Publication 87
title
Davis, W.J., A.G. Jones, W. Bleeker, and H, Grütter
Abstract
The late tectonic evolution of the Slave craton involves extensive magmatism, deformation,
and high temperature-low pressure (HT-LP) metamorphism. We argue that the nature of these
tectonic events is difficult to reconcile with early, pre 2.7 Ga development and preservation
of a thick tectosphere, and suggest that crust-mantle coupling and stabilization occured only
late in the orogenic development of the craton. The extent and repetitiveness off the tectonic
reworking documented within the Mesoarchean basement complex of the western Slave, together
with the development of large-volume, extensional mafic magmatism at 2.7 Ga within the basement
complex argue against preservation of a widespread, thick, cool Mesoarchean tectosphere beneath
the western Slave craton prior to Neoarchean tectonism. Broad-scale geological and geophysical
features of the Slave craton, including orientation of an early F1 fold belt, distribution of
ca. 2.63-2.62 Ga plutonic rocks, and the distribution of geochemical , petrological and geophysical
domains within the mantle lithosphere collectively highlight the importance of an NE-SW structural
grain to the craton. These trends are oblique to the earlier, ca. 2.7 Ga north-south trending
boundary between Mesoarchean and Neoarchean crustal domains, and are interpreted to represent a
younger structural feature imposed during northwest or southeast-vergent tectonism at ca 2.64-2.61 Ga.
Extensive plutonism, in part mantle-derived, crustal melting and associated HT-LP metamorphism argue
for widespread mantle heat input to the crust, a feature most consistent with thin (<100 km)
lithosphere at that time. We propose that the mantle lithosphere developed by tectonic imbrication
of one or more slabs subducted beneath the craton at the time of development of the D1 structural
grain, producing the early 2.63-2.62 Ga arc-like plutonic rocks. Subsequent collision (external
to the present craton boundaries) possibly accompanied by partial delamination of some of the
underthrust lithosphere, produced widespread deformation (D2) and granite plutonism throughout
the province at 2.6-2.58 Ga. An implication of this model is that diamond formation in the Slave
should be Neoarchean in age.
Source
Lithos, 71, 575-589, 2002.
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