Computer modeling of electromagnetic data for mineral exploration: Application to uranium exploration in the Athabasca Basin

2021 ◽  
Vol 40 (2) ◽  
pp. 139a1-139a10
Author(s):  
Xushan Lu ◽  
Colin Farquharson ◽  
Jean-Marc Miehé ◽  
Grant Harrison ◽  
Patrick Ledru
Keyword(s):  
Computer Modeling ◽  
Unstructured Grids ◽  
Mineral Exploration ◽  
Real Data ◽  
Data Interpretation ◽  
Error Modeling ◽  
Accurate Data ◽  
Trial And Error ◽  
Athabasca Basin ◽  
Uranium Exploration

Electromagnetic (EM) methods are important geophysical tools for mineral exploration. Forward and inverse computer modeling are commonly used to interpret EM data. Real-life geology can be complex, and our computer modeling tools need to faithfully represent subsurface features to achieve accurate data interpretation. Traditional rectilinear meshes are less flexible and have difficulty conforming to the complex geometries of realistic geologic models, resulting in large numbers of mesh cells. In contrast, unstructured grids can represent complex geologic structures efficiently and accurately. However, building realistic geologic models and discretizing these models with unstructured grids suitable for EM modeling can be difficult and requires significant effort and specialized computer software tools. Therefore, it is important to develop workflows that can be used to facilitate model building and mesh generation. We have developed a procedure that can be used to build arbitrarily complex geologic models with topography using unstructured grids and a finite-volume time-domain code to calculate EM responses. We present an example of a trial-and-error modeling approach applied to a real data set collected at a uranium exploration project in the Athabasca Basin in Canada. The uranium mineralization is closely related to graphitic fault conductors in the basement. The deep burial depth and small thickness of the graphitic fault conductors demand accurate data interpretation results to guide subsequent drill testing. Our trial-and-error modeling approach builds initial realistic geologic models based on known geology and downhole data and creates initial geoelectrical models based on physical property measurements. Then, the initial model is iteratively refined based on the match between modeled and real data. We show that the modeling method can obtain 3D geoelectrical models that conform to known geology while achieving a good match between modeled and real data. The method can also provide guidance of where future drill holes should be directed.

Clustering and constrained inversion of seismic refraction and gravity data for overburden stripping: Application to uranium exploration in the Athabasca Basin, Canada

Geophysics ◽  
2020 ◽  
Vol 85 (4) ◽  
pp. B133-B146 ◽  
Author(s):  
Mehrdad Darijani ◽  
Colin G. Farquharson ◽  
Peter G. Lelièvre
Keyword(s):  
Gravity Data ◽  
Seismic Refraction ◽  
Real Data ◽  
Drill Hole ◽  
Gravity Inversion ◽  
Glacial Sediments ◽  
Athabasca Basin ◽  
Overburden Thickness ◽  
Uranium Exploration ◽  
Fuzzy C Means Clustering

Gravity signatures from features associated with the footprints of uranium deposits within the sandstones and basement of the Athabasca Basin are masked in the measured gravity by the contribution from glacial sediments (overburden), in particular by the variable thickness of the overburden. The 2D inversions of seismic refraction and gravity data are assessed as a means of reliably mapping overburden thickness, enabling the contribution to gravity from the overburden to be taken into account and density anomalies associated with deeper mineralization and alteration to be reconstructed through further inversion. Results show that independent inversion of seismic refraction data using the fuzzy c-means clustering method is able to determine the base of overburden well. Subsequent gravity inversion constrained by the overburden thickness reveals possible subtle density variations at depth, which could be associated with alteration in the sandstones associated with the uranium mineralization. Application of the seismic clustering inversion followed by constrained gravity inversion to both representative synthetic scenarios and real data from the Athabasca Basin, Canada, are considered. Drill-hole data show that the inversion results can predict the base of the overburden well, and there is an acceptable match between geologic information and possible alteration zones suggested by the inversions.

scholarly journals 2D dipping dike magnetic data interpretation using a robust particle swarm optimization

