New occurrences of watanabeite, colusite, "arsenosulvanite" and "Cu-excess" tetrahedrite-tennantite at the Pef ka high-sulfidation epithermal deposit, northeastern Greece

The high-to intermediate-sulfidation epithermal Cu-Au-Ag-Te deposit at Pefka in northeastern Greece reveals an extraordinary and rare polymetallic ore-mineralogy including several Cu-, Bi-, Sn-, Ge-, V-, As-, Hg-, Au- and Ag-bearing sulfides, sulfosalts, tellurides, native elements and the rare Cu-sulfosalts and chalcogeno-salts watanabeite, colusite, "arsenosuvanite" and "Cu-excess" tetrahedrite-tennantite. Paragenetic sequences suggest deposition of an earlier high-sulfidation metallic ore assemblage (e.g. enargite/luzonite, goldfieldite and native gold), followed by an intermediate-sulfidation ore assemblage (composed of tetrahedrite-tennantite and various tellurides). Watanabeite, colusite and "arsenosulvanite" are intergrown with enargite/luzonite and native copper, thus clearly belonging to the high-sulfidation stage of ore deposition at Pefka. "Cu-excess" tetrahedrite-tennantite postdates enargite/luzonite, thus suggesting deposition at the transition from high-towards intermediate-sulfidation fluid states. Of all known occurrences worldwide, the As:Sb ratio of the Pefka watanabeite is the closest to the type material from the Teine mine, Hokkaido. An extremely Sb-rich analog to watanabeite (with up to 1.4 apfu Sb) detected during this study at Pefka mine, seems to fill the gap within the solid solution between the As-rich member and an unnamed Sb-dominant phase. Colusite at Pefka ranges in composition from colusite sensu stricto to stibiocolusite. In comparison to colusite, "arsenosulvanite" is Sn-free or relatively Sn-poor and moderately anisotropic. The fahlore-group minerals at Pefka reveal an excess in Cu-contents of up to 11.73 and 11.03 apfu for tennantite and tetrahedrite, respectively. Thus, our results suggest that the term "Cu-excess" can be applied for the whole tetrahedrite-tennantite solid solution series. We also detected "Cu-excess" compositions for Zn-bearing, Fe-free tennantite that has not been previously reported. We suggest a continuous evolution of the Pefka hydrothermal system from initial high-temperature (>280°C) high-sulfidation, oxidizing conditions, towards lower-temperature and lower-sulfidation, more reduced conditions with time. This evolution is also reflected in the paragenetic sequence of the fahlore group minerals (e.g. early extreme "Cu-excess" tennantite and tetrahedrite with > 11 apfu Cu was followed by moderate to weak "Cu-excess"-, and finally by fully substituted tennantite and tetrahedrite), being the result of decreasing copper content in the hydrothermal system. The abundance of tellurides and native tellurium in the mineralization is compatible with direct deposition of metals from the vapor phase of a buried porphyry body. © 2015 E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Germany

Chemical composition and varieties of fahlore-group minerals from Oligocene mineralization in the Rhodope area, Southern Bulgaria and Northern Greece

Fahlore-group minerals in Oligocene magmatic-hydrothermal deposits from the central and eastern Rhodope area, Bulgaria and Greece (e.g. porphyry-epithermal systems at Pagoni Rachi, Maronia and Kassiteres-Sapes, polymetallic epithermal high- and intermediate-sulfidation veins at Kirki, Perama Hill, Mavrokoryfi, Pefka, Zvezdel-Pcheloyad and Madzharovo, skarn-carbonate replacement deposits at Laki, Davidkovo, Madan, Enyovche and intrusion-related deposits at Kimmeria), cover the whole range of the tetrahedrite-tennantite solid solution series and are dominated by zincian and ferroan varieties reflecting deposition from Zn-(and Fe)-rich fluids. The majority of the studied fahlores are “normal” fully-substituted with Cu (+Ag) close to 10 apfu. However, high-sulfidation epithermal deposits in Greece contain “Cu-excess” tetrahedrite-tennantite; those with extreme high Cu-excess > Fe + Zn occur in transitional high- to intermediate-sulfidation systems, whereas low “Cu-excess” tetrahedrite-tennantite with Zn > Cu-excess + Fe and Fe > Cu-excess + Zn are part of tellurides-bearing intermediate-sulfidation assemblages. The epithermal St. Demetrios and Pefka deposits display the most Cu-rich tetrahedrites (11.039 apfu Cu) and tennantite (11.784 apfu Cu) worldwide. Although Ag substitutes for Cu in the structure of Ag-rich tetrahedrite in several deposits, freibergite with 6.800 apfu Ag occurs only at Mavrokoryfi; in particular, the cadmian freibergite at Mavrokoryfi is the second finding of this variety worldwide. Tellurium-bearing fahlore varieties occur in association with enargite/luzonite and native gold in high-sulfidation ore assemblages. Tetravalent tellurium substitutes for trivalent As and Sb in goldfieldite and Te-rich tennantite and tetrahedrite at Mavrokoryfi, Perama Hill, St. Demetrios and Pefka deposits. Goldfieldite at Mavrokoryfi and Perama Hill is remarkably Te-rich (up to 3.766 apfu and 3.711 apfu Te, respectively), with total metal content of 10.591 apfu and are the closest natural occurrence to the theoretical synthetic endmember Cu10Te4S13. The telluride-bearing fahlores in several epithermal deposits in Greece do not represent decomposition products of early goldfieldite. They are possibly the result of a new influx of Te-rich magmatic volatiles in the system. Decreasing Te (and Cu)-content in tetrahedrite-tennantite solid solution series reflects an evolution from initial high-T, high-sulfidation, oxidizing conditions, towards lower-T and lower-sulfidation, more reduced conditions with time. Fahlores, although they are minor constituents in the studied mineralization types, are carriers of Ag (and Au in goldfieldite) and may be used as an exploration tool, since they are closely associated with either native gold, gold-silver tellurides or Ag-sulfosalts. © 2015, Springer-Verlag Wien

