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International audience; The hydrothermal native element-arsenide mineralization (five-element) type comprises native Ag and/or native Bi as well as Ni-, Co-, and Fe-arsenides and-sulfarsenides. Due to the current surge in Co-demand, this mineralization type has regained recent economic interest. Thus, it is of interest to further understand the paragenetic and possible spatial relation of Co-bearing minerals and the formation mechanism/process of this mineralization type. This is achieved through an extensive literature review in combination with newly calculated stability relations. The mineralization is host rock independent, but spatially linked to sources of reducing agents (as this is the cause of precipitation). This reduction process results in a thermodynamically controlled characteristic Ni- Co- Fe-diarsenides sequence, as well as a transition from native elements to mono-to di-arsenides. The temporal Ni  Co  Fe trend has also been described to occur on a special scale, and since it is ubiquitous, it may be used as a tool in constraining Co rich sections of a deposit. The formation of this mineralization is, however, not only thermodynamically, but also kinetically controlled, as is evident by the abundant dendritic textures. Kinetics favor a sulfate-sulfide disequilibrium which enables an aqueous sulfide poor system that allows for arsenide formation.

International audience; At the giant tin deposit of San Rafael, Peru, the early hydrothermal stages, preceding the economic tin mineralization, include successively: 1) potassic alteration represented by hydrothermal K-feldspar altering magmatic plagioclase; 2) sericite replacing magmatic plagioclase in the ground mass and hydrothermal K-feldspar, with greisen formation in the apical part of the intrusion; 3) widespread albitic alteration, both disseminated and as intense replacement along fractures, overprinting and obliterating the previous stages; 4) quartz-tourmaline veins rimmed by albitic alteration halos. In this contribution, the greisen-style alteration and sodic alteration, are studied in depth. Trace element analysis of hydrothermal albite reveals a marked enrichment in incompatible elements (B, Rb, Cs) compared to magmatic plagioclase, suggesting albitization was triggered by magmatic fluids exsolved from an evolved silicate melt.

We present a combined study of oxygen and boron isotopes (δ18O and δ11B) measured in situ in tourmaline from the giant San Rafael tin deposit (Central Andean Tin Belt, Southeast Peru) to trace fluid processes during the magmatic-hydrothermal transition leading to tin mineralization. The results show that magmatic and pre-ore hydrothermal tourmaline has similar δ18O-δ11B values, which are consistent with crystallization in a continuously evolving magmatichydrothermal closed system. In contrast, syn-ore hydrothermal tourmaline has δ18O-δ11B values defining a linear array interpreted as the result of mixing with external fluids, thus indicating an opening of the hydrothermal system during the ore stage. Quantitative fluid modeling shows that a Rayleigh fractionation process in a closed system reproduces closely the δ18O- δ11B compositions of magmatic and pre-ore tourmaline, whereas mixing of a hot and saline (500°C, 45 wt% NaCl eq) tin-rich magmatic fluid with a heated meteoric fluid (250°C, 0 wt% NaCl eq) explains the observed δ18O-δ11B compositions for syn-ore tourmaline.

The investigations in Sboryanovo in 2015 were carried out in accordance with the program of the Bulgarian-Swiss project “Sboryanovo: Necropolises and Territory”. Twelve specialists and 16 students participated in the investiga-tions that included the study of the ditch of the tumulus, geological and lithological investigations and observations on the profiles, archaeozoological and bioanthropological studies, 3D and photogrammetric documentation.

Cerro de Pasco, part of the Miocene metallogenic belt of central Peru, is one of the largest known epithermal base metal deposits. The deposit formed along the eastern margin of a diatreme-dome complex emplaced in the Mid-Miocene. It is interpreted to represent the upper part of a porphyry Cu system but until now no evidence of porphyry mineralization has been found. We report the first evidence of multiple porphyry events at Cerro de Pasco. First, hornfels and magmatic clasts with typical A- and B-type quartz-molybdenite porphyry veins were found incorporated in a magmatic breccia, part of the diatreme-dome complex. In addition, direct evidence of porphyry-style mineralization at surface has been found in a silica-rich andesitic plug-like body crosscutting the diatreme-dome complex. The body is affected by a network of quartz-magnetite-chalcopyritepyrite veins. Petrography, SEM-CL imaging, mineral thermometry and fluid inclusion studies indicate that quartz-molybdenite porphyry veins are formed in hightemperature and pressure environment, up to 600°C and 1.4 kbar. Late quartz-magnetite-chalcopyrite-pyrite veining affecting the andesitic plug shares characteristics with shallow porphyry-style mineralization. These new observations suggest that Cerro de Pasco is a long-lived mineralized system, product of multiple overprinting mineralizing events.

New data for the magmatism, hydrothermal alteration, mineralization styles, isotope geochronology, mineralogy, fluid-inclusionsand elemental geochemical associations are combined in the present study to characterize the Tran Au- Ag±W deposit in Western Bulgaria. The main features of the deposit define it as intrusion-related gold system (IRGS): its association with reduced plutons; well-defined structural control on intrusion and mineralization; diverse mineralization styles, including veins, stockworks, dissemination; wide range of gold grades; approximately coeval magmatism and mineralization at 330-333 Ma; low sulfide content; apparent correlation of Au and Bi; and the presence of СО2 in hydrothermal fluids. These characteristics are useful for further prospecting for IRGS in the Variscan Belt of Eastern Europe.

This contribution provides an overview of available experimental, thermodynamic, and molecular data on Au aqueous speciation, solubility, and partitioning in major types of geological fluids in the Earth's crust, from low-temperature aqueous solution to supercritical hydrothermal-magmatic fluids, vapours, and silicate melts. Critical revisions of these data allow generation of a set of thermodynamic properties of the AuOH, AuCl−2, AuHS, and Au(HS)−2 complexes dominant in aqueous hydrothermal solutions; however, other complexes involving different sulphur forms, chloride, and alkali metals may operate in high-temperature sulphur-rich fluids, vapours, and melts. The large affinity of Au for reduced sulphur is responsible for Au enrichment in S-rich vapours and sulphide melts, which are important gold sources for hydrothermal deposits. Thermodynamic, speciation, and partitioning data, and their comparison with Au and S contents in natural fluid inclusions from magmatic-hydrothermal gold deposits, provide new constraints on the major physical-chemical parameters (temperature, pressure, salinity, acidity, redox) and ubiquitous fluid components (sulphur, carbon dioxide, arsenic) affecting Au concentration, transport, precipitation, and fractionation from other metals in the crust. The availability and speciation of sulphur and their changes with the fluid and melt evolution are the key factors controlling gold behaviour in most geological situations.

The large Cerro de Pasco Cordilleran base metal deposit in central Peru is located on the eastern margin of a Middle Miocene diatreme-dome complex. A striking characteristic is the presence of a N-S trending massive funnel-shape pyrite-quartz replacement ore body that contains pyrrhotite pipes grading outwards to lead-zinc replacement bodies, along the eastern contact of the diatreme-dome complex. Earlier workers interpreted the pyrrhotite pipes as postdating the pyritequartz body. This study, that has been possible through access to new mining areas and drill cores, allows an alternative interpretation. The new data strongly suggest that the pyrrhotite pipes and their associated lead-zinc replacement bodies predated the formation of the pyritequartz body

A great majority ofporphyry districts around the world show aregular pattern of zonal metal distribution –both vertically and laterally. Metal zonation commonly consists ofa Cu±Mo±Au core ringed by successive Cu-Zn, Zn-Pb-Ag, Pb-Ag (±Mn), and As-Sb-Hg±Auzones. If ahigh-sulfidation epithermal system is developed above the porphyry center, a vertical Cu±Au±Agzone may be present in the central upflow conduits. Comparing metal content in natural fluid inclusions from porphyry and associated skarn and epithermal deposits with thermodynamic predictions provides useful constraints on the mechanisms and processes controlling metal transport and deposition in porphyry systems. Results showthat decompression and cooling of a magmatic fluid, accompanied by boiling and water-rock interaction, are likely to be the major causes of zonal metal deposition in magmatic-hydrothermal systems. Large-scale fluid mixing is a relatively uncommon phenomenon during metal precipitation and is not expected to be a major cause of ore formation in the porphyry environment.

To constrain the fluid evolution in the polymetallic Main Stage (MS) veins at Butte, USA, we present microthermometric measurements of fluid inclusions assemblages (FIAs) in co-genetic ore and gangue minerals through the different mineralization stages. Early quartz-hosted FIAs indicate the highest homogenization temperatures (Th, between 290° and 320 °C) with salinity similar to the intermediate density FI of the pre-Main Stage (4 to 6 wt. % NaCl equiv). During the Cu-rich mineralization stage, a drop in salinity to 2 wt.% NaCl equiv. at temperature ~280°C, precedes locally developed phase separation, witnessed by coexisting vapor-rich and liquid-rich FI with similar Th but with higher salinity (2.5 to 7 wt.% NaCl equiv.). Primary FIAs in sphalerite and rhodochrosite from the late mineralization stage indicate fluid temperature (Th~210°C) and salinity (1.7 to 4 wt.% NaCl equiv.) decrease through time, towards the periphery of the district. This study suggests that mixing of a high-temperature fluid with salinity similar to fluids from the pre-Main Stage quartz-pyrite veins with cooler and lower salinity fluids (potentially of meteoric origin) combined with local boiling processes are responsible of the ore precipitation in the MS veins.

The Cu-Bi-Ag-Te mineralization found in moraine blocks in the central part of the Modi-Khola valley, on the southwestern flank of Annapurna-III in central Nepal can be defined as a new type postcollisional hydrothermal system in the High Himalaya, related to a Miocene magmatic event of leucocratic granite intrusions or equigranular pegmatite bodies. The mineral assemblage consists dominantly of chalcopyrite and pyrite, with variable amounts of Bi-Ag sulphides, sulphosalts and tellurides (bismuthinite, tetradymite, hessite, aikinite-bismuthinite derivates). Ilmenite, magnetite, cubanite, garnet, rutile, chlorite and quartz complete the mineral assemblage. Common complex intergrowth textures, involving aikinte, hessite and tetradymite in highly variable proportions and forming equilibrium assemblages, resulted from segregation and crystallization of “droplets” of Ag-Bi-Te-(S) “melts” from the hydrothermal fluids at temperatures above the melting point of bismuth. Thus, the mineralization can be considered as mesothermal ore formation, most probably resulting from a magmatic-hydrothermal system that was active during the mid- Miocene in the Annapurna Himal.

The Miocene epithermal Au-Ag deposits of Roşia Montană and Rodu-Frasin are located in the South Apuseni Mountains in Transilvania, western Romania, in the province of Alba Iulia. Both deposits lie in a northwesterly striking extensional structure. Miocene calc-alkaline magmatism is related to extensional tectonics due to block rotations during Carpathian orogenesis. Roşia Montană is among the biggest epithermal Au deposits in Europe with total reserves of 217.96 Mt of ore at 1.52 g/t Au and 7.5 g/t Ag (Wallier et al., submitted). This study represents the work of two completed Master thesis on the deposit of Roşia Montană and two ongoing master thesis on the deposit of Rodu-Frasin with main focus on fluid evolution studied by fluid inclusion analysis.

Geochemistry, mineralogy and petrology, 43, Au-Ag-Te-Se deposits. Proceedings of the 2005 Field Workshop, Kiten, Bulgarian, 14-19 September 2005

This review compiles geological, mineralogical, and isotopic data from the four largest Cu–Au epithermal deposits of the Late Cretaceous Panagyurishte mineral district, Bulgaria, including from north to south: the producing Chelopech, and the past-producing Krassen, Radka and Elshitsa deposits. Epithermal Cu–Au deposits of the northern and older part of this district are mainly hosted by andesites, whereas those from the southern and younger district are hosted by dacites. Advanced argillic alteration is described in the majority of the deposits, with the most complex alteration assemblage occurring at Chelopech. In all deposits, mineralization is the result of replacement and openspace deposition producing massive sulphide lenses surrounded by disseminated mineralization. Additionally at Chelopech, stockwork vein zones are also an important ore type. At Elshitsa, Radka and Krassen, the mineralized zones are controlled by WNW-oriented faults, and at Chelopech there is a supplementary control by NE-oriented faults. A three-stage paragenesis is recognized in all deposits, including an early disseminated to massive pyrite stage; an intermediate, Au-bearing Cu–As–S stage, which forms the economic ore; and a late Zn–Pb–Ba stage. Sulphur isotopic compositions of sulphide and gangue minerals are consistent with similar data sets from other highsulphidation deposits. Variations in Sr and Pb isotope data among the deposits are interpreted in terms of fluid interaction with different host-rocks, additionally variability in Pb isotopic compositions can be attributed to differences in composition of the associated magmatism. Throughout the Panagyurishte district, there is a coherent and continuous sequence of events displayed by the epithermal Cu–Au deposits indicating that they result from similar ore forming processes. However, latitudinal differences in ore deposit characteristics are likely related to emplacements at different depths, differences in degrees of preservation as a function of post-ore tectonics and/or sedimentary processes, efficiency of ore formation, and/or modifications of regional controls during the 14 Ma-long geological evolution of the Panagyurishte district, such as magma petrogenesis and/or tectonic regimes.

