Search

Societal concerns about future hydroclimate changes urge a thorough understanding of the governing processes. Here, an analysis of Middle and Late Holocene speleothem-based hydroclimate reconstructions and paleoclimate model simulations reveals sub-millennial fluctuations in the spatiotemporal variability of precipitation in the European and Mediterranean regions, that complements previous dendrochronological and pollen-based reconstructions with an improved temporal resolution. Although insolation forcing is the primary driver of Holocene hydroclimate changes in Europe on a multimillennial scale, the evaluation of the principal component analysis of speleothem records and correlations with sea surface temperature data indicates that North Atlantic ocean circulation played a significant role in the sub-millennial variation of continental moisture transport, with an increasing importance during the Late Holocene. The combined evaluation of speleothem-based data, climate simulations and sea surface temperature records therefore advances our understanding of the governing processes of Holocene hydroclimate changes in the European and Mediterranean regions.

Fluids play a crucial role in element mobility and mass transfer at the slab-mantle interface in subduction zones. However, tracing the source and chemical composition of subduction zone fluids still remains challenging. High-pressure (HP) metamorphic leucophyllites, mainly composed of quartz, muscovite/phengite and Mg-chlorite, occur in several localities in the Eastern Alps and experienced significant Mg-metasomatism at forearc depths during the Eoalpine orogeny. They thus provide a good opportunity to explore the origin of Mg-rich fluids in the continental subduction zone. The leucophyllites are rich in Mg and poor in Fe, Na, and Ca and occur as lenses and layers in the country rocks of metagranites. Both leucophyllites and metagranites show similar whole-rock REE distribution patterns, and magmatic zircons from them exhibit similar U-Pb ages of ∼271 Ma, suggesting that both types of rock have the same protolith of early Permian granite. One metagranite that preserves magmatic composition shows a low δ26Mg value of −0.64‰, suggesting a contribution of carbonate-rich sediment when granitic melts were produced. A profile of samples from metagranite through transitional gneiss to leucophyllite in Hungary shows two trends in δ26Mg values. In the Vashegy sections, δ26Mg values firstly decrease from −0.64‰ to −1.30‰ during gneiss formation, and then increase to 0.29‰ during leucophyllite formation. In a second locality, the TV tower section, the δ26Mg values firstly decrease from −0.29‰ to −0.89‰ during gneiss formation, and then remain constant during leucophyllite formation. Two leucophyllites in Austria exhibit higher δ26Mg values of 0.05 to 0.09‰ compared to their country rocks of about −0.20‰. Based on the Mg isotope systematics and their relationships to whole-rock geochemical compositions, we propose two types of fluid in the subduction zone: (1) a low δ26Mg ( 0.3‰) fluid derived from dehydration of talc-rich serpentinite. This is for the first time to find subduction zone fluids with distinct δ26Mg values at forearc depths. Both fluids possibly originated from dehydration of the sediment-serpentinite melange at the slab-mantle interface. The fluids were heterogeneous in δ26Mg values and they metasomatized slices of continental crust along shear zones. The presence of fluids with δ26Mg values as low as −1.3‰ suggests that the dissolution of Mg-rich carbonates can be significant at forearc depths. Our results provide an excellent example of tracing different sources of subduction zone fluids by coupling Mg isotopes with other petrological and geochemical variables. They may also have great implications for the generation of magmas with variable Mg isotope compositions at convergent plate boundaries.

A stalagmitic flowstone deposit from the Beke Cave (called Nagy-tufa deposit), East-Central Europe is characterized by complex, climate related textural and geochemical records as documented from a drill core (BNT-2 core) covering the period of 4 to 1 ka cal BP. The core location was monitored in an earlier study. Based on monitoring, textural and chemical relationships, it has been hypothesized that the stable carbon isotope signal of the flowstone deposit is a regional humidity record, indicating wet periods 3.8 to 3.4, 3.0 to 2.8 and 2.0 to 1.6 ka cal BP, and a prominent dry period between 2.1 and 2.7 ka cal BP. Furthermore, stable H isotope data of inclusion-hosted water were used to reconstruct the atmospheric temperatures that fit independent regional paleotemperature records, indicating warm conditions around 2.7 ka BP and a relatively cold period between 2.5 and 1.5 ka BP. Comparisons with regional speleothem records and reconstructed North Atlantic Oscillation data indicate that the Late Holocene paleohumidity changes recorded by the BNT-2 stable carbon isotope record can be detected in the entire Western-Central European region with further links to the North Atlantic realm.

Natural CO2 reservoirs provide an opportunity to study long-term fluid-rock interactions, which are essential to reassure the safety of mineral storage of carbon-dioxide. The Mihalyi-Repcelak field (Pannonian Basin, Central Europe) is one of the largest natural CO2-bearing reservoirs in Europe (25 Mt). The CO2 was trapped in Neogene sandstones, which contain various carbonate minerals (dolomite, ankerite, siderite, dawsonite). To reveal the origin of the parent fluid, from which these minerals precipitated, dawsonite and siderite were separated by a new physical method to minimise the uncertainties in the analysis of their stable isotope composition. The δ13CDaw values range from +1.3‰ to +1.6‰ and the calculated δ13CCO2 values in equilibrium with dawsonite (−4.8‰ - –2.0‰) overlap with the carbon isotope compositions of the local CO2 and the European Subcontinental Lithospheric Mantle (−3.9‰ - –2.1‰). This indicates that the dawsonite-forming CO2 had a magmatic origin. The siderite data indicates that some formed from the magmatic CO2, possibly simultaneously with dawsonite (−6.0‰ - –3.9‰), whereas the rest (−8.4‰ - –6.1‰) formed either from a fractionated CO2 with magmatic origin or before the CO2 invasion. The hydrogen isotope composition of structural OH− of dawsonite (−57‰ to −74‰) was determined and was used to estimate the origin of the interacting porewater. The calculated porewater data (δD: −69‰ - –103‰ and δ18O: −1.4‰ - +4.7‰) indicate that the parent fluid was meteoric water modified by water-rock interaction. Our data allows estimation of the total amount of CO2 stored in the dawsonite-bearing sandstone reservoir to be 25 kg/m3, well in line with previous modelling works, which gives a total of 2.01 × 106 t of CO2, higher than previous estimates. We suggest that individual mineral analysis complemented by hydrogen isotope analysis is to be employed to effectively trace in-reservoir fluid-rock interactions in CO2 reservoirs and provide valuable input data for geochemical modelling for better predicting conditions for mineral storage of CO2.

