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Hydrogeological characterisation of a Lower Jurassic rock unit at the Mont Terri - I: Data of the Opalinus Clay and the Staffelegg Formation

Opalinus Clay is chosen as host rock for the deep geological disposal of nuclear waste in Switzerland and is also being considered in Germany. The underlying Staffelegg Formation comprises potentially water-bearing layers. To investigate the hydrogeological setting of these two formations at the Swiss Rock Laboratory in Mont Terri two bore holes have been drilled in the framework of the HS-Experiment (Hydrogeological Survey). The 58 m long BHS-1 starts in the Lower Shaly facies of the Opalinus Clay, crossects the entire Staffelegg formation and ends in the Triassic Klettgau formation. The shorter BHS-2 provides additional data from the carbonate-rich sandy facies and Lower Shaly facies of the Opalinus Clay. The presented data publication provides geochemical, mineralogical and petrophysical parameters of rocks, pore water and (dissolved) gases from these two drillings. In the following the main measured parameter are listed: geochemical composition of bulk rock and single minerals, isotopic data of carbonates and S isotopes of bulk rock, cation exchange, analyses of organic compounds, bulk rock and clay mineralogy, bulk density, porosity, water content, noble gases, pore water composition, composition and isotopes of dissolved gases and water isotopes.

Experimental rock permeability data for illite-bearing Flechtinger sandstone measured with a flow-through apparatus at GFZ Potsdam

Temperature changes and variations in pore fluid salinity may negatively affect the permeability of clay‐bearing sandstones with implications for natural fluid flow and geotechnical applications alike. Cheng and Milsch (2020) investigated these factors for a sandstone dominated by illite as the clay phase. Flechtinger sandstone, a Lower Permian (Upper Rotliegend) sedimentary rock outcropping and commercially mined at the Sventesius Quarry near Flechtingen, Germany, was selected for the experiments. Three cylindrical cores were drilled from a larger block. Subsequently, samples were prepared with polished and plane-parallel end faces having a diameter of 30 mm and a length of 40 mm. The three samples were labelled FS1, FS3, and FS4, respectively. The three samples were vacuum-dried in an oven at 60 °C for 24 hours. They were then set under vacuum in a desiccator chamber for 10 hours and saturated with deionized water for another 24 hours. All experiments were performed with two flow-through apparatuses with details described in Milsch et al. (2008). The saturated sample is jacketed with a Fluorinated Ethylene Propylene (FEP) heat shrink tubing and is then mounted in the vessel. Afterwards, the two sample ends are connected to the upstream and downstream pumps, respectively. The flow direction, generally, is from the bottom to the top side of the sample but can be reversed for return permeability measurements.

Bericht zur bohrlochgeophysikalischen Messung an der Geothermiebohrung Gt P 14a/22 (Potsdam, Brandenburg)

In diesem Bericht wird die durch das GFZ Potsdam am 18. Juli 2024 durchgeführte bohrlochgeophysikalische Messung in der Bohrung Gt P 14a/23 in Potsdam (Brandenburg) dokumentiert. Die Messung wurde mit dem Ziel der Gewinnung hochaufgelöster und ungestörter Temperatur-Tiefen-Profile durchgeführt. Die Sidetrack-Bohrung der Hauptbohrung Gt P 14 wurde im März 2023 abgeteuft. Anschließend erfolgten Testarbeiten im Mai desselben Jahres. Bis zur Durchführung dieser Messungen erfolgten keine weiteren Aktivitäten in der Bohrung. Die Stillstandszeit (shut-in time) beträgt mind. 14 Monaten für die oberen 1.100 m, weshalb keine thermische Beeinflussung der Temperaturen durch den Bohrprozess mehr erwartet wird. In der Bohrung Gt P 14a/22 wurde bei 1039,9 m Teufe eine Temperatur von 46,07 °C gemessen, welches einem mittleren Temperaturgradienten von 35,6 °C/ km entspricht.

Bericht zur bohrlochgeophysikalischen Messung an der Soleverpressbohrung Ug Wsbg 10/76 (Wesenberg, MV)

In diesem Bericht wird die durch das GFZ Potsdam am 9. September 2020 durchgeführte bohrlochgeophysikalische Messung in der Bohrungen Ug Wsbg 10/76 in Wesenberg (Mecklenburg-Vorpommern) dokumentiert. Die Messung wurde mit dem Ziel der Gewinnung eines hochaufgelösten und ungestörten Temperatur-Tiefen-Profils durchgeführt. Die Untergrundspeicherbohrung wurde 1976 am Salzstock Wesenberg abgeteuft und lange als Sole-Verpressbohrung genutzt. Die Stillstandszeit nach letzter Nutzung liegt bei mind. 44 Monaten, weshalb von hydraulisch ungestörten Gebirgstemperaturen ausgegangen wird. In der Bohrung Ug Wsbg 10/76 wurde bei 1784,3 m Teufe eine Temperatur von 72.70 °C ermittelt, welches einem mittleren Temperaturgradienten von 36,0 °C/ km entspricht.

