Next Article in Journal
Late Carboniferous Slab Rollback in the Southern Altaids: Evidence from a Slab-Derived Adakitic Granodiorite in the South Tianshan
Previous Article in Journal
Enrichment Regularity of Indium in the Dulong Mineral Processing Plant, Yunnan Province, China
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Minerals
Volume 15
Issue 7
10.3390/min15070673
minerals-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Volcanic Rocks from Western Limnos Island, Greece: Petrography, Magnetite Geochemistry, and Magnetic Susceptibility Constraints

by
Christos L. Stergiou
*,
Vasilios Melfos
,
Lambrini Papadopoulou
,
Anastasios Dimitrios Ladas
and
Elina Aidona
School of Geology, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
*
Author to whom correspondence should be addressed.
Minerals 2025, 15(7), 673; https://doi.org/10.3390/min15070673
Submission received: 16 May 2025 / Revised: 12 June 2025 / Accepted: 20 June 2025 / Published: 23 June 2025
(This article belongs to the Special Issue Decoding Magmatic-Hydrothermal Parageneses: Insights into Mineralogy and Formation Conditions)
Browse Figures
Versions Notes

Abstract

This study contributes new mineralogical, whole-rock geochemical, and magnetic susceptibility data to the well-established petrogenesis of the Miocene of Limnos volcanic rocks in the Aegean region. The combined examination of volcanic samples from the Katalakon, Romanou, and Myrina units demonstrates that they belong to a genetically related high-K calc-alkaline to shoshonitic suite that was formed by fractional crystallization in a continental arc setting and derived from a subduction-modified mantle source, contaminated by continental sediments. Different magmatic processes and crystallization conditions are reflected in modest compositional differences in magnetite (Ti, Al substitution) and ilmenite (Mg, Al, Fe–Ti ratios), as well as variations in trace elements between the units (e.g., elevated Nb–Zr in Romanou, high LREE in Myrina, and Ba in Katalakon). According to the magnetic data, bulk magnetic susceptibility is largely determined by magnetite abundance, whereas magnetic domain states are influenced by the grain size and shape, as euhedral grains are associated with stronger responses. The coupled geochemical and magnetic results indicate the diversified and transitional character of the Agios Ioannis Subunit in the Katalakon Unit.

1. Introduction

Magmas in subduction zones are compositionally diverse, due to mantle–crust mixing, hydrous melting, and fluid transport in the mantle wedge [1,2,3]. These magmas, typically basaltic, form through hydrous melting, sometimes aided by decompression, and evolve during ascent via crustal interaction [4,5]. Subduction arcs commonly produce medium- to high-K calc-alkaline and shoshonitic magmas [6]. In oceanic arcs, K-rich types reflect sediment-influenced mantle melting, while continental arcs may involve melting of sediment diapirs or peridotite [6,7]. Some high-Mg andesites originate from hydrous peridotite or sediment-enriched melts [8]. After subduction ends, K-rich magmatism can be triggered by the melting of the metasomatized lithospheric mantle or crust, driven by volatiles or thermal input from asthenospheric upwelling [9].
The evolution of the Aegean–Anatolian region incorporates a complex history of subduction, slab segmentation, and crustal deformation within the broader Alpine–Eastern Mediterranean orogenic system [10,11,12,13]. Prolonged convergence and collision between the African and Eurasian plates since the Mesozoic has resulted in a complex tectonic assembly of the Apulia, Pelagonia, and Rhodope continental blocks, as well as intervening oceanic crust [14,15,16]. Subduction of the oceanic lithosphere along a north-dipping slab generated high-pressure metamorphism and crustal thickening, followed during the Eocene by a southward slab retreat and slab rollback [14,15,16].
Since the Eocene, the area has experienced large-scale extensional tectonics, trench rollback, significant crustal thinning, and the exhumation of metamorphic core complexes [12,13,14,15,16,17]. This process, beginning with an initial back-arc extension in the Rhodopes, intensified after ~25 Ma and especially after ~15 Ma, due to the southward retreat of the Hellenic slab and the onset of subduction of the Neotethyan oceanic lithosphere, south of Crete [12,18]. Magmatism and volcanism related to these processes has persisted since the Late Mesozoic [19]. Especially within the Rhodope block and at the Biga peninsula, northwestern Turkey, calc-alkaline to shoshonitic magmatism occurred between the Eocene and Miocene in response to slab dynamics and crust–mantle interactions (e.g., [19,20,21,22,23,24,25]). Regional extension, driven by slab rollback and mantle upwelling, has produced some high crustal dilation rates, profoundly reshaping the Aegean lithosphere [14,19]. This magmatic–volcanic activity also resulted in the formation of numerous instances of mineralization (e.g., porphyry, epithermal, skarn) of base, precious, and rare metals (e.g., Pb, Zn, Cu, Au, Te, Co, Bi) (e.g., [26,27,28,29,30]).
The Oligocene to Miocene high-K calc-alkaline to shoshonitic volcanism on Limnos, Lesbos, and Samothraki islands was the result of this tectonomagmatic framework [21,24,31]. Paleomagnetic and tectonic studies indicate that volcanism coincided with clockwise rotation and large-scale NE–SW extension, further facilitated by the activation of strike–slip systems, such as the North Anatolian Fault Zone [15,32,33,34,35,36,37]. In particular, Limnos Island occupies a key position within this extensional back-arc setting and records a distinct, narrow in time, and voluminous magmatic episode during the Early Miocene (Figure 1a). This volcanic phase, dominated by high-K to shoshonitic compositions, is interpreted as the product of asthenospheric mantle upwelling, due to slab detachment beneath the region [19,20,21]. The compositional characteristics of Limnos volcanics, including enriched rare earth elements (REEs), high Mg–Cr clinopyroxenes, and evolved isotopic signatures, indicate mixing between mantle-derived melts, and crustal components occurred, likely facilitated by the melting of underplated amphibolites [19,20]. The volcanic record of the island offers a unique opportunity to explore the mantle and crust interactions, back-arc tectonics, and post-emplacement evolution within the context of slab rollback and orogenic collapse in the northern Aegean [14,19,20,21,38].
In this article, we contribute to the existing, well-established knowledge on the petrogenesis of Limnos volcanic rocks with new data on mineralogy and whole-rock geochemistry. We integrate mineralogical characterization with whole-rock and magnetite geochemistry, alongside targeted magnetic susceptibility measurements, deciphering the petrogenesis and post-emplacement history of Limnos volcanic rocks. Whole-rock major and trace element systematics constrain the magma source characteristics, melting processes, and crustal assimilation, while magnetite geochemistry, particularly variations in Ti, V, and Al content, yields quantitative estimates of the magma differentiation pathways. Complementing these, measurements on low-frequency susceptibility (χLF), high-frequency susceptibility (χHF), and frequency-dependent susceptibility (χfd %) enable us to characterize the magnetic mineralogy and grain size distributions, distinguish the presence of superparamagnetic grains, and assess the degree of alteration or weathering within and between volcanic units on Limnos.

2. Geological Setting

Limnos Island, located in the northern Aegean Sea, southwest of Samothraki Island, is a tectonically active location within the Thrace Basin (Figure 1a,b). It covers an area of around 400 km2, which was shaped by intricate interactions between sedimentation, magmatism, and tectonism related to the evolution of the Aegean subduction zone. Limnos has a geological contrast in terms of its morphology: the western part is mountainous and volcanic, while the eastern part is low lying and characterized by sedimentary deposits. This contrast is controlled by the Kondias–Kotsinas fault zone, an NE–SW-striking right-lateral strike–slip fault system that not only divides the island morphologically, but may also have influenced the emplacement of volcanic and subvolcanic intrusions (Figure 1a) [32,36,39].
The oldest rocks in Limnos comprise a Paleogene sedimentary basement that formed during the post-orogenic collapse of the Rhodope–Sakarya orogen [40]. This collapse resulted in the formation of an NE–SW-trending extensional basin, including thick turbidite layers, dating from the Middle Eocene to the Early Oligocene and corresponding to the Fissini-Sardes Unit (Figure 1a). Sandstones interbedded with siltstones, and intercalated tuffs and limestone olistoliths make up this unit, while their formation is ascribed to submarine fan and continental slope sediments [41]. The Fissini-Sardes Unit is divided into a lower and an upper unit. The lower unit, more widely distributed, comprises siliciclastic deposits formed in a deeper setting, while the upper unit records a transition to shallower marine and, eventually, continental fluviodeltaic conditions, with interbedded siltstones, sandstones, and sandy limestones, overlain by fluvial sediments [40]. According to Marchev et al. [42], tuff layers that are intercalated in Late Eocene to Early Oligocene (Priabonian–Rupelian) sandstones, exposed in the southeast part of the island, are linked to two major supereruptions from the Oligocene Borovitsa volcanic complex in Bulgaria. The uppermost layer is dated to 32.8 Ma (U–Pb date), and the underlying layer to 33.38 Ma (U–Pb dates, after [42]).
The Fissini-Sardes Unit transitions to the Late Oligocene–Early Miocene Ifestia Unit, which includes thick-bedded and coarse-grained sandstones, incorporating conglomerates as lenses and layers (Figure 1a) [43]. The Early Miocene Therma Unit overlies the Ifestia Unit and indicates a transition to a continental environment during rapid uplift [43].
The volcanic activity on Limnos is represented by three major volcanic units: Katalakon, Romanou, and Myrina (Figure 1a) [44]. These Lower Miocene (Aquitanian–Burdigalian) volcanic rocks, which range in age from 21 to 18 Ma, are found, unconformably, overlying the sedimentary basement [20]. They vary in composition from andesite and dacite to trachyte and latite, with calc-alkaline to shoshonitic affinities [45,46].
The Katalakon Unit, the earliest volcanic unit, consists of NW-trending, K-rich andesitic to dacitic lavas. These lavas are locally interbedded or cut by hydrothermal breccias, E–W-trending dikes, and monomineralic quartz-cemented veins, indicating intense hydrothermal activity [20,44]. Radiometric dating revealed the whole-rock and groundmass K–Ar ages of 21.3 ± 0.7 to 20.2 ± 0.2 Ma, indicating an Early Miocene, Aquitanian age [44]. The Katalakon Unit covers the southern half of the island and creates the foundational volcanic landscape, particularly in the Gulf of Moudros (Figure 1a). At the northwestern part of the island, the Agios Ioannis Subunit is mentioned by Pe-Piper et al. [20]. This subunit is characterized as transitional from the Katalakon Unit to the Myrina Unit and mainly contains lava flows (Figure 1a).
The Romanou Unit, which overlies the Katalakon Unit, consists of K-rich dacites and latites [19]. It is characterized by thick pyroclastic sequences, containing lithic and pumice-rich flows (<160 m in thickness). These deposits are interlayered with airfall tuffs, shoshonitic lava flows, volcanic breccias, and sedimentary intercalations [20,45]. The whole-rock K–Ar dating of ignimbrites and andesites from the Romanou lavas suggests ages of roughly 20.5 ± 0.9 to 20.2 ± 0.8 Ma (Early Miocene, Aquitanian–Burdigalian), implying a relatively quick sequence of volcanic phases following the formation of the Katalakon Unit [20,44,45].
The Myrina Unit is the youngest group of volcanic rocks and is located in the southwest of Limnos (Figure 1a). It is dominated by K-rich dacitic lavas, with minor andesitic and trachytic compositions, and contains hydrothermal breccias, lava flows, and lahars that are lithologically comparable to the Katalakon Unit. The NW–SE-striking Kaspakas fault separates the Myrina Unit from the northern Katalakon Unit. Dacites and andesites from the Myrina Unit have groundmass, sanidine, and biotite K–Ar ages ranging from 19.3 ± 0.3 to 17.9 ± 0.4 Ma (Early Miocene, Burdigalian), indicating that they were formed during the late stages of the Miocene volcanic activity [20,44,45].
The Fakos intrusion (Cape Fakos, southern Limnos) is a geologically significant feature of the island, representing a deeper crustal expression of the same magmatism responsible for the overlying volcanic rocks of the Katalakon Unit (Figure 1a). The Fakos intrusion hosts a porphyry copper and epithermal gold–tellurium system, emplaced within the sedimentary sequence of the Fissini-Sardes Unit and the volcanic Katalakon Unit, under the structural control of the Kondias–Kotsinas fault system (Figure 1a) [47]. The mineralization is hosted in a ~20 Ma quartz monzonite, associated with shoshonitic affinities. Three distinct mineralization stages are recognized [47]: Stage 1, features porphyry-style quartz and quartz–calcite veins with pyrite, chalcopyrite, galena, bornite, molybdenite, and sphalerite, accompanied by potassic and propylitic alteration; Stage 2, is dominated by quartz–tourmaline veins and sericitic alteration, with disseminated pyrite and molybdenite; and Stage 3, which is epithermal in style, and includes polymetallic veins with enargite, bournonite, tetrahedrite–tennantite, native gold, and tellurides. Fluid inclusion and sulfur isotope data indicate a magmatic–hydrothermal origin, with evidence of boiling, volatile fractionation, and meteoric water mixing. The system is transitional between porphyry and high-to-intermediate sulfidation epithermal mineralization [47].
Younger sedimentary units of the Pliocene to Quaternary age unconformably overlie both the volcanic and older sedimentary rocks (Figure 1a). These deposits include conglomerates and sandstones, and younger calcarenites, sands, alluvial and colluvial deposits.
Tectonic compression from the Late Oligocene to the Middle Miocene folded the sedimentary successions and caused the formation of tensional structures. This deformation is linked to the collision of the Apulian block with the Eurasian Plate, which affected the subduction dynamics at the Aegean domain and caused regional uplift and erosion [36,48]. Subduction-related high-pressure metamorphism recorded in the Cycladic Basal Unit between 24 and 21 Ma also marks this tectonic phase [49]. Following this tectonic rearrangement, significant volcanism on Limnos took place in the Early Miocene, concurrent with the subduction of the oceanic lithosphere beneath the Aegean region [14,49].
Throughout Limnos Island, folding within the sedimentary units, particularly the Eocene–Oligocene turbidites of the Fissini-Sardes Unit, is expressed as gentle to open folds, with axes trending E–W and WSW–ENE. This deformation did not affect the overlying Miocene volcanic rocks, indicating that folding predates volcanism [36]. To the contrary, the faults are pervasive and display mainly NE–SW, ENE–WSW, and E–W-trending orientations, and secondarily NNE–SSW and NW–SE to NNW–SSE trends [32,36,39]. These fault systems affect both the sedimentary and igneous rocks and are responsible for local structural complexity. The Mourtzouflos, Kondias–Kotsinas, Kaspakas, and Fakos–Agia Sofia faults are notable (Figure 1a).

