Trace elements distribution in stream sediments of an abandoned U mining site in the Eastern Carpathians, Romania, with particular focus on REEs

https://doi.org/10.1016/j.chemer.2021.125761Get rights and content

Abstract

Trace elements distribution, including rare earth elements (REEs), in stream sediments of an abandoned U mining site in the Eastern Carpathians, Romania, were of high concern of interest in the present work. A total number of 40 riverbed sediments samples collected from the Bistricioara River and local tributaries (Primatar, Bradul, Prisacani, Barasau, Grintiesul Mare and Valea Seaca) were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) and energy dispersive X-ray fluorescence spectrometry (XRF). All REEs including La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu were identified and quantified in the present work using ICP-MS technique. For other 24 elements (Ti, V, Cr, Co, Zn, Li, Be, Rb, Sr, Y, Sc, Zr, Nb, Sb, Ba, Ta, W, Pb, U, Ni, Cu, Mo, As, Th) similar information was obtained either by ICP-MS or XRF techniques. The impact and the relevance of the obtained data base might be significant at a local scale of about 50 km2.

Enrichments of some trace elements of interest in comparison to the upper continental crust allowed discrimination between various mineralization processes specific for the investigated areas. Uranium mineralization and Paltin-type (Pb, Zn) mineralization seems to be specific for the NW area of the investigated region. Negative anomaly characteristic for the upper crustal rocks was identified for Eu and Ce elements. Evidences were obtained also for the existence of ultramafic rocks (Ni, Cr, Co and V) in the investigated riverbed sediments. The observation was also confirmed by the binary plots analysis of Th/Cr vs. Th/Co and Cr/V vs. Y/Ni pairs. From the investigated tributaries to Bistricioara River, Barasau seems to exert the highest influence on the abundances of REEss in the entire area. Most probably some chemical parameters such as the pH of the water streams influence leaching and depletions of some chemical constituents in various minerals specific for the region.

The existence of magnetite, garnets, pyrite and sillimanite minerals was confirmed by SEM-EDAX and XRF analysis, as well by optical microscopy. Principal Component Analysis runs confirmed the association of some chemical elements in the riverbed sediments in close connection with the minerals from which they originate.

The present work reports for the first time upon the authors knowledge clear scientific evidence and chemical information concerning the geology and geochemistry, i.e. transition metals, high field strength elements, alkali and alkaline earth elements, rare earth elements (REEs) and others, in stream sediments crossing the Tulghes-Grinties mining area (Eastern Carpathians, Romania). For the analysed REEs this is the first study reporting consistent information on the concentrations of the entire array of both light REEs (six elements) and heavy REEs (ten elements) in Bistricioara Basin stream sediments. Relevant scientific data related to geochemical characteristics of ultramafic rocks existent in the investigated area were also generated. Moreover, data reported in the present work might be considered as a reference geochemical database relevant for the investigated area, which can be used as a trustworthy input for a systematic national geochemical atlas.

Introduction

Rare earth elements (REEs) and other trace elements present in many geological settings are assigned as useful chemical parameters to understand the geological and geochemical processes taking place in the Earth. Their insolubility and resistance to mobilization during geological processes such as weathering, diagenesis and metamorphism make them important tools for the geochemical characterization of the Earth (Mc Lennan and Taylor, 2012). Generally, REE are found in many minerals but only few of them, such as monazite and bastnaesite, are rich enough to be considered of economic interest (Neary and Highley, 1984). Immobile elements and REEs are usually concentrated in riverbed sediments and can be used as tracers for the sediments’ sources (Taylor and McLennan, 1985).

