Proposed Title 1: - Queen's University

a ca. 1.85-1.83 Ga event associated with a northwest subduction that reactivated an earlier
northwest-dipping suture beneath the La Ronge-Lynn Lake arc. The 1848±5 Ma main
breccia-related U 4 uranium mineralization could be related to fault reactivation during the
ca. 1.85-1.83 Ga event in the Trans-Hudson Orogen.
Southeastward underthrusting of the Rae-Hearne foreland under the Superior
hinterland during the ca. 1.83-1.81 Ma terminal collision of the Trans-Hudson Orogen
(Ansdell and Yang 1995; Ansdell et al., 1999) is interpreted to have caused intracratonic
deformation and significant extension in the Rae back-arc and formation of the 1820 Ma
successor Martin Lake Basin (Mazimhaka and Hendry, 1985), which developed along lines
of pre-existing tectonic weakness (Fig. 2.13F). The plate-scale tectonic setting of this basin
is more compatible with an extensional rift regime, which is consistent with geodynamic
models that suggest subduction initiation followed by rapid back-arc extension and basin
formation (McKenzie, 1978; Clendenin et al., 1988). Ashton et al. (2009b) suggested that
brittle–ductile to brittle trans-tensional faulting at the junction of the Black Bay (Bergeron,
2001, 2002) and Saint Louis faults (Fig. 2.2) created a small pull-apart basin into which the
Martin Lake Basin was deposited. The Martin Lake Basin is associated with extrusion of
mantle-affinity alkaline to sub-alkaline mafic dikes at 1818±4 Ma (Morelli et al., 2009).
Magma ascended during extensional reactivation of deep fault zones, which act as conduit
for intrusion of the mafic dikes (Fig. 2.13F). Magmatic-hydrothermal degassing through
preexisting fractures and joints is likely related to the volcanic-related U 5 uranium
mineralization and associated mineral assemblage (Fig. 2.8). The 1812±15 Ma U 5 -
mineralization coincides with the 1818±4 Ma Martin Lake mafic volcanism in the
73