Smith, Richard S.

Permanent URI for this collectionhttps://laurentian.scholaris.ca/handle/10219/3306

Richard Smith received a BSc and MSc from the University of Adelaide, Australia and an MSc and PhD from the University of Toronto. In 1989, he worked at Lamontagne Geophysics in Toronto (1989) where he helped develop methods for generating conductivity depth sections from airborne electromagnetic data. In 1990, Richard held an ARC post-doctoral fellowship at Macquarie University in Sydney (1990). From 1990 to 1992, Richard worked as an explorationist at Pasminco Exploration in Melbourne.

In 1993, Richard joined Geoterrex Ltd, an airborne geophysical survey company, later purchased by Fugro. Here he developed methods for processing and interpreting airborne magnetic and electromagnetic data. In May 2009, Richard took up an Industrial Research Chair in Exploration Geophysics at Laurentian University in Sudbury. Dr Smith is a member of the SEG (Chair, Mining and Geothermal committee, 2008-2010), the EAGE, KEGS, the ASEG (Federal Executive, 1992-1993), and the PDAC (conference organizing committee, 2008-2011). He is the recipient of a number of awards for the "best presentation" at conferences and is a co-recipient of the award for the best paper in the journal Geophysics for 1997 and the best paper in Exploration and Mining Geology (2012). In 2009/2010 he was the CSEG Distinguished Lecturer.

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Application of Occam’s inversion to airborne time-domain electromagnetics
(2009-03-01) Vallée, Marc A.; Smith, Richard S.
Airborne time-domain electromagnetics (ATDEM) methods are regularly used for mining, hydrocarbon, and groundwater exploration. A large quantity of data is collected along survey lines from an aircraft, and there is an incentive to interpret these data in a systematic way. When the geology is appropriate, the use of 1D inversion methods is justified. Among these methods are: conductivity-depth transform (CDT) (Wolfgram and Karlik, 1995), layered-earth inversion (Sattel, 1998), Zohdy's method (Sattel, 2005), and Occam's inversion (Constable et al., 1987; Sattel, 2005). These methods either require considerable tuning to get realistic results, are limited to step response data, or require considerable experimentation with the initial guess to ensure a reasonable result. The advantage of the Occam's algorithm is that it can be easily adapted to different ATDEM methods and is not strongly dependent on the initial guess. Furthermore, there are not a lot of parameters to tune in order to get a reasonable result. The weakness of the Occam's inversion is that for ATDEM data, the process requires a great deal of computer time. In this paper, we review details of the application of Occam's method to ATDEM data and we present the results of some of our experiments.
Airborne electromagnetic methods: applications to minerals, water and hydrocarbon exploration
(2010-03) Smith, Richard S.
Case history of combined airborne time-domain electromagnetics and power-line field survey in Chibougamau, Canada
(2010-03-01) Vallée, Marc A.; Smith, Richard S.; Keating, Pierre
Exploration for volcanogenic massive sulfides requires good geologic understanding. Geologic knowledge often is limited by a lack of outcrops. This is especially true in Canada under residual glacial covers. Geologic information must therefore be complemented by information obtained using means such as geophysical and geochemical observations. Electromagnetic (EM) methods extend lithological understanding to depths beyond the overburden. Massive sulfides are highly conductive and, depending on their depth and volume, may be detected easily by airborne EM surveys. They are more often equant than graphitic sediments, which typically have longer strike length. Current EMtechniques that identify massive sulfides operate in the frequency or time domain, the latter being more common. Additional information can be provided by using power-line fields as a source of EM signals when the powerlines are appropriately located in the area of interest. We have worked in an active exploration area near Chibougamau, Canada, known for a large occurrence of massive sulfide deposits. The geology is a sequence of volcanic formations with felsic and mafic intrusions. Our magnetic technique responded well to mafic rocks. An airborne time-domain EM survey mapped localized and intrasedimentary conductors in that area. We learned in our study that power-line EM fields can be used to map large-extent conductive formations and narrow geologic faults.
