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Article

New Ag-Rich Mn-Zn±Pb Vein Mineralization at the Mavro Xylo Manganese Oxide Deposit, Drama, Greece

by
George Soulamidis
1,*,
Christina Stouraiti
1,
Panagiotis Voudouris
1,* and
Harilaos Tsikos
2
1
Department of Geology and Geoenvironment, National and Kapodistrian University of Athens, Panepistimiopolis, 15784 Athens, Greece
2
Department of Geology, University of Patras, Rio Campus, 26504 Patra, Greece
*
Authors to whom correspondence should be addressed.
Minerals 2024, 14(9), 955; https://doi.org/10.3390/min14090955
Submission received: 29 July 2024 / Revised: 18 September 2024 / Accepted: 20 September 2024 / Published: 21 September 2024
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Abstract

:
The manganese deposits at the Kato Nevrokopi area are located in the Drama Basin (Northern Greece) and belong to the Rhodope Metamorphic Province. The deposits were previously exploited for several supergene Mn-oxide ore bodies of massive, battery-grade nsutite, spatially associated with fault zones in the vicinity of Oligocene granitic intrusions. We conducted detailed geological, mineralogical, and geochemical investigations at the Mavro Xylo deposit, which led to the identification of Ag-rich Mn-Zn±Pb vein-type mineralization. The studied paragenesis appears to have developed during two hydrothermal stages: stage I, characterized by the mineral assemblage rhodonite–quartz–rhodochrosite–pyrophanite–pyrite–galena–Te bearing argentite–sphalerite–wurtzite–alabandite, and stage II, dominated by Ag-rich, Mn-Zn±Pb oxides in the form of fracture-fills along a high-angle NE-SW fault zone in brecciated marbles. Bulk analyses of the stage-II oxide assemblage yielded concentrations of Ag up to 0.57 wt.%. In the veins, wurtzite is present in bands, succeeded by manganese oxides, while calcite and quartz are the main gangue minerals. We placed particular emphasis on the occurrence of Ag in high concentrations within distinct manganese oxides. Major silver carriers include Zn-bearing todorokite, chalcophanite, and hydrous Pb-Mn oxide. The vein-type mineralization at Mavro Xylo shares many characteristics with other intermediate-sulfidation epithermal precious metal-rich deposits associated with high Mn concentrations. The evolution of the mineral paragenesis indicates a change in the physicochemical attributes of the ore-forming fluids, from initially reducing (stage I) to oxidizing (stage II). Although the origin of the initial ore-forming fluid remains to be constrained, the above redox change is tentatively attributed to the increasing incursion of meteoric waters over time.

1. Introduction

Manganese oxy/hydroxides exhibit remarkable adsorption properties and act as scavengers in geological environments for base metals, aiding in the discovery of new base metal deposits [1,2,3]. With the increasing demand for base and critical metals, identifying new deposits in Europe has become crucial [4]. Moreover, manganese has been assigned to the list of critical and strategic metals for the EU as a vital component in green energy applications, particularly in lithium-ion batteries as a cathode material [5,6].
Manganese–silver ores occur in different parts of the world and have been a focus of geochemical exploration due to their importance as a mineral resource for both manganese and silver [7,8,9]. Silver exists either encapsulated or in the crystal lattice of manganese oxides [10]. A variety of up to fifteen types of manganese oxides have been identified in Mn-Ag deposits worldwide [8,9,11,12]. Among these, three manganese oxides play a fundamental role in silver deportment within manganese–silver ores, namely cryptomelane, todorokite, and chalcophanite [11,13,14].
The Kato Nevrokopi manganese deposit (Northern Greece) is the largest manganese deposit exploited in Greece [15]. Kato Nevrokopi is located approximately 60 km northwest of Drama in northern Greece and represented the primary mining center for battery-grade manganese oxide ore from 1950 to 1994. Nimfopoulos et al. (1991, 1997) [15,16] characterized Mn mineralization at Kato Nevrokopi to be a result of progressive oxidation of rhodochrosite-sulfide veins, leading to a paragenetic sequence of MnO gel–todorokite–nsutite–chalcophanite–birnessite–cryptomelane–pyrolusite. Manganese ore deposits are structurally controlled and developed along E–W and NW–SE fault zones [15,16,17]. Apart from a few mineral-chemical analyses conducted on manganese ore bodies in the Kato Nevrokopi area [16,17], many genetic aspects of the deposits remain poorly constrained. Notably, the origin of these deposits remains unclear, and understanding is limited due to previous research primarily focusing on the geochemical properties of the battery-grade supergene manganese oxide ore driven by the region’s mining activities.
This study provides a more detailed investigation of the manganese deposits in the Kato Nevrokopi area, particularly at Mavro Xylo, and presents a new hypogene argentiferous manganese ore assemblage in the Mavro Xylo mine. It investigates the mineralogy and mineral chemistry of the argentiferous mineral assemblage at Mavro Xylo and provides new paragenetic constraints for the origin of Ag-rich Mn-Zn±Pb mineralization. Our results also offer new insights into hydrothermal manganese metallogenesis through comparisons with similar Ag- and base metal-bearing Mn mineralization elsewhere.

2. Regional Geology

2.1. Rhodope Metamorphic Core Complex

The Kato Nevrokopi area, as well as the whole Drama district, is part of the Rhodope massif, which represents a metamorphic core complex in the internal Hellenides (Figure 1). The structure, magmatic, and tectono-metamorphic characteristics of the Massif have been the center of attention for many researchers [18,19,20].
The Rhodope Metamorphic Core Complex, located in the northeastern Hellenides region, forms the core of the arc-type Hellenic orogenic belt. This core complex comprises intricate alpine nappe stacks of various metamorphic continental and oceanic units [21,22]. These nappes were sequentially emplaced through intense compressional tectonics and thrusting from the Jurassic to the Tertiary, driven by multiple subduction processes, high to ultra-high pressure metamorphism, and the closure of oceanic basins [19]. Extensional Tertiary tectonic activity has reworked the compressional structures between the nappes into low-angle normal detachment faults. The extensional phase was also marked by high-grade metamorphism, emplacement of syn- to post-tectonic granitoid intrusions (i.e., Vrondou, Panorama, Granitic, and Kavala, Figure 1, Figure 2 and Figure 3), and extensive migmatite formation [23,24].
The structural configuration of the Rhodope Province in the study area is relatively straightforward and comprises several distinct units. These include the Falakron marble series, a thick and highly strained carbonate platform of undetermined age situated between the Strymon and Nestos Rivers. On its southwestern edge, the series is bordered by a brittle, low-angle, southwest-dipping shear zone, which is overlain by the “Kerdylion Unit” and a cover of intensely deformed, unmetamorphosed Neogene sediments (Figure 1). Initially, this shear zone was thought to be a northeast-vergent Neogene thrust. However, Dinter and Royden (1993) [25] reinterpreted this tectonic contact as a southwest-vergent, low-angle normal fault, known as the Strymon Valley detachment. They demonstrated that this structure played a crucial role in the exhumation of the Falakron marble series during the Neogene period.
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Figure 1. Simplified geological map of the Greek Rhodope Massif in northern Greece showing the main tectonic units referred to in the text (modified from Voudouris et al. 2016 [26] and Melfos and Voudouris, 2017 [27]).
Figure 1. Simplified geological map of the Greek Rhodope Massif in northern Greece showing the main tectonic units referred to in the text (modified from Voudouris et al. 2016 [26] and Melfos and Voudouris, 2017 [27]).
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2.2. Geology and Mineralization of the Falakro Mt

