Eric C. Gaucher

Lavoisier H2 Geoconsult

The chemistry of pore water is an important property of clayrocks being considered as host rocks for long-term storage of radioactive waste. It may be difficult, if not impossible, to obtain water samples for chemical analysis from such rocks because of their low hydraulic conductivity. This paper presents an approach for calculating the pore-water...

The development of Thermoddem, a thermodynamic database devoted to geochemical modelling for environmental studies in general and, more specifically, to chemical systems involving waste materials, is discussed here. Concerns are also focused on taking into account some specific needs for modellers by proposing different output formats and some impo...

In continental volcanic settings, abundant carbonate precipitation can occur with atypical facies compared to marine settings. The (bio-)chemical processes responsible for their development and early diagenesis are typically complex and not fully understood. In the Bolivian Altiplano, Laguna Pastos Grandes hosts a 40-km² carbonate platform with a g...

During the Early Cretaceous, massive evaporite accumulations formed in the opening South Atlantic. However, the evaporite depositional model is still poorly constrained at the scale of the West African margin. The present study focuses along the proximal domain of the south Gabon - Congo - Cabinda margin and is based on (i) log interpretations of 2...

This data set contains the results from a 2023 GFZ Innovative Research Expedition project to explore for natural hydrogen gas (H2) occurrences in the NW Pyrenean foreland, near the town of Biarritz in France. The data represent in-situ measurements of soil and spring water gas, as well as in-situ spring water property measurements, complemented wit...

Naturally occurring hydrogen gas (H2) represents a potentially major source of clean energy. The most promising mechanism for large-scale natural H2 generation is serpentinization where mantle material reacts with water while passing through a temperature-dependent “serpentinization window” (T = 200-350˚C) during mantle exhumation. We study such se...

Submarine volcanic activity releases large amounts of gases and metals in the water column, affecting biogeochemical cycles and ecosystems at a regional and local scale. In 2018, Fani Maoré submarine volcano erupted 50 km offshore Mayotte Island (Comoros Archipelago, Indian Ocean). Active eruptive plumes were observed in May 2019 at and around the...

Natural Hydrogen is a new, clean and low-carbon source of hydrogen that is produced by the Earth, and can migrate and accumulate in geological reservoirs. Its exploration has begun in many countries and its price could be significantly lower than other H2 sources. In this position paper, the earth2 initiative summarizes (i) what natural hydrogen is...

In carbonate rocks, natural production of sulfuric acid can form karstic cavities. Where both epigenic and hypogenic speleogeneses have taken place, these processes are challenging to constrain, especially if there is more than one source of sulfur involved. Thanks to an innovative approach coupling geomorphology with measurements of multiple sulfu...

We present a method for measuring the clumped isotope composition of molecular hydrogen (H2) using a high-resolution mass spectrometer, the Thermo 253 Ultra, improved to address subtle artifacts arising from instrument baselines and non-linear responses. We also present methods for purification and concentration of H2 from natural and experimental...

Maintaining global warming well below 2 °C, as stipulated in the Paris Agreement, will require a complete overhaul of the world energy system. Hydrogen is considered to be a key component of the decarbonization strategy for large parts of the transport system, as well as some heavy industries. Today, about 96% of current hydrogen production comes f...

The need to investigate mineral precipitation in heterogeneous sedimentary rock with complex pore network and mineral composition arises with problems like pore clogging by barite precipitation during sulfate-rich water injection in geological reservoirs, the durability of long term storage of nuclear waste or the damage induced by crystallisation....

The existence of geological fluids rich in natural hydrogen (H2) raises the question about the energy potential of this carbon-free resource. However, to date there is no exploration strategy based on robust methodologies and pathfinders. Therefore, it is important to develop an exploration guide that is not only focused on surface gas monitoring,...

The existence of geological fluids rich in natural hydrogen (H2) raises the question about the energy potential of this carbon-free resource. However, to date there is no exploration strategy based on robust methodologies and pathfinders. Therefore, it is important to develop an exploration guide that is not only focused on surface gas monitoring,...

The history of the first Native Hydrogen discovery in the South of France (in French)

This is an open access article. You can read it free of charge here https://www.pnas.org/doi/epdf/10.1073/pnas.2114720119 Significance: Natural gas is a key fossil fuel as the world transitions away from coal toward less polluting energy sources in an attempt to minimize the impact of global climate change. Historically, the origin of natural gas...

The water supply in drylands mainly relies on groundwater, making it a crucial resource. Springs in southern Africa are often underutilized, and are neither protected nor monitored. Thus, the aim of this study was to evaluate their quality in a sample area in northwestern Namibia and to propose solutions for the sustainable use of springs. In total...