XRD analyses on cuttings samples from IODP Expeditions 338 and 348 (Nankai Trough accretionary prism)

This data publication uses XRD bulk rock analyses carried out on cuttings aboard D/V Chikyu during the International Ocean Discovery Program (IODP) Expeditions 338 and 348 of the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) project (Strasser et al, 2014, Tobin et al., 2015). More data on clay minerals in the C0002F and C0002P holes are published by Underwood and Song (2016a and 2016b), and Underwood (2017). These data are supplementary material for Schleicher and Jurado (2019).XRD data of the clay size fraction were analyzed at the University of Michigan, USA, and the GFZ Potsdam, Germany. All XRD analyses of the random powder and texture (oriented) preparation followed the analytical methods described in Moore and Reynolds (1997). Oriented clay size samples were measured under air-dried and glycolated conditions, the latter treatment caused interlayer expansion of swelling clays, allowing the recognition of discrete smectite and mixed-layer smectitic phases. In order to compare the clay mineral content, and the mineral amount relative to the adjacent material, exactly 45 μg of the material was mixed with 1.5 ml deionized water and dropped on a round glass slide (diameter 32 mm). All air-dried samples were measured at a relative humidity (RH) of ~30%, and afterward stored in a desiccator filled with ethylene glycol, in order to investigate the final swelling stage of the smectitic phases.The data are provided as tab delimited table (2019-002_Schleicher-Jurado_XRD-data.txt, see also Table 1 in Schleicher and Jurado, 2019) with the following columns:- Hole: name of the C0002 subhole- Depth (mbsf): depth in meter below surface (mbsf)- Sample (SMW): sample number SMW (solid cuttings taken from drilling mud)- Smectite (int./cps): intensity of smectite in counts per second (cps)- Illite (int./cps): intensity of smectite in counts per second (cps)In addition, the original XRD measurements are provided in raw and text formats (2019-002_Schleicher-Jurado_original-XRD-measurements.zip). All science data from these expeditions are also accesible via the Database of the science data acquired by International Ocean Discovery Program and Integrated Ocean Drilling Program expeditions of D/V Chikyu (http://sio7.jamstec.go.jp/).

Organochemical characterization of the mineralized Kupferschiefer in Spremberg, East Germany: Compositional and isotope data on hydrocarbons, biomarker and NSO compounds

Organic matter (OM) is known to be an important reductant in sediment-hosted base metal deposits like the European Kupferschiefer. However, the precise nature of interactions between OM and hydrothermal fluids are still debated as well as how the interconnected reactions develop over geological timescales. This dataset provides for the first time bulk, compositional and stable isotope data of hydrocarbons, biomarkers and organonitrogen, -sulfur and-oxygen (NSO) compounds for the mineralized Kupferschiefer Spremberg-Graustein field in Eastern Germany based on samples from two drill cores. The study aims to help to better understand the role that organic matter plays during the mineralisation and formation of the sedimentary ore deposit within the Kupferschiefer with a focus on stable hydrogen isotope compositions and NSO compositional data to especially address the origin and to assess the oxidative nature of the brines that caused the mineralization in the Spremberg-Graustein field. The data publication includes bulk, compositional and stable isotope data on inorganic metals and organic matter. The data about metal contents were generated using ICP-MS while those on the organic matter were generated using Rock-Eval pyrolysis, a microscope, a Soxhlet apparatus, medium pressure liquid chromatography (MPLC), gas chromatography with flame ionization (GC-FID) and mass spectrometric detection (GC-MS), gas chromatography isotope ratio mass spectrometry (GC-IRMS) and ultrahigh resolution mass spectrometry (Fourier Transform ion cyclotron resonance mass spectrometry, FT-ICR-MS) with Electrospray ionization (ESI) and Atmospheric pressure photoionization (APPI). The full description of samples, methods and data is given in the following sections.

Mechanical data of rotary shear experiments in bituminous dolostones

Mirror-like Surfaces (MSs) are ultra-polished fault surfaces widespread in carbonate seismic terrains, but their formation process is still debated. We deformed gouge samples from exposed fault surfaces hosted in bituminous dolostone rocks in a rotary shear apparatus (SHIVA) at seismic slip rates (1 m/s). By changing the water availability (water-pressurised and room-humidity conditions) and the organic matter/dolomite content (> 35%, dark gouge DG; < 30% bright gouge BG) we investigated the mechanical behaviour leading to MSs formation in fault gouges. We run tests at 15 MPa effective normal stress, 2 MPa confinement and 1 MPa pore pressure for the water-pressurised experiments and a total displacement of 0.13 m. Mirror-like fault surfaces were obtained in all successful experiments; mirrors were more developed under room-humidity conditions. Bituminous dolostones under room-humidity conditions had a slip neutral behaviour with a low friction (0.3). Bituminous dolostones under water-pressurised conditions showed a slip weakening behaviour with an initial peak effective friction μp = 0.65, followed by a drop to effective friction μss DG than in BG (i.e., μss of 0.25 vs 0.28). Future work will focus on the microstructural analysis of the experimental products and the investigation of the slip behaviour of bituminous dolostones at sub-seismic slip rates for a complete study of the slip behaviour spectra. This publication results from work conducted under the national open access action at SHIVA (Slow to High Velocity Apparatus) - HP-HT laboratory of experimental Volcanology and Geophysics (INGV, Roma 1 section) supported by WP3 ILGE - MEET project, PNRR - EU Next Generation Europe program, MUR grant number D53C22001400005.

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