Relationship between rock physical properties and spectral mineralogy applied to exploration for an unconformity-related uranium deposit (Saskatchewan, Canada)

Infrared (IR) spectroscopy has been used to characterize clay and clay-sized minerals present in drill cores that are associated with unconformity-related uranium deposits. Physical properties have been measured on samples to gain empirical data about the rock types and associated relationships with geophysical survey data. These data can be used to build three-dimensional geological models and constrain geophysical inversions. The objective of this study is to verify whether a relationship exists between rock physical properties and IR spectral mineralogy. Physical properties were measured on 427 core samples collected from the Martin Lake project, which is located in the southeastern Athabasca Basin (Saskatchewan, Canada). Results indicate that resistivity, density, and porosity are correlated to each other, especially within basement units. A comparison of their distribution with the IR spectral mineralogy demonstrates a relationship for each altered and unaltered samples. The samples with low resistivity and density, and high porosity are characterized by the presence of a di-trioctahedral (Al–Mg) chlorite (sudoite) due to the hydrothermal alteration processes. The unaltered samples with higher resistivity and density, and low porosity contain a tri-octahedral (Fe–Mg) chlorite as a result of metamorphic processes. Eleven mineralogical classes can be established based on IR spectroscopy. A percentile-based approach has been proposed and tested to define physical property ranges for each of the classes to predict resistivity and density values downhole.

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Joint inversion of potential-fields data over the DO-27 kimberlite pipe using a Gaussian mixture model prior

Interpretation ◽

10.1190/int-2019-0283.1 ◽

2020 ◽

Vol 8 (4) ◽

pp. SS47-SS62

Author(s):

Thibaut Astic ◽

Dominique Fournier ◽

Douglas W. Oldenburg

Keyword(s):

Gaussian Mixture Model ◽

Mixture Model ◽

Joint Inversion ◽

Gravity Data ◽

Physical Property ◽

Gaussian Mixture ◽

Kimberlite Pipe ◽

Magnetic Data ◽

High Porosity ◽

Rock Types

We have carried out petrophysically and geologically guided inversions (PGIs) to jointly invert airborne and ground-based gravity data and airborne magnetic data to recover a quasi-geology model of the DO-27 kimberlite pipe in the Tli Kwi Cho (also referred to as TKC) cluster. DO-27 is composed of three main kimberlite rock types in contact with each other and embedded in a granitic host rock covered by a thin layer of glacial till. The pyroclastic kimberlite (PK), which is diamondiferous, and the volcanoclastic kimberlite (VK) have anomalously low density, due to their high porosity, and weak magnetic susceptibility. They are indistinguishable from each other based upon their potential-field responses. The hypabyssal kimberlite (HK), which is not diamondiferous, has been identified as highly magnetic and remanent. Quantitative petrophysical signatures for each rock unit are obtained from sample measurements, such as the increasing density of the PK/VK unit with depth and the remanent magnetization of the HK unit, and are represented as a Gaussian mixture model (GMM). This GMM guides the PGI toward generating a 3D quasi-geology model with physical properties that satisfies the geophysical data sets and the petrophysical signatures. Density and magnetization models recovered individually yield volumes that have physical property combinations that do not conform to any known petrophysical characteristics of the rocks in the area. A multiphysics PGI addresses this problem by using the GMM as a coupling term, but it puts a volume of the PK/VK unit at a location that is incompatible with geologic information from drillholes. To conform to that geologic knowledge, a fourth unit is introduced, PK-minor, which is petrophysically and geographically distinct from the main PK/VK unit. This inversion produces a quasi-geology model that presents good structural locations of the diamondiferous PK unit and can be used to provide a resource estimate or decide the locations of future drillholes.

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The Preliminary Results of Rock Physical Properties in Yudu-Ganxian Ore Concentration Area

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.813.225 ◽

2013 ◽

Vol 813 ◽

pp. 225-229

Author(s):

Bin Zhao ◽

Jian Guo Li ◽

Shao Wei Sun ◽

Xin Peng Zhou ◽

Zhen Bin Wang ◽

...