In sedimentary basins, clay compaction by burial can lead to fluid overpressure and is suspected to also generate fresh waters, but few geochemical tracers are available to assess this process both qualitatively and quantitatively. Our objective was to carry out experiments on the chemical - and halogen (Cl, Br) isotope evolutions of pore water exp...

Interpreting the paleoecosystems of ancient microbialites relies on our understanding of how modern microbialites form in relation with the bio-physico-chemical conditions of their environment. In this study, we investigated the formation of modern carbonate microbialites in the hydrothermal system of La Salsa in Laguna Pastos Grandes (Bolivia), wh...

The Lower Cretaceous oil reservoirs of the Santos Basin are subject of many debates concerning the sedimentology, diagenesis, and current fluid compositions (hydrocarbons, water, CO2). The present study brings some new insights on (1) the origin of modern brines, (2) the spatial distribution of dissolved CO2 integrated with the structural setting,...

During orogenesis, large-scale thrusts as orogenic fronts can act as conduits and/or barriers for fluid flow. Unravelling the timing and modes of tectonic activation of large-scale faults is crucial to understanding the relationship between fluid flow and deformation. The North Pyrenean Frontal Thrust (NPFT) corresponds to a major basement-involved...

Phyllosilicates may trap hydrogen (H2) in the crust, but they may also produce it through various processes, including oxidative dehydrogenation. The dehydrogenation temperature depends on the type and composition of the phyllosilicates considered, but it may be as low as 300 °C. Here, we document the release of H2 and CO during thermal treatment o...

The peridotite massifs from the North-Western Pyrenean belt are fragments of a short-lived mid-Cretaceous hyper-extended rift inverted by the Pyrenean orogeny. We studied the petrology, mineralogy and geochemistry of 32 hydrothermally altered peridotites from the Montaut, Turon and Urdach massifs. This study aims to bring new constraints on the nat...

Native hydrogen (H2) may represent a new carbon free-energy resource, but to date there is no specific exploration guide to target H2-fertile geological settings. Here, we present the first soil gas survey specifically designed to explore H2 migration in a region where no surface seepage has been documented so far. We choose the Pyrenean orogenic b...

The link between fluid circulation schemes and basin histories remain one of the most valuable tools to understand the diagenetic evolution of petroleum reservoir. This study proposes a diagenetic model for the Deep Lacq reservoir constrained by petrography, geochemistry, fluid inclusions studies and basin modeling analyses. Drill cores penetrating...

The water released by smectite dehydration because of pressure and temperature increase during burial of claystone or clay-rich mudstone in sedimentary basins can generate overpressure and change the water salinity. Up until now, a clear distinction has been lacking between the water fraction produced by compaction and the water fraction produced b...

Native hydrogen (H2) may represent a new carbon free energy resource, but to date there is no specific exploration guide to target H2-fertile geological settings. Here, we present the first soil gas survey specifically designed to explore H2 migration in a region where no surface seepage has been documented so far. We choose the Pyrenean orogenic b...

Hypogenic caves, linked to carbonate rock dissolution due to CO2- and H2S-rich ascending deep waters, represent more than 10% of karstic networks worldwide; a proportion that increases as these systems are better constrained. However, interaction between hypogenic and epigenic processes is still poorly understood, especially since the subsequent in...

We present two computing tools, ClayTherm and ISTherm, devoted to the estimation of the thermodynamic properties of both anhydrous and hydrated clay minerals (ClayTherm), and of illite/smectite (I/S) mineral series (ISTherm). The first computing tool, ClayTherm, is devoted to thermodynamic property estimates for clay minerals. It combines several p...

The Meillon (Callovo-Oxfordian) and Mano (Tithonian) Formations are dolomitized carbonate reservoirs that actively produce oil and gas (Aquitaine Basin, France). In this study, the dolomitization conditions of their counterparts exhumed in the northwestern Pyrenees are detailed using a combination of field observations, petrography, fluid inclusion...

Laguna Pastos Grandes (Bolivia), nesting in a volcanic caldera, is a large, palustrine-to-lacustrine system fed by meteoric and hydrothermal calco-carbonic fluids. These different fluid inputs favor a complex mosaic of depositional environments, including hydrothermal springs, pools, and an ephemeral lake, producing abundant present-day carbonates...

Continental carbonate bodies are widespread in the Tabernas basin, eastern Betic Cordillera. Their relationships with the topographic evolution, climate changes and extensional regional tectonic processes recognized in the region are, however, still unclear. Travertine deposits exhibit facies of cascade and pool environments often reported as relat...

The exhumed Lodève Basin (Hérault, France) provides a rich suite of outcrops showing diagenetic Ba–Pb–Fe–Cu fronts trapped in karst system in Cambrian dolomites during the Triassic post-rift exhumation of the basin. The sedimentological analysis on 10 sites in the basin reveals that barites-sulfides fronts formed during humid-arid climate fluctuati...

