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<div>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.</div>