A Review of the Distribution of Critical and Strategic Mineral Raw Materials in the Vein-Type Mineralizations of Vertiskos Unit, Northern Greece †
by
, and
Christos L. Stergiou
1,*
,
Grigorios Aarne Sakellaris
1, 
Vasilios Melfos
1,*
and
Panagiotis Voudouris
2
1
Department of Mineralogy-Petrology-Economic Geology, Faculty of Geology, Aristotle University of Thessaloniki, GR-541 24 Thessaloniki, Greece
2
Department of Mineralogy-Petrology, Faculty of Geology and Geoenvironment, National and Kapodistrian University of Athens, GR-157 84 Athens, Greece
*
Authors to whom correspondence should be addressed.
†
Presented at the 2nd International Conference on Raw Materials and Circular Economy “RawMat2023”, Athens, Greece, 28 August–02 September 2023.
Mater. Proc. 2023, 15(1), 51; https://doi.org/10.3390/materproc2023015051
Published: 24 November 2023
(This article belongs to the Proceedings of The 2nd International Conference on Raw Materials and Circular Economy “RawMat2023”)
Abstract
:Supply risk and economic importance are the key aspects controlling the metals classified as critical. Several of the critical metals are also classified as rare based on their restricted geological availability. In Europe, numerous mineralizations have been reported as being enriched in critical, strategic, and rare metals, and could potentially facilitate the production of these metals as by-products. Within this context, this paper reviews the critical and rare metals incorporated in the vein-type mineralization hosted in the Vertiskos unit in Greece. Several Cenozoic polymetallic mineralizations hosted in quartz veins and metamorphic rocks, which are enriched in Cu–As–Pb–Bi–Ag–Au–Te or in Sb-W are being reported in the region. The polymetallic mineral assemblages are characterized by base metal sulfides—Bi-sulfosalts, Bi-sulfotellurides, and tellurides—associated with Au and Ag. On the contrary, Bi-Te mineral phases are lacking or are completely absent from the Sb-W mineralization. The highest critical metals enrichments are reported from Kolchiko and include Bi (995 ppm), Co (320 ppm) and W (844 ppm). Gold is up to 28.3 ppm in Koronouda, while Ag reaches up to 2433 ppm in Laodikino.
1. Introduction
Critical mineral raw materials are essential for high-tech industries and the development of the low-carbon society [1]. They are characterized by supply risk, economic importance, and, frequently, are restricted in terms of their geological availability; thus, their exploration and exploitation are of a high priority [1]. The European Commission 2023 Critical and Strategic Raw Materials list includes the following critical and strategic metals and metalloids: Al, Sb, As, Be, Bi, Co, Ga, Ge, Hf, Li, Mg, Mn, Nb, Ni, Cu, Sc, Ta, W, V, the groups of heavy (HREE; including also yttrium) and light (LREE) rare earth elements and the platinum group metals (PGM) [2]. In addition, rare metals (e.g., Ag, Au, Cd, Hg, etc.) are of specific significance. Previous publications have revealed new mineralogical and geochemical data on the base, precious, and critical metals incorporated in the Oligocene–Miocene magmatic–hydrothermal mineralization hosted in the Vertiskos unit (e.g., [3,4,5,6,7,8]) (Figure 1). This contribution to the literature constitutes a review of the critical, strategic, and rare metals hosted in the vein-type mineralization of the Vertiskos unit, as the future exploration and exploitation of the metals found in this region could facilitate the production of critical metals (e.g., Bi, Co, Te) as by-products of the main commodities produced (e.g., Cu, Au).
2. Geological Setting
The Ordovician–Silurian Vertiskos unit is a NW-trending polytectonic and polymetamorphosed geotectonic and basement zone stretching from the Greek–North Macedonian border to the Chalkidiki peninsula that hosts several Cenozoic deposits and prospects [6,7,8] (Figure 1). Basement rocks include gneiss, schist, amphibolite, metagabbro, and pegmatoids [12]. The Cenozoic igneous evolution of the region incorporates I-type plutonic, sub-volcanic, and volcanic rocks with Late Paleocene to Pliocene ages characterized by calc-alkaline, high-K calc-alkaline, and shoshonitic affinities [6].
