Abstract The European Organization for Nuclear Research (CERN) is currently undertaking a feasibility study to build the next-generation particle accelerator, named the Future Circular Collider (FCC), hosted in a 90–100 km subsurface infrastructure in the Geneva Basin, extending across western Switzerland and adjacent France. This article represents a preliminary, basin-scale stratigraphic and lithotype analysis using state-of-the-art Swiss and French stratigraphic terminology, set in context with the FCC. Existing stratigraphic information, rock cores and well reports, laboratory analyses and geophysical well-logs from 661 wells representative for the construction area have been integrated to pave the way for a multidisciplinary approach across several geoscientific and engineering domains to guide the FCC’s upcoming technical design phase. Comparisons with well-log data allowed the identification of rock formations and lithotypes, as well as to formulate a preliminary assessment of potential geological hazards. Regional stratigraphic evaluation revealed the FCC’s intersection of 13 geological formations comprising 25 different lithotypes across the Geneva Basin. A lack of data remains for the western to south-western subsurface region of the FCC construction area shown by well-density coverage modelling. The main geological hazards are represented by karstic intervals in the Grand Essert Formation’s Neuchâtel Member, Vallorbe and Vuache formations, associated to fractured limestone lithotypes, and Cenozoic formations represented by the pure to clayey sandstone-bearing Transition zone and Siderolithic Formation. Potential swelling hazard is associated to the presence of anhydrite, and claystone lithotypes of the Molasse Rouge and Grès et Marnes Gris à gypse formations, yielding up to 17.2% of smectite in the Molasse Rouge formation. Hydrocarbon indices in both gaseous and bituminous forms are encountered in the majority of investigated wells, and bear a potential environmental hazard associated with the Molasse Rouge deposits and fractured limestones of the Mesozoic Jura formations.

10.1186/s00015-022-00407-y

Cite

Citations (3)

Fluid flow through the sedimentary cover in northern Switzerland recorded by calcite–celestite veins (Oftringen borehole, Olten)

Swiss Journal of Geosciences (2011)

Antoine de Haller Αlexandre Tarantola Martin Mazurek Jorge E. Spangenberg

Molasse

Marl

10.1007/s00015-011-0085-x

Cite

Citations (9)

A non-magmatic component in fluids of South American Fe oxide-Cu-Au deposits inferred from ´37Cl, 87Sr/86Sri and Cl/Br

Springer eBooks (2005)

Massimo Chiaradia David Banks R. A. Cliff Robert Marschik Antoine de Haller

Brine

10.1007/3-540-27946-6_187

Cite

Citations (1)

New constraints on the tectonic history of the basement of the Western Cordillera and coastal forearc of Ecuador

Lithos (2024)

Richard Spikings Sebastian Betancur Cristian Vallejo Massimo Chiaradia Alexey Ulianov

Forearc

Basement

10.1016/j.lithos.2024.107821

Cite

Citations (1)

The Raul-Condestable Iron Oxide Copper-Gold Deposit, Central Coast of Peru: Ore and Related Hydrothermal Alteration, Sulfur Isotopes, and Thermodynamic Constraints

Economic Geology (2009)