The Falakron marble series in the broad area corresponds to the “lower tectonic unit” of the Greek Rhodope Province, as defined by Papanikolaou and Panagopoulos (1981) [28] and Dinter and Royden (1993) [25]. This series is exposed between the Strymon and Nestos Rivers [29,30,31]. The structural thickness of the marble increases northeastwards within the Rhodope core complex, ranging from less than 200 m in southwestern Mount Pangeon and the Menikion Mountains to over 5000 m in the central Falakron and Lekanis Mountains [32,33]. The primary lithology is a massive marble that is highly sheared and recrystallized (Figure 2). Micaceous gneiss, two-mica schist, and actinolite schist appear as local intercalations in the form of lenses and layers (from less than 1 m to over 400 m thick). The age of the Falakron series is poorly constrained [34].
The mineral compositions and assemblages found in mica schists and impure marbles across the mainland exposure of the Falakron series are characteristic of greenschist facies regional metamorphism, specifically the quartz–albite–epidote–biotite subfacies [35]. The major structural features of the Falakron marble include upright, kilometer-scale, gently northeast-plunging, open anticlines, and synclines. These ductile deformational elements are all attributed to a single, early Tertiary Alpine compressional event [36].
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Figure 2. Generalized geological map of the Drama basin area, northeastern Greece, showing the granodiorite intrusions and the manganese mining sites (redrawn from [16,25]).
Figure 2. Generalized geological map of the Drama basin area, northeastern Greece, showing the granodiorite intrusions and the manganese mining sites (redrawn from [16,25]).
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Previous studies report the Mn mineralization at Kato Nevrokopi as epigenetic, hosted by a thick sequence of marbles (i.e., Falakron upper marbles) and an alternating sequence of gneisses, mica schists, and marble located beneath them (Figure 2 and Figure 3) [17,29]. Mineralization mainly occurs within faults and veins, cross-cutting marbles and extending into host rocks [15,16,17]. Based on Mn mineralization and its geological setting, Nimfopoulos and Pattrick [15] described three ore zones: (i) the deeper, mineralized sulfide-carbonate-rich zone, which can be found as a deeply eroded relic in the southernmost mine of Pyrgi. (ii) The upper mineralized Mn-oxide-rich zones, reported close to the surface at Mavro Xylo and other mines, such as the 25th Km mine situated NW of Mavro Xylo (Figure 3) and the Karposluk and Tartana mines, both occurring along the E–W fault zone (Figure 2). Lastly, (iii) secondary manganese oxides found in formations described as karstic cavity fills originating from zone (ii). In the upper zones of Mn mines, manganese is reported to be concentrated in ‘black calcite’, which consists of coarsely crystalline calcite intergrown with, and replaced by, todorokite along cleavages [16,17,36,37].
The age of hydrothermal mineralization was determined by K/Ar dating using separates of hydrothermal muscovite [36]. The results yielded an age of 32.5–33.0 Ma, contemporaneous with magmatism in the Drama area. Mavro Xylo was the primary manganese mine in the area, located 5 km SE from the Granitis intrusion (Figure 3).
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Figure 3. Geological map of granitis intrusion and Mavro Xylo (modified from Papapetros [38], a geological map of IGME, Kato Nevrokopo Sheet).
Figure 3. Geological map of granitis intrusion and Mavro Xylo (modified from Papapetros [38], a geological map of IGME, Kato Nevrokopo Sheet).
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3. Methods

Seven samples were collected from a major vein exposed at the surface and within an abandoned gallery at the Mavro Xylo mine (Figure 4). All samples were processed for mineralogical and geochemical analyses. The bulk mineralogical composition of the samples was examined by X-ray diffraction using a Siemens D–5005 diffractometer (SIEMENS, Munich, Germany) at the Faculty of Geology & Geoenvironment, National and Kapodistrian University of Athens. The device has a Cu anode and was operated at a generator voltage of 40 kV and a current of 55 mA. The goniometer 2θ values ranged from 2° to 70°, with a scan rate of 0.02 s per step. Mineral phases were identified using the Joint Committee for Power Diffraction Standards (JCPDS) file and DIFFRAC software EVA (V.6, Bruker Corporation, Billerica, MA, USA) provided by Bruker. Analysis of major and selected trace elements was conducted on bulk ore powdered samples using an X-ray Fluorescence spectrometer equipped with a wavelength dispersive system, specifically the ZSX Primus IV device from Rigaku instruments (Rigaku, Tokyo, Japan) at the Laboratory of Metallurgy, National and Technical University of Athens, Greece. Samples were prepared as pressed tablets of 32 mm by mixing 4 g of sample powder and 1 g of binding material (HWC).
Five polished-thin sections and 11 polished blocks were studied by optical microscopy at the Faculty of Geology and Geoenvironment, National and Kapodistrian University of Athens and by scanning electron microscopy (SEM) with a Jeol JSM-IT500 instrument (Jeol USA, Inc., Peabody, MA, USA), equipped with an OXFORD Ultim Max 100 analytical device (Oxford Inc., Oxford, UK), at the Hellenic Survey for Geology and Mineral Exploration, Athens, Greece. The operating conditions were 20 kV accelerating voltage and 1.5 nA beam current with a 4 μm diameter beam. Precise chemical compositions of sulfides, oxides/hydroxides, silicates, and carbonates were further determined using a JEOL JXA 8530F field emission gun electron microprobe microanalyzer (Jeol USA, Inc., Peabody, MA, USA) at Utrecht University. Operating conditions were 20 kV and 20 nA, with a beam diameter of <1 mm. The following X-ray lines were used: SiKa, FeKa, MgKa, AlKa, SKa, KKa, CaKa, MnKa, ZnKa, CuKa, AsLa, AgLa, and PbMa. Diopside (for Si and Ca), chalcopyrite (for Fe, S, and Cu), forsterite (for Mg), jadeite (for Al), tephroite (for Mn), sphalerite (for Zn), indium arsenide (for As), pure silver (for Ag), and galena (for Pb) were used as standards.

4. Results

4.1. Mineralization at Mavro Xylo

Based on field observations and ore textures of this study, we distinguished two types of mineralization at Mavro Xylo (Figure 4 and Figure 5): (1) vein-type and (2) breccia-type. Two major fault systems are present in the Mavro Xylo deposit, controlling hydrothermal fluid flow and ore deposition (Figure 3 and Figure 4): a low-angle SW–NE trending fault (probably part of a detachment system in the area) and a high-angle NW–SE normal fault, which cross-cuts the previous one (Figure 4a–c). Rhodochrosite associated with disseminated pyrite is developed in veins alongside the low-angle SW–NE fault at higher topographic levels of the deposit (Figure 4a). A hydrothermal rhodonite–quartz–rhodochrosite-bearing vein was located at deeper topographic levels and was described from the Mavro Xylo area for the first time (Figure 5a). Sulfide-manganese oxide veins are developed along strike the high-angle normal faults at deeper levels of the deposit (Figure 4d). These veins are banded and characterized by the early deposition of sulfides at the margins of the vein (i.e., wurtzite, the polymorph of ZnS), followed by the deposition of a mixture of manganese oxide minerals in the inner part within a carbonate-quartz gangue assemblage (Figure 5b,c). Breccia-type mineralization is characterized by fragments of marbles cemented by Ag-bearing manganese oxides and calcite, occasionally dark colored due the inclusion of Mn oxides (Figure 4e,f).

4.2. Mineralogy

4.2.1. Sulfides

Sulfides at Mavro Xylo (i.e., galena, sphalerite, pyrite, and alabandite) occur either as inclusions in hydrohetaerolite and silver-rich manganese oxides, or inclusions of pyrite, galena, Te-bearing argentite in quartz in association with rhodonite and rhodochrosite or in massive form as distinct bands within veins (i.e., wurtzite) (Figure 5 and Figure 6).
Pyrite is the dominant sulfide in rhodonite–quartz–rhodochrosite-bearing veins. It forms inclusions in quartz in association with rhodonite (Figure 6a). The chemical analysis of pyrite is given in Table 1 and Table S1. The analyzed pyrite contains As up to 1 wt.%. Ag (up to 0.36 wt.%) in pyrite is probably attributed to submicroscopic inclusions of Ag-bearing phases (Table 1, Figure 6b).
Te-bearing Argentite (Ag2S) forms inclusions (up to 2 μm) in pyrite alongside galena (Figure 6b). Based on SEM-EDS data (Table S1), argentite contains up to 9.09 wt.%. Te.
Galena forms inclusions in pyrite from rhodonite–quartz–rhodochrosite-bearing veins (Figure 6b). It is also forms inclusions in silver-rich manganese oxides (Figure 6c). EDS analyses of galena are given in Table S1.
Sphalerite is observed in the rhodonite–quartz matrix and contains up to 2.6 wt.% Mn and 0.57 wt.% Fe, corresponding to 2.44 mole % FeS (Figure 6d, Table 1).
Alabandite (MnS) is found as small grains up to 5 μm in size in association with manganese oxides and seems to postdate the formation of adjacent Ag-todorokite (Figure 6e).
Wurtzite, a (Zn,Fe)S polymorph, was verified from its X-ray diffraction pattern (Figure S1). It occurs as massive, reddish-brown bands overlaid by manganese oxides such as todorokite–hetaerolite–chalcophanite (Figure 5).