This magmatism was accommodated in a post-collisional setting, while the magmatic–hydrothermal processes were structurally controlled by the Kerdylion and Strymon detachment faults and transtensional to transpressional tectonics (i.e., ENE–WSW-and eastward-trending shears; E–W-, NW–SE-, and NE–SW-trending normal to oblique faults and N–S-trending strike-slip faults) [6,7,8,9,12] (Figure 1). The interplay of magmatism and structural settings resulted in the formation of several mineralization types, mainly between Oligocene and Miocene [4,5,6]. Several porphyry, skarn/carbonate replacement, epithermal, and intrusion-related mineralization types, as well as Fe-Mn- residual oxide deposits, are documented and largely grouped in the Kilkis ore district of the Vertiskos unit and the Chalkidiki ore district of the Permo-Carboniferous to Late Jurassic Kerdylion unit [6,7,9] (Figure 1).
The intrusion-related mineralization includes polymetallic assemblages hosted in quartz veins and/or metamorphic rocks that are enriched in Cu–As–Pb–Bi–Ag–Au–Te or in Sb–W [6,10,11]. Significant polymetallic mineralizations are located across the Vertiskos unit at Laodikino, Koronouda, Stefania–Paliomylos, Kolchiko, Drakontio, and Stanos, while the Sb-W mineralization can be found at Rizana and Philadelphio (Figure 1).
3. Major Cenozoic Vein-Type Mineralization and Critical Metal Distribution at the Vertiskos Unit
The polymetallic mineralization is characterized by base metal sulfides, mainly chalcopyrite, arsenopyrite, and pyrite. In addition, a variety of Bi-sulfosalts, Bi-sulfotellurides, and tellurides associated with Au and Ag can be found [13,14] (Table 1).
Based on ore assemblages, mineral chemistry, and fluid inclusion studies, two stages of magmatic–hydrothermal activity are mainly documented: an early, higher-temperature stage rich in Fe-As with arsenopyrite- and pyrite-dominated polymetallic massive veins and a later, lower-temperature stage related to the polymetallic quartz veins enriched in Bi-sulfosalts and tellurides. Aikinite, hessite, bismuthinite, joseite-B, and pilsenite are the more common Bi and/or Te mineral phases occurring in the polymetallic vein mineralization [6,13,14] (Table 1). On the contrary, Bi-sulfosalts, Bi-sulfotellurides, and tellurides are lacking from the intrusion-related vein mineralizations related to Sb-W enrichment (i.e., Rizana and Philadelphio [11]) (Table 1).
At Laodikino, chalcopyrite hosts pilsenite (Bi4Te3) and native gold inclusions, galena incorporates altaite, and tetrahedrite contains up to 7185 ppm of Ag (Figure 2a,b). At Kolchiko, native bismuth is commonly hosted in galena (Figure 2c,d). In the quartz veins at Koronouda, hessite, pilsenite, tellurobismuthite, and Bi4Te2S (Joseite-B) coexist with native gold, while the gold content after bulk geochemistry is up to 28.3 ppm [7]. At Drakontio, the presence of native gold (Au < 22.5 ppm; bulk geochemistry) is correlated with the occurrence of matildite, emplectite, and aikinite [7]. Argentopentlandite is found in the quartz veins at Stefania–Paliomylos and Koronouda [7]. At Stanos, mineral phases of the bismuthinite–aikinite and lillianite–gustavite series, along with minerals of the Bi-Te-S-Se system (cf., Voudouris et al. [14]), represent a complex assemblage of Bi-sulfosalts, Bi-sulfotellurides, and tellurides [13]. On the contrary, Bi-sulfosalts, Bi-sulfotellurides, and tellurides are lacking from the intrusion-related vein-type mineralizations enriched in Sb-W (i.e., Rizana and Philadelphio, [9]). In these mineralizations, Sb and W oxides and hydroxides are mainly found as minor mineral phases due to supergene processes (Table 1).
