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Georgia is located in the central part of the Caucasus, which is the northern segment of the Eastern Mediterranean orogen system and extends over 1,200 km in a NW-SE direction between the Black and the Caspian Seas. In this study, our goal was to investigate the Th and U ore occurrences in the country. As a result of the research, we have identified 3 uranium and 4 thorium occurrences that need more in-depth investigation. Among them, there should be mentioned the Shkhara uraninite occurrence that we discovered in the pre-Jurassic Shkhara crystal-line massif. This occurrence formed in the Paleozoic biotite plagiomigmatites is in full correlation with uraninite deposits found in different parts of the world.

The Zarshuran gold deposit (155 t Au, average grade: 2.63 g/t), NW Iran, provides a new paradigm for understanding the multicomponent ore-forming processes and metallogeny of gold during the evolution of hydrothermal fluids. It is characterized by auriferous quartz veins and gold coexisting with disseminated Fe-As-S sulfide minerals that are hosted in a sequence of Early Cambrian metasedimentary rocks. A complex paragenesis is defined by five sulfide stages: pre-ore stage pyrite (Py0), early ore-stage pyrite (Py1 and Py2), middle ore-stage pyrite (Py3a, Py3b, and Py3c), late ore-stage pyrite (Py4), and post ore-stage pyrite (Py5). Py0 with framboidal texture is characterized by relatively low concentrations of As, Au, Cu, and Sb, and has a broad range of negative δ34S values from −28.2 to −3.7 ‰, indicating microbial reduction of marine sulfate. Py1 and Py2 show porous texture with As-rich bright bands also having high Au (mean: 18.4 ppm). Similarly, narrow ranges in δ34S from −3.6 to +3.2 ‰ likely suggest a deep-seated magmatic sulfur source. In the middle ore-stage, Py3a cryptocrystalline cores have a range of positive δ34S (+5.4 to +26.7 ‰) values and high concentration of As(-Au), whereas later well-crystallized outer rim Py3c is Co(-Ni) rich, has a much more restricted δ34S range (−2.9 to +1.4 ‰), indicating an evolution of fluid composition from As-rich to Co-rich. Most of the gold (mean: 20.2 ppm) and trace elements (Hg, Ag, Sb, and Tl) were deposited in Py4, whose δ34S values (+5.4 to +26.7 ‰) show that ore fluid sulfur in this stage was mainly sourced from a mixture of magmatic sulfur with minor input of reduced sedimentary rocks. Low gold and trace element content with slightly negative δ34S values (–8.5 to –4.2 ‰) of Py5 show that they were likely formed from a metal-poor oxidizing fluid. The mineralizing fluid system can be described as carbonic-aqueous with low to moderate salinity (3.2–15.1 wt% NaCl equiv.) and medium temperature of 285 to 317 °C (early ore-stage) and 255 to 290 °C (late ore-stage), which suggests that phase separation was responsible for gold precipitation during late ore-stage As-Hg-Sb sulfide veins. The δ18Ofluid ranges from −7.8 to +4.2 ‰, and the δD values for fluid inclusions in mineral range from −105 to −65 ‰, suggesting involvement of meteoric water during late- to post ore-stages. Our results indicate that the Zarshuran is a distal disseminated gold deposit formed during southward subduction of the Proto-Tethys oceanic lithosphere beneath the northern margin of Gondwanan terranes through the early Cambrian.

The melting relations of the CaCO3 MgCO3 system are investigated and trace element partition coefficient of Li, Na, K, Mn, Fe, Sr, Ba, Pb, Nb, Y and rare earth elements (REEs) between carbonates (Mg-calcite, Ca-magnesite) and dolomitic melt are established from high pressure (6 and 9 GPa) and temperature (1300 1800 ℃) experiments utilizing a rocking multi anvil press. We show that Ca Mg carbonates are stable within the subducting slab beyond ~300 km (9 GPa) but will (partial) melt beneath mid ocean ridges and in upwelling plumes. In contrast to previous studies, we report incongruent melting of carbonates producing a carbonate melt and periclase between 4 and 9 GPa. Partial melting of carbonates produces dolomitic melts whereby the trace element signature largely depends on the Ca/Mg-ratio of the bulk system. For instance, REE will be fractionated by two orders or magnitude between Ca magnesite and dolomitic melt. In contrast, melting of Ca rich carbonates will not lead to a significant REE fractionation. The here published data set includes all chemical analysis (major and trace elment composition) of run products and starting materials. From this data set we obtained the melting relations and partition coefficients reported in Sieber et al. (2020); Sieber et al. (under review).

