Evaluating the rate of migration of an uranium deposition front within the Uitenhage Aquifer

J. C. Vogel, A. S. Talma, T. H.E. Heaton, J. Kronfeld

Research output: Contribution to journalConference articlepeer-review

Abstract

The solubility of uranium in groundwater is very sensitive to changes in redox conditions. Many secondary (sandstone-type) uranium deposits have been formed when soluble U has precipitated after encountering reducing conditions in the subsurface. In the groundwater of the Uitenhage Aquifer (Cape Province, South Africa), 238U-series isotopes were used to assist in studying the history of the reducing barrier. Uranium isotopes were used to determine the present position of the barrier. Radium and radon were used to evaluate the path of migration that the front of the oxygen depletion zone has taken over the past 105 years. During this time the reducing barrier has moved, leaving in its wake a trail of U in various stages of secular equilibrium with its daughter 230Th. The 226Ra daughter of 230Th is not very mobile. Its growth upon the aquifer wall is reflected in the Rn content of the water. This in turn, due to the relatively great age of the water, indicates the extent of the 230Th ingrowth (from precipitated U) that took place before the barrier migrated.

Original languageEnglish
Pages (from-to)269-276
Number of pages8
JournalJournal of Geochemical Exploration
Volume66
Issue number1-2
DOIs
StatePublished - Jul 1999
EventProceedings of the 18th International Geochemical Exploration Symposium 'Geochemical Exploration 1997' - Jerusalem, Isr
Duration: 25 May 199729 May 1997

Keywords

  • Redox changes in aquifer
  • Sandstone-type uranium deposit
  • South Africa
  • Uranium series

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