Uranium ore-forming systems of the - Geoscience Australia
Uranium ore-forming systems of the - Geoscience Australia
Uranium ore-forming systems of the - Geoscience Australia
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<strong>Uranium</strong> <strong>ore</strong>-<strong>forming</strong> <strong>systems</strong> <strong>of</strong> <strong>the</strong> Lake Frome region2.2.1 Paleozoic – Arrowie BasinIn <strong>the</strong> study area <strong>the</strong> Arrowie Basin is represented by <strong>the</strong> Moorowie and Yalkalpo ‘Synclines’ orsub-basins which contain thick unfolded strata to <strong>the</strong> west and east, respectively, <strong>of</strong> <strong>the</strong> BenagerieRidge (Gravestock and Cowley, 1995, Figs. 2.1, 2.2). The Arrowie Basin is comprised <strong>of</strong>shallow marine sedimentary siliciclastic and carbonate deposits. The succession has beensubdivided into three sequences: Є1, a carbonate dominated sequence that progrades intoevaporite facies at <strong>the</strong> top <strong>the</strong> sequence; Є2, a redbed and carbonate sequence, and Є3, a thickpackage <strong>of</strong> red sandstones that coarsen up-sequence (Drexel, et al., 1993). Between sequences Є1and Є2 minor episodic tectonic and volcanic activity occurred.Petroleum exploration in <strong>the</strong> Moorowie sub-basin delineated a number <strong>of</strong> ‘shows’ but nosignificant discoveries have been made.Figure 2.2: Stratigraphic relationship diagram for <strong>the</strong> Arrowie Basin showing <strong>the</strong> correlation betweenlithologies and sequences. Source: Gravestock and Cowley (1995).2.2.2 Mesozoic – Eromanga BasinThe Eromanga Basin is an intracratonic sag basin covering some million square kilometres <strong>of</strong>east-central <strong>Australia</strong> (Fig. 2.3). A detailed stratigraphic framework for <strong>the</strong> Eromanga andadjacent basins was constructed by Gravestock et al. (1986), Krieg (1995) and Radke et al. (2000),among o<strong>the</strong>rs. The Eromanga Basin has been subdivided into three main stratigraphic sequences:a lower non-marine sequence (early Jurassic to earliest Cretaceous), a middle marine sequence(early Cretaceous) and an upper non-marine sequence (late Cretaceous).The lower non-marine sequence consists <strong>of</strong> medium-grained sands deposited in a braided fluvialenvironment, followed by fine-grained lacustrine sands, silts and shales. Volcaniclastic material ism<strong>ore</strong> abundant in <strong>the</strong> lower non-marine succession to <strong>the</strong> north and east <strong>of</strong> <strong>the</strong> Frome Embayment,Page 14 <strong>of</strong> 151