3. Materials and Methods

The sampling locations are allocated in the central and mostly in the western part of Limnos Island (Table 1, Figure 2a). Geological sampling was carried out along the outcrops of volcanic rocks belonging to the Myrina, Katalakon, and Romanou units, by focusing on examining the wall rock mineralogy, while avoiding areas altered by supergene processes. From each locality, 5 kg of representative rock material was collected to ensure a comprehensive sample for further analysis. A total of fifteen samples were collected, including seven trachydacite samples (LIM 01, LIM 02, LIM 03, LIM 04, LIM 10), three dacite samples (LIM 09, LIM 11, LIM 12), and two trachyandesite samples (LIM 05, LIM 13) from the Myrina Unit, one trachyandesite sample (LIM 07) from the Romanou Unit, and one andesite sample (LIM 08), two trachydacite samples (LIM 14, LIM 15), and one trachyandesite sample (LIM 16; Agios Ioannis Subunit) from the Katalakon Unit (Table 1, Figure 2a).
Fifteen thin-polished sections were produced and studied under a ZEISS Axioskop 40 dual reflected-transmitted light polarizing microscope (Zeiss, Oberkochen, Germany), coupled with a Canon Powershot A640 camera (Canon, Tokyo, Japan), at the School of Geology, Aristotle University of Thessaloniki (AUTH). Photomicrographs were obtained and analyzed using ImageJ software (version 1.54p) [50] in order to extract the morphometric and textural aspects, including the grain size, angularity, and modal percentages of magnetite.
Each collected sample was also analyzed by means of X-ray fluorescence spectrometry (XRF) and multi-element inductively coupled plasma mass spectrometry (ICP-MS) to determine the major and trace elements, at MSALABS, Langley, Canada. Pulp preparation included lithium borate fusion for the major oxides, refractory elements, and REEs by means of XRF analysis. The trace element analysis by means of ICP-MS for As, Au, Bi, Hg, Sb, Se, and Tl included Aqua Regia digestion (i.e., a true 3:1 mixture of hydrochloric and nitric acids and dilute mixtures (equal portion) of hydrochloric acid, nitric acid, and deionized water), while Ag, Cd, Cu, Mo, Ni, Pb, and Zn were digested in a 4-acid solution (hydrochloric, nitric, perchloric, and hydrofluoric acids). The geochemical results were compared and discussed in regard to previously published geochemical data from Limnos, Lesvos, and Samothraki [21,24,31,51]. Geochemical classification graphs were produced using PetroGram [52], while graph digitization was performed using Grapher software (version 16.1.335, Golden Software LLC, Golden, CO, USA). The LOI values range from 0.01 to 4.61 wt.% across the dataset, indicating limited to moderate volatile content, consistent with low degrees of alteration (advice Table 2). Major element oxides were recalculated by using PetroGram (a Microsoft Excel workbook as provided by [52] on a volatile-free basis to avoid dilution effects in the classification and petrogenetic diagrams. This ensures that geochemical interpretations reflect primary magmatic compositions. In Supplementary Table S1, the calculations (e.g., water-free XRF analysis) and conversions made using PetroGram are presented [52].
A total of 4 sections (LIM 01, Myrina Unit; LIM 07, Romanou Unit; LIM 08, LIM 15, Katalakon Unit) were studied by means of scanning electron microscopy, using a JEOL JSM-6390LV SEM, equipped with an OXFORD INCA 300 EDS (Oxford Instruments Ltd., Abingdon, UK), at the Faculty of Sciences, Aristotle University of Thessaloniki. The operating conditions included: 20 kV accelerating voltage, 0.4 mA probe current, 80 s analysis time, and ~1 μm beam diameter, in back-scattering electron (BSE) mode. Internal empirical corrections were performed to compensate for peak overlap. The main focus of the SEM–EDS analysis was to investigate the mineral chemistry and texture of magnetite and ilmenite. A summary of the min, max, standard deviation, and mean values in terms of the conducted SEM–EDS analyses is given in Supplementary Table S2.
Magnetic susceptibility measurements were performed on 15 representative samples from the investigated sites. All the samples were sieved and placed in cylindrical plastic boxes (2 × 2 × 2 cm). Laboratory measurements of volume-specific magnetic susceptibility (κ, SI units) were performed using a Bartington MS2B sensor, at low (0.465 kHz) and high (4.65 kHz) frequency. The samples were weighed prior to measurement; therefore, all the results are reported as mass-specific magnetic susceptibility (χ, 10−8 m3/kg). During the measurement process, each sample was measured at least 3 times, and the average value was considered as the final value for the sample. For all the samples, two air measurements were taken before and after the measurement of the sample. In addition, the frequency-dependent susceptibility (χFD%) was calculated [χFD% = 100(χLF − χHF)/χLF] according to Dearing et al. [53].
The volume-specific magnetic susceptibility (κ), expressed in SI units (m3/kg or m3/m3), quantifies the ability of rock to become magnetized in regard to an applied magnetic field. This property primarily reflects the concentration and composition of ferromagnetic and paramagnetic minerals, particularly Fe–Ti oxides (e.g., magnetite, ilmenite) [54,55]. In petrological studies, magnetic susceptibility is widely used as a proxy for estimating the modal abundance of magnetic minerals and can assist in distinguishing between rock types with similar bulk compositions but different mineralogies or alteration processes [54,55]. It also helps identify magmatic differentiation trends, hydrothermal alteration zones, or variations related to oxidation states [54,55]. In this study, magnetic susceptibility measurements were used to complement the petrographic observations and trace element data, helping to constrain the relative abundance of magnetic phases and support inferences about the degree of fractionation and alteration.

4. Results

4.1. Petrography

Typical volcanic textures and mineralogy characterize the surveyed outcrops at Limnos Island and the selected and analyzed samples (Figure 2b–g and Figure 3a–i). The volcanic rocks of the Myrina Unit are composed of dacites, trachydacites, and trachyandesites (Table 1, Figure 2b–e). The trachydacites show porphyritic textures. A groundmass of fine-grained feldspar, quartz, and subordinate mafic minerals surrounds the phenocrysts of plagioclase and K-feldspar, mainly sanidine (Figure 3a). Quartz exhibits rounded grains and magmatic corrosion, while clusters of clinopyroxene crystals are also common (Figure 3a,h). The Myrina trachyandesites have a similar porphyritic texture, with plagioclase and hornblende phenocrysts (Figure 3b). Plagioclase, quartz, biotite, and hornblende are found in dacites, which are also porphyritic to glomeroporphyritic. The interstitial groundmass is silica rich and has granular to microlitic textures. Hydrothermal alteration products have not been detected.
The Romanou Unit is represented by trachyandesitic lavas, characterized by porphyritic to trachytic textures (Figure 2f). Phenocrysts of plagioclase and subordinate K-feldspar (mainly sanidine) are typically present, along with variable amounts of mafic phases, such as clinopyroxene and amphibole (Figure 3d). These minerals often show alignment that imparts a fluidal fabric (Figure 2f). Alkali feldspar microlites and interstitial glass or a cryptocrystalline matrix compose the majority of the microcrystalline groundmass (Figure 3c). Mafic minerals locally may be replaced by chlorite, calcite, and epidote, suggesting the overprint of weak propylitic alteration.
Volcanic rocks of the Katalakon Unit include andesites and trachydacites (Figure 2g and Figure 3e,f). The andesites exhibit porphyritic textures, with dominant plagioclase phenocrysts, which are accompanied by subordinate hornblende, affected by hydrothermal alteration (Figure 3e). The groundmass is typically pilotaxitic to intergranular. The Katalakon trachydacites are likewise porphyritic, with plagioclase phenocrysts, biotite, and hornblende being set in a fine-grained matrix, with quartz and feldspar microlites (Figure 3f). Locally, clusters of pyroxene crystals are found in the rock mass (Figure 2g).
Magnetite was the most abundant accessory mineral found in all the analyzed samples (Figure 3g–i). It shows typical ilmenite lamellae, and only local hematite oxidation (Figure 3g–i). Other trace minerals variably detected in the studied samples, in association with magnetite, were apatite, zircon, titanite, monazite, rutile, chalcopyrite, and barite.

