A seismic-based cross-section of the Grenville Orogen in southern Ontario and western Quebec

White, Donald J; Forsyth, D.A.; Asudeh, I.; Carr, S.D.; Wu, H.; Easton, R.M.; Mereu, R.F.

doi:10.1139/cjes-37-2-3-183

Cited by 17 publications

(22 citation statements)

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“…Cook et al, 2004;2005;Evenchick et al, 2005). The Abitibi-Grenville Transect (Winardi and Mereu, 1997;Ludden and Hynes, 2000;Mereu, 2000;White et al, 2000) is of particular interest for this comparisson and discussed later on.…”

Section: The Lower Crust (> 25 Km) and Mohomentioning

confidence: 95%

“…With the completion of the Abitibi-Grenville (AG) transect during the Lithoprobe program (e.g. Clowes et al, 1996Ludden and Hynes, 2000;Martignole et al, 2000;White et al, 2000), and now the AKGTransect completed during the Inkaba yeAfrica project, a direct comparison of the deep crustal structures of these two areas can be attempted. For the purpose of this brief analysis, AG lines 32 and 33 Ludden and Hynes, 2000;White et al, 2000) are the most appropriate lines for direct comparison with the IyA-200501 seismic transect (Figures 13 and 14).…”

Section: Rodinian Connectionsmentioning

confidence: 99%

“…Some distinct differences occur between these two sections on either side of the Grenville-Kibaran Orogen, but none of these rule out their co-evolution. (Ludden and Hynes, 2000;White et al, 2000;yellow dashed box) iv. the mid-crustal tectonic fabric of the AG 32-33 profile dips away from the craton (green and blue, Figure 14b) whereas the mid-crust fabric in IyA-200501 dips towards the craton (orange, Figure 14b).…”

Section: Rodinian Connectionsmentioning

confidence: 99%

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Deep Crustal Profile Across the Southern Karoo Basin and Beattie Magnetic Anomaly, South Africa: An Integrated Interpretation With Tectonic Implications

Lindeque

Wit

Ryberg

et al. 2011

South African Journal of Geology

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Two geophysical onshore-offshore lines on the southern margin of Africa form the Agulhas-Karoo Geophysical Transect (AKGT) and cross prominent geological features such as the Karoo Basin, Cape Fold Belt (CFB) and the Beattie Magnetic Anomaly (BMA). Geophysical data acquired along this AKGTransect between 2004 and 2007 within the Inkaba yeAfrica (lyA) framework, provide the platform for constructing a deep crustal section (IyA-200501) for the centre 100 km of the western AKGT-transect in order to resolve these features at depth. We present a detailed deep crustal model constructed from the joint interpretation of: i. archive data comprising surface geology, aeromagnetic data, nearby deep boreholes, teleseismic receiver functions and regional seismic reflection profiles, and ii. line coincident newly acquired high-resolution geophysical data consisting of near vertical seismic reflection data, shallow P-and S-wave velocity data, wide-angle refraction data, high resolution magnetotelluric data and impedance spectroscopy measurements on borehole samples. Our model differentiates four components in the up to 45 km thick crust: 1. a ~2 to 5 km thick folded Karoo Supergroup, disrupted by low-angle thrust faults rooted in a zone of local décollements in the lower Ecca Group and resting paraconformably on 2. a continuous undeformed sub-horizontal ~1.5 to 10 km thick wedge of the Cape Supergroup (CSG). This CSG wedge stretches from the Escarpment in the north to the tectonic front of the CFB in the south, and rests on an unconformity that dips about three degrees to the south. The angular unconformity is interpreted as an erosional peneplain that separates the CSG wedge from component 3. the ~13 to 21 km mid-crust basement below. The mid-crust contains a distinct north-dipping seismic fabric, here interpreted as 1.4 to 1.0 Ga Mesoproterozoic Namaqua-Natal Metamorphic Belt (NNMB) crust. A south-dipping mid-crustal detachment, interpreted as a ductile thrust zone, separates the mid-crust from component 4. a highly reflective ~10 to 24 km thick lower crust. The latter is interpreted as an older Palaeoproterozoic section of the NNMB (or even Archean cratonic basement), and bounded by a ~2 to 5 km thick, highly reflective bottom layer below that lies subparallel to a clear Moho. This bottom layer is interpreted as a mafic underplate, metasomatic reaction zone, or lower-crust to mantle transition zone. Collectively the seismic reflection and wide-angle refraction data support an interpretation that the NNMB mid-crustal layer contains the BMA source, possibly connected to two zones of strong reflectivity: a ~10 to 12 km wide northern zone and a ~5 to 7 km wide southern zone, both about 5 km thick and 7 to 8 km below surface. We interpret the BMA source to be at least in part, a Namaqua-like massive to disseminated, deformed/metamorphosed stratiform sulphide-magnetite ore body with metasomatic overprint.

