Panagiotis Voudouris

Erratum to: Re–Os isotope evidence for mixed source components in carbonate-replacement Pb–Zn–Ag deposits in the Lavrion district, Attica, Greece

The Lavrion ore district contains carbonate-replacement and vein-type Pb–Zn–Ag deposits as well as low-grade porphyry Mo, Cu–Fe skarn, and minor breccia-hosted Pb–Zn–Cu sulfide mineralization. These ore types are spatially related to a Late Miocene granodiorite intrusion (7 to 10 Ma), and various sills and dikes of mafic to felsic composition. Samples of sphalerite and pyrite from the Ilarion carbonate replacement deposit, and galena from Vein 80 (vein-type mineralization) in the Adami deposit show heterogeneous Re–Os values. These values were partially disturbed by hydrothermal activity associated with the formation of hydrothermal veins (e.g., Vein 80). A plot of initial 187Os/188Os versus 1/Oscommon ratios for pyrite and sphalerite from the Ilarion deposit form a mixing line (r2 = 0.78) between high concentration crustal-like and low concentration mantle-like end-members, or two crustal end-members one of which was more radiogenic than the other. Based on the Re–Os systematics and previously published geological and geochemical evidence, the most plausible explanation for the Re–Os isotope data is that ore-forming components were derived from mixed sources, one of which was a radiogenic crustal source from schists and carbonates probably near intrusion centers and the other, intrusive rocks in the district that are less radiogenic. Although the Re and Os concentrations of galena from Vein 80 are above background values they cannot be used as a chronometer. However, the results of the current study suggest that although pyrite, sphalerite, and galena are poor geochronometers in this ore deposit, due to partial open-system behavior, they still yield valuable information on the origin of the source rocks in the formation of bedded replacement and vein mineralization in the Lavrion district.

Fluid evolution in Tertiary magmatic-hydrothermal ore systems at the Rhodope metallogenic province, NE Greece. A review

Characterization of various fluid parameters in magmatic-hydrothermal ore mineralizationsis potentially essential for interpretation of the conditions of formation and therefore formineral exploration. Fluid inclusions can provide a useful and promising tool in the researchof the ore forming processes in these systems. This review focuses on the nature,composition and origin of magmatic-hydrothermal ore forming fluids involved in the formationof representative Tertiary ore deposits at the Rhodope metallogenic province in NEGreece. These deposits are spatially related to Tertiary magmatism in NE Greece. Casestudies are presented here and include an intrusion-hosted sheeted vein system (Kavala), aAu-rich carbonate replacement and quartz-vein mineralization (Asimotrypes), mineralizedveins in Eptadendro-Rachi and Thasos island (Kapsalina and Panagia), porphyry Cu-Mo-Re-Au deposits in Pagoni Rachi and Maronia and epithermal Au-Ag mineralizations inPerama and Loutros. Hydrothermal fluids rich in CO2 together with elevated Au and Tecontent are common and occur at the Kavala intrusion hosted sheeted vein system, at theAsimotrypes Au-rich carbonate replacement mineralization and at the Panagia (Thasos)vein system. We classify all these ore mineralizations as intrusion-related gold systems(IRGS)v. Transport and precipitation of metals including Au and Te is favoured when CO2is present. Precipitation of the ore mineralization takes place due to the immiscibility of thecarbonic and the aqueous fluids which have a magmatic origin with the contribution ofmeteoric water. Cooling of magmatic hydrothermal fluids and dilution with meteoric wateris a common cause for ore mineral formation in the vein mineralizations of Eptadendro/Rachi and Kapsalina Thasos. At the Pagoni Rachi and Maronia porphyry deposits, boilingand the high proportion of the vapour phase are the most essential fluid processes whichaffected ore formation. The epithermal veins overprinting the Pagoni Rachi and the Maroniaporphyry systems and the HS-IS epithermal system in Perama Hill and the IS epithermalmineralization in Loutros are characterized by low to moderate temperatures and lowto moderate salinities. Cooling and dilution of the ore fluids are the main process for goldprecipitation. We conclude that the different fluid parameters and microthermometric dataindicate a variety of fluid origin conditions and sources which can affect the strategy forexploration and prospecting for gold, rare and critical metals.