4.2.2. Manganese Oxides

Todorokite [(Na,Ca,K,Ba,Sr)1-xMn6O12*3–4.5(H2O)] is the most abundant Mn oxide in Mavro Xylo, accompanying wurtzite in the vein-style mineralization. While it can occur either as a hypogene or supergene mineral in manganese deposits [1,3,40], todorokite at Mavro Xylo is thought to be of hydrothermal origin, and the first phase of manganese oxide to form followed by hydrothermal calcite and quartz (Figure 6e,f). EPMA and SEM-EDS data (Table 2 and Table S2) show that, except for Ca and K, which are common in todorokite in various concentrations, it also contains up to 3.65 wt.% Zn and 2 wt.% Ag. The average structural formula of todorokite, based on EMPA data, is (Mn1.762+K0.02Ca0.09Zn0.10Ag0.03)2Mn6O12*4H2O, demonstrating the incorporation of 1.76 apfu Mn2+ in the structure. The assemblage of todorokite–wurtzite in Mavro Xylo was verified by X-ray diffraction (Figures S1 and S2).
Hetaerolite (ZnMn2O4) and hydrohetaerolite (Zn2Mn4O8*H2O) (IMA unapproved) are rare zinc–manganese minerals found in the Mavro Xylo area. Both mineral phases postdate todorokite and contain up to 27 wt.% Zn (Table 3 and Table 4; Figure 6c). Even though all other manganese oxide minerals at Mavro Xylo have considerable Ag concentrations, hetaerolite and hydrohetaerolite analysis showed negligible Ag content (Table 2 and Table S2). This is likely because their spinel-like structure, like hausmannite, exhibits the weakest adsorption capacity among manganese oxides since the adsorption properties of manganese oxides are closely linked to their structural characteristics [1,41]. The presence of hetaerolite/hydrohetaerolite together with todorokite and chalcophanite was verified by X-ray diffraction patterns (Figure S2).
Chalcophanite (ZnMn3O7*3H2O) appears to replace hetaerolite at Mavro Xylo (Figure 6e,g). The Zn concentration varies from 5 wt.% up to 19 wt.% (Table 2 and Table S2), suggesting a zinc-deficient variety of chalcophanite [9,42,43]. Chalcophanite, together with todorokite, represent two Mn-oxide mineral phases with the highest Ag concentrations in the mineralization. The Ag content in chalcophanite ranges from 0.6 wt.% to 2.2 wt.% (Table 2 and Table S2). The Ca content also reaches values up to 2.26 wt.%. Based on EPMA data, the structural formula of the chalcophanite studied here is (Ca0.1Mn0.602+Zn0.21Ag0.09)Mn3O7*3H2O.
Hydrous lead manganese oxide (PbMn5O11*5H2O) is a minor constituent occurring with chalcophanite or within todorokite after galena (Figure 6f,g). This mineral phase was first described at Aurora mines together with argentiferous manganese oxides [9] and is also reported from Mavro Xylo. The Pb content in this mineral phase ranges from 9.82 to 20.86 wt.% (Table 2 and Table S2). Additionally, Ag contents reach values of up to 1 wt.%. The structural formula of hydrous Pb-Mn oxide is (Fe0.13Mn0.052+Zn0.14Pb0.62Ag0.03)Mn5O11*5H2O.

4.2.3. Gangue Minerals

Rhodonite [CaMn3Mn(Si5O15)], a manganese silicate mineral, was found in the Mavro Xylo area and is a dominant early mineral phase (Figure 6a,d,h) in hydrothermal veins. It incorporates minor amounts of Al2O3 substituting for SiO2 (up to 0.85 wt.%), and Ca, Mg, and Fe (up to 5.07, 0.26, and 0.2 wt.%, respectively) substituting for Mn (Table 3 and Table S3).
Quartz occurs following rhodonite, a major host of sulfides and Mn oxides in mineralization (Figure 6a). The mineral assemblage of rhodonite–quartz–rhodochrosite was verified by X-ray diffraction analysis (Figure S3).
Rhodochrosite is a Mn-carbonate mineral phase found together with quartz, postdating rhodonite (Figure 6h). Its chemical composition is given in Table 3. Its Ca concentration varies from 1 to 12 wt.%.
Pyrophanite (MnTiO3) has needle-like inclusions in quartz (Figure 6i).
Muscovite accompanies sulfides and oxides in Mavro Xylo mineralization (Figure 6d,e). Low amounts of manganese are present in muscovite, reaching values up to 1.78 wt.% (Table S3).
Calcite is abundant in Mavro Xylo, either as manganiferous black calcite alongside brecciated marble (Figure 4e) or as grey–white calcite in manganese oxide-bearing veins (Figure 6a,b). Manganese content in calcite varies from 1.5 to 1.9 wt.% (Table 3).
Monazite [(Ce,La,Nd)PO4] occurs mainly as minute grains (10–15 μm in size), included in todorokite. Monazite grains display a close textural association with muscovite (Figure 6f). Praseodymium, Gd, and Sm were found at values of 2.92 wt.%, 1.96 wt.%, and 1.7 wt.%, respectively (Table S3).

4.3. Bulk Ore Geochemistry

Six Mn ore samples from the Mavro Xylo vein were analyzed by X-ray fluorescence, and the results are shown in Table 4. The samples record manganese abundances from 48.6 wt.% to 66 wt.%. Notable base metal impurities in the manganese oxide ore reflect the mineral chemical characteristics already described: Pb content varies from 0.01 wt.% to 0.66 wt.%, Zn content ranges from 0.31 wt.% to 16.2 wt.%, Cu ranges from 0.01 wt.% to 0.8 wt.%, and S content ranges from 0.06 wt.% to 0.56 wt.%. Ag concentrations are particularly notable, ranging from 0.01 wt.% to 0.57 wt.%, although, in two samples, Ag was below the detention limit (b.d).
Table 4. XRF results (wt.%) of bulk manganese oxide ore from Mavro Xylo.
Table 4. XRF results (wt.%) of bulk manganese oxide ore from Mavro Xylo.
SampleK Mg CaAl Si Mn Fe Zn Pb Cu Ag As Sb S
MX23-10.50.16.590.360.7948.60.240.310.080.080.010.180.09b.d.
MX23-20.3b.d.4.561.241.8950.30.530.990.01b.d.b.d.0.05b.d.b.d.
MX23-40.12b.d.0.920.611.255.50.311.010.240.01b.d.0.05b.d.b.d.
MX23-50.312.13121.090.86660.57.090.660.80.430.080.020.06
MX23-60.51.023.9831.8959.80.8216.20.380.710.290.030.020.23
MX23-70.342.0111.40.963.0764.50.556.070.60.740.570.040.040.56

