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.  

Geochemical characteristics and geologic significance of rare earth elements in oil shale of the Yan’an Formation in the Tanshan area, in the Liupanshan Basin, China

2021 ◽  
pp. 1-41
Author(s):  
Lianfu Hai ◽  
Qinghai Xu ◽  
Caixia Mu ◽  
Rui Tao ◽  
Lei Wang ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Oil Shale ◽  
Sedimentary Environment ◽  
Moderate Degree ◽  
Material Source ◽  
Icp Ms ◽  
Ree Distribution ◽  
Heavy Rare Earth Elements ◽  
Degree Of Differentiation

In the Tanshan area, which is at the Liupanshui Basin, abundant oil shale resources are associated with coals. We analyzed the cores, geochemistry of rare earth elements (REE) and trace element of oil shale with ICP-MS technology to define the palaeo-sedimentary environment, material source and geological significance of oil shale in this area. The results of the summed compositions of REE, and the total REE contents (SREE), in the Yan'an Formation oil shale are slightly higher than the global average of the composition of the upper continental crustal (UCC) and are lower than that of North American shales. The REE distribution pattern is characterized by right-inclined enrichment of light rare earth elements (LREE) and relative loss of heavy rare earth elements (HREE), which reflects the characteristics of crustal source deposition. There is a moderate degree of differentiation among LREE, while the differences among HREE are not obvious. The dEu values show a weak negative anomaly and the dCe values show no anomaly, which are generally consistent with the distribution of REE in the upper crust. The characteristics of REE and trace elements indicate that the oil shale formed in an oxygen-poor reducing environment and that the paleoclimatic conditions were relatively warm and humid. The degree of differentiation of REE indicates that the sedimentation rate in the study area was low, which reflected the characteristics of relatively deep sedimentary water bodies and distant source areas. The results also proved that the source rock mainly consisted of calcareous mudstone, and a small amount of granite was also mixed in.

scholarly journals Geochemical Implications of Rare Earth Elements in Terra Rossa in Tropical Karst Area: A Case Study in Northern Vietnam

2020 ◽  
Vol 10 (3) ◽  
pp. 858 ◽  
Author(s):  
Zhang Liankai ◽  
Ji Hongbing ◽  
Wang Shijie ◽  
Luo Gang ◽  
Liu Xiuming ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Chemical Weathering ◽  
Karst Area ◽  
Oxidation Condition ◽  
Terra Rossa ◽  
Northern Vietnam ◽  
Material Sources ◽  
Karst Areas ◽  
Tropical Karst

Research on weathered crusts on carbonate rock is essential for paleoenvironmental studies in karst areas. Terra rossa, widely distributed in tropical karst areas, has not been studied in terms of its material sources and geochemistry. Two typical terra rossa profiles on dolomite (SC profile located at Sang Cai, Hoa Binh province) and limestone (TG profile located at Tong Gia, Lao Cai province) in Northern Vietnam were selected to examine the geochemical characteristics and the evolutionary processes of rare earth elements (REEs). Chondrite and bedrock normalized patterns indicated that these two profiles are in situ weathering crusts, meaning they are the residual material remaining after chemical weathering of the lower carbonate rocks. The average value of total REE in the SC profile is 381.19 ppm, which is 30 times higher than the bedrock. In the TG profile, the value is 386.26 ppm, 13 times higher than the bedrock. Compared with the profiles in nearby subtropical areas in Southeast China, the REE enrichment coefficients of terra rossa in Northern Vietnam are much higher. The REE depletion was also different between the SC and TG profiles. The light and heavy REE fractionations in the SC profile are higher than in the TG profile. Paleoclimate inversion analysis shows that the SC profile experienced a stable oxidation condition, whereas the TG profile was subjected to several reducing environments since a weathering crust formed.

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.

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.

scholarly journals New insights about the rare earth elements (REE) mobility in river waters

2002 ◽  
Vol 173 (2) ◽  
pp. 147-160 ◽  
Author(s):  
Samuel Deberdt ◽  
Jérôme Viers ◽  
Bernard Dupré
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
River Waters ◽  
Geological Processes ◽  
Ree Distribution ◽  
Colloidal Matter ◽  
Ree Mobility ◽  
First Time ◽  
Colloidal Fraction ◽  
The Rare Earth

Abstract While the rare earth elements (REE) have largely contributed to the understanding of some internal geological processes, their use as tracers of superficial mechanisms (i.e., weathering and elements transport) remains tricky. This results from the poor knowledge we have of the REE distribution in the different fractions of solutions. Up to recently, the studies carried out on the REE behavior in continental aquatic systems were mainly based on the “paniculate” and “solution” fractions separated by an arbitrary filtration through a 0.20 or 0.45 μm pore size membrane. Some recent work has shown, using ultrafiltration experiments, that REE are mainly contained in the colloidal fraction (i.e., 0.20 μm - 1 nm). However, studies devoted to the control of REE by the colloidal matter, have essentially focused on the organic pool (i.e., humic substances). By contrast, the mineral colloidal pool has received little attention. In order to model these processes, we have developed a combined approach that consider (1) ultrafiltration experiments performed on a series of rivers located in Africa (Cameroon) and south America (Brazil, Venezuela) and (2) speciation calculations. This quantitative approach reveals, for the first time, that more than 60 % of the total REE in the solution of river waters is controlled by the mineral colloidal pool.