New porphyry — Cu±Mo occurrences in the north-eastern Aegean, Greece: Ore mineralogy and epithermal relationships

New discoveries of porphyry Cu±Mo mineralization have been made on Limnos and Lesvos islands, in areas covered by hydrothermally altered Miocene shoshonitic volcanic and subvolcanic rocks. The Fakos prospect has, may typical features of porphyry Cu±Mo deposits: K-silicate alteration, barren advanced argillic lithocap, tourmaline-sericite veins and breccias and late quartz veins rich in base and precious metals. Gold and silver are present as electrum, hessite, petzite and an unknown Ag-sulfotelluride, and are mainly enriched in the late veins. The Stipsi prospect is a molybdenum-enriched porphyry system, consisting of a quartz stockwork that contains molybdenite, bismuthinite, galena and sphalerite. Both porphyry systems evolved through several stages of magmatic-hydrothermal action with the late polymetallic quartz veins representing either epithermal style overprints.

Gold and silver mineralogy of the Lavrion deposit, Attika, Greece

Mineralogical studies in the Lavrion deposit established the widespread occurrence of silver, gold and bismuth mineral phases. Silver is present in both the Kamariza and Plaka mines in the form of various Bi-Pb-Ag bearing sulfosalts, Ag-bearing tetrahedrite and Ag-sulfosalts included in chalcopyrite and galena. Gold occurs only in the Kamariza mines, in native form closely associated with native bismuth in copper ores and in a newly discovered gersdorffite + bismuthinite + native gold assemblage enclosed in galena. This mineralogy, and especially the close relationship of bismuth and native gold in the ore, is strong evidence of magmatic-hydrothermal inputs in the system. The Lavrion deposit underwent a multistage evolution probably the result of several magmatic pulses and may have affinities to the reduced-type magmatic-hydrothermal systems.

Thermogenic travertine deposits in Thermopylae hot springs (Greece) in association with cyanobacterial microflora

The present paper deals with the investigation of abiotic and biotic influence on thermogenic travertine formation in Thermopylae hot springs, one of the largest active thermogenic travertine systems in Greece. Geological, mineralogical and microbiological data from three different types of travertines (cascades, terraces and fluvial crusts) revealed different cyanobacterial communities. Microscopic analysis of fresh and cultured material has shown that epilithic and endolithic cyanobacteria are almost the exclusive components of travertines’ photosynthetic microflora. Thirty-one (31) taxa of cyanobacteria are presented here, among them the frequently found, in such environments, Phormidium incrustatum and Aphanocapsa thermalis, as well as the taxonomically interesting diazotrophic morphotype identified as Chlorogloeopsis sp. Sampling sites I and II have similar formation conditions characterized by laminated travertines with low porosity and shrub lithotypes, with the cyanobacterium Leptolyngbya ercegovicii occupying an endolithic zone, while the upper part is occupied by colonial chroococcalean species. On the contrary, sampling site III is characterized by laminated travertine with fenestrial type porosity and absence of shrub lithotypes resulting in a completely different community of cyanobacteria.

Distribution, Microfabric, and Geochemical Characteristics of Siliceous Rocks in Central Orogenic Belt, China: Implications for a Hydrothermal Sedimentation Model

Marine siliceous rocks are widely distributed in the central orogenic belt (COB) of China and have a close connection to the geological evolution and metallogenesis. They display periodic distributions from Mesoproterozoic to Jurassic with positive peaks in the Mesoproterozoic, Cambrian—Ordovician, and Carboniferous—Permian and their deposition is enhanced by the tensional geological settings. The compressional regimes during the Jinning, Caledonian, Hercynian, Indosinian, and Yanshanian orogenies resulted in sudden descent in their distribution. The siliceous rocks of the Bafangshan-Erlihe ore deposit include authigenic quartz, syn-depositional metal sulphides, and scattered carbonate minerals. Their SiO2 content (71.08–95.30%), Ba (42.45–503.0 ppm), and ΣREE (3.28–19.75 ppm) suggest a hydrothermal sedimentation origin. As evidenced by the Al/(Al + Fe + Mn), Sc/Th, (La/Yb)N, and (La/Ce)N ratios and δCe values, the studied siliceous rocks were deposited in a marginal sea basin of a limited ocean. We suggest that the Bafangshan-Erlihe area experienced high- and low-temperature stages of hydrothermal activities. The hydrothermal sediments of the former stage include metal sulphides and silica, while the latter was mainly composed of silica. Despite the hydrothermal sedimentation of the siliceous rocks, minor terrigenous input, magmatism, and biological activity partly contributed to geochemical features deviating from the typical hydrothermal characteristics.

