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Deep into the Chibougamau area, Abitibi Subprovince: structure of a Neoarchean crust revealed by seismic reflection profiling
  • +4
  • Lucie Mathieu,
  • David B Snyder,
  • Pierre Bedeaux,
  • Saeid Cheraghi,
  • Bruno Lafrance,
  • Phil Thurston,
  • Ross Sherlock
Lucie Mathieu
UQAC - Université du Québec à Chicoutimi

Corresponding Author:[email protected]

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David B Snyder
Laurentian University
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Pierre Bedeaux
UQAC
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Saeid Cheraghi
Laurentian University
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Bruno Lafrance
Laurentian University
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Phil Thurston
Laurentian University
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Ross Sherlock
Laurentian University
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Abstract

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Copper-Au magmatic-hydrothermal systems dominate in the Chibougamau area of the Neoarchean Abitibi Subprovince, whereas orogenic gold mineralization is more common in the rest of the Abitibi. Understanding differences in the metal endowment of parts of the Abitibi Subprovince requires insights into the geodynamic evolution of the Chibougamau area. This is addressed by imaging the crust using seismic reflection data acquired as part of the Metal Earth project. Seismic reflection imaged shallowly south-dipping structures in the upper-crust (e.g., deep extension of the Barlow fault) and a northward-dipping mid-crust region. The upper part of the mid-crust zone is characterized by multiple reflectors that are likely faults superimposed on a major lithological boundary. These structures were likely acquired at ca 2.70 Ga during terrane accretion prior to carbonization. Combining the seismic data with known stratigraphic, structural and magmatic records, we propose that the study area was initially a normal (i.e., thick) Archean oceanic crust that formed at or before 2.9 Ga and that evolved through terrane imbrication at 2.73 Ga or before. This caused rapid burial of mafic rocks followed by devolatilization and partial melting of hydrated mafic rocks to produce tonalite magmas that may have mixed with mantle-derived melts to produce the diorite-tonalite suite associated with Cu-Au magmatic-hydrothermal mineralization.