Mobility of Uranium, Thorium and Lanthanides Around the Bangombe Natural Reactor (Gabon)

1994 ◽  
Vol 353 ◽  
Author(s):  
R. Bros ◽  
F. Gauthier-Lafaye ◽  
P. Larque ◽  
J. Samuel ◽  
P. Stille
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Clay Minerals ◽  
Nuclear Reactor ◽  
Black Shales ◽  
Weathering Profile ◽  
The Core ◽  
Reducing Conditions ◽  
Isotopic Studies ◽  
Textural Evidence

AbstractNew mineralogical and isotopic studies were carried out on samples from the Bangombé natural nuclear reactor. This reactor is located at shallow depth in the weathering profile and has been subjected to severe supergene alteration. Textural evidence indicates partial dissolution of uraninite in the Bangombé ore related to precipitation of Fe-Ti oxi-hydroxides and clay minerals (kaolinite and metahalloysite). As a consequence of the alteration of the uraninite, uranium and f issiogenic rare earth elements were released in the clayey border of the reactor, whereas radiogenic 232Th remained confined in the close vicinity of the core. A retention effect is also evidenced, under reducing conditions, in the black shales located above the reactor.

Distribution of rare earth elements in some North Atlantic Kimmeridgian black shales

Nature ◽  
1979 ◽  
Vol 278 (5702) ◽  
pp. 339-341 ◽  
Author(s):  
HENNING DYPVIK ◽  
ARILD O. BRUNFELT
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
North Atlantic ◽  
Black Shales

scholarly journals Chemical weathering intensity and rare earth elements release from a chlorite schist profile in a humid tropical area, Bengbis, Southern Cameroon

2021 ◽  
Vol 16 (2) ◽  
pp. 123-145
Author(s):  
Vincent Laurent Onana ◽  
Estelle Ndome Effoudou ◽  
Sylvia Desirée Noa Tang ◽  
Véronique Kamgang Kabeyene ◽  
Georges Emmanuel Ekodeck
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Chemical Weathering ◽  
Weathering Profile ◽  
Ree Distribution ◽  
Weathering Intensity ◽  
Southern Cameroon ◽  
La Modification ◽  
Co Precipitation ◽  
Hydrolysis Of