Structural role of tellurium in the minerals of the pearceite- polybasite group

Abstract The crystal structure of a Te-rich polybasite has been refined by means of X-ray diffraction data collected at room temperature (space group P3̅m1; R = 0.0505 for 964 observed reflections and 94 parameters; refined formula Ag14.46Cu1.54Sb1.58As0.42S9.67Te1.33). The structure comprises stacking of [(Ag,Cu)6(Sb,As)2(S,Te)7]2−A and [Ag9Cu(S,Te)2(S,Te)2]2+ B layer modules in which Sb forms isolated SbS3 pyramids, as occurs typically in sulfosalts, Cu links two S atoms in a linear coordination and Ag occupies sites with coordination ranging from quasi linear to almost tetrahedral. The silver d10 ions are found in the B layer module along two-dimensional diffusion paths and their electron densities evidenced by means of a combination of a Gram-Charlier development of the atomic displacement factors and a split model. The Te-for-S substitution occurs at the same structural sites that Se substitutes for S in selenopolybasite and the Te occupancy at one of these sites is 0.49, thus suggesting the possibility that ‘telluropolybasite’ could be found in nature.

Mineralogy of the high-sulfidation Cu-Sb-Te Mavrokoryfi prospect (western Thrace, Greece)

The high-sulfidation Mavrokoryfi prospect is located in the Petrota graben, a tectonic depression filled with calc-alkaline and shoshonic volcanic rocks of Oligocene age. Mineralization was introduced following a brecciation event of preore silicification, and is hosted within veins of massive silicification enveloped by alunitic advanced argillic alteration. Ore consists of pyrite, marcasite, famatinite, tetrahedrite (up to 15.5 wt% Ag), goldfieldite (up to 29.3 wt% Te) and traces of chalcopyrite. Al-phosphate-sulfate minerals, together with normal alunites, occur in both advanced argillic alteration and as gangue minerals, and are characterized by unusual Pb-enrichment (up to 24.7 wt% PbO in hinsdalites). Mavrokoryfi goldfieldite is among the purest in the world, with up to 3.7 apfu Te.

Lavrion smithsonites: A mineralogical and mineral chemical study of their coloration

Samples of smithsonite from the Lavrion mines are studied to determine the relationship between the colour of the mineral and the content of minor and trace elements and/or impurities. Among the trace elements found, responsible for the colouration are iron and manganese (?) (light yellow), and copper (blue, green). Copper presence is due to a ZnCO3 — CuCO3 solid solution (up to 6.3 mol % CuCO3) and not to inclusions of copper minerals. In comparison, important inclusions are greenockite aggregates (yellow) and iron hydroxides (brown). In the most complicated cases, combinations of both trace elements and inclusions influence the final colour.

Bi-sulphotellurides associated with Pb – Bi – (Sb ± Ag, Cu, Fe) sulphosalts: an example from the Stan Terg deposit in Kosovo

Abstract New mineralogical and mineral-chemical data from the Stan Terg deposit, Kosovo, revealed the presence of abundant Bi-sulphotellurides associated with Bi- and Sb-sulphosalts and galena in pyrite–pyrrhotite-rich skarn-free ore bodies (ores without skarn minerals). The Bi-bearing association comprises Bi-sulphotellurides (joséite-A, joséite-B, unnamed phase A with a chemical formula close to (Bi,Pb)2(TeS)2, unnamed phase B with a chemical composition close to (Bi,Pb)2.5Te1.5S1.5), ikunolite, cosalite, Sb-lillianite, members of the kobellite series and Bi-jamesonite. Compositional trends of the Bi-sulphotellurides suggest lattice-scale incorporation of Bi–(Pb)-rich module and/or admixture with submicroscopic PbS layers in modulated structures, or complicated Bi–Te substitution. Cosalite is characterized by high Sb (max. 3.94 apfu), and low Cu and Ag (up to 0.72 apfu of Cu+Ag). Jamesonite from this mineralization has elevated Bi content, from 0.85 to 2.30 apfu. The negligible content of Au and Ag in the Bi-sulphotellurides, the low content of Ag in Bi-sulphosalts, together with the lack of Au–Ag bearing phases in the mineralization, indicate either ore deposition from fluid(s) depleted in precious metals, or physico-chemical conditions of ore formation preventing Au and Ag precipitation at the deposit site. The temperature of initial mineralization may have exceeded 400 °C as suggested by the lamellar exsolution textures observed in lillianite, which indicate breakdown textures from decomposition of high-temperature initial crystals. Non-stoichiometric phases among the Bi-sulphosalts and sulphotellurides studied at Stan Terg reflect modulated growth processes in a metasomatic environment.