The REEs-rich mineralized carbonate-rich veins of the Eastern Carpathians’ Igneous Complex from Romania are referred to some extend as potential important REEs resources in Europe (Honour et al., 2018). Some mineralizations (Paltin type) in Valea Seaca and Argintaria-tributaries of the Barasau River are genetically related with some vein mineralizations from Ditrau Igneous Complex (Gyula, 1998; Ionescu, 2000). The age of the Paltin type mineralizations is Upper Jurassic- to Early Cretaceous and they are similar or at least close to the Ditrau Complex mineralizations (Ionescu, 2000). The area is charcaterised by rocks containing galena and chalcopyrite, sulphides and REE and uranium deposits (Ionescu, 2000).

Important mineral resources are found in the area, with special focus on the Uranium deposits (Tulghes-Grinties) located in mica schists and feldspathic quartzites from the Bretila Group (Bejenaru and Cioloboc, 1993). Geological surveys suggest the area as the largest uranium deposit in Romania with valuable economic potential (Tofan et al., 2016). A study published in 2020 reports for Tulghes-Grinties area reduced radiological hazard from naturally occurring radionuclides within riverbed sediments near uranium deposits (Sandu et al., 2020). Moreover, the fingerprint of serpentinite ultramafic rocks present in the Prisacani River represents a potential suitable tool for understanding the geological setting, as the geochemistry may differ based on the influence of some parameters such as the temperature of formation and the nature of primordial fluid. The geochemical composition of serpentinites is usually influenced by the geological settings especially due to the influences derived from their formation temperature and the nature of primordial fluid (Deschamps et al., 2013). Nevertheless, the source of the serpentinite has not yet been found.

The present work aims to document the geochemical and mineralogical characteristics of stream/riverbed sediments of the main left tributaries of the Bistricioara River (Primatar, Grintiesul Mare, Bradul, Prisacani, Barasau and Valea Seaca) in the Central Group of the Eastern Carpathians, i.e. Bistritei Mountains. Of special concern in the present work are rare earth elements (REE) and selected trace elements in terms of quantitative assessments and their origin sources.

Section snippets

Geological framework

The studied area is located in Bistricioara hydrographic basin and it lies within two geological units known as Crystalline–Mesozoic in the Center (or Median Dacides) and Carpathian flysch in the East (Fig. 1). The Eastern Carpathians are geomorphological segments of the European Alpine mountain belt, with a length of about 200 km, corresponding to a relatively young tectonic setting which was formed during the Miocene collision (Kräutner and Bindea, 1995).

The origins of the Carpathians

Sample preparation

A number of 40 stream sediments samples were collected in May 2019 from Bistricioara’s left-bank tributaries (Primatar – 8 samples, Grintiesul Mare – 8 samples, Valea Seaca – 6 sample, Basarau – 5 samples, Prisacani – 4 samples, Bradul – 4 samples, Bistricioara – 5 samples), the sector spanning between the villages of Capu Corbului and Grinties. The sampling network was established based on accessibility. Each composite sample was generated from at least five sampling points that covered

Trace elements

Data related to quantified values in the concentration of selected elements (Ti, V, Ni, Cu, Zn, Li, Be, Rb, Sr, Y, Sc, Zr, Nb, Sb, Ba, Ta, W, Th, U) are presented in Table 1 while for the identified REEs (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) concentration values are presented in Table 2. Both Table 1, Table 2 present individual data for each analysed stream sediment sample accompanied by minimum, maximum and mean for each set of samples.

Trace elements in stream riverbed sediments in comparison with the upper continental crust (UCC)

A better way of understanding the geogenic and anthropogenic contribution is to compare the variability on the concentrations of the identified elements to the average values from the upper continental crust (UCC) (Maftei et al., 2018). The geology of the Bistricioara basin predominantly consists of metamorphic rocks and, in a lesser proportion, of sedimentary rocks. A comparison between the trace elements composition of the Bistricioara and its tributaries and the average of upper continental

Conclusions

A significant number of rare earth elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb Lu) and other metals of potential interest (Ti, V, Cr, Co, Zn, Li, Be, Rb, Sr, Y, Sc, Zr, Nb, Sb, Ba, Ta, W, Pb, U, Ni, Cu, Mo, As, Th) were identified and quantified in water stream sediments collected from a geographical area with relevance to about 50 km2 in the neighborhood of an U mining site (Tulghes-Grinties) in the Eastern Carpathians, Romania.

