimating these parameters requires a large number of boreholes and subsequent detailed analysis of the samples, making it a cumbersome exercise. Moreover, even after conducting these studies, it is not possible to cover the entire operational area. To address this issue, this study presents an indirect method of estimating geotechnical parameters through mathematical relations using resistivity data. The present study incorporated 2D and 3D subsurface imaging techniques for exploring coal reserves and analyzing geotechnical parameters that define subsurface soil properties. Electrical resistivity tomography (ERT) was utilized for data acquisition, employing a Dipole–dipole array with a multielectrode ABEM Terrameter LS instrument. Six parallel profiles were conducted, each 400 m in length, with an inter-electrode spacing of 10 m and a spacing of 50 m between profiles. These profiles were combined into a 3D dataset referred to as quasi-3D ERT. The inversion process for both 2D and 3D data was performed using the Res2dinv and Res3dinv programs, respectively. This study overcame the challenges of 2D resistivity sections by evaluating horizontal depth slices in the x-z plane from layers 1 to 10, reaching a depth of 81.2 m. The geotechnical parameters, including cohesion, friction angle, moisture content, and plastic index, were derived from the resistivity data. The ERT method proved to be cost-effective and efficient in determining soil properties over a large area compared with traditional laboratory analysis of borehole samples. Additionally, the variation of geotechnical parameters with resistivity values exhibited unique characteristics. The results from both the 2D and quasi-3D ERT were well correlated with the borehole data. Such studies are valuable for resource exploration and mine planning purposes. Full article
(This article belongs to the Special Issue Using Geophysical Inversion for Mineral Exploration: Methods and Applications)
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28 pages, 12027 KiB  
Article
New Insights into the Gold Mineralization in the Babaikundi–Birgaon Axis, North Singhbhum Mobile Belt, Eastern Indian Shield Using Magnetic, Very Low-Frequency Electromagnetic (VLF-EM), and Self-Potential Data
by Dharmita Horo, Sanjit Kumar Pal, Sahendra Singh and Arkoprovo Biswas
Minerals 2023, 13(10), 1289; https://doi.org/10.3390/min13101289 - 30 Sep 2023
Cited by 3 | Viewed by 1054
Abstract
The North Singhbhum Mobile Belt (NSMB) in the eastern Indian shield is an excellent example of a diverse lithological domain with multiphase shear/fracture zones. It is a well-acknowledged prospective region known for various mineralizations, e.g., Cu, Au, U, and Fe. The present study [...] Read more.
The North Singhbhum Mobile Belt (NSMB) in the eastern Indian shield is an excellent example of a diverse lithological domain with multiphase shear/fracture zones. It is a well-acknowledged prospective region known for various mineralizations, e.g., Cu, Au, U, and Fe. The present study was conducted in the Babaikundi–Birgaon Axis (a shear and fracture zone within NSMB) within Babaikundi village. The study suggests that anomalous zones are possibly related to gold-associated sulfide mineralization using photomicrography and geophysical methods such as magnetic, self-potential (SP), and very low-frequency (VLF) electromagnetic (EM) methods. Photomicrography on quartz samples and Scanning Electron Microscope (SEM) Backscattered-Electron (BSE) images show that gold particles are present in the quartz reef vein in Babaikundi. Magnetic data are presented in the total magnetic intensity (TMI), upward continuation, and analytical signal maps. VLF-EM data were analyzed using different processing techniques to delineate anomalous auriferous zones. Furthermore, the SP data were inverted using the Particle Swarm Optimization (PSO), Very Fast Simulated Annealing (VFSA), and Genetic Algorithm (GA) approaches for comparative study of the resultant model parameters and their suitability considering a 2D inverted resistivity section derived using VLF-EM. The photomicrography study indicates the existence of gold/ pyrite/pyrrhotite within the Babaikundi–Birgaon axis, which corresponds to a low magnetic anomaly based on a magnetic study; a high current density, a high Fraser value, and a low resistivity based on the VLF-EM study; and a negative SP value was found based on the SP study. The combined study generally supports mapping auriferous zones and demarcates the Babaikundi–Birgaon axis within the Babaikundi–Birgaon area. Full article
(This article belongs to the Special Issue Using Geophysical Inversion for Mineral Exploration: Methods and Applications)
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17 pages, 6087 KiB  
Article
Three-Dimensional Inversion of Multi-Component Semi-Airborne Electromagnetic Data in an Undulating Terrain for Mineral Exploration
by Zhiyuan Ke, Yunhe Liu, Yang Su, Luyuan Wang, Bo Zhang, Xiuyan Ren, Zhihao Rong and Xinpeng Ma
Minerals 2023, 13(2), 230; https://doi.org/10.3390/min13020230 - 5 Feb 2023
Cited by 4 | Viewed by 1290
Abstract
For the mineral exploration in complex terrain areas, the semi-airborne transient electromagnetic (SATEM) technology is one of the most powerful methods due to its high efficiency and low cost. However, since the mainstream SATEM systems only observe the component dBz/dt and the data [...] Read more.