4.2. Lithogeochemistry

The whole-rock geochemical analysis of representative volcanic samples from the Myrina, Katalakon, and Romanou units reveal distinct compositional variations. The SiO2 contents range from 56.95 to 64.82 wt.%, reflecting predominantly intermediate compositions, with some slightly more mafic samples (e.g., LIM 05, LIM 14) (Table 2). Al2O3 is consistently moderate (13.2–16.48 wt.%), while Fe2O3 varies more widely, from 3.37 wt.% to 7.01 wt.% (e.g., LIM 15), indicating variable iron enrichment, particularly in the Romanou Unit (Table 2). The MgO and CaO contents are slightly higher in the Romanou samples, consistent with a more mafic trend (Table 2). Na2O and K2O generally show moderate to high values (<5.26 wt.% K2O), suggesting a calc-alkaline affinity. TiO2 ranges from 0.5 to 1.0 wt.%, with higher values correlating with increased Fe2O3 and suggesting enrichment in Fe–Ti oxides, such as magnetite or ilmenite (Table 2). The loss on ignition (LOI) varies, with values above 4 wt.% in a few samples (e.g., LIM 01, LIM 08), possibly due to the minimal effect of hydrothermal alteration.
The trace element data indicate key geochemical variations that help distinguish the different samples. Notably, the Myrina samples show the highest enrichments in several trace elements (Table 3). They are enriched in Ba (<2590 ppm), Nb (<20 ppm), Zr (<364 ppm), Sr (<1415 ppm), and Rb (<235 ppm), as well as in light rare earth elements (LREEs), such as La (<97 ppm) and Ce (<182 ppm) (Table 3). The highest REE contents are related to sample LIM 09 (ΣREE = 403 ppm) (Table 3). Transition metals, such as Cr (<181 ppm, sample LIM 16) and Ni (<89 ppm, sample LIM 16), are relatively low overall, but show localized enrichments, while trace chalcophile and metalloid elements, like Sb (<0.92 ppm LIM 14), Bi (<0.18 ppm LIM 09), and Tl (<0.31 ppm LIM 12), display isolated high values. Additionally, sample LIM 07 from the Romanou Unit shows the highest enrichment in V (158 ppm) (Table 3).
The geochemical discrimination diagrams presented provide a comprehensive classification of the volcanic rocks from the Myrina, Katalakon, and Romanou units of Lemnos Island (Figure 4a–d). The TAS diagram reveals that all three units plot within the andesite, dacite, and trachyandesite fields, with some samples from the Myrina Unit approaching the trachyte/trachydacite boundary, indicating an intermediate to felsic composition (Figure 4a). In the K2O vs. SiO2 plot, most samples from all three units fall within the high-K calc-alkaline to shoshonitic fields, characteristic of subduction-related magmatism (Figure 4c). In the immobile element-based diagrams, the samples cluster mostly within the andesite to trachyandesite/trachyte fields (Figure 4b,d). It is notable that samples from the Romanou and Katalakon units show similar geochemical behavior, overlapping with the Myrina samples, with the differences primarily associated with variations in alkali enrichment (Figure 4a–d).
The geochemical classification and tectonic discrimination plots of the Limnos volcanic rocks are shown in Figure 5a–e. In the total alkali vs. SiO2 diagram, the samples from the Myrina, Romanou, and Katalakon units plot mainly in the calc-alkalic to alkali-calcic fields, indicating their overall alkaline to mildly subalkaline character (Figure 5a). The alkalinity index (AI) versus the feldspathoid silica-saturation index (FSSI) plot shows that all the samples are metaluminous and silica saturated, while the Cr vs. Y diagram places the majority of samples within the volcanic arc basalt (VAB) field, supporting an arc-related tectonic setting (Figure 5b,c). The Th/Nb vs. La/Yb plot further confirms a subduction-related signature, with all the samples plotting in the alkaline arc field (Figure 5c,d). Finally, the alteration index diagram confirms that the major element chemistry follows primary magmatic compositions, with the bulk of the samples falling within the igneous spectrum and showing no discernible signs of strong K or Na alteration (Figure 5e).
The normalized REE and multi-element patterns are shown in Figure 6a,b. The N-MORB normalized REE patterns display LREE enrichment and relatively flat heavy rare earth element (HREE) segments for all the analyzed samples from the Myrina, Romanou, and Katalakon units (Figure 5a). Only minor variations in slope and Eu anomalies are observed (Figure 6a). The multi-element diagram normalized to N-MORB shows pronounced enrichment in large ion lithophile elements (LILEs), such as Cs, Rb, Ba, Th, and U, and a distinct negative Nb–Ta anomaly (Figure 6b). Positive Pb anomalies are also evident, alongside a general depletion in high field strength elements (HFSEs), particularly Ti. Samples from all the volcanic units exhibit broadly similar geochemical trends to previously published samples from Limnos [24]. Higher Rb, Ba, Th, U, Nb, Sr, Ti, and Lu depletions are seen in previously published samples from Lesbos and Samothraki (Figure 6b) [21,31].

4.3. Magnetite, Ilmenite, and Titanite Mode of Occurrence

Magnetite, in the four selected samples, which also showed high magnetic susceptibility, is the ubiquitous metallic mineral always found set in the groundmass as subhedral to euhedral crystals. The size of the crystals rarely exceeds 400 μm. A detailed textural analysis is presented below (Table 4). Magnetite Mag1 (LIM 01, Myrina Unit) exhibits euhedral grains and thin ilmenite (Ilm1) lamellae (Figure 7a). It hosts inclusions of zircon and, locally, it is rimmed by apatite. Magnetite Mag2 (LIM 07, Romanou Unit) is distinguished by both very thin ilmenite (Ilm2) lamellae (Figure 7b), and by the occurrence of granular inclusions of ilmenite (Ilm2) in magnetite (Mag2). In sample LIM 07, embayed magnetite (Mag2) grains enveloped by biotite, with subordinate fine magnetite inclusions along cleavage planes, are found (Figure 7c). Magnetite Mag3 shows sparse and relatively thick ilmenite (Ilm3) lamellae, and bears inclusions of chalcopyrite, monazite, barite, and zircon, and it is rimmed by euhedral apatite (Figure 7d). In sample LIM 15, magnetite Mag4 appears as highly euhedral grains and clusters, showing a thick lamellae texture (Figure 7e). Ilmenite is missing and titanite (Ttn1) is found in the lamellas, along with mixed Fe–Ti phases (Figure 7f). Magnetite Mag4 is enclosed by epidote, K-feldspar, and apatite (Figure 7e).
Magnetite grains from fifteen volcanic rock samples across the Myrina, Romanou, and Katalakon units were characterized using ImageJ to quantify the grain morphology (Table 4). The images analyzed per sample range from 4 to 14, with the circularity values spanning from 0.81 to 0.94 (Table 4). Grains with a circularity >0.85 are classified as euhedral, those between 0.70 and 0.85 are subhedral, and those with a circularity score below 0.70 are classified as anhedral (after [65,66]). In the Myrina Unit, all the trachydacite samples (LIM 01 to 04, LIM 10) displayed circularities of 0.86–0.94, confirming euhedral habits, and average grain areas of 0.5%–2.4% (Table 4). Myrina dacites (LIM 09, LIM 11, LIM 12) ranged from 0.84 to 0.91, straddling the euhedral–subhedral boundary, with grain areas of 0.7%–1.3%. Myrina and Katalakon (Agios Ioannis Subunit) trachyandesites (LIM 13, LIM 16) exhibited the highest circularities (0.94, 0.90), both being euhedral, and had average areas between 1.1 and 1.4% (Table 4). The magnetite from sample LIM 07 (Romanou Unit), with a circularity of 0.81 and grain area of 2.6%, is subhedral. Magnetites from the Katalakon Unit (LIM 08, LIM 14, LIM 15) all exceeded 0.88 circularity (euhedral) and showed variable modal percentages (1.1%–3.6%).
The SEM–EDS analyses of magnetite from four selected samples revealed systematic variations in accessory Fe oxides and associated Ti oxides. The complete results are provided in Supplementary Table S2, while the calculated mineral formulas are presented in Table 5. In LIM 01 (trachydacite; Myrina Unit; N = 26), magnetite has an average of 83.73 wt.% FeOT, with TiO2 reaching 18.28 wt.%, and Al2O3 at 0.62 wt.%. Magnetite from sample LIM 07 (trachyandesite; Romanou Unit; N = 20) showed a slightly lower FeOT (81.26 wt.%), and a higher Al2O3 (4.37 wt.%) and TiO2 (15.29 wt.%), alongside elevated MgO (3.21 wt.%). In sample LIM 08 (andesite; Katalakon Unit; N = 18), magnetite returned an average 86.89 wt.% FeOT, 2.96 wt.% TiO2, and 1.19 wt.% Al2O3. Euhedral magnetite in LIM 15 (trachydacite; Katalakon Unit; N = 18) exhibited an average 89.82 wt.% FeOT, but lower TiO2 (1.05 wt.%) and Al2O3 (1.06 wt.%) values (Supplementary Table S2). The oxides MnO, V2O3, SiO2, Cr2O3, CaO, and NiO in magnetite remained below or close to 1 wt.% in all the samples (Supplementary Table S2).
Ilmenite grains after the SEM–EDS analysis revealed consistent Ti–Fe oxide compositions, with minor trace substitutions (Supplementary Table S2). In the Myrina trachydacite (LIM 01; N = 6), ilmenite averages 40.83 wt.% TiO2 and 47.45 wt.% FeOT, with MgO (4.59 wt.%), MnO (2.24 wt.%), Al2O3 (0.63 wt.%), and SiO2 (1.10 wt.%) as the minor components (Supplementary Table S2). The Romanou trachyandesite (LIM 07; N = 11) shows on average similar amounts of TiO2 (46.81 wt.%) and FeOT (43.11 wt.%), with slightly elevated MgO (3.20 wt.%) and Al2O3 (1.76 wt.%) averages. In the Katalakon andesite (LIM 08; N = 18), ilmenite incorporates 49.85 wt.% TiO2, and 47.13 wt.% FeOT, with MgO, MnO, Al2O3 and SiO2 being below 1 wt.% on average (Supplementary Table S2).
Titanite was detected and analyzed only in regard to sample LIM 15 (trachydacite; Katalakon Unit; N = 12) (Supplementary Table S2). It yielded on average (wt.%) 30.61 SiO2, 24.03 CaO, and 37.46 TiO2, with minor traces of Al2O3, FeO, MnO, and MgO.

4.4. Magnetic Susceptibility

The magnetic susceptibility results for the 15 volcanic rock samples collected on Limnos indicate a broad range of magnetic behaviors across different lithologies and volcanic units (Table 6). Trachydacites from the Myrina Unit (LIM 01 to 04, LIM 10) showed a wide range in terms of low-frequency magnetic susceptibility (LF Sus), which varies from 35.4 to 1344.7 × 10−8 m3/kg, with an average of 492.7 × 10−8 m3/kg, and a low average frequency dependence of 0.74% (Table 6). The Myrina trachyandesites (LIM 05, LIM 13) yielded a similar but slightly higher average LF susceptibility of 539 × 10−8 m3/kg, and a slightly lower average frequency dependence, averaging 1.5% (Table 6). On the contrary, the Myrina dacites (LIM 09, LIM 11, LIM 12) are characterized by relatively consistent and high LF susceptibility values (486.8–657.5 × 10−8 m3/kg), with a negligible average frequency dependence of 0.1% (Table 6). The trachyandesite sample from the Romanou Unit (LIM 07) showed an LF susceptibility of 502.2 × 10−8 m3/kg, with a frequency dependence of 0.92%. Sample LIM 08 (andesite; Katalakon Unit) displayed the highest LF value in the dataset of 1867.4 × 10−8 m3/kg and a minimal frequency dependence (0.10%) (Table 6). Katalakon trachydacites (LIM 14, LIM 15) also showed high magnetic susceptibility (979.9 to 1186.8 × 10−8 m3/kg), with a minor frequency dependence, averaging only 0.13%, while sample LIM 16 (trachyandesite; Agios Ioannis subunit) exhibited the highest frequency-dependent susceptibility peaking at 3.39% (Table 6).