Metalliferous mining geophysics — State of the art after a decade in the new millennium
(2011-06-03) Vallée, Marc A.; Smith, Richard S.; Keating, Pierre
Mining exploration was very active during the first decade of the twenty-first century because there were numerous advances in the science and technology that geophysicists were using for mineral exploration. Development came from different sources: instrumentation improvements, new numerical algorithms, and cross-fertilization with the seismic industry. In gravity, gradiometry kept its promise and is on the cusp of becoming a key technology for mining exploration. In potential-field methods in general, numerous techniques have been developed for automatic interpretation, and 3D inversion schemes came into frequent use. These inversions will have even greater use when geologic constraints can be applied easily. In airborne electromagnetic (EM) methods, the development of time-domain helicopter EM systems changed the industry. In parallel, improvements in EM modeling and interpretation occurred; in particular, the strengths and weaknesses of the various algorithms became better understood. Simpler imaging schemes came into standard use, whereas layered inversion seldom is used in the mining industry today. Improvements in ground EM methods were associated with the development of SQUID technology and distributed-acquisition systems; the latter also impacted ground induced-polarization (IP) methods. Developments in borehole geophysics for mining and exploration were numerous. Borehole logging to measure physical properties received significant interest. Perhaps one reason for that interest was the desire to develop links between geophysical and geologic results, which also is a topic of great importance to mining geologists and geophysicists.
A grid implementation of the SLUTH algorithm for visualizing the depth and structural index of magnetic sources
(2012-01-01) Smith, Richard S.; Thurston, Jeffrey B.; Salem, Ahmed; Reid, Alan B.
The SLUTH method requires first-order derivatives at two or more different heights above the ground and can estimate the location and depth of source bodies from magnetic data. Results of this method are independent of a specific model type and can be used to estimate the most appropriate model (structural index). This paper presents a grid implementation of the SLUTH method to visualize both depth and structural index from magnetic anomaly data. The implementation uses the Geosoft GX programming language. The method has been tested using theoretical magnetic gridded data and of two methods have been used for estimating depth; the estimate from the width of the imaged feature gives an underestimate and the estimate from the rate of fall off of the field with height gives an overestimate. The practical utility of the algorithm is demonstrated using field data from the Saskatoon area of Canada.
How to make better use of physical properties in mineral exploration: The exploration site measurement
(2012-03-01) Smith, Richard S.; Shore, Mark; Rainsford, Desmond
In recent years, there has been a growing awareness that a better understanding of physical property information is required in mineral exploration. As a consequence, there has been a strong push to collect more data and to use these data more intelligently. There are a multiplicity of reasons behind this impetus: geophysicists want more information about physical property data to enable better surveys to be planned and better interpretations to come from the data acquired and geologists want physical properties to provide addition information about the geology that might allow them to see variations in rocks that are not easy to see using traditional or more expensive methods (hand specimen examination, thin sections, lithogeochemistry, assays, etc.). If a hole is drilled on a geophysical target, then a physical property measurement of the core or the rocks surrounding the core can confirm if the target was intercepted and provides data that can be used to model the target response.
Using combinations of spatial gradients to improve the detectability of buried conductors below or within conductive material
(2012-12-12) Smith, Richard S.
The detection of conductive bodies is an important capability when exploring for massive sulfide deposits or looking for unexploded ordnance. When these bodies are buried below conductive overburden or embedded in conductive material, the use of an electromagnetic system to identify the bodies becomes problematic because the response of the overlying conductive material can be much greater that the response of the buried conductor. I calculated the response of five models representing different conductivity distributions (a buried conductor, a uniform overburden with changes in the system altitude, a paleochannel, a thicker overburden, and a thinner overburden). The subtle response of the buried conductor was difficult to identify because it looked very similar to the responses of other structures that are not necessarily of interest. The spatial gradients for the same five models showed that the greatest improvement in the relative size of the anomalous gradient response compared with the background gradient came for the cases in which the material closest to the surface changes, in particular the paleochannel and thickening overburden models. However, identification of the deeper buried conductor was still problematic because of the large background gradients. In theory, the cylindrical symmetry of a dipole transmitter over a layered earth ensured that there were exact relations between the spatial derivatives. Hence it was possible to define two specific combinations that should be zero over a layered earth. Calculating these combinations for the five models showed that the anomalous zones stood out with significantly greater anomaly-to-background ratios. The measurement of the gradients and the calculation of these combinations therefore provided a means of identifying anomalous zones in and below a conductive earth. Different relative sizes and shapes of the two combinations for different models provided a way of discriminating between the vertical conductor model and the four other models.