The Radka deposit is one of the largest Cu–Au epithermal deposits related to Late Cretaceous volcanic arc-type magmatic activity in the Panagyurishte ore region, central part of the Srednogorie zone, Bulgaria. The mineralogical and geochemical features of a vinciennite-bearing Cu–As–Sn (± Au) assemblage at Radka show very similar characteristics to those in other vinciennite-bearing high-sulfidation epithermal deposits worldwide. The assemblage consists of enargite, Cu-excess tennantite, chalcopyrite, gold, vinciennite, colusite, and minor covellite, within a gangue of barite, illite, and quartz. A detailed electron-microprobe study of vinciennite and associated minerals reveals the heterovalency of Cu and Fe. New data on the composition of vinciennite sheds light on aspects of its crystal chemistry, such as incorporation of Cu2+ and Fe3+ and Sn4+ Ge4+ substitution, and leads us to propose a new empirical formula: Cu+8Cu2+2Fe3+3(Fe,Cu)2+ (Sn,Ge)4+(As,Sb)5+S162–. Infrared microthermometry of enargite-hosted fluid inclusions provides constraints on the conditions of deposition of this unusual assemblage in the context of the evolution of the magma-related ore-forming system at Radka. The assemblage was formed by oxidized and slightly acid fluids, with a dominantly magmatic signature, high fugacity of sulfur and intermediate salinity (about 10 wt.% eq. NaCl) at a temperature of about 275°C. In view of the geology of the Radka deposit, its mineralogical and geochemical peculiarities, ore textures, type of hydrothermal alteration and the character of the fluids, we interpret the deposit as a deep part of a high-sulfidation epithermal mineralization, possibly genetically related to a porphyry copper system.

Pyrite samples from the Radka epithermal, replacement type, volcanic rock-hosted copper deposit, Bulgaria, have been studied using near-infrared (IR) microscopy. Two generations of pyrite based on their textures, composition and behaviour in IR light can be distinguished. Electron microprobe analyses, X-ray elemental mapping and Fourier transform infrared spectroscopy were used to study the relationship between crystal zoning, trace element contents and IR transmittance of pyrite. The observed crystal zoning is related to variable arsenic contents in massive fine-grained and colloform pyrite from the early pyrite-quartz assemblage, and cobalt contents in pyrite crystals from the late quartz-pyrite vein assemblage. There is a negative correlation between trace element content and IR transmittance of pyrite. The IR transparency of pyrite is thus a sensitive indicator of changes in trace element concentrations. Fluid inclusions have only been found in the second pyrite generation. Scanning electron microscopy observations on open fluid inclusion cavities permitted the crystallographic features of vacuoles to be determined. A characteristic feature of primary fluid inclusions in pyrite is a negative crystal habit, shaped mainly by {100}, {111} and {210}. This complicated polyhedral morphology is the reason for the observed opacity of some isometric primary inclusions. Secondary fluid inclusion morphology depends on the nature of the surface of the healed fracture. Recognition of the primary or secondary origin of fluid inclusions is enhanced by using crystallographically oriented sections. Microthermometric measurements of primary inclusions indicate that the second pyrite generation was deposited at maximum P-T conditions of 400 °C and 430 bar and from a fluid of low bulk salinity (3.5-4.6 wt%), possibly KCl-dominant. There are large ranges for homogenisation temperatures in secondary inclusions because of necking-down processes. Decrepitation features of some of pyrite-hosted inclusions and of all inclusions in associated quartz indicate reheating of the veins to 500-550 °C. The late cobalt-rich quartz-pyrite vein assemblage in the Radka deposit may be the shallow manifestation of deeper and genetically related porphyry copper mineralisation. This is a common observation of many intermediate- to high-sulfidation epithermal replacement-type ore bodies in this ore district and possibly the Cretaceous Banat-Srednogorie metallogenic belt in general.

