Proposed Title 1: - Queen's University

ca. 1820 Ma that triggered reactivation of the El Sherana-Palette fault system (Lally and
Bajwah, 2006). Faulting and brecciation was likely more focused in zones of pre-existing
tectonic weakness that were previously affected by pre-ore alteration, thus creating
structural traps near the unconformity that were open to fluid flow, hydrothermal alteration
and U mineralization. The mineralization formed when a 250 o C, low latitude, oxidizing, U-
bearing basinal brine from diagenetic aquifers in the Coronation sandstone, similar to those
of unconformity-related U-deposits in the Athabasca (e.g. Cuney and Kyser, 2008) and
Kombolgie basins (e.g. Polito et al., 2004, 2006), descended downward into the
unconformity along fracture systems created by brittle reactivation of the El Sherana-
Palette fault system (Fig. 5.1). At Coronation Hill, the mineralizing brine contained U, Au
and PGE, the former most likely leached from detrital U-bearing minerals in the El Sherana
Basin sandstone, and the Au and PGE from alteration of felsic volcanics and mafic rocks
that are part of the El Sherana Group (Jagodzinski, 1992). Interaction of oxidizing basinal
brines with the reducing Fe-rich ferruginous shale of the Koolpin Formation may have led
to deposition of the U-ore metals at El Sherana. The U, Au and PGE ore associated with the
quartz feldspar porphyry at Coronation Hill may have resulted from acid neutralization and
moderate reduction caused by fluid interaction with feldspathic host rocks (Needham,
1988b; Wyborn, 1992; Mernagh et al., 1994).
5.2.3. Late alteration events
Subsequent to their formation, U deposits in the Beaverlodge and South Alligator
River areas were affected by alteration events associated with multiple stages of
deformation and fluid events that are related to both near and far-field geodynamic events
198