Grenville age deformation of the Sudbury impact structure: evidence from magnetic modelling of the Sudbury diabase dyke swarm

Tschirhart, Peter; Morris, Bill

doi:10.1111/j.1365-3121.2011.01056.x

Cited by 17 publications

(10 citation statements)

References 18 publications

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“…1D). Formation of the Basin is attributed to deformation during the 1.7-1.6 Ga Mazatzal-Labradorian Orogeny (Bailey et al 2004) and the 1.2-1.0 Ga Grenville Orogeny (Card 1984;Tschirhart and Morris 2012). The SIC formed by melting of its immediate host rocks (Grieve et al 1991;Dickin et al 1999;Therriault et al 2002;Zieg and Marsh 2005).…”

Section: Sudbury Impact Structure and Offset Dikesmentioning

confidence: 99%

Modeling the geochemical evolution of impact melts in terrestrial impact basins: Vredefort granophyre dikes and Sudbury offset dikes

Huber

Kovaleva

Riller

2020

Meteorit & Planetary Scien

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The Vredefort impact structure, South Africa, is comparable to the Sudbury impact structure, Canada, in size, age, and target rock composition. Both impact structures feature impact melt dikes. The melt sheet of the Sudbury impact (Sudbury Igneous Complex; SIC) is genetically linked to the Sudbury offset dikes in the underlying target rock. At Vredefort, the melt sheet was eroded so that only the granophyre dikes retain compositional melt sheet characteristics. XRF analyses of 43 samples from four granophyre dikes are similar to previous studies, but identify an anomalous mafic phase within one of the dikes. The results from the Vredefort granophyre dikes are compared to the Sudbury offset dikes and shown to follow similar geochemical trends, controlled by crystallization of feldspar and pyroxene. The mafic granophyre phase is compositionally remarkably similar to the offset dike compositions. The program Rhyolite-MELTS was used to test possible melt sheet compositions. Modeling results are broadly consistent with the overall chemical and mineral composition of the dikes. Modeling is consistent with offset dikes being derived from the basal mafic layer of the SIC, and the granophyre dikes being derived from alkalidepleted bulk continental crust. For all modeled compositions, crystallization primarily occurred at temperatures between 1150°C and 1000°C. The emplacement of the felsic granophyre dikes from a homogenized crustal melt suggests emplacement within tens of years after the impact event. The presence of the mafic phase in one of the granophyre dikes is explained by its emplacement following some differentiation of the Vredefort melt sheet.

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Section: Sudbury Impact Structure and Offset Dikesmentioning

confidence: 99%

Modeling the geochemical evolution of impact melts in terrestrial impact basins: Vredefort granophyre dikes and Sudbury offset dikes

Huber

Kovaleva

Riller

2020

Meteorit & Planetary Scien

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“…In the absence of any direct evidence for magnetic remanence, all of our models are based on magnetic susceptibility fluctuations. We recognize that, if present, magnetic remanence could affect the dips of our output models (Tschirhart and Morris 2011). The depth to top can only have a small limited variation as overburden thicknesses in the region are overall less than 10 m (Thomas 1981).…”

Section: Geologic Settingmentioning

confidence: 97%

3D geophysical inversions of the north‐east Amer Belt and their relationship to the geologic structure

