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Rare earth elements in sedimentary rocks: influence of provenance and sedimentary processes

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... (Vidal, 1994). Ces subdivisions reflètent des propriétés chimiques qui ne sont pas strictement identiques le long de la série des lanthanides en raison essentiellement de leur rayon ionique qui diminue progressivement du La au Lu McLennan, 1989). Ainsi, par exemple, les TRl sont moins solubles que les TRL en milieu acide et organique Duddy, 1980 ;Braun et al., 1993). ...
... À Kaya 1, des enrichissements en TRL sont observés de manière plus ou moins intense dans toute la partie inférieure du profil, de 8,3m à sa base, aussi bien dans les roches totales que dans les fractions fines, avec généralement des fractionnements plus intenses dans ces dernières ( Figure 10.3, Figure 10.4). On remarque aussi que les roches totales de la saprolite McLennan, 1989 ...
... Variation des teneurs en La, Ce et Lu par rapport au Th en fonction de la profondeur dans les roches totales des profils Kaya 5 et Kaya 1. Rapports normalisés à la roche mère (Ln/Th = 1 pour la roche mère) Ce, il est enrichi par rapport au Th dans la cuirasse et à 6m, dans les argiles bariolées(Figure 3.3). Le comportement singulier du Ce s'explique par le fait qu'il passe de l'état Ce 3+ à l'état d'oxydation Ce 4+ en conditions oxydantes, alors que toutes les autres terres rares restent sous forme Ln 3+(McLennan, 1989). Sous sa forme oxydée, le Ce est très insoluble et un fractionnement apparaît dès lors que les autres lanthanides sont mobilisés. ...
Thesis
Les interactions eaux-roches au sein des profils d’altération sont à l’origine de flux d’éléments chimiques sous forme dissoute ou particulaire, allant des continents vers les océans. Les latérites couvrant un tiers de la surface des continents et leur mode de formation étant discuté, on se propose d’étudier de tels profils afin d’en retracer la formation et l’évolution et d’y rechercher les processus d’altération actuellement actifs. Le matériel étudié est constitué de roches totales ainsi que de fractions argileuses fines (< 0,2μm), matériel privilégié pour l’enregistrement des événements récents. L’approche combine minéralogie, géochimie analytique et géochimie isotopique. On s’intéresse tout particulièrement à l’apport des déséquilibres 238U-234U-230Th à la caractérisation des mobilités récentes. Les deux latérites étudiées sont une ferricrète du Burkina Faso et un latosol du Cameroun. Les horizons pétrographiques constitutifs des latérites semblent dériver de conditions d’altération différentes de la roche mère et non pas d’un processus progressif et continu d’altération. L’origine autochtone des cuirasses ferrugineuses est appuyée par des arguments minéralogiques et géochimiques. Les éléments chimiques sont remobilisés et redistribués lors de l’évolution des profils, comme le montre par exemple la distribution des lanthanides, ce qui perturbe aussi les signatures des systèmes isotopiques à longues périodes. Des mobilités récentes, voire actives, sont mises en évidence par les déséquilibres 238U-234U-230Th en tout point des profils. Les caractéristiques des mobilisations d’U peuvent être estimées à partir d’équations de désintégration radioactive pour des systèmes simples affectés par une mobilisation simple d’U et évoluant ensuite en système fermé. Dans le cas d’un système ouvert et soumis à la fois à un lessivage et à un apport d’U, une modélisation appropriée permet d’évaluer les caractéristiques des mobilités d’U (flux, variations). Les déséquilibres 238U-234U-230Th se révèlent être un outil adapté à la mise en évidence et à la caractérisation des mobilités chimiques récentes dans les profils d’altération. Il apparaît que des processus multiples affectent actuellement l’ensemble des horizons des latérites et participent donc aux flux chimiques issus de ces profils.
... Some immobile elements such as REE, HFSE (for example, Zr, Ti, Th, and Y), and transition elements (for example, Sc, Cr, and Co) are least fractionated during sedimentation, and thus their abundances or ratios have been used to decipher the source nature of metamorphosed sediments (Taylor and McLennan, 1985). The weakly fractionated HREE patterns of most samples, together with their significant Zr-Hf depletion relative to upper continental crust ( fig. 4), suggest a simple recycling without obvious enrichment of heavy minerals such as zircon and monazite (McLennan, 1989). The Th/Sc ratio is also a good indicator of source composition, since Th and Sc are enriched respectively in felsic and basic rocks and this ratio would basically remain constant during sedimentary recycling. ...
... The Th/Sc ratio is also a good indicator of source composition, since Th and Sc are enriched respectively in felsic and basic rocks and this ratio would basically remain constant during sedimentary recycling. The Zr/Sc ratio, however, would increase significantly during recycling as a result of zircon enrichment (Mclennan, 1989). Although the five samples deviate from the differentiation line due to the significant Zr depletion, in the Zr/Sc versus Th/Sc diagram, they form a roughly positive trend showing compositional variation but not sediment recycling ( fig. ...
... Cerium may have a valency of +3 or + 4, whereas europium may have a valency of +2 or + 3 [1]. The rare earth elements show a decrease in their ionic radii [4,5], K-P reported in Kabata-Pendias [3], and UCC reported in Rudnick and Gao [6]. (ix) bastnaesite (REE) [4]. ...
... The rare earth elements show a decrease in their ionic radii [4,5], K-P reported in Kabata-Pendias [3], and UCC reported in Rudnick and Gao [6]. (ix) bastnaesite (REE) [4]. Mineral and soil assemblies typically show greater LREE concentrations than HREE; however, the LREE/HREE ratio may vary with zircon abundances. ...
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Rare earth elements are critical elements in the modern economy. Mining of rare earth elements has significantly intensified in the last several decades and studies of the environmental impact are in their infancy. In trace amounts, rare earth elements may support plant growth and development. At greater concentrations, rare earth elements are increasingly recognized as having a degree of mammalian toxicity; however, the mammalian toxicity potential may not be as acute as that for some heavy metals. The toxicity of rare earth elements requires detailed research to showcase toxicity thresholds for a wide range of ecosystem health. This study reveals case studies demonstrating that investigators rely on pollution indices, which do indicate that mining and ore processing possess environmental challenges. Further research has been identified to evaluate pollution indices for rare earth elements, especially concentrating on their biological availability.
... When normalized to the upper continental crust (UCC) [60] and plotted on a spider diagram, the trace elements showed consistent distribution patterns in all samples, indicating that the sources of the oil shale of the detrital mineral matrix barely changed. Meanwhile, the sample/UCC is used to represent the enrichment coefficient, and a sample/UCC of more than 1 represents enrichment while a sample/UCC of less than 1 represents a deficit. ...
... Meanwhile, Eu and Tm show obvious negative anomaly characteristics (Figure 7). When normalized to the upper continental crust (UCC) [60] and plotted on a spider diagram, the trace elements showed consistent distribution patterns in all samples, indicating that the sources of the oil shale of the detrital mineral matrix barely changed. Meanwhile, the sample/UCC is used to represent the enrichment coefficient, and a sample/UCC of more than 1 represents enrichment while a sample/UCC of less than 1 represents a deficit. ...
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Oil shale is a crucial unconventional energy source to supplement conventional oil and gas. The oil shale in the Maoming Basin of China has excellent resource potential. In this study, through systematic geochemical testing, the industrial quality and geochemical characteristics of oil shale are revealed, and the hydrocarbon generation potential of oil shale, the parent rock type, and the tectonic setting of the source area are discussed. It is comprehensively assessed that Maoming oil shale has a medium-oil yield (avg. 6.71%) with high ash content (avg. 76.1%), a high calorific value (avg. 7.16 M J/kg), and ultra-low sulfur (avg. 0.54%). The mineralogical compositions primarily consist of clay minerals and quartz, and barely pyrite. Maoming oil shale is in an immature evolution stage, with high TOC and I-II1 kerogen type, and could be considered an excellent hydrocarbon source rock. The chemical index of alteration (CIA), the index of chemical variability (ICV), and the Th/U ratio indicate that the Maoming oil shale parent rock area is strongly weathered. Multitudinous geochemical diagrams also show that the oil shale was mainly derived from Late Cretaceous felsic volcanic rock and the granite zone, and the tectonic setting was a continental island arc environment related to the active continental margin. This is consistent with the tectonic history of southern China in the Late Cretaceous.
... Rare earth elements (REEs) are of significant interest in geochemical studies as tracers of sources, processes, and physicochemical conditions because their absolute concentrations and relative distributions are less susceptibile to weathering, denudation, transport, sedimentation, diagenesis, and metamorphism (Taylor and McLennan, 1985). The REE composition and distribution in sediments are mainly controlled by the characteristics of the original rocks (Klaver and Weering, 1993;Li et al., 2013;McLennan, 1989;Vital et al., 1999); therefore, lanthanides can serve as indicators of sources as well as chemical and physical conditions and processes (Aksentov and Sattarova, 2016;Li et al., 2013;Liu et al., 2018;Maslov et al., 2013;Su et al., 2017;Yang et al., 2002Yang et al., , 2014Ye et al., 2019). Several studies have identified the factors (source rock composition, grain-size, and mineralogy) that control the REE distribution in surficial sediments (Borrego et al., 2005;Byrne and Kim, 1990;Cullers et al., 1987;Jung et al., 2012;Liu et al., 2016;López-González et al., 2012;Maeda et al., 2007;Prego et al., 2009;Rea and Hovan, 1995;Yang et al., 2002;Zhang et al., 2012). ...
... Several studies have identified the factors (source rock composition, grain-size, and mineralogy) that control the REE distribution in surficial sediments (Borrego et al., 2005;Byrne and Kim, 1990;Cullers et al., 1987;Jung et al., 2012;Liu et al., 2016;López-González et al., 2012;Maeda et al., 2007;Prego et al., 2009;Rea and Hovan, 1995;Yang et al., 2002;Zhang et al., 2012). It is known that clay and silt fractions are usually enriched by REEs, unlike sand fractions, owing to dilution by quartz and carbonate minerals (McLennan, 1989;Taylor and McLennan, 1985;Vital et al., 1999). Investigations of marine sediments have revealed that REE patterns in sedimentary systems are influenced by both the depositional environment including water mass advection and mixing (Laukert et al., 2017;Murray et al., 1990Murray et al., , 1992 and diagenetic processes (Milodowski and Zalasiewicz, 1991;Murray et al., 1992). ...
... In these transitional scenarios, the analysis of these elements make it possible to ascertain the effect of past and present-day anthropic actions on the sediments extracted in continuous cores, by studying vertical and temporal variations of: i) their original concentrations (Benmhanned et al., 2021;Mejjad et al., 2022); ii) their normalized values and global patterns, using the North American Shale Composite (NASC; Taylor and McLennan, 1985), the Post Archaean Australian Shale (PAAS; McLennan, 1989) or chondrites values as backgrounds Liu et al., 2021;Chi et al., 2021); iii) different ratios between the REE groups (e.g. LREE/HREE, HREE/LREE) or fractionation between them using other ratios [e.g. ...
... In these samples, detection limits are between 0.01 ppm and 0.2 ppm. The PAAS-normalized values (Post Archean Australian Shale; Nance and Taylor, 1976;McLennan, 1989) have been used to detect changes in their distribution patterns due to natural fractionation processes. This method is usual if REE are used as environmental tracers (Rao and Chakraborty, 2016;Brito et al., 2016). ...