Based on the published bulk geochemical data, the vein-type mineralization is enriched in Cu–As–Pb–Bi–Ag–Au–Te, with Au up to 28.3 ppm at Koronouda; Ag up to 2433 ppm at Laodikino; and Bi, W, and Co up to <995 ppm, <844 ppm, and <320 ppm, respectively, at Kolchiko [11]. Other enrichments include Cd (<247 ppm), Hg (<187 ppm), Se (<59 ppm), and V (<10 ppm) at Laodikino, as well as Te (<3 ppm) at Kolchiko [11]. Antimony is up to 7 wt.% in the polymetallic quartz veins from Laodikino and is mainly hosted in tetrahedrite. The Sb-W-enriched vein-type mineralizations (i.e., at Rizana and Philadelphio) are depleted in other critical metals [11]. The stibnite mineralization at Rizana mainly comprises W (<45 ppm), Co (<33 ppm), and V (<23 ppm) [11].
4. Discussion and Conclusions
At the Vertiskos unit, the vein-type mineralization was formed during the regional Cenozoic magmatic and structural evolution from magmatic–hydrothermal fluids at mesothermal to low to intermediate sulfidation epithermal conditions [7,13] (Figure 3). Locally, they are restricted in extended shear zones at the transition between ductile and brittle deformation, demonstrating retrograde greenschist facies metamorphism [7,11,13]. Bismuth- and Te-bearing melts are thought to be scavengers of gold in the polymetallic vein-type mineralization [6,14]. The various Bi-sulfosalts, Bi-sulfotellurides, and tellurides that are incorporated in these mineralizations in close relation with native gold support the Au scavenger character of the initial polymetallic melts [6,14].
The schematic model of the vein-type mineralization and the porphyry–epithermal systems found at the Vertiskos unit is shown in Figure 3. The vein-type mineralizations are hosted in metamorphic rocks and in shear zones and were formed under transpressional to transtensional tectonic settings mainly along the border between Vertiskos unit and the Circum–Rhodope belt. On the contrary, the porphyry–epithermal systems were formed in an extensional setting. Critical and rare metals are variably associated with this mineralization. Nevertheless, enrichments in Bi, Te, and Au can be found in both mineralization groups. For the vein-type mineralization, this may be an indication for concealed proximal and/or distal magmatic intrusions and magmatic–hydrothermal mineralizing processes set along or near shear zones [6,11,13,14].
Author Contributions
Conceptualization, C.L.S., V.M.; writing—original draft preparation, C.L.S.; writing—review and editing, G.A.S., V.M., P.V. All authors have read and agreed to the published version of the manuscript.
Funding
This research study received no external funding.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
Data are contained within the article.
Acknowledgments
The authors would like to thank the three anonymous reviewers for their comments and suggestions, which significantly improved the manuscript. The authors would like to thank Charalampos Vasilatos especially for editorial handling.
Conflicts of Interest
The authors declare no conflict of interest.
References
- Humphreys, D. The mining industry and the supply of critical minerals. In Critical Metals Handbook; Gunn, G., Ed.; John Wiley & Sons: Hoboken, NJ, USA, 2014; pp. 20–40. [Google Scholar]
- European Commission, Study on the Critical Raw Materials for the EU 2023—Final Report; Publications Office of the European Union: Luxemburg, 2023; p. 160.
