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.

Topographic features of the sub-Athabasca Group unconformity surface in the southeastern Athabasca Basin and their relationship to uranium ore deposits

2015 ◽  
Vol 52 (10) ◽  
pp. 903-920 ◽  
Author(s):  
Zenghua Li ◽  
Kathryn M. Bethune ◽  
Guoxiang Chi ◽  
Sean A. Bosman ◽  
Colin D. Card
Keyword(s):  
Cross Sections ◽  
Regional Scale ◽  
Three Dimensional ◽  
Shear Zones ◽  
Ore Deposits ◽  
Athabasca Basin ◽  
Topographic Features ◽  
Dominant Sets ◽  
Lake Deposits ◽  
Unconformity Surface

Topographic features of the sub-Athabasca unconformity surface, such as paleovalleys, topographic highs, and fault scarps, have been documented locally in the eastern Athabasca Basin, and available data indicate that they are spatially associated with mineralization. However, the mechanisms by which such topographic features were generated, their size and distribution at the regional scale, as well as their relationship to mineralization, are still not completely understood. A 100 by 60 square kilometre area of the southeastern Athabasca Basin, encompassing the McArthur River, Phoenix, and Key Lake deposits, was selected to study the relationship between these topographic features and U mineralization. In this region three dominant sets of sub-vertical faults were identified on the basis of aeromagnetic data: northeast-trending, north–northwest-trending, and northwest-trending. A detailed three-dimensional (3-D) model of this part of the basin was constructed using data from more than 1200 drill holes. This model reveals numerous dominantly northeast-trending ridges and valleys in the unconformity surface. Among these, a prominent northeast-trending ridge is situated close to the McArthur River – Key Lake deposits trend. Structural interpretation and cross-sections illustrate that the topographic features that have been documented in previous studies are a function of three principal factors: (i) pre-Athabasca group ductile-brittle faulting and alteration; (ii) differential weathering and erosion; and (iii) syn- to post-Athabasca ductile-brittle reactivation of pre-existing graphite-rich ductile shear zones. The topographic features and associated faults may have acted as conduits and barriers to fluid flow and thus controlled alteration patterns and uranium mineralization.

scholarly journals Tectono-metamorphic evolution of the pre-Athabasca basement within the Wollaston–Mudjatik Transition Zone, Saskatchewan

2016 ◽  
Vol 53 (3) ◽  
pp. 231-259 ◽  
Author(s):  
Pauline Jeanneret ◽  
Philippe Goncalves ◽  
Cyril Durand ◽  
Pierre Trap ◽  
Didier Marquer ◽  
...  
Keyword(s):  
Transition Zone ◽  
Shear Zones ◽  
Structural Level ◽  
Metamorphic Evolution ◽  
Oblique Collision ◽  
Athabasca Basin ◽  
Strain Pattern ◽  
Exploration Drilling ◽  
Peak Pressures ◽  
Drilling Project

The Paleoproterozoic tectono-metamorphic evolution of the pre-Athabasca basement (∼1.7 Ga) within the Wollaston–Mudjatik Transition Zone (WMTZ) (Saskatchewan, Canada) has been characterized using both exposed basement and drill cores from the Wolly–McClean exploration drilling project. The finite ductile strain pattern of the WMTZ results from the superposition of two tectono-metamorphic events M1–D1 and M2–D2. M1–D1 is associated with the development of a gently dipping foliation striking N90°–N100° and a southward decrease in peak pressures from up to 10 kbar (1 kbar = 100 MPa) in the Cochrane River area down to 6 kbar in the Wolly–McClean exploration drilling project. The M2–D2 event is responsible for the main northeasterly trend of the WMTZ that developed in a sinistral transpressional tectonic regime during the final oblique collision of the Trans-Hudson Orogeny. Thermobarometric estimations on M2–D2 assemblages show that the studied area was reequilibrated at about 4–5 kbar and 750–825 °C. The basement has thus been affected by a differential isothermal decompression event between D1 and D2 that allowed the juxtaposition of the deepest northeastern domains and the Wolly–McClean exploration drilling project, at the same structural level. These results suggest that the basement exposed to the northeast of the Athabasca Basin is not an analog of the basement located beneath the eastern Athabasca Basin where uranium-enriched granitic pegmatites and granites are known. We also suggest that uranium-enriched melts produced during the early M1–D1 stage of partial melting in the deep crust were transferred to the midcrust, owing to D2 shear zones, where they have differentiated to produce uranium-bearing pegmatites.