Article
Multivariate analyses have been applied to the REE contents of three cores collected in the Tinto estuary, SW Spain, an extremely polluted area. Results indicate an extremely correlation between all REE, which behave as a single variable. A slight natural pollution peak and three anthropogenic pollution peaks are identified, related with the first mining activities, the Roman period and a recent intensive mining accompanied by a heavy industrial pollution. In all these peaks, the increase of Cu is parallel to that of MREE, which are configured as the best indicators of pollution among REE. Statistical analyses clearly differentiate four groups, each consisting of samples from different environments. Although grain size and this strong pollution alter the study of REE as environmental indicators, it is possible to recognise groups of samples with a common origin or to identify the surface extent of a given pollution peak.
... REE and Y concentrations are reported in parts per million. We used the reference material of McLennan (1989) for normalization of REE+Y concentrations and all samples were normalized to Post-Archean Australian Shale (PAAS, see McLennan 1989;Pourmand et al. 2012). The Excel program was used to compute the data. ...
... = 3Ce N /(2La N +Nd N ), Y anom. = 2Y N / (Dy N +Ho N ), La N /Nd N (N in subscript refers to normalization of concentration against the shale standard PAAS, see McLennan 1989), and the Y/Ho mass ratio. The Y/Ho mass ratio is defined by some authors as the Y anomaly (Tostevin et al. 2016). ...
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Machalski, M., Olszewska-Nejbert, D. and Wilmsen, M. 202X. Stratigraphy of the Albian-Cenomanian (Creta-ceous) phosphorite interval in central Poland: a reappraisal. Acta Geologica Polonica, XX (X), xxx-xxx. Warszawa. Several closely-spaced phosphorite beds stand out at the Albian-Cenomanian transition in the mid-Cretaceous transgressive succession at the northeastern margin of the Holy Cross Mountains, central Poland. They form a distinctive condensed interval of considerable stratigraphical, palaeontological, and economic value. Here, we correlate the classical section at Annopol with a recently investigated section at Chałupki. We propose a new stratigraphic interpretation of the phosphorite interval, based on lithological correlations, Rare Earth Elements and Yttrium (REE+Y) signatures of phosphorites, age-diagnostic macrofossils, and sequence stratigraphic patterns. This interval has long been considered as exclusively Albian in age. However, new macrofossil data allow us to assign the higher phosphorite levels at Annopol and Chałupki, which were the primary target for the phosphate mining, to the lower Cenomanian. In terms of sequence stratigraphy, the phosphorite interval encompasses the depositional sequence DS Al 8 and the Lowstand System Tract of the successive DS Al/Ce 1 sequence. The proposed correlation suggests that lowstand reworking during the Albian-Cenomanian boundary interval played an important role in concentrating the phosphatic clasts and nodules to exploitable stratiform accumulations. Our conclusions are pertinent to regional studies, assessments of natural resources (in view of the recent interest in REE content of the phosphorites), and dating of the fossil assemblages preserved in the phosphorite interval. On a broader scale, they add to our understanding of the formation of stratiform phosphorite deposits.
... Whole-rock geochemistry of sedimentary rocks is one of the essential tools for provenance analysis of sedimentary basins, because rare earth elements (REEs) and high field strength elements (HFSEs, e.g., Nb, Ta, Zr, Hf and Th) are relatively stable during sediment transport, deposition and diagenesis (McLennan, 1989(McLennan, , 1993Bock et al., 1998). Normalizing REEs to chondrite and other trace element concentrations to upper crust provides convenient visualization of the data. ...
... Petrography, rare earth and trace elements, and detrital zircon U-Pb ages of the sediments are applicable tools for provenance analysis (Dickinson and Suczek, 1979;McLennan, 1989McLennan, , 1993Dickinson and Gehrels, 2010). The textures of the sixteen sandstone samples vary from Tang et al. ...
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The Permian clastic sediments in the Mahu sag offer outstanding conditions to test the control of tectonism and paleoclimate on sedimentation in a rift basin. A synthesis of petrological and geochemical analyses of sandstones, zircon U-Pb geochronology of granitic conglomerates, and principal component analysis have been used to investigate the source composition and chemical weathering indices. The rare earth and trace element compositions of 16 sandstone samples are consistent with first cycle sources from the Carboniferous-Lower Permian mafic and felsic igneous rocks in West Junggar. Lower Permian sandstones contain abundant volcanic lithic clasts and plagioclase grains, and have high Na 2 O, CaO, Sr and V, suggesting a coeval proximal volcanic source in Central West Junggar during the syn-rift stage. Middle Permian sandstones consist of trachyte and rhyolite clasts, and quartz and albite grains, and show a gradual increase of Th, U and SiO 2 , indicating an expansion of source areas to more distant Southern and Northern West Junggar during the post-rift stage. In the Lower Triassic, an abrupt increase in the percentages of quartz and K-feldspar, as well as the zircon U-Pb geochronology of granite-clast conglomerates (290-330 Ma), all indicate regional uplift and unroofing of Carboniferous-Permian granitic plutons in West Junggar during the tectonic inversion stage at the Permian-Triassic boundary. Various chemical weathering indices indicate cold and arid climate conditions during the early Permian, followed by a transition to warm and humid climatic conditions. Comprehensive analysis of petrography and geochemistry sheds a new light for studying the source-to-sink evolution of a rift basin, and has further implication for paleoclimate fluctuation and change.
... However, vertical mobilization and redistribution of REEs were not observed in a soil profile, most probably due to the short residence time of water. LREE is preferentially enriched over HREE in soil has been proposed by several authors (Braun et al., 1993;Li et al., 2022;Li et al., 2017;McLennan, 1989;Nesbitt, 1979;Sanematsu et al., 2013;Yusoff et al., 2013) and are described as follows: (i) sharp LREE distributions are attributed to the enrichment of a large ion lithophile element caused by the partial melting of crustal rocks (McLennan, 1989;Wei et al., 2013), (ii) there are no significant HREE fractionations, (iii) the abundant occurrence of LREEs minerals (allanite, apatite, and REEs fluorocarbonate) relative to HREEs bearing minerals (titanite and zircon, Sanematsu et al., 2013), and (iv) selective ion-adsorption of LREE relative to HREE by clay minerals (Li et al., 2022;Li et al., 2017). fractionation is strongly pH-dependent and effectively occurs under pH 6.2-7.5. ...
... However, vertical mobilization and redistribution of REEs were not observed in a soil profile, most probably due to the short residence time of water. LREE is preferentially enriched over HREE in soil has been proposed by several authors (Braun et al., 1993;Li et al., 2022;Li et al., 2017;McLennan, 1989;Nesbitt, 1979;Sanematsu et al., 2013;Yusoff et al., 2013) and are described as follows: (i) sharp LREE distributions are attributed to the enrichment of a large ion lithophile element caused by the partial melting of crustal rocks (McLennan, 1989;Wei et al., 2013), (ii) there are no significant HREE fractionations, (iii) the abundant occurrence of LREEs minerals (allanite, apatite, and REEs fluorocarbonate) relative to HREEs bearing minerals (titanite and zircon, Sanematsu et al., 2013), and (iv) selective ion-adsorption of LREE relative to HREE by clay minerals (Li et al., 2022;Li et al., 2017). fractionation is strongly pH-dependent and effectively occurs under pH 6.2-7.5. ...
Article
The mineralogical and geochemical parameters on soil, waste, and tailings are major components for water quality assessments because they dictate the behavior of the chemical composition and water–rock interactions. Arsenic and trace metal contamination occasionally occurs because of the oxidation of arsenic-rich minerals and hydrothermal alteration or because of anthropogenic influences, such as industrial mining activity. This study aimed to understand the characteristics of tailings, soils, surface water, and groundwater to evaluate the possible geochemical dispersion of metals employed in tailing storage facilities. A study site at the former epithermal Au–Ag mine in Central Kalimantan, Indonesia, was selected because it was suitable for investigating the geochemical behavior of trace metals in water and solid samples and their possible contribution to metal contamination in tropical regions. A detailed study of the tailings comparing mineralogical and geochemical analysis indicates that the presence of unaltered, intermediate, and oxidized zone within the tailings can be related to the sulfides alteration indices (SAI). These zones include an unoxidized zone in the submerged areas where sulfides, including pyrite with less sphalerite and galena, remain fresh. In the intermediate zone, pyrite starts to change to iron oxyhydroxide. The SAI parameters from the intermediate zone, extending 50 cm below the tailing surface, indicate that only a few grains of pyrite in this zone are weakly altered and are capped by a thin (<10 μm) iron oxyhydroxide. The oxidized zone is indicated by traces of remaining pyrite and iron oxyhydroxide as the primary mineral. Heavy metals and rare earth elements from tailings storage facilities were scavenged from the soil solutions by groundwater. The stable isotopes of oxygen, hydrogen, and dissolved rare earth elements (REEs) were used as natural tracers in systems affected by acid mine drainage. The results showed that stable isotope and rare earth elements data do not support contamination between the surface and groundwater. This study found that the oxidation of ferrous iron to ferric ion and precipitation of Fe-oxyhydroxides in soil and water has a close spatial relationship with rare earth elements, which are concentrated only in intermediate and oxide zones.
... The burial and compaction processes can change the composition of framework grains, so the petrographic studies derived from them may not always reflect the true crustal setting. Therefore, geochemical composition is crucial to understanding the source rock and tectonic settings as a supplement to petrographic approaches (Ahmad et al., 2022;Bhatia, 1983;Khan et al., 2016;McLennan, 1989;Nesbitt & Young, 1982;Roser & Korsch, 1986). Therefore, many researchers have used sandstone geochemistry to figure out the provenance and tectonic setting of a region (Bhatia, 1983;McLennan, 1989;Nesbitt & Young, 1989;Roser & Korsch, 1986). ...
... Therefore, geochemical composition is crucial to understanding the source rock and tectonic settings as a supplement to petrographic approaches (Ahmad et al., 2022;Bhatia, 1983;Khan et al., 2016;McLennan, 1989;Nesbitt & Young, 1982;Roser & Korsch, 1986). Therefore, many researchers have used sandstone geochemistry to figure out the provenance and tectonic setting of a region (Bhatia, 1983;McLennan, 1989;Nesbitt & Young, 1989;Roser & Korsch, 1986). However, the chemical weathering processes play a significant role in changing the original mineralogical composition of rocks. ...
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Detrital mineralogy and geochemical (major element oxides) approach, with the support of heavy mineral and clay mineralogical study, the siliciclastic rocks of Geku Formation of Yinkiong Group, Eastern Himalaya have been studied to understand their compositional variations, provenance of sediments, and to decipher the tectonic settings. Sandstones are quartz-dominated, with feldspar and rock fragments in a modal average ratio of Q79F10L10, as shown in the petrographic examination. Litharenite, wacke, and Fe-sand types of sandstone have been identified using geochemical approaches. Tectonic discriminant diagrams based on petrographic observations and major elements oxides have inferred that the studied sandstones were deposited in a passive continental setting, and sediments were derived from igneous, sedimentary, and metamorphic sources, i.e., plutonic (intermediate to mafic), quartzose sedimentary and gneissic provenance. The Himalayan affinity rocks in the northern part of the basin, which include mafic igneous sources such as Abor volcanics, are the potential source. The palaeoweathering indices have shown that the sediments were derived by moderate-to-intense chemical weathering and deposited nearby to the source without extensive recycling. The SiO2/Al2O3 and index of chemical variability (ICV) have indicated that the rocks are not very mature in terms of composition, and that recycling is moderate to low. The Geku Formation was formed by uplifted Himalayan orogeny rocks deposited in a fore-arc basin during the India–Asia collision.
