The AUTh SEG Student Chapter at the world-class Lavrion polymetallic ore deposit,

Attic-Cycladic ore belt, SE Attica, Greece

Fieldtrip report

October, 9-11 2020

Submitted by:

Eftychia Peristeridou &

Christos Stergiou

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Fieldtrip participants The Society of Economic Geologists (SEG) Student Chapter of Aristotle University of

Thessaloniki (AUTH) organized on October 9-11, 2020, a field trip to the world-class Lavrion polymetallic deposit in SE Attica. The field- trip was financially supported by SEG through the Foundation Round I 2020 from the Stewart R. Wallace Fund. Additional funds were available from the participation of our chapter at the 1st AUTH Flea Market in February 2020. The 16 participants, undergraduate and graduate students, were guided by the Academic Advisor, Associate Professor Vasilios Melfos, with Dr. Christos Emmanouilidis and Dr. Stavros Oikonomidis. All participants (Table 1) are affiliated to the Department of Mineralogy-Petrology-Economic Geology, School of Geology, AUTH. The entrance into the underground mine was possible under the guidance and supervision of Mr. Hercules Katsaros and Mr. Vasilios Stergiou citizens of Lavrion city, who are experienced in exploring the ancient and modern underground galleries of the area. Their assistance in research of several groups of mineralogists has resulted in the discovery of several new minerals (Rieck et al., 2019; 2020). Table 1. Fieldtrip participants

Name SEG Member Academic Position Vasilios Melfos Academic Advisor Associate Professor

Christos Emmanouilidis - Teaching and Technical Personnel

Stavros Oikonomidis - Teaching and Technical Personnel

Eftychia Peristeridou President of SC* MSc student Christos Stergiou Vice President of SC Ph.D. candidate Dimitra Perperi Secretary of SC BSc student Eirini Margiola Treasurer of SC BSc student Thelxiopi Antonia Kimpizi

Other Exec. Member of SC

BSc student

Dimitris Baliakas SEG student**, SC member

BSc student

Eleni Pegioudi SEG student, SC member BSc student Fivos Kiniklis SEG student, SC member MSc student Spiros Fragkou SEG student, SC member BSc student Theodoros Tsigkas SEG student, SC member BSc student Christina Mitiglaki SC member Ph.D. candidate Katerina Panora SC member BSc student Stefania Andriopoulou SC member MSc student

*Student Chapter, **Student member of the SEG

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Introduction Lavrion is located in SE Attica and marks the westernmost extension of the Cenozoic

Attic-Cycladic ore belt, which is part of the Western Tethyan metallogenic belt (Melfos and Voudouris, 2017; Fig. 1A). Lavrion hosts numerous mineralization styles enriched in basic metal commodities, such as Fe, Cu, Pb, Zn, as well as in rare and critical metals (e.g. Au, Ag, Mo, W, Te, Sb, Bi, Ge, In and Sn). It was a mining district producing pure silver during the Classical period and the latest exploitation ended in the early 1970s (Conophagos, 1980).

The Lavrion ore district consists of a variety of ore styles, including porphyry, skarn, breccia, carbonate-replacement, and vein styles (Voudouris, 2005; Voudouris et al., 2008a; b; Bonsall et al., 2011; Fig. 1Β). In addition, supergene oxidation of the primary mineralization has resulted in the formation of a wide variety of common and rare secondary minerals (Zaimis, 2010).

Figure 1. A. Schematic map of the western part of the Attico-Cycladic metamorphic core complex showing the major detachment faults and the main mineralization types. B. Geologic map of the eastern Lavrion Peninsula showing the main tectonic units, the detachment faults and the main type of mineralizations. The locations visited during the fieldtrip are highlighted: 1. Vein 80 mine, 2. Plaka

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porphyry system, 3. Plaka carbonate replacement mineralization 4. 3rd Kilometer mine, 5. Thorikos area (modified after Scheffer et al., 2016; 2019).  