3D seismic survey at the Millennium uranium deposit, Saskatchewan, Canada: Mapping depth to basement and imaging post-Athabasca structure near the orebody

Geophysics ◽  
2012 ◽  
Vol 77 (5) ◽  
pp. WC245-WC258 ◽  
Author(s):  
Niklas Juhojuntti ◽  
Garnet Wood ◽  
Christopher Juhlin ◽  
Clare O’Dowd ◽  
Peter Dueck ◽  
...  
Keyword(s):  
Hydrothermal Alteration ◽  
Uranium Deposit ◽  
Three Dimensional ◽  
Seismic Interpretation ◽  
Primary Objective ◽  
Mine Planning ◽  
Seismic Survey ◽  
Seismic Image ◽  
Uranium Exploration ◽  
Static Corrections

Three-dimensional seismic reflection measurements have been used to assist mine planning at the Millennium uranium deposit, Canada. The deposit is located within the crystalline basement, separated from the overlying Athabasca Basin sediments by an unconformity potentially associated with significant fluid flow. The primary objective of the [Formula: see text] survey was to image the unconformity and possible post-Athabasca deformation structures in and around the deposit. Clear unconformity reflections are observed within most of the survey area, although there are amplitude variations due to complex geology, including intense hydrothermal clay alteration around the deposit. Finite-difference modeling indicates that the wide-angle character of the unconformity reflections is due to a gradual velocity increase at the unconformity. The reflections are obscured by large time delays, due to Quaternary sediments covering the area, making refraction static corrections crucial. The seismic interpretation shows large variations in the unconformity depth (from approximately 430 to 650 m), indicating a pronounced basement depression that coincides with a gravity low. Reflections from the unconformity are vague within the depression, especially in the vicinity of the deposit. Although the orebody is not directly visible in the seismic image, there is a lack of reflectivity coincident with the alteration surrounding the mineralization. We also observed reflections which likely originate at the contact between the altered and fresh basement rock located beneath the deposit. The seismic data further indicate post-Athabasca faults in the vicinity of the orebody. Based on the initial seismic interpretation, the depth of the crown pillar was adjusted and the mine infrastructure moved away from areas interpreted to be affected by the intense hydrothermal alteration surrounding the deposit. The capability to image the unconformity, post-Athabasca structure, and hydrothermal alteration also highlights the potential use of seismic surveys in uranium exploration.

scholarly journals Preliminary results are in from mid-ocean ridge three-dimensional seismic reflection survey

Eos ◽  
1999 ◽  
Vol 80 (16) ◽  
pp. 181 ◽  
Author(s):  
S. C. Singh ◽  
M. C. Sinha ◽  
A. J. Harding ◽  
G. M. Kent ◽  
P. J. Barton ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Three Dimensional ◽  
Preliminary Results ◽  
Mid Ocean Ridge ◽  
Ocean Ridge

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.

Effective utilization of seismic reflection technique with moderate cost in uranium exploration

2019 ◽  
Vol 68 (1) ◽  
pp. 129-144
Author(s):  
Zoltán Hajnal ◽  
Ernő Takács ◽  
Irvine R. Annesley ◽  
Bhaskar Pandit
Keyword(s):  
Seismic Reflection ◽  
Effective Utilization ◽  
Uranium Exploration ◽  
Moderate Cost

Three-dimensional strain accumulation and partitioning in an arcuate orogenic wedge: An example from the Himalaya

2020 ◽  
Vol 133 (1-2) ◽  
pp. 3-18 ◽  
Author(s):  
Suoya Fan ◽  
Michael A. Murphy
Keyword(s):  
Cross Sections ◽  
Three Dimensional ◽  
Western Himalaya ◽  
Shear Zones ◽  
High Elevation ◽  
Central Himalaya ◽  
Structural Style ◽  
Orogenic Wedge ◽  
Oblique Convergence ◽  
Thickness Variations