5. Discussion

5.1. Petrogenesis of High-K to Shoshonitic Magmatism

As a consequence of its widespread upper Miocene high-K to shoshonitic volcanism, the Cenozoic magmatism of the Aegean region, a result of the complex tectonic interactions involving oceanic subduction and continental fragment collisions since the Eocene, offers an ideal environment for studying the genesis of potassium-rich magmas in subduction-related environments [10,11,19,20,21,31,43,44,51]. In-depth petro-geochemical data on Limnos Island from high-K calc-alkaline to shoshonitic volcanic and plutonic rocks, developed during or after subduction processes, were recently published by Gläser et al. [24]. According to Gläser et al. [24], the trachydacites of Limnos Island and the Fakos monzonite form a genetically related suite, which was produced under fractional crystallization at temperatures from 1100 to 700 °C and pressures around 0.5 to 0.1 GPa, with no detectable crustal contamination. The composition of the lavas may have also been impacted by the mixing of other related batches of magma. In contrast to what was previously seen in earlier rocks in the northern Aegean, the radiogenic isotope and incompatible element compositions of Limnos magmatic rocks show the introduction of a continental sediment component in the depleted mantle wedge. Gläser et al. [24] proposed that Mesozoic–Cenozoic sediments in the Apulian block influenced the trace element and isotope signature of the parental magmas and contributed to the magma source. This demonstrates how, between 30 and 20 million years ago, the sedimentary intake into the Aegean subduction zone changed. At the expense of olivine, the subducted sedimentary component formed enriched phlogopite–pyroxenite veins due to its interaction with the mantle rock. The variations between high-K and shoshonitic rocks on Limnos are ascribed to different sediment input into the mantle and the partial melting of this phlogopite–pyroxenite source [24].
The whole-rock geochemical results presented in this study further support previously published geochemical interpretations on the volcanic rocks at Limnos Island (e.g., [20,24,43]). The Katalakon (21.3 ± 0.7 to 20.2 ± 0.2 Ma; Early Miocene; Aquitanian; K–Ar ages, [44]), Romanou (20.5 ± 0.9 to 20.2 ± 0.8 Ma; Early Miocene; Aquitanian–Burdigalian; K–Ar ages [44]), and Myrina (19.3 ± 0.3 to 17.9 ± 0.4 Ma; Early Miocene; Burdigalian; K–Ar ages [44]) volcanic units constitute a genetically related suite of high-K calc-alkaline to shoshonitic compositions (Figure 4a–d). Their consistent classification across different geochemical parameters (major and trace elements) underscores the coherence of this magmatic system, likely influenced by a K-enriched mantle source, modified by subduction-related components and, subsequently, shaped by varying degrees of fractional crystallization, as suggested by Gläser et al. [24]. The slight variations observed within each unit and across the different diagrams likely reflect the complex interplay of source heterogeneity and magmatic processes (Figure 4a–d).
The view of Limnos volcanic rocks as a series of high-K calc-alkaline to shoshonitic rocks, primarily metaluminous to slightly peraluminous rocks, formed in a continental arc environment, is further supported by the geochemical diagrams presented in this study (Figure 5a–e). In line with the tectonic evolution of the Aegean region, as described by Gläser et al. [24], and the suggested involvement of a subduction-modified mantle source, enriched by continental sediments, the continental arc signature in the Th/Nb vs. La/Yb diagram and the volcanic arc basalt (VAB) affinity in the Cr-Y diagram both strongly support a subduction-related origin (Figure 5c,d).
Light rare earth elements (LREEs, e.g., La < 97 ppm, Ce < 182 ppm) are notably abundant in the samples from the Myrina Unit (Table 3), indicating a strong crustal or enhanced mantle influence. An evolved magmatic source is suggested by the increased Nb and Zr values found in most of the samples, particularly in Romanou (Nb < 20 ppm, Zr < 364 ppm), while Sr peaking in the Katalakon samples (<1415 ppm) and Rb peaking in the Romanou sample LIM 07 (<235 ppm) suggest varied fractional crystallization tendencies. The trace chalcophile and metalloid elements like Sb, Bi, and Tl exhibit isolated high values in the Myrina and Romanou samples (Table 3), which may indicate late-stage magmatic differentiation or minor sulfide mineralization, as suggested by the occurrence of chalcopyrite in the magnetite in sample LIM 07 (Figure 7d). Sample LIM 16 from the Agios Ioannis Subunit of the Katalakon Unit shows the greatest Ba values (<2590 ppm), suggesting potential hydrothermal alteration processes, possibly related to the transitional character of this volcanic rocks, as suggested by Pe-Piper et al. [20].
Furthermore, the trace element spider diagram shows a positive anomaly in Pd and negative anomalies in Nb, Ta, and Ti (Figure 6b). These patterns are typical of magmas associated with subduction and are frequently interpreted as proof of a depleted mantle wedge source, metasomatized by fluids or melts produced from slabs (e.g., [19,20,24]). The selective enrichment of these HFSE during residual phases, such as rutile, within the subducted slab is reflected in the Nb and Ta depletions, whereas their depletion in arc magmas is caused by their immobility in aqueous fluids (e.g., [19,20,24]). Likewise, the early fractionation of Fe–Ti oxides or the remaining Ti-bearing phases in the magmatic source could be the cause of the Ti anomaly. Although less frequent, the occurrence of a positive Pd anomaly could indicate a slight contribution from crustal contamination by mafic lithologies with higher Pd contents or modest enrichment by fluid-mobile materials from the subducting slab (e.g., [19,20,24]). These geochemical characteristics align with regional tectonic reconstructions of the Aegean arc system during the Neogene and are consistent with magma formation in a supra-subduction zone environment (e.g., [19,20,24]).

5.2. Fe–Ti Oxides and Magnetic Susceptibility as Petrogenetic Tracers

The micro-analytical data revealed subtle but significant inter-unit variations in the composition of iron–titanium oxides (Table 5, Supplementary Table S2). The SEM–EDS analyses revealed inter-unit variations in magnetite composition, specifically in regard to the extent of Ti and Al substitution within the crystal structure across the Limnos volcanic units (Table 5, Supplementary Table S2). Similarly, while exhibiting overall compositional homogeneity, the ilmenite exsolution lamellae within magnetite preserve minor inter-unit variations in the Mg and Al content, as well as Fe–Ti ratios (Table 5, Supplementary Table S2). Titanite, a common accessory phase, displays the expected Ca–Ti–Si stoichiometry, but also shows variable substitution of Fe and Al, along with trace amounts of Mn (Table 5, Supplementary Table S2).
The coexistence of magnetite with exsolved ilmenite suggests crystallization from a magma possessing an intermediate oxidation state, initially forming a Ti-rich magnetite solid solution that is subsequently unmixed into magnetite and ilmenite during cooling. The TiO2–FeO–Fe2O3 ternary diagram places all the magnetite analyses firmly within the high-temperature titanomagnetite field (Figure 8). Thus, reflecting significant Ti substitution into the magnetite structure (TiO2 up to ~20 mol%) and Fe3+-rich compositions, consistent with crystallization well above the ulvöspinel–magnetite solvus (>600 °C; e.g., [67,68]). The modest scatter of the magnetite data likely records minor variations in the magmatic oxygen fugacity or cooling rates across the trachydacite, trachyandesite, and andesite lithologies, yet no systematic shift correlates with the bulk rock type, indicating broadly similar Fe–Ti melt chemistry during oxide saturation.
Magnetite (Fe3O4) is the most strongly magnetic common mineral in igneous rocks, exhibiting high magnetic susceptibility due to its ferrimagnetic nature [69,70]. It is a crucial indicator in magnetic susceptibility measurements, since it typically dominates the bulk magnetic characteristics of the rock [70]. In contrast, hematite (Fe2O3) contributes very little to the total magnetic susceptibility, unless it is present in significant quantities [69,71]. It is weakly magnetic and frequently exhibits antiferromagnetic behavior at an ambient temperature. Depending on the temperature and content, ilmenite (FeTiO3), another oxide that contains iron, exhibits paramagnetic to weakly ferromagnetic activity [69,70]. Even though ilmenite is not very sensitive on its own, it becomes more important in rocks that contain magnetite in solid solutions or exhibit exsolution textures as titanomagnetite intergrowths. When pure magnetite is scarce in a sample, these mixed phases can improve the magnetic response and partially explain the susceptibility results [69,70].
The magnetic properties of Limnos volcanic rocks provide a valuable complement to the geochemical and petrological data in regard to understanding their formation and evolution within the complex Aegean tectonic setting. The discrimination plots comparing low-frequency magnetic susceptibility (LF Sus) versus whole-rock geochemistry for the analyzed samples point to Fe and Ti concentrations as the main geochemical elements that favorably affect magnetic susceptibility (Figure 9a–d). Lower Fe and Ti in more developed, silica-rich melts may result from the fractionation of iron–titanium oxides during magmatic differentiation, which could explain the negative trend in regard to SiO2 (Figure 9a). In comparison to some of the more silicic dacites, the andesite sample (LIM 08) constantly stands out due to its high LF Sus, relatively lower SiO2, and greater FeO3 and TiO2 (Figure 9a–c). This is possibly the result of different chemical compositions and petrogenetic pathways. The lack of correlation with the LOI indicates that alteration, as approximated by the volatile content, does not have primary control over the bulk magnetic susceptibility (Figure 9d).
Overall, the magnetic properties are consistent with typical volcanic rocks, wherein primary magnetic carriers have not undergone significant post-emplacement alteration. Stable, moderately coarse-grained magnetite predominates, mostly in the single-domain (SD) to multi-domain (MD) range, as indicated by the consistently low frequency dependency values (<1%) seen in the majority of samples (Table 6). This implies generally uniform cooling histories and limited low-temperature alteration, which is also in agreement with geochemical suggestions about the absence of hydrothermal alteration (Figure 5e) that would produce large amounts of very fine-grained magnetic phases. Thus, the bulk magnetic susceptibility is largely controlled by the concentration of magnetite, with a negligible contribution from superparamagnetic particles (SPs). Possibly as a result of K-rich alteration processes, the enhanced frequency dependency in a single sample (LIM 16, Agios Ioannis Subunit, Katalakon Unit) suggests a localized hydrothermal alteration, promoting finer magnetic grains (see also Figure 5e).
The bulk magnetic response is primarily controlled by the magnetite abundance, as is explicitly confirmed by the substantial positive correlation found between low-frequency susceptibility and the average modal percentage of magnetite (Figure 10a). Magnetite is the dominant magnetic carrier in these rocks, as seen by the noticeably increased susceptibilities of samples with higher magnetite concentrations (Figure 10a). Although some units indicate a general tendency of a rising LF Sus with a larger average magnetite grain size, the relationship is more complicated overall (Figure 10b). This suggests that although the presence of magnetite is crucial, the distribution of the grain sizes and how it affects magnetic alignment may have a secondary impact on the effectiveness of bulk susceptibility.
The notion that larger magnetite grains contribute less to the superparamagnetic percentage, leading to lower frequency dependency, is further supported by the negative association between frequency-dependent susceptibility and the average magnetite grain size (Figure 10c). This indicates that most of the magnetite in these samples is in stable SD or MD states. With the exception of the Agios Ioannis Subunit, Katalakon Unit trachyandesite (LIM 16), which indicates a higher fraction of finer, possibly SP-sized grains, the Myrina, Romanou, and Katalakon volcanic rocks that differ in terms magnetite grain sizes and frequency dependences most likely resulted from minor discrepancies in their cooling histories or the physicochemical circumstances surrounding the crystallization of magnetite. In particular, sample LIM 16 from the Agios Ioannis Subunit of the Katalakon Unit shows notable variability in regard to the rest of the Katalakon Unit (Figure 9a–d and Figure 10a–c), justifying the proposed assignment of a distinct subunit (after [20]).
The observed correlations show that the bulk magnetite abundance mostly determines the LF susceptibility across volcanic units, while the grain size and shape regulate SP vs. SD/MD partitioning (Freq.Dep.%). Stronger and more consistent magnetic reactions are typically associated with higher circularity, which is a sign of more euhedral, less deformed or altered grains. When the magnetic data are combined with the textural and mineral compositional data, it is concluded that the magnetic properties of Limnos volcanic rocks are primarily controlled by primary magmatic magnetite, with the variations between units probably reflecting minor variations in their petrogenetic evolution and cooling pathways.

6. Conclusions

This research on Limnos volcanic rocks, situated within the tectonically active Aegean region, contributes to previously published and well-established petrological and geochemical data by sharing new geochemical data and discussing magnetic susceptibility versus whole-rock chemistry and magnetite chemistry and texture. Overall, the analytical results indicate that at Limnos the volcanic rocks of the Katalakon, Romanou, and Myrina Units form a genetically related high-K calc-alkaline to shoshonitic suite. This suite was created by the fractional crystallization of parental magmas that came from a subduction-modified mantle source that was enriched by continental sediments from the Apulian block. The whole-rock geochemistry supports a continental arc setting for their formation. The variations in the trace elements relate to complex magmatic processes, such as source heterogeneity and localized hydrothermal alteration, as shown by the elevated Nb and Zr in the Romanou Unit, the high LREEs in the Myrina Unit, and the high Ba in the Agios Ioannis Subunit, Katalakon Unit. In addition, the micro-analytical data on magnetite, ilmenite, and titanite show minor compositional differences between the units, with ilmenite exhibiting changes in Mg, Al, and Fe–Ti ratios and magnetite exhibiting significant Ti and Al substitution, indicating different crystallization conditions between the units. The grain size and shape affect the proportion of superparamagnetic versus stable domain states, with higher circularity and more euhedral grains generally correlated with stronger magnetic responses, indicative of primary magmatic magnetite. The magnetic susceptibility measurements combined with the textural analysis of magnetite show that bulk susceptibility is primarily controlled by the magnetite abundance. The geochemical results coupled with the magnetic susceptibility results support the transitional character of the Agios Ioannis Subunit of the Katalakon Unit.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/min15070673/s1, Table S1: Calculations and conversions, Reference [52] are cited in the Supplementary Materials, Table S2: SEM–EDS and mineral formula summary tables.

Author Contributions

Conceptualization, C.L.S. and V.M.; methodology, C.L.S. and V.M.; software, C.L.S., V.M., L.P., A.D.L. and E.A.; validation, V.M., L.P. and E.A.; formal analysis, C.L.S.; data curation, C.L.S., A.D.L. and E.A.; writing—original draft preparation, C.L.S.; writing—review and editing, C.L.S., V.M., L.P. and E.A.; visualization, C.L.S.; funding acquisition, E.A. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded under the research project “Study of volcanic rocks from Limnos Island for a possible association with the sanctuary of Kavirio” (Contract number: 76400), by the Special Account for Research Funds (ELKE), Aristotle University of Thessaloniki (AUTH).

Data Availability Statement

The data is contained within the article or Supplementary Materials.

Acknowledgments

The authors would like to thank Aristeidis G. Stamatiadis for the preparation of the thin-polished sections. We sincerely thank four anonymous reviewers for their insightful comments and constructive feedback, which have greatly contributed to improving the quality of our manuscript.

