Dissolved noble gases and stable isotopes as tracers of preferential fluid flow along faults in the Lower Rhine Embayment, Germany

Groundwater in shallow unconsolidated sedimentary aquifers close to the Bornheim fault in the Lower Rhine Embayment (LRE), Germany, has relatively low δ2H and δ18O values in comparison to regional modern groundwater recharge, and 4He concentrations up to 1.7 × 10−4 cm3 (STP) g–1 ± 2.2 % which is approximately four orders of magnitude higher than expected due to solubility equilibrium with the atmosphere. Groundwater age dating based on estimated in situ production and terrigenic flux of helium provides a groundwater residence time of ∼107 years. Although fluid exchange between the deep basal aquifer system and the upper aquifer layers is generally impeded by confining clay layers and lignite, this study’s geochemical data suggest, for the first time, that deep circulating fluids penetrate shallow aquifers in the locality of fault zones, implying  that sub-vertical fluid flow occurs along faults in the LRE. However, large hydraulic-head gradients observed across many faults suggest that they act as barriers to lateral groundwater flow. Therefore, the geochemical data reported here also substantiate a conduit-barrier model of fault-zone hydrogeology in unconsolidated sedimentary deposits, as well as corroborating the concept that faults in unconsolidated aquifer systems can act as loci for hydraulic connectivity between deep and shallow aquifers. The implications of fluid flow along faults in sedimentary basins worldwide are far reaching and of particular concern for carbon capture and storage (CCS) programmes, impacts of deep shale gas recovery for shallow groundwater aquifers, and nuclear waste storage sites where fault zones could act as potential leakage pathways for hazardous fluids

Data and Analysis: Stable isotopic composition of atmospheric precipitation on the Crimean Peninsula

The data represent time series of isotopic composition of atmospheric precipitation collected at two stations in Crimea in 2010-2014 (monthly means)

Compilation of 14C ages from Palaeolithic site Shulgan-Tash (Kapova) Cave, Southern Ural, Russia

Shulgan-Tash (a.k.a. Kapova) cave in Southern Ural, Russia is the easternmost European cave art monument of late Palaeolithic age. The data set contains 10 radiocarbon age dates from the cave published by different researchers between 1996-2016. Most of the dates were reported in difficult-to-access internal reports or proceedings, in Russian language. In many later re-publications the data were presented without explicit mentioning of whether or not the reported dates are calibrated and, sometimes, contained errors. This has led to “contamination” of the scientific record with non-calibrated 14C ages presented and interpreted (explicitly or implicitly) as calendar years. In this data set all available 14C ages from Shulgan-Tash cave are reported according to the standards of radiocarbon age presentation

Description of speleothem samples collected for U-series dating of Paleolithic cave art in Shulgan-Tash cave, Southern Ural, Russia

The data set describes sampling sites and samples of: (1) Flowstone underlying and overgrowing Paleolithic cave art in Shulgan-Tash cave collected for U-series dating; (2) Stalagmites, collected in Shulgan-Tash and three more caves (Kulyurtamak, Victoria, Gryoz) for U-series dating and paleoclimate studies; (3) Cryogenic cave calcite collected in Shulgan-Tash and Victoria cave for U-series dating and paleoenvironmental studies. Numeric results of dating are NOT reported in this data set

Isotopic composition of groundwater in Crimea

Stable isotope composition of groundwater sampled in natural springs, open wells, boreholes and mud volcanoes on the Crimean Peninsula. Excel file also contains maps identifying positions of sampled water occurrences

Geochemical and Isotopic Properties of Fluids from Gold-Bearing and Barren Quartz Veins of the Sovetskoye Gold Deposit (Siberia, Russia)