- Arvanitidis, N.D. New metallogenetic concepts and sustainability perspectives for non-energy metallic minerals in Central Macedonia, Greece. Bull. Geol. Soc. Greece 2010, 43, 2437–2445. [Google Scholar] [CrossRef]
- Christidis, C.; Serafimovski, T.; Arvanitidis, N.; Michael, C.; Tasev, G. 3D modeling tools jointly applied on Gerakario (Greece) and Kadiica (FYROM) porphyry copper mineralisations. In Proceedings of XX CBGA Congress; Beqiraj, A., Ionescu, C., Christofides, G., Uta, A., Beqiraj Goga, E., Marku, S., Eds.; Buletini i Shkencave Gjeologjike: Tirana, Albania, 2014; pp. 355–358. [Google Scholar]
- Dimou, E. Native minerals in rocks and mineralizations of Greece and their significance. Bull. Geol. Soc. Greece 1989, 23, 207–223. [Google Scholar]
- Voudouris, P.; Spry, P.G.; Melfos, V.; Alfieris, D. Tellurides and bismuth sulfosalts in gold occurrences of Greece: Mineralogical and genetic considerations. In Gold Deposits in Finland; Kojonen, K.K., Cook, N.J., Ojala, V.J., Eds.; Geological Survey of Finland: Espoo, Finland, 2007; Volume 53, pp. 85–94. [Google Scholar]
- Melfos, V.; Voudouris, P. Cenozoic metallogeny of Greece and potential for precious, critical and rare metals exploration. Ore Geol. Rev. 2017, 89, 1030–1057. [Google Scholar] [CrossRef]
- Voudouris, P.; Mavrogonatos, C.; Spry, P.G.; Baker, T.; Melfos, V.; Klemd, R.; Haase, K.; Repstock, A.; Djiba, A.; Bismayer, U.; et al. Porphyry and epithermal deposits in Greece: An overview, new discoveries, and mineralogical constraints on their genesis. Ore Geol. Rev. 2019, 107, 654–691. [Google Scholar] [CrossRef]
- Stergiou, C.L.; Melfos, V.; Voudouris, P.; Papadopoulou, L.; Spry, P.G.; Peytcheva, I.; Dimitrova, D.; Stefanova, E.; Giouri, K. Rare and Critical Metals in Pyrite, Chalcopyrite, Magnetite, and Titanite from the Vathi Porphyry Cu-Au±Mo Deposit, NorthernGreece. Minerals 2021, 11, 630. [Google Scholar] [CrossRef]
- Stergiou, C.L.; Melfos, V.; Voudouris, P.; Papadopoulou, L.; Spry, P.G.; Peytcheva, I.; Dimitrova, D.; Stefanova, E. A Fluid Inclusion and Critical/Rare Metal Study of Epithermal Quartz-Stibnite Veins Associated with the Gerakario Porphyry Deposit, Northern Greece. Appl. Sci. 2022, 12, 909. [Google Scholar] [CrossRef]
- Stergiou, C.L.; Sakellaris, G.A.; Melfos, V.; Voudouris, P.; Papadopoulou, L.; Kantiranis, N.; Skoupras, E. Mineralogy, Geochemistry and Fluid Inclusion Study of the Stibnite Vein-Type Mineralization at Rizana, Northern Greece. Geosciences 2023, 13, 61. [Google Scholar] [CrossRef]
- Mposkos, E.; Krohe, A.; Baziotis, I. Deep tectonics in the Eastern Hellenides uncovered: The record of Variscan continental amalgamation, Permo-Triassic rifting, and Early Alpine collision in Pre-Variscan continental crust in the W-Rhodope (Vertiscos-Ograzden Complex, NGreece). Tectonics 2021, 40, e2019TC005557. [Google Scholar] [CrossRef]
- Bristol, S.K.; Spry, P.G.; Voudouris, P.C.; Melfos, V.; Mathur, R.D.; Fornadel, A.P.; Sakellaris, G.A. Geochemical and geochronological constraints on the formation of shear-zone hosted Cu–Au–Bi–Te mineralization in the Stanos area, Chalkidiki, northern Greece. Ore Geol. Rev. 2015, 66, 266–282. [Google Scholar] [CrossRef]
- Voudouris, P.; Spry, P.G.; Mavrogonatos, C.; Sakellaris, G.A.; Bristol, S.K.; Melfos, V.; Fornadel, A. Bismuthinite derivatives, lillianite homologues, and bismuth sulfotellurides as indicators of gold mineralization at the Stanos shear-zone related deposit, Chalkidiki, northern Greece. Can. Mineral. 2013, 51, 119–142. [Google Scholar] [CrossRef]
Figure 1.
Cenozoic magmatism, structural setting, and mineralization types at the Vertiskos unit and the adjacent Kerdylion unit in Northern Greece (adapted from [9,10,11] and the references therein).
Figure 2.
