Geochemistry and Mineralogy of Rare Earth Elements (REE) in Bauxitic Ores of the Catalan Coastal Range, NE Spain

Abstract

Karst bauxite deposits are currently investigated as a new resource for rare earth elements (REE) in order to avoid present and future supply shortfalls of these critical metals. The present work focuses on the geochemistry and mineralogy of the REE in karst bauxite deposits of the Catalan Coastal Range (CCR), NE-Spain. It is revealed that the studied bauxitic ores have a dominant breccia and local ooido-pisoidic and pelitomorphic texture. The bauxitic ores are mostly composed of kaolinite and hematite, as well as of lesser amounts of boehmite, diaspore, rutile and calcite. The mineralogy and major element composition indicate incomplete bauxitization of an argillaceous precursor material possibly derived from the erosion of the Mesozoic Ebro massif paleo-high. The studied bauxites are characterized by ∑REE (including Sc, Y) between 286 and 820 ppm (av. 483 ppm) and light REE to heavy REE (LREE/HREE) ratios up to 10.6. REE are mainly concentrated in phosphate minerals, identified as monazite-(Ce) and xenotime-(Y) of detrital origin and unidentified REE-phosphates of a possible authigenic origin. REE remobilization presumably took place under acidic conditions, whereas REE entrapment in the form of precipitation of authigenic rare earth minerals from percolating solutions was related to neutral to slightly alkaline conditions. During the bauxitization process no significant REE fractionation took place and the REE distribution pattern of the bauxitic ores was governed by the REE budget of the precursor material. Finally, adsorption as a main REE scavenging mechanism in the studied CCR bauxite deposits should not be considered, since the presented data did not reveal significant REE contents in Fe-and Mn-oxyhydroxides and clay minerals.

Soil geochemistry, edaphic and climatic characteristics as components of Tunisian olive terroirs: Relationship with the multielemental composition of olive oils for their geographical traceability

“…This finding agrees with that reported by De Sá Paye et al (2016) regarding positive correlations of REE levels in Brazilian soils with the soil OM content. The relative enrichment observed in the Zaghouan soils is probably due to the alkaline barrier at the soil horizon near the bedrock, which causes REE cations to precipitate (Reinhardt et al 2018). This alkaline barrier is due to carbonate dissolution, which provides a neutral to alkaline buffer.…”

Mineralogical and Thermal Characterization of Kaolinitic Clays from Terra Alta (Catalonia, Spain)

“…Finally, it is locally covered by another unit of conglomerates, silts and sandstones. Several deposits of bauxitic and kaolinitic materials occur in the contact between the Cretaceous and Paleocene rocks in the basins located close to the Ebro Basin, such as in the Priorat region [17][18][19]. This is the case of the Terra Alta kaolinite deposits, which are located in a NE-SW fringe of 20 km between Horta de Sant Joan and Pinell de Brai towns, along the Mora Basin.…”

Critical Elements in Supergene Phosphates: The Example of the Weathering Profile at the Gavà Neolithic Mines, Catalonia, Spain

“…The exploration of CE in this type of geological environments is mainly focused on the study of laterites in which significant concentrations of critical elements such as rare earth elements (REE), Sc, or platinum group elements (PGE) have recently been reported in different localities worldwide [8][9][10][11][12][13][14][15][16]. Indeed, weathering processes such as lateritisation alter bedrock minerals and lead to significant changes in the geochemical distribution of several elements.…”