5. Discussion

5.1. Paragenetic Sequence and Physicochemical Conditions of Formation

Based on field relationships and petrographic data (optical microscopy, SEM, EPMA), we present a paragenetic sequence for the vein-type mineralization at Mavro Xylo below (Figure 7). We suggest two-stage evolution for mineralization in the area:
  • Stage I ore is dominated by the presence of disseminated sulfides, in accordance with previous findings of [15,16,17] for the broad Kato Nevrokopi area. At Mavro Xylo, initial deposition of the manganese silicate rhodonite is followed by rhodochrosite and quartz, the latter also including lesser pyrite, galena, Te-bearing argentite, and sphalerite (Figure 6a,b,d). Additionally, this stage is characterized by the deposition of wurtzite and alabandite. Stage I thus records notable enrichments in Mn-, Zn-, Ag-, and Te.
  • The second stage (stage II) is characterized by the dominance of manganese oxide minerals. Stage II is marked by the early deposition of Ag-Zn-bearing todorokite, followed by hetaerolite and hydrohetaerolite, and paragenetically later by Ag-bearing chalcophanite and hydrous Pb-Mn oxides. Quartz, calcite, muscovite, and monazite-(Ce) are gangue minerals.
Todorokite and chalcophanite are complex manganese oxide minerals with structures ([3 × 3] tunnel structure for todorokite and layered for chalcophanite) that can host many cations due to their strong adsorption capability for alkali and alkaline earth and transition metals [1]. Although Ag-Mn ore deposits are globally significant as metal sources, there are limited studies on the distribution of Ag in manganese oxides sensu stricto [6,44]. SEM-EDS and EPMA results on todorokite and chalcophanite from Mavro Xylo constrained their elemental compositions with respect to both Ag and Zn. For further understanding of the partitioning of Ag and Zn into both manganese oxides, correlation diagrams are presented in Figure 8. A broadly positive correlation between Ag and Zn in todorokite indicates that both elements occupy the tunnel structure of todorokite (Figure 8a). Binary plots between Mn-Ag and Mn-Zn display an apparent negative correlation in both cases (Figure 8b,c), suggesting that Ag and Zn substitute for Mn2+, thus supporting the late-stage origin and metal uptake of these minerals [45]. In contrast, the EPMA data of chalcophanite define a broadly negative correlation between Ag and Zn, indicating that these two metals substitute each other in the structure of chalcophanite (Figure 8d).
Manganese incorporation into early silicates (rhodonite), carbonates (rhodochrosite), oxides (pyrophanite), and sulfides (alabandite) takes place in its divalent form (Mn2+), supporting more reducing fluid conditions during the initial stages of mineralization. Manganese incorporated into stage-II minerals (todorokite, hetaerolite, hydro-hetaerolite, and chalcophanite) occurs mainly in the trivalent and/or tetravalent form, thus suggesting increasingly oxidized conditions during stage II ore deposition, likely due to meteoric fluid infiltration [46,47]. The presence of Te during mineralization indicates a primary magmatic contribution, given that Te is usually transported in the form of magmatic vapors [48]. In summary, Mavro Xylo vein-type mineralization is thought to have evolved from earlier, relatively reducing magmatic–hydrothermal conditions towards more oxidizing conditions due to the later incursion of meteoric waters. Future applications of stable isotope analyses and fluid inclusion studies are bound to provide critical constraints on the conditions of ore formation during both ore-forming stages.

5.2. Comparison of Mavro Xylo Veins with Other Epithermal Mn-Precious Metal Mineralization

The vein-type mineralization at Mavro Xylo is structurally controlled and shares common structural attributes (i.e., banding and brecciation) with epithermal styles of mineralization elsewhere [49]. Although rhodonite has been reported from carbonate replacement [50,51] and skarn deposits [52], it is also a typical mineral in epithermal-style mineralization when found together with Mn carbonates [53,54,55,56]. Moreover, the studied mineralization lacks other skarn-type mineralogy of diagnostic value (e.g., johannsenite, spessartine, and piedmontite) [20] that would support a contact metasomatic environment of deposition. Similarly to Mavro Xylo, the presence of early stage rhodochrosite, together with rhodonite, quartz, and sulfides, has been previously reported in hydrothermal manganese deposits of Hokkaido, Japan [53,57], Bisbee and Tombstone, Arizona [53,58,59], and Philipsburg and Butte, Montana [53,58,60]. Such assemblage is typical of intermediate sulfidation epithermal mineralization [53,61,62], as is, for example, the precious and base metal epithermal deposit of Banská Hodruša in Slovakia [56,63].
Two ZnS polymorphs are present within the epithermal NW–SE trending veins at Mavro Xylo, namely wurtzite and sphalerite. The presence of both wurtzite and sphalerite has also been reported from other epithermal mineralization in Greece, for example, at St. Philippos in western Thrace [64], Achla Tarla [65], Panormos in Tinos Island [66], and at Lavrion [67,68]. The presence of sphalerite with 2.4 mole % FeS at Mavro Xylo is compatible with intermediate sulfidation fluid states during mineralization [49]. Sphalerite, with a similar composition to that found at Mavro Xylo, is described from the intermediate sulfidation Mn-rich epithermal veins of the Rosia Montana Au-Ag deposit in Romania [69]. Moreover, the alabandite-bearing silver-rich manganese oxide mineralization at Mavro Xylo resembles other Ag- and Mn-rich epithermal deposits, such as the Santo Toribio epithermal deposit in Northern Peru [70].
Among the manganese oxides, todorokite, hetaerolite, and hydrohetaerolite are common constituents in Mn-rich epithermal-style deposits [1,3]. The minerals hetaerolite and hydrohetaerolite have been previously reported at Milos Island [3], Madjarovo, Eastern Rhodope [71], Rodna, Romania [72], as well as Hokkaido, Japan [73], in all cases in connection with vein-type Pb-Zn-Ag-Mn epithermal mineralization.
Silver-rich manganese oxides/hydroxides are considered quite rare and are typically found near Ag-Pb-Zn or Ag-Mn deposits as part of the epithermal environment [6,9,74]. In Mavro Xylo, todorokite records high concentrations of Zn and up to 2 wt.% Ag and can thus be reported as argentian todorokite. Argentian todorokite was initially identified in the Aurora mines (Treasure Hill), Hamilton, Nevada, USA [9], where it is associated with black calcite and has silver concentrations reaching up to 4 wt.% [9,75].
The occurrence of silver in these manganese minerals is complex and debated, with suggestions of silver existing as a native element bound to manganese oxide [9,12] or within the crystal lattice of the manganese oxides (such as cryptomelane) replacing potassium or other elements [8,9,76,77]. Despite their industrial significance, these mineral phases have not been extensively studied due to the low Ag recovery in metallurgical processes [7,8,13,78].
In summary, geological, mineralogical, and textural characteristics of the studied veins at Mavro Xylo indicate a fault-controlled, intermediate sulfidation, Ag-rich Mn-Zn±Pb epithermal style of mineralization. Partial leaching and remobilization of Ag, at the expense of earlier sulfide-dominant assemblages, could have played a key role in its subsequent incorporation into later-stage Mn oxides.

6. Conclusions

Based on the findings of this study, the following conclusions may be drawn:
(1)
New field evidence, including mineralogical and geochemical data from the Mavro Xylo Mn-Zn-Ag±Pb deposit at Kato Nevrokopi, Drama, Greece, indicates epithermal vein-type mineralization as part of the deposit.
(2)
Mineralization is interpreted to have formed during two evolutionary hydrothermal stages: (I) an early sulfide-bearing stage consisting of pyrite, galena, Te-rich argentite, sphalerite, wurtzite, and alabandite and (II) an oxide-bearing stage, with initial deposition of todorokite, followed by hetaerolite, hydrohetaerolite, and chalcophanite.
(3)
Silver was primarily introduced into the mineralization in the form of Te-bearing argentite and later remobilized and bound in the structure of Ag-bearing Mn-oxides such as todorokite and chalcophanite, as demonstrated in Mavro Xylo mineralization.
(4)
Mineralization evolved from more reducing (sulfide-bearing) towards more oxidized (Mn oxide-bearing) conditions, likely due to the increasing incursion of meteoric waters in the ore system.

Supplementary Materials

The following supporting information can be downloaded at https://www.mdpi.com/article/10.3390/min14090955/s1, Figure S1: X-ray diffraction pattern of the ore sample from the epithermal vein consisting of wurtzite (Wur)–todorokite (Tdr) with calcite (Cal) and quartz (Qz) as gangue minerals, Figure S2: X-ray diffraction pattern of the silver-rich manganese oxide ore sample containing hetaerolite (Hta), todorokite (Tdr), and chalcophanite (Cph), Figure S3: X-ray diffraction pattern of gangue minerals containing Rhodonite (Rdn)–Quartz (Qz)–Rhodochrosite (Rds), Table S1: Representative SEM-EDS analyses of sulfides from Mavro Xylo Mn mineralization (in wt.%), Table S2: Representative SEM-EDS data of hetaerolite and silver-rich manganese oxides from Mavro Xylo, Kato Nevrokopi area (in wt.%), Table S3: Representative SEM-EDS data of gangue minerals.

Author Contributions

Methodology, G.S., C.S., P.V., and H.T.; software, G.S.; validation, G.S., C.S., P.V., and H.T.; formal analysis, G.S.; investigation, G.S., C.S., P.V., and H.T.; resources, G.S., C.S., P.V., and H.T.; data curation, G.S.; writing—original draft preparation, G.S.; writing—review and editing, G.S., C.S., P.V., and H.T.; visualization, G.S., C.S., H.T., and P.V.; supervision, C.S., P.V., and H.T. All authors have read and agreed to the published version of the manuscript.

Funding

The Hellenic Foundation for Research and Innovation (HFRI) supported G.S.’s research under the 4th Call for HFRI PhD Fellowships (Fellowship Number: 11210).

Data Availability Statement

Data are contained within the article and Supplementary Materials.