... The positive correlations among the other trace elements with their respective correspondents imply some geochemical coherence. [55]. ...
... (a) Plot of Bateka iron deposits in Ce/Ce*-Pr/Pr* binary diagram after [68] modified from [79]). (b) Source rock discriminating diagram of La vs. Th (after [55] for the Bateka iron prospect. (c) Ce/Ce*-Nd plot; the dividing line between anoxic and oxic is after [71]. ...
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The Bateka iron prospect is situated in the lower Dja Serie which constitutes one of the Proterozoic cover series of the Congo Craton in Cameroon. Field mapping surveys for banded iron formations (BIFs) was carried out in this area, and samples submitted for quantitative X-ray diffractometry and Inductively Coupled Plasma-Mass Spectrometry analyses. The objective of this study was to constraint petrography, mineralogy and geochemical composition to delineate the petrogenesis and the origin of Bateka banded iron formation. Bateka BIFs are slightly to moderately magnetic, laminated, exhibit macroband texture, and are composed of hematite (16.9-43.9%), magnetite (1.5-5.3%), goethite (1.4-23.8%) and amorphous (53.2-54%). They show Fe 2 O 3 (90.9-99.76%), large ion lithophile elements and transition metals enrichment, and depletion for the rest of major oxides and high field strength elements. PAAS-normalization REEs are fractionated (La N /Yb N = 0.02-4.98) and the patterns show light rare earth elements depletion (La N /Sm N = 0.07-0.80) relative to heavy rare earth elements (Gd N /Yb N = 0.61-7.41) and a positive Eu anomaly (Eu/Eu* = 1.05-1.83). The chemical composition of the Bateka iron prospect is similar to Algoma-type BIFs and based on the high Fe 2 O 3 content, this deposit is classified as oxide facies. The overall composition of Bateka iron prospect is in accordance with the hydrothermal and Red Sea deposits and have been deposited close to the distal position. The Bateka BIFs have the composition of peraluminous sediments, they derived from Archean volcano-sedimentary materials. Their sediment provenance indicates mature pelitic greywacke that were deposited in an oceanic island arc environment from basaltic and andesitic detritus setting, where conditions were anoxic with fast sedimentation.
... The high Th/Sc and LREE/HREE values of the Pg Sequence claystones correspond to an increase in the abundance of detrital Th-bearing minerals relative to Sc-rich minerals (e.g., pyroxene and smectite - Wilson, 2004;Salminen et al., 2005). Th and Sc are useful for determining variations in sediment provenance in sedimentary rocks due to their insolubility and immobile character during transport, diagenesis, weathering and metamorphism (e.g., Taylor and McLennan, 1985;McLennan, 1989;Condie, 1993;McLennan et al., 1993;Hofer et al., 2013). The Th/Sc ratio is particularly useful for distinguishing derivation from mafic and felsic source areas because Th is more abundant in felsic crustal rocks and Sc is generally more abundant in mafic rocks (McLennan, 1989). ...
... Th and Sc are useful for determining variations in sediment provenance in sedimentary rocks due to their insolubility and immobile character during transport, diagenesis, weathering and metamorphism (e.g., Taylor and McLennan, 1985;McLennan, 1989;Condie, 1993;McLennan et al., 1993;Hofer et al., 2013). The Th/Sc ratio is particularly useful for distinguishing derivation from mafic and felsic source areas because Th is more abundant in felsic crustal rocks and Sc is generally more abundant in mafic rocks (McLennan, 1989). Most Pg Sequence claystones have Th/Sc values above 0.95 (baseline of the blue colour fill - Fig. 6), maximum values of 1.5 and average values of 1.05, which are interpreted to mark an increase in the contribution of detrital material derived from a predominantly felsic crustal source area. ...
Article
The Cretaceous and Paleogene marine sedimentary rocks that crop out along southern coastal Tanzania have been the focus of the Tanzanian Drilling Project (TDP) since 2001. The comprehensive lithological and chronostratigraphic examination of over forty shallow cores by the TDP culminated in the formal definition of the Kilwa Group: a claystone-dominated succession comprising five formations deposited in middle to outer shelf and upper slope marine environments along a passive continental margin. Onshore, the TDP has cored important palaeoclimatic events within the Kilwa Group. Offshore, the group forms the reservoir and seal of several gas fields discovered in southern Tanzania. The formations of the Kilwa Group cored onshore, have been differentiated from each other largely by variations in subsidiary lithologies (sandstones and limestones), rather than by diagnostic characteristics of their dominant lithology (olive grey claystone). To test and refine the lithostratigraphy of the Kilwa Group, a forensic examination of the claystones using whole-rock inorganic geochemistry, mineralogical analysis and detailed biostratigraphy, is employed in this study. 1210 core samples collected from 20 onshore TDP boreholes and 185 cutting samples acquired from three wells located in offshore in Blocks 1 and 4 are examined by inductively-coupled plasma optical emission spectroscopy and mass spectrometry, whole-rock and clay fraction X-ray diffraction analysis and heavy mineral analysis using Raman spectroscopy. The different methodologies are used to produce a claystone-based chemostratigraphic framework for the Kilwa Group that comprises three sequences, five packages and six units, and links the shallow subsurface rocks onshore to the deep subsurface stratigraphy offshore. The multidisciplinary geochemical and mineralogical approach reveals that variations in detrital quartz, feldspars (K and Na), heavy minerals, phosphatic minerals and clay minerals (particularly illite, smectite and kaolinite) are key for defining the claystone-based stratigraphy of the Kilwa Group. The variation in the abundance of these mineral through time highlight mostly temporal changes in depositional environment, chemical weathering and sediment provenance that occurred in Tanzania during the Cretaceous and Paleogene. Integration of the chemostratigraphic framework with detailed biostratigraphic information from the study sections and comparison with the published lithostratigraphy of the Kilwa Group onshore reveals that all three stratigraphic schemes are in broad agreement. Nevertheless, refinements are proposed based on the new chemostratigraphic results. It is suggested here that the top and base of the Kilwa Group is older than previously reported (base–Albian and intra-Rupelian, respectively, rather than the end of both stages) and in most cases, the geochemical data suggests that most of the Kilwa Group formations, as cored onshore, are thinner than formerly proposed. Only the Masoko and Lindi Formations are interpreted to be thicker than previously defined by the TDP.
... Major elements have been used to define the tectonic settings of different sedimentary suites (Kumar et al. 2017). Major oxides, such as Al 2 O 3 and TiO 2 , can be used for interpretation of the source and tectonic setting; because during depositional processes, Al and Ti have very low mobility and sedimentation usually involves minerals or rock fragments rather than single elements (McLennan 1989). The major and trace immobile elements, such as Al, Fe, Ti, Th, Sc, Co, Zr, and REE, present in the river bed and suspended loads are a useful indicator of the source of sediments/sedimentary rocks. ...
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The purpose of this study is to use the geochemical analysis of recent sediments from the Rayen River (length of about 25 km), located in the Central Iranian zone and Urumieh-Dokhtar Magmatic Belt, to interpret their compositional maturity, chemical weathering, source rocks, and tectonic setting. Geochemical analysis (major and trace elements) of ten sediment samples suggests that mafic and intermediate igneous rocks are the sources of these sediments. Based on discriminant function, binary and ternary diagrams, it is concluded that the tectonic setting of the study area is similar to a continental island arc. The Chemical Index of Alteration (CIA) ranges between 50 and 57, suggesting low-to-moderate chemical weathering that reflects tectonic activity, erosion, and rapid deposition under arid climatic conditions, which gradually increased through time in the source areas. The ICV (Index of Compositional Variability) values show that these sediments have low compositional and mineralogical maturity. It is also shown that the bed load in the Rayen River has a mixed source from undifferentiated volcanic rocks. The data obtained from both petrography and geochemical analysis, which reflect the tectonic and climatic conditions in the study area, can be used as a guide for the interpretation of similar ancient sedimentary records.
... be chosen based on site-specific criteria and according to the purpose of assessment. Rare earth elements (REE) are suitable for geochemical studies and provenance composition analysis of the material due to their stability against biogeochemical processes, no fractionation during sedimentation, low solubility, and relative immobile in surface and aqueous environments (McLennan 1989;Fonseca et al. 2021). For this study, samarium (Sm) was chosen as the normalizer as it is an element that is not affected by surface geochemical processes and has high analytical precision and low detection limit with the AANI technique. ...
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Purpose The main objective of the study was to assess the environmental quality status of the sediments of eleven Patagonian lakes regarding the concentrations of five trace elements, evaluating the influence of volcanic activity and water and sediment parameters on element concentration and distribution. Materials and methods Surface sediment samples from 11 lakes were collected at different depths for granulometric analysis, organic matter (OM) contents, and determination of As, Br, Cr, Hg, Ni, and Zn concentrations. Physicochemical variables of the water column were also measured. The quality of the sediments and the potential ecological risks were assessed by comparing the concentrations of elements with local and global geochemical background values and with consensus-based sediment quality guidelines and through the calculation of environmental quality indices (enrichment factor and index of geo-accumulation). Results and discussion A higher proportion of sand with a lower %OM characterized the surface sediments in lakes close to the volcanic complex (PCCVC), while a higher proportion of silt–clay with a higher %OM was found in sediments from lakes furthest from the PCCVC, consistent with the expected gradient of volcanic ash size deposited in the lakes. The presence of volcanic ashes in sediments seems to dilute trace element concentrations of samples, having sediment samples from lakes near the PCCVC lower concentrations of Br, Cr, and Ni than the furthest lakes. Environmental quality indices indicated minimal to moderate enrichment/contamination in sediments from deep lakes near the PCCVC and significant to high enrichment/contamination in sediments from lakes far from the volcano and in the shallower lakes. The concentrations of As, Cr, and Ni in six of the 11 sampled lakes are at levels considered harmful for sediment-dwelling organisms according to north hemisphere guidelines. Conclusions Despite being in a protected area, the sediments of some Patagonian lakes have concentrations of potentially toxic elements at levels that may cause pollution and be of risk to the aquatic biota, with the volcanic ashes acting to dilute this effect.
... The REE concentrations were normalized against the Post-Archean Australian Shale PAAS (McLennan, 1989). The Gd anomaly (Gd/Gd*) N , i.e., the excess of it in groundwater, was calculated using interpolation of the normalized concentration (suffix N, subscribed) of two REE neighbors, samarium (Sm) and terbium (Tb), using the following equation: ...