2017 ◽  
Author(s):  
Khalid S. Essa ◽  
Mahmoud El-Hussein
Keyword(s):  
Particle Swarm Optimization ◽  
Mineral Exploration ◽  
Random Noise ◽  
Particle Swarm ◽  
Real Data ◽  
Data Interpretation ◽  
Magnetic Data ◽  
Model Parameters ◽  
Swarm Optimization ◽  
Ore Bodies

Abstract. A robust Particle Swarm Optimization (PSO) investigation for magnetic data by a 2D dipping dike has been presented. The interpretive model parameters are: the amplitude coefficient (K), the depth to the top of the dipping dike (z), exact origin of the dipping dike (x0), and the width of dipping dike (w). The inversion procedure is actualized to gauge the parameters of a 2D dipping dike structures where it has been confirmed first on synthetic models without and with different level of random noise. The results of the inversion demonstrate that the parameters derived from the inversion concur well with the true ones. The root mean square (RMS) is figured by the strategy which is considered as the misfit between the measured and computed anomalies. The technique has been warily and effectively applied to real data examples from China and UK with the presence of ore bodies. The present technique can be applicable for mineral exploration and ore bodies of dike-like structure embedded in the shallow and deeper subsurface.

Paradigmatic Shifts in the Uranium Exploration Process: Knowledge Brokers and the Athabasca Basin Learning Curve

SEG Discovery ◽  
2011 ◽  
pp. 1-23
Author(s):  
James L. Marlatt ◽  
T. Kurt Kyser
Keyword(s):  
Research And Development ◽  
Technology Development ◽  
Current Model ◽  
Development Effort ◽  
Organizational System ◽  
Exploration Process ◽  
Athabasca Basin ◽  
Uranium Exploration ◽  
The Status ◽  
Knowledge Brokers

ABSTRACT Uranium exploration increased over the past decade in response to an increase in the price of uranium, with more than 900 companies engaged in the global exploration on over 3,000 projects. Major economic discoveries of new uranium orebodies have been elusive despite global exploration expenditures of $3.2 billion USD, with most of the effort in historical uranium districts. The increased effort in exploration with minimal return can be described through the example of a cyclical model based on exploration and discovery in the prolific Athabasca Basin, Saskatchewan. The model incorporates exploration expenditure, quantities of discovered uranium, and the sequence of uranium deposit discoveries to reveal that discovery cycles are epochal in nature and that they are also intimately related to the development and deployment of new exploration technologies. Exploration in the Athabasca Basin can be divided into an early “prospector” phase and the current “model-driven”phase. The future of successful uranium exploration is envisaged as the “innovation exploration” stage in which a paradigmatic shift in the exploration approach will take the industry towards new discoveries by leveraging research and technology development. Effective engagement within the “innovation exploration” paradigm requires that exploration organizations recognize knowledge brokers, and adopt research, development, and technology transfer as a long-term, systematic strategy, including critical definition of exploration targets, identification of innovation frontiers needed, enhanced leadership to accurately portray the research and development imperative and elevation of the status of the research and development effort within the organizational system.

Simultaneous source separation using a robust Radon transform

Geophysics ◽  
2014 ◽  
Vol 79 (1) ◽  
pp. V1-V11 ◽  
Author(s):  
Amr Ibrahim ◽  
Mauricio D. Sacchi
Keyword(s):  
Radon Transform ◽  
Real Data ◽  
Radon Transforms ◽  
Accurate Data ◽  
Quadratic Formula ◽  
Penalty Term ◽  
Source Data ◽  
The Cost ◽  
Simultaneous Source ◽  
Incoherent Noise

We adopted the robust Radon transform to eliminate erratic incoherent noise that arises in common receiver gathers when simultaneous source data are acquired. The proposed robust Radon transform was posed as an inverse problem using an [Formula: see text] misfit that is not sensitive to erratic noise. The latter permitted us to design Radon algorithms that are capable of eliminating incoherent noise in common receiver gathers. We also compared nonrobust and robust Radon transforms that are implemented via a quadratic ([Formula: see text]) or a sparse ([Formula: see text]) penalty term in the cost function. The results demonstrated the importance of incorporating a robust misfit functional in the Radon transform to cope with simultaneous source interferences. Synthetic and real data examples proved that the robust Radon transform produces more accurate data estimates than least-squares and sparse Radon transforms.

