Evidence of magmatism and rifting in the southern superior craton from the Temagami geophysical anomaly

The Snow Lake Allochthon is a zone of tectonic interleaving of sedimentary rocks of an inverted marginal basin (Kisseynew Domain) with island-arc and oceanic rocks. It is located in the southeastern part of the exposed internal zone of the Paleoproterozoic Trans-Hudson Orogen in Manitoba, Canada, near the external zone (Superior collision zone or Thompson Belt), which constitutes the local boundary between the Trans-Hudson Orogen and the Archean Superior Craton. The Snow Lake Allochthon formed, was deformed, and was metamorphosed up to high grade at low to medium pressure during the Hudsonian orogeny as a result of the collision of Archean cratons ~1.84-1.77 Ga. Four generations of folds (F1-F4) that formed in at least three successive kinematic frames over a period of more than 30 Ma are described. Isoclinal to transposed southerly verging F1-2 structures are refolded by large, open to tight F3 folds and, locally, by open to tight F4 folds. The axes of the F1-2 folds are parallel or near parallel to the axes of F3 folds, owing to progressive reorientation of the F1-2 axes during south- to southwest-directed tectonic transport, followed by F3 refolding around the previous linear anisotropy. A tectonic model is presented that reconciles the distinct tectono-metamorphic developments in the Snow Lake Allochthon and the adjacent part of the Kisseynew Domain on the one hand, and in the Thompson Belt on the other, during final collision of the Trans-Hudson Orogen with the Superior Craton.

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Timing of Paleoproterozoic granitoid magmatism along the northwestern Superior Province margin: implications for the tectonic evolution of the Thompson Nickel BeltThis article is one of a series of papers published in this Special Issue on the theme of Geochronology in honour of Tom Krogh.

Canadian Journal of Earth Sciences ◽

10.1139/e10-079 ◽

2011 ◽

Vol 48 (2) ◽

pp. 325-346 ◽

Cited By ~ 3

Author(s):

N. Machado ◽

L. M. Heaman ◽

T. E. Krogh ◽

W. Weber ◽

M. T. Corkery

Keyword(s):

Sensu Stricto ◽

Crustal Thickening ◽

Superior Province ◽

Granitoid Magmatism ◽

Continental Block ◽

Granitic Magmatism ◽

Peak Metamorphism ◽

Granite Magmatism ◽

Superior Craton ◽

Superior Margin

The U–Pb geochronology of three granitoid plutons and three granitic pegmatite dykes, largely from the Thompson Nickel Belt located along the northwestern Superior craton margin, was investigated to place constraints on the timing of felsic magmatism associated with closure of the Manikewan Ocean and final continent–continent collision to form the Trans-Hudson Orogen. These data indicate that 1840–1820 Ma granite magmatism along the Superior margin was more active than previously thought and that some magmatism extended beyond the Thompson Nickel Belt sensu stricto, including the 1836 ± 3 Ma Mystery Lake granodiorite, 1822 ± 5 Ma Wintering Lake granodiorite, and the 1825 ± 8 Ma Fox Lake granite located in the Split Lake Block. Granitic pegmatites within the Thompson Nickel Belt were emplaced late in the collisional history in the period 1.79–1.75 Ga and include a 1770 ± 2 Ma dyke exposed at the Thompson pit, a 1767 ± 6 Ma dyke at the Pipe Pit, and a 1786 ± 2 Ma dyke located at Paint Lake. The final stage of crustal amalgamation in the eastern Trans-Hudson Orogen involved Superior Province crustal thickening and partial melting forming 1.84–1.82 Ga granite magmas and then final collision at ∼1.8 Ga between the Superior Province and a continental block to the west consisting of the previously amalgamated Sask and Hearne cratons. Heating of the Superior craton margin and granitic magmatism continued past peak metamorphism (1790–1750 Ma); this thermal event is represented by the emplacement of numerous late pegmatite dykes and evidenced by cooling dates recorded by metamorphic minerals (e.g., titanite) in reworked Archean gneisses and Proterozoic intrusions.

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The gravity field over the Ungava Bay region from satellite altimetry and new land-based data: implications for the geology of the area

Canadian Journal of Earth Sciences ◽

10.1139/e98-085 ◽

1999 ◽

Vol 36 (1) ◽

pp. 75-89 ◽

Cited By ~ 4

Author(s):

Hamid Telmat ◽

Jean-Claude Mareschal ◽

Clément Gariépy

Keyword(s):

Satellite Altimetry ◽

Gravity Data ◽

Gravity Anomalies ◽

Gravity Models ◽

Crustal Thickening ◽

Seismic Line ◽

Crustal Thinning ◽

Gravity Measurements ◽

George River ◽

Superior Craton

Gravity data were obtained along two transects on the southern coast of Ungava Bay, which provide continuous gravity coverage between Leaf Bay and George River. The transects and the derived gravity profiles extend from the Superior craton to the Rae Province across the New Quebec Orogen (NQO). Interpretation of the transect along the southwestern coast of Ungava Bay suggests crustal thickening beneath the NQO and crustal thinning beneath the Kuujjuaq Terrane, east of the NQO. Two alternative interpretations are proposed for the transect along the southeastern coast of the bay. The first model shows crustal thickening beneath the George River Shear Zone (GRSZ) and two shallow bodies correlated with the northern extensions of the GRSZ and the De Pas batholith. The second model shows constant crustal thickness and bodies more deeply rooted than in the first model. The gravity models are consistent with the easterly dipping reflections imaged along a Lithoprobe seismic line crossing Ungava Bay and suggest westward thrusting of the Rae Province over the NQO. Because no gravity data have been collected in Ungava Bay, satellite altimetry data have been used as a means to fill the gap in data collected at sea. The satellite-derived gravity data and standard Bouguer gravity data were combined in a composite map for the Ungava Bay region. The new land-based gravity measurements were used to verify and calibrate the satellite data and to ensure that offshore gravity anomalies merge with those determined by the land surveys in a reasonable fashion. Three parallel east-west gravity profiles were extracted: across Ungava Bay (59.9°N), on the southern shore of the bay (58.5°N), and onshore ~200 km south of Ungava Bay (57.1°N). The gravity signature of some major structures, such as the GRSZ, can be identified on each profile.