The student chapter visited the “Filoni 80” vein style mineralization in the underground Plaka mine, the Plaka porphyry system and the skarn deposit, the “3rd-kilometer” carbonate-replacement Pb-Zn-Ag deposit, and the ancient mining and metallurgical site of Thorikos. The fieldtrip was a great opportunity for the participants to examine four different magmatic-hydrothermal ore styles, to get familiar with the geological and mineralogical setting, and to combine this information with the plentiful historical and cultural data of the region. Lavrion is considered as an inexhaustible natural mineral and chemical “laboratory”, where more than 700 species of minerals have been discovered (Zaimis, 2010).  

Activities Program Adhering to the Covid-19 personal hygiene measures, the fieldtrip started on Friday,

October 9, 2020 and after driving 6 hours from Thessaloniki, we arrived at the city of Lavrion. On Friday afternoon we visited the Mineralogical Museum, where approximately 700 samples from 115 different mineral species are exhibited (https://emel.gr/wp-content/uploads/2019/12/en_oryktologiko_mouseio.pdf). The rare and beautiful specimens (e.g. annabergites, serpierites, spangolites, laventulanites), classify the area not only a world-class deposit but a worldwide mineralogical spectacle.

During the second day Mr. Hercules Katsaros and Mr. Vasilios Stergiou joined the group and guided us into the abandoned underground mine “Filoni 80” of Plaka. The entrance in this gallery is permitted by the authorities and is safe. All the participants were equipped with the necessary safety gear and a short safety induction preceded the entrance to the mine.

The “Filoni 80” mine was opened in the mid-1950s along a major Pb-As-Sb-Cu-Ag-rich banded vein that crosscuts the local lithology consisting of hornfels and mylonitic and cataclastic marbles (Voudouris et al., 2008a). The vein is up to 2 m thick and up to 1 km long with an ESE-WNW direction that dips shallowly southwards, parallel to the West Cycladic detachment system (Fig. 2A, B). According to Voudouris et al. (2008a) and Scheffer et al. (2019) the ore mineralization started with the early deposition of pyrrhotite followed by arsenopyrite, löollingite, pyrite, marcasite. It continued with the formation of a Cu-Bi bearing assemblage including lillianite homologues, pyrargyrite, chalcopyrite, Bi-bearing tetrahedritetennantite, bournonite, and lead sulfo-antimonides. During the final stages of the ore forming processes galena, sphalerite, and native arsenic were deposited. Galena contains small inclusions of silver sulphosalts, such as argentian tetrahedrite and miargyrite. The main gangue minerals are quartz, siderite, fluorite, and calcite.

In the underground mine, the group had the chance to examine the textures of the mineralization and the relation with the metamorphic rocks and the detachment fault. The main ore body is developed along the footwall of the large detachment fault, which forms a brecciated zone, up to 3 m in thickness. Crossing the gallery, the group walked through the well-exposed detachment fault zone and got informed about the role of the regional tectonics in Lavrion metallogeny during Miocene (Fig. 3).

Later that day, the group visited the Plaka porphyry Mo±W system associated with a late Miocene granodiorite. The granodiorite has been extensively altered by hydrothermal fluids, producing three styles of alteration: potassic, sodic-calcic and sericitic, locally with silicifications (Voudouris et al., 2008a, 2019). Numerous sheeted quartz veins and stockworks of A- and B-type veins are linked to the potassic alteration. The mineralization consists of pyrite, molybdenite, chalcopyrite, pyrrhotite and minor scheelite. The participants collected hand specimens from each alteration zone and examined their characteristic minerals. The sodic-calcic alteration is characterized by oligoclase/andesine, diopside,

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actinolite, titanite with minor magnetite, quartz and apatite. Hydrothermal biotite, K-feldspar, quartz, and magnetite constitute the potassic alteration, while sericite, pyrite and quartz characterize the sericitic alteration (Voudouris et al., 2019).