Lacustrine carbonates formed in rift settings are increasingly studied not only as archives of Earth chemical and climatic history but also because they represent potential hydrocarbon source rocks and/or reservoirs. The role of magmatic gases in their formation and diagenetic evolution, hence in their reservoir properties, remains unclear. We stud...

In continental volcanic settings, abundant carbonate precipitation can occur with atypical facies compared with those of marine settings. The (bio-)chemical processes responsible for their development and early diagenesis are typically complex and not fully understood. In the Bolivian Altiplano, Laguna Pastos Grandes hosts a 40-km2 carbonate platfo...

Natural hydrogen (H2) seepages may represent a new promising source of energy for a low carbon society. Numerous geological evidences of natural H2 seepages and accumulation are now well identified, but our knowledge of hydrogen behavior in the crust is so limited that it is not yet possible to consider exploitation of this resource. To date, there...

Most source‐to‐sink studies typically focus on the dynamics of clastic sediments and consider erosion, transport and deposition of sediment particles as the sole contributors. Although often neglected, dissolved solids produced by weathering processes contribute significantly in the sedimentary dynamics of basins, supporting chemical and/or biologi...

The northwestern Pyrenean foreland represent an oil and gas-rich area. Hydrocarbons were mainly produced from two Jurassic dolomitized carbonate reservoirs (Bathonian to Oxfordian Meillon Formation and Tithonian Mano Formation). These pre-rift units which consist in a succession of platforms and ramps, commonly present very low permeabilities (K<1m...

The evaporation of seawater in arid climates is currently the main accepted driving mechanism for the formation of ancient and recent salt deposits in shallow basins. However, the deposition of huge amounts of marine salts, including the formation of tens of metres of highly soluble types (tachyhydrite and bischofite) during the Aptian in the South...

Diagenetic smectite dehydration and smectite-to-illite transition in clay-rich sediments can contribute to the generation of overpressure in sedimentary basins, because of the release of water associated with these mineralogical reactions. However, the challenge of deciphering the contribution of smectite dehydration and illitisation to fluid press...

Several fluid circulation events are recorded in the Aquitaine Basin and the Chaînons Béarnais in the Pyrenean belt of southwestern France. Different fluid types are found in all locations studied. The main difference comes from the thermal peak event (rifting), which was more intense in the Chaînons Béarnais close to the exhumed mantle zone. In si...

During a high pressure (up to 150 MPa) high temperature (up to 150°C) compaction experiment of MX-80 smectite equilibrated with ocean water, it was found that the Cl and Br concentrations in the expelled solution are progressively being decreased while simultaneously being increased in the compacted clay. This significant retention of Cl and Br in...

During the Albian, the hyperextension of the Pyrenean passive margin led to a hyperthinning of the continental crust and the subsequent subcontinental mantle exhumation. The giant Trimouns talc-chlorite deposit represents the most prominent occurrence of Albian metasomatism in the Pyrenees, with the occurrence of the largest talc deposit worldwide....

Although multistage hydraulic fracturing is routinely performed for the extraction of hydrocarbon resources from low permeability reservoirs, the downhole geochemical processes linked to the interaction of fracturing fluids with formation brine and reservoir mineralogy remain poorly understood. We present a geochemical dataset of flowback and produ...

The lacustrine-to-palustrine Pastos Grandes Laguna (Bolivia) is located in a volcanic caldera fed by active hot springs, with a carbonate crust extending over 40 km2. An integrated approach based on geology and hydrochemistry was used to characterize La Salsa, one of its hydrothermal systems, composed of a flat mound with a hydrothermal discharge....

The relationship between environmental conditions and the development, mineralization and preservation of modern tufa microbialites was investigated in a 1.1 km long freshwater stream in Villiers-le-Bâcle, a tributary of Mérantaise river. Detailed mapping of the tufa microbialite distribution combined with sedimentological, petrographical and miner...

Large dolomitized geobodies represent significant oil and gas reservoirs in the western north Pyrenean foreland (e.g. Lacq field: 9 tcf gas production). These pre-rift Jurassic carbonates (Bathonian to Oxfordian Meillon Formation and Tithonian Mano Formation) consist in a succession of platform and ramp of E-W polarity, which were affected by (1) t...

The polyphasic tectonic evolution of the northern Pyrenees (southern France) makes the context of foothills a privileged place for deep fluid circulations. Among these, the presence of CO 2-and H2S-rich deep brines has been identified in the South-Aquitaine oil & gas fields, trapped within Jurassic and Cretaceous carbonate formations. Expelled from...