Stefano M. Bernasconi

Last Name

Bernasconi

First Name

Stefano M.

ORCID

0000-0001-7672-8856

Organisational unit

09601 - Stoll, Heather / Stoll, Heather

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Publications 1 - 10 of 468

Soil Processes and Functions in Critical Zone Observatories
Banwart, Steven; Bernasconi, Stefano M.; Bloem, Jaap; et al. (2011)
Vadose Zone Journal
Microbial utilization of abiogenic carbon and hydrogen in a serpentinite-hosted system
Lang, Susan Q.; Früh-Green, Gretchen L.; Bernasconi, Stefano M.; et al. (2012)
Geochimica et Cosmochimica Acta
Sulfur in peridotites and gabbros at Lost City (30°N, MAR)
Delacour, Adélie; Früh-Green, Gretchen L.; Bernasconi, Stefano M.; et al. (2008)
Geochimica et Cosmochimica Acta
A simple method for the removal of dissolved organic matter and d15N analysis of NO3-from freshwater
Huber, Benjamin; Bernasconi, Stefano M.; Pannatier Graf, Elisabeth; et al. (2012)
Rapid Communications in Mass Spectrometry
Search for microbial life in the deep sub-seafloor
Warthmann, Rolf; Meister, Patrick; Mauclaire, Laurie; et al. (2004)
ESA SP ~ Mars: the search for life : proceedings of the 3rd European Workshop on Exo-Astrobiology : 18-20 November 2003 Madrid, Spain
Multi-stage evolution of the Lost City hydrothermal vent fluids
Aquino, Karmina A.; Früh-Green, Gretchen L.; Rickli, Jörg; et al. (2022)
Geochimica et Cosmochimica Acta
Serpentinization-influenced hydrothermal systems, such as the Lost City Hydrothermal Field (LCHF), are considered as potential sites for the origin of life. Despite an abundance of reducing power in this system (H2 and CH4), microbial habitability may be limited by high pH, elevated temperatures, and/or low concentrations of bioavailable carbon. At the LCHF, the relative contribution of biotic and abiotic processes to the vent fluid composition, especially in the lower temperature vents, remain poorly constrained. We present fluid chemistry and isotope data that suggest that all LCHF fluids are derived from a single endmember produced in the hotter, deeper subsurface essentially in the absence of microbial activity. The strontium isotope composition (87Sr/86Sr) of this fluid records the influence of underlying mantle and/or gabbroic rocks, whereas sulfur isotope composition indicates closed-system thermochemical sulfate reduction. Conductive cooling and transport is accompanied by continued sulfate reduction, likely microbial, and mixing with unaltered seawater, which produce second-order vents characterized by higher δ34Ssulfide and lower δ34Ssulfate values. Third-order vent fluids are produced by varying degrees of subsurface mixing between the first- and second-order fluids and a seawater-dominated fluid. Additional biotic and abiotic processes along different flow paths are needed to explain the spatial variability among the vents. Relationships between sulfur geochemistry and hydrogen concentrations dominantly reflect variations in temperature and/or distance from the primary outflow path. Methane concentrations are constant across the field which point to an origin independent of flow path and venting temperature. At Lost City, not all vent fluids appear to have zero Mg concentrations. Thus, we propose an extrapolation to a Sr isotope-endmember composition as an alternative method to estimate endmember fluid compositions at least in similar systems where a two-component mixing with respect to Sr isotopes between seawater and endmember fluids can be established.
Reconstructing the magnitude of Early Toarcian (Jurassic) warming using the reordered clumped isotope compositions of belemnites
Fernandez, Alvaro; Korte, Christoph; Ullmann, Clemens V.; et al. (2021)
Geochimica et Cosmochimica Acta
