The isotope geochemistry of uranium: Igneous petrology, ore deposits, and groundwater contamination

Bopp, Charles J., IV

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https://hdl.handle.net/2142/18351 Copy

Description

Title

The isotope geochemistry of uranium: Igneous petrology, ore deposits, and groundwater contamination

Author(s)

Bopp, Charles J., IV

Issue Date

2011-01-14T22:47:12Z

Director of Research (if dissertation) or Advisor (if thesis)

Lundstrom, Craig C.

Doctoral Committee Chair(s)

Lundstrom, Craig C.

Committee Member(s)

• Johnson, Thomas M.
• Sanford, Robert A.
• Marshak, Stephen

Department of Study

Geology

Discipline

Geology

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• uranium
• uranium isotopes
• groundwater
• groundwater contamination
• groundwater remediation
• mass spectrometry
• thermal diffusion
• thermal migration
• uranium contamination
• uranium remediation
• bioremediation
• uranium ore
• roll front
• uranium mining
• uranium reduction
• thermal migration zone refining
• basalt

Abstract

This study applies high precision 238U/235U measurement techniques two three geologic settings: basalt differentiation, uranium ore genesis, and the remediation of a uranium-contaminated groundwater system. In the latter two cases, 238U/235U is used as a tracer of uranium reduction. 238U preferentially enters the reduced (solid) U phase, thus analysis of U ores can reveal information on the development of an ore body (chapters 2 and 3) while analysis of 238U/235U in contaminated groundwater can be used to monitor the progress of uranium reduction (chapters 4 and 5). 238U/235U measurements are applied in a less orthodox way to the problems of magmatic differentiation, where 235U separates from 238U when a partially-molten basalt is allowed to equilibrate under a temperature gradient. This extends the previous work on the isotopic effects of thermal diffusion into the heavy elements, and presents new research on the mineralogical development of a basalt under a thermal gradient. There are five studies in this work: 238U/235U is first applied to detect the effect of a thermal gradient on a partially molten basalt, with variations of ≈1.0‰ found over ≈150°C. 238U/235U is then applied to the case of sedimentary reduced uranium ore deposits. A general survey of finds a shift of ≈1.0‰ between magmatic-type and sandstone-type uranium ores. A small-scale study of a uranium roll front deposit finds 238U/235U variation in excess of 1.0‰. In both cases, the shift in 238U/235U is attributed to the nuclear field shift effect during uranium reduction. 238U/235U analysis is then applied to a groundwater remediation setting at a biostimulation experiment at the former site of a uranium tailings pile in Rifle, Colorado. 238U/235U analysis of a bioremediation experiment finds a shift of ≈1.0‰ associated with a large (≈90%) decrease in dissolved uranium concentration. This shift is again attributed to the nuclear field shift effect during uranium reduction. Finally, 238U/235U analysis is used to trace the cause of an abnormal change in dissolved uranium concentration during a subsequent biostimulation experiment at the Rifle, Colorado site. By analyzing the sense and timing of shifts in 238U/235U relative to shifts in dissolved uranium concentration I am able to differentiate between uranium reoxidation, uranium desorption, and advection of uranium-bearing groundwater.

Graduation Semester

2010-12

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http://hdl.handle.net/2142/18351

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Copyright 2010 Charles John Bopp IV

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