Publication 157
Crustal and lithospheric scale structures of the Precambrian Superior-Grenville margin
Adetunji, A.Q., I.J. Ferguson, and A.G. Jones
Abstract
The lithosphere beneath the margin of the Archean Superior and Proterozoic Grenville
provinces was investigated with a northwest-southeast oriented, 650-km-long profile of 40
magnetotelluric stations. Dominant geoelectric strike azimuths of N45E and N85E were
defined for the crust and the lithospheric mantle respectively. A 2-D isotropic resistivity model
derived using the crustal strike images resistive Laurentian margin rocks dipping southeast to the
base of the crust, bounded to the northwest by the Grenville Front, and to the southeast by the
Central Metasedimentary Belt Boundary Zone. The observation is in contrast to conductive mid
to lower crust elsewhere in the region. A 2-D isotropic resistivity model determined using the
lithospheric mantle strike azimuth reveals an extremely resistive region in the upper 100 km of
the mantle lithosphere of the northern Grenville Province. The geometry of this body, which
includes a well-defined base and southeast dip, suggests that it is Superior lithosphere. A subvertical
conductor, located approximately 50 km along strike from the Mesozoic Kirkland Lake
and Cobalt kimberlite fields, is interpreted to be due to re-fertilization of an older mantle scar.
The resistivity model includes a horizontal conductor at 160 km depth beneath the southern
Superior Province that is likely the resistivity signature of the lithospheric-asthenospheric
boundary.
Source
Tectonophysics, , 614, 146-169, doi:10.1016/j.tecto.2013.12.008, 2014. [PDF]
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Alan G Jones / 25 March 2014 /
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