Figure 2. Vein type mineralization in “Filoni 80” mine. A. Banded vein mineralization, B. Pb-Zn-Ag ore below the detachment fault (photo courtesy E. Peristeridou).

Figure 3. The fieldtrip participants “holding” the hanging wall surface of the well-exposed West Cycladic detachment fault (photo courtesy: H. Katsaros).  

The next stop was at the carbonate replacement mineralization in the village of Plaka. The mineralization resembles the skarn style, and consists of pyrrhotite followed by pyrite, sphalerite, galena and chalcopyrite (Voudouris et al., 2008a, b). Magnetite, hematite and

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marcasite are decomposition products of pyrrhotite, while calcite is the main gangue mineral. The mineralization forms strata-bound lenses (mantos) and partly crosscutting structures (chimneys) with respect to the layering in the host marble (Voudouris et al., 2008b; Fig. 4).

Figure 4. The carbonate replacement mineralization at the Plaka village. The mineralized hydrothermal fluids dissolved and replaced the marble forming chimneys within the marble and mantos along the marble-schist contact (photo courtesy: C. Stergiou).

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The day ended with our visit to the carbonate replacement Pb-Zn-Ag mineralization at

the “3rd-kilometer” site (Voudouris et al., 2008a). The numerous ancient galleries around highlight the economic importance of the area in the Classical period (Conophagos, 1980). The mineralization consists of Pb-Ni-Au-Bi association with galena-gersdorffite-gold veins that crosscut the brecciated upper marble close to the detachment. Several arsenides (rammelsbergite, nickeline and safflorite) and inclusions of vaesite, millerite and ullmannite are also reported (Pekov et al., 2016; Fig. 5).

 Figure 5. The fieldtrip participants in an exploitation cavern at the skarn-free replacement Pb-Zn-Ag mineralization at the “3rd-kilometer” site (photo courtesy: V. Melfos).

During the third day of the fieldtrip we visited the Thorikos area, an important ancient mining and metallurgical site that is related to the dawn of the Classical Greek era (Scheffer et al., 2017). The Thorikos Pb-Zn-Fe-Cu-Ag polymetallic vein deposit consists of a 60 cm to 1 m thick, and 800 m long vein parallel to the detachment fault. A replacement style mineralization occurs within the mylonitic marbles with chimney and manto ore styles (Scheffer et al., 2017; 2019).

The first indications of the mining activity in the area date back to the 4th to 3rd millennium BCE and are traced at the neighboring Velantouri Hill. However, Thorikos was a significant metallurgical center in Classical antiquity. The remnants of the ancient hydro-mechanical washers used for the ore benefaction still survive and have been extensively restored (Conophagos, 1980; Fig. 5). The oldest known ancient theater globally is found in Thorikos, and dates at the end of the Archaic era, between 525 and 480 BC (Docter & Webster, 2018; Fig. 5).

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Figure 5. The ancient theater of Thorikos at the background, and the restored ancient hydro-mechanical washer (photo courtesy: E. Peristeridou).  

Acknowledgments AUTh SEG Student Chapter is grateful to the Society of Economic Geologists for the

funds granted through the SEG Foundation Round I 2020 Student Chapter Funding from the Stewart R. Wallace Fund. More information regarding budget allocation and relative expenses can be found in the attached file “Expenses report”. Finally, we would like to thank Mr. Hercules Katsaros and Mr. Vasilis Stergiou who assisted us in organizing this fieldtrip.

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References Bonsall, T.A., Spry, P.G., Voudouris, P.C., Tombros, S., Seymour, K.S., Melfos, V. (2011)

The geochemistry of carbonate-replacement Pb-Zn-Ag mineralization in the Lavrion district, Attica, Greece: Fluid inclusion, stable isotope, and rare earth element studies. Economic Geology, 106(4):619-651.

Conophagos, C. (1980). The ancient Lavrion and the Greek techniques for silver production. Hellados Publ, Athens, 458.

Docter, R. F., & Webster, M. (Eds.). (2018). Exploring Thorikos. Ghent University, Department of Archaeology.