Conflicts of Interest

The authors declare that there are no conflicts of interest.

References

  1. Miyashiro, A. Volcanic rock series in island arcs and active continental margins. Am. J. Sci. 1974, 274, 321–355. [Google Scholar] [CrossRef]
  2. McCulloch, M.T.; Gamble, J.A. Geochemical and geodynamical constraints on subduction zone magmatism. Earth Planet. Sci. Lett. 1991, 102, 358–374. [Google Scholar] [CrossRef]
  3. Hawkesworth, C.J.; Gallagher, K.; Hergt, J.M.; McDermott, F. Mantle and slab contributions in arc magmas. Ann. Rev. Earth Planet. Sci. 1993, 21, 175–204. [Google Scholar] [CrossRef]
  4. Schmidt, M.W.; Jagoutz, O. The global systematics of primitive arc melts. Geochem. Geophys. Geosyst 2017, 18, 2817–2854. [Google Scholar] [CrossRef]
  5. Davidson, J.P.; Hora, J.M.; Garrson, J.; Dungan, M.A. Crustal forensics in arc magmas. J. Volcanol. Geoth Res. 2005, 140, 157–170. [Google Scholar] [CrossRef]
  6. Sun, C.H.; Stern, R.J. Genesis of Mariana shoshonites: Contribution of the subduction component. J. Geophys. Res. 2001, 106, 589–608. [Google Scholar] [CrossRef]
  7. Marschall, H.R.; Schumacher, J.C. Arc magmas sourced from mélange diapirs in subduction zones. Nat. Geosci. 2012, 5, 862–867. [Google Scholar] [CrossRef]
  8. Straub, S.M.; LaGatta, A.B.; Martin-Del Pozzo, A.L.; Langmuir, C.H. Evidence from high-Ni olivines for a hybridized peridotite/pyroxenite source for orogenic andesites from the central Mexican Volcanic Belt. Geochem. Geophys. Geosyst 2008, 9, Q03007. [Google Scholar] [CrossRef]
  9. Perrin, A.; Goes, S.; Prytulak, J.; Rondenay, S.; Davies, D.R. Mantle wedge temperatures and their potential relation to volcanic arc location. Earth Planet. Sci. Lett. 2018, 501, 67–77. [Google Scholar] [CrossRef]
  10. Schaarschmidt, A.; Haase, K.M.; Voudouris, P.C.; Melfos, V.; Klemd, R. Migration of arc magmatism above mantle wedge diapirs with variable sediment contribution in the Aegean. Geochem. Geophys. Geosyst. 2021, 22, e2020GC009565. [Google Scholar] [CrossRef]
  11. Schaarschmidt, A.; Klemd, R.; Regelous, M.; Voudouris, P.; Melfos, V.; Haase, K.M. The formation of shoshonitic magma and its relationship to porphyry-type mineralisation: The Maronia pluton in NE Greece. Lithos 2012, 380–381, 105911. [Google Scholar] [CrossRef]
  12. Schmid, S.M.; Fügenschuh, B.; Kounov, A.; Matenco, L.; Nievergelt, P.; Oberhänsli, R.; Pleuger, J.; Schefer, S.; Schuster, R.; Tomljenovic, 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]
  13. 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]
  14. Jolivet, L.; Menant, A.; Sternai, P.; Rabillard, A.; Arbaret, L.; Augier, R.; Laurent, V.; Beaudoin, A.; Grasemann, B.; Huet, B.; et al. The geological signature of a slab tear below the Aegean. Tectonophysics 2015, 659, 166–182. [Google Scholar] [CrossRef]
  15. Brun, J.P.; Sokoutis, D. 45 my of Aegean crust and mantle flow driven by trench retreat. Geology 2010, 38, 815–818. [Google Scholar] [CrossRef]
  16. Brun, J.P.; Sokoutis, D. Core complex segmentation in North Aegean, a dynamic view. Tectonics 2018, 37, 1797–1830. [Google Scholar] [CrossRef]
  17. Rohrmeier, M.K.; von Quadt, A.; Driesner, T.; Heinrich, C.A.; Handler, R.; Ovtcharova, M.; Ivanov, Z.; Petrov, P.; Sarov, S.; Peytcheva, I. Post-orogenic extension and hydrothermal ore formation: High-precision geochronology of the central Rhodopian metamorphic core complex (Bulgaria-Greece). Econ. Geol. 2013, 108, 691–718. [Google Scholar] [CrossRef]
  18. van Hinsbergen, D.J.J.; Schmid, S.M. Map view restoration of Aegean-West Anatolian accretion and extension since the Eocene. Tectonics 2012, 31, TC5005. [Google Scholar] [CrossRef]
  19. Pe-Piper, G.; Piper, D.J.W. The Igneous Rocks of Greece: The Anatomy of an Orogen, 1st ed.; Gebrüder Borntraeger: Berlin, Germany, 2002; p. 645. [Google Scholar]
  20. Pe-Piper, G.; Piper, D.; Kokouvelas, I.; Dolansky, L.; Kokkalas, S. Postorogenic shoshonitic rocks and their origin by melting underplated basalts: The Miocene of Limnos, Greece. Geol. Soc. Am. Bull. 2009, 121, 39–54. [Google Scholar] [CrossRef]
  21. Pe-Piper, G.; Zhang, Y.; Piper, D.J.; Prelevic, D. Relationship of Mediterranean type lamproites to large shoshonite volcanoes, Miocene of Lesbos, NE Aegean Sea. Lithos 2014, 184–187, 281–299. [Google Scholar] [CrossRef]
  22. Christofides, G.; Pinarelli, L.; Pipera, K.; Soldatos, T.; Koroneos, A. Geochemical features of the depression basin-related magmatism in southeastern Rhodope massif and Circum-Rhodope Belt: The Tertiary Evros volcanic rocks (Western Thrace, northeastern Greece). Acta Vulcanol. J. Natl. Volcan. Group. Italy 2013, 25, 43–56. [Google Scholar]
  23. Erenoglu, O.; Bozcu, M.; Billor, M.Z. Age and petrology of Eocene-Oligocene calc-alkaline volcanism in Biga Peninsula (NW Turkey): Implications for magma origin and geodynamic evolution. J. Afr. Earth Sci. 2022, 192, 104559. [Google Scholar] [CrossRef]
  24. Gläser, L.; Grosche, A.; Voudouris, P.C.; Haase, K.M. The high-K calc-alkaline to shoshonitic volcanism of Limnos, Greece: Implications for the geodynamic evolution of the northern Aegean. Contrib. Mineral. Petrol. 2022, 177, 73. [Google Scholar] [CrossRef]
  25. Rabayrol, F.; Hart, C.J. Petrogenetic and tectonic controls on magma fertility and the formation of post-subduction porphyry and epithermal mineralization along the late Cenozoic Anatolian Metallogenic Trend, Turkey. Miner. Depos. 2021, 56, 279–306. [Google Scholar] [CrossRef]
  26. Börner, F.; Keith, M.; Bücker, J.L.; Voudouris, P.; Klemd, R.; Haase, K.; Kutzschbach, M.; Schiperski, F. In-situ trace element and S isotope systematics in pyrite from three porphyry-epithermal prospects, Limnos Island, Greece. Front. Earth Sci. 2022, 10, 916107. [Google Scholar] [CrossRef]
  27. Sanchez, M.G.; McClay, K.; King, A. Crustal extension and its relationship to porphyry Cu-Au and epithermal Au mineralization in the Biga Peninsula, NW Turkey. Soc. Econ. Geol. Spec. Publ. 2016, 19, 113–156. [Google Scholar]
  28. 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]
  29. 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]
  30. Stergiou, C.L.; Sakellaris, G.-A.; Melfos, V.; Voudouris, P.; Papadopoulou, L.; Kantiranis, N.; Peytcheva, I.; Chatzipetros, A.; Dimitrova, D.; Stefanova, E. Metallogeny and distribution of critical and strategic metals in the polymetallic vein mineralization at Kolchiko, Vertiskos Unit, northern Greece. J. Geoch. Expl. 2025, 272, 107708. [Google Scholar] [CrossRef]
  31. Vlahou, M.; Christofides, G.; Eleftheriadis, G.; Pinarelli, L.; Koroneos, A. Tertiary volcanic rocks from Samothraki island (north Aegean, Greece): Sr and Nd isotope constraints on their evolution. Geol. Soc. Am. Spec. Pap. 2006, 409, 283–304. [Google Scholar]
  32. Chatzipetros, A.; Kiratzi, A.; Sboras, S.; Zouros, N.; Pavlides, S. Active faulting in the north-eastern Aegean Sea Islands. Tectonophysics 2013, 597, 106–122. [Google Scholar] [CrossRef]
  33. Kondopoulou, D.; Atzemoglou, A.; Pavlides, S. Palaeomagnetism as a tool for testing geodynamic models in the North Aegean: Convergences, controversies and a further hypothesis. Geol. Soc. Spec. Publ. 1996, 105, 277–288. [Google Scholar] [CrossRef]
  34. Kondopoulou, D. Palaeomagnetism in Greece: Cenozoic and Mesozoic components and their geodynamic implications. Tectonophysics 2000, 326, 131–151. [Google Scholar] [CrossRef]
  35. Sakellariou, D.; Tsampouraki-Kraounaki, K. Plio-Quaternary extension and strike-slip tectonics in the Aegean. In Transform Plate Boundaries and Fracture Zones, 1st ed.; Duarte, J.C., Ed.; Elsevier: Amsterdam, Holland, 2019; pp. 339–374. [Google Scholar]
  36. Tranos, M.D. Faulting of Limnos Island; A mirror of faulting of the North Aegean Trough (Northern Greece). Tectonophysics 2009, 467, 72–88. [Google Scholar] [CrossRef]
  37. Westphal, M.; Kondopoulou, D. Paleomagnetism of Miocene volcanics from Lemnos island: Implications for block rotations in the vicinity of the north Aegean Trough. Ann. Τectonicae 1993, 7, 142–149. [Google Scholar]
  38. Koukousioura, O.; Kouli, K.; Gkouma, M.; Theocharidis, N.; Ntinou, M.; Chalkioti, A.; Dimou, V.G.; Fatourou, E.; Navrozidou, V.; Kafetzidou, A.; et al. Reconstructing the Environmental Conditions in the Prehistoric Coastal Landscape of SE Lemnos Island (Greece) Since the Late Glacial. Water 2025, 17, 220. [Google Scholar] [CrossRef]
  39. Pavlides, S.; Tsapanos, T.; Zouros, N.; Sboras, S.; Koravos, G.; Chatzipetros, A. Using active fault data for assessing seismic hazard: A case study from NE Aegean Sea, Greece. In Proceedings of the Earthquake Geotechnical Engineering Satellite Conference XVIIth International Conference on Soil Mechanics & Geotechnical Engineering, Alexandria, Egypt, 5–9 October 2009. [Google Scholar]
  40. Roussos, N. Geological Map of Greece: Myrina-Moudros Map Sheet, 1:50,000; IGME: Acharnes, Athens, 1987. [Google Scholar]
  41. Maravelis, A.G.; Boutelier, D.; Catuneanu, O.; Seymour, K.S.; Zelilidis, A. A review of tectonics and sedimentation in a forearc setting: Hellenic Thrace Basin, North Aegean Sea and Northern Greece. Tectonophysics 2016, 674, 1–19. [Google Scholar] [CrossRef]
  42. Marchev, P.; Raicheva, R.; Ivanova, R.; Peytcheva, I.; Grozdev, V. Early Oligocene Supereruption in SE Europe Outlined by 33.3 Ma U-Pb Ages for Limnos Tuff and Correlation with Regional Ash Deposits. C. R. Acad. Bulg. Sci. 2021, 74, 396–405. [Google Scholar]
  43. Innocenti, F.; Manetti, P.; Mazzuoli, R.; Pertusati, P.; Fytikas, M.; Kolios, N.; Vougioukalakis, G.E.; Androulakakis, N.; Critelli, S.; Caracciolo, L. Geological map (scale 1:50,000) of Limnos island (Greece): Explanatory notes. Acta Vulcanol. 2009, 21, 123–134. [Google Scholar]
  44. Innocenti, F.; Manetti, P.; Mazzuoli, R.; Pertusati, P.; Fytikas, M.; Kolios, N. The geology and geodynamic significance of the Island of Limnos, North Aegean Sea, Greece. Neues Jb Geol. 1994, 11, 661–691. [Google Scholar] [CrossRef]
  45. Fytikas, M.; Giuliani, O.; Innocenti, F.; Manetti, P.; Mazzuoli, R.; Peccerillo, A.; Villari, L. Neogene volcanism of the northern and central Aegean region. Ann. Geol. Pays Hell. 1980, 30, 106–129. [Google Scholar]