Two major types of Cu-Au ore deposits, genetically related to the Upper Cretaceous volcanic arc magmatic activity are recognised in the Panagyurishte district, Sredna Gora zone (Bulgaria): replacement type epithermal and porphyry copper deposits. Detailed studies of mineral composition, trace-element distribution, stable (O, H, S) and radiogenic (Sr, Pb) isotopes and fluid inclusions (visible and IR light) have been performed in the Radka and Elshitsa epithermal and the Vlaikov Vrah porphyry-Cu deposits, in order to constrain the origin of epithermal mineralisations and to test the hypothesis of the genetic connection between porphyry and epithermal systems. The results of field work and laboratory analyses confirmed the epigenetic character of studied mineralisations and permitted us to characterise them as deeper parts of high- to intermediate-sulphidation epithermal systems. The deposits were formed by oxidised, relatively acidic fluids with fluctuating , but generally high, sulphur fugacity. Four principal ore stages can be recognised in the epithermal deposits: an early stage of massive As-bearing pyrite, a copper stage with a very characteristic signature (Bi-Te-Se-As-Sn-Pb), a polymetallic (Zn-Pb-Cu) stage, and a late anhydrite stage indicating the progressive oxidation of the system. Fluid inclusion and stable isotope study reveal the participation of magmatic fluids to the ore formation, and their mixing with meteoric water during the late stages of evolution of the hydrothermal system. Radiogenic isotope study indicates extensive fluid circulation through the metamorphic basement and shows that both the porphyry-Cu and epithermal Cu-Au deposits in the southern part of the Panagyurishte district formed during the same metallogenic event. Upper Cretaceous intrusive rocks are the most probable source of metals for the formation of economic mineralisations., Le district de Panagyurishte, zone de Sredna Gora (Bulgarie) comporte deux types de gisements cuprifères à métaux précieux liés génétiquement au magmatisme d'arc néocrétacé : des gisements épithermaux de remplacement et des porphyres cuprifères. Afin de contraindre l'origine des gisements épithermaux de Radka et d'Elshitsa dans la partie sud du district, et de tester l'hypothèse de la liaison génétique entre minéralisations épithermale et porphyrique, l'analyse de la composition minéralogique et l'étude des éléments-traces des deux gisements épithermaux et du porphyre cuprifère de Vlaikov Vrah, associé à l'épithermal d'Elshitsa, ont été réalisées en parallèle avec l'étude isotopique (isotopes stables – O, H, S et radiogéniques – Sr, Pb) et des inclusions fluides (en lumière visible et IR). Les résultats obtenus lors des travaux de terrain et des analyses au laboratoire nous ont permis de confirmer le caractère épigénétique des minéralisations étudiées et de les caractériser comme des parties profondes des systèmes de type épithermal acide à intermédiaire. Les gisements ont été formés à partir de fluides oxydés, relativement acides et à fugacité en soufre fluctuante, mais tout en restant relativement élevée. Quatre stades principaux de minéralisation peuvent être définis dans les gisements épithermaux : un stade précoce à pyrite massive arsénifère, un stade à cuivre de composition géochimique très caractéristique (Bi, Te, Se, As, Sn, Pb), un stade polymétallique marqué par l'association Zn-Pb-Cu et un stade sulfaté à anhydrite tardive, marquant l'oxydation progressive du système. L'étude des inclusions fluides et des isotopes stables a révélé le rôle important des fluides magmatiques pour la formation des gisements, qui se mélangent avec des fluides météoriques aux cours des stades tardifs de l'évolution du système hydrothermal. La composition des isotopes radiogéniques a mis en évidence une circulation intense des fluides à travers le socle métamorphique et a permis de définir les deux types de gisements cuprifères dans la partie sud du district de Panagyurishte comme faisant partie d'un même événement métallogénique et ayant comme source de métaux la plus probable les roches plutoniques néocrétacées.