For the mineral exploration in complex terrain areas, the semi-airborne transient electromagnetic (SATEM) technology is one of the most powerful methods due to its high efficiency and low cost. However, since the mainstream SATEM systems only observe the component dBz/dt and the data are usually processed by simple interpretation or one-dimensional (1D) inversion, their resolutions are too low to accurately decipher the fine underground structures. To overcome these problems, we proposed a novel 3D forward and inversion method for the multi-component SATEM system. We applied unstructured tetrahedron grids to finely discretize the model with complex terrain, subsequently we used the vector finite element method to calculate the SATEM responses and sensitivity information, and finally we used the quasi-Newton method to achieve high-resolution underground structures. Numerical experiments showed that the 3D inversion could accurately recover the location and resistivities of the underground anomalous bodies under the complex terrain. Compared to a single component data, the inversion of the multi-component data was more accurate in describing the vertical boundary of the electrical structures, and preferable for high-resolution imaging of underground minerals. Full article
(This article belongs to the Special Issue Using Geophysical Inversion for Mineral Exploration: Methods and Applications)
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19 pages, 6646 KiB  
Article
Interpreting Surface Large-Loop Time-Domain Electromagnetic Data for Deep Mineral Exploration Using 3D Forward Modeling and Inversion
by Ming Cheng, Dikun Yang and Qiang Luo
Minerals 2023, 13(1), 34; https://doi.org/10.3390/min13010034 - 26 Dec 2022
Cited by 5 | Viewed by 2133
Abstract
Surface transient electromagnetic (TEM) data with large transmitter loops for deep mineral exploration are often complicated by the non-trivial coupling between extended sources and arbitrarily oriented geological targets. This case study reports a TEM field data set acquired across terranes with strong lateral [...] Read more.
Surface transient electromagnetic (TEM) data with large transmitter loops for deep mineral exploration are often complicated by the non-trivial coupling between extended sources and arbitrarily oriented geological targets. This case study reports a TEM field data set acquired across terranes with strong lateral inhomogeneity, which is responsible for the high inconsistency in TEM data patterns along the survey line, as well as for the negative TEM transients (sign reversal) at some near-central loop stations. 3D forward modeling and inversion, as maturing tools in recent years, offer unique opportunities to extract as much geological information from such data as possible. 3D forward simulations of representative synthetic models found that the phenomenon of sign reversal at some TEM stations is associated with compact conductors enclosed by the transmitter loop and receivers that are in the loop, but off the conductor–a situation that is common in large-loop TEM and can only be explained by 3D models. However, 3D inversion of the field data with a uniform subspace as the initial and reference model fails to converge, another point of evidence that 3D inversions of large-loop TEM data are more likely to be subject to stability issues. Our solution is to warm-start the inversion with the representative model in the forward simulation experiments as the initial model, so the ill-posed 3D inversion can escape from local minima. Finally, the vertical contact structure in our 3D-inversion model is verified by a resistivity cross section of the CSAMT method. Our case study demonstrates the demand and capability of 3D electromagnetic modeling and inversion for high-resolution deep mineral exploration. It also provides an easy-to-follow template for carrying out 3D interpretation for complex geology in practice. Full article
(This article belongs to the Special Issue Using Geophysical Inversion for Mineral Exploration: Methods and Applications)
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12 pages, 5696 KiB  
Article
Subsurface Insights of the Maricunga Gold Belt through Local Earthquake Tomography
by Felipe Bugueño, Daniela Calle-Gardella, Diana Comte, Valentina Reyes-Wagner, Marcia Ojeda, Andreas Rietbrock and Steven Roecker
Minerals 2022, 12(11), 1437; https://doi.org/10.3390/min12111437 - 12 Nov 2022
Cited by 2 | Viewed by 1438
Abstract
With the advancement of the use of geophysical methods in mining exploration, the possibility of restudying known mineral deposits that could have greater potential than that previously estimated is opening up, as is the case in the Maricunga Belt (MB), which is a [...] Read more.