Acknowledgments

X-ray fluorescence analyses were conducted in the School of Mining and Metallurgical Engineering, NTUA. Additionally, the authors would like to thank Paul R.D. Mason, Tilly Bouten, and Eric Hellebrand of Utrecht University for their assistance.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Post, J.E. Manganese Oxide Minerals: Crystal Structures and Economic and Environmental Significance. Proc. Natl. Acad. Sci. USA 1999, 96, 3447–3454. [Google Scholar] [CrossRef] [PubMed]
  2. Spinks, S.C.; Uvarova, Y.; Thorne, R.; Anand, R.; Reid, N.; White, A.; Ley-Cooper, Y.; Bardwell, N.; Gray, D.; Meadows, H.; et al. Detection of Zinc Deposits Using Terrestrial Ferromanganese Crusts. Ore Geol. Rev. 2017, 80, 484–503. [Google Scholar] [CrossRef]
  3. Papavassiliou, K.; Voudouris, P.; Kanellopoulos, C.; Glasby, G.; Alfieris, D.; Mitsis, I. New Geochemical and Mineralogical Constraints on the Genesis of the Vani Hydrothermal Manganese Deposit at NW Milos Island, Greece: Comparison with the Aspro Gialoudi Deposit and Implications for the Formation of the Milos Manganese Mineralization. Ore Geol. Rev. 2017, 80, 594–611. [Google Scholar] [CrossRef]
  4. Zhang, S.E.; Bourdeau, J.E.; Nwaila, G.T.; Ghorbani, Y. Emerging Criticality: Unraveling Shifting Dynamics of the EU’s Critical Raw Materials and Their Implications on Canada and South Africa. Resour. Policy 2023, 86, 104247. [Google Scholar] [CrossRef]
  5. European Commission COM. Establishing a Framework for Ensuring a Secure and Sustainable Supply of Critical Raw Materials—Present a List of Strategic Raw Materials (Annex 1) and Critical Raw Materials (Annex 2). 2023, p. 160. Available online: https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A52023PC0160 (accessed on 29 July 2024).
  6. Soulamidis, G.; Kourmousi, M.; Mitsopoulou, C.A.; Stouraiti, C. Electrochemical Behavior of Natural Manganese Oxides: Transformation Mining Waste into Energy Storage Materials. Minerals 2024, 14, 455. [Google Scholar] [CrossRef]
  7. Tian, Q.; Jiao, C.; Guo, X. Extraction of Valuable Metals from Manganese–Silver Ore. Hydrometallurgy 2012, 119–120, 8–15. [Google Scholar] [CrossRef]
  8. Fan, C.; Wang, L.; Fan, X.; Zhang, Y.; Zhao, L. The Mineralogical Characterization of Argentian Cryptomelane from Xiangguang Mn–Ag Deposit, North China. J. Mineral. Petrol. Sci. 2015, 110, 214–223. [Google Scholar] [CrossRef]
  9. Calderon-Rodarte, J.; Lopez-Valdivieso, A.; Aragon-Pina, A.; Reyes-Bahena, J.L.; Gallegos-Garcia, M.I.L.; Zapata-Velazquez, A.; Robledo-Cabrera, A. Mineralogy and Silver Distribution in Argentiferous Manganese Ores from La Encantada Mines in Mexico. Physicochem. Probl. Miner. Process. 2017, 53, 591–600. [Google Scholar] [CrossRef]
  10. Chase, C.K. Treatment of manganiferous silver ores for recovery of silver in view of changed precious metal economics. In Proceedings of the 110th AIME Annual Meeting, Chicago, IL, USA, 22–26 February 1981; pp. 81–86. [Google Scholar]
  11. Radtke, A.S.; Taylor, C.M.; Hewett, D.F. Aurorite, Argentian Todorokite, and Hydrous Silver-Bearing Lead Manganese Oxide. Econ. Geol. 1967, 62, 186–206. [Google Scholar] [CrossRef]
  12. Li, S.Y.; Li, Y.; Lai, L.R. Technological Mineralogy of Silver in Argentiferous Deposits of China; Geological Press: Beijing, China, 1996. [Google Scholar]
  13. Gomez-Caballero, J.A.; Villasenor-Cabral, M.G.; Santiago-Jacinto, P.; Ponce-Abad, F. Hypogene ba-rich todorokite and associated nanometric native silver in the San Miguel Tenango mining area, Zacatlan, Puebla, Mexico. Can. Miner. 2010, 48, 1237–1253. [Google Scholar] [CrossRef]
  14. Fan, C.; Li, Q.; Chu, B.; Lu, G.; Gao, Y.; Xu, L. Silver binding in argentiferous manganese oxide minerals investigated by synchrotron radiation X-ray absorption spectroscopy. Phys. Chem. Miner. 2018, 45, 679–693. [Google Scholar] [CrossRef]
  15. Nimfopoulos, M.K.; Michailidis, K.M.; Christofides, G. Zincian Rancieite from the Kato Nevrokopi Manganese Deposits, Macedonia, Northern Greece. Geol. Soc. Lond. Spec. Publ. 1997, 119, 339–347. [Google Scholar] [CrossRef]
  16. Nimfopoulos, M.K.; Pattrick, R.A.D. Mineralogical and Textural Evolution of the Economic Manganese Mineralisation in Western Rhodope Massif, N. Greece. Mineral. Mag. 1991, 55, 423–434. [Google Scholar] [CrossRef]
  17. Michailidis, K.M.; Nicholson, K.; Nimfopoulos, M.K.; Pattrick, R.A.D. An EPMA and SEM Study of the Mn-Oxide Mineralization of Kato Nevrokopi, Macedonia, Northern Greece: Controls on Formation of the Mn4+ Oxides; Geological Society: London, UK, 1997; Volume 119, pp. 265–280. [Google Scholar] [CrossRef]
  18. Burg, J.; Ricou, L.; Ivano, Z.; Godfriaux, I.; Dimov, D.; Klain, L. Syn-metamorphic Nappe Complex in the Rhodope Massif. Structure and kinematics. Terra Nova 1996, 8, 6–15. [Google Scholar] [CrossRef]
  19. Burg, J.-P. Rhodope: From Mesozoic Convergence to Cenozoic Extension. Review of Petro-Structural Data in the Geochronological Frame. J. Virtual Explor. 2012, 42, 1–44. [Google Scholar] [CrossRef]
  20. Tombros, S.; Kokkalas, S.; Triantafyllidis, S.; Fitros, M.; Tsikos, H.; Papadopoulou, L.; Voudouris, P.; Zhai, D.; Skliros, V.; Perraki, M.; et al. Genesis of a New Type of Mangan Skarn Associated with Peraluminous Granitoids in Greece. Chem. Geol. 2023, 623, 121369. [Google Scholar] [CrossRef]
  21. Kilias, A.; Falalakis, G.; Sfeikos, A.; Papadimitriou, E.; Vamvaka, A.; Gkarlaouni, C. The Thrace Basin in the Rhodope Province of NE Greece—A Tertiary Supradetachment Basin and Its Geodynamic Implications. Tectonophysics 2013, 595–596, 90–105. [Google Scholar] [CrossRef]
  22. Schmid, S.M.; Fügenschuh, B.; Kounov, A.; Maţenco, L.; Nievergelt, P.; Oberhänsli, R.; Pleuger, J.; Schefer, S.; Schuster, R.; Tomljenović, B.; et al. Tectonic Units of the Alpine Collision Zone between Eastern Alps and Western Turkey. Gondwana Res. 2020, 78, 308–374. [Google Scholar] [CrossRef]
  23. Brunn, J.H. Contribution à l’étude géologique du Pinde septentrional et d’ une partie de la Macédoine occidnetale. Ann. Géol. Pays Helléniques 1956, 7, 1–358. [Google Scholar]
  24. Kilias, A. The Alpine Geological History of the Hellenides from the Triassic to the Present—Compression vs. Extension, a Dynamic Pair for Orogen Structural Configuration: A Synthesis. Geosciences 2023, 14, 10. [Google Scholar] [CrossRef]
  25. Dinter, D.A.; Royden, L. Late Cenozoic extension in northeastern Greece: Strymon Valley detachment system and the Rhodope metamorphic core complex. Geology 1993, 21, 4548. [Google Scholar] [CrossRef]