The enrichment in trace elements, such as Pb and

CRediT authorship contribution statement

Data curation: Marius C. Sandu and Laurentiu V. Soroaga. Formal analysis: Marius C. Sandu, Laurentiu V. Soroaga, Ovidiu Chiscan, Gabriel O. Iancu, Cecilia Arsene and Romeo I. Olariu. Methodology: Marius C. Sandu, Laurentiu V. Soroaga and Ciprian Chelariu. Validation: Marius C. Sandu, Laurentiu V. Soroaga, Cecilia Arsene, Romeo I. Olariu. Writing - original draft: Marius C. Sandu, Laurentiu V. Soroaga, Sorin I. Balaban, Ciprian Chelariu, Gabriel O. Iancu and Romeo I. Olariu. Writing - review &

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

References (59)

  • J. Huang et al.

    Vanadium: global(bio)geochemistry

    Chem. Geol.

    (2015)
  • J. Janeczek et al.

    Structural formula of uraninite

    J. Nucl. Mater.

    (1992)
  • E. Kelepertzis et al.

    Origin, mineral speciation and geochemical baseline mapping of Ni and Cr in agricultural topsoils of Thiva Valley (central Greece)

    J. Geochem. Explor.

    (2013)
  • A.E. Maftei et al.

    Chemical and mineralogical composition of fluvial sediments (Bistrita River,Romania): geogenic vs. Anthropogenic input into rivers on its way through mining areas

    Chemie Der Erde - Geochem.

    (2018)
  • G. Meinhold

    Rutile and its applications in earth sciences

    Earth. Rev.

    (2010)
  • M. Munteanu et al.

    The east-carpathian crystalline-mesozoic zone (Romania): paleozoic amalgamation of gondwana-and east european craton-deroved terranes

    Gondwana Reserch

    (2003)
  • E. Pal-Molnar et al.

    Origin of Mafic and ultramafic cumulates from Ditrău Alkaline Massif, Romania

    Lithos

    (2015)
  • P.N. Ranasinghe et al.

    Application of geochemical ratios for delineating gem-bearing areas in high grade metamorphic terrains

    Appl. Geochem.

    (2005)
  • J. Rubin et al.

    The mobility of zirconium and other "immobile" elements during hydrothermal alteration

    Chem. Geol.

    (1993)
  • R.L. Rudnick et al.

    Composition of the continental crust

    Treatise on Geochemistry

    (2003)
  • R.L. Rudnick et al.

    Composition of the continental crust

    Earth System and Environmental Sciences. Treatise on geochemistry (Second Edition)

    (2014)
  • G. Alexandrescu et al.

    Geological Map of Romania, Scale 1:200.000

    (1968)
  • S. Anupam et al.

    Mineralogy and geochemistry of the Mahi River sediments in tectonically active western India: Implications for Deccan large igneous province source, weathering and mobility of elements in a semi-arid climate

    Geochim. Cosmochim. Acta

    (2013)
  • I. Balintoni et al.
    (1980)
  • C. Bejenaru et al.

    Uranium exploration and production in Romania: case histories and prospects. IAEA-TECDOC-823, recent developments in uranium resources and supply

  • R.G. Cawthorn et al.

    Platinum group element, chromium, and vanadium deposits in mafic and ultramafic rocks

    Econ. Geol.

    (2005)
  • M.D. Cocker

    Distribution of Selected Elements in Stream Sediments, Stream Hydrogeochemistry, and Geology of the Flint River Basin, Georgia. Atalanta, Bulletin 129

    (1998)
  • F.J. Dahlkamp

    Uranium Deposits of the World Europe

    (2016)
  • H.G. Dill et al.
    (2012)
  • View full text