This study introduces a novel approach intertwining analytics of spatial microbial distribution with chemical, mineralogical and (micro)structural related aspects in corroded concrete sewer environments. Samples containing up to 4 cm thick corrosion layers were collected from concrete manholes and analysed using hydro-geochemical, microbiological, biochemical and mineralogical methods. Opposed to the current opinion DNA and RNA indicating microbial activity were found throughout the entire deterioration layer down to the corrosion front. Elemental distributions of corresponding areas revealed a dynamic pH- and diffusion-controlled system in which a distinct succession of elemental accumulations was unequivocally correlated with responding pH levels, associated dissolution and precipitation of solids, as well as with the spatially resolved presence of microbes. Microbial activity further coincided with massive iron deposition zones, within the inner anoxic to anaerobic corrosion layers. As a possible microbial catalyst for iron oxidation and in-situ acid production in this zone, we propose Acidithiobacillus ferrooxidans which were isolated from the deteriorated concrete. Based on the data we propose a new model in which biogenic induced in-situ acid production is a decisive factor, steering high concrete corrosion rates of > 1 cm yr − 1 .

Studies on the last interglacial (LIG) can provide information on how our environment behaved in a period of slightly higher global temperatures at about 125 ± 4 ka, even if it is not the best analogue for the Holocene. The available LIG climate proxy records are usually better preserved and can be studied at a higher resolution than those of the preceding interglacials, allowing detailed comparisons. This paper presents complex stable hydrogen, carbon and oxygen isotope records obtained for carbonate (δ 13 C and δ 18 O carb ) and fluid inclusion hosted water (δD and δ 18 O w ) of a stalagmite from the Baradla Cave system in Central Europe that covers most of the LIG, as proven by U-Th dates. Comparing its C and O isotope data with records reported for other speleothem (cave-hosted carbonate) deposits from Europe revealed the complex behavior of these climate proxies, with a concerted relative increase in 18 O of carbonates from 128 to 120 ka and synchronized shifts in the opposite direction after 119 ka. The hydrogen isotope analyses of inclusion-hosted water extracted from the BAR-II stalagmite also correspond to the regional climate proxy records, with meaningful deviations from global temperature trends. Beside following the general paleotemperature pattern from the climate optimum (high δD values up to −64‰ around 120 ka) to the subsequent cooling starting at about 119 ka (low δD values down to −90‰ at about 109 ka), a period between 126.5 and 123 ka with low δD values (down to −81‰) is detected in the BAR-II stalagmite. Although the isotope shifts are muted in the C-O isotope data of carbonate due to competitive fractionation processes, the δ 13 C data show a positive relationship with the δD pattern, indicating humidity – and possibly temperature – variations. The periods with low δD values fit well to temperature and humidity changes inferred from proxy records from western Europe to the eastern Mediterranean. Spatial distributions of these variables show, that at about 125 ± 2 ka the Mediterranean region was characterized by warm, humid conditions and enhanced seasonality with elevated winter precipitation. The combined interpretation of stable isotope data revealed that the Alpine and Mediterranean regions behaved differently during Greenland Stadial 26 (GS26, ∼119 to 116.2 ka). While the Alpine records fluctuated in close agreement with the Central Greenland ice core δ 18 O data, the BAR-II stalagmite show a positive δ 18 O carb anomaly. The Baradla data indicate enhanced aridity and seasonality for a part of GS26, with the relative dominance of summer precipitation and Mediterranean moisture contribution. Following the GS26 event, the effect of long-term global cooling becomes dominant in the Baradla isotope records and leads to glacial inception at about 109 ka.

The Dachstein platform was an extensive carbonate platform developed on the westernmost shelf of the Neotethys during the Late Triassic, now preserved in various tectonic units disrupted during the Alpine orogeny. Despite being the focus of a multitude of sedimentological, paleontological and other studies, the demise of this platform remains controversial, with contrasting views on the timing and causes of cessation of its growth, the duration of the gap above, which at many places includes the Triassic-Jurassic boundary (TJB), and the depositional environment of overlying strata. Here we present new carbonate sedimentological, stable isotope and cyclostratigraphic data from sections in the Transdanubian Range (Hungary) which capture the termination of uppermost Triassic Dachstein Limestone and the onset of Hettangian (Early Jurassic) sedimentation following a hiatus. Previously, the TJB in the Transdanubian Range was regarded as a textbook case of a tectonically-driven platform drowning event or, alternatively, cessation of carbonate production due to emergence caused by a significant sea level fall at the TJB. However, recognition of global biotic change and environmental perturbations at the TJB calls for an assessment of their possible role in the demise of the Dachstein platform. Oxygen and carbon isotopic composition of bulk carbonates were measured in sections at Kőris-hegy (Bakony Mts.), Tata (Tata Horst), and Voroshid (Gerecse Mts.) Paleogeographically, these three sections represent a proximal to distal platform transect. Other sections at Pisznice and Tolgyhat (Gerecse Mts.) yielded additional sedimentological data. The sharp surface separating the Dachstein Limestone from the overlying Jurassic formations carries no or only minimal relief at outcrop scale. Thin section studies reveal small-scale irregularities, stylolites, microborings with ferruginous filling, or a thin clay-rich layer at the TJB, indicative of a submarine, or perhaps polygenetic, hardground. In the first meters of the lowermost Jurassic beds abundant ooids occur, and crinoids become common. In each of the studied sections, an abrupt negative carbon isotope shift is recorded at the TJB, and a gradual rebound to more positive values characterizes the lowermost Jurassic strata. Chemostratigraphy allows correlation with sections elsewhere. In the Transdanubian Range, the initial carbon isotope excursion and at least the first part of the purported main carbon isotope excursion are not preserved due to the gap at the TJB. Combined bio- and cyclostratigraphy of lowermost Jurassic strata permits an astrochronologic duration estimate of the early Hettangian hiatus that was not longer than a few hundreds of thousand years. Our results highlight the role of submarine erosion, perhaps partly related to acidification, and point to an abrupt change in carbonate production related to the end-Triassic extinction of several groups in the platform system. “Unreefing”, the ecological collapse of reefs, led to a regime shift, the transformation of the rimmed platform to a carbonate ramp, with a significant gap in production and preservation of carbonate sediment. This model is not uniformly applicable to Late Triassic platforms as several of them, unlike the Dachstein platform, survived with unrimmed architecture in the Early Jurassic elsewhere on the Neotethyan shelf. However, the model may explain features of the carbonate platform sedimentary record across other events with reef collapse.