  26. Voudouris, P.; Melfos, V.; Baker, T.; Spry, P. Diverse Styles of Oligocene-Miocene Magmatic-Hydrothermal Deposits in Northeastern Greece: Relationships Between Tectonic-, Magmatic Activity, Alteration and Au-Ag Mineralization. In Eocene to Miocene Hydrothermal Deposits of Northern Greece and Bulgaria: Relationships Between Tectonic-Magmatic Activity, Alteration, and Gold Mineralization; Guidebook Series of the Society of Economic Geologists; Society of Economic Geologists: Littleton, CO, USA, 2016; Volume 54, pp. 83–112. [Google Scholar]
  27. 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]
  28. Papanikolaou, D.; Panagopoulos, A. On the structural style of southern Rhodope. Geol. Balc. 1981, 11, 13–22. [Google Scholar]
  29. Zachos, S.; Dimadis, E. The geotectonic position of the Skaloti-Echinos granite and its relationship to the metamorphic formations of Greek Western and Central Rhodope. Geol. Balc. 1983, 13, 5. [Google Scholar]
  30. Bomovas, I.; Rondogianm-Tsiambou, T. Geological Map of Greece; Institute of Geology and Mineral Exploration: Athens, Greece, 1983. [Google Scholar]
  31. Vavelidis, M.; Elftheriadis, G.; Kassoli-Fournaraki, A. A petrological study of the crystalline complex in the island Thasos. Ann. Géologiques Pays Helléniques 1987, 33, 203–216. [Google Scholar]
  32. Kronberg, P. Petrografie und Tectonik im Rhodopen-Kristallin des Tsal-Dag, Simvolon und Ost-Pangaon (Griechisch-Makedonien). Neues Jahrb. Geol. Pal. Abh. 1969, 7, 140–156. [Google Scholar]
  33. Schenk, P.-F. Geologie des westlichen Pangaion in Griechisch-Ostmakedonien. In Beihefte zum Geologischen Jahrbuch; Heft 88; Amt für Bodenforschung: Hannover, Germany, 1970; pp. 81–132. [Google Scholar]
  34. Meyer, W.; Pilger, A. Zur Geologie des Gebietes zwischen Strimon und Nestos (Rhodopen-Massiv) in Griechisch Makedonien: Neues Jahrbuch fur Geologie und Palaontologie. Abhandlungen 1963, 118, 272–280. [Google Scholar]
  35. Kronberg, P.; Meyer, W.; Pilger, A. Geologie der Rila-Rhodope-Masse zwischen Strimon und Nestos (Nordgriechenland). In Beihefte zum Geologischen Jahrbuch; Heft 88; Amt für Bodenforschung: Hannover, Germany, 1970; pp. 133–180. [Google Scholar]
  36. Nimfopoulos, M.K.; Rex, D.; Pattrick, R.A.D. Age of hydrothermal manganese mineralization near Kato Nevrokopi, Drama, northern Greece. Applied earth science. Trans. Inst. Min. Metall. 1998, 97, B193–B195. [Google Scholar]
  37. Nimfopoulos, M.K.; Pattrick, R.A.D.; Michailidis, K.M.; Polya, D.A.; Esson, J. Geology, geochemistry and origin of the continental Karst-hosted supergene manganese deposits in the western Rhodope massif, Macedonia, Northern Greece. Explor. Min. Geol. 1997, 6, 171–184. [Google Scholar]
  38. Papapetros, P. Geological Map of Greece, Kato Nevrokopi Sheet; Institute of Geology and Mineral Exploration: Athens, Greece, 1977–1979. [Google Scholar]
  39. Warr, L.N. IMA–CNMNC Approved Mineral Symbols. MinMag 2021, 85, 291–320. [Google Scholar] [CrossRef]
  40. Stouraiti, C.; Lozios, S.; Soukis, K.; Mavrogonatos, C.; Tsikos, H.; Voudouris, P.; Wang, H.; Zamparas, C.; Kollias, K. Manganese Metallogenesis in the Hellenic Arc: Case Studies from a Triassic Rift-Related Volcaniclastic Succession of the Cycladic Blueschist Unit, Greece. Ore Geol. Rev. 2022, 142, 104694. [Google Scholar] [CrossRef]
  41. Feng, X.H.; Zhai, L.M.; Tan, W.F.; Liu, F.; He, J.Z. Adsorption and redox reactions of heavy metals on synthesized Mn oxides minerals. Environ. Pollut. 2007, 147, 366–373. [Google Scholar] [CrossRef]
  42. Ostwald, J. A Low-zinc Chalcophanite from Norseman, Western Australia. Mineral. Mag. 1984, 48, 356–358. [Google Scholar] [CrossRef]
  43. Ostwald, J. Some observations on the chemical composition of chalcophanite. Mineral. Mag. 1985, 49, 752–755. [Google Scholar] [CrossRef]
  44. Du, S.; Wen, H.; Liu, S.; Qin, C.; Yan, Y.; Yang, G.; Feng, P. Mineralogy and Metallogenesis of the Sanbao Mn–Ag (Zn-Pb) Deposit in the Laojunshan Ore District, SE Yunnan Province, China. Minerals 2020, 10, 650. [Google Scholar] [CrossRef]
  45. Larson, L.T. Zinc-Bearing Todorokite from Philipsburg, Montana. Am. Mineral. 1962, 47, 59–66. [Google Scholar]
  46. Norman, D.I.; Bazrafshan, K.; Eggleston, T. Mineralization of the Luis Lopez epithermal manganese deposits in light of fluid inclusion and geologic studies. In Socorro Region II; New Mexico Geological Society 34th Field Conference Guidebook; New Mexico Geological Society Publications: Socorro, NM, USA, 1983. [Google Scholar]
  47. Maynard, J.B. Manganiferous Sediments, Rocks, and Ores. In Treatise on Geochemistry; Holland, H.D., Turekian, K.K., Eds.; Pergamon: Oxford, UK, 2003; pp. 289–308. [Google Scholar] [CrossRef]
  48. Cook, N.J.; Ciobanu, C.L.; Spry, P.G.; Voudouris, P.; The Participants of the IGCP-486. Understanding gold-(silver)-telluride-(selenide) mineral deposits. Episodes 2009, 32, 249–263. [Google Scholar] [CrossRef]
  49. Hedenquist, J.W.; Arribas, R.A.; Gonzalez-Urien, E. Exploration for Epithermal Gold Deposits. Gold 2000. [Google Scholar] [CrossRef]
  50. Siron, C.R.; Thompson, J.F.H.; Baker, T.; Friedman, R.; Tsitsanis, P.; Russell, S.; Randall, S.; Mortensen, J. Magmatic and Metallogenic Framework of Au-Cu Porphyry and Polymetallic Carbonate-Hosted Replacement Deposits of the Kassandra Mining District, Northern Greece. Soc. Econ. Geol. Spec. Publ. 2016, 19, 29–55. [Google Scholar]
  51. Siron, C.R.; Rhys, D.; Thompson, J.F.H.; Baker, T.; Veligrakis, T.; Camacho, A.; Dalampiras, L. Structural Controls on Porphyry Au-Cu and Au-Rich Polymetallic Carbonate-Hosted Replacement Deposits of the Kassandra Mining District, Northern Greece. Econ. Geol. 2018, 113, 309–345. [Google Scholar] [CrossRef]
  52. Xu, R.; Li, W.-C.; Deng, M.-G.; Zhou, J.-X.; Ren, T.; Yu, H.-J. Genesis of the Superlarge Luziyuan Zn-Pb-Fe(-Cu) Distal Skarn Deposit in Western Yunnan (SW China): Insights from Ore Geology and C-H-O-S Isotopes. Ore Geol. Rev. 2019, 107, 944–959. [Google Scholar] [CrossRef]
  53. Roy, S. Mineralogy of the Different Genetic Types of Manganese Deposits. Econ. Geol. 1968, 63, 760–786. [Google Scholar] [CrossRef]
  54. Wang, L.; Qin, K.-Z.; Song, G.-X.; Li, G.-M. A Review of Intermediate Sulfidation Epithermal Deposits and Subclassification. Ore Geol. Rev. 2019, 107, 434–456. [Google Scholar] [CrossRef]
  55. Sabeva, R.; Mladenova, V.; Mogessie, A. Ore Petrology, Hydrothermal Alteration, Fluid Inclusions, and Sulfur Stable Isotopes of the Milin Kamak Intermediate Sulfidation Epithermal Au-Ag Deposit in Western Srednogorie, Bulgaria. Ore Geol. Rev. 2017, 88, 400–415. [Google Scholar] [CrossRef]