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The use of environmental tracers brings comprehensive benefits to the management of water resources since it helps to prevent their pollution, minimize public health risks, and thus reduce the impact of urbanization. In Brazil, the Guarani Aquifer System (GAS) has strategic and environmental importance, making its preservation and sustainable exploitation mandatory. The present study aimed at evaluating sources of contamination in the GAS using the combination of geochemical data and two environmental tracers: nitrate isotopes (¹⁵NNO3 and ¹⁸ONO3) and one rare earth element (Gadolinium—Gd). For that, five wells—four exploiting the GAS and one the Bauru Aquifer System (BAS)—were selected to discuss the human inputs in groundwater used for public supply in an urban area. Traditional physicochemical analyses were conducted for six campaign samplings and nitrate monitoring for this period was evaluated on a time scale, also considering the accumulated rainfall. Besides that, the double isotopic method (DIM), e.g., δ¹⁸ONO3 e δ¹⁵NNO3, was applied to identify the fractionation and enable the distinction of the nitrate contamination source. In addition, the determination of anomalies of Gd, a wastewater-derived contaminant, was also performed to verify recent human inputs in groundwater. The results show that the local existence of nitrate in the GAS and BAS—even at low concentrations (values from 0.26 to 6.68 mg L⁻¹)—originated from anthropogenic inputs (septic waste), as indicates the typical isotopic signals ratio in the isotopic approach. Associated with that, the evaluation of Gd permitted the separation of groundwater samples into older or more recent leakages. The use of environmental tracers to assess anthropogenic inputs in groundwater reiterates the importance of adopting more effective protection strategies for water resources management systems, in order to prevent contamination. Graphical Abstract
... Above, the influx of terrigenous input, indicated with high Al, Fe, Si, and Ti values, characterized the top of the section where phosphorous disappeared in the water column. The REE patterns, normalized to post-Archean Australian Shale (PAAS; Ref. [39]) are shown in Figure 9. The REE patterns show consistent negative Ce anomalies in the analyzed samples, reflecting similar results from previous studies [40,41]. ...
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Petrological, geochemical, and biostratigraphical investigations have been conducted on seventy-nine samples from four selected sections in Jordan to understand the factors that influenced the enrichment and deposition of massive phosphorite deposits. The calcareous nannofossil marker species Broisonia parca constrica and Reticulofenestra bisecta, from the assigned sections 1 and 2 (Hawar and Al Dhahikiyya), were indicative of the Campanian and Eocene periods, respectively. The enrichment of some ecological marker species such as Kamptnerius magnificus indicates that there were cold periods during phosphate precipitation. All thin sections of the phosphate samples are of grain-stone and packstone textures and are composed of skeletal fragments and peloids. Skeletal fragments appeared to be the main component of Hawar phosphates with the existence of peloids, while peloids were the component in sections 2 and 3 (section 3: Al Hisa). At least three intervals of high phosphorous values appeared in the Hawar section, showing variations in the Ca and Nd isotopes and in the terrigenous inputs. Four periods of phosphate enrichment are observed in Sections 2 and 3. These are deep water circulation periods of the early and late Campanian period, interrupted by two periods of submarine and continental weathering. Deep water circulation was initiated during cooling in the Campanian period and indicated by high phosphorous and Ca isotope components and a decline in terrigenous indicators (Al, Si, Ti, and Fe). Submarine weathering during warmer deep-sea periods is indicated by a rising Nd isotope ratio when many of the igneous provinces were subjected to weathering. Continental weathering took place in the warmer periods, with the hydro-logic cycle and enhancement of terrigenous indicators (Al, Si, Ti, and Fe) being observed. The effect of the hydrologic cycle was at its highest in the south during the Campanian period and in the Eocene, as both represented shallower settings.
... The Mo concentrations of the microbial and transitional zone fabrics are similar, but higher than that of the fine spar fabric (Table 1; Figure 2I). Rare earth element (REE) concentrations of the specific components in the microbialites were normalized to Post-Archean Australian Shale (PAAS; McLennan, 1989) and Ce anomalies were calculated as (Ce/Ce*) = 2 × Ce SN /(La SN + Pr SN ). In general, the microbialites in the Leikoupo Formation have low ΣREE+Y contents, which range from 0.439 to 5.629 ppm. ...
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Microbialites are important reservoirs for oil and gas. The mineralization of organic matter in microbialites during early diagenesis can produce acidic fluids that dissolve carbonate grains, and can also result in an alkaline pore water that precipitates cement. The mineralization of organic matter in microbialites and its effect on microbialite reservoirs have not yet been studied in detail. In this study, quantitative statistical analysis of the two-dimensional spatial occurrence of pores and microbial fabrics, in situ geochemical analysis of specific components (microbial, transitional zone, and fine spar fabrics), and qualitative evaluation of the implications for microbialite reservoirs were undertaken on microbialites from Member IV of the Leikoupo Formation, Sichuan Basin, China. The quantitative statistical analysis shows that pores are spatially associated with microbial fabrics, but porosity has a poor correlation with microbial fabric content. In situ geochemical data indicate that microbialites with different porosities experienced different processes of organic matter mineralization. The processes of organic matter mineralization such as oxidation and nitrate reduction can provide more dissolution micropores than the process related with sulfate reduction, whereas the process of organic matter mineralization related with Fe–Mn oxide reduction results in cementation. Micropores created by organic matter mineralization can act as fluid channels for later dissolution and are important in the development of microbialite reservoirs.
... As another provenance proxy, REE can be effectively used to portray clastic sediment parental rocks (McLennan, 1989;Cullers, 1994Cullers, , 2000Nanga Bineli et al., 2021;Sonfack et al., 2021). Felsic rocks generally show high values of LREE/HREE ratios and exhibit negative Europium anomalies, whereas mafic rocks commonly show low values of LREE/HREE ratios and low or even lack of negative Europium anomalies (Cullers, 1994(Cullers, , 2000. ...
... Moreover, values of Eu/Eu* and Ce/Ce* were calculated to determine the characteristics of Eu and Ce anomalies in the sediments. These are important indicators because Eu anomalies (δEu) are usually produced by the source bedrock, and Ce anomalies (δCe) are attributed to the sedimentary environment (McLennan, 1989;Wang et al., 2019). These values were calculated as follows: ...
Article
Recent studies have suggested that rare earth elements (REEs) are contaminants of emerging concern. Moreover, the understanding of the occurrence and risks of REEs in river-estuary-bay systems is limited. The present study investigated the distributions, geochemical characteristics, and ecological risks of Y and 14 REEs (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) in sediments from the Yellow River to its estuary and adjacent Laizhou Bay. The average total concentrations of Y and REEs in the sediments generally increased from the Yellow River (149 mg/kg) to the estuary (165 mg/kg) and Laizhou Bay (173 mg/kg). In the estuarine core sediments, the concentrations of Y, light REEs (LREEs), and heavy REEs (HREEs) were in the ranges of 19.5-31.4 mg/kg, 58.6-156 mg/kg, and 12.3-19.1 mg/kg, respectively, from the 1700s to 2018, showing no obvious increasing or decreasing trends. The surface and core sediments from the river to the bay were characterized by obvious fractionation between LREEs and HREEs. In sediments, Fe minerals and clay are believed to promote the accumulation of REEs, especially HREEs. The enrichment levels of REEs generally increased from the middle reaches of the Yellow River to the bay, and Gd, Tb, Dy, Ho, Yb, and Lu were the most enriched elements in the sediments. Lu had moderate potential ecological risks in sediments of "the Yellow River-estuary-bay" system, and other REEs had relatively low ecological risks. The potential ecological risk indices of Y and REEs ranged from 78.7 to 144, showing increasing trends from the Yellow River to its estuary and adjacent bay, which should raise concerns regarding emerging contaminant management around estuarine and coastal regions.
... a, La/Y, Ce/Ce*, Eu/Eu*, (La/Yb) N were performed and have helped to understand REE behavior and fractionation. These parameters were calculated based on Taylor and McLennan (1985), Anders and Grevesse (1989), McLennan (1989) as follows: ...
... Numerous REEs geochemical parameters including a, La/Y, Ce/Ce*, Eu/Eu*, (La/Yb) N were performed and helped to understand REEs behavior and fractionation. These parameters were calculated based on Taylor and McLennan (1985), Anders and Grevesse (1989), McLennan (1989) as shown in Table 2. ...
Article
Ferralsols in the transitional zone between the Adamaoua and the South Cameroonian plateaus provided evidence of significant economical and scientific interests, but they have received very little attention over the last decades. Thus, macroscopic, mineral and geochemical investigations of two residual soil profiles from orthogneiss in the Bétaré-Oya Gold District (BOGD) with significant morphological differences were conducted in order to assess weathering and lateritization processes and their significance to the occurrence of mineralized trace and rare earth elements. Macroscopically, soil profile in upslope is deep weathered and thick (> 8.0 m thick), exhibiting a 5.1 m thick encrusted mineral level. Inversely, the downslope soil profile is moderately weathered and marked by a near surface water table that partly affects the mineral horizon B. These studied ferralsols result from an intense weathering but weak to moderate lateritization as revealed by the Chemical Index of Alteration (CIA: 87 to 99%), the Plagioclase Index of Alteration (PIA: 98 to 100%) and the Index of Lateritization (IOL: 31.48 to 60.83%). The two soil profiles have a similar mineralogical content characterized by the predominance of newly-formed secondary minerals such as kaolinite (12–40%), gibbsite (12–27%), goethite (7–15%), hematite (2–15%), maghemite (6–10%) and anatase (1–2%). However, a considerable amount of residual quartz (16–56%) and muscovite (3–15%) is evidenced in the weathering products. Geochemically, the weathering products of Ndokayo show weak to moderate depletion of SiO2 (77.26–31.82%), strong depletion of alkali and alkaline earths (Weathering Index of Parker or WIP: 56.73 to 1.56), and moderate enrichment of Al2O3 (12.43–29.20%), Fe2O3 (1.26–23.45%) and TiO2 (0.11–1.77%). V (64.67–210 ppm) and Cr (25.81–720 ppm) are the most enriched trace elements in this area, with their respective maximum enrichment factor of 2 and 7, and display similar geochemical patterns with Fe2O3, suggesting their adsorption or incorporation into the crystalline structure of Fe-oxides. Some others mineralized trace elements (Sc, Ga, As, Mo, Sn, Cs, Pb, Bi, Th and U) exhibit low to moderate contents, even if their mineralization indices range between 1 and 81. This is indicative of low mining potential of the Ndokayo weathering products. Finally, the deep and intense weathering of orthogneiss, coupled with weak to moderate lateritization of the weathering products in the study area is controlled by rock type involving the formation of kaolinitic laterites and bauxitious kaolins with weak mineralization indices of some trace and rare earth elements.
... Accessory minerals like zircon, monazite, allanite, and xenotime are rich in incompatible elements such as Th, U, Y, Hf, and Zr (Grauch, 1989;McLennan, 1989;Jiang et al., 2000;Slack et al., 2000) and can influence the REE concentrations of tourmaline. For the Lianyunshan tourmalines, the influence of monazite and allanite inclusions is likely reflected in the high U contents (to 10-13 ppm) of a few grains of Tourmalines I and II, although their mean values are 1.2 ± 2.76 ppm and 1.6 ± 3.99 ppm, respectively (ESM Table S2). ...
