Deep Into the Chibougamau Area, Abitibi Greenstone Belt: Structure of a Neoarchean Crust Revealed by Seismic Reflection Profiling

Tectonics ◽  
2020 ◽  
Vol 39 (7) ◽  
Author(s):  
Lucie Mathieu ◽  
David B. Snyder ◽  
Pierre Bedeaux ◽  
Saeid Cheraghi ◽  
Bruno Lafrance ◽  
...  
Keyword(s):  
Greenstone Belt ◽  
Seismic Reflection ◽  
Abitibi Greenstone Belt ◽  
Seismic Reflection Profiling

A seismic-reflection-based regional cross section of the southern Abitibi greenstone belt

1995 ◽  
Vol 32 (2) ◽  
pp. 135-148 ◽  
Author(s):  
S. L. Jackson ◽  
A. R. Cruden ◽  
D. White ◽  
B. Milkereit
Keyword(s):  
Greenstone Belt ◽  
Seismic Reflection ◽  
Lower Layer ◽  
Middle Layer ◽  
Shear Zones ◽  
Low Pressure ◽  
Crustal Thickening ◽  
Upper Crust ◽  
Abitibi Greenstone Belt ◽  
Seismic Reflection Profiles

Seismic reflection profiles from the southern Abitibi greenstone belt reveal four first-order subdivisions: (1) Between 0 and ~4.5 s, the upper crust is weakly reflective, with prominent local to laterally extensive reflections. (2) Between ~4 and ~9 s, the crust is strongly and heterogeneously reflective with laterally continuous reflections. (3) From ~9 to ~13 s, the crust is more homogeneously reflective and displays downward decreasing reflectivity. (4) Below ~13 s (Moho?) the upper mantle is weakly reflective. The upper layer may correspond to subgreenschist–greenschist-facies supracrustal rocks cut by low-angle shear zones and intruded by regional tabular batholiths; the middle layer, to ductiley deformed amphibolite-facies gneisses, granitoids, and (or) metasediments; and the lower layer, to more homogeneously deformed granulite-facies rocks. North-dipping, low-angle reflections extending beneath both diverse supracrustal assemblages and regional batholiths may represent structural detachments upon which both the supracrustal assemblages and batholiths were imbricated and translated southward. However, the preservation of regional low-pressure metamorphic rocks and the common para-autochthonous relationships between assemblages suggest that thrust-related vertical separations and the magnitude of crustal thickening were not large. Steeply dipping regional shear zones within the greenstone belt appear to disrupt subhorizontal reflections down to ~15 km and may represent late-tectonic strains, which were progressively concentrated into linear zones during continued north–south shortening. The crustal-scale structure determined from the seismic reflection profiles, combined with surface geology, is compatible with post-2.70 Ga north–south shortening accommodated by south-directed(?) thrusting in a thermally softened mid crust and by upright folding in the upper crust. This scenario is comparable to recently proposed models for the Paleozoic, high-temperature, low-pressure Lachlan fold belt of Australia.

Seismic reflection constraints from Lithoprobe line 29 on the upper crustal structure of the northern Abitibi greenstone belt

1995 ◽  
Vol 32 (2) ◽  
pp. 128-134 ◽  
Author(s):  
Gilles Bellefleur ◽  
Arthur Barnes ◽  
Andrew Calvert ◽  
Claude Hubert ◽  
Marianne Mareschal
Keyword(s):  
Crustal Structure ◽  
Greenstone Belt ◽  
Seismic Reflection ◽  
Volcanic Rocks ◽  
Seismic Profile ◽  
Median Filtering ◽  
Abitibi Greenstone Belt ◽  
Geological Information ◽  
Additional Constraints ◽  
East West

Detailed reprocessing of east–west Lithoprobe seismic reflection line 29 includes cross-dip analysis to improve the continuity of the reflectors and median filtering to attenuate shear wave refractions. The interpretation provides additional constraints on the tectonic models of northern Abitibi, but cannot be used to invalidate either of the two models recently presented for the area. However, the seismic profile defines a large east-dipping faulted contact between the Brouillan tonalite and the volcanic rocks exposed west of the intrusion. The moderate dip of the reflectors and their extensive lateral continuity, combined with geological information, provide evidence for an east-dipping thrust sequence and suggest an allochthonous origin for the Brouillan tonalite. The maximum thickness of the volcanic sequence in the northern Abitibi greenstone belt is 8 km, but could be as low as 4 km if Opatica orthogneisses are considered to underthrust northern Abitibi. The mid-crustal reflections confirm the east–west continuity of south-vergent imbrications also observed on a north–south reflection line (28) through northern and central Abitibi. Breakage and displacement of some mid-crustal reflectors may define a west-to-east thrust sequence of sense opposite to that which thrust the Brouillan pluton over the volcanic rocks.

Southern Abitibi greenstone belt: Archean crustal structure from seismic-reflection profiles

Geology ◽  
1990 ◽  
Vol 18 (11) ◽  
pp. 1086 ◽  
Author(s):  
S. L. Jackson ◽  
R. H. Sutcliffe ◽  
J. N. Ludden ◽  
C. Hubert ◽  
A. G. Green ◽  
...  
Keyword(s):  
Crustal Structure ◽  
Greenstone Belt ◽  
Seismic Reflection ◽  
Abitibi Greenstone Belt ◽  
Seismic Reflection Profiles

The North American Midcontinent Rift beneath Lake Superior from Glimpce seismic reflection profiling

Tectonics ◽  
1989 ◽  
Vol 8 (2) ◽  
pp. 305-332 ◽  
Author(s):  
W. F. Cannon ◽  
Alan G. Green ◽  
D. R. Hutchinson ◽  
Myung Lee ◽  
Bernd Milkereit ◽  
...  
Keyword(s):  
North American ◽  
Seismic Reflection ◽  
Lake Superior ◽  
Midcontinent Rift ◽  
The North ◽  
Seismic Reflection Profiling

Archean terrane docking: upper crust collision tectonics, Abitibi greenstone belt, Quebec, Canada

1996 ◽  
Vol 265 (1-2) ◽  
pp. 127-150 ◽  
Author(s):  
W.U Mueller ◽  
R Daigneault ◽  
J.K Mortensen ◽  
E.H Chown
Keyword(s):  
Greenstone Belt ◽  
Upper Crust ◽  
Abitibi Greenstone Belt ◽  
Collision Tectonics

2D-3C high-resolution seismic data from the Abitibi Greenstone Belt, Canada

2009 ◽  
Vol 472 (1-4) ◽  
pp. 226-237 ◽  
Author(s):  
David B. Snyder ◽  
Peter Cary ◽  
Matt Salisbury
Keyword(s):  
High Resolution ◽  
Seismic Data ◽  
Greenstone Belt ◽  
Abitibi Greenstone Belt
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