  56. Rybárik, M.; Števko, M.; Koděra, P.; Prcúch, J. New Type of Epithermal Manganese Mineralization from the Banská Hodruša Precious and Base Metal Deposit at the Rozália Mine, Hodruša-Hámre, Slovakia. J. Geosci. 2023, 213–228. [Google Scholar] [CrossRef]
  57. Hariya, Y. Mineralogical studies on todorokite and birnessite from the Todoroki mine, Hokkaido, Japan. J. Jpn. Assoc. Mineral. Petrol. Econ. Geol. 1961, 45, 219–230, (In Japanese with English Abstract). [Google Scholar] [CrossRef]
  58. Hewett, D.F.; Fleischer, M. Deposits of the manganese oxides. Econ. Geol. 1960, 55, 1–55. [Google Scholar] [CrossRef]
  59. Rasor, C.A. Manganese mineralization at Tombstone, Arizona. Econ. Geol. 1939, 34, 790–803. [Google Scholar] [CrossRef]
  60. Prinz, W. Geology and Ore Deposits of the Philipsburg District Granite County, Montana; Geological Survey Bulletin; U.S. Government Publishing Office: Washington, DC, USA, 1967; p. 1237.
  61. Oyman, T. Efemçukuru B-Rich Epithermal Gold Deposit (Izmir, Turkey). Ore Geol. Rev. 2003, 23, 35–53. [Google Scholar] [CrossRef]
  62. Hewett, D.F. Veins of hypogene manganese oxide minerals in the southwestern United States. Econ. Geol. 1964, 59, 1429–1472. [Google Scholar] [CrossRef]
  63. Kubač, A.; Chovan, M.; Koděra, P.; Kyle, J.R.; Žitňan, P.; Lexa, J.; Vojtko, R. Mineralogy of the Epithermal Precious and Base Metal Deposit Banská Hodruša at the Rozália Mine (Slovakia). Miner. Petrol. 2018, 112, 705–731. [Google Scholar] [CrossRef]
  64. Voudouris, P.; Repstock, A.; Spry, P.G.; Frenzel, M.; Mavrogonatos, C.; Keith, M.; Tarantola, A.; Melfos, V.; Tombros, S.; Zhai, D.; et al. Physicochemical Constraints on Indium-, Tin-, Germanium-, Gallium-, Gold-, and Tellurium-Bearing Mineralizations in the Pefka and St Philippos Polymetallic Vein- and Breccia-Type Deposits, Greece. Ore Geol. Rev. 2022, 140, 104348. [Google Scholar] [CrossRef]
  65. 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]
  66. Tombros, S..; St. Seymour, K.; Spry, P.; Williams-Jones, A. Greenockite and zincian greenockite in epithermal polymetallic AgAuTe mineralization, Tinos Island, Hellas: Description and conditions of formation. Neues Jahrb. Mineral.—Abh. Band 2005, 182, 1–9. [Google Scholar] [CrossRef]
  67. Baumgärtl, U.; Burow, J. Laurion. Aufschluss 2002, 53, 245–362. [Google Scholar]
  68. Ottens, B.; Voudouris, P. Griechenland: Mineralien-Fundorte-Lagerstätten; Christian Weise Verlag: Munchen, Germany, 2018; 480p, ISBN 978-3-921656-86-0. [Google Scholar]
  69. Tămaș, C.G.; Andrii, M.P.; Kovács, R.; Drăgușanu, S.; Cauuet, B. Sphalerite Composition in Low- and Intermediate-Sulfidation Epithermal Ore Bodies from the Roșia Montană Au-Ag Ore Deposit, Apuseni Mountains, Romania. Minerals 2021, 11, 634. [Google Scholar] [CrossRef]
  70. Olivo, G.R.; Gibbs, K. Paragenesis and Mineral Chemistry of Alabandite (MnS) from the Ag-Rich Santo Toribio Epithermal Deposit, Northern Peru. Mineral. Mag. 2003, 67, 95–102. [Google Scholar] [CrossRef]
  71. Dobrev, S.; Vassileva, M.; Kolkovski, B. Hetaerolite from Madjarovo au-base-metal deposit, eastern Rhodopes. In Proceedings of the Annual Scientific Conference, Rye Brook, NY, USA, 22 October 2004. [Google Scholar]
  72. Udubasa, G.; Ottemann, J.; Agiorgitis, G. Hetaerolite from the Rodna Base Metal Ore Deposit: A New Occurrence. Am. Miner. 1973, 58, 1065–1068. [Google Scholar]
  73. Tanida, K.; Kitamura, T. Hydrohetaerolite from Maruyama mine, Hokkaido, Japan. J. Jpn. Assoc. Min. Petr. Econ. Geol. 1982, 72, 284–289. [Google Scholar] [CrossRef]
  74. Gasparrini, C. Gold and Other Precious Metals; Springer: Berlin/Heidelberg, Germany, 1993; pp. 149–185. [Google Scholar]
  75. Hewett, D.F.; Radtke, A.S. Silver-Bearing Black Calcite in Western Mining Districts. Econ. Geol. 1967, 62, 1–21. [Google Scholar] [CrossRef]
  76. Hewett, F.D. Silver in Veins of Hypogene Manganese Oxides; Geological Survey Circular; U.S. Geological Survey: Reston, VA, USA, 1968.
  77. Siems, P.L. Volcanic and Economic Geology of the Rosita Hills and Silver Cliff Districts, Custer County, Colorado. Ph.D. Thesis, Colorado School of Mines, Golden, CO, USA, 1967. [Google Scholar]
  78. Tiburcio Munive, G.; Encinas Romero, M.A.; Vazquez, V.M.; Valenzuela García, J.L.; Valenzuela Soto, A.; Coronado Lopez, J.H. Dissolution of Gold and Silver with Ammonium Thiosulfate from Mangano-Argentiferous Ores Treated in Acid-Reductive Conditions. JOM 2017, 69, 1901–1908. [Google Scholar] [CrossRef]
Minerals 14 00955 g004
Figure 4. Field photos demonstrating various mineralization styles at the Mavro Xylo mine. (a–c) Manganese mineralized marbles are cross-cut by both low-angle and high-angle faults; (d) vein mineralization with wurtzite and Ag-bearing Mn oxides; (e,f) brecciated marble cemented by coarse-grained black calcite containing silver-rich manganese oxides.
Figure 4. Field photos demonstrating various mineralization styles at the Mavro Xylo mine. (a–c) Manganese mineralized marbles are cross-cut by both low-angle and high-angle faults; (d) vein mineralization with wurtzite and Ag-bearing Mn oxides; (e,f) brecciated marble cemented by coarse-grained black calcite containing silver-rich manganese oxides.
Minerals 14 00955 g004
Minerals 14 00955 g005
Figure 5. Hand specimens demonstrating vein-type assemblage of the Mavro Xylo area: (a) rhodonite (Rdn)–quartz (Qz)–rhodochrosite (Rds) followed by later quartz (Qz) and todorokite; (b) early wurtzite (Wur) followed by todorokite (Tdr)–hetaerolite (Hta)–chalcophanite (Cph), grey in color with quartz and calcite as gangue minerals; (c) hetaerolite (hta) and silver-rich manganese oxides. Abbreviations were obtained from Warr (2021) [39].
Figure 5. Hand specimens demonstrating vein-type assemblage of the Mavro Xylo area: (a) rhodonite (Rdn)–quartz (Qz)–rhodochrosite (Rds) followed by later quartz (Qz) and todorokite; (b) early wurtzite (Wur) followed by todorokite (Tdr)–hetaerolite (Hta)–chalcophanite (Cph), grey in color with quartz and calcite as gangue minerals; (c) hetaerolite (hta) and silver-rich manganese oxides. Abbreviations were obtained from Warr (2021) [39].
Minerals 14 00955 g005
Minerals 14 00955 g006
Figure 6. Microphotographs (BSE images) of sulfides, Mn oxides, and non-metallic minerals from the (a,b,d,h,i) rhodonite–quartz–rhodochrosite–sulfide-rich samples and (c,e–g) the silver-rich Mn oxide samples from Mavro Xylo. (a) Pyrite (Py) grains in association with rhodonite (Rdn) surrounded by quartz (Qz); (b) Te-bearing argentite (Arg) and galena (Gn) as inclusions in pyrite; (c) galena (Gn) is present as an inclusion in hetaerolite (Hta) and surrounded by calcite (cal); (d) sphalerite (Sp) occurs together with hydrothermal muscovite (Ms) and quartz (Qz) and rimming rhodonite; (e) early alabandite (Abd) followed by todorokite (Tdr), which is replaced by hetaerolite/hydrohetaerolite (Hta) and late chalcophanite (Cph). Hydrothermal muscovite (Ms) formed contemporaneously with manganese oxides; (f) monazite in association with hydrothermal muscovite (Ms) included in todorokite (Tdr) and in contact with the hydrous Pb-Mn oxide mineral replacing todorokite; (g) argentian chalcophanite (Ag cph) and silver-rich hydrous lead manganese oxide (Pb-Mn ox.) postdate hydrohetaerolite (Hta); (h) rhodonite (Rdn) followed by quartz (Qz) in association with rhodochrosite (Rds); (i) pyrophanite (Pph) as an inclusion in quartz (Qz).
Figure 6. Microphotographs (BSE images) of sulfides, Mn oxides, and non-metallic minerals from the (a,b,d,h,i) rhodonite–quartz–rhodochrosite–sulfide-rich samples and (c,e–g) the silver-rich Mn oxide samples from Mavro Xylo. (a) Pyrite (Py) grains in association with rhodonite (Rdn) surrounded by quartz (Qz); (b) Te-bearing argentite (Arg) and galena (Gn) as inclusions in pyrite; (c) galena (Gn) is present as an inclusion in hetaerolite (Hta) and surrounded by calcite (cal); (d) sphalerite (Sp) occurs together with hydrothermal muscovite (Ms) and quartz (Qz) and rimming rhodonite; (e) early alabandite (Abd) followed by todorokite (Tdr), which is replaced by hetaerolite/hydrohetaerolite (Hta) and late chalcophanite (Cph). Hydrothermal muscovite (Ms) formed contemporaneously with manganese oxides; (f) monazite in association with hydrothermal muscovite (Ms) included in todorokite (Tdr) and in contact with the hydrous Pb-Mn oxide mineral replacing todorokite; (g) argentian chalcophanite (Ag cph) and silver-rich hydrous lead manganese oxide (Pb-Mn ox.) postdate hydrohetaerolite (Hta); (h) rhodonite (Rdn) followed by quartz (Qz) in association with rhodochrosite (Rds); (i) pyrophanite (Pph) as an inclusion in quartz (Qz).
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Minerals 14 00955 g007
Figure 7. The paragenetic sequence of Ag-rich Mn-Zn-Pb vein-type mineralization at Mavro Xylo.
Figure 7. The paragenetic sequence of Ag-rich Mn-Zn-Pb vein-type mineralization at Mavro Xylo.
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Minerals 14 00955 g008
Figure 8. Correlation plots of (a) Ag vs. Zn, (b) Mn vs. Ag, and (c) Mn vs. Zn in Todorokite, and (d) Ag vs. Zn in chalcophanite from Mavro Xylo Ag-Pb-Zn-Mn mineralization.
Figure 8. Correlation plots of (a) Ag vs. Zn, (b) Mn vs. Ag, and (c) Mn vs. Zn in Todorokite, and (d) Ag vs. Zn in chalcophanite from Mavro Xylo Ag-Pb-Zn-Mn mineralization.
Minerals 14 00955 g008
Table 1. Representative EPMA data of sulfides from Mavro Xylo Mn mineralization (in wt.%, b.d. = below detection): 1–3 Pyrite; 4–5 sphalerite; 6 alabandite.
Table 1. Representative EPMA data of sulfides from Mavro Xylo Mn mineralization (in wt.%, b.d. = below detection): 1–3 Pyrite; 4–5 sphalerite; 6 alabandite.
123456
Fe46.8445.3746.580.570.20.22
S52.7651.4653.3732.8533.0135.15
Mn0.820.030.032.32.5664.9
Cu0.060.050.020.050.040.02
As0.011.07b.d.b.d.b.d.b.d.
Pb0.180.190.250.10.060.11
Znb.d.0.010.0264.7164.780.08
Agb.d.0.360.020.020.090.03
Total99.698.54100.29100.6100.74100.49
Chemical Formula
Fe1.0061.0001.0000.0100.0030.003
S1.9741.9761.9970.9920.9940.961
Mn0.0180.0010.0010.0400.0451.034
Cu0.0010.0010.0000.0010.0010.000
As0.0000.017b.d.b.d.b.d.b.d.
Pb0.0010.0010.0010.0000.0000.001
Znb.d.0.0000.0000.9570.9560.001
Agb.d.0.0040.0000.0000.0010.000
Total3.0003.0003.0002.0002.0002.000
Table 2. Representative EPMA data of Mn-oxides/hydroxides from Mavro Xylo Mn mineralization (in wt.%, b.d. = below detection): 1–2 hetaerolite; 3–4 hydrohetaerolite; 5–6 todorokite; 7–8 hydrous lead manganese oxide; 9–11 chalcophanite.
Table 2. Representative EPMA data of Mn-oxides/hydroxides from Mavro Xylo Mn mineralization (in wt.%, b.d. = below detection): 1–2 hetaerolite; 3–4 hydrohetaerolite; 5–6 todorokite; 7–8 hydrous lead manganese oxide; 9–11 chalcophanite.
Oxide 1234567891011
SiO20.110.120.160.180.060.030.10.080.110.090.06
Al2O30.02b.d.b.d.0.02b.d.b.d.0.080.10.150.070.03
FeO0.230.180.120.130.160.20.840.450.430.80.29
Mn3O466.266.0662.1662.26-------
MnO2----87.0185.5568.8271.9369.2876.8379.52
MgOb.d.b.d.b.d.b.d.0.060.020.020.290.350.340.5
CaO0.04b.d.0.130.090.930.830.951.461.091.793.01
K2O0.02b.d.0.030.040.180.180.20.410.220.640.78
Cu2O0.050.020.110.120.030.030.520.560.090.530.09
As2O3b.d.b.d.b.d.b.d.b.d.b.d.0.870.580.310.240.17
PbO0.03b.d.0.020.070.030.0617.199.820.050.311.5
ZnO33.7833.635.235.122.482.994.865.1722.587.44.68
Ag2Ob.d.b.d.b.d.b.d.0.671.560.731.460.461.812.2
Total100.2599.9897.9398.0391.6191.4595.1892.3195.0190.8593.74
Table 3. Representative EPMA data of Mn-carbonates and Mn-silicates from Mavro Xylo Mn mineralization (in wt.%, b.d. = below detection): 1 Mn-bearing Calcite; 2–3 rhodochrosite; 4–5 rhodonite.
Table 3. Representative EPMA data of Mn-carbonates and Mn-silicates from Mavro Xylo Mn mineralization (in wt.%, b.d. = below detection): 1 Mn-bearing Calcite; 2–3 rhodochrosite; 4–5 rhodonite.
Oxide12345
SiO2b.d.0.390.1744.7744.62
Al2O3b.d.0.030.030.891.04
FeOb.d.0.160.120.410.36
MnO1.959.6347.3646.1644.61
MgO0.330.210.680.580.4
CaO54.521.311.725.417.11
K2Ob.d.0.010.020.02b.d.
Cu2O0.030.030.020.010.02
As2O3b.d.b.d.0.010.03b.d.
PbO0.02b.d.b.d.0.040.06
ZnO0.060.090.010.020.01
Ag2O0.02b.d.b.d.0.01b.d.
CO2 *42.9336.9038.01--
Total99.4898.7598.1597.9598.23
* CO2 is estimated by stoichiometry.
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Soulamidis, G.; Stouraiti, C.; Voudouris, P.; Tsikos, H. New Ag-Rich Mn-Zn±Pb Vein Mineralization at the Mavro Xylo Manganese Oxide Deposit, Drama, Greece. Minerals 2024, 14, 955. https://doi.org/10.3390/min14090955

AMA Style

Soulamidis G, Stouraiti C, Voudouris P, Tsikos H. New Ag-Rich Mn-Zn±Pb Vein Mineralization at the Mavro Xylo Manganese Oxide Deposit, Drama, Greece. Minerals. 2024; 14(9):955. https://doi.org/10.3390/min14090955

Chicago/Turabian Style

Soulamidis, George, Christina Stouraiti, Panagiotis Voudouris, and Harilaos Tsikos. 2024. "New Ag-Rich Mn-Zn±Pb Vein Mineralization at the Mavro Xylo Manganese Oxide Deposit, Drama, Greece" Minerals 14, no. 9: 955. https://doi.org/10.3390/min14090955

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