Photographs of hand-collected specimens from the polymetallic massive veins at Laodikino (a) and from the polymetallic quartz veins at Kolchiko (c). Photomicrographs (plane-reflected light: b,d) of the hypogene mineralization in these veins: (a) Massive pyrite (Py) and arsenopyrite (Apy); (b) native gold (Au) associated with pyrite (Py), as well as chalcopyrite (Cpy) from a polymetallic massive vein; (c) pyrite (Py) and chalcopyrite (Cpy) in quartz (Qtz); (d) pyrite (Py), sphalerite (Sph), chalcopyrite (Cpy), and galena (Gn) with inclusions of native bismuth (Bi) in a polymetallic quartz vein.
Figure 2.
Photographs of hand-collected specimens from the polymetallic massive veins at Laodikino (a) and from the polymetallic quartz veins at Kolchiko (c). Photomicrographs (plane-reflected light: b,d) of the hypogene mineralization in these veins: (a) Massive pyrite (Py) and arsenopyrite (Apy); (b) native gold (Au) associated with pyrite (Py), as well as chalcopyrite (Cpy) from a polymetallic massive vein; (c) pyrite (Py) and chalcopyrite (Cpy) in quartz (Qtz); (d) pyrite (Py), sphalerite (Sph), chalcopyrite (Cpy), and galena (Gn) with inclusions of native bismuth (Bi) in a polymetallic quartz vein.
Figure 3.
Schematic model showing the magmatic–hydrothermal mineralizing processes and tectonic settings at the Vertiskos unit during Cenozoic. Specific enrichments in critical and rare metals are highlighted for the porphyry–epithermal and the vein-type mineralization (modified after [13]).
Figure 3.
Schematic model showing the magmatic–hydrothermal mineralizing processes and tectonic settings at the Vertiskos unit during Cenozoic. Specific enrichments in critical and rare metals are highlighted for the porphyry–epithermal and the vein-type mineralization (modified after [13]).
Table 1.
Overview of the typology, alteration, and textural characteristics of the hypogene mineralization hosted in major vein-type deposits found at the Vertiskos unit (data compiled from [5,6,7,8,9,10,11,13,14]).
| Locality | Mineralization Style | Host Rock | Alteration Style | Metallic Assemblage | Gangue and Alteration Assemblage |
|---|---|---|---|---|---|
| Drakontio | Polymetallic quartz veins | Mica schist | Silicification | Cpy + Py + Gn + Sph + Bm + Au ± Aik ± Emp ± Mtd | Qtz |
| Kolchiko | Polymetallic massive veins | Mica schist | Sericitization | Apy + Py + Cpy + Gn + Po ± Gab ± Bi ± Au ± Ttn ± Ilm ± Rt ± Urn | Ser + Qz + Chl |
| Polymetallic quartz veins | Py + Cpy + Apy + Gn + Sph + Po ± Bi ± Hes ± Tb | ||||
| Quartz-pyrite veins | Py ± Cpy | ||||
| Koronouda | Polymetallic quartz veins | Two-mica gneiss + pegmatoids | Silicification | Cpy + Py + Sph + Po + Gn ± Pn ± Apy ± Cob ± Ttr ± Fb ± Bm ± Tb ± Hes ± Aik ± Ptz ± Syv ± Pils ± Js-B ± Hes ± Au | Qtz |
| Laodikino | Polymetallic massive veins | Two-mica gneiss + chlorite-muscovite schist | Sericitization + chloritization | Apy + Py + Cpy + Sph ± Ttr ± Gn ± Po ± Mag ± Ilm ± Rt ± Cob ± Alt ± Aik ± Pils ± Elc ± Bi | Qz + Ser + Chl + Cal + Brt |
| Polymetallic quartz veins | Py + Cpy + Ttr + Sph + Gn | ||||
| Philadelphio | Massive stibnite and quartz–stibnite veins | Two-mica gneiss + amphibolite + schist | Silicification + chloritization | Stb + Apy + Cpy + Py ± Ccsb ± See ± Kem ± Mrc ± Po ± Sph ± Ttr ± Sbc ± Zkn ± Wf | Qtz |