Qualitative geophysical interpretation of the Sudbury Structure
(2013-07-26) Smith, Richard S.; Olaniyan, Oladele; Morris, Bill
The Sudbury Structure is one of the most studied geologic structures in the world due to its enigmatic nature and mineral wealth. The available geologic work from the literature and mining industry operations accumulated for more than a century was recently assessed and compiled into a bedrock geologic map. Most regional geophysical investigations of the Sudbury Structure have been quantitative — modeling and depth estimation without a clear definition of surface control. Airborne total magnetic intensity data over the Sudbury Structure were compiled, processed, and interpreted, to define magnetic stratigraphy boundaries and near-surface lineaments. Traditional directional and normalized derivatives were computed to enhance the high-frequency information in the magnetic field. Available airborne frequency-domain electromagnetic (EM) data were also interactively interpreted along profiles and in a gridded format to isolate conductive structures. On-screen geographic information system-based information extraction from multiple derivatives was used to interpret the magnetic contacts, dykes, and lineaments. The magnetic interpretation was compared with published bedrock maps of the Sudbury Structure. Magnetic contacts based on the qualitative classification of the magnetic texture did not always correspond to the geologic boundaries on the existing maps. Some magnetic lineaments corresponded with well-defined geologic structures, some were further extensions of partially mapped structures, and others are newly identified linear structures. Conductive locations identified from the EM profiles were probably due to responses from conductive ore bodies, faults, dykes, lithological contacts, and cultural objects.
Mapping lateral changes in conductance of a thin sheet using time-domain inductive electromagnetic data
(Society of Exploration Geophysicists, 2013-11-05) Kolaj, M.; Smith, Richard S.
With the inductive electromagnetic geophysical method, the laterally varying conductance of thin sheet models can be estimated either through a direct transform of the measured data or through inversion. The direct transform (called the simplified solution) does not require grid or line data and is simple enough to be performed in the field because the conductance at a location is calculated directly from the ratio of two measured magnetic fields (the vertical spatial and temporal derivative of the vertical magnetic field) at that location. However, the simplified solution assumes that the secondary horizontal magnetic fields are zero and/or that the sheet has a uniform conductance. Our nonapproximate solution (called the full inversion) does not make these assumptions, but requires gridded data, measurements of the secondary horizontal magnetic fields, and more complicated inversion algorithms. Through forward modeling, we found that the full inversion provides better results than the simplified solution when the spatial gradient of the resistance is strong and/or when the horizontal magnetic fields are large. Because the simplified solution may be preferable due to its simplicity, we introduce two unreliability parameters, which assess the unreliability of the conductance calculated using the simplified solution. A comparison of the simplified solution and full inversion in a fixed in-loop survey collected overtop a dry tailings pond in Sudbury, Ontario, Canada, revealed that there were small differences around large conductance contrasts, which coincided with elevated unreliability parameters. The simplified solution is recommended if fast in-field interpretations are required, or additionally, as a first-pass survey that can be performed with sparse station spacing to identify areas of interest. Denser grid data can then be collected, for the more reliable full inversion, over areas of interest and/or zones where the simplified solution is expected to be unreliable as predicted by the unreliability parameters.
Robust conductance estimates from spatial and temporal derivatives of borehole electromagnetic data
(Society of Exploration Geophysicists, 2014-05-01) Kolaj, M.; Smith, Richard S.
The conductance of an infinite uniformly conductive thin sheet can be calculated using the ratio of the temporal gradient and the spatial gradient in the normal direction of any component (or combination of components) of the secondary magnetic field. With standard borehole electromagnetic (BHEM) systems, the temporal gradient can either be measured or readily calculated from transient-magnetic-field data, and the spatial gradient in the normal direction can be estimated using adjacent stations. Synthetic modeling demonstrates that, for a finite thin sheet, the magnitude of the field provides a robust and reliable apparent conductance in typical three-component BHEM survey configurations. The accuracy in which the apparent conductance can be calculated is hindered by low spatial gradient signal values and can only be reliably estimated where the fields are large (i.e., in close proximity to the target). In a field example of BHEM data collected over a massive sulfide deposit in Sudbury, Ontario, Canada, the spatial gradient could be calculated over a roughly 100-m-wide zone, and a consistent apparent conductance could be calculated at each delay time using the magnitude of the field. Increases in the apparent conductance with increasing delay time are likely due to currents migrating into more conductive parts of the body. The apparent conductance values were also consistent with Maxwell models and time constant derived conductance estimates. This simple and robust apparent conductance is ideal as a first-pass estimate for target discrimination, grade estimation, and starting values for forward and/or inversion modeling.
