Vitric Compositions in the Onaping Formation and Their Relationship to the Sudbury Igneous Complex, Sudbury Structure

The 1.85 Ga Sudbury impact structure is considered a remnant of a peak-ring or multi-ring basin with an estimated original diameter of 150 to 200 km. The Offset Dikes are radial and concentric dikes around the Sudbury Igneous Complex (SIC) and are composed of the so-called inclusion-rich Quartz Diorite (IQD) and inclusion-poor Quartz Diorite (QD), and in some Offset Dikes, Metabreccia (MTBX). We carried out a detailed field and analytical investigation of MTBX from the Parkin Offset Dike in the North Range of the Sudbury structure. Our observations suggest that MTBX represents impact breccia that originally formed underneath the Main Mass of the SIC and that was subsequently contact-metamorphosed and entrained during the emplacement of the Parkin Offset Dike. The MTBX bears no resemblance to the QD and IQD in which it is hosted, but it does share many similarities with Footwall Breccia (FWBX), suggesting that the two shared a similar initial origin. A genetic relationship between MTBX and FWBX is also supported by whole rock geochemical analyses.

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Geoscience impact: a synthesis of studies of the Sudbury Structure

Canadian Journal of Earth Sciences ◽

10.1139/e99-062 ◽

2000 ◽

Vol 37 (2-3) ◽

pp. 477-501 ◽

Cited By ~ 22

Author(s):

D E Boerner ◽

B Milkereit ◽

A Davidson

Keyword(s):

Three Dimensional ◽

Timing Constraints ◽

Igneous Complex ◽

Crustal Rocks ◽

Sudbury Igneous Complex ◽

Sudbury Structure ◽

Genetic Interpretation ◽

History Of ◽

Post Impact ◽

Proper Context

Geophysical probing results are synthesized into a three-dimensional framework necessary for understanding the genesis of the Sudbury Structure, based primarily on seismic reflection results centred on the Sudbury Igneous Complex. Remnants of crustal melting from a catastrophic meteorite impact are superimposed on the juxtaposition of mid-crustal rocks exhumed during the Archean against deformed Paleoproterozoic sedimentary rocks. Sedimentation, metamorphism, deformation, and metasomatic overprints are all part of the post-impact history of Sudbury and tend to dominate the geophysical response of the structure. Pre-impact deformation, although certainly preserved in some aspects of Sudbury geology, is not clearly expressed in the geophysical data, nor are any elements of impact-induced deformation. Geophysical views of the Sudbury Igneous Complex are thus somewhat biased in representing mostly the post-impact, but pre-Grenvillian history of the region, with the exception of igneous events. Establishing the proper context for integrating these geophysical results in the genetic interpretation of the Sudbury Structure depends crucially upon timing constraints.

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Geophysical evidence for a pre-impact Sudbury dome, southern Superior Province, Canada

Canadian Journal of Earth Sciences ◽

10.1139/e04-097 ◽

2005 ◽

Vol 42 (1) ◽

pp. 1-9 ◽

Cited By ~ 2

Author(s):

Stephen A Prevec ◽

Duncan R Cowan ◽

Gordon RJ Cooper

Keyword(s):

Thermal Regime ◽

Superior Province ◽

Geochronological Data ◽

Subsequent Evolution ◽

Igneous Complex ◽

Sudbury Igneous Complex ◽

Gneiss Complex ◽

Sudbury Structure ◽

Abitibi Subprovince

New filtering of aeromagnetic images of the Sudbury area indicates the existence of a large, elliptical feature that appears to underlie the deformed Sudbury Structure in the region of the exposed Levack Gneiss Complex, such that the two features have long axes which are significantly orthogonal to one another. A northsouth-oriented ellipse appears to be crosscut by that of the Sudbury Structure and does not correspond to known local lithological or structural trends. The magnetic images, combined with existing tectonic, petrological, geothermometric and geobarometric, and geochronological data, are used to suggest the existence of a pre-impact crustal dome in the southernmost Abitibi subprovince, probably related to ca. 2450 Ma rifting and magmatism in the area. This is consistent with existing petrological and tectonic evidence from a variety of sources. Although the doming is itself unrelated to the ca. 1850 Ma Sudbury event, it may have affected the thermal regime existing at the time of impact, which would have profound implications for the subsequent evolution of the Sudbury Igneous Complex.

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Timing constraints on deformation history of the Sudbury Impact Structure

Canadian Journal of Earth Sciences ◽

10.1139/e94-147 ◽

1994 ◽

Vol 31 (11) ◽

pp. 1654-1660 ◽

Cited By ~ 15

Author(s):

Jianjun Wu ◽

Bernd Milkereit ◽

David Boerner

Keyword(s):

Timing Constraints ◽

Impact Structure ◽

Relative Timing ◽

Deformation History ◽

Initial Shape ◽

Igneous Complex ◽

Sudbury Igneous Complex ◽

Sudbury Structure ◽

History Of ◽

Seismic Images

Herein, we present new high-resolution seismic images of the Sudbury Impact Structure, acquired across the Sudbury Igneous Complex and its environs, which provide evidence for the relative timing of the deformation events that reshaped the initial Sudbury Structure. The seismic images show that the lower unit of the Sudbury basinal fill sediments, the Onwatin argillite, is penetrated by a set of blind, imbricated thrusts, whereas the overlying Chelmsford turbidites are unaffected by faulting. We interpret this observation to mean that the deposition of the Chelmsford sediments postdates the latest major deformation of the Sudbury Structure, suggesting that the uniform paleocurrent trends observed in the Chelmsford turbidites are not related to the initial shape of the Sudbury Structure.

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