Abstract In this study, we use published geologic maps and cross-sections to construct a three-dimensional geologic model of major shear zones that make up the Himalayan orogenic wedge. The model incorporates microseismicity, megathrust coupling, and various derivatives of the topography to address several questions regarding observed crustal strain patterns and how they are expressed in the landscape. These questions include: (1) How does vertical thickening vary along strike of the orogen? (2) What is the role of oblique convergence in contributing to along-strike thickness variations and the style of deformation? (3) How do variations in the coupling along the megathrust affect the overlying structural style? (4) Do lateral ramps exist along the megathrust? (5) What structural styles underlie and are possibly responsible for the generation of high-elevation, low-relief landscapes? Our model shows that the orogenic core of the western and central Himalaya displays significant along-strike variation in its thickness, from ∼25–26 km in the western Himalaya to ∼34–42 km in the central Himalaya. The thickness of the orogenic core changes abruptly across the western bounding shear zone of the Gurla Mandhata metamorphic core complex, demonstrating a change in the style of strain there. Pressure-temperature-time results indicate that the thickness of the orogenic core at 37 Ma is 17 km. Assuming this is constant along strike from 81°E to 85°E indicates that, the western and central Nepal Himalaya have been thickened by 0.5 and 1–1.5 times, respectively. West of Gurla Mandhata the orogenic core is significantly thinner and underlies a large 11,000 km2 Neogene basin (Zhada). A broad, thick orogenic core associated with thrust duplexing is collocated with an 8500 km2 high-elevation, low-relief surface in the Mugu-Dolpa region of west Nepal. We propose that these results can be explained by oblique convergence along a megathrust with an along-strike and down-dip heterogeneous coupling pattern influenced by frontal and oblique ramps along the megathrust.

Crustal structure and surface zonation of the Canadian Appalachians: implications of deep seismic reflection data

1989 ◽  
Vol 26 (2) ◽  
pp. 305-321 ◽  
Author(s):  
François Marillier ◽  
Charlotte E. Keen ◽  
Glen S. Stockmal ◽  
Garry Quinlan ◽  
Harold Williams ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Three Dimensional ◽  
Surface Expression ◽  
Seismic Profiles ◽  
Crust And Upper Mantle ◽  
Seismic Reflection Data ◽  
Central Block ◽  
Reflection Data ◽  
Lower Crustal ◽  
Canadian Appalachians

In 1986, 1181 km of marine seismic reflection data was collected to 18–20 s of two-way traveltime in the Gulf of St. Lawrence area. The seismic profiles sample all major surface tectono-stratigraphic zones of the Canadian Appalachians. They complement the 1984 deep reflection survey northeast of Newfoundland. Together, the seismic profiles reveal the regional three-dimensional geometry of the orogen.Three lower crustal blocks are distinguished on the seismic data. They are referred to as the Grenville, Central, and Avalon blocks, from west to east. The Grenville block is wedge shaped in section, and its subsurface edge follows the form of the Appalachian structural front. The Grenville block abuts the Central block at mid-crustal to mantle depths. The Avalon block meets the Central block at a steep junction that penetrates the entire crust.Consistent differences in the seismic character of the Moho help identify boundaries of the deep crustal blocks. The Moho signature varies from uniform over extended distances to irregular with abrupt depth changes. In places the Moho is offset by steep reflections that cut the lower crust and upper mantle. In other places, the change in Moho elevation is gradual, with lower crustal reflections following its form. In all three blocks the crust is generally highly reflective, with no distinction between a transparent upper crust and reflective lower crust.In general, Carboniferous and Mesozoic basins crossed by the seismic profiles overlie thinner crust. However, a deep Moho is found at some places beneath the Carboniferous Magdalen Basin.The Grenville block belongs to the Grenville Craton; the Humber Zone is thrust over its dipping southwestern edge. The Dunnage Zone is allochthonous above the opposing Grenville and Central blocks. The Gander Zone may be the surface expression of the Central block or may be allochthonous itself. There is a spatial analogy between the Avalon block and the Avalon Zone. Our profile across the Meguma Zone is too short to seismically distinguish this zone from the Avalon Zone.