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Section: The Lower Crust (> 25 Km) and Mohomentioning

confidence: 95%

Section: Rodinian Connectionsmentioning

confidence: 99%

Section: Rodinian Connectionsmentioning

confidence: 99%

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Deep Crustal Profile Across the Southern Karoo Basin and Beattie Magnetic Anomaly, South Africa: An Integrated Interpretation With Tectonic Implications

Lindeque

Wit

Ryberg

et al. 2011

South African Journal of Geology

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“…Such relationships between the images of the crust obtained with refraction and reflection seismic methods were established in various geological situations Mitrofanov et al, 1998;White et al, 2000;Kuusisto et al, 2006;Cook et al, 2010]. Therefore, especially important are evidences for partial coordination of the boundaries of density /velocity layering in the crust, on the one hand, and the geological boundaries identified in CMP profiles, on the other hand.…”

Section: Density Layering and Structural Geological Characterization mentioning

confidence: 96%

“…Reflection seismic methods yield widely variable seismic images of the crust-mantle boundary at the base of Precambrian crust, and specific features of such images suggest a dependence on structure and formation history of the crust [BABEL Working Group, 1990;Abramovitz et al, 1997;White et al, 2000;Van der Velden, Cook, 2005;Kukkonen, Lahtinen, 2006;Mints et al, 2009Mints et al, , 2015Cook et al, 2010;Hammer et al, 2010;Mints, 2011]. It is assumed that beneath the Precambrian cratons, as a rule, this boundary is rather distinctly expressed in the replacement of the moderately or intensely reflecting lower crust by the mantle domain that is acoustically transparent.…”

Section: Introductionmentioning

confidence: 99%

Geologic transect across the Grenville orogen of Ontario and New York

et al. 2000

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Abstract:The complex geophysical 3D model of the Earth's crust and the upper mantle is created for the Archaean Karelian Craton and the Late Palaeoproterozoic accretionary Svecofennian Orogen of the southeastern Fennoscandian Shield with the use of methods of complex inversion of geophysical data based on stochastic description of interrelations of physical properties of the medium (density, P-wave velocity, and heat generation). To develop the model, we use results of deep seismic studies, gravity and surficial heat flow data on the studied region. Numerical solutions of 3D problems are obtained in the spherical setting with an allowance for the Earth's surface topography. The geophysical model is correlated with the regional geological data on the surface and results of seismic CMP studies along 4B, FIRE-1 and FIRE-3-3A profiles. Based on results of complex geophysical simulation and geological interpretation of the 3D model, the following conclusions are drawn. (1) The nearly horizontal density layering of the continental crust is superimposed on the previously formed geological structure; rock differentiation by density is decreasing with depth; the density layering is controlled by the recent and near-recent state of the crust, but can be disturbed by the latest deformations. (2) Temperature variations at the Moho are partially determined by local variations of heat generation in the mantle, which, in turn, are related to local features of its origin and transformation. (3) The concept of the lower continental crust being a reflectivity zone and the concept of the lower continental crust being a layer of high density and velocity are not equivalent: the lower crust is the deepest, high-density element of near-horizontal layering, whereas the seismic image of the reflectivity zone is primarily related to transformation of the crust as a result of magmatic under-and intraplating under conditions of extension and mantle-plume activity. (4) At certain combinations of crustal thickness and temperature at the level of Moho discontinuity, the crust in a platform region can be transformed into eclogites. In this case, the crust-mantle boundary is determined by quantitative proportions of the rocks that underwent eclogitization or escaped this process and by corresponding density and velocity values. (5) High compaction of rocks in the crust under lithostatic loading cannot be explained by «simple» concepts of metamorphism and/or rock compaction, which are based on laboratory studies of rock samples and mathematical simulations; this is an evidence of the existence of additional, quite strong mechanisms providing for reversible changes of the rocks.Key words: geophysical simulation, complex inversion, thermal model, density model, CMP seismic profiling, crustalmantle boundary, velocity-density Moho discontinuity, Karelian Craton, Svecofennian Orogen.Recommended by E.V. Sklyarov Аннотация: Трехмерная комплексная геофизическая модель земной коры и верхней части мантии архейско-го Карельского кратона и позднепалеопро...

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Thermo-compositional structure of the north-eastern Canadian Shield from Rayleigh wave dispersion analysis as a record of its tectonic history

Altoe

Eeken

Goes

et al. 2020

Earth and Planetary Science Letters

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The thermal and compositional structure of lithospheric keels underlying cratons, which are stable continental cores formed during the Precambrian, is still an enigma. Mapping lithospheric temperatures and compositional heterogeneities is essential to better understand geodynamic processes that control craton formation and evolution. Here we investigate the northeastern part of North America which comprises the Superior Craton, the largest Archean craton in the world, and surrounding Proterozoic belts. We model Rayleigh-wave dispersion curves from a previous study, which were regionalized based on cluster analysis. Next, we perform a grid search for sub-crustal thermal and compositional structures that are consistent with the average dispersion curve for each cluster. We apply constraints on crustal structure and use thermodynamic methods to map thermo-compositional structures into seismic velocity. In agreement with previous studies, most regions require concentrations of metasomatic minerals over certain depth intervals to fit the seismic profiles. Our results further require vertical as well as lateral variations in compositional and thermal structures, which appear to reflect different stages of formation and modification of the lithosphere below the region, with distinct structures found under Archean cores, Archean/Paleoproterozoic collision belts, mid-late Proterozoic collision belts, and zones affected by rifting.

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A seismic-based cross-section of the Grenville Orogen in southern Ontario and western Quebec

Cited by 17 publications

References 0 publications

Deep Crustal Profile Across the Southern Karoo Basin and Beattie Magnetic Anomaly, South Africa: An Integrated Interpretation With Tectonic Implications

Deep Crustal Profile Across the Southern Karoo Basin and Beattie Magnetic Anomaly, South Africa: An Integrated Interpretation With Tectonic Implications

Geologic transect across the Grenville orogen of Ontario and New York

Thermo-compositional structure of the north-eastern Canadian Shield from Rayleigh wave dispersion analysis as a record of its tectonic history

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