A procedure for collecting electromagnetic data using multiple transmitters and receivers capable of deep and focussed exploration
(Society of Exploration Geophysicists, 2014-11-26) Lymburner, J.; Smith, Richard S.
Many ground controlled-source electromagnetic (EM) systems have been deployed, and under ideal conditions these systems are capable of detecting large conductors to depths of approximately 800 m; however, more common detection limits are less than 400 m. Although these systems have been used with great success, they may experience two weaknesses when exploring for deeper conductors: poor coupling with the target and small signal-to-noise ratios (S/Ns), both of which decrease the quality and interpretability of the data. We evaluated a novel time-domain EM procedure that addresses these weaknesses. The coupling weakness was addressed through multiple transmitter locations and multiple receiver locations, and the S/N was increased by spatial stacking of measurements (from the various transmitter-receiver combinations). A field test of this procedure was undertaken. Reciprocity data indicated that the noise levels of the vertical component data we acquired were about −0.004μV/Am2. Spatial stacking of the data can reduce the noise levels by a factor of seven. This means that a small conductor previously only visible to 150 m could be seen to 275 m and a conductor visible to 300 m could be seen to 575 m. One challenge of the new procedure was the time required to collect all the transmitter-receiver combinations — this time can be reduced using the principle of reciprocity and not repeating approximately reciprocal measurements. Another challenge was to visualize and interpret the large volumes of data collected using the procedure — this has been partially addressed by creating equivalent-dipole depth sections. Synthetic and real equivalent-dipole depth sections appeared very similar and illustrated that these images of the subsurface could be interpreted. However, the features appeared too deep on the sections, so better visualization techniques could be developed.
Regional 3D geophysical investigation of the Sudbury Structure
(Society of Exploration Geophysicists and American Association of Petroleum Geologists, 2015-04-22) Olaniyan, O.; Smith, Richard S.; Lafrance, B.
The 3D geologic and structural setting of the Sudbury Structure was predicted by an integration of surface and subsurface geologic data with 2.5D modeling of high-resolution airborne magnetic and gravity data using 3D GeoModeller software. Unlike other CAD-based 3D software, GeoModeller uses the field interpolator method, whereby contacts of rock units are assumed to be equipotential surfaces, whereas orientation data determine the gradient and direction of the surfaces. Contacts and orientation variables are cokriged to generate 3D continuous surfaces for each geologic unit. Our 3D geologic model was qualitatively evaluated by forward computing the predicted gravity response at 1 m above topography and by comparing this response to the measured gravity field. Large-scale structures within the Onaping Formation and Archean basement, which overlie and underlie the Sudbury Igneous Complex (SIC), respectively, were not the cause of the linear gravity high in the center of the Sudbury Structure. We suggested that the deformation of the initial circular SIC may have commenced under the Sudbury Basin due to the reversal of the normal faults related to the Huronian rift system during the Penokean orogeny, therefore resulting into a north verging fold at the base of the SIC in the south range. This new interpretation was consistent with the magnetic and gravity data and honoured most of the significant seismic reflectors in the Lithoprobe seismic sections.
Introduction to special section: Mining and minerals exploration interpretation
(Society of Exploration Geophysicists, American Association of Petroleum Geologists, 2015-04-22) Lo, B.; Li, Y.; Smith, Richard S.; Arce, J.; Shore, M.
