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Pearson correlation coefficient matrix between all parameters analyzed in the dataset. Warm and cold colors show positive and negative correlation, respectively. The black rectangle across the first five columns highlights the five important experimental products.
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The origin of methane and light hydrocarbons (HCs) in natural fluids from serpentinization has commonly been attributed to the abiotic reduction of oxidized carbon by H2 through Fischer-Tropsch-type (FTT) reactions. Multiple experimental serpentinization studies attempted to identify the parameters that control the abiotic production of H2, CH4, an...
Citations
... Lab-scale demonstrations of SGH are constrained in scope but have effectively stimulated a variety of source rocks under relevant conditions and time periods -often operating over several weeks to several months to achieve steady-state hydrogen generation. Reported production rates can vary from one another substantially, sometimes by orders of magnitude from field measurements [45]- [47] -highlighting the intrinsic challenge of assigning singular values to production rates in this work. From the lab-scale experiments, a steady state production rate of 1 kg H2/m 3 source rock seems achievable under their idealized conditions, which is 25% of the 4 kg H2/m 3 maximum yield of peridotite-type rocks. ...
Geological hydrogen has emerged as a low-cost and low-carbon primary source of energy. This study provides a comprehensive techno-economic analysis of natural geological hydrogen (GH) and stimulated geological hydrogen (SGH) production, reaffirming its potential as a low-cost energy source. For the United States, we estimate production costs at 0.92/kg for SGH, demonstrating the feasibility of achieving production below $1/kg under optimal conditions. Detailed sensitivity analyses reveal hydrogen purity and production flow rates at the well head as primary cost drivers along with final delivery pressure of hydrogen. Although, GH has lower cost, SGH's scalability, driven by ubiquitous iron-rich rocks and controlled production rates, positions it as a practical solution for co-locating near demand centers. These findings underscore the potential of geological hydrogen to contribute significantly to a sustainable energy future, provided further field data validates the underlying assumptions.
... Presumably, the high pH enhances dissolution of siliceous components and thereby aids water-rock interactions. Experimental reviews of an extensive database such as Barbier et al. [2020], show that reaction kinetics correlate strongly to parameters including temperature, pressure, grain size, time, and fluid composition. Optimal reaction temperatures reported in many studies range between 200 and 350°C [Barbier et al. 2020]. ...
... Experimental reviews of an extensive database such as Barbier et al. [2020], show that reaction kinetics correlate strongly to parameters including temperature, pressure, grain size, time, and fluid composition. Optimal reaction temperatures reported in many studies range between 200 and 350°C [Barbier et al. 2020]. ...
An experimental setup was created to study serpentinization of an olivine sand sample and study hydrogen production. Inspired by the so-called "white" hydrogen sources, enhanced serpentinization of olivine represents an attractive opportunity to produce hydrogen from geological resources. Literature offers examples of experimental conditions that achieve hydrogen production at laboratory scale with different degrees of success. We made a preliminary selection of experimental parameters and assembled a setup capable of replicating conditions suitable for hydrogen production from enhanced olivine serpentinization. Commercially available olivine sand was selected with a grain size range of 250 to 355 µm for the experiment. The sample was subjected to 18 days of high pH brine exposure via continuous inflow, while inside a reactor heated by a furnace. The operating temperature range inside the reactor was between 80 and 245°C. The produced gas phase was separated, periodically collected, and analyzed via gas chromatography calibrated for hydrogen. Analysis of the produced gas showed hydrogen concentrations of 9 and 13% by mole. The precursor olivine sand was characterized in pre- and post-reaction states using scanning electron microscopy and analytical techniques (x-ray diffraction and x-ray fluorescence). A significant amount (14 wt% of the reacted sample) of serpentine precipitate was observed, coating the grains. The analysis suggests that the serpentinization reaction was maintained by the large grain size and the development of accessible porosity between the grains and grain-coating serpentine precipitates. Minor amounts of carbonate, magnetite, and variable composition (Ca-Fe-Mg-Ti) silicate precipitates were also observed. These preliminary results suggest that it is possible to enhance, at laboratory scale, serpentinization of olivine and generate hydrogen with significant H2 compositional yields. Our findings are supported by produced gas analysis and evidence collected on the reacted sample.