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Although tourmaline is common in pegmatite-related Nb-Ta deposits and metasedimentary cover rocks in the Lianyunshan Complex of northeastern Hunan Province, South China, its fluid sources and genetic relationship to the host pegmatite remain unresolved. In this contribution, we chose the less-studied tourmaline minerals and analyzed their chemical (major, trace, and rare earth elements) and boron isotopic compositions to shed light on the process of pegmatite-related Nb-Ta mineralization. Lianyunshan tourmalines are both metasedimentaryhosted (Tourmalines I and II) and pegmatite-hosted (Tourmaline III), belong to the alkali group, have mainly schorlitic compositions, and contain dominantly hydroxyl anionic species. Element substitution is controlled by the activities MgFe-1, alkali-deficiency vector R1Al[Na(FeMg)]-1, AlO[R(OH)]-1, and □Al(NaR)-1. Lianyunshan tourmalines define a trend consistent with foitite to magnesio-foitite compositions. Lianyunshan tourmalines are poor in Fe3+, with a Fe3+/Fe2+ ratio of zero in all samples. This feature, as well as their non-alignment with the FeAl-1 vector, suggests precipitation from a reduced fluid. Fluid salinity may have been moderate to low given the low Na contents of all samples (0.60–0.66 apfu). Tourmaline I is rich in Mg and Ti, but the contents of these elements decrease in Tourmalines II and III. Fluid fractionation may have played a role in the decreasing Mg and Ti contents with corresponding enrichment in the contents of Fe, Na and X□ as Tourmalines II and III precipitated. Unusual enrichment of Li is found in the pegmatite-hosted Tourmaline III (mean 97 ppm) relative to Tourmalines I and II (means ~ 31–33 ppm), and of Sn in Tourmaline II (mean 291 ppm) relative to Tourmalines I and III (means ~ 3–10 ppm). δ11B values are similar for Tourmalines I (–14.21 to –12.09 ‰), II (–15.07 to –13.71 ‰), and III (–14.48 to –13.55 ‰), being consistent with the δ11B of typical S-type granites (~− 16 to − 8 ‰) such as the S-type muscovite monzogranite host of the Lianyunshan tourmalines. We conclude that the Lianyunshan tourmalines precipitated from an evolved melt that formed muscovite monzogranite.
... Accessory minerals like zircon, monazite, allanite, and xenotime are rich in incompatible elements such as Th, U, Y, Hf, and Zr (Grauch, 1989;McLennan, 1989;Jiang et al., 2000;Slack et al., 2000) and can influence the REE concentrations of tourmaline. For the Lianyunshan tourmalines, the influence of monazite and allanite inclusions is likely reflected in the high U contents (to 10-13 ppm) of a few grains of Tourmalines I and II, although their mean values are 1.2 ± 2.76 ppm and 1.6 ± 3.99 ppm, respectively (ESM Table S2). ...
Article
Although tourmaline is common in pegmatite-related Nb-Ta deposits and metasedimentary cover rocks in the Lianyunshan Complex of northeastern Hunan Province, South China, its fluid sources and genetic relationship to the host pegmatite remain unresolved. In this contribution, we chose the less-studied tourmaline minerals and analyzed their chemical (major, trace, and rare earth elements) and boron isotopic compositions to shed light on the process of pegmatite-related Nb-Ta mineralization. Lianyunshan tourmalines are both metasedimentary-hosted (Tourmalines I and II) and pegmatite-hosted (Tourmaline III), belong to the alkali group, have mainly schorlitic compositions, and contain dominantly hydroxyl anionic species. Element substitution is controlled by the activities MgFe-1, alkali-deficiency vector R1Al[Na(FeMg)]-1, AlO[R(OH)]-1, and □Al(NaR)-1. Lianyunshan tourmalines define a trend consistent with foitite to magnesio-foitite compositions. Lianyunshan tourmalines are poor in Fe3+, with a Fe3+/Fe2+ ratio of zero in all samples. This feature, as well as their non-alignment with the FeAl-1 vector, suggests precipitation from a reduced fluid. Fluid salinity may have been moderate to low given the low Na contents of all samples (0.60-0.66 apfu). Tourmaline I is rich in Mg and Ti, but the contents of these elements decrease in Tourmalines II and III. Fluid fractionation may have played a role in the decreasing Mg and Ti contents with corresponding enrichment in the contents of Fe, Na and X□ as Tourmalines II and III precipitated. Unusual enrichment of Li is found in the pegmatite-hosted Tourmaline III (mean 97 ppm) relative to Tourmalines I and II (means ~31-33 ppm), and of Sn in Tourmaline II (mean 291 ppm) relative to Tourmalines I and III (means ~3-10 ppm). δ11B values are similar for Tourmalines I (–14.21 to –12.09 ‰), II (–15.07 to –13.71 ‰), and III (–14.48 to –13.55 ‰), being consistent with the δ11B of typical S-type granites (~−16 to −8 ‰) such as the S-type muscovite monzogranite host of the Lianyunshan tourmalines. We conclude that the Lianyunshan tourmalines precipitated from an evolved melt that formed muscovite monzogranite.
... Most major oxides are easily mobilized (e.g., K 2 O, CaO, Na 2 O) which makes their use in provenance characterization of interbedded tuff layers unreliable (Feng et al., 2021). However, Al 2 O 3 , TiO 2 , some trace elements (e.g., Zr, Nb, Ta, and Th), and REE are widely used for tracing source magmas owing to their immobility during weathering and diagenesis (Mclennan, 1989;Kacmaz, 2016;Dai et al., 2017Dai et al., , 2018aLi et al., 2021). As shown in Fig. 7B, the Maquan section tuff chondrite- normalized REE distribution features LREE enrichment (La N /Sm N = 3.78-6.79) ...
Article
Tuffs, produced by explosive volcanic eruptions, are widely deposited throughout the Precambrian to Cenozoic stratigraphic record. Due to rapid compaction and erosion, preservation and identification of tuffs in distal environments are challenging. However, in deep lacustrine environments, tuffs may be found well-preserved as interlayers in the organic-rich mudstone. This in turn provides valuable insights into the origin, transport, and diagenesis of volcanic material. In this study, we performed an integrated sedimentological, mineralogical, and geochemical analysis of seven tuff samples collected from the lower part of the Chang7 member of the Maquan section to infer on their provenance, transport mechanisms and post-depositional alterations. Immobile element ratios, tectonic discrimination diagrams, trace element distribution patterns, and negative whole-rock εNd(t) reveal an intermediate to felsic continental arc source of the studied tuff. Supported frameworks and ash aggregates in the tuff are in favor of the transport from pyroclastic density currents and ash plumes during multiple volcanic eruptions with various degrees of eruption volume and water content. Tuff diagenesis is characterized by dissolution of plagioclase, illitization of smectite, cementation of carbonate minerals, and presence of bud-dingtonite. Relatively ordered illite-smectite and low vitrinite reflectance from the adjacent organic-rich mudstone indicate diagenetic evolution of studied tuff have reached mesogenetic stage.
... However, as already mentioned, a potential anthropogenic contribution cannot be excluded for MG and M2, consistent with other metals . This fractionation demonstrated by the higher positive ratios (La/Yb)n and (Sm/Yb)n with high flow, might illustrate the progressive contribution of intermediate and felsic rocks by erosion processes (McLennan, 1989;Ramesh et al., 1999;Brito et al., 2018). Nevertheless, the slight depletion of HREE in sediments would also result in their greater tendency to form stable soluble complexes than LREE and MREE, and thus to be preferentially transported in overlying water instead of accumulating in the sediments (Fleet, 1984;Millero, 1992;Kuss et al., 2001;Sappal et al., 2014). ...
... As mentioned above, the representative amphibolite and plagioclasehornblende schist samples in this study were collected from host-rocks of the Heishan'gou deposit, and suffered amphibolite facies metamorphism. The igneous zircon domains from the amphibolite and plagioclase-hornblende schist yield upper intercept ages of 2781 ± 43 McLennan (1989) and Taylor and McLennan (1985), respectively. ...
Article
The Yudongzi banded iron formations (BIFs) are widely spread in the Neoarchean Yudongzi Group of the Bikou Terrane, Central China. Their sedimentary and metamorphic ages, however, remain controversial, either their forming or reworking processes. In this contribution, we conducted an integrated study of zircon U-Pb-Hf isotope geochemistry, as well as mineral and bulk-rock geochemistry on the Heishan’gou iron deposit, the largest iron deposit of the Yudongzi BIFs, to constrain their formation and metamorphism ages, source of ore-forming material and tectonic setting. Mineral chemistry analysis indicates that the amphibolite, host-rock of the Heishan’gou deposit suffered amphibolite facies metamorphism. LA-ICP-MS U-Pb dating of zircon grains from orthometamorphic host-rocks suggests that the Heishan’gou deposit was formed at the early Neoarchean (2781±43 Ma for amphibolite and 2776±43 Ma for plagioclase-hornblende schist), and metamorphosed at ca. 2480±26 Ma and 1818±44 Ma, respectively. The low contents of aluminum, titanium and high field strength elements in BIFs suggest that they are detritus-free marine chemical precipitates. The rare earth elements (REE) and Y patterns of BIFs display seawater-like signatures with light REE depletion, and positive La and Y anomalies. Meanwhile, their positive Eu anomalies suggest that submarine hydrothermal fluid might also be involved in the precipitation of BIFs. Combined with zircon Hf isotope data and geochemical compositions of amphibolites, it is proposed that the Yudongzi BIFs should be formed at back-arc basin setting. Compared with the representative Archean continent nucleus of the Yangtze Block (Kongling Complex), the Yudongzi Complex experienced distinct crustal evolutionary history. It indicates that the Yudongzi Complex might represent the accretionary block combined to the Yangtze continental nucleus later than the Paleoproterozoic.
... The Eu concentration (Table 1) is extremely low (on the order of the EPMA detection limit) in both specimens, causing strongly negative Eu anomalies (Fig. 4). The Eu/Eu* ratio [with Eu* = (Sm  Gd) 0.5 ; compare McLennan, 1989] was calculated as 0.03 for the Kolonna sample and 0.04 for the Masimbula sample, respectively. Cerium shows an insignificant behaviour to weakly positive anomaly (Fig. 4). ...
... The enrichment in LREE and HREE of the muscovite-based ceramics (Figure 8b-d) is attributed to the higher retention potential of REE shown by muscovite, whose layer charge is higher than that of illite and kaolinite (Andersson et al., 2004;Degryse & Braekmans, 2014;Honty, Clauer, & Šucha, 2008;Meunier, 2005;Šegvić et al., 2021;Zanoni & Šegvić, 2019). It should also be noted that REE is primarily transported by mechanical processes and carried by solid load, rather than dissolved load during erosion and sedimentation McLennan, 1989). It follows that the higher REE content in the muscovite ceramic matrix might have been inherited from the crystalline precursor rocks. ...
Article
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The Petit-Chasseur megalithic necropolis is a key archaeological context for analyzing the social and ideological changes at the end of the Neolithic in the Alpine region of Central Europe. The link between the funerary monuments and settlement sites was established by means of ceramic archaeometric analysis. Domestic pottery from settlement sites were thoroughly characterized using multiple spectroscopic and microscopic techniques. Twelve ceramic fabrics were identified along with three types of clay substrate: illitic, muscovitic, and kaolinitic. Reconstructed paste preparation recipes largely involved the tempering of the raw clays with crushed rocks or coarse sediments. Types of raw material were not picked up randomly but were selected or avoided due to their particular compositional properties and attest to the exploitation of glacial, gravitational, eolian, and fluvial deposits. Compositional correspondence between ceramic grave goods and domestic pottery allowed identification of a link between the megalithic tombs and settlement sites, thus providing new data contributing to the investigation of the social dimension of monumental burials. Ceramic grave goods were revealed to be intertwined with the social instability affecting the 3rd millennium BC communities of the Upper Rhône Valley.