  46. Fytikas, M.; Innocenti, F.; Manetti, P.; Mazzuoli, R.; Peccerillo, A.; Villari, L. Teriary to Quaternary evolution of volcanism in the Aegean region. In Geological Evolution of the Eastern Mediterranean, 1st ed.; Dixon, J.E., Robertson, A.H.F., Eds.; Geological Society of London Special Publication: London, UK, 1984; Volume 17, pp. 687–699. [Google Scholar]
  47. Fornadel, A.P.; Voudouris, P.C.; Spry, P.G.; Melfos, V. Mineralogical, stable isotope, and fluid inclusion studies of spatially related porphyry Cu and epithermal Au-Te mineralization, Fakos Peninsula, Limnos Island, Greece. Miner. Petrol. 2012, 105, 85–111. [Google Scholar] [CrossRef]
  48. Erbil, Ü.; Okay, A.I.; Hakyemez, A. Late oligocene-early Miocene shortening in the Thrace Basin, northern Aegean. Int. J. Earth Sci. 2021, 110, 1921–1936. [Google Scholar] [CrossRef]
  49. Ring, U.; Layer, P.W.; Reischmann, T. Miocene high-pressure metamorphism in the Cyclades and Crete, Aegean Sea, Greece: Evidence for large-magnitude displacement on the Cretan detachment. Geology 2001, 29, 395–398. [Google Scholar] [CrossRef]
  50. Schneider, C.A.; Rasband, W.S.; Eliceiri, K.W. NIH Image to ImageJ: 25 years of image analysis. Nat. Methods 2012, 9, 671–675. [Google Scholar] [CrossRef]
  51. Pe-Piper, G.; Piper, D.J. Geochemical variation with time in the Cenozoic high-K volcanic rocks of the island of Lesbos, Greece: Significance for shoshonite petrogenesis. J. Volcanol. Geotherm. Res. 1992, 53, 371–387. [Google Scholar] [CrossRef]
  52. Gündüz, M.; Asan, K. PetroGram: An excel-based petrology program for modeling of magmatic processes. Geosci. Front. 2013, 12, 81–92. [Google Scholar] [CrossRef]
  53. Dearing, J.A.; Dann, R.J.L.; Hay, K.; Lees, J.A.; Loveland, P.J.; Maher, B.A.; O’grady, K. Frequency-dependent susceptibility measurements of environmental materials. Geophys. J. Int. 1996, 124, 228–240. [Google Scholar] [CrossRef]
  54. Tarling, D.; Hrouda, F. Magnetic Anisotropy of Rocks, 1st ed.; Champan and Hall: London, UK, 1993; p. 218. [Google Scholar]
  55. Hrouda, F. Magnetic anisotropy of rocks and its application in geology and geophysics. Geophys. Surv. 1982, 5, 37–82. [Google Scholar] [CrossRef]
  56. Le Bas, M.J.; Le Maitre, R.W.; Streckeisen, A.; Zanettin, B. A chemical classification of volcanic rocks based on the total alkali-silica diagram. J. Petrol. 1986, 27, 745–750. [Google Scholar] [CrossRef]
  57. Winchester, J.A.; Floyd, P.A. Geochemical discrimination of different magma series and their differentiation products using immobile elements. Chem. Geol. 1977, 20, 325–343. [Google Scholar] [CrossRef]
  58. Peccerillo, A.; Taylor, S.R. Geochemistry of Eocene calc-alkaline volcanic rocks from the Kastamonu area, northern Turkey. Contrib. Mineral. Petrol. 1976, 58, 63–81. [Google Scholar] [CrossRef]
  59. Pearce, J.A. A users guide to basalt discrimination diagrams. In Trace Element Geochemistry of Volcanic Rocks: Applications for Massive Sulphide Exploration; Wyman, D.A., Ed.; Geological Association of Canada: St. John’s, NL, Canada, 1996; Short Course Notes 12; pp. 79–113. [Google Scholar]
  60. Frost, B.R.; Frost, C.D. A geochemical classification for feldspathic igneous rocks. J. Petrol. 2008, 49, 1955–1969. [Google Scholar] [CrossRef]
  61. Pearce, J.A. Trace element characteristics of lavas from destructive plate boundaries. In Andesites: Orogenic Andesites and Related Rocks, 1st ed.; Thorp, R.S., Ed.; John Wiley and Sons: New York, NY, USA, 1982; pp. 525–548. [Google Scholar]
  62. Hollocher, K.; Robinson, P.; Walsh, E.; Roberts, D. Geochemistry of amphibolite-facies volcanics and gabbros of the Støren Nappe in extensions west and southwest of Trondheim, Western Gneiss Region, Norway: A key to correlations and paleotectonic settings. Am. J. Sci. 2012, 312, 357–416. [Google Scholar] [CrossRef]
  63. Hughes, C.J. Spilites, keratophyres, and the igneous spectrum. Geol. Mag. 1972, 109, 513–527. [Google Scholar] [CrossRef]
  64. Sun, S.S.; McDonough, W.F. Chemical and isotopic systematics of oceanic basalts: Implications for mantle composition and processes. Geol. Soc. Lond. Spec. Publ. 1989, 42, 313–345. [Google Scholar] [CrossRef]
  65. Gualda, G.A.; Ghiorso, M.S.; Lemons, R.V.; Carley, T.L. Rhyolite-MELTS: A modified calibration of MELTS optimized for silica-rich, fluid-bearing magmatic systems. J. Petrol. 2012, 53, 875–890. [Google Scholar] [CrossRef]
  66. Marsh, B.D. On the interpretation of crystal size distributions in magmatic systems. J. Petrol. 1998, 39, 553–599. [Google Scholar] [CrossRef]
  67. Buddington, A.F.; Linsley, D.H. Iron-titanium oxides minerals and synthetic equivalents. J. Petrol. 1964, 5, 310–357. [Google Scholar] [CrossRef]
  68. Carmichael, R.S. Practical Handbook of Physical Properties of Rocks and Minerals, 1st ed.; CRC Press Inc.: Boca Raton, FL, USA, 1989; p. 756. [Google Scholar]
  69. Borradaile, G.J. Magnetic susceptibility, petrofabrics and strain. Tectonophysics 1988, 156, 1–20. [Google Scholar] [CrossRef]
  70. Ishihara, S.; Hashimoto, M.; Machida, M. Magnetite/ilmenite–series classification and magnetic susceptibility of the Mesozoic-Cenozoic batholiths in Peru. Resour. Geol. 2000, 50, 123–129. [Google Scholar] [CrossRef]
  71. Flanders, P.J.; Remeika, J.P. Magnetic properties of hematite single crystals. Philos. Mag. A J. Theor. Exp. Appl. Phys. 1965, 11, 1271–1288. [Google Scholar] [CrossRef]
Minerals 15 00673 g001
Figure 1. (a) Geological map of Limnos Island showing the allocation of sedimentary and igneous rocks, as well as the major tectonic structures (modified after [20,32,39,40,41,42,43,44]); and (b) inset map of the Aegean Sea depicting the location of Limnos Island (red rectangle) in respect to the geotectonic zones of the Hellenic orogen and the main tectonic units of Greece and western Turkey. The distribution of shoshonitic volcanic rocks in the northern Aegean Sea (pale orange overlay), the South Aegean Volcanic Arc (SAVA) (pale red overlay), the North Anatolian Fault Zone (NAFZ), and the Hellenic trench are shown. Abbreviations: SAM = Samothrace, LEM = Limnos, LES = Lesbos, BIGA = Biga peninsula (modified after [19,20,24,30]).
Figure 1. (a) Geological map of Limnos Island showing the allocation of sedimentary and igneous rocks, as well as the major tectonic structures (modified after [20,32,39,40,41,42,43,44]); and (b) inset map of the Aegean Sea depicting the location of Limnos Island (red rectangle) in respect to the geotectonic zones of the Hellenic orogen and the main tectonic units of Greece and western Turkey. The distribution of shoshonitic volcanic rocks in the northern Aegean Sea (pale orange overlay), the South Aegean Volcanic Arc (SAVA) (pale red overlay), the North Anatolian Fault Zone (NAFZ), and the Hellenic trench are shown. Abbreviations: SAM = Samothrace, LEM = Limnos, LES = Lesbos, BIGA = Biga peninsula (modified after [19,20,24,30]).
Minerals 15 00673 g001
Minerals 15 00673 g002
Figure 2. Representative field photographs and macro-photographs of hand specimens from the Limnos volcanic rocks: (a) satellite imagery overlaid by the volcanic rocks outcropping in western Limnos (also see the legend in Figure 1) and the sampling locations (yellow pins), and the major towns are highlighted (red cycles); (b) a lava dome near survey site LIM 05; (c) lava flows at survey site LIM 12 (Myrina Unit) made of dacite; (d) a K-feldspar (Kfs) phenocryst set in a dacite sample from survey site LIM 12 (Myrina Unit); (e) a grey colored trachydacite sample (LIM 01; Myrina Unit) showing abundant feldspar phenocrysts set in a fine-grained groundmass, with scattered mafic minerals; (f) a trachyandesite sample (LIM 07; Romanou Unit) showing a light brown tint with a few feldspar phenocrysts and almost parallel, aligned mafic minerals; and (g) a trachydacite sample (LIM 15; Katalakon Unit) incorporating feldspar phenocrysts and clusters of mafic minerals (red dashed lines), set in a dark brownish color groundmass.
Figure 2. Representative field photographs and macro-photographs of hand specimens from the Limnos volcanic rocks: (a) satellite imagery overlaid by the volcanic rocks outcropping in western Limnos (also see the legend in Figure 1) and the sampling locations (yellow pins), and the major towns are highlighted (red cycles); (b) a lava dome near survey site LIM 05; (c) lava flows at survey site LIM 12 (Myrina Unit) made of dacite; (d) a K-feldspar (Kfs) phenocryst set in a dacite sample from survey site LIM 12 (Myrina Unit); (e) a grey colored trachydacite sample (LIM 01; Myrina Unit) showing abundant feldspar phenocrysts set in a fine-grained groundmass, with scattered mafic minerals; (f) a trachyandesite sample (LIM 07; Romanou Unit) showing a light brown tint with a few feldspar phenocrysts and almost parallel, aligned mafic minerals; and (g) a trachydacite sample (LIM 15; Katalakon Unit) incorporating feldspar phenocrysts and clusters of mafic minerals (red dashed lines), set in a dark brownish color groundmass.
Minerals 15 00673 g002
Minerals 15 00673 g003
Figure 3. Representative photomicrographs showing typical mineralogical paragenesis and mineral textures (transmitted plane polarized light (b,c,f); transmitted crossed-polarized light (a,d,e); reflected plane polarized light (g–i)) of the volcanic rocks sampled from the Myrina (LIM 01, LIM 03, LIM 05, LIM 10, LIM 12), Romanou (LIM 07), and Katalakon (LIM 08, LIM 14) units at Limnos island: (a) plagioclase (Pl), hornblende (Hbl), and rounded quartz (Qz) set in a fine-grained groundmass, including quartz and plagioclase in a trachydacite (LIM 01); (b) hornblende (Hbl) and plagioclase (Pl) forming a porphyritic texture and magnetite (Mag) in a trachyandesite sample (LIM 05); (c) hornblende (Hbl), biotite (Bt), and plagioclase (Pl) set in a fine-grained groundmass, with minor magnetite (Mag), in a dacite sample (LIM 12); (d) feldspar (Fsp) and plagioclase (Pl) and larger euhedral hornblende (Hbl) set in a fine-grained groundmass, comprising acicular feldspar microlites and microlitic mafic phases in a trachyandesite (LIM 07); (e) hydrothermally altered hornblende (Hbl) and quartz (Qz) set in fine-grained groundmass of quartz and plagioclase in an andesite sample (LIM 08); (f) biotite (Bt) with numerous magnetite (Mag) inclusions and hornblende (Hbl) set in a fine-grained groundmass, consisting of plagioclase (Pl), in a trachydacite sample (LIM 14); (g) magnetite (Mag) showing ilmenite (Ilm) exsolution lamellae found in hornblende (Hbl) in a trachydacite sample (LIM 03); (h) magnetite (Mag) grains and a clinopyroxene (Cpx) cluster in a trachydacite sample (LIM 10); and (i) magnetite (Mag) oxidized peripherically to hematite (Hem), bearing euhedral apatite (Ap) inclusions, in a trachydacite sample (LIM 14).