... Horita and Berndt, 1999;Bradley, 2016). A recent statistical network analysis by Barbier et al. (2020) of all available experimental studies of abiotic CH 4 synthesis reported in the literature, in contrast, found no clear support for enhancement of CH 4 production rates by FTT catalysts. The study does not, however, acknowledge the extraordinarily high rates of CH 4 production observed in hydrothermal carbon reduction experiments conducted with native Fea known FTT catalyst McCollom et al. 2010), or with Fe-Ni alloy (Horita and Berndt, 1999) discussed further below. ...
... The study does not, however, acknowledge the extraordinarily high rates of CH 4 production observed in hydrothermal carbon reduction experiments conducted with native Fea known FTT catalyst McCollom et al. 2010), or with Fe-Ni alloy (Horita and Berndt, 1999) discussed further below. Barbier et al.(2020) include many diverse types of experiments (including low pressure, dual-phase experiments) performed with many types of reactor materials (Au-Ti, stainless steel), the majority without added 13 C that would allow reliable tracking of C sources and sinks (Barbier et al., 2020). In the absence of labeled C sources, it is not always possible to distinguish CH 4 generation from background carbon sources in reactant solutions and solids (either preformed or generated by thermogenic processes) from bona fide abiotic C reduction. ...
... The study does not, however, acknowledge the extraordinarily high rates of CH 4 production observed in hydrothermal carbon reduction experiments conducted with native Fea known FTT catalyst McCollom et al. 2010), or with Fe-Ni alloy (Horita and Berndt, 1999) discussed further below. Barbier et al.(2020) include many diverse types of experiments (including low pressure, dual-phase experiments) performed with many types of reactor materials (Au-Ti, stainless steel), the majority without added 13 C that would allow reliable tracking of C sources and sinks (Barbier et al., 2020). In the absence of labeled C sources, it is not always possible to distinguish CH 4 generation from background carbon sources in reactant solutions and solids (either preformed or generated by thermogenic processes) from bona fide abiotic C reduction. ...
... In addition to natural examples of abiotic hydrocarbons, numerous experimental studies of abiotic hydrocarbon formation at elevated temperatures and pressures have been reported (Foustoukos and Stern, 2012;Manning et al., 2013;McCollom, 2013). Under crustal conditions, the formation of hydrocarbons in serpentinization experiments has been widely studied with and without catalysts such as metallic iron (Barbier et al., 2020). At higher, upper mantle pressures, some experimental studies have focused on fluids without minerals present. ...
... This indicates that Al tends to substitute for Si in the tetrahedral sheets (Evans et al. 2013), which may stabilize antigorite at higher temperatures (Padrón-Navarta et al. 2013). Our XGBoost model thus documents the importance of serpentine mineral replacements during mass transfers in subduction zones and relates serpentine chemical compositions to their geological environments, whereas traditional geochemical methods have limited capabilities to provide such information on alteration chemistry (e.g., Barbier et al. 2020). ...
The three main serpentine minerals, chrysotile, lizardite, and antigorite, form in various geological settings and have different chemical compositions and rheological properties. The accurate identification of serpentine minerals is thus of fundamental importance to understanding global geochemical cycles and the tectonic evolution of serpentine-bearing rocks. However, it is challenging to distinguish specific serpentine species solely based on geochemical data obtained by traditional analytical techniques. Here, we apply machine learning approaches to classify serpentine minerals based on their chemical compositions alone. Using the Extreme Gradient Boosting (XGBoost) algorithm, we trained a classifier model (overall accuracy of 87.2%) that is capable of distinguishing between low-temperature (chrysotile and lizardite) and high-temperature (antigorite) serpentines mainly based on their SiO2, NiO, and Al2O3 contents. We also utilized a k-means model to demonstrate that the tectonic environment in which serpentine minerals form correlates with their chemical compositions. Our results obtained by combining these classification and clustering models imply the increase of Al2O3 and SiO2 contents and the decrease of NiO content during the transformation from low-to high-temperature serpentine (i.e., lizardite and chrysotile to antigorite) under greenschist–blueschist conditions. These correlations can be used to constrain mass transfer and the surrounding environments during the subduction of hydrated oceanic crust.
... Meanwhile, geologic hydrogen has emerged as a promising new clean energy source (Hand, 2023). One approach to generating hydrogen from the subsurface is through chemical reaction processes: minerals such as olivine can react with water and transform to serpentine, generating hydrogen (known as white hydrogen or gold hydrogen, e.g., Barbier et al. 2020, Ellison et al. 2021, Klein et al. 2013, Lamadrid et al. 2017, McCollom et al. 2009, 2020, Osselin et al. 2022). This process can potentially produce 23 million tonnes of H 2 each year (Zgonnik, 2020)-an amount equal to almost a quarter of the current total hydrogen demand globally (IEA, 2021). ...