... According to Hofmann (1988), the depletion of Nb suggests the fractionation of Nb from the source rock since it is immobile during sedimentary processes. Th content is lower than the average UCC (10.70 ppm) value, which suggests the influence of continental crust materials (McLennan 1989). Hf concentration is lower than the average UCC value of 5.8 ppm (Taylor and McLennan 1995) which suggests different levels of mafic minerals and the depletion of heavy minerals especially zircon (Cullers 1988). ...
Article
This study uses petrographical and whole-rock geochemical data to determine the provenance, paleo-weathering conditions, tectonic settings, paleo-climate, and mixing proportions of the conglomerate and greywacke in the Chagupana area within the Paleoproterozoic Birimian in North-West Ghana. The conglomerate is foliated and composed of dominant metamorphosed clasts which are matrix-supported, poorly sorted, and polymictic. The greywacke is immature, medium to coarse-grained, poorly sorted, and rich in quartz (53%) and feldspar (46%). The major element contents of 30 greywacke samples were determined by X-ray fluorescence, while the trace element contents including rare earth elements (REEs) were analyzed by inductively coupled plasma mass spectrometer. SiO2, Na2O, and Fe2O3 are slightly enriched while TiO2, MnO, MgO, CaO, K2O, and P2O5 are depleted, compared with average upper continental crust values. The greywacke is sodic with K2O/Na2O ratio of 0.63. Average chemical index of alteration (53%) and chemical index of weathering (58%) values indicate weak chemical weathering, while Plagioclase index of alteration (53%) value suggests weak-moderate alteration of plagioclase. The greywacke is from intermediate-felsic source rocks with minimum recycling, incipient alteration, and underwent K-metasomatism during diagenesis. Tectonically, the rocks belong to an active continental plate margin of a rift basin with slight positive Eu anomaly suggesting derivation from young undifferentiated volcanic arc. Very low TiO2 (< 2.0 wt.%) content suggests the influence of igneous rocks from magmatic arcs. Positive Ba-Th anomaly, negative Nb–Ta, and Zr-Hf anomalies suggest an arc setting associated with subduction. The detritus making up the Chagupana greywacke is best modeled with mixtures having 59% granite and 41% basalt.
... Lithology is one of the important controlling factors of REE composition and spatial distribution pattern (Cullers, 2000;McLennan, 1989;McLennan et al., 1993). Based on the geological map in the northeastern TP (Fig. 1b), it is found that the Qilian Mountains in the northeastern margin of the TP are dominated by a mixture of Cenozoic arc, Early Paleozoic arc, Late Paleozoic arc, and other stratigraphic chronologies. ...
Article
Rare earth elements (REE) are widely used as tracers for surface processes due to their zonal differences in composition and special geochemical indicators. In this study, we collected 30 glacial meltwater samples from a large area of the northeastern Tibetan Plateau region and analyzed the REE composition of suspended particulate matter (SPM, d > 0.45 μm) to explore the spatial distribution, origins and the influencing factors of REE in SPM. Results suggested that chondrite-normalized REE distribution patterns were characterized by steep LREE and relatively flat HREE, which is different from that of PAAS-normalized. The high (La/Sm)N ratio and low (Gd/Yb)N ratio indicated that the degree of LREE fractionation was higher than that of HREE. We found an obvious correlation between REE concentration and SPM concentration, indicating that REE concentration in glacial runoff was significantly affected by SPM contents. It was found that Ce/Ce* decreased first and then increased with the decrease of altitude in the glacial river basins, which may contribute to weathering, oxidation, and physicochemical property of the water environment in the study areas. At the glacier forefield, the degree of weathering is intense, resulting in the highest Ce/Ce* value in the altitude between 3200-4800 m. However, this was not obvious in non-glacial regions. Compared REE geochemical parameters (e.g., LREE/HREE, Eu/Eu*, LaN/SmN) of SPM in the glacier basin with those of Asian potential dust sources and long-range transport (LRT) dust deposited on the studied glaciers, we found that the SPM in the glacial river basins is affected by lithology of parent materials, the LRT dust from the surrounding deserts, the release of ice/snow dust, and the detrital material from local rock weathering. This study provides a new perspective on the composition, distribution and variation in the altitude of REE in the glacial river basin of the northeast TP, and thus is of significance to improve the understanding of the source and migration process of REE in SPM of glacial river basins.
... The contents of REE were normalized on C1 chondrite with the data given by Anders and Grevesse [20]. The numerical values of the Ce and Eu anomalies were calculated using the equations given by McLennan [21]. ...
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This mineralogical and fluid inclusion study was conducted on an Au-bearing quartz–sulfide vein encountered in the deep parts of the Bytíz deposit in the Příbram uranium and base-metal district, Bohemian Massif, Czech Republic. The samples were taken where the Au-bearing vein is crosscut by the common base-metal Zn-Pb ore vein Bt23C. The early mineralization of the Au-bearing vein is composed mainly of quartz (Q-1 to Q-3), illite–muscovite, Fe-Mg chlorite, arsenopyrite, and Au-Ag alloys, showing a wide range of compositions (4–69 at. % Ag) and a decrease in Au/(Au + Ag) ratios during vein evolution. Younger hydrothermal processes led to the crystallization of nests and veinlets composed of late quartz (Q-4), carbonates (siderite, dolomite–ankerite and calcite), base-metal sulfides (galena, sphalerite, chalcopyrite, and tetrahedrite), a suite of Ag and Bi-tellurides, and acanthite. The input of Sb is manifested by the partial to complete replacement of some gold grains by aurostibite and an unnamed (Ag,Au)-Sb oxide with a composition close to AuSbO3. The fluid inclusion study, combined with chlorite thermometry and arsenopyrite thermometry, showed that the early mineralization crystallized from progressively cooled (from 300 to 400 °C down to ca. 180 °C), diluted (1.2–7.0 wt. % NaCl eq.) aqueous solutions. The late portion of the mineralization formed from aqueous fluids with highly variable salinity (0.2–23.4 wt. % NaCl eq.) and homogenization temperatures decreasing from ca. 250 °C to < 50 °C, which compare well with the base-metal mineralization of the vein Bt23C and other base-metal veins of the Příbram ore area. Our study illustrates the nature and intensity of the processes of the reworking of the early gold mineralization mediated by the younger Ag,Sb-rich base-metal fluids, giving rise to Příbram’s typical late-Variscan vein Zn-Pb mineralization.
... However, Tucker a.o., (1997) -2 ) anion. The abundance of REE, document the variable paleo-environmental conditions (Mclennan, 1989). The enrichment in the REE may be resulted from late diagenetic alteration and/or indicating anoxic conditions. ...
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The carbonaceous shale is widely distributed within small semiclosed basins in Allouga, Abu Thor, Abu Zarab and Abu Hamata localities in Um Bogma area. This facies form a good host rock for uranium-molybdenum and LREE-bearing mineralizations. Uranium mineralization with various scales and grades were recorded due to intensively interbedded oxidation. This mineralization is localized with Fe-Mn oxides and organic matter rich sediments. The NASC-normalized chemical composition of the studied shale shows highly enrichment in Fe 2 O 3 , P 2 O 5 , Cu, Zn, Zr, Pb, V, Mo, Cr, U and depletion in SiO 2 , Al 2 O 3 , MgO, CaO, K 2 O, Co and Ni. Uranium and Mo are reduced either abiotically by the surface-catalysed reduction via Fe 2+ or enzymatically by sulphate reducing bacteria. The identified secondary minerals are umohoite, moluranite, sedovite, brannerite, bassetite, torbernite, jarosite, willemite, kaolinite, hematite, goethite, pyrite, galena and barite, in addition to detrital quartz and zircon. The chondrite-normalized REE patterns of the studied samples show positive Ce anomaly (+∆ Ce) reaching up to 5.9. This led to the dominance of Ce-bearing minerals as bastnasite and brannerite. Bastnasite is the most significant known LREE-bearing mineral and account for most of the REE currently utilized in the world. Organic matter and sulphides play an important role in development and preservation of the sensitive redox metals. Mo, U, V and LREE are removed from the groundwater with sulphidized organic matter or via sequestration by Fe-S phases and/or Fe-Mn oxyhydroxides. The enrichment is related to supergene processes than to the detrital clastics influx.
... Since Zr is relatively stable and can reflect the properties of the parent rocks (Taylor & McLennan, 1985), its concentration can be used to identify sediment provenance (McLennan, 1989). Zr/Sc ratios differed significantly among the three regions (p < .05, ...
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Frequent and serious aeolian disasters occur in the upper and middle reaches of the Yarlung Zangbo River, which runs through the high‐elevation Tibet Plateau. Sediment geochemical characteristics can be used as a proxy to identify the sediment's provenance. To determine the provenance of aeolian sediments in the river's basin, we analyzed major and trace element contents from surface samples and local clastic rocks throughout the basin. We found that the major and trace elements differed between the middle reaches, upper reaches, and regions south of the river. Major element contents were similar in the upper and middle reaches, but trace elements differed. Al2O3, MgO, and Na2O concentrations increased from the upper reaches to the lower reaches, and in the lower reaches, MgO and Na2O were enriched compared to the crustal average. The similarities between samples in the lower part of the upper reaches and those in the middle reaches indicated that sediment transported by fluvial systems from the upper reaches was first deposited in the wide valleys near Xigaze, where they formed a large area of shifting sand. These deposits were then transported by the wind to the river's middle reaches, where they formed a large area of shifting sand. When we compared aeolian sediment in the middle reaches with the local clastic rocks, they appeared to be unrelated. The difference between sediments south of the river and those in the middle reaches means that the southern sediments were not transported to the middle reaches. Therefore, the aeolian sediment in the middle reaches of the Yarlung Zangbo River mainly came from the lower part of the upper reaches, not from the local clastic rocks.
... Based on measured mMg/Ca values, the following equations were used(Rimstidt et al., 1998; 240 Coggon et al., 2010) to calculate the seawater mMg/Ca values, where T is temperature in241 Kelvin, and temperatures are constrained to 15-35°C for shallow marine cement formation. Mg/Ca] fluid = [Mg/Ca] marine cements/Ce anomaly profiles from early marine cements248 Normalisation of Ce abundance relative to the neighbouring rare earths (Ceanom) -Archean Australian shale (PAAS;McLennan, 1989). In this calculatio n, 254 Pr/Pr*=2Prn/(Cen+Ndn) can be used to constrain the true negative Ceanom (Bau & Dulski, 255 1996). ...
