Variation in plagioclase clouding intensity in Matachewan dykes: evidence for the exhumation history of the northern margin of the Sudbury Igneous Complex

2002 ◽  
Vol 39 (6) ◽  
pp. 933-942 ◽  
Author(s):  
J P Siddorn ◽  
H C Halls
Keyword(s):  
Impact Crater ◽  
Regional Metamorphism ◽  
Thin Sections ◽  
Igneous Complex ◽  
Northern Margin ◽  
Sudbury Igneous Complex ◽  
Gneiss Complex ◽  
History Of ◽  
Archean Basement ◽  
Exhumation History

Early Proterozoic Matachewan mafic dykes that cut the Archean Cartier granite – Levack Gneiss Complex north of the Sudbury Igneous Complex (SIC), Canada, are generally metamorphosed to lower amphibolite facies but exhibit locally unaltered plagioclase. These plagioclase feldspars display a clouding similar to that found in the same swarm in the vicinity of the Kapuskasing uplift, about 200 km to the northwest, where the clouding intensity is due to magnetite exsolution and displays a positive correlation with the depth of dyke emplacement. In the Sudbury area, the clouding intensity, obtained by image analysis of thin sections, increases away from the SIC, opposite to the direction of increasing regional metamorphism in the Archean basement. This suggests that the Levack Gneiss Complex north of the SIC was exhumed prior to the intrusion of 2.47 Ga Matachewan dykes and therefore predates the formation of the SIC and associated impact event. The southward tilting of the crust inferred from the plagioclase-clouding data appears to have involved uplift along the Benny Deformation Zone, but the exact age of this deformation is unknown. It may be associated with the 1.8–1.9 Penokean Orogen, 1.85 Ga Sudbury impact crater, or 2.2–2.4 Ga Blezardian Orogen.

High-temperature brine in chalcopyrite-rich quartz vein 40 km southwest of Sudbury, Ontario

2011 ◽  
Vol 48 (10) ◽  
pp. 1369-1385 ◽  
Author(s):  
Eva S. Schandl ◽  
Michael P. Gorton ◽  
Colin J. Bray
Keyword(s):  
High Temperature ◽  
Fluid Inclusion ◽  
Fluid Inclusions ◽  
Minimum Temperature ◽  
Tectonic Evolution ◽  
Quartz Vein ◽  
Regional Metamorphism ◽  
Dissolved Metals ◽  
Igneous Complex ◽  
Sudbury Igneous Complex

The Lac Panache (Nipissing) gabbro intrudes Huronian metasediments ca. 40 km southwest of the Sudbury Igneous Complex. The gabbro contains disseminated sulfides and is in contact with a chalcopyrite-rich quartz vein that crystallized from highly saline fluids (46.8 ± 3 equivalent wt.% NaCl) at a minimum temperature of 420 ± 27 °C. Chloride and carbonate inclusions in opened fluid inclusion cavities in the vein suggest that the brine contained dissolved metals (in addition to NaCl), such as Fe, Cu, Mn, and Co. The weakly altered quartz vein postdated regional metamorphism and was probably contemporaneous with the 1.7 Ga felsic magmatism and attendant albite alteration in the area. Cl-rich scapolite in the gabbro and highly saline fluid inclusions in the quartz vein suggest the existence of circulating hot brine throughout the tectonic evolution of the region. The 2.2 Ga old gabbro contains an abundance of Cl-rich scapolite intergrown with pyrrhotite and chalcopyrite that formed during the early hydrothermal (deuteric) alteration of the gabbro.

Geoscience impact: a synthesis of studies of the Sudbury Structure

2000 ◽  
Vol 37 (2-3) ◽  
pp. 477-501 ◽  
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.

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

2005 ◽  
Vol 42 (1) ◽  
pp. 1-9 ◽  
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 north–south-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.

Timing constraints on deformation history of the Sudbury Impact Structure

1994 ◽  
Vol 31 (11) ◽  
pp. 1654-1660 ◽  
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.

Some early history of replica techniques for electron microscopy

1992 ◽  
Vol 50 (2) ◽  
pp. 1076-1077
Author(s):  
Robert M. Fisher
Keyword(s):  
Thin Film ◽  
Electron Microscopy ◽  
Optical Microscope ◽  
Early History ◽  
Bulk Materials ◽  
Thin Sections ◽  
Transmission Electron ◽  
Reflected Light ◽  
History Of ◽  
Electron Microscopes

By 1940, a half dozen or so commercial or home-built transmission electron microscopes were in use for studies of the ultrastructure of matter. These operated at 30-60 kV and most pioneering microscopists were preoccupied with their search for electron transparent substrates to support dispersions of particulates or bacteria for TEM examination and did not contemplate studies of bulk materials. Metallurgist H. Mahl and other physical scientists, accustomed to examining etched, deformed or machined specimens by reflected light in the optical microscope, were also highly motivated to capitalize on the superior resolution of the electron microscope. Mahl originated several methods of preparing thin oxide or lacquer impressions of surfaces that were transparent in his 50 kV TEM. The utility of replication was recognized immediately and many variations on the theme, including two-step negative-positive replicas, soon appeared. Intense development of replica techniques slowed after 1955 but important advances still occur. The availability of 100 kV instruments, advent of thin film methods for metals and ceramics and microtoming of thin sections for biological specimens largely eliminated any need to resort to replicas.

Surficial geochemical and mineralogical signatures of Ni-Cu-PGE deposits in glaciated terrain: examples from the South Range of the Sudbury Igneous Complex, Ontario, Canada

2021 ◽  
pp. 104301
Author(s):  
Sarah Hashmi ◽  
Matthew I. Leybourne ◽  
Daniel Layton-Matthews ◽  
Stewart Hamilton ◽  
M. Beth McClenaghan ◽  
...  
Keyword(s):  
The South ◽  
Igneous Complex ◽  
Sudbury Igneous Complex
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