| Rizana | Massive stibnite and quartz–stibnite veins | Two-mica gneiss + augen gneiss | Silicification + Sericitization | Stb + Bth + Sph + Py + Cpy + Sb ± Wf ± Gn ± Ttr ± Mrc ± Po ± Apy ± Rlg ± As ± Au | Qtz + Brt + Ank + Ser |
| Stanos | Polymetallic massive veins | Orthogneiss + amphibolite + metagabbro + schist | Chloritization + Sericitization + Potassic | Stage I: Py + Apy + Po ± Mol ± Sph | Stage I: Qtz + Bt + Ms + Chl |
| Stage II: Cpy + Sph ± Mol ± Bn ± Bm ± Aik ± Lil ± Gus ± Js-A ± Js-B ± Mtd ± Hes ± Cos ± Pek ± Gld ± Krp ± Szb ± Paa ± Gus ± Ik ± Bi ± Elc | Stage II: Bt + Ms + Chl + Sd + Ap + Mnz + Xtm | ||||
| Stefania– Paliomylos | Polymetallic quartz veins | Two-mica gneiss + pegmatoids | Silicification | Py + Cpy + Sph + Po + Gn ± Apn ± Aik ± Js-B ± Bm ± Gdf ± Cob ± Pils ± Hes ± Au | Qtz |
Abbreviations: Aik = aikinite, Alt = altaite, Apn = argentopentlandite, Apy = arsenopyrite, As = native arsenic, Au = native gold, Bi = native bismuth, Bm = bismuthinite, Bn = bornite, Bth = berthierite, Ccsb = chalcostibite, Cob = cobaltite, Cos = cosalite, Cpy = chalcopyrite, Elc = electrum, Emp = emplectite, Fb = freibergite, Gab = galenobismuthinite, Gdf = gersdorffite, Gld = gladite, Gn = galena, Gus = gustavite, Hes = hessite, Ik = ikunolite, Ilm = ilmenite, Js-A = joseite-A, Js-B = joseite-B, Kem = kermesite, Krp = krupkaite, Lil = lillianite, Mag = magnetite, Mol = molybdenite, Mrc = marcasite, Mnz = monazite, Mtd = matildite, Paa = paarite, Pek = pekoite, Pils = pilsenite, Po = pyrrhotite, Pn = pentlandite, Ptz = petzite, Py = pyrite, Rlg = realgar, Sb = native antimony, Sbc = stibiconite, Sd = siderite, See = seelite, Stb = stibnite, Sph = sphalerite, Syv = sylvanite, Szb = salzburgite, Tb = tellurobismuthite, Ttn = titanite, Ttr = tetrahedrite, Rt = rutile, Urn = uraninite, Wf = wolframite, Xtm = xenotime, Zkn = zinkenite.
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Stergiou, C.L.; Sakellaris, G.A.; Melfos, V.; Voudouris, P. A Review of the Distribution of Critical and Strategic Mineral Raw Materials in the Vein-Type Mineralizations of Vertiskos Unit, Northern Greece. Mater. Proc. 2023, 15, 51. https://doi.org/10.3390/materproc2023015051
AMA Style
Stergiou CL, Sakellaris GA, Melfos V, Voudouris P. A Review of the Distribution of Critical and Strategic Mineral Raw Materials in the Vein-Type Mineralizations of Vertiskos Unit, Northern Greece. Materials Proceedings. 2023; 15(1):51. https://doi.org/10.3390/materproc2023015051
Chicago/Turabian StyleStergiou, Christos L., Grigorios Aarne Sakellaris, Vasilios Melfos, and Panagiotis Voudouris. 2023. "A Review of the Distribution of Critical and Strategic Mineral Raw Materials in the Vein-Type Mineralizations of Vertiskos Unit, Northern Greece" Materials Proceedings 15, no. 1: 51. https://doi.org/10.3390/materproc2023015051
APA StyleStergiou, C. L., Sakellaris, G. A., Melfos, V., & Voudouris, P. (2023). A Review of the Distribution of Critical and Strategic Mineral Raw Materials in the Vein-Type Mineralizations of Vertiskos Unit, Northern Greece. Materials Proceedings, 15(1), 51. https://doi.org/10.3390/materproc2023015051