RésuméUn profil d’altération développé sur chloritoschistes de la zone de Bengbis (Sud Cameroun) a été choisi pour quantifier l’intensité de l’altération et comprendre le comportement des terres rares. Les valeurs de l’indice d’altération mafique combinées aux diagrammes ternaires du système Al – Fe – Mg – Ca – Na – K montrent que l’hydrolyse des feldspaths est proportionnelle à celle des minéraux mafiques (pertes en Mg), bien que l’hydrolyse des plagioclases (Ca, Na) soit plus intense que celle des minéraux ferromagnésiens. Les matériaux d’altération étudiés sont localisés dans le domaine de la kaolinitisation, à l’exception des matériaux nodulaires qui sont légèrement latritiss. La modification du comportement du Mg dans le milieu d’altération s’exprime par les faibles valeurs du rapport Ca/Mg. Le potassium et Be sont lessivés dans le sol en association avec Mg. L’ordre de mobilité des éléments dans l’environnement d’altération étudié est : Ca ≈ Na > Fe2+ ≈ Sr > Mg ≈ Co > Mn > Li > Ba > Rb > P > Cd > Ni > Si > Be > K > Sn. Les enrichissements en K, Cs et Be dans les saprolites sont liés à la présence d’illite. L’accumulation en Cs dans le sol est due à la présence de kaolinite. Le système le plus stable dans le milieu d’altération étudié est : Hf – Nb – W – U. Les saprolites, les matériaux nodulaires et les matériaux argileux meubles superficiels sont appauvris en terres rares par rapport à la roche mère. Les terres rares présentent trois types de comportement le long du profil d’altération, comme l’indiquent les valeurs du rapport (La/Yb)N ((La/Yb)N < 1, (La/Yb)N ~ 1 et (La/Yb)N > 1). Les terres rares légères et les terres rares moyennes s’accumulent dans les matériaux d’altération pour des valeurs de pH comprises entre 5,5 et 5,6 et pour celles de Eh variant entre +60 et +70mV. L’ordre de mobilité de ces éléments dans ces matériaux est le suivant : terres rares moyennes > terres rares lourdes terres rares légères. Ce fait est contre-intuitif, car les terres lourdes sont plus mobiles dans les environnemenst supergènes que les terres rares légères. L’adsorption ou la co-précipitation de ces terres rares sur les oxydes de fer peut principalement contrôler la concentration de ces éléments dans le profil d’altération. Les faibles anomalies en Ce dans les matériaux d’altération de la zone de Bengbis, dues au changement de Ce3+ en Ce4+, sont probablement dues à la présence de faibles quantités de rhabdophane. Les matériaux d’altération étudiés présentent un fractionnement en Gd (Gd/Gd* ~0.70 – 0.84) dues à une intense lixiviation. Ce fait a rarement été signalé dans un environnement d’altération latéritique. Il semble qu’une partie de la distribution et de la remobilisation du gadolinium soit contrôlée par des minéraux mafiques dans les matériaux d’altération étudiés. La distribution et la mobilisation des terres rares sont donc contrôlées par (1) l’adsorption ou la coprécipitation dans les minéraux mafiques et Fe, (2) et légèrement par les minéraux contenant des terres rares tels que le rhabdophane, rencontrés dans les matériaux d’altération étudiés. Abstract An in situ weathering profile overlying chlorite schists in southern Cameroon was chosen to quantify chemical weathering intensity and to study the behaviour of rare earth elements (REE). Mafic index alteration values combined with the ternary diagrams of the Al – Fe – Mg – Ca – Na – K system show that the hydrolysis of feldspars is proportional to that of mafic minerals (losses in Mg), although the hydrolysis of the plagioclases (Ca, Na) is more intense than that of ferromagnesian minerals. The studied materials are localised in the domain of kaolinitisation, except for nodular materials which are slightly lateritised. The change in the behaviour of Mg in the weathering environment is expressed by the low values in Ca/Mg ratio. Potassium and Be are leached in the soil in association with Mg. The order of mobility of the elements in the weathering environment is: Ca ≈  Na > Fe2+ ≈ Sr > Mg ≈ Co > Mn > Li > Ba > Rb > P > Cd > Ni > Si > Be > K > Sn. The enrichments in K, Cs and Be in saprolites are linked to the presence of illite. Cesium accumulation in the soil is due to the presence of kaolinite. The most stable system is: Hf – Nb – W – U. Saprolites, nodular and loose clayey materials are depleted in REE relative to the parent rock. REE exhibit three types of behaviour along the Bengbis profile like indicated by (La/Yb)N ratio values ((La/Yb)N < 1, (La/Yb)N ~ 1 and (La/Yb)N > 1). Light REE and Middle REE accumulate in the weathering materials for pH values ranging between 5.5 and 5.6 and for those of Eh varying between +60 and +70mV. The order of mobility of REE in these horizons is: Middle REE > Heavy REE ≈ Light REE. This fact is counter-intuitive, because Heavy REE are more mobile in supergene environment than Light REE. Adsorption or co-precipitation of LREE onto Fe oxides mainly may control the concentration of these elements in the profile. Weak Ce anomalies in the weathering materials of Bengbis area, due to the change in Ce3+ to Ce4+, are probably due to the presence of low amounts in rhabdophane. The studied weathering materials show a fractionation in Gd (Gd/Gd* ~0.70 – 0.84) due to intense chemical leaching. This fact has been rarely reported in lateritic weathering environment. It appears that, a part of Gd distribution and remobilization is controlled by mafic minerals in the studied weathered materials. REE distribution and mobilization are thus controlled by (1) adsorption or co-precipitation in mafic and Fe minerals, (2) and slightly by REE-bearing minerals such as rhabdophane found in the studied weathering profile.  