This paper reports on the comparative study of fluids trapped in inclusions in gold-bearing and barren quartz veins at the Sovetskoye gold deposit, Yeniseisky ridge, Siberia, Russia. The host rocks are greenschist facies metasedimentary rocks of Upper Proterozoic age. Within the deposit, some veins contain 10 to 25 ppm of Au (gold-bearing veins); others contain Jess than 1 ppm of Au (barren veins). Fluid inclusions trapped in barren veins are predominantly low-salinity-H20 (4.0—8.0 mass % NaCl equiv.) with variable contents of dissolved C02 (<12.5 mol 070), CH4 (<1.3 mol 0/0), and N2 (<1.7 mol 070). Homogenization temperatures vary from 2000 to 4100C, and the calculated pressures of entrapment are <1.5 kbars. Inclusion fluids trapped in the host schists are predominantly aqueous (97.6 —99.3 mol % HO), with C02 contents below 2.4 mol percent. The fluids trapped in ore-bearing quartz inclusions are different. Inclusions show higher homogenization temperatures (up to 6300C) and salinity (up to 20—25 mass % NaCl equiv). Calculated pressures range from 0.7 to 2.0 kbars. Bulk gas chromatographic data of fluids extracted from native gold have contents of C02 that range from 29.3 to 62.0 mol percent, N2 from 2.7 to 13.2 mol percent, and CH4 from 0.0 to 2.8 mol percent. In gold-bearing quartz the contents of C02 range from 18.0 to 41.0 mol percent, N2 from 0.1 to 0.2 mol percent, and CH4 from 0.3 to 3.0 mol percent. Raman spectroscopic data of fluid from gold-bearing quartz revealed C02 contents of individual inclusions as high as 98.2 mol percent, N2 up to 66.4 mol percent, and CH4 up to 88.7 mol percent. Fluids of the country-rock schists which host gold-bearing quartz veins are also enriched in C02 (up to 49.5 mol 0/0). The host rocks for both barren and gold-bearing quartz veins show consistent REE patterns characterized by a negative Eu anomaly. Fluids from barren quartz veins show similar REE patterns although with a less conspicuous negative Eu anomaly, whereas fluids from gold-bearing quartz show a marked positive Eu anomaly. Similar isotopic values of sulfur in pyrite, pyrrhotite, and arsenopyrite disseminated in country rocks (ð34S = 14.7—21.6%0), and in barren (ð34S = and gold-bearing quartz veins (ô34S = suggest that sulfur in sulfides was derived from the same source, most likely being the adjacent country rocks. C02 trapped in fluid inclusions of barren and gold-bearing quartz has distinct isotopic compositions (ð 13C = —8.1 to —10.2 and —4.9 to +5.2 700, respectively), and the ð 13C values are positively correlated with Au contents in veins. Helium isotope composition of both types of quartz veins (3He/4He = 0.04—0.05 Ra for gold-bearing veins and 3He/4He 0.02 Ra for barren veins) indicates a crustal provenance of mineral-forming fluids. The 40Ar/39Ar dating of sericite demonstrates that the barren veins (890—850 Ma) are significantly older than the gold-bearing veins (830—730 Ma). On the basis of their ages, barren veins are interpreted as symmetamorphic. The age of the gold-bearing veins corresponds to the age of the local granitoids (850—720 Ma), suggesting that the origin of the Sovetskoye deposit is related to the tectonic activity syntetctonic magmatism

First investigations of an ice core from Eisriesenwelt cave (Austria)

Investigations into the genesis and dynamical properties of cave ice are essential for assessing the climate significance of these underground glaciers. We drilled an ice core through a 7.1 m-thick ice body filling a large cavern of the dynamic ice cave Eisenriesenwelt (Austria). In addition to visual core inspections, quasi-continuous measurements at 2 cm resolution comprised particulate matter, stable water isotope (δ<sup>18</sup>O, δD) and electrolytic conductivity profiles supplemented by specifically selected samples analyzed for tritium and radiocarbon. We found that recent ablation led to an almost complete loss of bomb-derived tritium removing any ice accumulated since, at least, the early fifties leaving the actual ice surface even below the natural tritium level. The small particulate organic masses rendered radiocarbon dating inconclusive, though a crude estimate gave a basal ice age in the order of several thousand years. The visual stratigraphy and all investigated parameters showed a clear dichotomy between the upper 2 m and the bottom 3 m of the core, which points to a substantial change in the ice formation process. Main features of the core comprise the changing appearance and composition of distinct cryocalcite layers, extremely low total ion content and a surprisingly high variability of the isotope signature. Co-isotope evaluation (δD versus δ<sup>18</sup>O) of the core in comparison with data from precipitation and karst spring water clearly indicate that ice formation is governed by (slow) freezing of dripping water