Pekov, I. V., Chukanov, N. V., Varlamov, D. A., Belakovskiy, D. I., Turchkova, A. G., Voudouris, P., Katerinopoulos, A., Magganas, A. (2016). Nickeltsumcorite, Pb(Ni,Fe3+)2(AsO4)2(H2O,OH)2, a new tsumcorite-group mineral from Lavrion, Greece. Mineralogical Magazine, 80(02);337–346.

Rieck, B., Giester, G., Lengauer, C., Topa, D. (2019) Stergiouite, IMA 2018-051a. In: Miyawaki, R. et al. (eds.) IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) Newsletter 47. European Journal of Mineralogy, 31:199–204.

Rieck, B., Giester, G., Lengauer, C., Nasdala, L. (2020) Katsarosite, IMA 2020-014. In: Miyawaki, R. et al. (eds.) IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) Newsletter, 57. European Journal of Mineralogy, 32:495-499.

Scheffer, C., Tarantola, A., Vanderhaeghe, O., Voudouris, P., Rigaudier, T., Photiades, A., Moris, D., Alloucherie, A. (2017) The Lavrion Pb-Zn-Fe-Cu-Ag detachment-related district (Attica, Greece): Structural control on hydrothermal flow and element transfer-deposition. Tectonophysics, 717:607-627.

Scheffer, C., Tarantola, A., Vanderhaeghe, O., Voudouris, P., Spry, P. G., Rigaudier, T., Photiades, A. (2019) The Lavrion Pb-Zn-Ag–rich vein and breccia detachment-related deposits (Greece): Involvement of evaporated seawater and meteoric fluids during postorogenic exhumation. Economic Geology, 114(7):1415-1442.

Scheffer, C., Vanderhaeghe, O., Lanari, P., Tarantola, A., Ponthus, L., Photiades, A., France, L. (2016) Syn-to post-orogenic exhumation of metamorphic nappes: Structure and thermobarometry of the western Attic-Cycladic metamorphic complex (Lavrion, Greece). Journal of Geodynamics, 96:174-193.

Voudouris, P. (2005) Gold and silver mineralogy of the Lavrion deposit, Attika, Greece. In: Mao, L., and Bierlein, F.P., (eds.) Mineral deposit research: meeting the global challenge, 1089-1092. Springer-Verlag Berlin Heidelberg.

Voudouris, P., Mavrogonatos, C., Spry, P.G., Baker, T., Melfos, V., Klemd, R., Haase, K., Repstock, A., Djiba, A., Bismayer, U., Tarantola, A., Scheffer, C., Moritz, R., Kouzmanov, K., Alfieris, D., Papavassiliou, K., Schaarschmidt, A., Galanopoulos, E., Galanos, E., Kołodziejczyk, J., Stergiou, C., Melfou, M. (2019) Porphyry and epithermal deposits in Greece: An overview, new discoveries, and mineralogical constraints on their genesis. Ore Geology Reviews, 107:654-691.

Voudouris, P., Melfos, V., Spry, P. G., Bonsall, T., Tarkian, M., Economou-Eliopoulos, M. (2008a) Mineralogical and fluid inclusion constraints on the evolution of the Plaka intrusion-related ore system, Lavrion, Greece. Mineralogy and Petrology, 93(1-2):79-110.

Voudouris, P., Melfos, V., Spry, P. G., Bonsall, T. A., Tarkian, M., Solomos, C. (2008b) Carbonate-replacement Pb–Zn–Ag±Au mineralization in the Kamariza area, Lavrion, Greece: Mineralogy and thermochemical conditions of formation. Mineralogy and Petrology, 94(1-2):85.

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Zaimis S. (2010). Mineralogical study of the Lavrion minerals from the Museum of Mineralogy and Petrology of the Aristotle University of Thessaloniki. Unpublished Diploma Thesis, Aristotle University of Thessaloniki, p. 80.