J.P. Donval

Institut Français de Recherche pour l'Exploitation de la Mer | Ifremer

The Menez Gwen, Lucky Strike, Rainbow, TAG (Transatlantic Geotraverse) and Snake Pit hydrothermal vent fields on the Mid-Atlantic Ridge were revisited and resampled for geochemical investigation during the BIOBAZ 2013 and BICOSE 2014 research cruises. Geochemical analysis of the major and minor elements of the hydrothermal fluid and concentrations...

Carbon dioxide (CO2) and methane (CH4) are two climate-sensitive components of gases migrating within sediments and emitted into the water column on continental margins. They are involved in several key biogeochemical processes entering into the global carbon cycle. In order to perform onboard measurements of both the molecular and stable carbon is...

Understanding the dynamics and fate of methane (CH4) release from oceanic seepages on margins and shelves into the water column, and quantifying the budget of its total discharge at different spatial and temporal scales, currently represents a major scientific undertaking. Previous works on the fate of methane escaping from the seafloor underlined...

So far, the natural recovery of vent communities at large scales has only been evaluated at fast spreading centres, by monitoring faunal recolonisation after volcanic eruptions. However, at slow spreading ridges, opportunities to observe natural disturbances are rare, the overall hydrothermal system being more stable. In this study, we implemented...

The measurement of methane clumped isotopologues (Δ13CH3D and Δ12CH2D2) allows exploring isotope bond ordering within methane molecules, and may reveal equilibrium temperatures. Whether such temperature reflects the formation or re-equilibration temperature of the methane is not well understood, but would have critical implications for the use of m...

Natural Gas Hydrates (NGH) collected during the Ghass cruise 2015 in the Western Black Sea onboard the R/V Pourquoi pas? are characterized by a suite of techniques. Gas Chromatography and Raman spectroscopy are used for the identification of the nature of the gas source, the hydrate structure and spatial variability of cage occupancies. The nature...

Environmental sciences are expanding and are based on standardized and certified calibrations when measurements are required. When a gaseous composition is quantified, commercial standards are used. Here, we report on a two-component device for the preparation and injection of gas mixtures at the appropriate levels of pressure and volume. The two-c...

The study area is located at the transition between the northern end of the Tonga Trench and the North Fiji fracture zone, where tectonic movements are reputed to be the fastest in the world. To the southeast of Futuna Island, a broad area of volcanism occurs within a region characterized by a change in the tectonic fabric between a NE-SW oriented...

The observation of densely concentrated chemosynthetic communities at hydrate deposits has motivated the need for developing multidisciplinary and multitool‐based approaches combining geochemistry, microbiology and biology to investigate the interplays between hydrate geochemical dynamics and the development of such ecosystems. This chapter starts...

Two newly discovered hydrothermal vent fields of the Wallis and Futuna region, Kulo Lasi and Fatu Kapa, were sampled for fluid geochemistry. A great geochemical diversity was observed and assigned to the diversity of lithologies as well as the occurrence of various processes. Kulo Lasi fluids likely formed by interaction with fresh volcanic rocks,...

The Niger Delta is one of the largest hydrocarbon basin offshore Africa and it is well known for the presence of active pockmarks on the seabed. During the Guineco-MeBo cruise in 2011, long cores were taken from a pockmark cluster in order to investigate the state of its current activity. Gas hydrates, oil and pore-water were sampled for geochemica...

“Headspace” technique is one of the methods for the onboard measurement of hydrogen (H2) and methane (CH4) in deep seawater. Based on the principle of an automatic headspace commercial sampler, a specific device has been developed to automatically inject gas samples from 300 ml syringes (gas phase in equilibrium with seawater). As valves, micro pum...

The study area is close to the Wallis and Futuna Islands in the French EEZ. It exists on the western boundary of the fastest tectonic area in the world at the junction of the Lau and North-Fiji basins. At this place, the unstable back-arc accommodates the plate motion in three ways: (i) the north Fiji transform fault, (ii) numerous unstable spreadi...

The EEZ of Wallis and Futuna is located west of the collision zone between the Pacific plate and the Australian plate. In this area, at the north of the Tonga Trench, the fastest plate movement in the world is recorded (24 cm / year). An area of 350x250 km has been explored between 2010 and 2013. Of the 52 200 km2 mapped, almost 60% consist of rece...

As part of a Public Private consortium, explorations to locate sulfide mineralization in the French EEZ of Wallis and Futuna allowed to discover new hydrothermal fields. Three cruises organized between 2010 and 2012 have explored this area. The first phase focused on a regional mapping to find areas of recent volcanism using multibeam echosounders...

For many trace elements, continental margins are the location of intense exchange processes between sediment and seawater, which control their distribution in the water column, but have yet to be fully understood. In this study, we have investigated the impact of fluid seepage at cold seeps on the marine cycle of neodymium. We determined dissolved...