Understanding the role of natural clay minerals as effective adsorbents and alternative source of rare earth elements: Adsorption operative parameters

2019 ◽  
Vol 185 ◽  
pp. 149-161 ◽  
Author(s):  
Aref Alshameri ◽  
Hongping He ◽  
Chen Xin ◽  
Jianxi Zhu ◽  
Wei Xinghu ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Clay Minerals ◽  
Natural Clay ◽  
Alternative Source

Recovery of rare earth elements adsorbed on clay minerals: I. Desorption mechanism

2012 ◽  
Vol 117-118 ◽  
pp. 71-78 ◽  
Author(s):  
Georgiana A. Moldoveanu ◽  
Vladimiros G. Papangelakis
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Clay Minerals ◽  
Desorption Mechanism

Residence and fractionation of rare earth elements during kaolinization of alkaline peraluminous granites in NW Spain

Clay Minerals ◽  
2007 ◽  
Vol 42 (3) ◽  
pp. 341-352 ◽  
Author(s):  
E. Galán ◽  
J. C. Fernández-Caliani ◽  
A. Miras ◽  
P. Aparicio ◽  
M. G. Márquez
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Dominant Role ◽  
Clay Mineralogy ◽  
Distribution Patterns ◽  
Weathering Profile ◽  
Nw Spain ◽  
Peraluminous Granites ◽  
Mineralogical Study ◽  
Different Grain Size

AbstractA geochemical and mineralogical study has allowed us to address the factors controlling distribution pattern, residence and behaviour of rare earth elements (REE) during kaolinization of Variscan granitoids in NW Spain. Mineral composition of the deeply weathered samples is dominated by kaolinite, with minor amounts of quartz, muscovite-illite, alkaline feldspar and traces of resistant minerals (rutile, ilmenite, zircon and monazite). Variable amounts of Si, Na, Ca, K, Rb, Cs, Ba, U and P were lost from the weathering profile, as a result of feldspars, mica and apatite breakdown, whereas Al, Fe, Ti, Zr, Th, Hf and REE were concentrated in the residual kaolin. Chondrite-normalized REE patterns of the kaolins show an overall enrichment of light REE (LaN/SmN = 1.22–2.53), heavy REE depletion (GdN/YbN = 2.42–15.10) and a strong negative Eu anomaly (Eu/Eu* = 0.11–0.25), probably inherited from the parent granite. Nevertheless, the normalization to the parent granite reveals some REE fractionation and increasing positive Eu anomalies with advancing weathering, in response to the breakdown of feldspars. Different grain-size fractions show similar REE distribution patterns, but differ in concentration levels. Although the fine fractions are the most important REE reservoir, there is no positive correlation with clay mineralogy. The correlative behaviour among P2O5, Th and REE in the <2 mm fraction suggests that monazite plays a dominant role controlling the REE budget in the weathering profile.

Recovery of rare earth elements adsorbed on clay minerals: II. Leaching with ammonium sulfate

2013 ◽  
Vol 131-132 ◽  
pp. 158-166 ◽  
Author(s):  
Georgiana A. Moldoveanu ◽  
Vladimiros G. Papangelakis
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Ammonium Sulfate ◽  
Clay Minerals

Plumbogummite-group minerals from Mull and Morvern

1970 ◽  
Vol 37 (292) ◽  
pp. 934-938 ◽  
Author(s):  
D. C. Bain
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Clay Minerals ◽  
Spectrochemical Analysis ◽  
X Ray Diffraction ◽  
Complex Composition ◽  
X Ray

SummarySandstones from Mull and Morvern, most of which are from the Greensand formation, have been shown by X-ray diffraction to contain minerals of the plumbogummite group in very small amounts in the < 1·4µm fraction. The minerals were concentrated by HF digestion of the clay minerals. X-ray spectrographic traces show concentrations of Sr, La, Ce, Yt, and Ba, and a semiquantitative spectrochemical analysis also shows a concentration of Ca and Pb and the presence of numerous rare-earth elements. Individual minerals, which have a complex composition and can not be assigned to any one named species, are disseminated throughout the rocks as particles with an estimated size of between 0·1 and 0·25µm.

Clay minerals control rare earth elements (REE) fractionation in Brazilian mangrove soils

CATENA ◽  
2022 ◽  
Vol 209 ◽  
pp. 105855
Author(s):  
Gabriel Ramatis Pugliese Andrade ◽  
Javier Cuadros ◽  
Jorge Marcos Peniche Barbosa ◽  
Pablo Vidal-Torrado
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Clay Minerals ◽  
Ree Fractionation ◽  
Mangrove Soils
Sign in / Sign up

Export Citation Format

Share Document