Ilmenites and their alteration products, sinkholes for uranium and radium in roll-front deposits after the example of South Tortkuduk (Kazakhstan)

Boulesteix, Thomas; Cathelineau, ‪Michel; Deloule, Étienne; Brouand, Marc; Toubon, H.; Lach, Philippe; Fiet, Nicolas

doi:10.1016/j.gexplo.2019.106343

Cited by 13 publications

(4 citation statements)

References 42 publications

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“…Such observations have already been made in the same geological context (namely the South Tortkuduk roll-front deposit in Kazakhstan) (Boulesteix et al, 2019). Chemical maps of Fe-Ti minerals of the L sample obtained from microprobe analysis (WDS X-ray spectrometry) confirm the almost total depletion of uranium after acidic leaching (Figure S4, supplementary material).…”

Section: Petrographic Observations and Digital Autoradiograph Of Alpha Activitysupporting

confidence: 65%

“…Understanding the mobility of these radio-elements is an important environmental issue in the post-mining ISR context. While previous works highlighted the retention of 226 Ra by celestine (SrSO4), ilmenite (TiFeO3), barite (BaSO4) and clay minerals (Robin et al, 2017;Lestini et al, 2019;Heberling et al, 2018;Boulesteix et al, 2019;Billon et al, 2020), the geochemical behaviour of U-daughter elements is still poorly understood in an acidic context (Déjeant et al, 2016;Déjeant et al, 2014;Chautard et al, 2017;Ballini et al, 2020), in which other important isotopes in the 238 U series are 230 Th, 222 Rn and polonium isotopes ( 218 Po, 214 Po, 210 Po). As of today, the geochemical studies of U and its daughter elements are based on sequential leaching of the bulk material, which is an expensive, destructive and complex method which is also difficult to interpret (Blanco et al, 2004;Bacon and Davidson, 2008;Menozzi et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

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Mobility of daughter elements of 238U decay chain during leaching by In Situ Recovery (ISR): New insights from digital autoradiography

Angileri

Sardini

Beaufort

et al. 2020

Journal of Environmental Radioactivity

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In highly permeable sedimentary rock formations, U extraction by in-situ leaching techniques (ISR  In-Situ Recovery) is generally considered to have a limited environmental impact at ground level. Significantly, this method of extraction produces neither mill tailings nor waste rocks. Underground, however, the outcome for 238 U daughter elements in aquifers is not well known because of their trace concentrations in the host rocks. Thus, understanding the in-situ mobility of these elements remains a challenge. Two samples collected before and after six months of ISR experiments (Dulaan Uul, Mongolia) were studied with the help of a digital autoradiography technique (DA) of alpha particles, bulk alpha spectrometry, and complementary petrographic observation methods. These techniques demonstrate that before and after leaching, the radioactivity is concentrated in altered and microporous Fe-Ti oxides.Most of the daughter elements of U remain trapped in the rock after the leaching process. DA confirms that the alpha activity of the Fe-Ti oxides remains high after uranium leaching, and the initial secular equilibrium of the 238 U series for 230 Th to 210 Po daughter elements (including 226 Ra) of the fresh rocks is maintained after leaching. While these findings should be confirmed by more systematic studies, they already identify potential mechanisms explaining why the U-daughter concentrations in leaching water are low.

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Section: Petrographic Observations and Digital Autoradiograph Of Alpha Activitysupporting

confidence: 65%

Section: Introductionmentioning

confidence: 99%

Mobility of daughter elements of 238U decay chain during leaching by In Situ Recovery (ISR): New insights from digital autoradiography

Angileri

Sardini

Beaufort

et al. 2020

Journal of Environmental Radioactivity

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“…In order to validate the new approach described above, we use 76 gamma spectra of uranium ore samples recorded by ORANO Mining (such as the spectrum of Fig. 1) to study radioactive disequilibrium in Dulann Uul and Zoovch Ovoo deposits, Mongolia [2]. The samples have different densities and filling heights.…”

Section: Experimental Qualificationmentioning

confidence: 99%

“…The gamma spectra are measured with a Falcon 5000 [1] handheld spectrometer from Mirion-Canberra, equipped with a HPGe planar detector (BEGE 2830 model). The method is studied by MCNP6 Monte Carlo calculation by the Nuclear Measurement Laboratory of CEA, DEN, Cadarache, and validated with experimental data obtained by ORANO Mining during a measurement campaign intended to characterize uranium content and imbalance of the samples [2]. The two rays at 92 keV and 98 keV are systematically present with a high intensity on uranium ore spectra (see example of a small concentration sample in Fig.…”

Section: Introductionmentioning

confidence: 99%

The use of self-induced X-ray fluorescence in gamma-ray spectroscopy of uranium ore samples

Marchais¹,

Pérot²,

Carasco³

et al. 2020

EPJ Web Conf.

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Gamma logging for uranium exploration are currently based on total counting with Geiger Müller gas detectors or NaI (TI) scintillators. However, the total count rate interpretation in terms of uranium concentration may be impaired in case of roll fronts, when the radioactive equilibrium of the natural 238U radioactive chain is modified by differential leaching of uranium and its daughter radioisotopes of thorium, radium, radon, etc. Indeed, in case of secular equilibrium, more than 95 % of gamma rays emitted by uranium ores come from 214Pb and 214Bi isotopes, which are in the back-end of 238U chain. Consequently, these last might produce an intense gamma signal even when uranium is not present, or with a much smaller activity, in the ore. Therefore, gamma spectroscopy measurements of core samples are performed in surface with high-resolution hyper-pure germanium HPGe detectors to directly characterize uranium activity from the 1001 keV gamma ray of 234mPa, which is in the beginning of 238U chain. However, due to the low intensity of this gamma ray, i.e. 0.84 %, acquisitions of several hours are needed. In view to characterize uranium concentration within a few minutes, we propose here a method using both the 92 keV gamma ray of 234Th and the 98.4 keV uranium X-ray. This last is due to uranium self-induced fluorescence caused by gamma radiations of 214Pb and 214Bi, which create a significant Compton scattering continuum acting as a fluorescence source and resulting in the emission of uranium fluorescence X-rays. The comparison of the uranium activity obtained with the 92 keV and 98.4 keV lines allows detecting a uranium heterogeneity in the ore. Indeed, in case of uranium nugget, the 92 keV line leads to underestimated uranium concentration due to gamma self-absorption, but on the contrary the 98.4 keV line leads to an overestimation because of increased fluorescence. In order to test this new approach, several tens of uranium ore samples have been measured with a handheld HPGe FALCON 5000 detector.

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Gamma dose rate distribution in the Unegt subbasin, a uranium deposit area in Dornogobi Province, southeastern Mongolia

Omori

Gun-Aajav²,

Enkhgerel³

et al. 2019

Environ Sci Pollut Res

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Ilmenites and their alteration products, sinkholes for uranium and radium in roll-front deposits after the example of South Tortkuduk (Kazakhstan)

Cited by 13 publications

References 42 publications

Mobility of daughter elements of 238U decay chain during leaching by In Situ Recovery (ISR): New insights from digital autoradiography

Mobility of daughter elements of 238U decay chain during leaching by In Situ Recovery (ISR): New insights from digital autoradiography

The use of self-induced X-ray fluorescence in gamma-ray spectroscopy of uranium ore samples

Gamma dose rate distribution in the Unegt subbasin, a uranium deposit area in Dornogobi Province, southeastern Mongolia

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