scholarly journals Entrainment and abrasion of megaclasts during submarine landsliding and their impact on flow behaviour

2018 ◽  
Vol 477 (1) ◽  
pp. 223-240 ◽  
Author(s):  
D. M. Hodgson ◽  
H. L. Brooks ◽  
A. Ortiz-Karpf ◽  
Y. Spychala ◽  
D. R. Lee ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Three Dimensional ◽  
Submarine Landslides ◽  
Seismic Reflection Data ◽  
Karoo Basin ◽  
Reflection Data ◽  
Seabed Topography ◽  
Flow Evolution ◽  
Basal Shear ◽  
Process Product

AbstractMany mass transport complexes (MTCs) contain up to kilometre-scale (mega)clasts encased in a debritic matrix. Although many megaclasts are sourced from the headwall areas, the irregular basal shear surfaces of many MTCs indicate that megaclast entrainment during the passage of flows into the deeper basin is also common. However, the mechanisms responsible for the entrainment of large blocks of substrate, and their influence on the longitudinal behaviour of the associated flows, have not been widely considered. We present examples of megaclasts from exhumed MTCs (the Neuquén Basin, Argentina and the Karoo Basin, South Africa) and MTCs imaged in three-dimensional seismic reflection data (Magdalena Fan, offshore Colombia and Santos Basin, offshore Brazil) to investigate these process–product interactions. We show that highly sheared basal surfaces are well developed in distal locations, sometimes extending beyond their associated deposit. This points to deformation and weakening of the substrate ahead of the flow, suggesting that preconditioning of the substrate by distributed shear ahead of, and to the side of, a mass flow could result in the entrainment of large fragments. An improved understanding of the interactions between flow evolution, seabed topography, and the entrainment and abrasion of megaclasts will help to refine estimates of run-out distances, and therefore the geohazard potential of submarine landslides.

scholarly journals Formation of band ogives and associated structures at Bas Glacier d’Arolla, Valais, Switzerland

2002 ◽  
Vol 48 (161) ◽  
pp. 287-300 ◽  
Author(s):  
Becky Goodsell ◽  
Michael J. Hambrey ◽  
Neil F. Glasser
Keyword(s):  
Ground Penetrating Radar ◽  
Three Dimensional ◽  
Shear Zones ◽  
Glacier Surface ◽  
Glacier Tongue ◽  
Basal Ice ◽  
Planar Structures ◽  
Geophysical Techniques ◽  
Reverse Faulting ◽  
Ground Penetrating

AbstractStructural glaciological, sedimentological and geophysical techniques are used to provide new insight concerning the formation of band ogives and associated structures at Bas Glacier d’Arolla, Switzerland. Sedimentary stratification, crevasse traces and transverse foliation are identified as planar structures in the lower icefall and glacier tongue. Stratification and crevasse traces are progressively deformed into, and enhance, the transverse foliation found in the glacier tongue. Three-dimensional geometry has been defined using ground-penetrating radar, which portrays four main characteristics: (i) deep reflectors interpreted as the ice/bed interface, (ii) alternating reflection-rich and reflection-poor zones interpreted as ogives, (iii) up-glacier-dipping reflectors, interpreted as planar structures, and (iv) down-glacier-dipping reflectors of uncertain origin. At the glacier surface, each band ogive consists of a light and dark band. The dark bands contain more intense foliation which, on differential weathering, traps fine debris. Clasts and clear ice of basal character within dark ogive bands suggest that basal ice has been raised to the glacier surface. The most applicable model for the formation of band ogives at Bas Glacier d’Arolla is a refinement of Posamentier’s (1978) “reverse faulting” hypothesis. In this context, multiple shear zones are formed, through which basal ice is uplifted to the glacier surface to produce the dark, foliated ogive bands. This model fits observations reported from other glaciers with band ogives.

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