Keyword(s):

Physical Properties ◽

Research Method ◽

Three Dimensional ◽

Physical Property ◽

Physical Parameters ◽

Distribution Characteristics ◽

Actual Distribution ◽

New Information ◽

Metallogenic Prognosis ◽

Rock Physical Property

As the lack of work on comprehensive rock physical properties in deep geophysical exploration in Yudu-Ganxian ore concentration area, this paper focuses in comprehensive and systematic study about the comprehensive rock physical properties in this area. Known from the rock (ore) actual distribution in this area, this paper presents the comprehensive rock physical properties research method of the area, which use varieties of techniques to collect specimens systematic, determine the physical parameters, and even study the distribution characteristics and variation law of rock (ore) integrated rock physical properties parameters. In this paper, the results can provide the new information about integrated rock physical property parameters for understanding and explaining the integrated geophysical anomaly, providing the basis for the future in Nanling to carry out deep geophysical three-dimensional exploration and deep metallogenic prognosis.

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Three-dimensional gravity modelling applied to the exploration of uranium unconformity-related basement-hosted deposits: the Contact prospect case study, Kiggavik, northeast Thelon region (Nunavut, Canada)

Canadian Journal of Earth Sciences ◽

10.1139/cjes-2016-0225 ◽

2017 ◽

Vol 54 (8) ◽

pp. 869-882 ◽

Cited By ~ 5

Author(s):

Régis Roy ◽

Antonio Benedicto ◽

Alexis Grare ◽

Mickaël Béhaegel ◽

Yoann Richard ◽

...

Keyword(s):

Gravity Data ◽

Three Dimensional ◽

Gravity Anomalies ◽

3D Models ◽

Low Density ◽

Uranium Deposits ◽

Geological Interpretation ◽

Thelon Basin ◽

Dimensional Gravity ◽

Density Values

In unconformity-related uranium deposits, mineralization is associated with hydrothermal clay-rich alteration haloes that decrease the density of the host rock. In the Kiggavik uranium project, located in the eastern Thelon Basin, Nunavut (Canada), basement-hosted shallow deposits were discovered by drilling geophysical anomalies in the 1970s. In 2014, gravity data were inverted for the first time using the Geosoft VOXI Earth ModellingTM system to generate three-dimensional (3D) models to assist exploration in the Contact prospect, the most recent discovery at Kiggavik. A 3D unconstrained inversion model was calculated before drilling, and a model constrained by petrophysical data was computed after drilling. The unconstrained inversion provided a first approximation of the geometry and depth of a low-density body and helped to collar the discovery holes of the Contact mineralization. The constrained inversion was computed using density values measured on 315 core samples collected from 21 drill holes completed between 2014 and 2015. The constrained modelling highlights three shallower and smaller low-density bodies that match the geological interpretation and refines the footprint of the gravity anomalies in relation to the current understanding of the deposit. The 3D inversion of gravity data is a valuable tool to guide geologists in exploration of shallow basement-hosted uranium deposits associated with alteration haloes and to assess the deposit gravity geometry.

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Reservoir Physical Property and Controlling Factors for the Lower Youshashan Formation in Youshashan-Dawusi Area, Southwestern Qaidam Basin

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.675-677.1363 ◽

2014 ◽

Vol 675-677 ◽

pp. 1363-1367 ◽

Cited By ~ 1

Author(s):

Guo Min Chen ◽

Quan Wen Liu ◽

Min Quan Xia ◽

Xiang Sheng Bao

Keyword(s):

Qaidam Basin ◽

Sedimentary Environment ◽

Physical Property ◽

Controlling Factors ◽

Reservoir Rock ◽

High Porosity ◽

Delta Front ◽

Thin Sections ◽

Rock Types ◽

Porosity And Permeability

The core data, casting thin sections and scanning electron microscopy are used to study the clastic reservoir characteristics and controlling factors of reservoir growth. It indicated that the main reservoir rock types are lithic arkose, Feld spathic sandstone, and a small amount of feldspar lithic sandstone, and with compositional maturity and low to middle structural maturity. Moreover, the primary reservoir space types are mainly intergranular pores, secondary are secondary pores, and reservoir types belong to the medium-high porosity and permeability, and the average porosity and permeability of lower Youshashan formation are 17.70% and 112.5×10-3μm2 separately. Furthermore, the reservoir body is mainly sand body result from deposits of distributary channel and mouth bar of which belong to the braided delta front, and the planar physical property tends to be better reservoir to worse reservoir from northwest to southeast. Finally, mainly factors to control the distribution of reservoir physical property, are the sedimentary environment and lithology, were worked out.