scholarly journals Determination of rare earth elements and other trace elements (Y, Mn, Co, Cr) in seawater using Tm addition and Mg(OH)2 co-precipitation

Talanta ◽  
2011 ◽  
Vol 85 (1) ◽  
pp. 582-587 ◽  
Author(s):  
Nicolas Freslon ◽  
Germain Bayon ◽  
Dominique Birot ◽  
Claire Bollinger ◽  
Jean Alix Barrat
Keyword(s):  
Trace Elements ◽  
Rare Earth ◽  
Rare Earth Elements ◽  
Co Precipitation

scholarly journals Distribution of rare-earth elements in rock-forming minerals of corundum-bearing rocks of the Khitoostrov deposit (North Karelia)

2021 ◽  
Vol 66 (4) ◽  
Author(s):  
Ekaterina Yu. Akimova ◽  
◽  
Sergey G. Skublov ◽  
◽  
◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Isotopic Composition ◽  
Mobile Belt ◽  
Positive Slope ◽  
Rock Formation ◽  
Ree Distribution ◽  
Lree Enrichment ◽  
Order Of Magnitude ◽  
The Difference

The distribution of rare-earth elements (SIMS method) in minerals from the rocks of the Khitoostrov occurrence (Belomorian mobile belt of Eastern Fennoscandia) was studied: corundum-bearing metasomatites with anomalous isotopically light oxygen and hydrogen and garnet amphibolites after gabbro with normal isotopic composition. The study was accompanied by estimates of P-T parameters of rock formation using multi-equilibrium thermobarometry (TWEEQU method). Temperatures calculated for garnet amphibolites after gabbro fall within the range of 730–770 ° C, pressures - 13–14 kbar; for corundum-bearing rocks, temperatures were 680–710 ° C, pressures - 6.5–7.5 kbar. Corundum-bearing rocks were formed at slightly lower temperatures and at significantly lower pressures than garnet amphibolites after gabbro. The REE distribution spectra in garnets from apogabbroic amphibolites are characterized by a clearly pronounced slope from light to heavy REE, while in garnets from corundum-bearing rocks they have a less pronounced positive slope, which is associated with a noticeable enrichment of garnets in LREE and an insignificant depletion of HREE. Calcium amphiboles from corundum-bearing rocks are significantly enriched in rare-earth elements as compared to amphiboles from garnet amphibolites after gabbro, especially LREE (by more than an order of magnitude) and, to a lesser extent, MREE. Plagioclases from corundum-bearing rocks are also enriched in LREE against the background of garnet amphibolites. Thus, in all the studied minerals of corundum-bearing rocks LREE enrichment is recorded. It isn’t manifested in the minerals of amphibolites and, obviously, isn’t related to the difference in P-T parameters of rock formation. Consequently, LREE was transferred by a specific fluid during mineral-forming processes, which led to the formation of metasomatites with an anomalous isotopic composition of oxygen and hydrogen.

scholarly journals Saprolitization’s Characteristics of Rare Earth Elements in Volcanic Regolith on Drill Core #65 in Western Sulawesi, Indonesia

2019 ◽  
Vol 7 (4) ◽  
Author(s):  
Shaban Godang ◽  
Arifudin Idrus ◽  
Fadlin, Bambang Priadi ◽  
Nurcahyo Indro Basuki
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Chemical Weathering ◽  
Gradual Increase ◽  
Drill Core ◽  
High Concentration ◽  
Adsorption Ability ◽  
Ti Oxides ◽  
Weathering Degree ◽  
The Relationship

The enrichment of Rare Earth Elements (REEs) in regolith depends on greatly number of chemical weathering degree, the ability of the ion-adsorption on clay, precipitation of REEs, minimum uptake by plants, and minor REE leaching out by lessivage. The degree of chemical weathering depends on the decaying of four base weathering elements (Mg, Ca, Na, K) in minerals and is relatively less dependent on the slow leaching of silica. Therefore, a study of regolith profile from weathering’s Adang Volcanics (western Sulawesi, Indonesia) is performed to understand the relationship between degree of chemical weathering, nature migration of REE and the characteristics of saprolitization REEs. The result of drill core samples shows the increasing of degree of chemical weathering (Degree of Saprolitization; DOS) is equal to gradual increasing of alumina by saprolitization, and has also gradual increase in Fe-Ti-oxides by ferruginization; furthermore, there is also a gradual enrichment of REEs occurred in the saprolite zone on Adang Volcanics regolith. The enrichment of REEs in the saprolite zones (E and B horizons) is 2.73 times (TREY = 2,579 ppm, in avg) compared to the parent mafic trachytic rocks (944 ppm) reveal the high adsorption ability on lateritic-ferruginous clay. The thickness of high concentration REEs (2,435 ppm, in avg) is starting from A to E, and B-horizon which is about 5 m. The ratio of LREE and HREE is 87.42% and 12.58%, respectively in parent rock which indicates the genesis of rare-earth is more influenced by replacement of Ca2+, Na+ and K+ in minerals of diopside, apatite and leucite/pseudoleucite rather than the substitution by zircon (Zr4+).

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