Tschirhart

Morris

Jefferson

et al. 2012

Geophysical Prospecting

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The Amer Lake area is located within the Churchill Structural Province in the Kivalliq Region of Nunavut, approximately 160 km north‐west of Baker Lake. Two distinct geophysical‐geological entities are structurally intercalated: an Archean mixed granitoid gneiss – metasedimentary‐metavolcanic basement and the unconformably overlying Paleoproterozoic Amer Group metasediments. From east of Amer Lake stretching toward the south‐west, these two entities form the Amer fold and thrust belt. At the north‐east end of this belt, high‐resolution aeromagnetic data define a distinctive oval shape that has been interpreted as a south‐west trending doubly plunging synform. The outcrop within the interior of this structure is sparse resulting in limited structural data and speculative geological interpretations with multiple geometries possible. The high‐resolution aeromagnetic data compiled through an industry‐government consortium and newly acquired detailed gravity profiles were modelled to provide constraints on the geometry of this synform. We document a geophysical‐geological feedback process whereby the available geological and geophysical data were used to derive constraints on inversion models for the synform. Starting with available limited litho‐structural data the presence of a double plunging synform was directly inferred from the aeromagnetic data. Segments of the aeromagnetic data have 2D morphology and so can be modelled using a simple parametric 2D dipping slab inversion approach. Models of profiles extracted from the aeromagnetic data were used to provide preliminary dip and magnetic susceptibility constraints for the Three Lakes mudstone with iron formation and the Five Mile Lake basalt. Landsat imagery outlined the spatial limits of the stratigraphically underlying, non‐magnetic Ayagaq quartzite. Incorporating these outputs as bounds in the input / reference model for a UBC‐GIF 3D magnetic inversion helped to accentuate the geological structure in the output mesh: an enhanced inversion that incorporates both geological and geophysical constraints. The validity of the resulting inversion model was tested by computing 2D forward models of the gravity profile data. The inversion model generated by this study emphasizes the importance of integrating information from as many knowledge sources as one can find. More trust can be placed on forward and inversion models where there is agreement among all data sets and a coherency of structural style.

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“…) and the 1.2–1.0 Ga Grenville Orogeny (Card et al. ; Tschirhart and Morris ). Morphologically, the synformal Main Mass SIC of the Sudbury Basin, which measures 63 km × 25 km at surface, is divided into three ranges, the South Range, the North Range, and the East Range (Fig.…”

Section: Geological Settingmentioning

confidence: 99%

“…1). Formation of the Basin is attributed to deformation during the 1.7-1.6 Ga Mazatzal-Labradorian Orogeny (Bailey et al 2004) and the 1.2-1.0 Ga Grenville Orogeny (Card et al 1984;Tschirhart and Morris 2012). Morphologically, the synformal Main Mass SIC of the Sudbury Basin, which measures 63 km 9 25 km at surface, is divided into three ranges, the South Range, the North Range, and the East Range (Fig.…”

Section: Geological Settingmentioning

confidence: 99%

Thermo‐mechanical interaction of a large impact melt sheet with adjacent target rock, Sudbury impact structure, Canada

Göllner

Wüstemann

Bendschneider

et al. 2019

Meteorit & Planetary Scien

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The 1.85 Ga Sudbury Igneous Complex (SIC) and its thermal aureole are unique on Earth with regard to unraveling the effects of a large impact melt sheet on adjacent target rocks. Notably, the formation of Footwall Breccia, lining the basal SIC, remains controversial and has been attributed to impact, cratering, and postcratering processes. Based on detailed field mapping and microstructural analysis of thermal aureole rocks, we identified three distinct zones characterized by static recrystallization, incipient melting, and crystallization textures. The temperature gradient in the thermal aureole increases toward the SIC and culminates in a zone of partial melting, which correlates spatially with the Footwall Breccia. We therefore conclude that assimilation of target rock into initially superheated impact melt and simultaneous deformation after cratering strongly contributed to breccia formation. Estimated melt fractions of the Footwall Breccia amount to 80 vol% and attest to an extreme loss in mechanical strength and, thus, high mobility of the Breccia during assimilation. Transport of highly mobile Footwall Breccia material into the overlying Sublayer Norite of the SIC and vice versa can be attributed to Raleigh–Taylor instability of both units, long‐term crater modification caused by viscous relaxation of crust underlying the Sudbury impact structure, or both.

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Grenville age deformation of the Sudbury impact structure: evidence from magnetic modelling of the Sudbury diabase dyke swarm

Cited by 17 publications

References 18 publications

Modeling the geochemical evolution of impact melts in terrestrial impact basins: Vredefort granophyre dikes and Sudbury offset dikes

Modeling the geochemical evolution of impact melts in terrestrial impact basins: Vredefort granophyre dikes and Sudbury offset dikes

3D geophysical inversions of the north‐east Amer Belt and their relationship to the geologic structure

Thermo‐mechanical interaction of a large impact melt sheet with adjacent target rock, Sudbury impact structure, Canada

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