Der Artikel fragt nach dem Einfluss digitaler Medien auf die Praktik des Lesens. Der methodischen Herausforderung, digitales Lesen zu untersuchen, wird mit dem Entwurf einer literatur- und medientheoretisch informierten Lesepraxeologie begegnet. Diese geht aus theoretischen Überlegungen hervor, die u.a. auf der Materialitätsforschung, Wolfgang Isers Leseakttheorie und dem Eigenschaftskatalog digitaler Lesemedien (Kuhn & Hagenhoff) aufbauen. Anhand zweier literarischer Beispiele wird veranschaulicht, wie Lesen an digitalen Medien von Affordanzen begleitet wird, die stabile Lesestrategien erfordern.

This data set is the source of my doctoral thesis and of three resulting publications. Through whole rock geochemistry of selected samples and microprobe and geochronological analyses of key minerals, formerly selected by extensive microscopical studies, standard geothermobarometry and modelling was applied. It has been shown that metamorphic rocks, in particular, the eclogites of the northern Kaghan Valley, Pakistan, were buried to depths of 140-100 km (36-30 kbar) at 790-640°C. Subsequently, cooling during decompression (exhumation) towards 40-35 km (17-10 kbar) and 630-580°C has been superseded by a phase of reheating to about 720-650°C at roughly the same depth before final exhumation has taken place. In the southern-most part of the Kaghan Valley, amphibolite facies assemblages with formation conditions similar to the deduced reheating phase indicate a juxtaposition of both areas after the eclogite facies stage and thus a stacking of Indian Plate units. Radiometric dating of zircon, titanite and rutile by U-Pb and amphibole and micas by Ar-Ar reveal peak pressure conditions at 47-48 Ma. With a maximum exhumation rate of 14 cm/a these rocks reached the crust-mantle boundary at 40-35 km within 1 Ma. Subsequent exhumation (46-41 Ma, 40-35 km) decelerated to ca. 1 mm/a at the base of the continental crust but rose again to about 2 mm/a in the period of 41-31 Ma, equivalent to 35-20 km. Apatite fission track (AFT) and (U-Th)/He ages from eclogites, amphibolites, micaschists and gneisses yielded moderate Oligocene to Miocene cooling rates of about 10°C/Ma in the high altitude northern parts of the Kaghan Valley using the mineral-pair method. AFT ages are of 24.5±3.8 to 15.6±2.1 Ma whereas apatite (U-Th)/He analyses yielded ages between 21.0±0.6 and 5.3±0.2 Ma. The southern-most part of the Valley is dominated by younger late Miocene to Pliocene apatite fission track ages of 7.6±2.1 and 4.0±0.5 Ma that support earlier tectonically and petrologically findings of a juxtaposition and stack of Indian Plate units. As this nappe is tectonically lowermost, a later distinct exhumation and uplift driven by thrusting along the Main Boundary Thrust is inferred. Out of this geochemical, petrological, isotope-geochemical and low temperature thermochronology investigations it was concluded that the exhumation was buoyancy driven and caused an initial rapid exhumation: exhumation as fast as recent normal plate movements (ca. 10 cm/a). As the exhuming units reached the crust-mantle boundary the process slowed down due to changes in buoyancy. Most likely, this exhumation pause has initiated the reheating event that is petrologically evident (e.g. glaucophane rimmed by hornblende, ilmenite overgrowth of rutile). Late stage processes involved widespread thrusting and folding with accompanied regional greenschist facies metamorphism, whereby contemporaneous thrusting on the Batal Thrust (seen sometimes equivalent to the MCT) and back sliding of the Kohistan Arc along the inverse reactivated Main Mantle Thrust caused final exposure of these rocks. Similar circumstances have been seen at Tso Morari, Ladakh, India, 200 km further east where comparable rock assemblages occur. In conclusion, as exhumation was already done well before the initiation of the monsoonal system, climate dependent effects (erosion) appear negligible in comparison to far-field tectonic effects. Thus, the channel flow model is not applicable for this part of the Himalayas.

Core samples have been taken for complementary laboratory seismic measurements and mineralogical analyses on whole rock core from the COSC-1 borehole, Sweden (UTM 63.3124, 13.5259). These samples were used to provide and characterize the seismic properties (i.e., seismic velocities and anisotropy) of the drilled rocks from the highly metamorphosed and deformed Seve Nappe Complex, an orogenic thrust zone in the Scandinavian Caledonides, in central Sweden. The laboratory seismic and mineralogical analysis in general comprises three distinct measurements (i.e., data sets), which will be described in detail in the following subsections: (1) P- and S-wave laboratory seismic measurements on three perpendicular core plugs, under different confining (hydrostatic) pressure conditions (10 + 6 samples), (2) Bulk mineralogy of core plugs using X-ray powder diffraction (XRD) and mineral chemical composition measurements using an electron probe micro-analyzer (EPMA, here microprobe), on 10 thin sections and (3) Microstructural investigations based on electron-backscatter diffraction analyses on 5 thin sections. The laboratory seismic measurements were initially conducted on 6 samples by Wenning et al. (2016) and extended by another 10 samples by Kästner et al. (2020). Despite these authors were using the same sensor setup, the provided data files may differ due to individual acquisition parameters. Where different acquisition, processing, or calibration parameters are used this is indicated in the text using the abbreviations FK and QW referring to each examiner and their related sample measurements. International Geo Sample Numbers (IGSN) are provided for each core sample in the complete sample data table.

The crystal chemistry of tourmaline, XY3Z6(T6O18)(BO3)3V3W, has a strong influence on the structure and physical properties. Since tourmalines occur in a wide range of geological settings and have large temperature and pressure stability fields, the understanding of the relation between the tourmaline chemistry and thermal expansion allows for better thermodynamic modeling of geological processes. Here, we report dynamic and static thermal expansions as well as mode Grüneisen parameters studied by Raman spectroscopy and single-crystal X-ray diffraction data on several tourmaline species. In addition, oxidation processes in fluor-schorl and Fe2+-bearing elbaite were followed by Raman spectroscopy. Our results emphasize the role of Y-/Z-site occupancy disorder to reduce the local strains and demonstrate that small-size octahedrally coordinated cations perturb the topology of the SiO4 rings, which in turn seems to enhance the anisotropic thermal-expansion response. In addition, it is shown that the temperature-dependent behavior of the VOH modes primarily depends on the occupancy of the Y site, whereas that of the WOH modes depends on the occupancy of the X site. High-temperature Raman experiments in air allowed to follow the oxidation of Fe2+ to Fe3+ in fluor-schorl by analyzing both the framework and OH-stretching phonon modes. It is further demonstrated that under the same conditions, no oxidation of iron is observed for Fe2+-bearing elbaite, which implies that at high oxygen fugacity, iron is only oxidized in tourmaline species with prevalent divalent cations at the Y site.

The Central Rift in Kenya (CRK) comprises the lakes Naivasha, Elementaita and Nakuru and the Longonot, Eburru and Menengai volcanos. The alkaline magmas, produced by the volcanoes within the CRK, lead to solid rocks likes trachytes, phonolites, and fewer basalts and accompanied soft rocks like ashes, tuffs, pumices and ignimbrites (e.g. Macdonald et al., 1987; Macdonald, 2014). Lacustrine sediments and beds of diatoms are remnants of former lake level variations caused by climate variability and topographic changes (e.g. Stoof-Leichsenring et al., 2011). The samples have been taken within the frame of a VW-Foundation funded project that tries to detect, map and monitor groundwater pollution from anthropogenic and natural sources. For a previous VW-Foundation funded project (grant 85465), also the groundwater fluoride enrichment in the CRK have been studied (Olaka et al., 2016).

The trace element distribution in samples from eight VMS deposits which have experienced varying metamorphic grades were investigated by LA-ICP-MS spot analyses and mapping. Gold and the PGE in pyrite can be observed in samples from varying metamorphic grades. They do not show any systematic variation depending on metamorphic pressure or temperature and their presence in the samples indicate that no melt migration has occurred. Samples from deposits at amphibolite metamorphism show a homogeneous distribution of Se, Sb, and Te, while Ag, Rb, Sr, Mo,and Bi are enriched in bornite compared to sphalerite and pyrite. At greenschist metamorphic grade, Se and Sb are heterogeneously distributed among the different sulfide phases with Se being most enriched in pyrrhotite and Sb in chalcopyrite. Tellurium shows a homogeneous distribution between sulfide phases. Some other elements are as well enriched in chalcopyrite compared to pyrite and pyrrhotite, including V, Cr, Mn, Ni, Ga, Ge, Mo, Ag, Cd, In, Sn, and W. Cadmium, In, and Mn are even more enriched in sphalerite compared to chalcopyrite in weakly metamorphosed VMS. Indium concentrations in sphalerite are up to 0.1 wt%. Indium, Mn, and Cd in sphalerite, and Bi in galena are homogenously distributed in trace element maps in two samples from greenschist and epidote-amphibolite facies metamorphosed deposits. Cobalt is observed to occur only at the rim of pyrite grains in the sample from the greenschist facies metamorphosed deposit, while in the sample which experienced higher metamorphic P and T, Co occurs only in the centre of pyrite grains. Germanium and W show a homogeneous distribution in pyrite. Tin is homogeneously distributed in chalcopyrite.

Rates of mineral reactions are controlled by two major factors: surface kinetics and element transport. Dissolution and precipitation of minerals in the presence of a hydrous fluid is assumed to occur predominantly by hydrolysis of the outermost charged monolayers of the reacting crystal and subsequent incorporation of atoms from ionic solutions into favorable sites at the product surface. Element transport during mineral reactions is commonly thought to occur via ionic solutions with the mineral solubility in the coexisting fluid being a rate limiting factor. Here we show in high-pressure/low temperature rocks that an alkali-Al-Si-rich amorphous material forms directly by depolymerization of the crystal lattice. Depolymerization starts along grain or phase boundaries, dislocation cores in the crystal lattice or lattice defects in general that serve as element exchange pathways and are also sites of porosity formation. High hydrogen concentrations in such dislocation cores within nominally anhydrous pyroxene has been confirmed by Nano-SIMS measurements and indicates hydrolysis and recrystallization within mineral grains. Element transfer in the alkali-Al-Si-rich amorphous material is thermodynamically decoupled from ionic solutions and therefore enables significantly higher element transport rates than previously thought. The resulting amorphous material occupies large volumes in an interconnected porosity network which has been documented in 3D imaging. Precipitation of product minerals occurs directly by repolymerization of the amorphous material at the product surface. This new dissolution-reprecipitation mechanism has major implications for the role of mineral reactions during geophysical and geochemical processes in the dynamic Earth.

The huge volumes and unknown composition of flowback and produced waters cause major public concerns about the environmental and social compatibility of hydraulic fracturing and the exploitation of gas from unconventional reservoirs. Flowback and produced waters contain not only residues of fracking additives but also chemical species that are dissolved from the shales themselves during fluid-rock interaction. Knowledge of the composition, size and structure of dissolved organic carbon (DOC) as well as the main controls on the release of DOC are a prerequisite for a better understanding of these interactions and its effects on composition of flowback and produced water. Black shales from four different geological settings and covering a maturity range Ro = 0.3-2.6% were extracted with deionized water. The DOC yields were found to decrease rapidly with increasing diagenesis and remain low throughout catagenesis. Four DOC fractions have been qualitatively and quantitatively characterized using size-exclusion chromatography. The concentrations of individual low molecular weight organic acids (LM-WOA) decrease with increasing maturity of the samples except for acetate extracted from the overmature Posidonia shale, which was influenced by hydrothermal brines. The oxygen content of the shale organic matter also shows a significant influence on the release of organic acids, which is indicated by the positive trend between oxygen index (OI) and the concentrations of formate and acetate. Based on our experiments, both the properties of the organic matter source and the thermal maturation progress of the shale organic matter significantly influence the amount and quality of extracted organic compounds during the leaching experiments.

The huge volumes and unknown composition of flowback and produced waters cause major public concerns about the environmental and social compatibility of hydraulic fracturing and the exploitation of gas from unconventional reservoirs. Flowback and produced waters contain not only residues of fracking additives but also chemical species that are dissolved from the target shales themselves. Shales are a heterogeneous mixture of minerals, organic matter, and formation water and little is actually understood about the fluid-rock interactions occurring during hydraulic fracturing of the shales and their effects on the chemical composition of flowback and produced water. To overcome this knowledge gap, interactions of different shales with different artificial stimulation fluids were studied in lab experiments under ambient and elevated temperature and pressure conditions. These lab experiments showed clearly that fluid-rock interactions change the chemical composition of the initial stimulation fluid and that geochemistry of the fractured shale is relevant for understanding flowback water composition. In addition, flowback water samples were taken after hydraulic fracturing of one horizontal well in Pomeranian region, Poland and investigated for their chemical composition. With this presentation, results from lab and field studies will be presented and compared to decipher possible controls on chemical compositions of flowback and produced water.