Figure 3. Representative photomicrographs showing typical mineralogical paragenesis and mineral textures (transmitted plane polarized light (b,c,f); transmitted crossed-polarized light (a,d,e); reflected plane polarized light (g–i)) of the volcanic rocks sampled from the Myrina (LIM 01, LIM 03, LIM 05, LIM 10, LIM 12), Romanou (LIM 07), and Katalakon (LIM 08, LIM 14) units at Limnos island: (a) plagioclase (Pl), hornblende (Hbl), and rounded quartz (Qz) set in a fine-grained groundmass, including quartz and plagioclase in a trachydacite (LIM 01); (b) hornblende (Hbl) and plagioclase (Pl) forming a porphyritic texture and magnetite (Mag) in a trachyandesite sample (LIM 05); (c) hornblende (Hbl), biotite (Bt), and plagioclase (Pl) set in a fine-grained groundmass, with minor magnetite (Mag), in a dacite sample (LIM 12); (d) feldspar (Fsp) and plagioclase (Pl) and larger euhedral hornblende (Hbl) set in a fine-grained groundmass, comprising acicular feldspar microlites and microlitic mafic phases in a trachyandesite (LIM 07); (e) hydrothermally altered hornblende (Hbl) and quartz (Qz) set in fine-grained groundmass of quartz and plagioclase in an andesite sample (LIM 08); (f) biotite (Bt) with numerous magnetite (Mag) inclusions and hornblende (Hbl) set in a fine-grained groundmass, consisting of plagioclase (Pl), in a trachydacite sample (LIM 14); (g) magnetite (Mag) showing ilmenite (Ilm) exsolution lamellae found in hornblende (Hbl) in a trachydacite sample (LIM 03); (h) magnetite (Mag) grains and a clinopyroxene (Cpx) cluster in a trachydacite sample (LIM 10); and (i) magnetite (Mag) oxidized peripherically to hematite (Hem), bearing euhedral apatite (Ap) inclusions, in a trachydacite sample (LIM 14).
Minerals 15 00673 g003
Minerals 15 00673 g004
Figure 4. Geochemical classification plots for the analyzed volcanic samples from Limnos: (a) plot of total alkalis (wt.%) vs. SiO2 (wt.%) (TAS diagram after [56]); (b) plot of silica (wt.%) vs. Zr/TiO2 (wt.%) ratio (after [57]); (c) plot of K2O (wt.%) vs. SiO2 (wt.%) (after [58]); and (d) plot of Zr/Ti ratio (ppm) vs. Nb/Y ratio (ppm) for the analyzed volcanic rocks (after [59]).
Figure 4. Geochemical classification plots for the analyzed volcanic samples from Limnos: (a) plot of total alkalis (wt.%) vs. SiO2 (wt.%) (TAS diagram after [56]); (b) plot of silica (wt.%) vs. Zr/TiO2 (wt.%) ratio (after [57]); (c) plot of K2O (wt.%) vs. SiO2 (wt.%) (after [58]); and (d) plot of Zr/Ti ratio (ppm) vs. Nb/Y ratio (ppm) for the analyzed volcanic rocks (after [59]).
Minerals 15 00673 g004
Minerals 15 00673 g005
Figure 5. Geochemical and tectonic setting classification plots for the analyzed volcanic samples from Limnos: (a) plot of alkalis–CaO (wt.%) vs. SiO2 (wt.%) (after [60]); (b) plot of alkalinity index (AI = Al − (K + Na) vs. feldspathoid silica saturation (FSSI = Q − [Lc + 2(Ne + Kp0]/100), where Q = quartz normative content (in wt% or mol%), Lc = leucite normative content, Ne = nepheline normative content, Kp0 = kaliophilite (K-feldspathoid) normative content, after [60]); (c) plot of Cr (ppm) vs. Y (ppm), where MORB = mid-ocean ridge basalt, WPB = within plate basalt, and VAB = volcanic arc basalt (after [61]); (d) plot of Th/Nb ratio (ppm) vs. La/Yb ratio (ppm) (after [62]); and (e) plot of alteration index (after [63]).
Figure 5. Geochemical and tectonic setting classification plots for the analyzed volcanic samples from Limnos: (a) plot of alkalis–CaO (wt.%) vs. SiO2 (wt.%) (after [60]); (b) plot of alkalinity index (AI = Al − (K + Na) vs. feldspathoid silica saturation (FSSI = Q − [Lc + 2(Ne + Kp0]/100), where Q = quartz normative content (in wt% or mol%), Lc = leucite normative content, Ne = nepheline normative content, Kp0 = kaliophilite (K-feldspathoid) normative content, after [60]); (c) plot of Cr (ppm) vs. Y (ppm), where MORB = mid-ocean ridge basalt, WPB = within plate basalt, and VAB = volcanic arc basalt (after [61]); (d) plot of Th/Nb ratio (ppm) vs. La/Yb ratio (ppm) (after [62]); and (e) plot of alteration index (after [63]).
Minerals 15 00673 g005
Minerals 15 00673 g006
Figure 6. (a) Rare earth element discrimination diagram for Limnos volcanic rocks. Normalized to N-MORB values after [64]; and (b) multi-element diagram normalized to N-MORB [64], where the trace elements are sorted by incompatibility in descending order. Magmatic geochemical signatures from Lesbos [21] and Samothraki [31] are shown (dashed outline of a polygon), as well as those from Limnos [red outline of a polygon; [24]].
Figure 6. (a) Rare earth element discrimination diagram for Limnos volcanic rocks. Normalized to N-MORB values after [64]; and (b) multi-element diagram normalized to N-MORB [64], where the trace elements are sorted by incompatibility in descending order. Magmatic geochemical signatures from Lesbos [21] and Samothraki [31] are shown (dashed outline of a polygon), as well as those from Limnos [red outline of a polygon; [24]].
Minerals 15 00673 g006
Minerals 15 00673 g007
Figure 7. SEM back-scattered electron images of magnetite, ilmenite, and titanite in the studied samples from Limnos: (a) magnetite (Mag1) with thin ilmenite (Ilm1) lamellae and zircon (Zrn) inclusions from sample LIM 01; (b) magnetite (Mag2) showing very thin ilmenite (Ilm2) lamellae from sample LIM 07; (c) magnetite (Mag3) grains enveloped by biotite with fine magnetite inclusions along cleavage planes (white dashed lines highlight the respected area) from sample LIM 07; (d) magnetite (Mag3) with thick ilmenite (Ilm3) lamellae and chalcopyrite (Ccp) as inclusion, rimmed by apatite (Ap) from sample LIM 08; (e) a cluster of euhedral magnetite (Mag4) bearing titanite (Ttn1) and apatite (Ap), enveloped by K-feldspar (Kfs) and epidote (Ep), from sample LIM 15; and (f) a detail of euhedral magnetite (Mag4) with a lamellae texture, where ilmenite has been replaced by titanite (Ttn1).
Figure 7. SEM back-scattered electron images of magnetite, ilmenite, and titanite in the studied samples from Limnos: (a) magnetite (Mag1) with thin ilmenite (Ilm1) lamellae and zircon (Zrn) inclusions from sample LIM 01; (b) magnetite (Mag2) showing very thin ilmenite (Ilm2) lamellae from sample LIM 07; (c) magnetite (Mag3) grains enveloped by biotite with fine magnetite inclusions along cleavage planes (white dashed lines highlight the respected area) from sample LIM 07; (d) magnetite (Mag3) with thick ilmenite (Ilm3) lamellae and chalcopyrite (Ccp) as inclusion, rimmed by apatite (Ap) from sample LIM 08; (e) a cluster of euhedral magnetite (Mag4) bearing titanite (Ttn1) and apatite (Ap), enveloped by K-feldspar (Kfs) and epidote (Ep), from sample LIM 15; and (f) a detail of euhedral magnetite (Mag4) with a lamellae texture, where ilmenite has been replaced by titanite (Ttn1).
Minerals 15 00673 g007
Minerals 15 00673 g008
Figure 8. Average analysis (atom per formula unit: a.p.f.u.) of magnetite and ilmenite obtained after SEM–EDS analysis are shown on a ternary diagram of FeO–TiO2–Fe2O3. Approximate equilibrium lines and oxidation direction are shown (modified after [67,68]).
Figure 8. Average analysis (atom per formula unit: a.p.f.u.) of magnetite and ilmenite obtained after SEM–EDS analysis are shown on a ternary diagram of FeO–TiO2–Fe2O3. Approximate equilibrium lines and oxidation direction are shown (modified after [67,68]).
Minerals 15 00673 g008
Minerals 15 00673 g009
Figure 9. Discrimination diagrams of low-frequency magnetic susceptibility (LF Sus) vs. whole-rock geochemistry: (a) LF Sus vs. SiO2l; (b) LF Sus vs. Fe2O3; (c) LF Sus vs. TiO2; and (d) LF Sus vs. loss of ignition (LOI).
Figure 9. Discrimination diagrams of low-frequency magnetic susceptibility (LF Sus) vs. whole-rock geochemistry: (a) LF Sus vs. SiO2l; (b) LF Sus vs. Fe2O3; (c) LF Sus vs. TiO2; and (d) LF Sus vs. loss of ignition (LOI).
Minerals 15 00673 g009
Minerals 15 00673 g010
Figure 10. Discrimination diagrams of low-frequency magnetic susceptibility (LF Sus) versus (a) average modal percentage of magnetite; (b) average magnetite size; and (c) frequency-dependent susceptibility versus average magnetite size.
Figure 10. Discrimination diagrams of low-frequency magnetic susceptibility (LF Sus) versus (a) average modal percentage of magnetite; (b) average magnetite size; and (c) frequency-dependent susceptibility versus average magnetite size.
Minerals 15 00673 g010
Table 1. Sample identification numbers, localities with coordinates (WGS84), and lithological descriptions.
Table 1. Sample identification numbers, localities with coordinates (WGS84), and lithological descriptions.
Sample IDCoordinates (Latitude/Longitude)Lithological Description
LIM 0139.886600° 25.069800°Trachydacite; Myrina Unit
LIM 0239.892100° 25.082300°Trachydacite; Myrina Unit
LIM 0339.900800° 25.091800°Trachydacite; Myrina Unit
LIM 0439.913400° 25.084800°Trachydacite; Myrina Unit
LIM 0539.915062° 25.112126°Trachyandesite; Myrina Unit
LIM 0739.903600° 25.208600°Trachyandesite; Romanou Unit
LIM 0839.897700° 25.173900°Andesite; Katalakon Unit
LIM 0939.872200° 25.153800°Dacite; Myrina Unit
LIM 1039.865000° 25.124500°Trachydacite; Myrina Unit
LIM 1139.884200° 25.154700°Dacite; Myrina Unit
LIM 1239.873400° 25.102300°Dacite; Myrina Unit
LIM 1339.869000° 25.054800°Trachyandesite; Myrina Unit
LIM 1439.957100° 25.164800°Trachydacite; Katalakon Unit