A novel variable-volume type high-pressure apparatus has been designed, constructed and used for gas hydrate investigations. The apparatus has an operating temperature ranging from 253 K to 473 K and pressure ranging from 0.1 MPa to 60 MPa. Its central component consists of a viewing windows cell to which several sensors or analytical instruments c...

Between 12° and 40°N on the Mid-Atlantic Ridge (MAR), high- or low-temperature hydrothermal activity and mantle degassing are indicative of ongoing serpentinization process. Chemical composition of fluids from ultramafic-hosted hydrothermal fields (Rainbow, 36°14' N; Lost City, 30°N Logatchev I and II, 14°45' N; Ashadze I and II, 12°58' N), all loc...

Several hydrothermal deposits associated with ultramafic rocks have recently been found along slow spreading ridges with a low magmatic budget. Three preferential settings are identified: (1) rift valley walls near the amagmatic ends of ridge segments; (2) nontransform offsets; and (3) ultramafic domes at inside corners of ridge transform-fault int...

The first building blocks of life could be produced in ultramafic-hosted hydrothermal systems considering the large amounts of hydrogen and methane generated by serpentinisation and Fischer–Tropsch-Type synthesis, respectively, in those systems. The purpose of this study was to detect and characterise organic molecules in hydrothermal fluids from u...

Headspace technique is a common method to analyze light hydrocarbons in deep marine sediments. The use of an automatic headspace sampler instead of a manual injection is the guarantee for a better repeatability and furthermore it is less time consuming. But to increase the sensitivity and therefore, to achieve a better detection limit, it is necess...

As part of a multidisciplinary project aimed at studying mid-ocean ridge processes near the Azores, fifty water column profiles were analyzed for 3He/4He ratios in dissolved helium (a well-known hydrothermal tracer) from 36°N to 40°N along the Mid-Atlantic Ridge (MAR) and over the Azores Plateau. As expected, large delta 3He anomalies could be obse...

As a part of the ZAIANGO IFREMER/TOTAL-FINA-ELF program, gas hydrates were collected from a gravity sediment core on the Congo–Angola margin during the ZAI-ROV cruise (December 2000). Gas hydrates, associated with a deep giant (800 m in diameter) active depression called “pockmark,” occurred from the sediment surface down to 12 m depth, at 3160 m w...

The Flores diving cruise was part of the MAST III-AMORES (1995–1998) program funded by the European Union. One of the major achievements of the Flores cruise was the discovery of the Rainbow hydrothermal field hosted in ultramafic rocks south of the Amar segment on the Mid-Atlantic ridge (MAR). The Rainbow hydrothermal fluids exhibit temperatures o...

Fluids were collected from the Rainbow vent field (36°14′N) on the Mid-Atlantic Ridge (MAR) during the 1997 diving FLORES cruise. This vent field, in ultramafic rocks at a depth of 2300 m, is composed of ∼10 black smokers emitting acidic (pH∼2.8) fluids at 365 °C. The low pH of the hot-temperature Rainbow fluids likely results from seawater–ultrama...

During the DIVA 1 cruise in May 1994, a series of 19 dives was conducted using the French submersible Nautile at the topographic highs of three volcanic segments centered at 37°17′N, 37°50′N and 38°20′N, respectively, south of the Azores Triple Junction (ATJ) on the Mid-Atlantic Ridge (MAR). Hydrothermal fluids were collected at the Lucky Strike (L...

As part of a multidisciplinary research effort aimed at quantifying mid-ocean ridge processes near the Azores, we conducted a survey of the water column above the mid-Atlantic Ridge (MAR) in the vicinity of the Azores Triple Junction. Manganese is a tracer of hydrothermal activity intimately related to mid-ocean ridge processes. This paper reports...

During the 1994 DIVA-1 cruise, the distribution of sulfide, methane and total dissolvable manganese (TDM) in the water column was examined near the seafloor at two locations on the mid-Atlantic ridge (MAR) affected by hydrothermal venting. Samples for this study were obtained using a miniature rosette mounted on the Nautile submersible and hydrogra...

Given a multigraph G = (V, E), the Edge Coloring Problem (ECP) calls for the minimum number  of colors needed to color the edges in E so that all edges incident with a common node are assigned different colors. The best known polynomial time approximation algorithms for ECP belong to a same family, which is likely to contain, for each positive int...

The Lau Basin, a back arc spreading center, is one of the most active hydrothermal areas in the ocean. A scientific team from France, Germany, and Tonga investigated the southern Lau Basin near Tonga in 1989 to study the processes of seafloor ore-mineral formation associated with hydrothermal circulation along the volcanic Valu Fa ridge (Ride de Va...

During the French-German cruise Nautile(April-May 1989), 22 dives have been completed to understand the processes of seafloor arc formation associated with hydrothermal circulation along the volcanic Valu FA ridge. The CTD recordings, obtained in real time inside the Nautile, show the narrow relation between the geological structure and the tempera...