... The relationship involving the iron end member of olivine (fayalite) is the most studied reaction in laboratory experiments (Barbier et al. 2020). The production of H 2 is accompanied by the production of magnetite (Fe 3þ 2 Fe 2þ O 4 ), which is a ferrimagnetic mineral. ...
Hydrogen (H 2 ) emanations have been recognized in the south and north of the Pyrenees fold belt, within its two forelands. The proposed source is a mantle wedge rather near the surface which is currently undergoing serpentinization. The migration pathway seems to be the deep rooting faults since the H 2 content is higher where the faults reach the surface. The zone of current H 2 generation is around 10 km deep. It is evident from filed observations that kilometric pieces of mantle have been incorporated in the thrusts and outcrop in a few areas along the mountain belt. We studied the Turon de Tecouère, one of this mantle-derived body, using various field and laboratory tools focusing on the characterization of its alteration, the degree of serpentinization and its heterogeneity at the kilometer-scale. Accordingly, magnetic field and magnetic susceptibility were mapped, classical optical observations and 3D scan of some samples were performed and H 2 soil gas content mapping has been carried out. The results show heterogenous serpentinization from 3% to 62% at km to the µm scale. Since, the temperature and burial history are the same overall the Turon de Tecouère, these factors were not sufficient to characterize the level of transformation in the H 2 generating rock. The soil gas measurements show current H 2 emanations in and around the Turon de Tecouère. Near surface H 2 production of this mantle body is unlikely in the current knowledge of the H 2 generation kinetics. To explain these emanations, we favor a preferential migration pathway within the Turon root and the surrounding faults.
Thematic collection: This article is part of the Hydrogen as a future energy source collection available at: https://www.lyellcollection.org/topic/collections/hydrogen
... Serpentinization is readily observed in natural environments: at mid-ocean ridges (e.g., Charlou et al., 2002;Kelley et al., 2005;Liu et al., 2023) and on land (e.g., Barnes et al., 1978;Leong et al., 2021;Leong & Shock, 2020;Sánchez-Murillo et al., 2014), requiring only peridotite to be exposed to water at crustal-to-upper-mantle conditions (<∼6 GPa, <∼600°C) (Janecky & Seyfried, 1986). The process has also been recreated within laboratory experiments with both natural and synthetic samples at a range of pressures and temperatures (see recent review by Barbier et al., 2020) and thermodynamic modeling of subduction zones predicts the presence of serpentinite minerals, chiefly antigorite, up to a depth of 6 GPa (Abers et al., 2017;Maurice et al., 2020;Ulmer & Trommsdorff, 1995) (though H2 could be generated more deeply as olivine reacts with water to form magnetite and H2, e.g., Malaspina et al., 2023). ...
Serpentinization is among the most important, and ubiquitous, geological processes in crustal–upper mantle conditions (<6 GPa, <600°C), altering the rheology of rocks and producing H2 that can sustain life. While observations are available to quantify serpentinization in terrestrial and mid‐ocean ridge environments, measurements within subduction zone environments are far more sparse. To overcome this difficulty, we design a methodology to quantify and offer a first‐order estimate of the magnitude of “slab‐serpentinization” that has occurred over the last 5 Ma within the world's subduction zones by coupling four discrete tectonic and geophysical datasets—(a) raster grids of relic abyssal peridotite (peridotite exhumed from slow spreading mid‐ocean ridges but unaffected by pre‐subduction serpentinization) within ocean basins, (b) slab geometry, (c) thermal profiles and a (d) plate‐tectonic model. Averaged per year, our results suggest that 4.2–24 • 10⁷ kg of H2 per annum could be generated from “slab‐serpentinization” within a subduction zone. Our estimate is 3–4 orders of magnitude lower than what is thought to be produced at mid‐ocean ridges, and 1–2 orders of magnitude lower than what could occur through serpentinization at trench flexure and when including possible mantle wedge serpentinization. Higher hydrogen production is correlated most strongly with the spreading history of ocean basins, underlaying the importance of the tectonic history of a slab prior to subduction.
... 1. Ultrabasic rocks and associated minerals (i.e., peridotite and olivine) are the most tested reactants (Barbier et al., 2020) because the generation of H 2 was first evidenced during the serpentinization process. However, the few new starting materials tested (pyroxene, amphibole, Fe-carbonates, Fe-oxides) show a comparable H 2 productiveness, which is encouraging in the search for new H 2 _GRs around the world. ...