LIM 1539.943010° 25.154000°Trachydacite; Katalakon Unit
LIM 1639.930310° 25.061500°Trachyandesite; Agios Ioannis Subunit; Katalakon Unit
Table 2. Chemical composition of major elements in analyzed samples from the Katalakon, Myrina, and Romanou units from western Limnos. Rock types: 1 = trachydacite, 2 = trachyandesite, 3 = andesite, 4 = dacite.
Table 2. Chemical composition of major elements in analyzed samples from the Katalakon, Myrina, and Romanou units from western Limnos. Rock types: 1 = trachydacite, 2 = trachyandesite, 3 = andesite, 4 = dacite.
Volcanic UnitsMyrinaRomanouKatalakon
1 2414 2231 2
LODLIM
01		LIM
02		LIM
03		LIM
04		LIM
05		LIM
09		LIM
10		LIM
11		LIM
12		LIM
13		LIM
07		LIM
08		LIM
14		LIM
15		LIM
16
wt.%
SiO20.0161.8264.5364.8262.7660.1962.8459.260.7563.9161.1757.7356.9560.3960.5661.05
Al2O30.0114.8213.215.0616.0616.4815.9715.3315.0515.415.431615.371616.1914.89
Fe2O30.013.623.373.543.695.394.965.274.744.465.627.337.014.8455.77
CaO0.014.663.842.992.974.254.214.993.633.43.894.855.743.713.822.83
MgO0.011.261.791.621.882.222.413.212.531.832.382.843.631.932.262.85
Na2O0.013.542.483.353.483.53.693.472.993.783.723.453.044.283.763.44
K2O0.013.313.764.414.783.393.563.133.453.624.053.562.813.463.345.26
MnO0.010.070.070.070.060.060.080.10.10.070.080.070.130.090.10.08
TiO20.010.50.50.530.580.730.650.740.610.680.810.920.630.640.94
P2O50.010.220.280.290.30.410.420.380.340.410.520.50.450.310.310.43
Cr2O30.01bdlbdlbdlbdlbdlbdlbdlbdlbdl0.02bdlbdlbdlbdl0.03
SrO0.010.110.060.070.070.120.160.140.090.10.090.130.140.090.10.11
BaO0.010.190.10.120.130.230.280.230.270.120.190.240.260.190.20.27
LOI0.014.364.591.521.381.592.054.351.442.292.854.613.152.272.43
Total-98.4998.5698.3798.7598.37100.8398.2698.999.23100.24100.56101.0699.0898.54100.39
TC0.010.450.580.05<0.010.030.010.030.320.090.180.210.570.40.090.01
TS0.010.030.020.02<0.010.020.010.020.01<0.010.040.030.02<0.010.010.1
bdl = below detection limit, LOD = limit of detection, LOI = loss of ignition.
Table 3. Rare earth element (REE) chemical composition in analyzed samples from Limnos. Rock types: 1 = trachydacite, 2 = trachyandesite, 3 = andesite, 4 = dacite.
Table 3. Rare earth element (REE) chemical composition in analyzed samples from Limnos. Rock types: 1 = trachydacite, 2 = trachyandesite, 3 = andesite, 4 = dacite.
Volcanic UnitsMyrinaRomanouKatalakon
1241422312
LODLIM
01		LIM
02		LIM
03		LIM
04		LIM
05		LIM
09		LIM
10		LIM
11		LIM
12		LIM
13		LIM
07		LIM
08		LIM
14		LIM
15		LIM
16
Trace elements (ppm)
Ba0.515758861012110819452363211725901059179317762138166017132287
Cr104539354322306236539839332630181
Cs0.015.83.33.33.01.66.13.02.95.34.90.992.36.52.04.6
Ga0.2181718192120191919201921212119
Hf0.25.78.78.89.87.27.97.16.79.19.57.97.47.56.112
Nb0.1111414161214121318201112111118
Rb0.211313415116390116961101581721057710488235
Sn5bdlbdlbdlbdlbdlbdlbdlbdlbdlbdlbdlbdlbdlbdlbdl
Sr0.193151968564011021415116775588279611271265884969905
Ta0.10.60.811.10.70.7111.31.50.50.60.60.71
Th0.05352224273140283234372430262431
U0.057.36.36.574.58.04.76.17.67.23.54.03.73.57.4
V1084687976126114113988411915817211710985
W1bdlbdlbdlbdlbdlbdl12bdl2bdlbdlbdlbdl4
Y0.5171820202626242023222629232522
Zr2177291288307245259258244346354266247254200364
Ag0.010.070.040.070.070.060.030.060.050.040.080.090.060.050.040.05
Cd0.020.270.060.050.040.070.050.10.050.040.070.080.10.080.160.03
Cu0.2251715141627141817323433138.532
Mo0.052.01.41.61.71.81.73.23.02.32.72.72.84.02.42.4
Ni0.2131212147.8132112172717137.29.989
Pb0.5834850485472575662545155425354
Zn2514951527587685955597578638461
As0.11.51.61.71.80.81.311.313.42.21.11.71.81.3
Bi0.010.030.110.050.140.070.180.030.110.080.070.020.040.030.050.01
Hg0.0050.007bdlbdlbdlbdlbdlbdlbdlbdl0.007bdl0.005bdlbdl0.008
Sb0.050.130.310.240.230.150.60.160.540.170.670.410.20.920.110.19
Se0.2bdlbdlbdlbdlbdlbdlbdlbdlbdlbdlbdlbdlbdlbdlbdl
Tl0.020.050.120.110.130.130.20.110.130.310.280.030.040.02b.d.l.0.06
Trace elements (ppb)
Au0.53.91.511.30.80.80.50.71.31.52.50.90.9bdl1.3
Rare earth elements (ppm)
La0.1634855589197757262627694697168
Ce0.111198107115164182142135122119142175130134132
Pr0.03121112131920161515151720141516
Nd0.1414144486971605356546371525261
Sm0.035.56.26.77.310109.07.98.38.29.7107.78.09.8
Eu0.031.51.51.81.82.52.72.21.92.02.02.72.82.02.22.5
Gd0.054.65.05.25.78.17.77.06.26.56.27.78.36.26.47.3
Tb0.010.560.660.710.7410.970.90.780.850.831.01.10.820.860.93
Dy0.052.93.33.63.85.14.74.63.84.64.35.15.34.14.34.7
Ho0.010.570.570.630.670.880.870.850.710.790.790.90.950.740.820.85
Er0.031.71.71.82.02.42.42.52.12.52.42.52.72.22.42.3
Tm0.010.270.260.250.30.370.350.330.310.370.330.360.410.330.340.35
Yb0.031.71.61.71.72.32.22.22.02.12.12.32.52.12.12.3
Lu0.010.310.250.270.290.360.370.310.310.350.350.350.380.330.350.35
Eu/Eu *-0.900.810.920.840.840.930.830.820.820.840.940.920.870.920.89
ΣREE-245219239258376403324301282277331394291300307
bdl = below detection limit, LOD = limit of detection.
Table 4. Textural parameters obtained using image analysis (ImageJ software, version 1.54p, Schneider et al. [50]). Area % represents modal percentages of magnetite. Circularity corresponds to euhedral (>0.85), subhedral (0.70–0.85), and anhedral (<0.70) grains.
Table 4. Textural parameters obtained using image analysis (ImageJ software, version 1.54p, Schneider et al. [50]). Area % represents modal percentages of magnetite. Circularity corresponds to euhedral (>0.85), subhedral (0.70–0.85), and anhedral (<0.70) grains.
Area %TextureRock Type/Volcanic Unit
SampleNMINMAXSTDEVAVGAverage Crystal Size (μm)Circularity
LIM 0150.703.91.32.42310.90Trachydacite; Myrina Unit
LIM 0250.571.60.40.9970.94Trachydacite; Myrina Unit
LIM 03140.080.80.30.5880.91Trachydacite; Myrina Unit
LIM 0450.290.80.20.51830.87Trachydacite; Myrina Unit
LIM 10130.392.60.60.91030.86Trachydacite; Myrina Unit
Average0.411.90.571.01400.90
LIM 0570.3614.65.03.64550.90Trachyandesite; Myrina Unit
LIM 1380.474.51.31.41130.94Trachyandesite; Myrina Unit
Average0.419.53.22.52840.92
LIM 0940.191.50.60.7760.88Dacite; Myrina Unit
LIM 1140.792.10.61.32950.91Dacite; Myrina Unit
LIM 1290.136.32.01.22490.84Dacite; Myrina Unit
Average0.373.31.11.02070.88
LIM 0790.468.32.72.64170.81Trachyandesite; Romanou Unit
LIM 0861.186.52.12.81250.88Andesite; Katalakon Unit
LIM 14100.933.91.12.72690.90Trachydacite; Katalakon Unit
LIM 15100.341.70.51.1600.91Trachydacite; Katalakon Unit
Average0.632.80.811.91640.90
LIM 1690.612.00.71.1580.90Trachyandesite; Agios Ioannis Subunit; Katalakon Unit
Abbreviations: AVG = average value, MIN = minimum value, MAX = maximum value, N = number of analyses, STDEV = standard deviation.
Table 5. Magnetite, ilmenite, and titanite average formulas for the analyzed volcanic samples from Myrina, Romanou, and Katalakon units. See also Supplementary Table S2.
Table 5. Magnetite, ilmenite, and titanite average formulas for the analyzed volcanic samples from Myrina, Romanou, and Katalakon units. See also Supplementary Table S2.
MineralAverage Formulas
Magnetite[Fe2+(Fe3+)2O4]
Mag1Fe2+1.18(Fe3+1.46Ti0.18Si0.05Al0.05Mn0.03V0.02Mg0.01Ca0.01Cr0.01Zn0.01)2O4
Mag2Fe2+1.13(Fe3+1.38Ti0.21Al0.11Mg0.08Si0.03Mn0.02V0.01Zn0.01)2O4
Mag3Fe2+1.01(Fe3+1.74Ti0.08Mg0.07Al0.05V0.02Mn0.01Si0.01Zn0.01)2O4
Mag4Fe2+1.03(Fe3+1.84Al0.05Ti0.03Si0.02V0.01Mg0.01Ca0.01Zn0.01)2O4
Ilmenite[(Fe2+,Fe3+)TiO3]
Ilm1(Fe2+0.55Fe3+0.42Mn0.17Si0.03Al0.02)Ti0.75O3
Ilm2(Fe2+0.73Fe3+0.15Mg0.12Al0.05Mn0.03Si0.02V0.02)Ti0.86O3
Ilm3(Fe2+0.91Fe3+0.07Mg0.02Al0.01Mn0.01Si0.01V0.01Ca0.01)Ti0.94O3
TitaniteCaTi(SiO4)O
Ttn1Ca3.37Ti3.68Fe0.53Al0.32Mn0.09Mg0.03(SiO4)O
Table 6. Summary of magnetic susceptibility measurements for the analyzed samples from the Myrina, Katalakon, and Romanou volcanic units.
Table 6. Summary of magnetic susceptibility measurements for the analyzed samples from the Myrina, Katalakon, and Romanou volcanic units.
SampleLF Sus
(×10−8 m3/kg)		HF Sus
(×10−8 m3/kg)		Freq.Dep.%Rock Type/Volcanic Unit
LIM 011344.71338.70.45Trachydacite; Myrina Unit
LIM 0235.435.40.0Trachydacite; Myrina Unit
LIM 03216.3214.11.02Trachydacite; Myrina Unit
LIM 04112.4109.92.22Trachydacite; Myrina Unit
LIM 10754.6754.60.0Trachydacite; Myrina Unit
Average4934910.74
LIM 05904.5902.10.27Trachyandesite; Myrina Unit
LIM 13172.6171.40.7Trachyandesite; Myrina Unit
Average5395370.5
LIM 09570.6569.10.26Dacite; Myrina Unit
LIM 11657.5657.50.0Dacite; Myrina Unit
LIM 12486.8486.60.04Dacite; Myrina Unit
Average5725710.1
LIM 07502.2497.60.92Trachyandesite; Romanou Unit
LIM 081867.41865.50.10Andesite; Katalakon Unit
LIM 141186.81186.80.0Trachydacite; Katalakon Unit
LIM 15982.5979.90.26Trachydacite; Katalakon Unit
Average108510830.13
LIM 16380.4367.53.39Trachyandesite; Agios Ioannis Subunit; Katalakon Unit
Abbreviations: Freq.Dep.% = frequency-dependent susceptibility, HF Sus = high-frequency susceptibility, LF Sus = low-frequency magnetic susceptibility.
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Stergiou, C.L.; Melfos, V.; Papadopoulou, L.; Ladas, A.D.; Aidona, E. Volcanic Rocks from Western Limnos Island, Greece: Petrography, Magnetite Geochemistry, and Magnetic Susceptibility Constraints. Minerals 2025, 15, 673. https://doi.org/10.3390/min15070673

AMA Style

Stergiou CL, Melfos V, Papadopoulou L, Ladas AD, Aidona E. Volcanic Rocks from Western Limnos Island, Greece: Petrography, Magnetite Geochemistry, and Magnetic Susceptibility Constraints. Minerals. 2025; 15(7):673. https://doi.org/10.3390/min15070673

Chicago/Turabian Style

Stergiou, Christos L., Vasilios Melfos, Lambrini Papadopoulou, Anastasios Dimitrios Ladas, and Elina Aidona. 2025. "Volcanic Rocks from Western Limnos Island, Greece: Petrography, Magnetite Geochemistry, and Magnetic Susceptibility Constraints" Minerals 15, no. 7: 673. https://doi.org/10.3390/min15070673

APA Style

Stergiou, C. L., Melfos, V., Papadopoulou, L., Ladas, A. D., & Aidona, E. (2025). Volcanic Rocks from Western Limnos Island, Greece: Petrography, Magnetite Geochemistry, and Magnetic Susceptibility Constraints. Minerals, 15(7), 673. https://doi.org/10.3390/min15070673

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop