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Fluid conditions of shallow marine hydrothermal vent sites (200 mbsl) and mid-ocean ridge-related environments (>2000 mbsl). At Calypso Vents in the Bay of Plenty and Paleochori Bay at the coast of Milos Island, fluids with temperatures

Compiled data show the age progression of magmatic centers along the two approximately linear profiles from NE Greece and NW Turkey to the South Aegean Volcanic Arc. The age progression reveals the southwestward migration of arc magmatic activity from Oligocene to present, perpendicular to the Hellenic Trench. This is in accordance with the migration of the Aegean subduction zone due to the collision of oceanic and continental blocks, trench retreat, mantle flow, and coeval extension. We suggest that the subduction of large volumes of sediments and their contribution to the sub-arc magma source controlled the composition of calc-alkaline to high-K calc-alkaline and shoshonitic arc magmas during the past 30 Ma. The magma geochemistry and the approximately linear age-progressive migration of magmatic activity suggest focused ascent of mixed material from the subducted slab into the mantle wedge, most likely in the form of melange diapirs. Geochemical data along the profile reveals increasing Sr and decreasing Nd isotopes during Upper Miocene in agreement with the ongoing subduction of continental blocks, low subduction rates, and development of an accretionary wedge. The different K-rich arc magmas reflect the variable subduction of sediments, whereas crustal assimilation often plays a minor role. Magmas with variable Sr-87/Sr-86, P/Nd, and Ba/La indicate a variable contribution of clastic, phosphate-bearing, and barite-bearing sediments. Low-degree partial melting in sediment-dominated melange diapirs causes the formation of shoshonitic magmas with high Sr and P2O5 contents and high La/Yb in the northern Aegean.

The Maronia Cu-Mo ± Re ± Au deposit is spatially related to a microgranite porphyry that intruded an Oligocene monzonite along the Mesozoic Circum-Rhodope belt in Thrace, NE Greece. The magmatic rocks and associated metallic mineralization show plastic and cataclastic features at the south-eastern margin of the deposit that implies emplacement at the ductile-brittle transition, adjacent to a shear zone at the footwall of the Maronia detachment fault. The conversion from ductile to brittle deformation caused a rapid upward magmatic fluid flow and increased the volume of water that interacted with the host rocks through high permeable zones, which produced extensive zones of potassic and sodic-calcic alteration. Potassic alteration is characterized by secondary biotite + K-feldspar (orthoclase) + magnetite + rutile + quartz ± apatite and commonly contains sulfides (pyrite, chalcopyrite, pyrrhotite). Sodic-calcic alteration consists of actinolite + sodic-calcic plagioclase (albite/oligoclase/andesine) + titanite + magnetite + chlorite + quartz ± calcite ± epidote-allanite. The high-oxidation state of the magmas and the hydrothermal fluid circulation were responsible for the metal and sulfur enrichments of the aqueous fluid phase, an increase in O2 gas content, the breakdown of the magmatic silicates and the production of the extensive potassic and sodic-calcic alterations. Brittle deformation also promoted the rapid upward fluid flow and caused interactions with the surrounding host rocks along the high temperature M-, EB-, A-and B-type veins. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.

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.

Magnetite is a common accessory phase in various types of ore deposits. Its trace element content has proven to have critical implications regarding petrogenesis and as guides in the exploration for ore deposits in general. In this study we use LA-ICP-MS (laser ablation-inductively coupled plasma-mass spectrometry) analyses of trace elements to chemically characterize magnetite from the Pagoni Rachi Cu–Mo–Re–Au porphyry-style prospect, Thrace, northern Greece. Igneous magnetite mostly occurs as euhedral grains, which are commonly replaced by hematite in fresh to propylitic-altered granodiorite porphyry, whereas, hydrothermal magnetite forms narrow veinlets or is disseminated in sodic/potassic-calcic altered (albite + K-feldspar + actinolite + biotite + chlorite) granodiorite porphyry. Magnetite is commonly associated with chalcopyrite and pyrite and locally exhibits martitization. Laser ablation ICP-MS analyses of hydrothermal magnetite yielded elevated concentrations in several trace elements (e.g., V, Pb, W, Mo, Ta, Zn, Cu, and Nb) whereas Ti, Cr, Ni, and Sn display higher concentration in its magmatic counterpart. A noteworthy enrichment in Mo, Pb, and Zn is an unusual feature of hydrothermal magnetite from Pagoni Rachi. High Si, Al, and Ca values in a few analyses of hydrothermal magnetite imply the presence of submicroscopic or nano-inclusions (e.g., chlorite, and titanite). The trace element patterns of the hydrothermal magnetite and especially the decrease in its Ti content reflect an evolution from the magmatic towards the hydrothermal conditions under decreasing temperatures, which is consistent with findings from analogous porphyry-style deposits elsewhere. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.

The UG2 chromitite of the Bushveld Complex in South Africa contains the world’s largest resources of platinum-group elements (PGE). However, only limited work has been conducted on the distribution of PGE and platinum-group minerals (PGM) within the UG2. In the present study, earlier work on the PGE distribution within the Merensky Reef (Osbahr et al. 2013) is followed up and extended to the UG2. Two drill cores of the UG2 chromitite from the eastern and western Bushveld Complex were studied by whole rock analysis, ore microscopy and SEM/MLA. The PGE, Au and Ag contents of pentlandite, pyrrhotite and chalcopyrite were determined using LA-ICP-MS analysis. Whole-rock analyses of the two profiles reveal highest Pd and Pt concentrations at the top and at the base of the UG2 main seam. Sulfides mostly occur as aggregates of pentlandite, chalcopyrite and rare pyrrhotite and pyrite or as individual grains associated mostly with chromite grains. In-situ LA-ICP-MS analyses reveal that pentlandite carries distinctly elevated PGE contents. In contrast, pyrrhotite and chalcopyrite contain very low PGE concentrations. Pentlandite shows average maximum values of 350-1000 ppm Pd, 200 ppm Rh, 130-175 ppm Ru, 20 ppm Os and 150 ppm Ir and therefore, is the principal host of Pd and Rh in the studied ores of the UG2. Mass balance calculations were conducted for samples representing the UG2 main seam of the drill core DT46, eastern Bushveld. Accordingly, pentlandite constantly hosts elevated contents of the whole rock Pd (up to 55 %) and Rh (up to 46 %), and erratic contents of Os (up to 50 %), Ir (2 to 17 %) and Ru (1 - 39 %). PGM investigations support these mass balance results, most of the PGM are Pt-dominant PGM like braggite/cooperite and Pt-Fe alloys or laurite, (carrying elevated concentrations of Os and Ir). Palladium and Rh-bearing PGM are rare. PGE concentrations and their distribution in BMS in the UG2 largely resemble that of the Merensky Reef, as most of the Pd and Rh are incorporated in pentlandite whereas pyrrhotite, chalcopyrite and pyrite are almost devoid of PGE. Consequently, similar mineralization processes are responsible for the PGE enrichment in the UG2 and in the Merensky Reef.

We present new analytical data of major and trace elements for the geological MPI-DING glasses KL2-G, ML3B-G, StHs6/80-G, GOR128-G, GOR132-G, BM90/21-G, T1-G, and ATHO-G. Different analytical methods were used to obtain a large spectrum of major and trace element data, in particular, EPMA, SIMS, LA-ICPMS, and isotope dilution by TIMS and ICPMS. Altogether, more than 60 qualified geochemical laboratories worldwide contributed to the analyses, allowing us to present new reference and information values and their uncertainties (at 95% confidence level) for up to 74 elements. We complied with the recommendations for the certification of geological reference materials by the International Association of Geoanalysts (IAG). The reference values were derived from the results of 16 independent techniques, including definitive (isotope dilution) and comparative bulk (e.g., INAA, ICPMS, SSMS) and microanalytical (e.g., LA-ICPMS, SIMS, EPMA) methods. Agreement between two or more independent methods and the use of definitive methods provided traceability to the fullest extent possible. We also present new and recently published data for the isotopic compositions of H, B, Li, O, Ca, Sr, Nd, Hf, and Pb. The results were mainly obtained by high-precision bulk techniques, such as TIMS and MC-ICPMS. In addition, LA-ICPMS and SIMS isotope data of B, Li, and Pb are presented.