This study investigates the spectral behavior of Mn and associated elements in Mn-rich minerals and Mn-oxide assemblages using handheld (hhLIBS) and micro-LIBS (RLIBS) techniques. Two synthetic Mn oxides (Mn2O3 and MnO2) and eight natural Mn-bearing samples from hydrothermal environments were analyzed to evaluate the consistency of Mn emission features and the effectiveness of Mn-based normalization strategies. LIBS spectra are dominated by dense Mn I emission lines across the ultraviolet and visible ranges. Comparison of integrated Mn emission features indicates that visible Mn I lines at 475-484 nm exhibits the highest intensities and lowest variability across all samples. The Mn I line at 482.352 nm consistently defines the selected Mn reference emission (Mn(ref)) and provides a stable internal reference for handheld LIBS measurements. Normalization to Mn(ref), combined with peak-area integration, partly compensates for ablation-and plasma-related variability and improves comparability of elemental signals, enabling clearer evaluation of relationships between Mn and associated elements (Na, K, Ca, Mg, Zn, Ag, Ba). Mn-normalized ratios reflect mineralogical controls on elemental behavior: alkali and alkaline-earth elements co-vary with Mn in tunnel-structured Mn oxides, whereas trace metals such as Zn and Ag show phase-dependent enrichment linked to hetaerolite and todorokite mineral phases, respectively. Spatial mapping by hhLIBS and RLIBS imaging demonstrates pronounced chemical heterogeneity and complementary Ag-Zn distributions, while localized enrichments of As and Cd further highlight trace-metal partitioning at the micro-scale. Overall, Mn(ref)-normalized peak-area metrics provide a robust framework for comparative LIBS analysis of Mn-rich materials and support the use of handheld and micro-LIBS for investigating mineralogical controls on trace-element distribution where matrix-matched calibration is impractical.

Todorokite is a unique tunnel-structured hydrous manganese oxide common in terrestrial manganese deposits. It is renowned for its excellent adsorption capacity, associated with a high specific surface area and microporous structure. Due to its role in metal accumulation in the oxidation zone of some ore bodies, todorokite may act as a vectoring tool for concealed ore deposits. This research uses a multi-method analytical approach to investigate the mineral chemistry of todorokite-rich samples from six hydrothermal deposits in different geological settings in Greece: Mavro Xylo-Karposluk (Drama), Aspro gialoudi-Vani (Milos Island), Piavitsa (Chalkidiki), Trikorfo (Thasos Island), Thapsana (Paros Island), and Koskina (Evia Island). Portable X-ray fluorescence (pXRF) was used as the primary analytical method of various Mn-ore samples, complemented by XRD, SEM and electron microprobe analysis (EMPA) for mineral characterization and finally, micro-XRF and inductively coupled plasma-mass spectrometry (ICP-MS) to determine the concentration and distribution of economically important metals (loids) such as Zn, Pb, Ag, and Sb. In this research, we demonstrate that todorokite from manganese oxide deposits adjacent to intrusion related (Piavitsa, Mavro Xylo-Karposluk) and hybrid epithermal-VMS deposits (Milos Island) shows significant enrichment in Zn, Pb, Ag, As and Sb, in contrast to samples from less mineralized settings (Trikorfo, Thapsana, Koskina) that are base and precious metal-poor. EMPA cross-sections across mineral boundaries and micro-XRF mapping confirm metal zonation and phase-specific enrichment, particularly in Agand Zn-bearing todorokite. Additionally, geochemical correlations between pXRF and bulk ICP-MS data of Mnoxide ore samples highlight the value of portable XRF as a rapid tool for detecting metal anomalies in the field. This research shows that combining portable XRF with focused mineralogical analyses can significantly improve geochemical exploration of hypogene hydrothermal and concealed deposits of base and precious metals.

