The Potential for REE and Associated Critical Metals in Coastal Sand (Placer) Deposits of Greece: A Review

Abstract

The rare earth elements (REEs) are characterized by the European Union (EU) as critical raw materials with a significant risk of supply because of their broad utility in both traditional and emerging technological applications. The growing demand for REE has caused a flurry in the search for new REE deposits in Europe and elsewhere in the world, and is also linked to rising exploitation efforts in a variety of geological settings. To this end, Greece appears to be a promising candidate to become a leading EU country in terms of REE by virtue of its natural endowment in sedimentary heavy mineral deposits (placers) along its long coastline. The present review focuses on the distribution, abundance, and bulk geochemistry of REEs and other critical metals (Ta, Nb, Co) associated with placer deposits of Greece, and specifically with geologically young heavy mineral sand accumulations developed proximal to felsic plutonic source rocks. These deposits are also enriched in the actinides uranium (U) and thorium (Th), as both of these metals are typically associated with REE-rich minerals such as xenotime, monazite, thorite, allanite, and zircon. Previous studies have employed a variety of analytical techniques down to nano-meter scale with the aim to elucidate the mineralogy and distribution of REE and associated actinides in Greek beach placers. In view of this mineralogically-intensive background, the present review focuses chiefly on bulk geochemical characteristics of the same deposits and the variations thereof between two major geographical regions (northern Greece, southern Aegean) and across individual placer occurrences within them. In this framework, we present comprehensive compositional comparisons between the different deposits, highlighting the geological sub-environments wherein they occur, their distinctive sources and geochemical signatures, and their potential economic significance in terms of REE and other critical metal enrichments where applicable.

Effect of Mineralogy on the Beneficiation of REE from Heavy Mineral Sands: The Case of Nea Peramos, Kavala, Northern Greece

“…Zircon is another REE-hosting phase, with relatively higher concentration in heavy REE (HREE) (253-890 mg/kg) relative to light REE (LREE) (8-44 mg/kg) [18,23]. Apatite is a common fine-grained accessory phase disseminated in silicate minerals.…”

“…In the last decade, there is an increasing number of geochemical and mineralogical studies that have been carried out on the coastal areas of Kavala [14][15][16][17][18][19], Sithonia Peninsula of Chalkidiki [20], Touzla Cape [21], and the area of Maronia, Samothrace [22]. Most of these studies focused on the characterization of the placers and their natural radioactivity ( [23] and references therein). Previous studies have demonstrated that the heavy minerals, monazite, allanite, titanite, uraninite, zircon, and apatite, are traced in the Kavala black sands, derive from the Symvolon/Kavala pluton, a deformed granodioritic complex of Miocene age (Table 1) [6,9,14,24].…”

Detrital zircon U–Pb geochronology and geochemistry of the Riachuelos and Palma Sola beach sediments, Veracruz State, Gulf of Mexico: a new insight on palaeoenvironment

“…A significant positive correlation between Al 2 O 3 and K 2 O for the Riachuelos (r = 0.81) and Palma Sola (r = 0.87) beach sediments indicates that a considerable proportion of K is associated with fine-grained sediments or phyllosilicates (Etemad-Saeed et al 2015;Greggio et al 2018;Udayanapillai et al 2020). Al 2 O 3 against TiO 2 reveals a negative correlation for the Riachuelos (r = − 0.36, n = 15) and Palma Sola (r = − 0.01, n = 20) beach sediments, indicating that TiO 2 is not associated with aluminous clays or its association with titano-magnetite and ilmenite (Nagarajan et al 2015(Nagarajan et al , 2017Papadopoulos et al 2019). Similarly, a weak correlation between Al 2 O 3 and P 2 O 5 for the Riachuelos (r = − 0.70, n = 15) and Palma Sola (r = 0.13, n = 20) beach sediments suggests P 2 O 5 content is associated with detrital minerals, probably apatite (Fig.…”

Mineralogy, Geochemistry and Provenance of Coastal Sands from Greece: New Insights on the REE Content of Black Coastal Sands from Aggelochori Area, N.-Greece

“…There is a particular focus from the scientific community as far as REE's deposits. In the case of beach placer deposits, there are numerous studies referring to areas of economic value due to their REE and other critical elements content [1]. Particularly in Greece there are several publications studying the REE and natural radioactivity content in beach placer deposits [1].…”

“…In the case of beach placer deposits, there are numerous studies referring to areas of economic value due to their REE and other critical elements content [1]. Particularly in Greece there are several publications studying the REE and natural radioactivity content in beach placer deposits [1]. Coastal sands from Aggelochori area close to Thessaloniki (N.-Greece) have been studied by Filippidis et al 1997 [2] but there are no studies of source formation of the beach placers, up to now.…”