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Weak faults at megathrust plate boundary respond to tidal stress

Earth Planets and Space ◽

10.1186/s40623-021-01414-3 ◽

2021 ◽

Vol 73 (1) ◽

Author(s):

Takashi Tonegawa ◽

Toshinori Kimura ◽

Kazuya Shiraishi ◽

Suguru Yabe ◽

Yoshio Fukao ◽

...

Keyword(s):

Physical Properties ◽

Subduction Zones ◽

Seismic Anisotropy ◽

High Tide ◽

Three Dimensional ◽

Plate Boundary ◽

Physical Property ◽

Ocean Bottom ◽

Tidal Stress ◽

Slow Earthquakes

AbstractLateral spatial variations of weak portions at the plate boundary in subduction zones have been estimated primarily by the distribution of slow earthquakes mainly occurring around seismogenic zones. However, the detailed depth profile of weak faults remains elusive. Here, we deployed six ocean bottom seismometers in the Nankai subduction zone, Japan, to observe reflections originated from drilling vessel Chikyu ship noise (hydroacoustic P wave) that was persistently radiated from a fixed position at the sea surface, and retrieved P-to-s (Ps) reflections from multiple dipping faults near the plate boundary. The Ps amplitudes were stacked and compared according to the degrees of tidal stresses, and high amplitudes were observed at high tide (compression). A migration technique shows that the locations where velocity contrasts fluctuate were estimated at both the megasplay fault and another fault between the megasplay fault and the top of the oceanic crust. This indicates that the physical properties of these faults are altered by tidal stress. The physical-property changes are attributed to fluid connections and isolations within the faults due to tidal stress fluctuations, inducing the variation of seismic anisotropy. Such a variation was confirmed by a three-dimensional numerical simulation for wave propagation with anisotropic medium. Our observation suggests that multiple weak faults are present around the plate boundary, and the obtained changes of fault physical properties may have implications for in-depth understanding of tidal triggering of earthquakes.

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Exploration for unconformity-type uranium deposits with audiomagnetotelluric data: A case study from the McArthur River mine, Saskatchewan, Canada

Geophysics ◽

10.1190/1.2348780 ◽

2006 ◽

Vol 71 (6) ◽

pp. B201-B209 ◽

Cited By ~ 57

Author(s):

Volkan Tuncer ◽

Martyn J. Unsworth ◽

Weerachai Siripunvaraporn ◽

James A. Craven

Keyword(s):

Three Dimensional ◽

Smoothing Function ◽

Western Canada ◽

Well Log ◽

Uranium Deposits ◽

Athabasca Basin ◽

Impedance Data ◽

Basement Fault ◽

3D Effects

Unconformity-type deposits supply a significant amount of the world’s uranium and consist of uranium that is generally codeposited with graphite in a fault zone. The low resistivity of the graphite produces a significant contrast in electrical resistivity, which can be located with electromagnetic (EM) methods. The Athabasca Basin in Western Canada hosts significant uranium deposits, and exploration in deeper parts of the basin has required the application of new EM methods. This paper presents an evaluation of the audiomagnetotelluric (AMT) exploration method at the McArthur River mine in the Athabasca Basin. AMT data were collected at 132 stations on a grid, and two-dimensional (2D) and three-dimensional (3D) inversions were used to generate resistivity models. These models showed two major results: (1) a significant conductor coincident with a major basement fault (P2) and the uranium deposits (this conductor begins at the unconformity at a depth of [Formula: see text] and extends to a depth of at least three km) and (2) a resistive halo which might be caused by the silicification associated with mineralization. However, synthetic inversions showed that this halo could be an artifact of smoothing function in the inversion scheme. The 2D inversions were validated by synthetic inversions, comparison with the 3D inversion models, and correlation with well-log information. 3D AMT forward modeling showed that strong 3D effects are not present in the AMT impedance data. Induction vectors showed more evidence of complexity, but the inclusion of these data in the inversion improved subsurface resolution.