scholarly journals Teaching Real Data Interpretation with Models (TRIM): Analysis of Student Dialogue in a Large-Enrollment Cell and Developmental Biology Course

2016 ◽  
Vol 15 (2) ◽  
pp. ar17 ◽  
Author(s):  
Patricia Zagallo ◽  
Shanice Meddleton ◽  
Molly S. Bolger
Keyword(s):  
Cell Biology ◽  
Biological Significance ◽  
Real Data ◽  
Data Interpretation ◽  
Biological Data ◽  
Scientific Practices ◽  
Student Dialogue ◽  
Audio Recordings ◽  
A Cell ◽  
Large Enrollment

We present our design for a cell biology course to integrate content with scientific practices, specifically data interpretation and model-based reasoning. A 2-yr research project within this course allowed us to understand how students interpret authentic biological data in this setting. Through analysis of written work, we measured the extent to which students’ data interpretations were valid and/or generative. By analyzing small-group audio recordings during in-class activities, we demonstrated how students used instructor-provided models to build and refine data interpretations. Often, students used models to broaden the scope of data interpretations, tying conclusions to a biological significance. Coding analysis revealed several strategies and challenges that were common among students in this collaborative setting. Spontaneous argumentation was present in 82% of transcripts, suggesting that data interpretation using models may be a way to elicit this important disciplinary practice. Argumentation dialogue included frequent co-construction of claims backed by evidence from data. Other common strategies included collaborative decoding of data representations and noticing data patterns before making interpretive claims. Focusing on irrelevant data patterns was the most common challenge. Our findings provide evidence to support the feasibility of supporting students’ data-interpretation skills within a large lecture course.

3D VSP migration by image point transform

Geophysics ◽  
2010 ◽  
Vol 75 (3) ◽  
pp. S121-S130 ◽  
Author(s):  
Calin Cosma ◽  
Lucian Balu ◽  
Nicoleta Enescu
Keyword(s):  
Mineral Exploration ◽  
Real Data ◽  
Three Dimensions ◽  
Seismic Survey ◽  
Image Point ◽  
Inverse Transform ◽  
Time Distance ◽  
Diffraction Patterns ◽  
Original Time ◽  
Downhole Measurements

The common characteristic of the seismic methods involving downhole measurements is the difficulty of designing surveys able to image the subsurface space evenly. Migration schemes for these layouts are sensitive to reconstruction artifacts. The defining property of the image point (IP) transform is its ability to accumulate amplitudes of curved reflection events appearing in time-distance profiles into approximately discoidal (or spherical in three dimensions) vicinities in the IP domain. Due to the reflected wavefields collapsing into such vicinities in the IP domain, the emphasizing of the reflectors consists of enhancing regions with higher amounts of accumulated amplitude. True-dip filtering can also easily be performed, even for reflectors appearing in the time-distance profiles as curved events due to their dip, source offset or variable velocity field. Reflecting interfaces aredefined as sets of linked piecewise planar-reflector elements rather than as collections of point diffractors. True reflectors fitting this description are enhanced by the IP transform while diffraction patterns, events produced by other wave types, multiples, and noise of any kind, tend to be suppressed. The inverse transform leads to filtered versions of time-distance profiles. An alternative to performing the inverse transform back to the original time-distance representation is computing 2D/3D migrated images directly from the transformed IP space. Although the 3D migration by IP transform is applicable to any seismic survey geometry, we focused on procedures for enhancing prestack migrated images obtained by sparse multioffset, multiazimuth vertical seismic profiling (VSP) surveys as typically performed for mining site characterization and mineral exploration. The real data used were collected within an extensive mining seismic investigation program performed in Canada.

scholarly journals Recognising and dealing with complications in orthopaedic surgery