The combined use of the stable isotope compositions of speleothem carbonate and inclusion-hosted water presents great potential in paleotemperature reconstructions, due to the various temperature-dependent isotope fractionations detected in cave systems and their environment. This paper evaluates the applicational possibilities of hydrogen and oxygen isotope measurements of inclusion-hosted water and its host calcite, in three different approaches: i) direct determination of calcite-water oxygen isotope fractionation by measuring inclusion water and carbonate compositions, ii) calculation of water oxygen isotope composition from hydrogen isotope data and of temperature from the inferred calcite-water fractionation, and iii) calculation of formation temperature from measured hydrogen isotope data and its temperature dependence in the modern precipitation water. Fluid inclusion oxygen and hydrogen isotope compositions as well as calcite oxygen isotope compositions were determined for five speleothem occurrences in Hungary. Although the background processes are not resolved, calculations involving measured calcite and water oxygen isotope compositions yielded unrealistic paleotemperatures, likely because of syn-formation isotope fractionation processes and diagenetic alterations. The hydrogen isotope data may yield realistic temperatures, provided that long-term isotopic composition - temperature relationships are known and the stable hydrogen isotope composition of the precipitation waters in the study area is temperature-controlled. Winter half-year and annual isotope-temperature relationships (δ2H/T gradients) were calculated using multidecadal isotope composition records from the Global Network of Isotopes in Precipitation (GNIP), gridded surface temperatures, and precipitation amounts from the E-OBS 21.0e database. The calculations yielded a paleotemperature record for the last ~250 ka, with average precisions ranging from ±0.6 °C for interglacial to ±2.4 °C for glacial periods. Clumped isotope analyses of cave-hosted flowstones support the inferred formation temperatures based on gradients, while detection of kinetic fractionations by combined hydrogen and oxygen isotope analyses of calcite and inclusion water lead to filtering clumped isotope (Δ47) data and more coherent Δ47-temperature relationships.

The end-Triassic extinction is one of the major Phanerozoic mass extinctions and it appears to have been linked to coeval rapid and severe environmental change, thought to be triggered by volcanism in the Central Atlantic Magmatic Province (CAMP). However, direct stratigraphic evidence to substantiate this linkage and to help develop scenarios for the cascade of events is still scarce. Mercury is an increasingly widely used proxy to trace the volcanic activity associated with large igneous provinces (LIPs) in distal sedimentary sections, but so far Hg records are available from only a handful of Triassic–Jurassic boundary (TJB) sections. One of the few well-studied marine sedimentary sections with a continuous sedimentary record across the TJB is located at Csővar (Hungary) and it exposes an extended succession of carbonates deposited in an intraplatform basin on the western Tethyan shelf. Previously, this section yielded one of the first convincing records of carbon isotope excursions (CIEs) across the TJB, albeit from low-resolution sampling. Here we report a new, high-resolution δ13Ccarb curve, supplemented with Hg measurements. A series of successive negative carbon isotope excursions (termed NCIE-1 to 6) attests to carbon cycle perturbations in the TJB interval. Four excursions appear significant after statistical smoothing. Of these, NCIE-3 exhibits the highest amplitude and is biostratigraphically constrained to the topmost Triassic, hence reliably correlated with the initial CIE, a globally recognised excursion closely preceding the TJB, and coincident with the end-Triassic extinction (ETE) horizon. The Hg concentration data provide the longest record available to date from a single section across the TJB. It shows very low values below NCIE-3 that are interpreted as the pre-volcanic background, followed by a prominent Hg peak that is nearly coincident with the most significant carbon isotope spike (NCIE-3). The slight lag suggests that onset of a major extrusive phase of CAMP (marked by a significant rise in Hg) closely followed the very onset of carbon cycle perturbation at that time (expressed by an abrupt change in the δ13Ccarb signal), possibly from biogenic methane release. Subsequent and recurring smaller Hg psuggest a pulsatory nature of prolonged volcanic activity. Organic content in the section is consistently low and sedimentary Hg concentrations are therefore normalized against Fe content, a reliable proxy in the lack of significant lithological changes. The maximum sedimentary Hg concentration at Csővar is greater than that in any other TJB section, although not unprecedented if other events are considered. Three hypotheses are explored to explain the high values; i) the hit-or-miss model could suggest that deposition of the sampled beds was fortuitously coincident with major eruptions, ii) the presence and preservation of cryptotephra could account for the unusually high sedimentary Hg enrichment, and iii) changes in the proportion of Hg-carrier phases throughout the studied succession, e.g. from magnetite to pyrite dominance, could have enhanced the potential of Hg capture and deposition. Collectively, the new data provide direct stratigraphic and geochemical evidence for the link between CAMP volcanism and carbon cycle perturbations and strengthen the case of their causal relationship with the end-Triassic extinction.

The Lower Triassic succession of the Transdanubian Range in Hungary comprises limestones, dolomite, marl, sandstones and siltstones, deposited in tidal flat, lagoon and ooid shoal environments on the marginal ramp of the western Neotethys. Seven cores were chosen for petrographic and stable isotope investigations aiming to reconstruct the paragenetic sequence with special regard to the dolomitization and hydrothermal events. Five lithotypes were differentiated: (i) dolomite, (ii) sandy, silty, clayey dolomite, and dolomarl, (iii), dolomitic siltstone and sandstone, (iv) dolomitic limestone, and (v) limestone. In these lithotypes, three types of dolomites are present: non-ferroan replacive, ferroan replacive, and ferroan cement. Fabric retentive and fabric destructive non-ferroan replacive dolomitization are interpreted to have occurred by seepage reflux. Supporting evidence includes the presence gypsum and anhydrite in the Lower Triassic beds. Stable isotope values of the ferroan dolomite (δ18O of −10.7 to −4.2‰ and δ13C of −4.8 to 4.7‰) suggest dolomitization by fluids of relatively high temperature. The similar stable isotope values (δ18O of −9.3 to −5.8‰ and δ13C of −1.9 to 2.5‰) of the non-ferroan dolomite phase suggest that the reflux dolomite was overprinted by this second dolomitization event. Traces of exotic minerals, such as barite, chalcopyrite, galena and sulphosalts were found as fillings of vugs and fractures in the dolomite-cemented sandstone. The metals could have been sourced from the underlying Permian red sandstone beds. The heterogeneous sediment composition had profound impact on the diagenesis of these sedimentary successions.

Degradation of concrete caused by the formation of secondary hydrous sulfate minerals (e.g. thaumasite, ettringite and gypsum) can cause serious problems concerning the durability of building structures. To provide a better understanding of the formation conditions of these sulfate minerals we have investigated thaumasite (Ca3Si(OH)6(CO3)(SO4)•12H2O), ettringite (Ca6Al2(SO4)3(OH)12•26H2O) and gypsum (CaSO4•2H2O) with the aim of extracting crystal (i.e. structural) water and analysing its stable O and H isotopes. The crystal water was released and collected using a heating and vacuum distillation method followed by δ2H and δ18O analyses on a liquid water isotope analyser. Results indicated that this setup is highly promising to trace the isotopic composition of water involved in the precipitation of the various hydrous sulfate mineral. Based on our data we calculated O and H isotope fractionation factors for thaumasite and ettringite between crystal and aqueous H2O. The results agree with previous findings that the sulfate mineral formation, responsible for concrete damage, is occurring in highly concentrated solutions (5000 up to 30000mg L-1 SO4) due to evaporation.