Mineral deposits are found in a variety of geologic settings and ore-forming minerals can have a vast range of physical properties. The search for these deposits is also relatively near-surface thus far. These factors allow for a large number of possible airborne and ground-based techniques to be used in geophysical exploration. Deciding on the proper geophysical technique and survey layout requires an understanding of the target, its associated alteration, the variations in physical properties and the geologic and structural setting. Knowing the exploration history is important, particularly in exploration programs that are more mature. Interpretation of the data requires the integration of the myriad of information ranging from physical property models constructed from inversions or forward modeling, physical property data, geochemical data, mineral deposit model, and host geology. We envisioned a special section on mining geophysics to highlight the integrative nature of mining geophysics through a collection of papers using multiple geophysical data to provide geology and exploration rationale along with the interpretations. So in collaboration with the editor of Interpretation, we issued a call for papers that discussed geophysics as applied to mining, discussed all relevant geophysical data and provided geologic information and the exploration rationale along with the interpretations. The following papers provide insight into the importance of geophysics in mineral exploration from the belt or camp scale to exploration focused on a specific orebody. Wright and Koehler combine controlled-source audio magnetotelluric and gravity data in a previously explored terrain of the Carlin trend. The authors demonstrate that successive geophysical surveys, combined with geologic understanding and target model development were key to a significant gold discovery. Martinez and Li demonstrate that lithological interpretation techniques based on inversion of airborne gravity gradiometry and aeromagnetic data can be used to characterize an iron-ore formation in Minas Gerais. The authors show that lithology differentiation using either generic physical property constraints or geologic constraints can contribute to a geologic understanding at the deposit scale. Olaniyan et al. study the 3D geologic and structural setting of the Sudbury structure using an integration of geologic data with airborne gravity and magnetic data. Using standard 2.5D modeling and 3D Geomodeller software, they generate continuous surfaces in three dimensions for each geologic interface, which leads them to suggest a possible deformation history of the Sudbury structure. Woolrych et al. present data from a range of airborne and ground-based geophysical techniques that have contributed to the discovery of the Kitumba iron oxide copper gold (IOCG) deposit in central Zambia. The interpretation of geophysical data following an exploration criteria of an IOCG-type deposit model has opened up exploration for this style of deposit in Central Zambia. Lü et al. present a case study that demonstrates the use of integrating seismic, magnetotelluric, gravity, and magnetic data to interpret the 3D structure and deformation at depth in the Lu-Zong ore district of Eastern China. Insights were obtained into the fault systems and crustal architecture that are essential for understanding the Lu-Zong ore district mineral system and for mineral exploration at depth. Legault et al. present the results of three different airborne electromagnetic (EM) surveys over the Lalor copper-zinc-gold volcanogenic massive sulfide deposit, which is more than 500 m deep and is in the Flin Flon Greenstone Belt of north-central Manitoba. The active and passive source EM surveys span a five year period, which means that the development of EM systems over this period can be assessed.
Combining spatial components and Hilbert transforms to interpret ground-time-domain-electromagnetic data
(Society of Exploration Geophysicists, 2015-06-19) Desmarais, J.K.; Smith, Richard S.
We have developed a method for displaying or imaging data from a ground-time-domain electromagnetic system and for extracting the geometric parameters of a small conductor. The parameters are determined directly from the data using combinations of the spatial components of the secondary fields and their Hilbert transforms. The position of the target coincides with the peaks of the energy envelope (EE) or the 𝑇-component of the response. Here, the EE is the square root of the sum of the squares of the three spatial components and their Hilbert transforms, whereas the 𝑇-component response is an analogous quantity that excludes the Hilbert transform terms. Studies on synthetic models indicate that the 𝑇-component response is sharper than the EE in most possible target orientations. Once the position of a body has been determined using the peak of the 𝑇-component response, the dip of the target can be quantified using the ratio of the full-width at half-magnitude (FWHM) of the 𝑇-component response and the 𝑇-component Hilbert transform response, which is analogous to the EE but excludes the untransformed quantities. Finally, once all other geometric parameters have been determined, the depth of the target can be evaluated using the FWHM of the 𝑇-component response. The proposed modeling method was tested over an anomaly acquired at the Coulon field site during an InfiniTEM survey in the Abitibi greenstone belt of Quebec. The extracted geometric parameters were consistent with the available geologic information.
A multiple transmitter and receiver electromagnetic system for improved target detection
(Society of Exploration Geophysicists, 2015-06-22) Kolaj, M.; Smith, Richard S.
