The Central Slave Basement Complex, Part I: its structural topology and autochthonous cover

Bleeker, Wouter; Ketchum, J. W. F.; Jackson, Valerie A.; Villeneuve, M.

doi:10.1139/cjes-36-7-1083

Cited by 23 publications

(42 citation statements)

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“…The exposed Archean crust of the Slave craton is 500 km E‐W by 700 km N‐S, and is surrounded by orogens Paleoproterozoic or younger in age (Figure 1). An ancient gneiss complex (Central Slave Basement Complex of Bleeker et al [1999]) in the west‐central part of the craton hosts some of the oldest rocks on Earth, the ∼4030 Ma Acasta gneisses [ Bowring and Williams , 1999] and is overlain by a thin, ∼2800 Ma quartzite and banded iron formation [ Bleeker et al , 1999]. Basement, exposed in places within large antiformal culminations, is elsewhere overlain or flanked by basalt‐dominated and turbiditic sedimentary rocks of the 2730–2620 Ma Yellowknife Supergroup or equivalent (Figure 2).…”

Section: Geological Setting and Competing Tectonic Modelsmentioning

confidence: 99%

“…The Slave craton is unusual in that crustal studies suggest roughly north‐south trends in large‐scale structure, whereas several independent mantle studies reveal ENE‐WSW trends (Figure 1) [ Davis and Hegner , 1992; Bleeker et al , 1999; Grütter et al , 1999; Davis et al , 2003; Jones et al , 2003; Griffin et al , 2004]. Isotopic studies of large intrusive bodies show Nd and Pb isotope trends with roughly north‐south contours (Figure 1) [ Davis and Hegner , 1992].…”

Section: Geological Setting and Competing Tectonic Modelsmentioning

confidence: 99%

“…This exploration has resulted in an unusually rich petrological, geochronological and geochemical understanding of mantle “stratigraphy” derived from mantle xenoliths and xenocrysts found within the kimberlite deposits that host the mines [e.g., Grütter et al , 1999; Griffin et al , 1999; Kopylova and Caro , 2004; Heaman et al , 2006; O'Reilly and Griffin , 2006]. Equally important are comprehensive surface mapping and related studies providing important constraints on the geological evolution of the whole craton [e.g., Hoffman , 1980; Padgham and Fyson , 1992; Isachsen and Bowring , 1994; Bleeker et al , 1999; Davis and Bleeker , 1999]. Today this geological knowledge base, if less extensive, is arguably equally informative as that of any craton including the Kaapvaal [e.g., Jones et al , 2004].…”

Section: Interpretation Of Discontinuities As Structuresmentioning

confidence: 99%

“…Dotted lines labeled Pb and Nd are crustal boundaries, determined from isotope studies of plutons, that parallel major crustal divisions [ Davis et al , 2003]. Overlay outlines the Central Slave Basement Complex (CSBC) [ Bleeker et al , 1999]. Open diamonds indicate kimberlite deposits; the cluster in the center is the Lac de Gras kimberlite field.…”

Section: Introductionmentioning

confidence: 99%

“…Exploration for diamonds within the Slave craton during the past two decades resulted in an unusually rich petrological and geochemical understanding of its mantle “stratigraphy” as derived from mantle xenoliths and xenocrysts found within the kimberlite eruptions that typically host diamonds [e.g., Grütter et al , 1999; Griffin et al , 1999; Kopylova and Caro , 2004; Heaman et al , 2006; O'Reilly and Griffin , 2006]. Regional surface mapping and related studies have similarly provided important constraints on the geological history of the craton [e.g., Padgham and Fyson , 1992; Bleeker et al , 1999; Davis et al , 2003; Bennett et al , 2005]. All of these results are consistent with a preferred interpretation of mantle layers with distinct seismic properties as representing underthrust and stacked carbon‐laden lithosphere through which sheeted kimberlite eruptions brought diamonds to the near surface [ Snyder and Lockhart , 2005].…”

Section: Introductionmentioning

confidence: 99%

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Stacked uppermost mantle layers within the Slave craton of NW Canada as defined by anisotropic seismic discontinuities

Snyder

2008

Tectonics

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A 20‐station seismic array in NW Canada recorded 336 teleseismic events with distribution in back azimuth and epicentral distance sufficient to characterize uppermost mantle discontinuities between depths typical of the Mohorovicic and Lehman discontinuities. Following wavefield decomposition, groups of seismograms were source‐normalized through simultaneous deconvolution to estimate the near‐receiver impulse response and thus detect major discontinuities beneath each seismic station. Stations within the Lac de Gras kimberlite field display an unusually strong negative impulse on the radial component within the NW quadrant and two moderate impulses on the transverse component. Forward modeling of these impulses suggests a mantle layer dipping at 22° to the southeast with a mildly anisotropic (2%) upper discontinuity at 120–135 km depth and another mildly anisotropic (2%) discontinuity at about 170 km depth. Superimposed on these layers is another, stronger anisotropic (4%) layer between 110 and 180 km depths that dips to the west. Stations outside of the Lac de Gras field, but within the southeastern Slave craton, display more numerous, but weaker, impulses. The most prominent of these occurs at about 150 km depth on the transverse component and has opposite polarity to that observed farther north. The prominent negative impulse observed on the radial component is interpreted to arise from structural‐preferred orientation in the form of a stockwork of wehrlite dykes beneath the Lac de Gras field. Interpretation of the other layers in the context of known surface geology as well as xenolith petrology and garnet geochemistry of diamondiferous kimberlites favors previous suggestions that they represent 4000–2900 Ma depleted harzburgite and eclogite layers underthrust from the northwest at 2600 or 1880 Ma. The layer beneath the SE Slave craton has a similar, but distinct, tectonic history of NW‐verging underthrusting associated with the 2635–2615 Ma Defeat Suite of plutonism. Taken together, these interpretations indicate that the Slave craton was assembled from at least four lithospheric blocks prior to its cratonization about 2580 Ma: each block is 90–120 km thick, and all four blocks abut across a steep suture boundary beneath MacKay Lake in the central Slave craton. Significant amounts of carbon and eclogites could have become incorporated into the central Slave mantle within the diamond stability field during the proposed underthrusting of lithosphere to explain their relatively common occurrence in kimberlite eruptions within the Slave craton.

