Litho-structural layering within the Archean Lac du Bonnet Batholith, at AECL’s Underground Research Laboratory, Southeastern Manitoba

Everitt, R.A.; Brown, A.E.P.; Ejeckam, R.B.; Sikorsky, R.; Woodcock, D R

doi:10.1016/s0191-8141(98)00068-6

Cited by 13 publications

(6 citation statements)

References 7 publications

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“…Domain-wise analysis shows that fracture frequency of a single rock type is higher in the domains having lithological contacts than that in domains without any lithocontact, indicating domains with lithological contacts are hydrologically more important than domains with single lithology. Histogram of fracture frequency in same lithology for grids with (i) lithological contacts and (ii) single lithology shows that grids with lithological contacts are characterised by comparatively higher values of fracture-frequency than monolithic grids, indicating spatial correlation between high fracture-frequency with lithostratigraphic contact, which is also supported by several workers (Everitt et al 1996).…”

Section: Resultssupporting

confidence: 77%

“…The present study demonstrates that the line, containing high-discharging dugwells in each group assigned as 'dugwell-line', actually occurs over a highly weathered zone with thick saprolite and fissured rock zones concurrent with lithostratigraphic contact and a subsurface intense fracture zone with deeper weathered zone (Acharya and Prasad 2014). Several studies (Neretnieks 1985;Crawford and Brackett 1995;Everitt et al 1996;Deyell and Sherlock 2003;Lachassagne et al 2011) demonstrated that along and near such lithologic contacts, differential deformation stress and weathering at low topographic region may often create zones of enhanced permeability and pathways for groundwater flow.…”

Section: Resultsmentioning

confidence: 51%

“…This is due to the ductile nature of the mica schist (Morland 1997;Banks and Robins 2002;Cook 2003). The limiting distance from the contact maintaining the higher fracture-frequency value is assigned as the 'influence zone' for the contact concerned, e.g., for granite gneissic rock 900 m, phylliteepidiorite 320 m and epidiorite-phyllite 80 m. The results clearly reveal the significant role of the lithostratigraphic; contact to influence and increase the fracture-frequency within its 'influence zone', assigning those fractures to be more hydrologically significant (Braathen 1999; near the lithostratigraphic contact, in turn, assigning lithostratigraphic contact to be more hydraulically significant (Everitt et al 1996). Furthermore, fractures, those are making higher angle than the 'limiting angle' with the lithostratigraphic contact concerned, i.e., ≥70 • in quartz-biotite granite gneiss and ≥50 • phyllite and epidiorite, clearly show a sharp and consistent increase in fracture-frequency within the 'influence zone' of the lithocontact.…”

Section: Resultsmentioning

confidence: 88%

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Lithostratigraphic contact – a significant site for hydrogeological investigation in crystalline fractured-rock terrains

Acharya

Prasad

2017

J Earth Syst Sci

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Estimating the hydrogeologic control of fractured aquifers in hard crystalline and metamorphosed rocks is challenging due to complexity in the development of secondary porosity. The present study in the Precambrian metamorphic terrain in and around the Balarampur of Purulia district, West Bengal, India, aims to estimate the hydrogeologic significance of lithostratigraphic contacts using fracture characteristics obtained from surface bedrock exposures supported by hydrological data from the existing dugwells. This study involves the domain-wise analysis of the frequencies of fractures that control the fractureporosity. The domain-wise study reveals higher fracture-frequencies adjacent to the lithostratigraphic contacts. The concurrence of lithostratigraphic contacts with the occurrences of high-discharging wells and also with the deep weathered zone in low-lying areas is clearly established, thus assigning the lithostratigraphic contact as hydrogeologically significant. An increase in frequencies of the fractures within the 'influence zone' of the lithocontact, is clearly visible. Among those fractures, particularly, which make the angle greater than the 'limiting angle' with the lithocontact are characterised by increased frequencies. However, brittle rocks like quartz biotite granite gneisses, phyllite and epidiorite show high porosity of fracture, within the 'influence zone' of the lithostratigraphic contact. Enhanced deepening of the weathered-zone at lower topographic region may perhaps be a plausible explanation for this increased fracture-porosity at lithocontact to assign it as a hydrogeologically significant transmissive zone within fractured rocks.

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Section: Resultssupporting

confidence: 77%

Section: Resultsmentioning

confidence: 51%

Section: Resultsmentioning

confidence: 88%

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Lithostratigraphic contact – a significant site for hydrogeological investigation in crystalline fractured-rock terrains

Acharya

Prasad

2017

J Earth Syst Sci

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“…Sample WN-1 is an Archean granodiorite from the Winnipeg River Subprovince of the Superior craton from the Lac du Bonnet Batholith emplaced at 2665 ± 20 to 2568 ± 23 Ma (Everitt et al, 1996 and references therein). This sample was from a borehole core at 30.5 m depth and was previously dated via biotite 40 Ar/ 39 Ar, yielding an age of 2291 ± 27 Ma (Hunt and Roddick, 1988).…”

