Variations in the uranium isotopic compositions of uranium ores from different types of uranium deposits

Uvarova, Yulia; Kyser, T. Kurt; Geagea, Majdi Lahd; Chipley, Don

doi:10.1016/j.gca.2014.09.034

Cited by 56 publications

(41 citation statements)

References 52 publications

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“…Uranium leached from ore during alteration/recrystallization results in minerals enriched in 234 U [9], and therefore the 238 U/ 234 U ratio is primarily used to evaluate recent fluid alteration events. Given the short half-life of 234 U, the 238 U/ 234 U ratio yields a result consistent with secular equilibrium if the deposit or mineral has not experienced alteration within the past 2.5 million years [9].This study reports trace element abundances and Pb, Sr, and U isotopic ratios of uraninites (n = 15) from ore deposits within North America and one from the Democratic Republic of the Congo in relation to establishing baseline signatures for nuclear forensic applications. Secondary Pb-Pb isochron ages for several uraninite samples were obtained by both SM-and LA-multicollector (MC) ICP-MS.…”

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confidence: 81%

“…In recent years, improvements in analytical methods and equipment have enhanced the reporting of chemical and isotopic signatures at faster time scales and with lower detection limits (e.g., [7,8]). Consequently, there has been renewed interest and more detailed investigations into the U isotope signatures of nuclear materials, such as uraninite (e.g., [9,10]). Geochronological investigations of nuclear materials, such as those employing the 230 Th dating technique (e.g., [11,12]) also provide insightful forensic signatures.…”

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The Role of Continental Crust in the Formation of Uraninite-Based Ore Deposits

et al. 2020

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This study reports trace element abundances and Pb, Sr, and U isotopic signatures of uraninite from a variety of ore deposits in order to establish baseline forensic information for source attribution of raw, natural U-rich samples. Trace element concentrations, reported here, provide insights into uraninite crystal substitution mechanisms and possible crustal sources of U, including mobility of trace elements between pristine versus altered fractions. Spatially resolved laser ablation (LA) multicollector (MC) inductively coupled plasma mass spectrometry (ICP-MS) analyses were used to determine secondary 207Pb-206Pb isochron ages, and these were validated by corroborative results obtained by solution mode (SM) MC-ICP-MS for the same sample. Secondary Pb-Pb isochron ages obtained, in this study, indicate that uraninite alteration occurs shortly after ore mineralization. Initial 87Sr/86Sr values correlate in general with host craton age, and therefore suggest that uraninite ore formation is closely linked to the nature of the bedrock geology. The δ238U values are explained by invoking multiple physicochemical conditions and parameters such as temperature, nuclear field shift, oxidation, and source rock composition. The δ234U values indicate that the uraninites, investigated here, have undergone recent alteration, but the latter has not perturbed the Pb-Pb secondary isochron ages.

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The Role of Continental Crust in the Formation of Uraninite-Based Ore Deposits

et al. 2020

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“…Compilation of the d 238 U values obtained from this study and literature data(Stirling et al, 2005(Stirling et al, , 2006Weyer et al, 2008;Bopp et al, 2009;Amelin et al, 2010;Montoya-Pino et al, 2010;Brennecka et al, 2010a Brennecka et al, ,b, 2011aBouvier et al, 2011;Larsen et al, 2011;Brennecka and Wadhwa, 2012;Connelly et al, 2012;Hiess et al, 2012;Telus et al, 2012;Kaltenbach, 2012;Asael et al, 2013;Cheng et al, 2013;Kendall et al, 2013Kendall et al, , 2015Andersen et al, 2014Andersen et al, , 2015Dahl et al, 2014;Goto et al, 2014;Iizuka et al, 2014;Murphy et al, 2014;Uvarova et al, 2014;Goldmann et al, 2015;Noordmann et al, 2015) (see Supplementary Material…”

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Uranium isotopic compositions of the crust and ocean: Age corrections, U budget and global extent of modern anoxia

Tissot

Dauphas

2015

Geochimica et Cosmochimica Acta

185

197

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The 238 U/ 235 U isotopic composition of uranium in seawater can provide important insights into the modern U budget of the oceans. Using the double spike technique and a new data reduction method, we analyzed an array of seawater samples and 41 geostandards covering a broad range of geological settings relevant to low and high temperature geochemistry. Analyses of 18 seawater samples from geographically diverse sites from the Atlantic and Pacific oceans, Mediterranean Sea, Gulf of Mexico, Persian Gulf, and English Channel, together with literature data (n = 17), yield a d 238 U value for modern seawater of À0.392 ± 0.005& relative to CRM-112a. Measurements of the uranium isotopic compositions of river water, lake water, evaporites, modern coral, shales, and various igneous rocks (n = 64), together with compilations of literature data (n = 380), allow us to estimate the uranium isotopic compositions of the various reservoirs involved in the modern oceanic uranium budget, as well as the fractionation factors associated with U incorporation into those reservoirs. Because the incorporation of U into anoxic/euxinic sediments is accompanied by large isotopic fractionation (D Anoxic/Euxinic-SW = +0.6&), the size of the anoxic/euxinic sink strongly influences the d 238 U value of seawater. Keeping all other fluxes constant, the flux of uranium in the anoxic/euxinic sink is constrained to be 7.0 ± 3.1 Mmol/yr (or 14 ± 3% of the total flux out of the ocean). This translates into an areal extent of anoxia into the modern ocean of 0.21 ± 0.09% of the total seafloor. This agrees with independent estimates and rules out a recent uranium budget estimate by Henderson and Anderson (2003). Using the mass fractions and isotopic compositions of various rock types in Earth's crust, we further calculate an average d 238 U isotopic composition for the continental crust of À0.29 ± 0.03& corresponding to a 238 U/ 235 U isotopic ratio of 137.797 ± 0.005. We discuss the implications of the variability of the 238 U/ 235 U ratio on Pb-Pb and U-Pb ages and provide analytical formulas to calculate age corrections as a function of the age and isotopic composition of the sample. The crustal ratio may be used in calculation of Pb-Pb and U-Pb ages of continental crust rocks and minerals when the U isotopic composition is unknown.

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“…On the other hand, as argued by Romaniello et al (2013), δ 238 U values of ancient carbonates, affected by diagenetic processes, may be enriched in 238 U due to U accumulation under anoxic pore water conditions. Large differences of nearly 2 ‰ have been observed between uranium ores formed at low and at high temperatures (Bopp et al 2009;Uvarova et al 2015;Murphy et al 2014): magmatic ores vary from −0.7 to −0.3 ‰ whereas sandstonetype low temperature ores have δ 238 U-values around +0.4 ‰. Isotope variations seem to be controlled by the isotope composition of the U source and the efficiency of U reduction.…”

Section: Characteristic U Signaturesmentioning

confidence: 99%

Isotope Fractionation Processes of Selected Elements

Hoefs

2015

Stable Isotope Geochemistry

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Variations in the uranium isotopic compositions of uranium ores from different types of uranium deposits

Cited by 56 publications

References 52 publications

The Role of Continental Crust in the Formation of Uraninite-Based Ore Deposits

The Role of Continental Crust in the Formation of Uraninite-Based Ore Deposits

Uranium isotopic compositions of the crust and ocean: Age corrections, U budget and global extent of modern anoxia

Isotope Fractionation Processes of Selected Elements

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