In addition to the collagen and phosphate components of bones and teeth, the stable carbon and oxygen isotope compositions of skeletal carbonate are frequently measured to determine diet, environmental conditions, and populational or individual migration in bioarchaeological research. A standardized method for the stable isotopic analysis of skeletal carbonate has not yet been established, despite the importance of these data. In this study, significant differences in the stable oxygen isotope values of bones and dental enamel were observed, which arose due to instrument- and methodology-based differences. The same target archaeological samples were analyzed in three laboratories, and the stable isotope analyses were supplemented by Fourier Transformation Infrared Spectroscopy (FTIR) measurements, which detected a strong OH− concentration-dependence in the stable oxygen isotopic shifts measured between the three laboratories. Laboratory experiments were conducted to quantify the effects of reaction temperature and phosphoric acid (H3PO4) concentration on the oxygen isotopic composition of carbonate, both of which resulted in significant, though smaller δ18O changes than the OH-related δ18O change. As such, we suggest that the δ18O values of bone structural carbonate should not be included in anthropological interpretation and that the analysis of tooth enamel should be conducted at 70 °C using 102% H3PO4, in order to make the results comparable. Furthermore, carbonated hydroxylapatite (CHAP) reference materials with varied isotopic compositions should be developed in the near future.

This paper presents stable C and O isotope data, as well as water contents and stable hydrogen isotope compositions of inclusion-hosted water of 230 Th-dated stalagmites collected from the Leany and Pal-volgyi Caves of Central Hungary, within and about 50 km NW from Budapest, respectively. A good replication of contemporaneous stalagmite oxygen isotope records and their agreement with the COMNISPA record from the Eastern Alps suggest that the stalagmite oxygen isotope variation reflects past climate change. H 2 O contents in the Leany stalagmite indicate a relationship with the oxygen isotope compositions and hence with climate conditions, raising the possibility of its use as a climate proxy in future studies. The stalagmites show strong negative δ 18 O excursions for two cold periods at about 5.4–6 and 8–9 ka, whereas the oxygen isotope data are relatively high in the period of 6–7 ka, indicating warmer conditions. The stalagmite hydrogen and d -excess series positively correlate with the COMNISPA record, interpreted as a sign of moisture source variations. High d -excess values in the periods of low δ 18 O data for the Leany Cave at about 5.4–6 and 8–9 ka suggest a shift to Mediterranean moisture source domination when the COMNISPA record indicate weaker North Atlantic Oscillation (NAO) activity. Lower d -excess values in the period of 6–7 ka are associated with low δ 18 O values in the COMNISPA record, corresponding to NAO+ phase. The inferred moisture source changes are in accordance with published instrumental data covering the last hundred years and atmospheric circulation model results, and demonstrate that NAO activity influenced the climate conditions of the Carpathian Basin during most of the Holocene.

The Basal Complex of Fuerteventura, in the Canary Islands, contains an ultra-alkaline complex formed by alkaline pyroxenites, melteigites, ijolites, alkaline gabbros, syenites and carbonatite dykes cut by a basaltic dyke swarm. A later basaltic magma, which formed a pyroxenite-gabbro pluton, intruded the entire series and caused a strong contact metamorphism and partial melting of the rocks near the contact. The anatexis appears in the form of “zebra rocks” in the contact-metamorphosed silicate rocks. Carbonatite dykes have been found in the metamorphic aureole and in the anatexite. Typical skarn mineralogy, including diopside, grossular-andradite garnet and vesuvianite, developed between the carbonatites and silicate rocks (e.g. ijolites, pyroxenites). In the metacarbonatites and skarns, the metamorphic paragenesis varies with the distance to the contact zone. The original igneous mineralogy disappeared completely in the anatectic zone, and a metamorphic association composed of wollastonite, monticellite, diopside, vesuvianite, garnet, calcite, perovskite, alabandite, pyrrhotite and Nb–Zr–Ca silicates (cuspidine–niocalite–baghdadite series) was formed. This paragenesis indicates that the carbonatites within the anatectic zone have undergone a thermal metamorphism under hornblende–hornfels facies (550–600 °C). Metamorphic reactions were also associated with the infiltration of F-rich aqueous fluids, which produced an intense metasomatism and caused Sr, Ba and S enrichment in the carbonatite. As a result, alkali elements such as K, Na, Rb or Th were leached and the remaining chemical elements were redistributed into the neoformed metacarbonatite paragenesis. Most of the metacarbonatites show significant C and O isotope deviations as compared with the primary isotopic compositions, due to fluid/rock interactions. The metacarbonatites with wollastonite have δ 13 C and δ 18 O values indicating CO 2 release, in agreement with devolatilization reactions that took place in the metacarbonatite and in the skarn. In addition, in the metacarbonatites with diopside, vesuvianite and garnet, a δ 18 O decrease relative to the primary isotopic compositions due to late fluid/rock interactions can be observed. The circulation of hot meteoric water fluids heated by the pyroxenite intrusion was responsible for the metamorphic-metasomatic reactions that caused the mineralogical, chemical and isotopic changes in the carbonatitic rocks and brought about skarn formation.

Four decades of U ore production in Hungary provides an opportunity to study the possible environmental effects of mining. The study reveals significant changes in chemical composition of a stalagmite (cave deposit). The good fit between U content changes in the studied deposit and the U ore production rate support the assumption of the relationship with mining activity. An independent chemoenviromental archive, living pine (Pinus sylvestis) trees were also investigated. Data on pine tree cores collected from the same region show different levels of pollution (Cu, Zn, Mn, U) after the 1950s and 1960s, linked to the opening of mines and subsequent dust fallout around the site. Elevated concentrations of detritally derived elements (Si, Al, Th) coupled with a rise in U concentration and change in δ234U values of the stalagmite suggest increasing amounts of mine-derived dust from 1 to 3 km distance that settled and washed into the karst system. The combined usage of different proxies not only provides historic records for the anthropogenic impact in the environment, but also allows the timing of U concentration increases within the stalagmite and the identification of elemental behavior from the pollution. This study shows that complementary geochemical archives such as stalagmites and tree rings used together can enhance understanding of past environmental contamination.

The petrography, mineralogy and geochemistry of two macroscopically distinct drill core samples of what was previously identified as a potentially diamondiferous kimberlitic rock from the Wekusko Lake area (central Manitoba, Canada) were examined in detail. The rock shows an inequigranular, uniform to segregation texture arising from the presence of abundant macrocrysts (partly or completely chloritized phlogopite, Mg–Al–Cr-rich spinel and Mg–Cr-rich ilmenite) and coarse-grained segregations in a fine-grained dolomitic groundmass (70–85% of the rock volume). The unmodified groundmass dolomite (3–22 mol% ankerite) is enriched in Sr, Ba, light rare-earth elements and shows a distinct “mantle” isotopic signature [δ 13 C V-PDB = − 7.6 to − 5.3‰; ( 87 Sr/ 86 Sr) i = 0.70348–0.70574]. Its consistently high δ 18 O V-SMOW values (20–25‰) indicate re-equilibration with low-temperature CO 2 -poor fluids. Phlogopite macrocrysts (mg# = 0.64–0.85, 8.8–14.9 wt.% Al 2 O 3 and 0.1–1.9 wt.% TiO 2 ) are cognate with the host rock and exhibit trace-element variation typical of carbonatitic micas ( 400 ppm Mn). Both spinel and ilmenite are compositionally indistinguishable from macrocrysts in kimberlites and interpreted to represent mantle-derived xenocrysts. The whole-rock compositions are characterized by elevated levels of compatible trace elements (30–110 ppm Co, 910–990 ppm Cr and 380–610 ppm Ni) and certain incompatible elements (most notably, Sr, light REE, Nb, Zr, Th and U), as well as high Nb/Ta, Zr/Hf and Ga/Al ratios (> 21, 48 and 7 × 10 − 4 , respectively). The most common accessory minerals are Na–Sr–REE-bearing fluorapatite and low-Hf zircon. With the exception of spinel and ilmenite macrocrysts, the mineralogy and geochemistry of the examined samples are inconsistent with their identification as kimberlite. On the basis of their modal, isotopic, major- and trace-element composition, the Wekusko Lake rocks are interpreted as primary magnesiocarbonatite contaminated by mantle-derived material and isotopically re-equilibrated with low-temperature crustal fluids.

Combined petrographical, mineralogical, geochemical and stable isotope analyses were conducted on an actively forming Egerszalok Travertine mound to determine the factors that govern carbonate precipitation and thus influence the use of travertines in paleoclimate reconstruction. Stable isotope analyses of oxygen, carbon and hydrogen demonstrate both biological and abiological factors to control travertine deposition. Processes of morphology-related outgassing had major effects upon isotopic composition. Continuous CO 2 degassing and temperature change of the thermal water between the spring orifice and distal parts of the system, caused stable carbon and oxygen isotope compositions of the precipitating travertines to increase (from + 2.7 to + 4.3‰ relative to V-PDB and from + 10.5 to + 14.7‰ relative to V-SMOW, respectively). The travertines at the spring orifice ( T ∼ 67 °C) are composed of almost pure calcite with a δ 13 C value of + 2.7‰ (relative to V-PDB) enabling classification as intermediate between thermometeogene and thermogene. In lower temperature water, away from the spring orifice, various amounts of aragonite (5–35%) with higher Sr concentrations precipitate from solution. This phenomenon is exceptional in hot spring carbonate deposits and could be explained by fast carbonate precipitation due to the morphology-related outgassing. Oxygen and hydrogen isotope measurements of the thermal water confirmed evaporation to be causing limited kinetic isotope fractionation. However, δ 18 O values of the travertine do show isotope shifts away from the equilibrium fractionation curve, which is most probably related to the rapid calcite precipitation and transportation along the flow path. Our data closely follow the temperature–Δ 18 O calcite–water relationship observed for other travertine localities. This is slightly displaced from the experimental curve and determines an empirical ‘travertine curve’. Our study shows that this shift may result in an approximately 8 °C difference in paleotemperature calculations depending upon which fractionation curve is used.

Carbonate xenoliths containing olivine and rimmed by kaersutitic amphibole were collected in basaltic rocks of the Basal Complex of La Palma. The mineralogical composition and microscopic appearance may suggest a relationship with carbonatites in general, thus a major element, trace element and stable isotope study was conducted to investigate the origin of the carbonate formation. Based on electron microprobe analyses, the carbonate is calcite with up to 6.3 wt% MgO and 7.2 wt% SiO 2 . The elevated SiO 2 content may suggest a melt origin for the carbonate. However, the C and O isotope compositions of the carbonate xenoliths (δ 13 C and δ 18 O around −1‰ and 13‰, respectively) are similar to those of calcite veins and amygdales in basaltic rocks of the Basal Complexes of La Palma and Fuerteventura and are interpreted as produced by fluid degassing and metasomatism by CO 2 –H 2 O fluid derived from mobilization of sedimentary material. Trace element contents determined by laser-ablation ICP-MS analyses support the assumed origin, thus, the relationship with carbonatitic melts can be excluded. Based on trace element compositions, the amphibole surrounding the xenoliths is not related genetically to the carbonate. The elevated SiO 2 content of the calcite can be attributed to submicron relics of pyroxene, thus, the use of this feature as an evidence for melt origin is questionable.

Metamorphosed carbonatites, located in the Basal Complex of Fuerteventura, Canary Islands (Spain), contain unusual Ca-Nb-Zr disilicates. These mineral phases appear in different textural situations that have very different chemical compositions. More widespread Ca-Nb disilicates with minor Zr contents cover the whole range of cuspidine–niocalite solid solution. Disilicate crystals containing more Zr always have Nb, too, and can be described as members of the cuspidine–niocalite–baghdadite ternary solid solution. The crystals richest in Zr have intermediate compositions between niocalite and baghdadite. All of the analyzed crystals have very high Sr contents (between 0.05 and 0.30 a.p.f.u.) and very low Na contents in substitution of Ca compared to the composition of the cuspidine group minerals from diverse paragenesis. The Ca-Nb-Zr disilicate crystals were formed by metamorphic and metasomatic recrystallization of zircon and pyrochlore crystals, which are very frequent in the igneous carbonatites of Fuerteventura, due to the increase in temperature around the ultramafic intrusion of the Pajara pluton and the circulation of F, S and H 2 O-rich high temperature fluids. Zr-rich minerals of the cuspidine–niocalite solid solution and crystals belonging to the baghdadite–niocalite solid solution as described in the Fuerteventura metacarbonatites have not been reported previously from any other paragenesis and are considered to represent new members of the cuspidine–lavenite group.

The Eden Lake pluton in the Trans-Hudson Orogen is the first known occurrence of carbonatites in Manitoba. The pluton is largely made up of modally and geochemically diverse syenitic rocks derived from postorogenic magma(s) of shoshonitic affinity. Their diversity can be accounted for by a combination of crystal fractionation and fluid release in the final evolutionary stage (crystallization of quartz alkali-feldspar syenite). At Eden Lake, carbonatites, represented predominantly by coarse-grained massive to foliated sovite, occur as branching veins and lenticular bodies up to 4 m in thickness showing crosscutting relations with respect to all of the syenitic units. The host rocks are intensely fenitized at the contact, and there is also abundant mineralogical and textural evidence for assimilation of silicate material by carbonatitic magma through wallrock reaction and xenolith fragmentation and digestion. The bulk of the carbonatites are composed of (in order of crystallization): Sr–REE-rich fluorapatite, aegirine–augite, and coarse calcite crystals surrounded by fine-grained calcite (on average, ∼ 90 vol.% of the rock). Noteworthy accessory constituents are celestine, bastnasite-(Ce) (both as primary inclusions in calcite), Nb–Zr–rich titanite, low-Hf zircon, allanite-(Ce) and andradite. The calcite is chemically uniform (Sr-rich, Mg–Mn–Fe-poor and low in 13 C), but shows clear evidence of ductile deformation and syndeformational cataclasis. Geochemically, the carbonatites are enriched in Sr, Ba, light rare-earth elements, Th and U, but depleted in high-field-strength elements (particularly, Ti, Nb and Ta). The stable-isotope composition of coarse- and fine-grained calcite from the carbonatites and interstitial calcite from syenites is remarkably uniform: ca. − 8.16 ± 0.27‰ δ 13 C (PDB) and + 8.04 ± 0.19‰ δ 18 O (SMOW). The available textural and geochemical evidence indicates that the Eden Lake carbonatites are not consanguineous with the associated syenites and may have been derived from a Nb–Ti-retentive and 13 C-depleted source such as the subducted crustal material underlying the Eden Lake deformation corridor.

Processes and causes of biotic and environmental change at the Triassic–Jurassic transition remain controversial, partly because of a scarcity of Triassic–Jurassic boundary sections studied in detail. Continuous marine strata spanning the boundary are exposed at Csővar, Hungary, where new integrated stratigraphic data were obtained from multidisciplinary investigations to help reconstruct the end-Triassic and Early Jurassic events. Boundary strata are predominantly slope to basinal carbonates deposited in a periplatform basin. The position of the system boundary is constrained by radiolarian, foraminiferan, conodont and ammonoid biostratigraphy. Pronounced radiolarian turnover is observed between assemblages assigned to the Late Rhaetian Globolaxtorum tozeri zone and the Early Hettangian Canoptum merum zone. Benthic foraminifera suffered lesser extinction. Successive conodont faunas of the latest Rhaetian Misikella posthersteini and Misikella ultima zones record a marked drop in diversity and abundance but sporadic survivors persist into the earliest Hettangian. The extinction is also recorded in a reduction of biogenic components in carbonates. Decline of benthic and planktic biota is followed by a negative δ13Ccarb excursion of up to − 6‰ that is composed of short-term fluctuations revealed by dense sampling. Carbon and oxygen isotope ratios are positively correlated in the lower part of the section and appear to reflect primary variations. Drivers of the stable isotope trends are interpreted as warming in excess of + 10 °C and concomitant episodic, short-term perturbations of the global carbon cycle, possibly due to methane release from gas–hydrate dissociation induced by rapid climatic events. The main biotic and isotopic events occurred within a single sedimentary cycle but sea-level does not appear to have exerted a critical influence on these changes. The Triassic–Jurassic boundary crisis appears a short but not instantaneous event.

Complete, continuous marine Permian–Triassic (P–T) boundary sections in the Bukk Mountains, Northern Hungary, represent a ramp setting on the margin of the western Tethys. The Upper Permian succession comprises limestone rich in calcareous algae, foraminifera, and skeletal fragments of metazoans. A significant reduction of biogenic components occurs in the topmost limestone layers below the “boundary shale bed” (BSB). It coincides with the beginning of a gradual negative shift in δ 13 C carb values that continues into the BSB. The BSB consists predominantly of marly siltstones that are similar to the insoluble residue of the underlying limestone. A second biotic decline is recorded in the upper-third of the BSB, where the continuous negative shift in δ 13 C values is superimposed by a sharp and quasi-symmetric negative peak. The δ 13 C peak is confined to the shale bed and is not correlated with the lithological change, therefore diagenetic or other secondary effects are ruled out. The carbon isotope signal reflects primary processes related to significant changes in environmental conditions. Correlation and comparison of sedimentological, biotic, geochemical and mineralogical features of the studied sections in the Bukk Mountains with other Tethyan P—T sections in the Southern Alps, Dinarides, Iran, Kasmir (India) and southern China are discussed. The continuous shift in δ 13 C values is most probably related to a decrease in bioproductivity, whereas the sharp peak is attributed to an addition of C strongly depleted in 13 C isotope to the ocean–atmosphere system. The most plausible model is a massive release of methane from gas–hydrate dissociation. This event led to the extinction of the already impoverished biota. Scarcity of metazoans and prolonged unfavourable environmental conditions gave rise to a bloom of microbial communities. Mineralogical and geochemical analyses failed to reveal any evidence for extraterrestrial effects or synchronous volcanism were found in the studied sections.

Several Permian–Triassic boundary sections occur in various structural units within Hungary. These sections represent different facies zones of the western Palaeotethys margin. The Gardony core in the NE part of the Transdanubian Range typically represents the inner ramp, while the Balvany section in the Bukk Mountains of northern Hungary represents an outer ramp setting. The two sections have different patterns for their δ13C values. The Balvany section shows a continuous change towards more negative δ13C values starting at the first biotic decline, followed by a sharp, quasi-symmetric negative peak at the second decline. The appearance of the δ13C peak has no relationship to the lithology and occurs within a shale with low overall carbonate content, indicating that the peak is not related to diagenesis or other secondary influences. Instead, the shift and the peak reflect primary processes related to changes in environmental conditions. The continuous shift in δ13C values is most probably related to a decrease in bioproductivity, whereas the sharp peak can be attributed to an addition of C strongly depleted in 13C to the ocean–atmosphere system. The most plausible model is a massive release of methane-hydrate. The quasi-symmetric pattern suggests a rapid warming–cooling cycle or physical unroofing of sediments through slope-failure and releasing methane-hydrate. The Gardony-1 core shows a continuous negative δ13C shift starting below the P–T boundary. However, the detailed analyses revealed a sharp δ13C peak in the boundary interval, just below the major biotic decline, although its magnitude doesn't reach that observed in the Balvany section. Based on careful textural examination and high-resolution stable isotope microanalyses we suggest that the suppression of the δ13C peak that is common in the oolitic boundary sections is due to combined effects of condensed sedimentation, sediment reworking and erosion, as well as perhaps diagenesis.

Carbonate globules have been found in amphibole-bearing glass veins of peridotite xenoliths from Szentbekalla (Balaton Highland, Central Hungary). Strong resorption of amphibole suggests multiple fluid-melt infiltration. Textural features of carbonate globules and the surrounding silicate glass indicate a magmatic melt origin for the carbonate and exclude the possibility of significant alteration. The application of the cpx structural barometer for clinopyroxenes formed in the silicate glass indicates high-pressure vein formation. Laser-ablation ICP-MS analyses revealed trace element zoning within the carbonate. Uniform profiles observed for various elements within the carbonate indicate that the zoning is related to non-diffusive mixing during carbonate–silicate interaction rather than to element diffusion. The trace element composition of the centers of the globules (e.g. low Ce/Pb and Nd/Pb ratios) suggests a crustal origin for the carbonate melt. The C, O, and Sr isotope compositions of the calcite globules (13C about ?14‰; 18O about 22‰; 87Sr/86Sr=0.70533) also argue for a crustal origin of the carbonate melt. Trace element and C–O–Sr isotopic compositions of calcite globules suggest that the carbonate melt was derived from subducted material. Injection of the carbonate melt into the peridotite triggered amphibole melting. The carbonate and silicate melts intermingled, but their interaction was confined to the margins of carbonate globules. Preservation of trace element zoning and element diffusion calculations indicate that the vein-hosting peridotite was rapidly brought to the surface after the carbonate melt injection.

The origin of low δ18O values for ocean island basalts (OIBs) is debated as such low values have been taken as evidence for melt contamination by altered oceanic crust with low δ18O values or for the involvement of altered and subducted oceanic crust during melting at mantle depths. For the submarine–subaerial Transitional Volcanic Group of Fuerteventura (Canary Islands, Spain) low δ18O values (4.8±0.3‰) measured for phlogopite and amphibole megacrysts with close-to-HIMU Sr–Nd–Pb isotope characteristics are interpreted to be primary and, on the basis of hydrogen isotope compositions, exclude the influence of crustal assimilation. The model that best describes the chemical and H–O–Sr–Nd–Pb isotope compositions of these minerals favours melting of subducted ocean crust in the OIB source as a cause of low δ18O values. Low δD values of −115±4‰ have been measured for amphibole megacrysts and are attributed to preceding phlogopite crystallization from a fluid-rich magma. However, phlogopites with close-to-HIMU Sr–Nd–Pb isotope ratios are also depleted in deuterium relative to upper mantle compositions with δD values of −96±1‰, which may be regarded as the pristine H isotope composition characteristic for plume material.

In the Late Triassic, a large carbonate platform system came into existence in the Transdanubian Range (TR) producing a 1.5- to 2-km-thick carbonate succession. The lower part of the platform carbonate series is made up of cyclic peritidal dolomite (Main Dolomite Formation), while the upper one consists of cyclic peritidal limestone (Dachstein Limestone Formation). However, there is a transitional member of remarkable thickness between them consisting of partially dolomitised limestone and calcitic dolomite. This study focuses on the transitional member where the process of early dolomitisation was halted at various stages. In the investigated sections the early dolomitisation was controlled by the climate and high-frequency sea-level oscillation, which led to periodic subaerial exposure of large areas and palaeo-hydrological conditions. Increasing humidity and gradual extension of the permanently inundated outer platform led to cessation of early dolomitisation in the Middle to Late Norian.

The 370–380 Ma Khibina and Vuoriyarvi complexes on the Kola Peninsula, Russia, which form part of the Palaeozoic Kola Alkaline Province, contain REE-rich carbonatites with burbankite (Na,Ca)3(Sr,Ca,REE,Ba)3(CO3)5 or calcioburbankite (Na,Ca)3(Ca,Sr,REE,Ba)3(CO3)5 as the principal primary REE mineral. Within each complex the C–O and Sr–Nd isotopic data are similar for burbankite group minerals and co-existing calcite or dolomite (Khibina: δ13C(V-PDB)=−6.4 to−5.8‰, δ18O(V-SMOW)=7.3–7.7‰, (87Sr/86Sr)370=0.70390–0.70404 and (143Nd/144Nd)370=0.51230–0.51235; Vuoriyarvi: δ13C=−4.2 to −3.0‰, δ18O=8.1–9.4‰, (87Sr/86Sr)370=0.70313–0.70315 and (143Nd/144Nd)370=0.51243–0.51245). This indicates that the REE mineralization and its host carbonatites in each complex are derived from the same source and are co-genetic. There is, however, a great difference between the Sr, Nd and C isotopic signatures from Khibina and Vuoriyarvi, whereas the δ18O ranges are similar. This suggests that the REE carbonatites of the two complexes originate from sources with different isotopic signatures. At least three mantle components are needed to explain the variations in Sr and Nd compositions in the carbonatites from Kola. The δ13C ranges of primary carbonatites with low δ18O values are quite different for Khibina and Vuoriyarvi and show correlation with the radiogenic isotope compositions. The data may be best explained by subduction-related source contamination that caused δ13C variations in different mantle components. During late-stage processes burbankite and calcioburbankite have been replaced by various assemblages of REE–Sr–Ba minerals. The alteration of burbankite group minerals is an open-system hydrothermal process leading to multiple element transfer. It has produced mineral assemblages which are characterized by high δ18O values (Khibina: δ18O(V-SMOW)=11.4–13.9‰ and Vuoriyarvi: δ18O=17.1–18.0‰) compared to primary burbankite and calcioburbankite. Co-existing calcite and dolomite have retained their original C and O isotope compositions, and one calcite sample from Khibina shows strong positive δ13C–δ18O shifts similar to those of the pseudomorph. The high δ18O and sometimes high δ13C values can be attributed to low-temperature isotope exchange between minerals and fluid with variable CO2/H2O ratio taking place during and/or after crystallization as usually observed in carbonatites. The Sr and Nd isotope compositions of pseudomorphs and associated calcite/dolomite in general are identical to those of burbankite/calcioburbankite and associated carbonates suggesting that the fluids which caused burbankite alteration are from the same source, i.e. carbonatitic. Small variations in the Sr and Nd isotope signatures point to interaction of the pseudomorph-forming fluid with alkali silicate wall rocks.

Fuerteventura—the second largest of the Canary Islands consists of Mesozoic sediments, submarine volcanic rocks, dike swarms and plutons of the Basal Complex, and younger subaerial basaltic and trachytic series. Carbonatites are found in two Basal Complex exposures: the Betancuria Massif in the central part of the island and the Esquinzo area in the north. δ 13 C values of the carbonatites increase progressively from south to north of the island. This phenomenon is attributed to different degrees of assimilation of sedimentary carbonate. Homogeneous, typically magmatic δ 18 O values for carbonatites which have preserved primary igneous textures and minerals suggest a well-mixed reservoir where changes in δ 13 C values result from the storage of carbonate magmas at different structural levels. The magma storage allowed assimilation of sediment to varying degrees before final emplacement of carbonatites. Shifts in δ 18 O towards more positive and negative values from presumed primary compositions are observed in the carbonatites. On the basis of the oxygen isotope compositions of calcite, mica and K-feldspar, and the hydrogen isotope compositions of micas, the changes in the δ 18 O values of the carbonatites can be related to fluid/rock interactions.

Organic, inorganic and isotope geochemical investigations have been performed on 25 samples - 20 laminated marl samples and 5 re-sediment samples - taken from a 27m thick black shale section of early Toarcian age, cropping out in the Northern Calcareous Alps. On the basis of MnO, Fe, organic carbon (TOC) contents and Hydrogen Index (HI) values, the laminated marls of the section can be divided into two parts. TOC contents and HI values are below 2% and 500 mg HC/g TOC in the lower, Mn-rich (and Fe-rich) part (MnO between 2 and 16%, Fe between 3.9 and 6.4%), while they range between 5 and 9% and 600-700 mg HC/g TOC, respectively in the upper, Mn-poor (and Fe-poor) part (MnO < 1%, Fe between 1.5 and 3.8%). Both original amount of organic carbon (TOC or ), calculated from TOC, MnO and sulphur contents, and CaO concentration show a strong upward increase in the lower, Mn-Fe-rich part of the section. TOC or and CaO are believed to represent planktonic particles hence their simultaneous upward increases are interpreted as the result of an at least 2.5 fold increase of productivity during the first part of the black shale event. Following the same logic, in the second part of the black shale event productivity is believed to have slightly decreased from the previously reached high level. Stratigraphic variation of the sulphur isotopic ratio support this scenario. Comparison of organic geochemical and δ 34 S data of the re-sediments with those of the neighbouring marls suggests that increase and decrease (?) of productivity was paralleled by expansion and withdrawal of oxygen-depleted waters. During the black shale event the extent of the oxygen-depleted bottom water was governed by changes in intensity of productivity. Changes in rates of deposition of Mn and Fe were not related to those of the productivity but they deeply influenced nature and intensity of bacterial degradation of organic matter and especially the incorporation of sulphur into kerogen. The high contribution of Mn- and Fe-minerals in the case of the lower Mn-rich part prevented by both dilution and degradation of OM due to Mn-reduction an intense incorporation of sulphur into OM. In the upper, Mn- (and iron) poor part the high initial C org /Fe ratio led to an important incorporation of sulphur into OM and an early termination of sulphate reduction.