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The Coulon deposit: quantifying alteration in volcanogenic massive sulphide systems modified by amphibolite-facies metamorphism

Canadian Journal of Earth Sciences ◽

10.1139/cjes-2016-0017 ◽

2016 ◽

Vol 53 (12) ◽

pp. 1443-1457 ◽

Cited By ~ 2

Author(s):

Lucie Mathieu ◽

Rose-Anne Bouchard ◽

Vital Pearson ◽

Réal Daigneault

Keyword(s):

Mass Balance ◽

Massive Sulphide ◽

Amphibolite Facies ◽

High Grade ◽

Bay Area ◽

Volcanogenic Massive Sulphide ◽

High Grade Metamorphism ◽

And Performance ◽

Superior Craton ◽

Ore Zones

The Coulon deposit is a volcanogenic massive sulphide (VMS) system in the James Bay area, Superior craton, Quebec, that was metamorphosed to amphibolite-facies conditions. The chemistry and mineralogy of the VMS-related alteration halo proximal to the mineralized sulphide lenses are investigated, using samples collected in the field and 5583 chemical analyses provided by Osisko Ltd. Alteration is quantified using mass balance and normative calculations, and the application and performance of these methods in an exploration context are investigated. In VMS systems, altered rocks proximal to the ore zones are characterized by multi-element metasomatism, which is best quantified by mass balance methods that have been successfully applied in the study area. However, mass balance calculations necessitate the documentation of a precursor, which is not always possible in an exploration context; therefore, an alternative method (i.e., alteration indices) was also evaluated. In most VMS systems, proximal alteration is characterized by chlorite (chloritization), muscovite (sericitization), and quartz (silicification), while at the Coulon deposit, altered rocks contain mostly cordierite, biotite, sillimanite, and quartz. Alteration indices were calculated using observed and normative minerals, and provide satisfactory results similar to those obtained with mass balance calculations. Using these results, recommendations are made to estimate the intensity of alteration in the core shack using the proportions of observed minerals. Alteration indices are sensitive to the composition of precursors; and because of high-grade metamorphism, chloritization and sericitization are not precisely quantified. Recognizing these limitations is essential to successful quantification of alteration in areas metamorphosed to high-grade conditions.

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Lithospheric structure of the North American Craton constrained by full waveform inversion

10.5194/egusphere-egu21-14319 ◽

2021 ◽

Author(s):

Tong Zhou ◽

Min Chen ◽

Ziyi Xi ◽

Jiaqi Li

Keyword(s):

Shear Wave ◽

Wave Speed ◽

Waveform Inversion ◽

Continental Lithosphere ◽

Shear Wave Speed ◽

The North ◽

Full Waveform ◽

Radial Anisotropy ◽

North American Craton ◽

Superior Craton

Cratonic lithosphere is believed to be rigid and less deformed during a long period of time. However, the detailed structure of Cratons may bring information of the complex formation and assemblage process of the continental lithosphere. Here, we present the seismic radial anisotropic structure of the North American Craton (NAC) constrained by a regional full-waveform inversion (FWI) with 465,422 high-quality frequency-dependent travel time misfit measurements with the shortest period of 15 s from both the body wave and surface wave recordings of 5,120 stations and 160 earthquakes located in the contiguous U.S and surrounding regions. Started from an initial model constructed by combining US.2016 and Crust1.0 in the crust and S40RTS (isotropic) in the mantle, we are able to have the optimized crustal structure in terms of initial waveform similarity and get rid of existing features from other radially anisotropic mantle models.Our new model reveals the NAC lithosphere with about +2% voigt shear wave speed anomaly and an average thickness of 200&#8211;250 km beneath the Superior Craton, and becomes thinner towards the eastern, the southern, and the southwestern margins with a thickness decreased to 100&#8211;150 km. The radial anisotropy manifests a layer of higher horizontal shear wave speed VSH&#160;(&#958;=VSH2/VSV2>1) beneath the core of Superior Craton down to around 160 km, where the higher vertical shear wave speed VSV (&#958;<1) is observed beneath 160 km. Such radial anisotropy layering is also observed in the margin of continental lithosphere but with shallower depth. The radial anisotropic layer matches the receiver function results of mid-lithosphere discontinuities of the Craton cores, and the lithosphere conductivity result.&#160;The radial anisotropy layering observation confirms the two-layered lithosphere structure of the NAC, where the upper layer likely represents the original radial anisotropy fabric related to the cooling of the craton core, while the lower layer might be related to the tectonic processes more recently, e.g., accretion .&#160;The lithospheric thinning beneath the NAC margins indicates the deformation of the lithosphere and is likely controlled by the large-scale mantle convection, therefore relates to the further modification process of the NAC.

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