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The Ediacaran‐Cambrian Radiation marks the widespread appearance of metazoans and calcareous biomineralised hard parts. These innovations occurred during an interval of dynamic changes in marine redox and seawater chemistry. Here, changing carbonate mineralogy, Mg/Ca ratios, and rare earth element concentrations including the relative abundance of cerium (Ce anomaly: Ceanom) are documented to track seawater oxygen levels, in well‐preserved early marine cements from shallow marine reefs from Cambrian Stage 2 to 4 (ca 525 – 512 Ma). First, integrating the mineralogical data with published records, several shifts in dominant carbonate mineralogy are inferred: ‘dolomite‐aragonite seas’ in the late Ediacaran; ‘aragonite/ high‐Mg calcite seas’ in Cambrian Stage 2; a temporary shift to a ‘calcite sea’ during early Cambrian Stage 3; an ‘aragonite sea’ between late Cambrian Stage 3 and late Cambrian Stage 4, then a gradual shift from mixed ‘aragonite‐calcite seas’ during the middle and upper Cambrian towards a ‘calcite sea’ by the early Ordovician. Second, based on measured mMg/Ca in early marine cements, calculated seawater mMg/Ca at 15 and 35oC ranges from 1.2 ‐ 0.8 in Cambrian stage 2, 0.7 ‐ 0.4 in Stage 3, and 1.4 ‐ 0.9 in Stage 4, respectively. Finally, analysed Ceanom data combined with existing Ceanom data suggests potentially three phases of global oxic expansion. First, a long‐lived phase of progressive oxygenation during the late Ediacaran to Fortunian (ca 550 to 540 Ma; average Ceanom from 0.99 to 0.41), and possibly two shorter phases during early Cambrian stage 3 (ca 519 Ma; average Ceanom from 0.91 to 0.40) and Stage 4 (ca 512 Ma; average Ceanom from 1.02 to 0.49), bounded by intervals of more dominant anoxia. Summarising, these data demonstrate that early marine cements offer an underused and high‐resolution archive of shallow marine redox and seawater chemistry through this critical transition in Earth's evolution.
... All quantified data are shown in Tables 3 and 4, but we note that values below approximately 0.02 mg kg − 1 are close to the detection limits. Rare earth element contents of carbonates were normalized to Post Archean Australian Shale (PAAS) after McLennan (1989). ...
Article
The Ronda peridotite in southern Spain is subject to low-temperature serpentinization by circulating groundwaters that produces hyperalkaline fluids of high pH and low dissolved inorganic carbon content (DIC). When these waters resurface as hyperalkaline springs they take up atmospheric carbon dioxide (CO2), which triggers the precipitation of travertine carbonates. Spring waters at Baños del Duque, Fuente Romana, and Fuente Amargosa show typical chemical features of hyperalkaline springs such as high pH and low DIC, yet exhibit an unusual distribution of rare earth elements (REEs) enriched in lanthanum (La) and cerium (Ce). In order to constrain changes in spring water chemistry and carbonate precipitation during atmospheric CO2 uptake, a reaction path model was set up to illustrate that the distribution of REE species in the high pH and low DIC water is strongly dependent on REE complexation by hydroxide and carbonate species. Reaction path modeling results show that during spring fluid emission and CO2 uptake, REE speciation in the fluids shifts from a dominance of hydroxide to carbonate complexes. The complexation of rare earth elements in the high pH, low DIC fluids strongly depends on the DIC content of the respective fluid. The REE distribution of travertine deposits associated with the hyperalkaline springs deviates from that in the fluids, suggesting that travertines precipitated from fluids different to those currently emitted from the springs.
... Therefore, the distribution and Last and Smol, 2001). The normalized REE distribution is used to express the degree of weathering of soils (Rollinson, 1993;McLennan, 1989). Fractionation of the REE (Sm/Nd, Eu/Eu*, Ce/Ce*) is evident during weathering soil. ...
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Rare earth elements (REE) total concentration in soils are impacted by successive soil forming processes. So it can be used as indicator of soil development. Iron oxides and OM are known to have strong affinities with REE, and to play an important role in transfer and immobilization of REE. The ones available in the literature indicate that the release of REE induced by weathering and subsequent leaching in percolating water are the main pathways determining the REE fate in soils. Show that the REE content is strongly correlated to the general loss of elements and mineral weathering. In the redistribution of the elements resulting from weathering, the mobility of these elements and the geochemical changes at the end of the washing appear as the main determining factors. Weathering rate of soils is a fundamental approach to understanding and revealing the development processes of soils.
... The chemical composition of four Fe-Mn nodules (Si, Al, Ca, Fe, K, Mg, Mn, Na, P, Ti, Li, Be, Sc, V, Cr, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Rb, Sr, Y, Zr, Nb, Mo, Ag, Cd, Sb, Cs, Ba, REE, Hf, Ta, W, Tl, Pb, Th, and U) were determined by inductively coupled plasma mass-spectrometry (ICP-MS) using Agilent 7700x (Agilent Technologies) and by inductively coupled plasma atomic emission spectroscopy with iCAP6500 Duo (ThermoScientific) in the laboratory of Far East Geological Institute in Vladivostok. Rare Earth Element and Yttrium (REY) distribution plots were used for studying Fe-Mn deposit genesis and were normalized to shale (PAAS, Post-Archean Australian Shale) [57]. The Ce anomaly was calculated as Ce* = 2Ce/(La + Pr) for PAAS-normalized values. ...
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Ferromanganese (Fe-Mn) sedimentary layers and nodules occur at different depths within sediments at deep basins and ridges of Lake Baikal. We studied Fe-Mn nodules and host sediments recovered at the slope of Bolshoy Ushkany Island. Layer-by-layer 230Th/U dating analysis determined the initial age of the Fe-Mn nodule formation scattered in the sediments as 96 ± 5–131 ± 8 Ka. The distribution profiles of the main ions in the pore waters of the studied sediment are similar to those observed in the deep-sea areas of Lake Baikal, while the chemical composition of Fe-Mn nodules indicates their diagenetic formation with hydrothermal influence. Among the bacteria in microbial communities of sediments, members of organoheterotrophic Gammaproteobacteria, Chloroflexi, Actinobacteriota, Acidobacteriota, among them Archaea—chemolithoautotrophic ammonia-oxidizing archaea Nitrososphaeria, dominated. About 13% of the bacterial 16S rRNA gene sequences in Fe-Mn layers belonged to Methylomirabilota representatives which use nitrite ions as electron acceptors for the anaerobic oxidation of methane (AOM). Nitrospirota comprised up to 9% of the layers of Bolshoy Ushkany Island. In bacterial communities of Fe-Mn nodule, a large percentage of sequences were attributed to Alphaproteobacteria, Actinobacteriota and Firmicutes, as well as a variety of OTUs with a small number of sequences characteristic of hydrothermal ecosystems. The contribution of representatives of Methylomirabilota and Nitrospirota in communities of Fe-Mn nodule was minor. Our data support the hypothesis that chemolithoautotrophs associated with ammonium-oxidizing archaea and nitrite-oxidizing bacteria can potentially play an important role as primary producers of Fe-Mn substrates in freshwater Lake Baikal.
... The REE contents of the studied kaolin resources normalized to chondrite and North American Shale Composite (NASC) as quoted by McLennan (1989) and Gromet and Dymek (1984), respectively. The normalization to chondrite (Fig. 23) The normalization to NASC reflects a more flat pattern, although the Carboniferous kaolin deposits have higher concentration magnitude and conserve clear Eu deficiency, compared to those of the Cretaceous (Fig. 24). ...
... The occurrence of these metals in the Earth's crust, their mineralogy, and different types of deposits on land and oceans are a vital part of the mineral exploration industry. So far, many studies have been conducted on the association and exploration of the REE-rich rocks and minerals to improve the understanding of the location, type, and style of REE mineralization [6][7][8][9][10][11][12][13][14][15][16]. However, the minerals rich in REEs are commonly associated with the uncommon varieties of igneous rocks, such as carbonatites and alkaline rocks, or in residual deposits formed from physical and chemical weathering of igneous rocks, pegmatites, iron-oxide, copper-gold deposits, and marine phosphates. ...
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A recent increase in the importance of Rare Earth Elements (REEs), proportional to advancements in modern technology, green energy, and defense, has urged researchers to look for more sophisticated and efficient exploration methods for their host rocks, such as carbonatites. Hyperspectral remote sensing has long been recognized as having great potential to identify the REEs based on their sharp and distinctive absorption features in the visible near-infrared (VNIR) and shortwave infrared (SWIR) electromagnetic spectral profiles. For instance, neodymium (Nd), one of the most abundant Light Rare Earth Elements (LREEs), has among the most distinctive absorption features of REEs in the VNIR part of the electromagnetic spectrum. Centered at ~580, ~745, ~810, and ~870 nm in the VNIR, the positions of these absorption features have been proved to be independent of the mineralogy that hosts Nd, and the features can be observed in samples as low in Nd as 1000 ppm. In this study, a neodymium index (NI) is proposed based on the 810 nm absorption feature and tested on the hyperspectral images of the Sillai Patai carbonatite samples to identify Nd pixels and to decipher the relative concentration of Nd in the samples based on the depth of the absorption feature. A preliminary spectral study of the carbonatite samples was carried out using a spectroradiometer to determine the presence of Nd in the samples. Only two of the absorption features of Nd, centered at ~745 and ~810 nm, are prominent in the Nd-rich samples. The other absorption features are either weak or suppressed by the featureless spectra of the associated minerals. Similar absorption features are found in the VNIR and SWIR images of the rock samples captured by the laboratory-based hyperspectral cameras that are processed through Minimum Noise Fraction (MNF) and Fast Fourier Transform (FFT) to filter the signal and noise from the reflectance data. An RGB false-color composite of continuum-removed VNIR reflectance bands covering wavelengths of 587.5, 747.91, and 810.25 nm efficiently displayed the spatial distribution of Nd-rich hotspots in the hyperspectral image. The depth of the 810 nm absorption feature, which corresponds to the concentration of Nd in a pixel, is comparatively greater in these zones and is quantified using the proposed NI such that the deeper the absorption feature, the higher the NI. To quantify the Nd-rich pixels in the continuum-removed VNIR images, different threshold values of NI are introduced into a decision tree classifier which generates the number of pixels in each class. The strength of the proposed NI coupled with the decision tree classifier is further supported by the accuracy assessment of the classified images generating the Kappa coefficient of 0.82. Comparing the results of the remote sensing data obtained in this study with some of the previously published studies suggests that the Sillai Patti carbonatite is rich in Nd and associated REEs, with some parts of the samples as high in Nd concentration as 1000 ppm.
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The rare earth element ( REE ) content of the Tunisian Permian–Neogene shales have been studied to determine the origins of the clay minerals in these shales. The Permian–Neogene series overlies the Palaeozoic basement that has been studied via oil-drilling cores. This study of REE s was performed in various palaeogeographical domains of Tunisia, from the ‘Saharan Platform’ in the south to the ‘Nappes Zone’ in the north. In this work, those levels rich in illite (Palaeozoic, Triassic and Jurassic), smectite (Campanian–Maastrichtian) and palygorskite (continental Eocene) as well as some Miocene levels rich in halloysite are examined. The distribution of REE s in the Tunisian margin sediments is generally homogeneous, except for the Miocene levels containing halloysites. The normalization curves of REE s vs North American shale composite characterize the inherited clays regardless of the dominant minerals, except for a few cases of neoformation. The flat REE curves indicate a detrital origin of the studied clay levels.