Interaction between sulfate-rich basin fluids and hydrocarbons triggers thermochemical sulfate reduction (TSR), a key process in ore formation. In the Lavrion Pb-Zn-Ag district (Attica, Greece), mineralization developed during post-subduction exhumation along the West Cycladic Detachment System (WCDS) and includes porphyry Mo-Cu, Fe-Cu skarn, carbonate-replacement Pb-Zn-Ag, and vein/breccia-type Pb-Zn-Ag deposits.Sector-zoned sphalerite and later brown sphalerite record the evolution of the hydrothermal system. Brown sphalerite is enriched in Fe, Mn, Cd, and Hg, whereas Ag, In, and Ga distributions are independent of color zoning. Fluid inclusions indicate H2O-CO2-NaCl-CaCl2 fluids with salinities of 10–20 wt% NaCl eq. and homogenization temperatures of 120–280 °C. They also contain hydrocarbons (n-alkanes (C1–C6), alkenes, benzene, toluene, styrene) and sulfur compounds. Calcite δ13C-δ18O values indicate infiltration of surface-derived fluids and an increase in fluid-to-rock ratio during the transition from ductile-brittle to brittle deformation, while sphalerite δ34S values are consistent with TSR in a non-equilibrated system.Two hydrothermal-metallogenic systems operated between 10 and 7 Ma: (1) a magmatic-related system responsible for porphyry and skarn, and (2) a 280–120 °C high-temperature TSR-driven system associated with carbonatization along the WCDS, forming carbonate-replacement, vein, and breccia ores. Outside magmatic centers, metals were likely derived from leaching of volcano-sedimentary schists, metagranitic and metabasic boudins, and earlier magmatic-related mineralization.

The Kallintiri area (SW Byala Reka–Kechros Dome, Rhodope) hosts a polymetallic (critical, base, and precious metals) ore deposit, tectonically controlled by the late Eocene–Oligocene, top-to-SW Kallintiri Detachment System. The earliest structure associated with the Kallintiri Detachment is a ductile shear zone at the interface between the high-grade footwall gneisses of the Lower and Intermediate Rhodope Terranes. The detachment zone encompasses the uppermost part of the gneisses and the ultramylonitic Makri Unit marble. The marble is bound by a brittle–ductile shear zone at the base and a knife-sharp, low-angle normal fault at the roof, exhibiting considerable brecciation and ultracataclasite development. The hanging wall includes the Makri Unit phyllites and the overlying mid–late-Eocene–Oligocene supra-detachment sediments, which show syn-depositional slump structures and brittle deformation with low- and high-angle faulting and non-cohesive cataclasites. Extensive hydrothermal fluid circulation along the detachment zone and through NW tension gashes and high-angle faults led to pronounced silicification and ore deposition. Field observations and mineralogical and geochemical analyses revealed two primary types of ore mineralization spatially and temporally associated with different structures. Base and precious metals-rich ores are associated with the detachment, while Sb ore deposition is localized mostly within the NW-trending tension gashes and high-angle faults.

Rocks occupying the back-arc areas in subduction zones present a structural complexity resulting from subduction and exhumation processes, the latter contemporaneous with hydrothermal fluid circulation and ore deposition along crustal-scale shear zones. In many cases, the exhumation starts while rocks are situated in the middle crust, where ductile deformation prevails and ends when these rocks are exposed to the surface, juxtaposed against hanging wall rocks with contrasting mechanical properties and deformation history. The interplay between high- and low-grade rocks often results in complex patterns and puzzling structural inventories.The Rhodope crystalline complex (north Greece) comprises high-grade ortho-and paragneisses that were subducted in HP-UHP in the Mesozoic and exhumed in the Oligo-Miocene, through a complex network of ductile shear zones and low-angle normal faults constituting the Kechros Detachment. The high-grade footwall rocks belong to the Lower and Intermediate Rhodope Terranes, juxtaposed against the low-grade carbonates and phyllites of Makri Unit and the late-Eocene-Oligocene supra-detachment sediments and volcanic rocks.We have conducted a detailed mapping and structural study of the Kallintiri area (SW Byala Reka-Kechros Dome, Rhodope, northern Greece) to define the tectonostratigraphy of the area and discriminate between early ductile, subsequent brittle-ductile, and late brittle structures. Our results established a continuum of large-scale structures that brought the high-grade rocks from the middle crust to the surface, accompanied by corresponding fault rocks and structures, revealing the acting deformation mechanisms. During the exhumation process, the deformation was localized at the lower structural level of the Makri Unit due to the significant competence contrast between the structurally lower amphibolite-facies gneisses and the overlying lower-greenschist facies carbonates. As a result, the carbonate rocks from the hanging wall Makri Unit were mechanically coupled to the footwall and served as the main lithology that experienced mylonitic deformation.

The Plaka porphyry Mo-Cu system occurs in the world-class Lavrion Ag-Pb-Zn district in Attica, southern Greece. It is spatially associated with a granodiorite porphyry that intruded the Attic-Cycladic Crystalline Complex in the late Miocene, along the footwall of the Western Cycladic detachment fault. A Re-Os age of 9.51 +/- 0.04 Ma indicates that molybdenite formed during the early stage of the granodiorite porphyry intrusion and that subsequent cooling was very rapid. Brittle deformation and hydrothermal fluid flow created a network of A-, B-, diopside-actinolite and D-veins, associated with potassic-, sodic-calcic and sericitic alterations. Potassic alteration is characterized by secondary biotite +K-feldspar + quartz + magnetite +/- apatite, contains disseminated molybdenite, pyrite, and chalcopyrite, and formed at 420-500 degrees C, at pressures up to 530 bars (< 5.3 km depth) from hydrothermal fluids that underwent phase separation. Sodic-calcic alteration is devoid of Cu-Mo mineralization and, consists of diopside + actinolite + oligoclase/andesine + titanite + magnetite +/- epidote-allanite +/- chlorite +/- quartz, which corresponded to a temperature range of between 350 and < 500 degrees C. Primary magnetite, titanite and biotite crystallized between the nickel-nickel oxide (NNO) and hematite-magnetite (HM) buffers, indicating fairly oxidizing conditions for the granodioritic magma. Hydrothermal biotite plots closer to the HM buffer suggesting increasing oxygen fugacity during exsolution of the hydrothermal fluids associated with potassic alteration. The system evolved toward more reducing conditions during sericitic alteration and associated pyrite-molybdenite mineralization. A combination of evaporated seawater and magmatic fluids likely caused formation of the sodic-calcic alteration through the decarbonation of the host marble.

Geological characterization of the “Fonts-Bouillants” helium discovery - FranceRussier E1,2, Géraud Y2, Hauville B1, Tarantola A2 ,Beccaletto L3 and Diraison M11 45-8 ENERGY, France2 GeoRessources, University of Lorraine, France3 BRGM, F-45060, Orléans, France ABSTRACTHelium is essential for the manufacturing of many of our daily commodities such as optical fibres, computers or cell phones (semiconductors and processors), medical use (MRI scanners) or in other more specific applications such as airlifts, leak detection, gas chromatography or diving. Nowadays, Europe imports 100% of its helium needs from overseas and is facing regular shortages, reason why 45-8 Energy embarked five years ago on helium exploration and production in Europe. Helium is a noble gas mostly coming from the natural radioactive decay of Uranium and Thorium contained in the crust and the basement. Its migration and accumulation are strongly linked to a vector fluid that can be CO2, N2, CH4 or water. Helium and its vector fluids are then trapped and sealed in a rock reservoir. The Fonts-Bouillants area is located at the southern edge of the Paris Basin at the vicinity of the French Massif Central and Limagne rift. The 45-8 Energy project aims to jointly produce He and CO2 from a gas which is naturally seeping through the major Saint-Parize fault (SPF). Geological origin and migration pathway of He are therefore key questions to define the exploration guide, in particular to locate production wells to produce the seeping gas and process it. A multidisciplinary approach involving geology, geophysics, petrophysics and geochemistry has therefore been deployed. Because geological context was hardly documented in this area, a wide range of geophysical data were acquired or reprocessed and coupled with field geology to build a regional geological model. The initial geological model was considerably updated and a hidden and thick Late Palaeozoic depocenter was especially highlighted below the Mesozoic series. Well data in nearby analogous basins as well as outcrops enabled rock collections to conduct petrophysical and geochemical characterization. The main reservoirs discovered currently are in Triassic and Jurassic sandstones, and fault like Saint-Parize fault acted as barrier and drain. Our outcrops petrophysical and geochemical study highlight the importance of Late Palaeozoic basin for the helium system:As a potential rock source, with higher U-Th concentrations (3-13.5, 8-24 ppm) than typical crustal U-Th concentrations (1.8 and 7.2 ppm, [1]). As a potential migration pathway and reservoir, with sandstones and conglomerates porosity higher than 20% and permeability higher than 100 mD. Finally, gas sampling was performed in local natural springs, but also during well testing conducted in shallow boreholes which have encountered gas bearing reservoirs in the Mesozoic along the SPF. Helium generation system was modelled with geochemical data from the rocks and the fluids and from the volumetric capacity of the Palaeozoic basin. Keywords: Helium exploration, Geophysics, Petrophysics, GeochemistryThemes: Helium exploration References:[1] Krauskopf, K. B., & Bird, D. K. (1967). Introduction to geochemistry (Vol. 721). McGraw-Hill New York.

Understanding the temperature evolution of magmatic-hydrothermal systems is key to unraveling fluid-rock deformation reactions and related ore-forming processes. Ti-in-quartz thermometry has been widely used determine the quartz crystallization temperatures in these systems. However, out-of-equilibrium crystallization and fluid-assisted recrystallization of hydrothermal quartz may significantly influence the temperature estimates; a process that has not sufficiently been studied to date despite its broad implications. Here, we use the Pagoni Rachi Cu-Mo-(Re-Au) deposit (NE Greece) to provide insights into these processes. Typical A-type (ductile, 460-510 degrees C), B-type (ductile/brittle, 420-440 degrees C) and E-type (brittle, 220-330 degrees C) veins are developed in a continuum of deformation, forming from phase-separated fluids followed by cooling dilution with surface waters. In A-type veins, fluid-assisted recrystallization modified the Ti concentrations (10-60 ppm), yielding Ti-in-quartz temperatures (330-500 degrees C) lower than the fluid inclusion trapping temperatures, likely due to Ti loss. In later B-type veins, rapid growth under out-of-equilibrium conditions resulted overestimated Ti-in-quartz temperatures (440-750 degrees C), i.e., higher than fluid inclusion trapping temperatures. By contrast, effects of recrystallisation are lacking in the late-stage E-type veins, leading to a better agreement between Ti-in-quartz (160-360 degrees C) and fluid inclusion trapping temperatures. Our results show that out-of-equilibrium crystallization and fluid-assisted dynamic recrystallization processes can shift the Ti concentration in quartz leading to potential misinterpretation of the cooling path of magmatichydrothermal systems. This has also important implications on the common classification of vein types porphyry-epithermal systems based on the Al/Ti and Ge/Ti ratios in quartz. More generally, careful micro textural examinations of quartz veins are crucial for a reliable use of Ti concentrations in quartz as a petrogenetic indicator.

Strategic metals are indispensable for meeting the needs of modern society. It is then necessary to reassess the potential of such metals in Europe. For the exploration of strategic metals, portable XRF (X-Ray Fluorescence) and LIBS (Laser Induced Breakdown Spectroscopy) are powerful techniques allowing their multi-elementary analysis. This paper presents a database providing more than 2000 pXRF data and more than 4000 pLIBS spectra acquired on minerals from the Mineralogy and Petrology Museum of National and Kapodistrian University of Athens (NKUA), selected based on their potential in bearing strategic metals. The combination of these two portable techniques, along with expanding dataset on strategic metal-rich minerals, provides valuable insights into strategic metal affinities and demonstrates the effectiveness of portable tools for exploring strategic raw materials. Indeed, such database allows to strengthen the knowledge on strategic metals by producing statistic and chemometric analyses (e.g., boxplot, PCA, PLS) on their distribution.

Even if natural occurrence of Re can be found as rheniite (ReS2), most Re substitutes to Mo in molybdenite (MoS2), which explains why Re is usually a by-product of Cu-Mo deposits. In Thrace region (NE Greece), molybdenite can be enriched up to 4.7 wt% in Re in porphyry-epithermal deposits (Voudouris et al., 2013). Now, spectroscopic portable tools (e.g. pXRF) allows to directly detect Re in the field. First qualitative results obtained by pXRF show that is possible to know in which deposits from Greece the molybdenite is the most enriched without the necessity of long and costly laboratory measurements (EDS-SEM or EPMA). The X-250 pXRF (SciAps) used in this study do not include Re in its quantification program. Moreover, the spot diameter (4 mm) is generally larger than the molybdenite size in this area. Hence, Re cannot be quantified and even if it were, the value would be that of Re in the analytical spot and not in molybdenite only. The aims of this study is to (1) directly quantify Re with the pXRF and (2) determine the concentration in Re within the molybdenite. In Energy-dispersive XRF, there is an interference between the Zn-Kα emission line (8.6389 keV) and the Re-Lα emission line (8.6524 keV). If Zn is quantified and Re not included into the analytical program, the Re signal will be interpreted as Zn quantities. That is the case with our X-250 pXRF. In Thrace region, molybdenite occurs in quartz veins sometimes associated with few feldspar or pyrite but no Zn-bearing minerals. When measuring molybdenite-bearing veins, all the Zn quantitatively measured by the pXRF corresponds to a Re signal. That effect can be corrected by applying a correction factor on the Zn value to convert it into a Re quantity in situ by using calibration curves. A specific user method can also be easily implemented into the tool. In case Zn-bearing minerals are also found in the molybdenite-bearing veins, the in situ method requires a multilinear correction of signal obtained from the ROIs of Zn and Re. That is more difficult to implement and in the meanwhile, one can obtain signals from Zn and Re separately by proceeding to spectral decomposition using the PyMCA software (Solé et al., 2007). Once separated, these signals can be converted into concentrations of each elements with calibration curves. These curves have been built from the measurement of reference samples consisting in chosen proportions of SiO2 (considered as the matrix), MoS2, Re and Zn powders. That enabled to evaluate the impact of each parameter on detection limit, precision and accuracy of the Mo, Re and Zn concentrations. The calibration curves were tested by the use of a set of validation samples. In our case study, Re and Mo are only within molybdenite. The quantity of Re in the analysed area is mainly induced by the quantity of molybdenite, thus Mo, in the same area. The effect of Re-enrichment in molybdenite appears as a second order phenomenon. With these developments, Re-enrichment in molybdenite becomes a mapable parameter.

Understanding the distribution and concentration of Rare Earth Elements (REE) within various minerals and ores is crucial in mineralogy and geology for comprehending the micro-scale processes that contribute to the formation of REE-bearing minerals. Laser Induced Breakdown Spectroscopy elemental imaging emerges as a valuable tool due to its spatial resolution (15 mu m) and ability for blind and rapid identification of elements within thin rock sections. Geological samples from the metamorphic core of the Zagros orogen (Iran) prepared as thin rock sections have been analyzed by LIBS imaging. Mineralogical phases have been determined from LIBS images of major elements. We first found that the distribution of Yttrium and REEs varies depending on the metamorphic stage. Then, while garnets may exhibit zoning in Mn, we observed that not all of them incorporate Yttrium. Finally, we demonstrated that REEs carriers include bastnaesite (Y Ce La F) and xenotime-like minerals primarily composed of Y with varying amounts of Yb, Gd, and Nd. We also demonstrated that the REEs minerals can exhibit either millimetric size when embedded within andalusite phases, or micrometric size when randomly scattered throughout the matrix. And we have also observed that some samples feature abundant Y-enriched Zircon phases. This study demonstrates that mu LIBS imaging enables drawing a comprehensive picture of geological samples down to the micrometric scale. It has become a key technique in this field, providing access to the mineralogy of REE minerals, which is paramount for optimizing the final exploitation process compared to other analytical techniques.

A significant association of alunite supergroup minerals commonly associated with quartz and pyrite is found in the Kuh-e-Lakht district of NE Isfahan, Iran. These minerals occur as pervasive alterations and within hydrothermal quartz veins. Based on field observations, microscopic studies, and geochemical analyses, the alunite subgroup exhibits noticeable variations in morphology, composition, and geochemical signatures between areas with moderate to high mineralization and those with poor mineralization. Poorly mineralized regions contain aluminum-phosphate-sulfate (APS)-free minerals of the alunite subgroup formed from steam-heated acid or supergene processes at an estimated temperature of about 200 degrees C, with a higher K2O than Na2O content. These crystals exhibit pseudocubic or acicular habits and zoned formations with rhythmic bands and lack APS minerals. Moderately to highly mineralized areas in Kuh-e-Lakht host tabular to platy and bladed alunite subgroup crystals with a hypogene origin, formed at around 250 degrees C, characterized by a higher or equal Na2O content compared to K2O. These areas also feature APS minerals with different modes of occurrence. In the southwestern, northcentral, and northwestern parts, a strong genetic link with high-sulfidation minerals like pyrite, enargite, and chalcopyrite is observed. Alunite subgroup crystals with the highest Na2O/K2O ratio or equal values, as well as APS minerals with svanbergite-woodhouseite composition, occur within alunite crystals or as individual euhedral crystals exhibiting complex oscillatory zoning. These characteristics confirm a close association with the ore formation period and also the influence of higher-temperature fluids with magmatic-hydrothermal components, likely originating in closer proximity to intrusive sources. The estimated temperature for the alunite subgroup and associated ore minerals in these areas falls in the range of approximately 250 degrees C to 300 degrees C.

Geological characterization of the “Fonts-Bouillants” helium discovery - France Russier E1,2, Géraud Y2, Hauville B1, Tarantola A2 ,Beccaletto L3 and Diraison M1 1 45-8 ENERGY, France 2 GeoRessources, University of Lorraine, France 3 BRGM, F-45060, Orléans, France   ABSTRACT Helium is essential for the manufacturing of many of our daily commodities such as optical fibres, computers or cell phones (semiconductors and processors), medical use (MRI scanners) or in other more specific applications such as airlifts, leak detection, gas chromatography or diving. Nowadays, Europe imports 100% of its helium needs from overseas and is facing regular shortages, reason why 45-8 Energy embarked five years ago on helium exploration and production in Europe.   Helium is a noble gas mostly coming from the natural radioactive decay of Uranium and Thorium contained in the crust and the basement. Its migration and accumulation are strongly linked to a vector fluid that can be CO2, N2, CH4 or water. Helium and its vector fluids are then trapped and sealed in a rock reservoir.   The Fonts-Bouillants area is located at the southern edge of the Paris Basin at the vicinity of the French Massif Central and Limagne rift. The 45-8 Energy project aims to jointly produce He and CO2 from a gas which is naturally seeping through the major Saint-Parize fault (SPF).  Geological origin and migration pathway of He are therefore key questions to define the exploration guide, in particular to locate production wells to produce the seeping gas and process it. A multidisciplinary approach involving geology, geophysics, petrophysics and geochemistry has therefore been deployed.   Because geological context was hardly documented in this area, a wide range of geophysical data were acquired or reprocessed and coupled with field geology to build a regional geological model. The initial geological model was considerably updated and a hidden and thick Late Palaeozoic depocenter was especially highlighted below the Mesozoic series. Well data in nearby analogous basins as well as outcrops enabled rock collections to conduct petrophysical and geochemical characterization. The main reservoirs discovered currently are in Triassic and Jurassic sandstones, and fault like Saint-Parize fault acted as barrier and drain.  Our outcrops petrophysical and geochemical study highlight the importance of Late Palaeozoic basin for the helium system: As a potential rock source, with higher U-Th concentrations (3-13.5, 8-24 ppm) than typical crustal U-Th concentrations (1.8 and 7.2 ppm, [1]). As a potential migration pathway and reservoir, with sandstones and conglomerates porosity higher than 20% and permeability higher than 100 mD.   Finally, gas sampling was performed in local natural springs, but also during well testing conducted in shallow boreholes which have encountered gas bearing reservoirs in the Mesozoic along the SPF. Helium generation system was modelled with geochemical data from the rocks and the fluids and from the volumetric capacity of the Palaeozoic basin.   Keywords: Helium exploration, Geophysics, Petrophysics, Geochemistry Themes: Helium exploration   References: [1] Krauskopf, K. B., & Bird, D. K. (1967). Introduction to geochemistry (Vol. 721). McGraw-Hill New York.

The Skouries Au-Cu porphyry deposit is located in northern Greece and hosted by quartz monzonites and monzogranites of early Miocene age (similar to 20 Myr). The host rocks show geochemical similarities to other mafic to felsic intrusions in the district that have a similar strike direction, but which are 6 Myr older and lack evidence of economic mineralization. The Skouries magmas probably formed by fractional crystallization of mafic mantle-derived melts, from which the ore-forming fluids were released during second boiling accompanied by massive feldspar crystallization at similar to 65 wt% SiO2. Drill core samples record the dominant potassic alteration with A- and B-type veins, which are locally overprinted by chlorite-sericite alteration and related C-type veins, transitioning into sericitic alteration assemblages and D-type veins. The ore mineralization is characterized by chalcopyrite, bornite, pyrite, magnetite and accessory minerals, such as tellurides and PGE minerals. Incompatible trace element ratios of the host rocks, that are commonly used as tracers of magma fertility (e.g., Sr/Y, La/Sm), vary between the alteration-types and may therefore not generally provide a record of magmatic processes. Fluid inclusion and Ti-in-quartz thermometry yielded a temperature range of 520 to >600 degrees C for the A-type veins and 420 to 500 degrees C for the B-type veins. Decreasing fluid inclusion entrapment pressures suggest relatively rapid uplift of the hydrothermal system during the early- to main porphyry stage. Fluid inclusion compositions indicate that early K- and Cl-rich fluids caused the potassic alteration resulting in a strong mobilization of REEs, following a decrease in fluid salinity and temperature with proceeding porphyry evolution. Systematic variations in trace element contents (e.g., As, Ag, Pb) and ratios (e.g., As/Sb, Zn/Pb) of pyrite record fluid temperature changes and suggest early phase separation as a major ore-forming process. The common occurrence of native Au as inclusions in pyrite and chalcopyrite are indicative of early Au oversaturation in the fluid, which we relate to sulfide precipitation and phase separation, destabilizing the AuHS0 or Au(HS)(2)(-) complex, leading to the accumulation of Au particles. The formation of such Au colloids in fluids may thus reflect an important step towards the hydrothermal enrichment of Au in porphyry environments.

In situ analysis techniques of ore and drill core samples provide fast results that can be used to facilitate the decision-making process during the geochemical exploration of ore deposits. This study applies the use of two portable devices, pXRF and Laser-Induced Breakdown Spectroscopy (pLIBS), to a small manganese oxide deposit situated in the Rhodope metamorphic complex, Kato Nevrokopi, northern Greece. The study provides an example of exploration of a variety of manganese minerals, including Mn-oxides, Mn-carbonates, and Mn-silicates. It tests the accuracy of mineral identification using these two techniques. The application of pXRF helped in the elemental identification of critical trace metals in certain Mn minerals and showed that there is Ag enrichment in the ore, which is associated with the mineral hetaerolite (ZnMn2O4). From the LIBS analysis, it can be seen that Mn minerals with different Mn valences (+2, +3, and +4) display distinct spectra. This observation will be further examined by expanding the sampling pool of the spectra of manganese oxides. It is postulated that the presence of trace elements in Mn minerals may differ according to the valence of the Mn, which in turn affects the LIBS signals of the sample.

