László Palcsu

CO ₂ degassing from the deep Earth provides important insights into the global carbon cycle. CO ₂ ‐rich fluid inclusions in mantle xenoliths record fluid sources and migrations in the deep lithosphere, while the contribution of mantle components in groundwater can be traced via dissolved gas geochemistry. Here, we integrate basin‐scale geochemical observations with thermo‐kinematic modeling to reconstruct CO ₂ release in the Neogene Carpathian–Pannonian continental back‐arc system. He‐Ne isotope ratios were determined from mantle xenoliths studied in detail by fluid inclusion analyses, collected from the Styrian Basin ( R _c / R _a = 5.8–6.8), Bakony–Balaton Highland ( R _c / R _a = 6.1–7.3) and Perşani Mountains Volcanic Fields ( R _c / R _a = 2.3–5.3). This was compared with groundwater data from the same areas using previous studies and new data from the Bakony–Balaton Highland ( R _c / R _a = 1.0–2.1 and δ ¹³ C = −9.60‰ to −6.24‰). Considering the inferred genetic connection of deep fluids and groundwater, the results on mantle degassing can be extrapolated and modeled to recent times owing to the same geodynamic setting prevailed during xenolith transport to the surface. Continuous crystallization of CO ₂ ‐bearing, non‐extractable melts within the asthenosphere results in gradual release of CO ₂ during post‐rift lithospheric thickening. This mechanism is supported by numerical analysis of melting, melt extraction and mantle degassing over time, demonstrating that persistent post‐rift CO ₂ release until today is physically plausible. This mechanism provides a reasonable explanation for the widespread occurrence and longevity of non‐volcanic CO ₂ emissions far from areas of active volcanism in the Carpathian–Pannonian region and in analogous post‐rift tectonic environments worldwide.

The investigation of complex karst systems has always been a difficult task for hydrogeologists, especially related to the spatial position of karst channels. The city of Pirot, which is located in southeastern Serbia, taps karst water for water supply from three karstic springs (Kavak, Krupac and Gradište), which are characterized by extremely good and stable groundwater regime and quality. According to the general water regime, it can be concluded that in addition to the development of shallow and large karst conduits (as proven by tracer tests), there are also deeper karst channels, in which water circulates very slowly and remains for much longer. In order to understand the genesis and characteristics of karst springs used for water supply, multi-parameter research was conducted, which, in addition to monitoring the yield on a daily basis, also included detailed hydrochemical research together with an analysis of microelements and stable and radioactive isotopes. Water from springs has a stable hydrochemical composition highlighting prolonged contact with the host rock. Isotopic analysis showed that the water is a mixture of young waters (residing in the system for a few days, as determined by tracer tests); semi-young waters that, based on the radioactive isotopes ³T and ³He, have resided in the system for 53 years; and very old waters that have spent more than 3000 years in the system. Finally, such new data on significant dynamic as well as static reserves of quality drinking water are of particular importance for long-term sustainable water utilization.

The 11‐year cycle of the solar activity affects the production rate of cosmogenic isotopes. For tritium in precipitation, it has been just recently proven that this link exists. Here we show, for the first time, a tritium ice core time series which extends back to 1923, covering a time period that avoids the presence of artificial tritium from the thermonuclear weapon tests of the early 1950s. Accurate analyses of low‐level tritium enables us to estimate the natural level of tritium in the study site of Colle Gnifetti, Swiss‐Italian Alps, as well as its variation. Statistical analyses using sunspot number and the count rate of cosmic ray secondary neutrons have confirmed that the modulation of the solar activity does affect the tritium concentration of ice layers accumulated earlier than the first hydrogen bomb tests. The tritium level of the ice, as well as in precipitation, is still slightly decreasing during the last three decades. The natural level of tritium obtained in this work fits very well to early tritium analyses of European wine samples, as well as model calculations with the isotope‐enabled atmospheric general circulation model MIROC5‐iso. Further sensitive tritium analyses of ice cores around the world will provide the opportunity to validate these models.

The end‐Triassic extinction (ETE) is one of the most severe biotic crises in the Phanerozoic. This event was synchronous with volcanism of the Central Atlantic Magmatic Province (CAMP), the ultimate cause of the extinction and related environmental perturbations. However, the continental weathering response to CAMP‐induced warming remains poorly constrained. Strontium isotope stratigraphy is a powerful correlation tool that can also provide insights into the changes in weathering regime, but the scarcity of ⁸⁷Sr/⁸⁶Sr data across the Triassic‐Jurassic boundary (TJB) hindered the use of this method. Here we present new high‐resolution ⁸⁷Sr/⁸⁶Sr data from bulk carbonates at Csővár, a continuous marine section that spans 2.5 Myrs across the TJB. We document a continuing decrease in ⁸⁷Sr/⁸⁶Sr ratio from the late Rhaetian to the ETE, terminated by a 300 kyr interval of a flat trend and followed by a transient increase in the early Hettangian that levels off. We suggest that the first in the series of perturbations is linked to the influx of non‐radiogenic Sr from the weathering of freshly erupted CAMP basalts, leading to a delay in the radiogenic continental weathering response. The subsequent rise in ⁸⁷Sr/⁸⁶Sr after the TJB is explained by intensified continental crustal weathering from elevated CO₂ levels and reduced mantle‐derived Sr flux. Using Sr flux modeling, we also find support for such multiphase, prolonged continental weathering scenarios. Aggregating the new data set with published records employing an astrochronological age model results in a highly resolved Sr isotope reference curve for an 8.5 Myr interval around the TJB.

The end-Triassic extinction (ETE) is one of the most severe biotic crises in the Phanerozoic. This event was synchronous with volcanism of the Central Atlantic Magmatic Province (CAMP), the ultimate cause of the extinction and related environmental perturbations. However, the continental weathering response to CAMP-induced warming remains poorly constrained. Strontium isotope stratigraphy is a powerful correlation tool that can also provide insights into the changes in weathering regime but the scarcity of 87Sr/86Sr data across the Triassic-Jurassic boundary (TJB) compromised the use of this method. Here we present new high-resolution 87Sr/86Sr data from bulk carbonates in Csővár, a continuous marine section that spans 2.5 Myrs across the TJB. We document a continuing decrease in 87Sr/86Sr the from the late Rhaetian to the ETE, terminated by a 300 kyr interval of no trend and followed by a transient increase in the early Hettangian that levels off. We suggest that the first in the series of perturbations is linked to the influx of non-radiogenic Sr from the weathering of freshly erupted CAMP basalts, leading to a delay in the radiogenic continental weathering response. The subsequent rise in 87Sr/86Sr after the TJB is explained by intensified continental crustal weathering from elevated CO2 levels and reduced mantle-derived Sr flux. Using Sr flux modeling, we also find support for such multiphase, prolonged continental weathering scenario. Aggregating the new dataset with published records employing an astrochronological age model results in a highly resolved Sr isotope reference curve for an 8.5 Myr interval around the TJB.