With the advancement of the use of geophysical methods in mining exploration, the possibility of restudying known mineral deposits that could have greater potential than that previously estimated is opening up, as is the case in the Maricunga Belt (MB), which is a metallogenic belt located east of Copiapó, Chile, with a length of 200 km and oriented in the NNE-SSW direction. This belt hosts significant gold deposits classified as porphyry gold (-copper), epithermal gold (-silver) of a high sulphidation type, and transitional gold, in some districts. In this work we studied the characteristics of the MB through local earthquake tomography (LET), which revealed a clear spatial correlation between low Vp/Vs anomalies and the gold deposits, demonstrating that lithologic interpretation using Vp and Vs values of the seismic tomography makes sense for the most common rocks associated with the genesis of porphyry-type deposits. Furthermore, high Vp/Vs anomalies were correlated to the main regional faults around the study zone, which seem to have a robust structural control regarding the location of the deposits. Full article
(This article belongs to the Special Issue Using Geophysical Inversion for Mineral Exploration: Methods and Applications)
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14 pages, 3418 KiB  
Article
Mineralization Based on CSAMT and SIP Sounding Data: A Case Study on the Hadamengou Gold Deposit in Inner Mongolia
by Hanqin Lv, Liuyang Xu, Biao Yang, Panyun Su, Haoqing Xu, Hailong Wang, Chuan Yao and Peng Su
Minerals 2022, 12(11), 1404; https://doi.org/10.3390/min12111404 - 3 Nov 2022
Cited by 2 | Viewed by 1565
Abstract
The Hadamengou deposit is the largest gold deposit in Inner Mongolia. However, given that the sources of ore-forming alkaline magmatic hydrothermal solutions and ore-controlling structures are still controversial, the theories behind the genesis of the deposit have been controversial. In this study, four [...] Read more.
The Hadamengou deposit is the largest gold deposit in Inner Mongolia. However, given that the sources of ore-forming alkaline magmatic hydrothermal solutions and ore-controlling structures are still controversial, the theories behind the genesis of the deposit have been controversial. In this study, four controlled-source audio magnetotellurics (CSAMT) and spectral induced polarization (SIP) profiles in the mining area were used to obtain the underground resistivity model and the pseudo section map of the apparent frequency dispersivity based on fine inversion. In the resistivity model, there are two high-resistivity blocks with resistivity greater than 3000 Ω m and three low-resistivity channels with resistivity less than 50 Ω m. Combined with the regional geological and drilling data, it is inferred that the high-resistance bodies, R4 and R5, may be alkaline magmatic intrusions related to multiple stages of magmatic hydrothermal activities, ranging from the Precambrian to Yanshanian periods. The highly conductive channels, C3, C5, and C4, may represent the Baotou-Hohhot fault, secondary faults, and ductile shear zone, respectively, which were formed in the Precambrian era and underwent multiple activations during the Hercynian to Yanshanian period. According to the spatial relationship, it is inferred that the ductile shear zone is an important ore-controlling and ore-hosting structure. However, the Baotou–Hohhot fault may be a pre-metallogenic fault rather than an ore-controlling fault. By comparing the resistivity model with the pseudo section of the apparent frequency dispersivity, it was found that all the known gold veins are located in the superimposed area of low resistivity and high-frequency dispersivity. It is speculated that the ductile shear zone outside the alkaline magmatic rock with the superimposed characteristics of low resistivity and high-frequency dispersivity is the favorable area for mineralization. Full article
(This article belongs to the Special Issue Using Geophysical Inversion for Mineral Exploration: Methods and Applications)
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