Record and provenance of Pleistocene volcaniclastic turbidites from the central Lesser Antilles (IODP Expedition 340, Site U1398B)

International audiencePorphyritic lava and mineral fragments include plagioclase, diopside, augite and enstatite, as well as magnesio-hornblende and ferri-tschermakite. Geothermobarometry based on clinopyroxene and amphibole reveal the dominant role of upper crustal magma reservoirs. Ferri-tschermakite from 93 and 167.5 mbsf (~410 and 856 ka, respectively) records contributions from lower crustal, hot magma reservoirs. These temperature estimates are supported by Ti-in-zircon data. O-isotope ratios and trace elements in zircon reflect magmatic activity typical for an evolved island arc system. The bathymetry of the Grenada basin, the composition of lava clasts and minerals, scarcity of altered lava fragments, the narrow maximum age population of detrital zircon, and the O-isotope and trace element data on zircon suggest that the majority of U1398B volcaniclastic turbidites originated from the island of Dominica. The thick volcaniclastic units are most likely related to major eruption periods of andesitic magma that ascended from crustal reservoirs. Debris avalanche-related processes seem to be less important in U1398B at ≤ 170 mbsf. Mineral chemistry and O-isotope data obtained from plagioclase, pyroxene, amphibole, zircon and glass, separated from deep marine volcaniclastic turbidites, provide a chronostratigraphic frame for the sedimentary succession, and helps to complete knowledge about the volcanic and magmatic evolution of the neighboring volcanic islands. While this is documented here for the well-constrained Pleistocene history of the central Lesser Antilles, the applied methods may also be used to characterize ancient marine volcaniclastic mass flow deposits and to reconstruct their volcanic source areas

Porphyry and epithermal deposits in Greece: An overview, new discoveries, and mineralogical constraints on their genesis

Greece hosts a variety of magmatic-hydrothermal ore deposits/prospects with porphyry- and epithermal styles playing a major role in its total gold endowment. These deposit types are mainly clustered in two areas, the Rhodope- and Attico-Cycladic massifs, and formed from about 33 Ma to the Pleistocene, as a result of back-arc extension in the Aegean Sea, metamorphic core complex formation, and contemporaneous post-subduction and arc magmatism. In the Serbo-Macedonian massif, porphyry Cu-Au deposits include Skouries, Fisoka, Tsikara, Vathi and Gerakario. Causative intrusives are Oligocene to Miocene granodiorites to monzonites. Gold and PGE mineralization is associated with potassic alteration of the intrusives. In the eastern Rhodope massif and the NE Aegean islands, porphyry prospects occur at Pagoni Rachi, Konos Hill, Myli, Melitena (west Thrace), Fakos, Sardes, and Kaspakas (Limnos island) and Stypsi (Lesvos island). Mineralization is associated with Oligocene to Miocene subvolcanics of calc-alkaline to shoshonitic affinity. Feature of these prospects, which they share in common with several porphyry Au-only systems, is their shallow depth of emplacement, the presence of potassic/sodic-calcic and/or phyllic alteration, a strong epithermal overprint, their low Cu content, an extreme Re-enrichment, the multistage introduction of Au, the presence of banded quartz veinlets, and the local presence of tourmaline. New discoveries of porphyry-style mineralization at King Arthur, St. Philippos and Aisymi, increases the gold potential in west Thrace. High-intermediate sulfidation epithermal Au-Ag polymetallic deposits/prospects overprint and/or occur laterally from porphyry-style mineralization, where they are spatially associated with lithocaps of advanced argillic alteration. High-intermediate sulfidation Au-Ag epithermal mineralization at Perama Hill, Mavrokoryfi and Pefka in west Thrace, and at Pterounda, Mesotopos and Megala Therma on Lesvos island is controlled by steeply-dipping extensional faults within volcanic rocks, without any obvious genetic relationship to spatially-related porphyry-style mineralization. Polymetallic epithermal deposits and prospects contain critical and energy critical metals (e.g., Te, Se, Bi, Sb, In, Ge and Ga), which may be considered as by-products. In the Attico-Cycladic area, porphyry Mo-W mineralization occurs as sheeted quartz veins and stockworks cutting a potassic- to sericitic-altered Miocene granodiorite stock in the Lavrion district. Bonanza grade Au- and/or Ag-rich veins with epithermal affinities crosscut metamorphic rocks at Lavrion, and on Syros, Tinos, Antiparos and Anafi islands. Milos island is characterized by shallow submarine volcanic-hosted IS-HS epithermal Au-Ag-Te and base metal deposits. Antimony-As-Ag-Au deposits/prospects on Chios, Samos and Kos islands in the eastern Aegean Sea, indicate the potential for Carlin-style mineralization in Greece. Several factors played a role to the metal endowment of the Aegean porphyry-epithermal systems: magma fertility in the source regions, depth of emplacement of causative intrusives, relative contribution of mantle versus crustal material, redox state of subduction-related magmas, and physico-chemical fluid conditions at the site of ore deposition. © 2019 Elsevier B.V

