REEs in the North Africa P-Bearing Deposits, Paleoenvironments, and Economic Perspectives: A Review

Abstract

A review of the compositional features of Tunisia, Algeria, and Morocco phosphorites is proposed in order to assess and compare the paleoenvironmental conditions that promoted the deposit formation as well as provide information about their economic perspective in light of growing worldwide demand. Since these deposits share a very similar chemical and mineralogical composition, the attention was focused on the geochemistry of rare earth elements (REEs) and mostly on ΣREEs, Ce and Eu anomalies, and (La/Yb) and (La/Gd) normalized ratios. The REEs distributions reveal several differences between deposits from different locations, suggesting mostly that the Tunisian and Algerian phosphorites probably were part of the same depositional system. There, sub-reducing to sub-oxic conditions and a major REEs adsorption by early diagenesis were recorded. Conversely, in the Moroccan basins, sub-oxic to oxic environments and a minor diagenetic alteration occurred, which was likely due to a different seawater supply. Moreover, the drastic environmental changes associated to the Paleocene–Eocene Thermal Maximum event probably influenced the composition of Northern African phosphorites that accumulated the highest REEs amounts during that span of time. Based on the REEs concentrations, and considering the outlook coefficient of REE composition (Koutl) and the percentage of critical elements in ΣREEs (REEdef), the studied deposits can be considered as promising to highly promising REE ores and could represent a profitable alternative source for critical REEs.

Geotechnical Characterization of Phosphate Mining Waste Materials for Use in Pavement Construction

“…The chemical composition confirms that the mineral composition of phosphatic limestone and limestone contains four main minerals: carbonatefluorapatite, calcite, dolomite, and quartz. The results are in agreement with the findings of [25,[34][35][36][37][38][39][40][41][42][43].…”

Environmental Technologies to Treat Rare Earth Element Pollution: Principles and Engineering

“…Some of the REE deposits contain ΣREE up to 2000 µg/g (Emsbo et al, 2015), although the composition of these rocks mostly depends on their type and origin. The ΣREE of Northern African (Tunisian and Algerian) phosphorites exhibit a median of 314.5 µg/g (maximum value 1018.34 µg/g) and 289.21 µg/g (maximum value 1759.41 µg/g), respectively, and fall in the second highest range after the US deposits that are the most REE-enriched (average = 4394 µg/g) (Buccione et al, 2021).…”

Geochemical and Isotopic (Nd, Sr) Tracing of the Origin of REE Enrichment in the Cambrian Georgina Basin Phosphorites

“…(2015) and Buccione et al. (2021) identified enrichment of REE in phosphate‐rich rocks (phosphorites) currently mined for phosphate fertilizer in the US and worldwide, while Wu et al. (2018) and Emsbo et al.…”

“…However, Valetich et al (2022), demonstrated large regional-scale variations in REE content of Cambrian phosphorites of the Georgina Basin: In this case, the authors proposed links between phosphorite REE content and the composition of the basement lithology and resulting in groundwater input into marine basins. Other studies have demonstrated systematic variations in total REE concentrations in seawater with depth (Alibo & Nozaki, 1999;Elderfield & Greaves, 1982;Osborne et al, 2015), while continental run-off, atmospheric input, bottom sediment flux and groundwater discharge are also known to influence the concentration, ratios and isotopic signatures of REE in oceans and coastal waters (Abbott et al, 2015;Buccione et al, 2021;Johannesson et al, 2017;Lacan et al, 2012;Molina-Kescher et al, 2018). Furthermore, REE concentrations in phosphorites can vary up to orders of magnitude even between individual layers of a deposit or between textural types ("pelletal" grainstones vs. "non-pelletal" microcrystalline carbonate fluorapatite mudstone -microsphorite) (Auer et al, 2017;Cook, 1972;Valetich et al, 2022;Watkins et al, 1995).…”

“…The projected risk to supply of rare earth elements (REEs -herein the lanthanide group La-Lu, including Y) required for a transition to a low-carbon future and technological advancement (Chakhmouradian & Wall, 2012), has emphasized the need to find new potential sources of REE. Recently, Emsbo et al (2015) and Buccione et al (2021) identified enrichment of REE in phosphate-rich rocks (phosphorites) currently mined for phosphate fertilizer in the US and worldwide, while Wu et al (2018) and Emsbo et al (2015) demonstrated the feasibility of solvent extraction of REEs as a by-product of phosphate mining. Accordingly, phosphorites are now considered an important potential source for the industrial supply of REEs in the future.…”