The magnitude of temperature changes in the Early Jurassic are not well known. Clumped isotope measurements can potentially be used to provide better constrains, but unfortunately many of the well-studied sedimentary successions that preserve Lower Jurassic fossils experienced burial temperatures above the limits of preservation of Δ47, which for geological timescales is thought to be between 80–120 °C. Samples from these basins are expected to be partially reordered and yield apparent clumped isotope temperatures that are warmer than original values. Here, we explore whether useful paleoclimate information can be recovered from these samples. We test the hypothesis that relative temperature differences are preserved in partially reordered samples when they experience a common burial history. This was done with the use of reordering models and Δ47 measurements of early Jurassic belemnites from the Aubach section of the SW German Basin, a basin that has a relatively well constrained burial history with maximum burial temperatures above 90 °C. We find that even though partial reordering progressively erases the Δ47 difference between samples, the majority (>50%) of the signal is preserved when samples are buried at temperatures as high of 150 °C for up to 200 Ma. Moreover, the models demonstrate that – regardless of burial conditions – partially reordered samples always preserve minimum records of temperature change across climate events. These inferences are supported by the belemnite Δ47 data that show partially reordered compositions and warming/cooling patterns across the Early Jurassic that closely mimic observations from independent proxies. Model observations are used to interpret a 13 ± 4 °C (95% ci) temperature increase that is observed in the belemnite data across the Early Toarcian. The large magnitude of the temperature excursion is explained as a combination of warming and a change in belemnite habitat before and after the Toarcian Ocean Anoxic Event. Our results demonstrate the usefulness of partially reordered samples and further open the use of this proxy in deep time settings.
Fluid mixing and organic carbon-mediated sulfate reduction in the formation of Alpine-type Zn-Pb sulfide deposits (Gorno district, Southalpine domain, N Italy)
Giorno, Michele; Bertok, Carlo; Barale, Luca; et al. (2025)
Ore Geology Reviews
Alpine-type Zn-Pb deposits are a subclass of Mississippi Valley-type (MVT) deposits, hosted in Anisian-Carnian carbonate rocks of the European Alps. They represent the second-largest province of Zn-Pb deposits in Europe in terms of resources and historic production. The Gorno mining district in Italy is a prime example of an Alpine-type district, with stratabound Zn-Pb-Ag (± fluorite ± barite) mineralization hosted in lower Carnian clay-rich sediments and peritidal limestones. Despite scientific and economic interest, there is no consensus on the genesis of the Gorno mineralization. This study sheds light on the ore-forming processes involved in Alpine-type deposits: metallogenesis at Gorno was related to hydrothermal activity associated with multiple stages of diagenesis and mineralization, including dolomitization, silicification, brecciation, dissolution, and cementation. Petrographic evidence, showing replacive and displacive growth of hydrothermal sulfides, dolomite, and quartz within unlithified sediments, indicates that mineralization occurred at shallow burial conditions, linked to Late Triassic extension, as confirmed by recent radiometric data. Microthermometry of primary fluid inclusions in sphalerite and fluorite, alongside sphalerite trace-element geothermometry—both never before applied in Gorno—indicates fluid temperatures between 70 and 140 °C (mean: ∼100 °C) and salinities up to ∼25 eq.wt% NaCl. Micro-Raman spectroscopy documents the involvement of gaseous hydrocarbons (e.g., CH4). Carbon, oxygen, and strontium isotopes suggest that the ore fluid was modified seawater that interacted with underlying Permian sandstones and basement. Ore-mineral precipitation was controlled by the distribution of organic-rich lithologies in the host-sequence and occurred through a combination of fluid mixing and in situ reduction of the ore fluids.
Les isotopes de l'oxygène associés au phosphate comme outil d'analyse du cycle du P
Frossard, Emmanuel; Tamburini, Federica; Bernasconi, Stefano M.; et al. (2012)
Journées d'étude des sols : actes des 11èmes JES : 19 au 23 mars 2012, Versailles
18O enrichment in phosphorus pools extracted from soybean leaves
Pfahler, Verena; Dürr-Auster, Thilo; Tamburini, Federica; et al. (2013)
New Phytologist

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Stefano M. Bernasconi

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