Magnetic fabric constraints on friction melt flow regimes and ore emplacement direction within the South Range Breccia Belt, Sudbury Impact Structure

Scott, Ronald G.; Spray, John G.

doi:10.1016/s0040-1951(99)00124-9

Cited by 24 publications

(30 citation statements)

References 29 publications

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“…This corroborates other petrographic and structural studies documenting evidence for a pervasive greenschist-metamorphic overprint of post-impact lithologies in the South Range, notably offset dikes and pseudotachylitic rocks (summary in Riller 2005). The documented metamorphic overprint of these lithologies is at variance with the interpretation of magnetic fabrics as primary fabrics formed by flow of quartz-diorite melt in Offset Dikes in Huronian rocks underlying the South Range SIC (Scott and Spray 1999).…”

Section: Mineral Fabrics Of the Worthington Dikesupporting

confidence: 89%

“…Both processes would have occurred within minutes after impact (Melosh 1989). By contrast, magnetic fabric studies of the Worthington and Copper Cliff Offset Dikes seem to indicate that the respective melts were emplaced in transfer fault zones separating gravitationally collapsing wall segments during the modification of the transient crater (Scott and Spray 1999: Scott and Benn 2002. Collectively, these modes of dike formation likely require turbulent flow of quartz diorite melt.…”

Section: Introductionmentioning

confidence: 91%

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Differentiation and emplacement of the Worthington Offset Dike of the Sudbury impact structure, Ontario

Hecht

Wittek

Riller

et al. 2008

Meteorit & Planetary Scien

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Abstract-The Offset Dikes of the 1.85 Ga Sudbury Igneous Complex (SIC) constitute a key topic in understanding the chemical evolution of the impact melt, its mineralization, and the interplay between melt migration and impact-induced deformation. The origin of the melt rocks in Offset Dikes as well as mode and timing of their emplacement are still a matter of debate. Like many other offset dikes, the Worthington is composed of an early emplaced texturally rather homogeneous quartz-diorite (QD) phase at the dike margin, and an inclusion-and sulfide-rich quartz-diorite (IQD) phase emplaced later and mostly in the centre of the dike. The chemical heterogeneity within and between QD and IQD is mainly attributed to variable assimilation of host rocks at the base of the SIC, prior to emplacement of the melt into the dike. Petrological data suggest that the parental magma of the Worthington Dike mainly developed during the pre-liquidus temperature interval of the thermal evolution of the impact melt sheet (>1200 °C). Based on thermal models of the cooling history of the SIC, the two-stage emplacement of the Worthington Dike occurred likely thousands to about ten thousand years after impact. Structural analysis indicates that an alignment of minerals and host rock fragments within the Worthington Dike was caused by ductile deformation under greenschist-facies metamorphic conditions rather than flow during melt emplacement. It is concluded that the Worthington Offset Dike resulted from crater floor fracturing, possibly driven by late-stage isostatic readjustment of crust underlying the impact structure.

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Section: Mineral Fabrics Of the Worthington Dikesupporting

confidence: 89%

Section: Introductionmentioning

confidence: 91%

Differentiation and emplacement of the Worthington Offset Dike of the Sudbury impact structure, Ontario

Hecht

Wittek

Riller

et al. 2008

Meteorit & Planetary Scien

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“…The biotite grains exhibit a moderate to strong subvertical lineation (Fig. 8b,c), which is coaxial to the orientation of the magnetic lineation as determined from anisotropy of magnetic susceptibility (Ah4S) studies (Scott and Spray, 1999).…”

Section: Mineralogymentioning

confidence: 55%

“…We have suggested previously (Spray, 1997;Scott and Spray, 1999) that the SRBB was formed by high strain-rate (>I d s ) failure of the inner wall of the crater, which slumped into the impact-melt sheet. The thickness of the SRBB requires at least 2.5 km of displacement along a listric "superfault" in order to generate an average pseudotachylyte width of 250 m during high-speed slip (Spray, 1997).…”

Section: Discussionmentioning

confidence: 98%

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The South Range Breccia Belt of the Sudbury Impact Structure: A possible terrace collapse feature

Scott

Spray

2000

Meteorit & Planetary Scien

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Abstract-The South Range Breccia Belt (SRBB) is an arcuate, 45 km long zone of Sudbury Breccia in the South Range of the 1.85 Ga Sudbury Impact Structure. The belt varies in thickness between tens of meters to hundreds of meters and is composed of a polymict assemblage of Huronian Supergroup (2.49-2.20 Ga), Nipissing Diabase (2.2 Ga), and Proterozoic granitoid breccia fragments ranging in size from a few millimeters to tens of meters. The SRBB matrix is composed of a tine-grained (-100 p m ) assemblage of biotite, quartz, and ilmenite, with trace amounts of plagioclase, zircon, titanite, epidote, pyrite, chalcopyrite, pyrrhotite, and occasionally chlorite. The SRBB hosts the Frood-Stobie, Vermilion, and Kirkwood quartz diorite offset dykes, the former being associated with one of the largest Ni-Cu-PGE sulphide deposits in the world.Optical petrography and whole-rock geochemistry concur with previous studies that have suggested that the matrix of the SRBB is derived from comminution and at least partial fiictional melting of the wall rock We suggest that the SRBB was formed by high strain-rate (>1 m/s), gravity-driven seismogenic slip of the inner ring of the Sudbury Impact Structure during postimpact crustal readjustment (crater modification stage). Failure of the hanging wall may have facilitated the injection of bulk SIC melt into the SRBB, along with the Ni-Cu-PGE sulphides of the Frood-Stobie deposit. Postimpact Penokean (1.9-1.7 Ga) tectonism, particularly northwest-directed shearing along the South Range Shear Zone and associated thrust faulting, could account for the present subvertical orientation of the SRBB, and the apparent lack of a connection at depth with the SIC.

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Magnetic Signatures of Terrestrial Meteorite Impact Craters: A Summary

Gilder

Pohl

Eitel

2018

Magnetic Fields in the Solar System

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Magnetic fabric constraints on friction melt flow regimes and ore emplacement direction within the South Range Breccia Belt, Sudbury Impact Structure

Cited by 24 publications

References 29 publications

Differentiation and emplacement of the Worthington Offset Dike of the Sudbury impact structure, Ontario

Differentiation and emplacement of the Worthington Offset Dike of the Sudbury impact structure, Ontario

The South Range Breccia Belt of the Sudbury Impact Structure: A possible terrace collapse feature

Magnetic Signatures of Terrestrial Meteorite Impact Craters: A Summary

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