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

Petrophysical, Geochemical, and Hydrological Evidence for Extensive Fracture-Mediated Fluid and Heat Transport in the Alpine Fault's Hanging-Wall Damage Zone

Fault rock assemblages reflect interaction between deformation, stress, temperature, fluid, and chemical regimes on distinct spatial and temporal scales at various positions in the crust. Here we interpret measurements made in the hanging-wall of the Alpine Fault during the second stage of the Deep Fault Drilling Project (DFDP-2). We present observational evidence for extensive fracturing and high hanging-wall hydraulic conductivity (∼10−9 to 10−7 m/s, corresponding to permeability of ∼10−16 to 10−14 m2) extending several hundred meters from the fault's principal slip zone. Mud losses, gas chemistry anomalies, and petrophysical data indicate that a subset of fractures intersected by the borehole are capable of transmitting fluid volumes of several cubic meters on time scales of hours. DFDP-2 observations and other data suggest that this hydrogeologically active portion of the fault zone in the hanging-wall is several kilometers wide in the uppermost crust. This finding is consistent with numerical models of earthquake rupture and off-fault damage. We conclude that the mechanically and hydrogeologically active part of the Alpine Fault is a more dynamic and extensive feature than commonly described in models based on exhumed faults. We propose that the hydrogeologically active damage zone of the Alpine Fault and other large active faults in areas of high topographic relief can be subdivided into an inner zone in which damage is controlled principally by earthquake rupture processes and an outer zone in which damage reflects coseismic shaking, strain accumulation and release on interseismic timescales, and inherited fracturing related to exhumation

Data for: Identification of gas inflow zones in the COSC-1 borehole (Jämtland, central Sweden) by drilling mud gas monitoring, downhole geophysical logging and drill core analysis

Data_Fig_5: Drilling mud gas depth profiles of the COSC-1 boreholeData_Fig_6: Helium depth profile, DLLd, DLLs and DLLd/DLLs values, and fracture depths from core scanningTHIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Noble gas isotopes and the chemical composition of geothermal gases from the eastern part of the Buyuk Menderes Graben (Turkey)

We present noble gas isotope and gas composition data from eight production wells of the Kizildere geothermal field and from six gas discharging pools from the adjacent Tekke Hamam geothermal field, situated in the eastern segment of the Buyuk Menderes Graben system in western Anatolia (Turkey). Gas from both locations is composed mainly of CO2 with minor contributions of N-2, H2S, CH4, O-2, Ar, H-2, C2+ and He, with higher contents of H2S. He and C2+ in Tekke Hamam samples

Continuous in-situ measurements of gases (H2, H2S, CH4, N2, O2, He and CO2) at the fumarole “Soffionissimo” (Solfatara volcano, Southern Italy).

Temperature measurements and gas extraction were done at the fumarole very close to the “Bocca Grande”. The temperature measurements were performed with a temperature probe (K-type thermocouple), which was let about 30 cm into the fumarole. For better comparison of temperature and gas data, the gas tube was directly connected with the temperature probe, to make sure that temperature measurement and gas extraction were carried out at the same place. After having adjusted a continuous gas flow with diaphragm pump and a needle valve, the gas was piped through a 10 m Teflon© tube for more than 40 hours. The gas phase primary consists of water gas, which was condensed in a trap, installed in a refrigerator. The amount of water in the trap was determined in regular intervals (every 3-4 hours). At the beginning of the monitoring experiment, the Teflon© tube was heated in order to avoid condensation of the water in the tube before getting trapped. Although the tube was not heated for the whole time of the experiment, it turns out that the amount of water, condensed in the water trap per hour, does not significantly change when the tube was not heated. Hence, the amount of water, condensing in the tube before getting trapped, seems negligible. The remaining, almost water-free gas phase was finally dried over Fe in a filter, and then continuously analysed with a quadrupole mass spectrometer (Balzers Omnistar) for the following components: H2, H2S, CH4, N2, O2, Ar, He, and CO2. To make sure that the final drying process does not influence the gas composition in particular for H2 and H2S, a comparison measurement was done without the filter, which only revealed somewhat higher water content. During the second half of the monitoring, additionally a laser-optical CO2 sensor was installed (not shown in the sketch). Gas samples were taken from the gas line for laboratory gas-chromatographic analysis