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GEOREF RECORD

"Sudbury Breccia" at Whitefish Falls, Ontario; evidence for an impact origin

Andrew C. Parmenter, Christopher B. Lee and Mario Coniglio
"Sudbury Breccia" at Whitefish Falls, Ontario; evidence for an impact origin
Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre (June 2002) 39 (6): 971-982

Abstract

Sudbury breccias are unusual clast-matrix rock bodies formed in abundance around the Sudbury Igneous Complex, the most obvious manifestation of a major impact at Sudbury. At Whitefish Falls, approximately 70 km southwest of Sudbury, similar breccias consisting of clasts of argillite and amphibolite dyke enclosed in a fine-grained matrix of host rock are developed in metamorphosed argillites of the Huronian Supergroup. Pre-brecciation brittle textures in the host argillite and breccia clasts, such as layer-parallel foliation offset by cataclastic fractures, suggest that the host rock was entirely competent prior to brecciation. One composite penetrative foliation and its associated ductile folding were also formed in the argillite host prior to brecciation. Post-brecciation ductile deformation produced a regionally dominant east-west-trending foliation, and two late-stage folding events, and indicate a syn-Penokean age of brecciation. The breccias at Whitefish Falls are enriched in ferromagnesian minerals compared to adjacent, embayed and partially digested, host rock. Flow-foliated breccia matrices surround a highly rounded clast phase. These features are characteristic of impact-related pseudotachylyte, formed during extreme cataclasis and friction melting of the impacted host rock. We propose that these breccias formed by injection of a high-strain, pseudotachylytic melt, triggered by the Sudbury impact event, and focused along a blind superfault, coincident with a post-Penokean high-strain zone.


ISSN: 0008-4077
EISSN: 1480-3313
Coden: CJESAP
Serial Title: Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre
Serial Volume: 39
Serial Issue: 6
Title: "Sudbury Breccia" at Whitefish Falls, Ontario; evidence for an impact origin
Affiliation: University of Waterloo, Department of Earth Sciences, Waterloo, ON, Canada
Pages: 971-982
Published: 200206
Text Language: English
Summary Language: French
Publisher: National Research Council of Canada, Ottawa, ON, Canada
References: 38
Accession Number: 2002-067093
Categories: Structural geologyIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. geol. sketch maps
N46°25'00" - N46°49'60", W81°40'00" - W80°45'00"
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200221
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