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Section: Geological Setting and Competing Tectonic Modelsmentioning

confidence: 99%

Section: Geological Setting and Competing Tectonic Modelsmentioning

confidence: 99%

Section: Interpretation Of Discontinuities As Structuresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Stacked uppermost mantle layers within the Slave craton of NW Canada as defined by anisotropic seismic discontinuities

Snyder

2008

Tectonics

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Lithospheric architecture of the Slave craton, northwest Canada, as determined from an interdisciplinary 3‐D model

Snyder

Hillier

Kjarsgaard

et al. 2014

Geochem Geophys Geosyst

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Regional-scale geologic structures characteristic of mantle lithosphere within cratons found in continent interiors are interpreted using geo-registered diverse data sets from the Slave craton of northwest Canada. We developed and applied a new method for mapping seismic discontinuities in three dimensions using multiyear observations at sparse, individual broadband receivers. New, fully 3-D conductivity models used all available magnetotelluric data. Discontinuity surfaces and conductivity models were geo-registered with previously published P-wave and surface-wave velocity models to confirm first-order structures such as a midlithosphere discontinuity. Our 3-D model to 400 km depth was calibrated by ''drill hole'' observations derived from xenolith suites extracted from kimberlites. A number of new structural discontinuities emerge from direct comparison of coregistered data sets and models. Importantly, we distinguish primary mantle layers from secondary features related to younger metasomatism. Subhorizontal Slave craton layers with tapered, wedge-shaped margins indicate construction of the craton core at 2.7 Ga by underthrusting and flat stacking of lithosphere. Mapping of conductivity and metasomatism in 3-D, the latter inferred via mineral recrystallization and resetting of isotopic ages in xenoliths, indicates overprinting of the primary layered structures. The observed distribution of relatively conductive mantle at 100-200 km depths is consistent with pervasive metasomatism; vertical ''chimneys'' reaching to crustal depths in locations where kimberlites erupted or where Au mineralization is known.

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Geochemistry of ultramafic–mafic rocks of the Madawara Ultramafic Complex in the southern part of the Bundelkhand Craton, Central Indian Shield: Implications for mantle sources and geodynamic setting

2018

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Detailed field, petrography and whole‐rock geochemical study was carried out in order to constrain the mantle sources and geodynamic setting of the Madawara Ultramafic Complex (MUC) of the Bundelkhand Craton. Studies reveal that there are two types of ultramafic rocks: (a) high‐Mg ultrabasic/basic rocks and (b) undeformed ultramafic–mafic plutonic rocks. The high‐Mg ultrabasic/basic rocks have undergone severe low‐grade (greenschist) metamorphism and are characterized by stringer and veinlet structures of talc–tremolite–actinolite schists with alternate layers of serpentinites showing comparatively higher SiO2 (46.1–49.4 wt%), lower MgO (24.6–26.2 wt%), and higher Al2O3 (4.58–7.06 wt%) and CaO (2.72–6.77 wt%) compared to the undeformed ultramafic rocks. The undeformed ultramafic rocks (mainly harzburgite, lherzolite, and olivine websterite) are characterized by globular structures and have lower SiO2 (40–44.1 wt%), higher MgO (30.4–38 wt%) and lower Al2O3 (1.84–4.03 wt%) and CaO (0.16–3.14 wt%). The undeformed mafic rocks (mainly gabbro) occur as small pockets within the undeformed ultramafic rocks as well as independent outcrops. Limited variation in Nb/Th against Nb/Yb along with negative Nb‐Ti anomalies of all the rock types in the multi‐element diagram reveals the significant role of the metasomatized mantle in their genesis. All the rocks show enrichment in light rare earth element and large‐ion lithophile elements compared to heavy rare earth elements and high‐field strength elements. The geochemical characteristics coupled with Ce/Yb versus Ce variation of the rocks of MUC point towards two different sources for their genesis. The high‐Mg ultrabasic/basic rocks are derived from partial melting of metasomatized mantle at shallow depth, while the undeformed ultramafic rocks were formed as a result of asthenospheric upwelling from a greater depth that induced the melting in the overlying lithosphere. Gabbro rocks represent the last and most evolved phase of the complex. Geochemical signatures suggest that the rocks of MUC were formed in a continental arc setting.

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The Central Slave Basement Complex, Part I: its structural topology and autochthonous cover

Cited by 23 publications

References 0 publications

Stacked uppermost mantle layers within the Slave craton of NW Canada as defined by anisotropic seismic discontinuities

Stacked uppermost mantle layers within the Slave craton of NW Canada as defined by anisotropic seismic discontinuities

Lithospheric architecture of the Slave craton, northwest Canada, as determined from an interdisciplinary 3‐D model

Geochemistry of ultramafic–mafic rocks of the Madawara Ultramafic Complex in the southern part of the Bundelkhand Craton, Central Indian Shield: Implications for mantle sources and geodynamic setting

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