Section: Western Superior Province Ontariomentioning

confidence: 99%

Instability of the southern Canadian Shield during the late Proterozoic

McDannell

Zeitler

Schneider

2018

Earth and Planetary Science Letters

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Cratons are generally considered to comprise lithosphere that has remained tectonically quiescent for billions of years. Direct evidence for stability is mainly founded in the Phanerozoic sedimentary record and low-temperature thermochronology, but for extensive parts of Canada, earlier stability has been inferred due to the lack of an extensive rock record in both time and space. We used 40 Ar/ 39 Ar multi-diffusion domain (MDD) analysis of K-feldspar to constrain cratonic thermal histories across an intermediate (~150-350°C) temperature range in an attempt to link published high-temperature geochronology that resolves the timing of orogenesis and metamorphism with lower-temperature data suited for upper-crustal burial and unroofing histories. This work is focused on understanding the transition from Archean-Paleoproterozoic crustal growth to later intervals of stability, and how uninterrupted that record is throughout Earth's Proterozoic "Middle Age." Intermediate-temperature thermal histories of cratonic rocks at well-constrained localities within the southern Canadian Shield of North America challenge the stability worldview because our data indicate that these rocks were at elevated temperatures in the Proterozoic. Feldspars from granitic rocks collected at the surface cooled at rates of <0.5°C/Ma subsequent to orogenesis, seemingly characteristic of cratonic lithosphere, but modeled thermal histories suggest that at ca. 1.1-1.0 Ga these rocks were still near ~200°Csignaling either reheating, or prolonged residence at mid-crustal depths assuming a normal cratonic geothermal gradient. After 1.0 Ga, the regions we sampled then underwent further cooling such that they were at or near the surface (<< 60°C) in the early Paleozoic. Explaining mid-crustal residence at 1.0 Ga is challenging. A widespread, prolonged reheating history via burial is not supported by stratigraphic information, however assuming a purely monotonic cooling history requires at the very least 5 km of exhumation beginning at ca. 1.0 Ga. A possible McDannell et al.-Late Proterozoic Instability of the Canadian Shield 2 explanation may be found in evidence of magmatic underplating that thickened the crust, driving uplift and erosion. The timing of this underplating coincides with Mid-Continent extension, Grenville orogenesis, and assembly of the supercontinent Rodinia. 40 Ar/ 39 Ar MDD data demonstrate that this technique can be successfully applied to older rocks and fill in a large observational gap. These data also raise questions about the evolution of cratons during the Proterozoic and the nature of cratonic stability across deep time.

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“…The lithological and structural delamination of the batholith was revealed by sinking a shaft down to a depth of 443 m. The delamination is manifested in low-angle contacts between granitoids pertaining to different intrusive phases, the same attitude of xenoliths composed of amphibolized rocks, pegmatite dikes, and quartz-epidote-chlorite veins. The delamination is emphasized by three gently dipping zones of elevated fracturing and hydrothermal alteration of rocks (Everitt et al, 1998). The lithological and structural delamination is accompanied by geomechanical heterogeneity.…”

Section: Natural Analogues and Underground Laboratories In Granite: Amentioning

confidence: 99%

The Antei uranium deposit: A natural analogue of an SNF repository and an underground geodynamic laboratory in granite

et al. 2008

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The estimation of the long-term stability of crystalline rock massifs with respect to natural and technogenic loads in the course of long-term storage of spent nuclear fuel (SNF) is a special area of surveys at underground research laboratories (URLs). In parallel with these surveys, data on uranium deposits-natural analogues of repositories of SNF consisting of 95% UO 2 -are used for obtaining insight into the dynamics of radionuclide migration and validating barrier properties of host rocks. Examples of URLs located in granitic massifs of Sweden (Äspö), Canada (Whiteshell), Switzerland (Grimsel), Japan (Mizunami), and Finland (ONKALO), as well as the El Berrocal (Spain), Palmottu (Finland), Sanerliu (China), and Kamaishi (Japan) deposits, are considered in the paper. The objects listed above are distinct in tectonic settings, geology, control of ore mineralization, redox conditions of uranium migration, and character and intensity of filtration and transportation, which predetermine the direction and specific features of research conducted therein. A variant in which a URL and a natural analogue are combined in one object is especially promising for validation of safe long-term isolation of SNF. The Antei vein-stockwork uranium deposit in the southeastern Transbaikal region, localized in Paleozoic granite at a depth of 400-1000 m and opened by mine workings at six levels, is such an object. Its geological features, stress-strain state, and infrastructure of mine workings offer an opportunity to study the entire spectrum of processes proceeding in near-and far-field of an SNF repository. The structural geology, mineralogy and petrography, and petrophysical and tectonophysical features of the deposit at its three lower levels are considered. The sequence of metasomatic alteration of rocks and the dynamics of formation of ore-bearing faults that crosscut prototectonic elements, as well as relationships of physicomechanical properties of rocks as a function of the intensity of their metasomatic alteration and the distance from master fault planes, have been established. A 3D geological model of the deposit in combination with estimated parameters of the present-day stress field and physicomechanical properties of particular rock blocks serves as the basis for prediction of the geomechanical behavior of the massif. The practical implications of the results obtained for assessment of the long-term safety of SNF repositories in granites are discussed.

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Litho-structural layering within the Archean Lac du Bonnet Batholith, at AECL’s Underground Research Laboratory, Southeastern Manitoba

Cited by 13 publications

References 7 publications

Lithostratigraphic contact – a significant site for hydrogeological investigation in crystalline fractured-rock terrains

Lithostratigraphic contact – a significant site for hydrogeological investigation in crystalline fractured-rock terrains

Instability of the southern Canadian Shield during the late Proterozoic

The Antei uranium deposit: A natural analogue of an SNF repository and an underground geodynamic laboratory in granite

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