Antoine de Haller Lluı́s Fontboté

The iron oxide copper-gold (IOCG) Raul-Condestable deposit is located 90 km south of Lima, Peru, and approximately 5 km from the Pacific coast. Mineralization consists mainly of replacement mantos and disseminations within permeable volcaniclastic and carbonate-rich rocks and structurally controlled veins surrounding a coeval and apparently causative intrusion of tonalitic composition emplaced in the core of a dacitic volcano. Potassic (biotite grading upward to sericite-chlorite) alteration and a poorly developed, almost sulfide-free, quartz stockwork closely border the tonalite, affecting the basaltic to dacitic Lower Cretaceous volcano-sedimentary host sequence. Ore is associated with a hydrated calc-silicate (mainly amphiboles) alteration that surrounds the biotite alteration. A hematite-chlorite (albite, epidote, calcite) alteration affects the periphery of the system. The main ore stage is characterized by two end-member mineral associations that were formed according to (1) an oxidized deposition sequence (hematite-magnetite-pyrite-chalcopyrite) occurring in and near feeder structures, and (2) a reduced deposition sequence (pyrrhotite-pyrite-chalcopyrite) found in volcaniclastic rocks and veins. Early specular hematite of the oxidized sequence is transformed to magnetite (“mushketovite”). The main ore-stage mineralization is cut by minor late-stage calcite-sulfide veins. Main ore-stage sulfides have δ34S values asymmetrically distributed from 1.0 to 26.3 per mil, with a median at 6.6 per mil (n = 51). Similar values are observed for pyrrhotite, pyrite, and chalcopyrite. The δ34S values depend on the stratigraphic position, with deep-seated vein samples normally distributed between 1.0 and 6.3 per mil (avg about 3.5‰, n = 13) and shallower samples from 2.7 to 26.3 per mil (median around 7.5‰, n = 39). Sulfides found in late-stage calcite-sulfide veins show strongly negative δ34S values ranging between –32.7 and –22.9 per mil (n = 6), indicating a possible biogenic source. Because no rock unit is known to occur in the internal parts of the deposit that could have oxidized fluids to the point of hematite stability, the oxidized mineral sequence is best explained by magmatic brines following the SO2-H2S gas buffer at high temperature (>350°C) and fluid/rock ratio. This is supported by the close to magmatic δ34S values of sulfides from the deep parts of feeder veins. Mass-balance calculation based on sulfur isotope data suggests that at the deposit scale, the bulk of the sulfides is dominated by magmatic sulfur, with sulfides of the oxidized minerals association having a larger component of magmatic sulfur than those of the reduced mineral association. The deposition sequence from hematite to chalcopyrite reflects the cooling of the magmatic fluid and redox and pH buffering by the basaltic-andesitic volcano-sedimentary host rocks. Thus, the occurrence of magnetite pseudomorphous after early hematite (mushketovite) paragenetically followed by iron-bearing sulfides is interpreted to be direct field evidence for precipitation from oxidized magmatic brines. The same sequence has been described in many IOCG, skarn, and some porphyry copper deposits worldwide. δ34S values of sulfides ranging up to 26.3 per mil are found in what corresponded to a relatively shallow aquifer filled with evolved reduced seawater. Heavy sulfur in H2S was produced through thermochemical reduction of Aptian seawater sulfate (δ34S = 14‰) in the recharge zone, which is interpreted to correspond to the hematitechlorite (albite, epidote, calcite) alteration present at the upper flanks of the hydrothermal system, adjacent to the causative intrusion. Hematitization (through oxidation) resulted from the high fO2 of seawater and from the reduction of its sulfate to H2S by the Fe2+ contained in the rock. In the core of the system, the seawater-derived fluids reached near chemical equilibrium with their actinolitized host rock, at about 300° to 350°C, in reduced, rock-dominated conditions. Mixing of these fluids with magmatic brines, already partially or totally reduced through reaction with wall rock at medium to low magmatic fluid/rock ratio can explain the large positive δ34S scatter observed in sulfides of the reduced mineral association, at stratigraphically shallow positions.

10.2113/gsecongeo.104.3.365

Cite

Citations (45)

Veins in clay-rich aquitards as records of deformation and fluid-flow events in northern Switzerland

Applied Geochemistry (2018)

Martin Mazurek Donald W. Davis Herfried Madritsch Daniel Rufer Igor M. Villa

Molasse

10.1016/j.apgeochem.2018.05.010

Cite

Citations (20)

The stable H and O isotope analysis of small highly saline water samples: A methodological study

Elsevier eBooks (2009)

Antoine de Haller Jorge E. Spangenberg Jochen Smuda M. Koroleva

Molality

Saline water

Saturation (graph theory)

Source

Cite

Citations (0)

Microstratigraphy and palaeoenvironmental implications of a Late Quaternary high‐altitude lacustrine record in the subtropical Andes

Sedimentology (2022)

Lucía Guerra Mateo A. Martini Hendrik Vogel Eduardo L. Piovano Irka Hajdas

Abstract High‐mountain lake records in semiarid foreland settings, such as the central Andes of North‐western Argentina, are highly restricted and often deprived of well‐preserved microstratigraphic information to analyze palaeoenvironmental changes and their causes, particularly for periods prior to the Last Glacial Maximum. Laguna La Salada Grande (23°S/65°W, 4063 metres above sea‐level) is a closed shallow lake located at Cordillera Oriental, North‐western Argentina with a unique depositional record, including geomorphic and stratigraphic evidence of palaeoenvironmental changes since the Late Pleistocene. In order to understand the depositional dynamics of this mountain lacustrine system at different timescales, limnogeological multiproxy analyses together with a radiocarbon and 210 Pb‐based chronology were applied on massive and laminated sediments from La Salada Grande. Laminated deposits were further analyzed using novel sub‐centimetric mineralogical, textural and geochemical automated methods (including a combination of micro‐X‐ray fluorescence and quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN ® ). Thick laminated microfacies at the beginning of the sequence record a deep and organic matter productive palaeolake prior to ca 34 ka (1 ka = 1000 years before 1950), that changed into a highly fluctuating shallower‐palaeolake with frequent detrital influxes after ca 34 ka. Microstratigraphy of the coarser‐grained detrital laminae between 31 ka and 25 ka reveals irregular and probably sub‐centennial high‐energy discharge events, pointing to convective atmospheric activity as the main trigger. After ca 21 ka the lake evolved to deeper water‐level conditions resulting in fine‐grained deposits with limited delivery of coarse‐grained sediments, followed by an abrupt lake level drop and incision. The multi‐millennial palaeoenvironmental reconstruction of La Salada Grande, and its correlation with other palaeoclimate records, shows a close link between the lacustrine depositional processes and palaeoclimate changes associated with the South American summer monsoon dynamics. This multifocal research in such an understudied environment provides key knowledge about lacustrine functioning and discharge events−climate interactions of mountain lakes of semi‐arid climates.

Chronology

10.1111/sed.13004

Cite

Citations (6)