We have developed an alternative strategy for the inevitable deeper inductive electromagnetic (EM) exploration, which will be required as shallow deposits are exhausted. Rather than using very large magnetic moment ground loops, measurement stations are repeated using many smaller sized loops with smaller moments. The multiple transmitter data are then weighted and summed into a single high signal-to-noise ratio (S/N) composite transmitter. The composite transmitter can be thought of as a postprocessing method that uses the collected multitransmitter data to construct/simulate a transmitter, which maximizes the coupling to a particular target. The appropriate transmitter weights to use will depend on the target location and geometry, and, as such, different weighting schemes allow for the construction of different composite transmitters, each of which will maximally highlight different targets. We have assumed no prior knowledge of the location and orientation of the exploration targets, and we constructed composite transmitters for each possible location of a discretized subsurface and 324 possible target orientations (dipole embedded within a fully resistive medium). A modified difference of squares and a dipole look-up table was used to assess the fit between each composite transmitter and the suggested target location and orientation. Synthetic studies using conductive plate target(s) embedded within a fully resistive medium found that the target locations and orientations could be accurately determined and that the S/N of the composite transmitter was significantly higher than that of standard fixed-loop ground and airborne surveys. In a ground time-domain EM field test, 23 transmitter positions were used, and a shallow target (conductive dike) could be identified using the developed methodology. The composite transmitter data we produced was considerably easier to interpret and had a larger amplitude than that of any one single transmitter.
The effect of dielectric permittivity on the fields radiated from a radio-frequency electric dipole in a homogeneous whole space
(Society of Exploration Geophysicists, 2016-02-18) Naprstek, T.; Smith, Richard S.
The radio imaging method (RIM) is an electromagnetic cross-borehole method with applications in mineral exploration, as well as in the coal industry, where it is used across mine drives. Attenuation of the signal from conductive regions may indicate areas of mineralization, and these conductive effects in general dominate the response. In an effort to better understand the effect of a material’s dielectric permittivity on the response of the RIM, we have developed a simple program to model an electric dipole in a homogeneous whole space. When increasing the dielectric permittivity, the amplitude peak broadened and increased, whereas the phase peak sharpened and shifted negatively. To showcase the effect of dielectric permittivity on RIM data, data recorded from two transmitter positions in a moderately homogeneous zone in the Sudbury Basin were curve fit, and we concluded that despite the stronger effect that conductivity has on the signal, RIM is still sensitive to dielectric permittivity, and appropriate values must be used when developing conductivity tomograms. In addition, we found that for the given situation and frequencies used, an increase in either the conductivity or dielectric permittivity could be accounted for by a decrease of approximately the same factor in the other variable. However, the low-conductivity, high-permittivity case seemed to fit the shape of the amplitude and phase curves better. For the sulfide impregnated crystalline rocks at our field site, relative dielectric constants of 26.4 and 31 at 1250 and 625 kHz, respectively, were inferred.
Approximate semianalytical solutions for the electromagnetic response of a dipping-sphere interacting with conductive overburden
(Society of Exploration Geophysicists, 2016-06-06) Desmarais, J.K.; Smith, Richard S.
Electromagnetic exploration methods have important applications for geologic mapping and mineral exploration in igneous and metamorphic terranes. In such cases, the earth is often largely resistive and the most important interaction is between a conductor of interest and a shallow, thin, horizontal sheet representing glacial tills and clays or the conductive weathering products of the basement rocks (both of which are here termed the “conductive overburden”). To this end, we have developed a theory from which the step and impulse responses of a sphere interacting with conductive overburden can be quickly and efficiently approximated. The sphere model can also be extended to restrict the currents to flow in a specific orientation (termed the dipping-sphere model). The resulting expressions are called semianalytical because all relevant relations are developed analytically, with the exception of the time-convolution integrals. The overburden is assumed to not be touching the sphere, so there is no galvanic interactions between the bodies. We make use of the dipole sphere in a uniform field and thin sheet approximations; however, expressions could be obtained for a sphere in a dipolar (or nondipolar) field using a similar methodology. We have found that there is no term related to the first zero of the relevant Bessel function in the response of the sphere alone. However, there are terms for all other zeros. A test on a synthetic model shows that the combined sphere-overburden response can be reasonably approximated using the first-order perturbation of the overburden field. Minor discrepancies between the approximate and more elaborate numerical responses are believed to be the result of numerical errors. This means that in practice, the proposed approach consists of evaluating one convolution integral over a sum of exponentials multiplied by a polynomial function. This results in an extremely simple algorithmic implementation that is simple to program and easy to run. The proposed approach also provides a simple method that can be used to validate more complex algorithms. A test on field data obtained at the Reid Mahaffy site in Northern Ontario shows that our approximate method is useful for interpreting electromagnetic data even when the background is thick. We use our approach to obtain a better estimate of the geometry and physical properties of the conductor and evaluate the conductance of the overburden.