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The Patterson Lake corridor of Saskatchewan, Canada: defining crystalline rocks in a deep-seated structure that hosts a giant, high-grade Proterozoic unconformity uranium system

Geochemistry Exploration Environment Analysis ◽

10.1144/geochem2020-007 ◽

2020 ◽

pp. geochem2020-007

Author(s):

Colin D. Card

Keyword(s):

Large Scale ◽

Shear Zones ◽

Crystalline Rocks ◽

Ductile Deformation ◽

Uranium Deposits ◽

Content Type ◽

Athabasca Basin ◽

Rock Types ◽

Host Rocks ◽

Basin Region

The Patterson Lake corridor in the Athabasca Basin region of Saskatchewan, Canada hosts a large-scale uranium system with two major deposits already delineated. The corridor developed in crystalline rocks of the southwest Rae Province, which host all of the known uranium endowment. Orthogneisses along with voluminous pegmatites are the hosts of the uranium mineralization. These rocks, however, underwent significant open-system metasomatic – hydrothermal modification. Principal amongst these alterations is early and pervasive quartz flooding of the host rocks that resulted in the development of widespread secondary quartzites and associated rock types. These secondary quartzites and their altered host rocks suffered ductile deformation, typically focussed at silicification fronts. Late carbonatite dykes exploited the associated shear zones. Semi-brittle deformation zones nucleated near the previously developed ductile high-strain zones. Graphite and associated iron-sulphides precipitated in a semi-brittle structural regime. These graphitized zones provided the necessary structural architecture to focus the uranium system, which developed may be hundreds of millions of years younger developing at ∼1.425 Ga.Host rocks of the Patterson Lake corridor prove that metasedimentary rocks are not a requirement for development of giant Proterozoic unconformity uranium deposits. Crustal-scale fault zones with access to the mantle (i.e. carbonatites) should be considered a key parameter in the exploration model for Proterozoic unconformity uranium deposits. Given the similarity of the mineral assemblages in the crystalline basement rocks of the main exploration corridor to eastern Athabasca Basin region, it is likely that a similar, cryptic geological boundary focussed the giant uranium system in that region.Thematic collection: This article is part of the Uranium Fluid Pathways collection available at: https://www.lyellcollection.org/cc/uranium-fluid-pathways

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Flood vulnerability assessment in the Accra Metropolis, southeastern Ghana

Applied Water Science ◽

10.1007/s13201-021-01463-9 ◽

2021 ◽

Vol 11 (7) ◽

Author(s):

Benjamin Wullobayi Dekongmen ◽

Amos Tiereyangn Kabo-bah ◽

Martin Kyereh Domfeh ◽

Emmanuel Daanoba Sunkari ◽

Yihun Taddele Dile ◽

...

Keyword(s):

Drainage Density ◽

Geological Structures ◽

Flood Vulnerability ◽

Rock Types ◽

Digital Elevation ◽

Annual Population ◽

Density Values ◽

High Runoff ◽

Elevation Model ◽

Very High

AbstractFloods in Ghana have become a perennial challenge in the major cities and communities located in low-lying areas. Therefore, cities and communities located in these areas have been classified as potential or natural flood-prone zones. In this study, the Digital Elevation Model (DEM) of the Accra Metropolis was used to assess the drainage density and elevation patterns of the area. The annual population estimation data and flood damages were assessed to understand the damages and population trend. This research focused primarily on the elevation patterns, slope patterns, and drainage density of the Accra Metropolis. Very high drainage density values, which range between 149 and 1117 m/m2, showed very high runoff converging areas. High drainage density was also found to be in the range of 1117–1702 m/m2, which defined the area as a high runoff converging point. The medium and low converging points of runoff were also found to be ranging between 1702–2563 m/m2 and 2563–4070 m/m2, respectively. About 32% of the study area is covered by natural flood-prone zones, whereas flood-prone zones also covered 33% and frequent flood zones represent 25%. Areas in the Accra Metropolis that fall in the Accraian and Togo series rock types experience high floods. However, the lineament networks (geological structures) that dominate the Dahomeyan series imply that the geological structures in the Dahomeyan series also channel the runoffs into the low-lying areas, thereby contributing to the perennial flooding in the Accra Metropolis.

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