Porphyry and epithermal deposits in Greece: An overview, new discoveries, and mineralogical constraints on their genesis

Greece hosts a variety of magmatic-hydrothermal ore deposits/prospects with porphyry- and epithermal styles playing a major role in its total gold endowment. These deposit types are mainly clustered in two areas, the Rhodope- and Attico-Cycladic massifs, and formed from about 33 Ma to the Pleistocene, as a result of back-arc extension in the Aegean Sea, metamorphic core complex formation, and contemporaneous post subduction and arc magmatism. In the Serbo-Macedonian massif, porphyry Cu-Au deposits include Skouries, Fisoka, Tsikara, Vathi and Gerakario. Causative intrusives are Oligocene to Miocene granodiorites to monzonites. Gold and PGE mineralization is associated with potassic alteration of the intrusives. In the eastern Rhodope massif and the NE Aegean islands, porphyry prospects occur at Pagoni Rachi, Konos Hill, Myli, Melitena (west Thrace), Fakos, Sardes, and Kaspakas (Limnos island) and Stypsi (Lesvos island). Mineralization is associated with Oligocene to Miocene subvolcanics of calc-alkaline to shoshonitic affinity. Feature of these prospects, which they share in common with several porphyry Au-only systems, is their shallow depth of emplacement, the presence of potassic/ sodic-calcic and/or phyllic alteration, a strong epithermal overprint, their low Cu content, an extreme Reenrichment, the multistage introduction of Au, the presence of banded quartz veinlets, and the local presence of tourmaline. New discoveries of porphyry-style mineralization at King Arthur, St. Philippos and Aisymi, increases the gold potential in west Thrace. High-intermediate sulfidation epithermal Au-Ag polymetallic deposits/prospects overprint and/or occur laterally from porphyry-style mineralization, where they are spatially associated with lithocaps of advanced argillic alteration. High-intermediate sulfidation Au-Ag epithermal mineralization at Perama Hill, Mavrokoryfi and Pefka in west Thrace, and at Pterounda, Mesotopos and Megala Therma on Lesvos island is controlled by steeply-dipping extensional faults within volcanic rocks, without any obvious genetic relationship to spatially-related porphyry-style mineralization. Polymetallic epithermal deposits and prospects contain critical and energy critical metals (e.g., Te, Se, Bi, Sb, In, Ge and Ga), which may be considered as byproducts. In the Attico-Cycladic area, porphyry Mo-W mineralization occurs as sheeted quartz veins and stockworks cutting a potassic- to sericitic-altered Miocene granodiorite stock in the Lavrion district. Bonanza grade Au- and/or Ag-rich veins with epithermal affinities crosscut metamorphic rocks at Lavrion, and on Syros, Tinos, Antiparos and Anafi islands. Milos island is characterized by shallow submarine volcanic-hosted IS-HS epithermal Au-Ag-Te and base metal deposits. Antimony-As-Ag-Au deposits/prospects on Chios, Samos and Kos islands in the eastern Aegean Sea, indicate the potential for Carlin-style mineralization in Greece. Several factors played a role to the metal endowment of the Aegean porphyry-epithermal systems: magma fertility in the source regions, depth of emplacement of causative intrusives, relative contribution of mantle versus crustal material, redox state of subduction-related magmas, and physico-chemical fluid conditions at the site of ore deposition