Chemical Effects of α-Decay in Uranium Minerals

Regil, Eduardo Ordóñez; Schleiffer, J. J.; Adloff, J.P.; Roessler, Κ.

doi:10.1524/ract.1989.47.4.177

Cited by 29 publications

(4 citation statements)

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“…Preferential leaching may occur due to mineral lattice damage associated with 234 Th recoil (Rosholt et al 1963) or due to preferential oxidation of the 234 U in damaged mineral lattice by aqueous fl uids (Kolodny and Kaplan 1970). Regil et al (1989), Roessler (1983Roessler ( , 1989 and Adloff and Roessler (1991) present detailed models of 234 U oxidation due to -recoil.…”

Section: Alpha Recoilmentioning

confidence: 99%

Isotopic Gradients Across Fluid–Mineral Boundaries

Druhan

Brown

Huber

2015

Reviews in Mineralogy and Geochemistry

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Isotopic Gradients Across Fluid-Mineral Boundaries 357 composition is likely governed by the partitioning associated with a reaction (Lemarchand et al. 2004; Fantle and DePaolo 2007; DePaolo 2011). The accumulation of newly formed solids is also anticipated to vary with the local transport regime, which in turn exerts an infl uence on the isotopic composition of the fl uid-solid interface. This relationship between the dominant mechanisms of transport and fractionation suggests that over a representative volume of porous media a variety of fractionation factors may be observed. For example a fractionation factor characteristic of diffusive transport between the solid-fl uid surface and the well-mixed fl uid, or a fractionation factor associated with the difference in isotope composition between the fl uid and solid at each reactive surface. The continuum-scale or observable fractionation factor over the timescale of the reaction (e.g., seconds to years) is then subject to the location and volume of material sampled. Over much longer periods of time, processes like recrystallization and solid-state diffusion homogenize spatial zoning within the solid. This implies that transient isotopic partitioning should be observable over signifi cant periods of time, and that the observed macroscopic fractionation factor is potentially (1) a combination of multiple, distinct mechanisms and (2) variable as a result of parameters such as saturation state and fl ow rate.

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Section: Alpha Recoilmentioning

confidence: 99%

Isotopic Gradients Across Fluid–Mineral Boundaries

Druhan

Brown

Huber

2015

Reviews in Mineralogy and Geochemistry

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“…Studies on developing the conceptual model of oxidative isotope fractionation of 234 U have shown that 234 Th, the daughter of 238 U, is due to alpha-recoil pushed into areas of rock matrix where oxygen atoms accumulate around it (Adloff and Roessler, 1991;Regil et al, 1989). Extra energy generated during decay may increase the oxidation potential at the end of the 234 Th recoil trajectory.…”

Section: U/ 238 U Disequilibria In Uranium Roll Bedding Depositsmentioning

confidence: 99%

Understanding sulphuric acid leaching of uranium from ore by means of 234U/238U activity ratio as an indicator

et al. 2015

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“…(Regil et al, 1989) and thus readily mobilised, after production, as a uranyl complex in oxic fluids. Fossil corals investigated here are typically coated with Fe-Mn oxides precipitated from the water column.…”

Section: Addition Of Alpha-recoiled 234 Umentioning

confidence: 99%

Structural limitations in deriving accurate U-series ages from calcitic cold-water corals contrast with robust coral radiocarbon and Mg/Ca systematics

et al. 2013

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Radiocarbon and uranium-thorium dating results are presented from a genus of calcitic Antarctic cold-water octocorals (family Coralliidae), which were collected from the Marie Byrd Seamounts in the Amundsen Sea (Pacific sector of the Southern Ocean) and which to date have not been investigated geochemically. The geochronological results are set in context with solution and laser ablation-based element/Ca ratios (Li, B, Mg, Mn, Sr, Ba, U, Th).Octocoral radiocarbon ages on living corals are in excellent agreement with modern ambient deep-water  14 C, while multiple samples of individual fossil coral specimens yielded reproducible radiocarbon ages. Provided that local radiocarbon reservoir ages can be derived for a given time, fossil Amundsen Sea octocorals should be reliably dateable by means of radiocarbon.In contrast to the encouraging radiocarbon findings, the uranium-series data are more difficult to interpret. The uranium concentration of these calcitic octocorals is an order of magnitude lower than in the aragonitic hexacorals that are conventionally used for geochronological investigations. While modern and Late Holocene octocorals yield initial  234 U in good agreement with modern seawater, our results reveal preferential inward diffusion of dissolved alpha-recoiled 234 U and its impact on fossil coral  234 U. Besides alpha-recoil related 234 U diffusion, high-resolution sampling of two fossil octocorals further demonstrates that diagenetic uranium mobility has offset apparent coral U-series ages. Combined with the preferential alpha-recoil 234 U diffusion, this process has prevented fossil octocorals from preserving a closed system U-series calendar age for longer than a few thousand years.Moreover, several corals investigated contain significant initial thorium, which cannot be Mg/Ca ratios within single octocoral specimens are internally strikingly homogenous, and appear promising in terms of their response to ambient temperature. Magnesium/lithium ratios are significantly higher than usually observed in other deep marine calcifiers and for many of our studied corals are remarkably close to seawater compositions. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPTAlthough this family of octocorals is unsuitable for glacial deep-water  14 C reconstructions, our findings highlight some important differences between hexacoral (aragonitic) and octocoral (calcitic) biomineralisation. Calcitic octocorals could still be useful for trace element and some isotopic studies, such as reconstruction of ambient deep water neodymium isotope composition or pH, via boron isotopic measurements.

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Chemical Effects of α-Decay in Uranium Minerals

Cited by 29 publications

References 0 publications

Isotopic Gradients Across Fluid–Mineral Boundaries

Isotopic Gradients Across Fluid–Mineral Boundaries

Understanding sulphuric acid leaching of uranium from ore by means of 234U/238U activity ratio as an indicator

Structural limitations in deriving accurate U-series ages from calcitic cold-water corals contrast with robust coral radiocarbon and Mg/Ca systematics

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