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The Mewongo area of the Nyong Complex is located in the northwestern part of the Congo craton in southwestern Cameroon. The metavolcanosedimentary succession in this area comprises banded iron formations (BIFs), interlayered with amphibolites and gneisses and intruded by metamorphosed dolerite dykes. Within the framework of detailed field investigation, we report whole-rock geochemical data for the BIFs, metadolerites, and gneisses to constrain their provenance and tectonic setting, and present LA-ICP-MS U-Pb-Hf isotopic data for zircons from amphibolite and gneiss to assess the depositional age of BIFs from the Nyong Complex and understand the crustal evolution at the northwestern margin of the Congo craton. The geochemical composition of the Mewongo BIFs indicates a contribution of hydrothermal fluids, derived via submarine alteration of volcanics, and seawater. Geochemical and LA-ICP-MS U-Pb detrital zircon data for the gneisses reveal felsic protolith with ages between 2.97 and 2.65 Ga. Our zircon U-Pb-Hf isotope data suggest that a significant growth of juvenile crust occurred at ca. 2.7-2.2 Ga, followed by a reworking event at ca. 2.1 Ga with only minor juvenile crust addition. The metadolerites, cutting the metavolcanosedimentary succession, range in composition between tholeiitic and calc-alkaline basalts. They can be subdivided into two groups based on their trace element signature. The group I metadolerites have OIB-like geochemical composition (e.g., enriched LILE, HFSE, and LREE), while the group II metadolerites exhibit MORB-like geochemical signature (e.g., flat HFSE and HREE patterns). Metadolerites belong to two different so far undated magmatic events on the Congo craton that were previously recognized on the adjacent Ntem Complex. LA-ICP-MS U-Pb zircon dating of amphibolites, combined with chemical composition of metadolerites and gneisses, indicate deposition of the metavolcanosedimentary sequence at ca. 2.1 Ga in a pro-foreland basin sandwiched between the West and East Gabonian blocks, at the time when the Congo and São Francisco cratons collided during the Eburnean-Transamazonian orogeny. The Nyong Complex BIFs were therefore deposited in a deep, open-marine setting during the ca. 2.1-2.0 Ga time interval.
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The Tanshan area is located in the southern section of the west margin of the Ordos basin. The Middle Jurassic Yan’an Formation is relatively thick and rich in coal and oil shale layers, having positive potential for energy development. In order to explore the sedimentary environment of oil shale and the controlling factors of organic matter accumulation, 18 oil shale samples collected from two boreholes (Guyou-3 and Guyou-4) in the Tanshan area were selected as the research objects, and organic geochemical and elemental geochemical tests were carried out systematically. The results show that oil shales have the characteristics of medium oil content, medium ash, high calorific value, low sulfur and low maturity stage, which constitutes good hydrocarbon generation potential. The organic matter is mainly humic type, resulting from terrigenous debris and higher plant debris. The indictors of C-value (mean 81.90), Th/U ratio (mean 3.44), CaO/(MgO·Al2 O3) ratio (mean 0.07), δEu (mean 0.71), δCe (mean 1.15), V/(V + Ni) ratio (mean 0.79), Ceanom index (mean −0.04), Babio index (mean 488.97 μg/g), P/Ti ratio (mean 0.08), TOC/S ratio (mean 59.80), Sr/Ba ratio (mean 0.57) and (La/Yb)N ratio (mean 14.71) indicate that Tanshan oil shales were formed in a warm–humid climate and anoxic-reducing environment, with a low-salinity water body and a low deposition rate but also a relatively low initial paleoproductivity. Paleoclimate conditions, organic matter sources and redox properties of paleowater are the main controlling factors affecting the accumulation of organic matter in oil shales. Although low paleoproductivity and deposition rates are not conducive to the preservation of organic matter, under the conditions of warm and humid climate and a reducing water environment, the continuous and stable input of terrigenous debris and higher plant debris can also cause the enrichment of organic matter.
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In the high altitude (>3000 m asl) grasslands of northern Ecuador, the Páramo ecosystem, soils generally formed on recent volcanic ashes being <10,000 years old in the northern and central part of the cordilleras. With time these soils evolved in to non-allophanic Andisols with hydric properties such as evidenced in profiles from the Cajas massif located in the western central Cordillera. However soils at the Fierro Urcu massif and at the Oña plateau at the eastern Cordillera formed on a non pyroclastic indurated parent material. Compared to non-allophanic Andisols from the Cajas massif, they present similar morphological properties with a dark 50 cm thick carbon-rich (80–120 g kg⁻¹) topsoil with a very low bulk density (<0.65 g cm⁻³) and high water retention. These top soils appear to have originated from fall-out, derived from close and still active volcanoes of Sangay and/or Tungurahua, both located in a distance of 200–250 km NNE of the Oña Massif, respectively. Geochemical determinations of trace and rare earth elements, however, confirm the lack of volcanic ash contribution in the Saraguro and Oña samples based on Eu/Eu* and Ce/Ce* anomalies relative to the lack of such anomalies in the Cajas samples. The Oña and Saraguro soils appear to be the result of a long-lasting double pedogenic process. The basement of the Saraguro soil is a Ferralsol with gibbsite and kaolinite and the Oña soil is a 5 m thick kaolinitic Ferralsol. The upper part of these profiles are the result of a major climatic change with increasing colder conditions, generating an increase in organic matter content and a very acidic environment leading to the instability of kaolinite and gibbsite, thereby liberating large amounts of free aluminium and iron oxides. The evolution of these very highly evolved Ferralsols into soils with Andic properties is proposed to be the result of rapid tectonic uplift calculated at a rate exceeding 0.6 mm/year in the region leading to a general decrease in temperature limiting carbon mineralization and favouring the formation of organo-metallic complexes. The soils studied here reveal compelling new evidence and information about the uplift of a part of the Ecuadorean Andes.
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What caused ocean/climate changes that drove Marinoan deglaciation, and the subsequent genesis of Ediacaran cap carbonates remains unclear. To address this issue, we examined the Hg records in Ediacaran cap carbonates from shelf to slope depositional settings in exposures from South China. These cap carbonates show higher total Hg (THg) concentrations (4.9 to 405 ppb), most of which are comparable to that observed in carbonates deposited during non-LIPs periods. The lack of THg/TOC anomalies in these cap carbonates suggests that background volcanic activity, rather than a short-term large igneous province event, drove the Marinoan deglaciation. The cap carbonates show positive Δ 199 Hg values (0.18 to 0.34 ‰) in slope settings and slightly negative to slightly positive Δ 199 Hg values (− 0.16 to 0.11 ‰) in shelf settings, suggesting a binary mixing of seawater-and terrestrial-derived Hg in early Ediacaran Ocean. We infer that the accumulation of greenhouse gases, due to ongoing volcanic emissions of CO 2 and enhanced release of gas hydrates, triggered global warming. This warming led to melting of sea ice cover, enhanced terrestrial inputs of alkalis (e.g., K + , Na + , Ca 2+ , Mg 2+), and large-scale dissolution of atmospheric CO 2 into seawater, driving widespread deposition of Ediacaran cap carbonates.
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The Sanaga iron ore prospect is a recent discovery in the Nyong Series with a resource estimated at 82.9 Mt at 32.1% Fe and whose origin remains debatable. The mineralization occurs as NE-SW oriented discontinuous lenticular bodies of magnetite-bearing pyroxene-gneisses (MPG) hosted by ortho-derived gneisses. Rare amphibolites are observed. The MPG mineral assemblage consists of quartz-magnetite-orthopyroxene-garnet-tremolite/actinolite exhibiting a granoblastic texture, which is characteristic of granulite facies metamorphism. The granodioritic gneisses show compositional features of the tonalite-trondhjemite-granodiorite association. Their trace and REE element geochemistry indicate their protolith melt resulted from the partial melting of a subducted oceanic slab, with interaction with the overlying mantle wedge during ascent. The amphibolites show enrichment in LILE with negative Ta–Nb and Zr–Hf indicating arc-related magmas generated by partial melting of a sub-continental lithospheric mantle source with metasomatism by subduction-related fluids. The MPG exhibits oxidation-exsolution features characterized by ilmenite lamellae, with hematite fracture-filling in magnetite, and lacks features characteristic of typical BIF such as LREE depletion relative to HREE, positive Eu, La, and Y anomalies. Based on the results of this study, we interpret the Sanaga MPG as a possible skarn-type mineralization formed by the metamorphism/metasomatism of a possible BIF protolith. The results of this study compare with similar magnetite-rich mineralization in the São Francisco craton in northeastern Brazil and enhance the correlation of pre-drift reconstructions of the São Francisco–Congo Cratons.
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The carbonates of the Dodguni area of the Chitradurga greenstone belt, Dharwar Craton, India were studied to understand the Archean diagenetic and palaeo‐depositional conditions using carbon and oxygen isotopes along with whole‐rock geochemistry. These carbonates show significant variation in δ13C and δ18O (−1.73‰ Vienna Peedee Belemnite [VPDB] to −0.45‰ VPDB and δ18O vary from −13.51‰ VPDB to −8.46‰ VPDB, respectively). The rare earth element (REE) + Y (rare earth elements and yttrium) of the studied carbonate rocks exhibit flat and uniform patterns (PrSN/YbSN = 0.4–1), slight positive La, Eu and Gd anomalies (CeSN/CeSN* = 0.8–0.9; EuSN/EuSN* = 0.7–1.4 and GdSN/GdSN* = 2–2.3, respectively) with slight positive Ce anomalies (PrSN/PrSN* = 0.84–0.86) and superchondritic Y/Ho ratios (Y/Ho = 29–45; chondritic Y/Ho = 28). Their negative δ13C (−1.75‰ to −0.45‰) values are attributed to the influence of higher bio‐productivity during their deposition and oxidation of organic carbon. The geochemical and isotopic systematics suggest that the Dodguni limestones are not affected by the diagenetic and metamorphic processes and record the REE geochemistry of the ancient seawater in which they were precipitated. The comprehensive geochemical including the isotopic studies of the Archean carbonate rocks of the Dharwar Craton, indicate their deposition in shallow marine conditions, precipitation in high temperatures with significant hydrothermal input under the influence of high bio‐productivity, thereby providing valuable constraints on the palaeoceanography and geochemical evolution of the Archean sea. The carbonates of the Dodguni area are associated with stromatolitic carbonates, volcanic rocks, banded iron formations and manganese formations, and they were precipitated at shallow depth with variable signatures of hydrothermal inputs.
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he paper characterizes REE mineralization from carbonaceous metapelites of the Paleoproterozoic Mikhailovka Formation, which is the most ancient gold-bearing horizon of the Lena province (Bodaibo district, Irkutsk region). The conditions of metamorphism of the studied samples do not exceed those of chlorite-muscovite subfacies of greenschist facies (ilmenite-pyrrhotite isograde). The metamorphic allanite is a main REE host, which crystallized before the last stage of plastic deformation and folding. The matter source for its formation is related to REE and Th absorbed on organic matter and clay minerals, as well as the detrital monazite. Late hydrothermal-metasomatic processes resulted in its replacement by hydroxycarbonates (hydroxybastnaesite, ancylite) and hydrous phosphates of light REEs (rhabdophane?), while Th precipitated as a hydrous silicate. Findings of low-temperature metamorphic monazite and xenotime are also described.
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