We provide new constraints for the fluid flow system at the origin of two F-Ba deposits located at the unconformity between the south of the Paris Basin and the northern edge of the French Massif Central. We used microthermometry and bulk crush-leach analyses to determine isotope ratios of mineralizing fluids (δ 18 O, δD, δ 37 Cl), together with cation and anion composition of fluid inclusions hosted by fluorite. Chlorinity and Cl/Br molar ratios (212–521) indicate the involvement of a brine, whose origin likely corresponds to Triassic evaporated seawater compatible with supratidal dolomitic facies preserved nearby. Microthermometry reveals high Ca/Na ratios, suggesting that the brine composition evolved from hydrothermal alteration of the Variscan basement and partial dissolution and replacement of the host sedimentary rocks. δ 37 Cl values are lower than the expected value of evaporated seawater, suggesting Cl isotope fractionation by ion filtration in clay-rich horizons. Fluorite crystallized at minimum temperatures of 70 to 110 °C, 10–40 °C warmer than the host Triassic sedimentary rocks. Ascending brines were expelled during the Early Cretaceous and experienced a drop in pressure and temperature, together with possible mixing with the SO 4 -rich pore water of the sedimentary rocks, causing precipitation of silica, followed by fluorite and barite, forming a stratabound deposit similar to those found in many areas in Western Europe.

The Eocene epoch in China is characterized by the abundance of salt-mudstone rhythms in the eastern basins, which are considered ideal for the reconstruction of eastern Asian paleoclimate. Salt deposits correspond to relatively extreme climate events. However, due to insufficient independent temperature proxies, there is a lack of paleotemperature records obtained from salt laminae depositions. Here, we measured fluid inclusion by microthermometry to study halite samples from the third member of the Qianjiang Formation in the Qianjiang Depression, Jianghan Basin, central China. Following approprite sample preparation measures, homogenization temperatures (Th) of primary fluid inclusions in chevron and cumulate halite crystals that can represent air temperatures at the time of deposition, were plotted in two separate ranges: 12.1-29.9 degrees C and 36.2-47.2 degrees C, representing winter and summer temperature fluctuations, respectively. In comparison with modern evaporative environments and temperatures calculated from oxygen isotopes in mudstones and dolomites that are spatially related to our halite samples it was found that the annual temperature fluctuations in the middle Eocene of the Jianghan Basin has been very similar to the Badwater Basin in Death Valley. Furthermore, the salt rhythms were mainly controlled by water influx and evaporation capacity rather than the elevated temperatures. Ultimately, statistical analysis of the homogenization temperature data and cross-plots of the carbon and oxygen isotopes revealed a monsoon climate that could have been more likely to prevail during the middle Eocene epoch of the Jianghan Basin.

The Lavrion mining district (SE Attica, Greece) comprises ore deposits of (1) low-grade Mo-Cu porphyry style, (2) Cu-Fe skarn, (3) high-temperature carbonate replacement Pb-Zn-Ag-(Au), and (4) vein and breccia Pb-Zn-Ag mineralizations. These are the result of the transport and deposition of economic elements from fluids that circulated from the construction to the gravitational collapse of the Hellenides-Aegean Domain along the Africa-Eurasia convergent plate boundary active for the last 80 Ma. Oceanic and continental rocks of the African plate were buried to high pressure conditions in the subduction zone. Progressive southward slab retreat was accompanied by magmatism and exhumation of metamorphic rocks along high- and low-angle detachment systems, with associated mineralized systems. The porphyry and skarn deposits are spatially and genetically related to the Plaka magmatic in tru sion dated 12 – 8 Ma. Carbonate replacement is associated with decarbonation and the liberation of CO2 during exhumation at the ductile to brittle transition. Fluorite and calcite gangue minerals enclosing the vein and breccia Pb-Zn-Ag mineralization were precipitated during brittle deformation from a fluid resulting from mixing of meteoric water with evaporated seawater closer to the surface. Base and precious metals were exploited since the Bronze Age to the late 20th century. As such, the Lavrion area represents an exceptional site to study the evolution of mining technologies through history.