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Koongarra, and deposits in the SAVMF (Hills and Richards, 1972; Gulson and Mizon,
1980). Subsequent fault reactivation and alteration continued into the Phanerozoic at ca.
530 Ma - 510 Ma (Fig. 4.16), coincident with the formation of Cambrian to early
Ordovician Georgina Basin (Shergold and Druce, 1980) and the extrusion of the 513 Ma
Antrim Volcanics (Hanley and Wingate, 2000) outpouring early Cambrian Plateau over
most of the North Australian Craton (Myers et al., 1996). Following a period of apparent
tectonic quiescence from the Ordovician to Devonian (Fig. 4.16), uraninite alteration
occurred during the Carboniferous coincident with tectonic activities during continental
rifting that separated Asian terranes to the north from the NW Australian Gondwana to the
south at around ca. 350 Ma - 270 Ma (Metcalfe, 2001).
Lower intercept ages in the U-Pb system of 122±90 Ma, 45±92 Ma and 23±73 Ma
(Figs. 4.12H, 4.12G and 4.12B, respectively) and recent chemical Pb ages of uraninite
(Table 4.1) record tectonic activities along the western active margin of the Australian plate
including the Mesozoic breakup between Greater India and Australia at ca. 136 Ma and
various recent collisional processes and plate boundary reorganizations north and east of
Australia during the Cenozoic (Müller et al., 2000).
4.7. Conclusions
Hydrothermal alteration, uranium mineralization, and late remobilization events have
affected rocks of the SAVMF during protracted tectonic evolution that spans over 1.8 Gyrs
(Table 4.7). Results indicate that these deposits formed at ca. 1820 Ma, subsequent to
deposition of the El Sherana Group and are therefore, older than the unconformity-related
U mineralization at 1650-1675 Ma in the Kombolgie Basin. The formation of these
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