Browsing by Author "Mclntyre, MG"

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    234U/238U signatures associated with uranium ore bodies: part 1 Ranger 3
    (Elsevier Science Ltd, 2013-04-01) Lowson, RT; Mclntyre, MG
    The Ranger 3 ore body is an early Proterozoic U ore body in the Alligator Rivers U province, Northern Territory, Australia. It has surface expression with a redox front located between 30 and 50 m below the surface. The ground water U concentration and U-234/U-238 AR signature in the top 10 m of the weathered zone are reported for 357 samples collected over 4 wet seasons, at 5 depths, along a transect in-line with the hydraulic gradient and along the centre line of the ore body and its associated dispersion halo. The results show that the weathered zone displays a general U isotope feature for this type of ore body with the U-234/U-238 AR for the ground water and amorphous phase of the solid matrix being less than 1. The ground water U-234/U-238 AR is independent of the annual monsoonal climate and depth within the range surface to 10 m. In the vicinity of the U ore body the ground water U-234/U-238 AR is 0.75 and is very similar to the U-234/U-238 AR of the amorphous phase of the solid (0.76). The U-234/U-238 ARs of the amorphous phase and ground water rise and separate to values of 0.88 and 1.02 at the end of the transect. The rise and separation in U-234/U-238 AR are interpreted as evidence that the source of the U in the ground water is from the water-soluble sub-phase of the amorphous phase and that the ground water flow is too fast to allow the processes occurring across the solid water interface to reach chemical equilibrium. The data set is a robust characterisation of the coarse and fine detail of the U-234/U-238 AR signature in the weathered zone of U ore bodies. © 2013, Elsevier Ltd.
  • No Thumbnail Available
    Item
    234U/238U signatures associated with uranium ore bodies: part 2 Manyingee
    (Elsevier Science Ltd, 2013-04-01) Lowson, RT; Mclntyre, MG
    The Manyingee ore body is a roll-front U ore body located at depth in the Cretaceous sandstone sediments of a Proterozoic palaeo valley. It is located in a confined aquifer. The aquifer is recharged 4 km upstream by the Ashburton River. Groundwater samples were collected at and up to 4.7 km downstream of the ore body. The ground water U-234/U-238 activity ratios (AR) were elevated to 1.86 in the vicinity of the ore body and then declined to 1.06 over the 4.7 km transect. The elevated U-234/U-238 ARs are attributed to selective leaching of U-234 sites by oxidising waters, with a recoil as a necessary precursor to produce activated U-234 sites. Direct ejection into another phase following a recoil is considered to be a minor contributor to U-234 U-238 disequilibrium in this environment. The profile is considered to be typical of the U-234/U-238 AR profile at and down gradient of the redox front of a U ore body. © 2013, Elsevier Ltd.