... Various ranges of pressure have been tested, especially in the case of serpentinization. See Barbier et al. (2020) for discussion. 3. Subsequently, a limited number of studies have been dedicated to low-temperature alteration but according to the data available in the literature, serpentinization is a low H 2 generator (Neubeck et al., 2011). ...
Natural dihydrogen (H 2 ) exploration is now active in various countries, but tools and workflows that help to characterize prospective zones are still poorly defined. This review paper is dedicated to share our experience in characterizing H 2 plays based on exploration efforts carried out in many countries in Europe, North and South America, Africa, and Oceania between 2017 and 2023. We decided to focus on onshore exploration where three main reactions are generating H 2 : (i) redox reactions between Fe ²⁺ and H 2 O, (ii) radiolysis of water and, (iii) organic late maturation where H 2 comes from hydrocarbons. This leads to classify the H 2 generating rocks (H 2 _GR) into four types that seem us the more likely to be of economic interest: basic and ultrabasic rocks of oceanic/mantellic affinity (H 2 _GR1), iron-rich bearing sedimentary and intrusive rocks, (H 2 _GR2), radioactive continental rocks (H 2 _GR3) and organic matter-rich rocks (H 2 _GR4). For the pre-fieldwork, the workflow aims to target new promising areas for H 2 exploration. Cross-referencing the presence of H 2 _GR in the basement, classical geological-hydrodynamic features (fault, water source), and already-known H 2 occurrences at the surface remain essential but should be accompanied by remote sensing analyses to detect possible H 2 occurrences. For the fieldwork, the focus is made on gas and rocks. A discussion is led concerning the importance of punctual measurements and long-term monitoring of gas seepages, that allow to conclude on dynamics of H 2 leakage from depth through space and time. For the post-fieldwork, we present the most useful analytical tools to characterize H 2 gas seepages and the suspected H 2 _GR. The critical parameters to estimate the H 2 potential of a rock are the content in Fe ²⁺ /Fe tot (H 2 _GR1 and H 2 _GR2), the content of radioactive elements U, Th, K (H 2 _GR3), and the total organic content (H 2 _GR4). The hydrogen exploration is in its infancy and all the profession is attempting to define an automated and fast workflow. We are still far away from it due to a lack of data, yet this review presents a practical guide based on the current knowledge.
... Catalyzed by minerals, this facilitates abiotic reactions of the produced H 2 with mantle-derived carbon dioxide (CO 2 ) or carbon monoxide (CO) (McCollom and Seewald, 2001). In Sabatier (Reaction 2) and Fischer-Tropsch (Reaction 3) type processes, methane (CH 4 ) and small organic molecules [C n H(2n + 2)] are enriched in the hydrothermal fluid (Barbier et al., 2020) ...
... Alternatively, small organic molecules may serve as primary source of carbon. These include organic acids such as formate and acetate produced in Fischer-Tropsch and Sabatier-type reactions (Barbier et al., 2020;Fones et al., 2021) or via acetogenesis and fermentation (Kohl et al., 2016;Suzuki et al., 2017), as well as amino acids such as glycine produced in Strecker synthesis (Ménez et al., 2018;Nobu et al., 2022) (Figure 1A). The abiotic origin of those organic carbon sources tackles the definition of heterotrophy, which normally refers to the consumption of organic compounds derived from organic sources (Schönheit et al., 2016). ...
Serpentinite-hosted systems are amongst the most challenging environments for life on Earth. Serpentinization, a geochemical alteration of exposed ultramafic rock, produces hydrothermal fluids enriched in abiotically derived hydrogen (H2), methane (CH4), and small organic molecules. The hyperalkaline pH of these fluids poses a great challenge for metabolic energy and nutrient acquisition, curbing the cellular membrane potential and limiting electron acceptor, carbon, and phosphorous availability. Nevertheless, serpentinization supports the growth of diverse microbial communities whose metabolic make-up might shed light on the beginning of life on Earth and potentially elsewhere. Here, we outline current hypotheses on metabolic energy production, carbon fixation, and nutrient acquisition in serpentinizing environments. A taxonomic survey is performed for each important metabolic function, highlighting potential key players such as H2 and CH4 cycling Serpentinimonas, Hydrogenophaga, Methanobacteriales, Methanosarcinales, and novel candidate phyla. Methodological biases of the available data and future approaches are discussed.
