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Fracturing, thermal evolution and geophysical signature of the crater floor of a large impact structure; the case of the Sudbury Structure, Canada

B. Milkereit, N. Artemieva and H. Ugalde
Fracturing, thermal evolution and geophysical signature of the crater floor of a large impact structure; the case of the Sudbury Structure, Canada (in Large meteorite impacts and planetary evolution IV, Roger L. Gibson (editor) and Wolf Uwe Reimold (editor))
Special Paper - Geological Society of America (September 2010) 465: 115-131

Abstract

Impact modeling and post-impact cooling studies predict a unique fracture and post-impact temperature distribution within the crater floor of large meteorite impact structures. The integration of numerical modeling results and their application to the observed geophysical and current topographic data provides new insights into the early evolution of the deeply eroded Sudbury Structure. The modeling shows a maximum depth of melting of 30-40 km (depending on impact angle and impact velocity). However, melt from upper target layers (< 10 km) is mainly ejected during the excavation stage of crater formation, and the remaining melt is strongly biased to melt derived from lower crustal material. Two-dimensional thermal evolution modeling with various granophyre/norite thickness ratios shows that irrespective of the granophyre/norite thickness ratio, the hottest part of the Sudbury Igneous Complex (SIC) was near the crater center at the melt-pool bottom and within the crater floor, which supports precipitation of sulfides toward the crater floor. The 2D cooling models give compelling evidence for longevity of melt at the bottom of the SIC and partial remelting of the crater floor. The numerical model results are compared with observed topographic, seismic and magnetic data and provide important constraints on their interpretation. A unique slow cooling history is manifested in the broad magnetic signature of the SIC and the adjacent crater floor, and its pronounced remanent magnetization. The vast damage zone and the complex fracture pattern predicted for the crater floor is well preserved in the new high-resolution topographic data for the Sudbury Structure. These regional topographic data allow the distinction between inside-basin fabric (radial topographic lineaments) and crater-floor topographic fabric (radial and contact parallel lineaments), which corroborates the numerical modeling results of radial and concentric faults propagating up to tens of kilometers from the crater center.


ISSN: 0072-1077
EISSN: 2331-219X
Coden: GSAPAZ
Serial Title: Special Paper - Geological Society of America
Serial Volume: 465
Title: Fracturing, thermal evolution and geophysical signature of the crater floor of a large impact structure; the case of the Sudbury Structure, Canada
Title: Large meteorite impacts and planetary evolution IV
Author(s): Milkereit, B.Artemieva, N.Ugalde, H.
Author(s): Gibson, Roger L.editor
Author(s): Reimold, Wolf Uweeditor
Affiliation: University of Toronto, Department of Physics, Toronto, ON, Canada
Affiliation: University of the Witwatersrand, School of Geosciences, Johannesburg, South Africa
Pages: 115-131
Published: 201009
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 74
Accession Number: 2011-013821
Categories: Structural geologyGeomorphology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Includes appendices
Illustration Description: illus. incl. 1 table, geol. sketch maps
N46°25'00" - N46°49'60", W81°40'00" - W80°45'00"
Secondary Affiliation: Leibniz Institute at Humbaldt University Berlin, DEU, GermanyPlanetary Science Institute, USA, United StatesMcMaster University, CAN, Canada
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201109
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