2017 ◽  
Vol 99 (3) ◽  
pp. 185-188 ◽  
Author(s):  
D Ricketts ◽  
RA Rogers ◽  
T Roper ◽  
X Ge
Keyword(s):  
Royal College ◽  
Orthopaedic Surgery ◽  
Data Interpretation ◽  
Accurate Data ◽  
Orthopaedic Surgeons

Orthopaedic surgeons need information about the complications they are likely to encounter. The literature on complications is difficult to interpret owing to a lack of agreed definitions, problems with collecting accurate data and with data interpretation. We suggest a role for the Royal College of Surgeons and specialist societies in collecting and interpreting complications data.

Application of modern 2-D and 3-D seismic-reflection techniques for uranium exploration in the Athabasca BasinThis article is one of a series of papers published in this Special Issue on the theme Lithoprobe — parameters, processes, and the evolution of a continent.

2010 ◽  
Vol 47 (5) ◽  
pp. 761-782 ◽  
Author(s):  
Z. Hajnal ◽  
D. J. White ◽  
E. Takacs ◽  
I. Gyorfi ◽  
I. R. Annesley ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Three Dimensional ◽  
Shear Zones ◽  
Mine Planning ◽  
Fracture Density ◽  
Athabasca Basin ◽  
Seismic Properties ◽  
Uranium Exploration ◽  
Exploration Drilling ◽  
Efficient Exploration

Seismic-reflection techniques have been applied in several studies over the last 20 years as a uranium-exploration tool within the Athabasca Basin and have been utilized to provide the larger structural context for known uranium deposits within the basin. At the crustal scale, deposits within the eastern Athabasca Basin are shown to be associated with deep-seated shear zones that originated during Trans-Hudson orogeny and have subsequently been reactivated during and subsequent to deposition of the basin-fill sandstones. Seismic properties of the Athabasca sandstones and underlying basement have been determined through in situ borehole measurements. Reflectivity within the sandstones is generally weak. Seismically recognizable signatures are primarily associated with variations in fracture density, porosity, and degree of silicification. The basement unconformity and regolith, a prime target of exploration, is widely imaged as it is characterized by variable but generally distinct reflectivity. Results from the McArthur River mine site suggest that the spatial coincidence of seismically imaged high-velocity zones and deep-seated faults that offset the unconformity may be a more broadly applicable exploration targeting tool. Three-dimensional (3-D) seismic imaging near existing ore zones can define the local structural controls on the mineralization and point the way to new targets, thus leading to more efficient exploration drilling programs. Furthermore, seismically generated structural maps of the unconformity and rock competence properties may play a significant role at the outset of mine planning.

scholarly journals Geological mapping and mineral exploration in the Motzfeldt Centre of the Igaliko nepheline syenite complex, South Greenland

1985 ◽  
Vol 125 ◽  
pp. 56-60
Author(s):  
T Tukiainen
Keyword(s):  
Ad Hoc ◽  
Raw Materials ◽  
Mineral Exploration ◽  
Weather Conditions ◽  
Field Work ◽  
Geological Mapping ◽  
Base Camp ◽  
Uranium Exploration ◽  
Geophysical Investigations ◽  
Bad Weather

The mineral occurrences of the Motzfeldt Centre, discovered by the South Greenland regional uranium exploration programme (Armour-Brown et al., 1984, Tukiainen et al., 1984), are now being explored for their Nb and Ta potential under a project financed by the EEC's Resources and Raw Materials Programme and The Geological Survey of Greenland. Accompanying the mineral exploration several other investigations are being carried out, and there is a dose co-operation between the various groups working in the area. The 1984 field activities comprised geological mapping, geochemical and geophysical investigations, and mineral exploration. The field activities were supported by GGU's facilities at Narssarssuaq where Jørgen Lau acted as base camp manager. A Jet Ranger helicopter, chartered on an ad hoc basis from the Ice Reconnaissance Centre at Narssarssuaq, was used for camp moves, geological reconnaissance and servicing of the field teams. Despite the bad weather conditions which prevailed for most of the season the main objectives of the field work were achieved.

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