A comparison of magnetic susceptibility meters using samples from the Thompson Nickel Belt, Canada
(2016-10) Deng, Deng N.; Smith, Richard S.
Exploring for copper–gold deposits exhibiting a wide range of conductivities with time–domain electromagnetics at Opemiska, Canada
(2017) Gaucher, Frédéric E. S.; Smith, Richard S.
Finding and delineating new economic Cu-Au ore zones corresponding to poorly conductive disseminated mineralization and narrow massive chalcopyrite veins in the Chapais-Chibougamau mining district of Québec is a challenging exploration problem. The site of the former Opemiska underground mine was the location for conducting an experimental ground time-domain electromagnetics (EM) survey for mapping the conductivity, the anisotropy of the conductivity, and the chargeability estimated from shape reversals. Measurements at fourteen different sites confirmed the variability of the EM response. The trends, sizes, shapes and conductances of the relatively strong conductors were identified with success and modelled using thin plates in full space. The vein direction in the weakly conductive zones was quantified from the x-component data. Petrophysical measurements and microscopic observations suggest complex interrelations between the amount of ore, the fabric of the rock, texture, mineralogical associations and impurities. This explains a wide range of bulk conductivity values ~0.01 S/m to 4000 S/m measured on rock samples and also suggests that chalcopyrite might be a semiconductor at some locations at Opemiska.
Integrated Multi-Parameter Exploration Footprints of the Canadian Malartic Disseminated Au, McArthur River-Millennium Unconformity U, and Highland Valley Porphyry Cu Deposits: Preliminary Results from the NSERC-CMIC Mineral Exploration Footprints Research Network
(2017) Lesher, M.; Hannington, M.; Galley, A.; Ansdell, K.; Astic, T.; Banerjee, N.; Beauchamp, S.; Beaudoin, G.; Bertelli, M.; Bérubé, C.; Beyer, S.; Blacklock, N.; Byrne, K.; Cheng, L.-Z.; Chouinard, R.; Chouteau, M.; Clark, J.; D'Angelo, M.; Darijani, M.; Devine, M.; Dupuis, C.; El Goumi, N.; Farquharson, C.; Enkin, R.; Fayol, N.; Feltrin, L.; Feng, J.; Gaillard, N.; Gleeson, S.; Gouiza, M.; Grenon, C.; Guffey, S.; Guilmette, C.; Guo, K.; Hart, C.; Hattori, K.; Hollings, P.; Joyce, N.; Kamal, D.; King, J.; Kyser, K.; Layton-Matthews, D.; Lee, R.; Lesage, G.; Leybourne, M.; Linnen, R.; Lypaczewski, P.; McGaughey, J.; Mitchinson, D.; Milkereit, B.; Mir, R.; Morris, W.; Oldenburg, D.; Olivo, G.; Perrouty, S.; Piercey, S.; Piette-Lauzière, N.; Raskevicius, T.; Reman, A.; Rivard, B.; Ross, M.; Samson, I.; Scott, S.; Shamsipour, P.; Shi, D.; Smith, Richard S.; Sundaralingam, N.; Taves, R.; Taylor, C.; Valentino, M.; Vallée, M.; Wasyliuk, K.; Williams-Jones, A.; Winterburn, P.
Mineral exploration in Canada is increasingly focused on concealed and deeply buried targets, requiring more effective tools to detect large-scale ore-forming systems and to vector from their most distal margins to their high grade cores. A new generation of ore system models is required to achieve this. The Mineral Exploration Footprints Research Network is a consortium of 70 faculty, research associates, and students from 20 Canadian universities working with 30 mining, mineral exploration, and mining service providers to develop new approaches to ore system modelling based on more effective integration and visualization of multi-parameter geological-structural-mineralogical-lithogeochemical-petrophysical-geophysical exploration data. The Network is developing the next generation ore system models and exploration strategies at three sites based on integrated data visualization using self-consistent 3D Common Earth Models and geostatistical/machine learning technologies. Thus far over 60 footprint components and vectors have been identified at the Canadian Malartic stockwork-disseminated Au deposit, 20–30 at the McArthur-Millennium unconformity U deposits, and over 20 in the Highland Valley porphyry Cu system. For the first time, these are being assembled into comprehensive models that will serve as landmark case studies for data integration and analysis in the today’s challenging exploration environment.

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