About 60 samples from the non-bioturbated Urkut Manganese Ore Formation (Bakony Mountains, Hungary), representing the early Toarcian anoxic event, were studied for: (1) TOC content, Rock-Eval parameters and kerogen δ 13 C; (2) S content and δ 34 S and (3) Al, Ca, Mn, Si and Ti contents. Using the example of the formation, a novel approach for estimating paleoproductivity is presented, taking into account reduced sulphur and manganese contents, which reflect the amount of organic carbon lost during early burial. Drastic changes in Mn content (between 0.7% and 37%) during deposition of the formation resulted in very variable early diagenetic processes, with sulphate reduction dominating in low-Mn sediments, and Mn reduction dominating in high-Mn sediments. The amounts of reduced sulphur and manganese allowed calculation of the original organic carbon (TOC or ) content throughout the formation. Based on stratigraphic variations in chemical composition, changes in the rate of sedimentation were assessed for the three main members of the formation. Next, using the formula describing the relationship between measured productivity, rate of sedimentation and carbon flux reaching the sea-floor, developed by Suess (1980) , past productivity was calculated. The values obtained, lower than those prevailing in present-day upwelling systems, are probably underestimated because of uncertainties of chronostratigraphic and water-depth data. However, relative differences between productivity values obtained for the three members are considered as realistic and suggest an increase in productivity during deposition of the formation. This increase is not related to stratigraphic variations in Mn content and is accompanied by an increase in the growth of calcareous plankton.

The Rechnitz Window is the easternmost Penninic window of the Alps and the only one that is partly covered by Neogene sediments. Zircon and apatite fission-track ages have been measured on the Penninic metasediments of the Rechnitz series to better understand the exhumation of the window at the Alpine-Pannonian border. The zircon FT ages range from 21.9 to 13.4 Ma, similar to the white mica K/Ar ages (19 and 23 Ma). The exhumation rate during the Early Miocene extension was high (∼40°C/Ma). Apatite samples display FT ages of 7.3 and 9.7 Ma, thus the cooling rate was significantly less (7–11°C/Ma) during the post-rift uplift uplift in Late Miocene-Pliocene than in the Early Miocene escape period. Zircon FT ages decrease eastward due to the gradual southeastward slide of the Austroalpine cover along low-angle normal faults. The exhumation of the Rechnitz metamorphic core complex is younger than the unroofing of the eastern Tauern Window. Morphology of detrital zircon crystals of the Penninic metasediments was used for the differentiation of tectonic subunits and to trace the internal structure of the window. One population was probably derived from undifferentiated calc-alkaline granitoids and tholeiitic granitoid sources, while the other derived from evolved calc-alkaline granitoids and alkaline granitoids of anorogenic complexes. The areal distribution of zircon populations is in harmony with the eastward shift of zircon cooling ages. These data indicate the exhumation of deep levels of Penninic metasediments in the centre of the window.

Processes of carbonate formation have been related to C and O isotopic compositions in the Mesozoic alkali basalt (Mecsek Mts.) and lamprophyre (Transdanubian Range) suites of Hungary. In the studied magrnatic rocks, carbonates are present as ocelli, amygdales, xenoliths, veins and groundmass carbonate. C and O isotope studies of these types of carbonate have yielded information on the origin of the carbonates and indicated the following processes of formation that determined the δ13C and δ18O values of the carbonates:(1)Crystallization of magmatic carbonate. Textural characteristics and δ13C values suggest formation of magmatic carbonate in alkali basalt and lamprophyre dikes, whereas the δ18O compositions of these carbonates indicate low temperature oxygen isotope exchange with magmatic fluids.(2) Assimilation of sedimentary carbonate by silicate magmas. Even completely recrystallized amygdales and ocelli of basalts and lamprophyres have preserved their sedimentary δ13C values. In contrast, variations in the extent of mobilization and isotope exchange with magmatic fluids are reflected in differences in the ranges of the δ18O values of amygdales, ocelli and veins, and can be attributed to different amounts of fluids involved in the magmatic events.(3) Low temperature alteration of magmatic rocks caused only 18O-enrichment in the carbonate amygdales of basalts and the groundmass carbonates of lamprophyres, indicating that no externally-derived CO2 was present in the alteration fluids.(4) Degassing of magma and magmatic fluid. Correlations between δ13C and δ18O data, magma crystallization depths and amygdale sizes in the alkali basalts suggest that CO2 degassing has been responsible for the negative δ13C and positive δ18O shifts observed. A similar trend was found in the lamprophyres, but the extent of the δ18O shift indicates that in these rocks H2O degassing also played an important role.

After conversion of water to H2 gas with zinc for DH ratio determination, hydrogen gas can be absorbed by the zinc during cooling, resulting in H isotope fractionation. Thermal release and subsequent DH ratio determination of hydrogen bound to zinc revealed that the fractionation between the bound H and the H2 gas is extremely large with an empirical α-value of ∼ 1.62. Differences in the fractionations observed using stopcock-sealed vessels and break-seal tubes indicate that the conversion method and H2Zn ratios should be the same for both samples and standards. The effect of hydrogen absorption can be eliminated (or lowered) by re-heating the zinc during transfer of hydrogen gas into the mass spectrometer. For measurement of hydrogen isotope composition of geological samples with varying and sometimes unpredictable water content (e.g., fluid inclusions of minerals) recording a calibration curve of varying water/zinc ratios and δD-values is proposed.

Based on 13 published porewater H 2 S and sulphate profiles the amount of H 2 S escaping from non-bioturbated shales varies between some few % to 45% of the amount of bacterially generated H 2 S. This finding permits calculation of the original organic carbon (TOC or ) content of immature nonbioturbated shales using TOC and sulphur content data. In two immature non-bioturbated sequences from Hungary (Toarcian and Oligocene) the first-order correlation between HI and TOC/TOC or was found to be stronger than that between HI and TOC, indicating that sulphate reduction was the leading process both in decrease in TOC content and degradation of kerogen source potential.