Consulta: creatorFacets:"Ondreas, Helene"
Registros recuperados: 28
Data/hora: 02/06/2024 00:48:34

Sr‐Nd‐Hf isotopes along the Pacific Antarctic Ridge from 41 to 53°S
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Hamelin, Cedric; Dosso, Laure; Hanan, Barry; Barrat, Jean-alix; Ondreas, Helene.
Major, trace element and Sr-Nd-Hf isotope data in basalts collected along the Pacific-Antarctic Ridge ( PAR) axis between 53 and 41 S, far from any hotspot influence, reveal tight coherent geochemical variations within the depleted MORB mantle. All samples are located below the Pacific reference line defining two sub-oceanic mantle domains on each side of the Easter microplate. The data extend the PAR 66-53 S field towards more radiogenic Sr (0.70264), less radiogenic Nd (epsilon = 7.7) and Hf (epsilon = 11.4) values. The along ridge geochemical variability is closely related to the morphological segmentation of the ridge. Anomalous geochemical features are attributed to the atypical morphology of two segments due to the presence of off-axis magmatism. The...
Tipo: Text
Palavras-chave: Pacific-Antarctic; Depleted mantle; Sr-Nd-Hf isotopes.
Ano: 2010
URL: http://archimer.ifremer.fr/doc/00004/11526/8123.pdf

A detailed study of the Lucky-Strike hydrothermal site and discovery of a new hydrothermal site: « Menez-Gwen ». Preliminary results of DIVA 1 cruise (5-29 May, 1994)
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Fouquet, Yves; Charlou, Jean-luc; Donval, Jean-pierre; Radford-knoery, Joel; Pelle, P; Ondreas, Helene; Lourenco, N; Segonzac, Michel; Tivey, Mk.
Tipo: Text
Ano: 1994
URL: http://archimer.ifremer.fr/doc/00070/18134/15682.pdf

High production of H-2 and CH4 and abiotic hydrocarbons in ultramafic-hosted hydrothermal systems on the Mid-Atlantic Ridge
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Charlou, Jean-luc; Donval, Jean-pierre; Konn, Cecile; Ondreas, Helene; Fouquet, Yves; Jean-baptiste, P.; Fourre, E.
Tipo: Text
Ano: 2010
URL: http://archimer.ifremer.fr/doc/00023/13408/10480.pdf

Helium isotopes on the Pacific-Antarctic ridge (52.5°–41.5°S)
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Moreira, M; Dosso, Laure; Ondreas, Helene.
The first isotopic data and concentrations of helium are reported for the Pacific-Antarctic ridge between 52.5 degrees S and 41.5 degrees S. The He-4/He-3 ratio is extremely homogeneous over more than 1200 km, with a mean ratio of 99,275 (R/Ra = 7.29) and a standard deviation of 2719 (0.19), which is the lowest dispersion observed for the global mid oceanic ridge system. Moreover, the Menard T. F. is a frontier between two mantles with slightly different helium isotopic ratios (96,595 +/- 1520 and 100,347 +/- 2330). No difference in the helium concentration between the two ridge segments defined by the Menard T. F. can be observed, as well as no significant difference in the U and Th contents suggesting that the difference in helium isotopic ratio is old...
Tipo: Text
Palavras-chave: Pacific Antarctic ridge; Mantle geochemistry; Helium isotopes.
Ano: 2008
URL: http://archimer.ifremer.fr/doc/2008/publication-4348.pdf

Menes caldera, a highly active site of brine seepage in the Eastern Mediterranean sea: "In situ" observations from the NAUTINIL expedition (2003)
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Huguen, Caroline; Foucher, Jean-paul; Mascle, J.; Ondreas, Helene; Thouement, M.; Gontharet, S.; Stadnitskaia, A.; Pierre, C.; Bayon, Germain; Loncke, L.; Boetius, A.; Bouloubassi, I.; De Lange, G.; Caprais, Jean-claude; Fouquet, Yves; Woodside, J.; Dupre, Stephanie.
This paper reports the first "in situ" seafloor observations of fluid escape structures in a fault-controlled caldera-type depression of about 8 km diameter, named the Menes caldera, in the Eastern Mediterranean sea off Egypt (western province of the Nile Deep Sea Fan). A detailed analysis of seven Nautile dives, performed during the Nautinil cruise in 2003, focused on determining the nature, origin, importance, mechanisms and environmental impacts of the fluid escape processes from the geological observations. Seafloor maps, constructed from direct visual observations and video records made from the submersible, and sampling results, for three mud volcanoes of the caldera, Cheops, Chephren and Mykerinos show differences in activity but many common...
Tipo: Text
Palavras-chave: Mediterranean Sea; Nile Deep Sea Fan; Mud volcano; Brine seep.
Ano: 2009
URL: http://archimer.ifremer.fr/doc/00000/11089/10627.pdf

ROV study of a giant pockmark on the Gabon continental margin
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Ondreas, Helene; Olu, Karine; Fouquet, Yves; Charlou, Jean-luc; Gay, Aurelien; Dennielou, Bernard; Donval, Jean-pierre; Fifis, Alexis; Nadalig, Thierry; Cochonat, Pierre; Cauquil, E; Bourillet, Jean-francois; Le Moigne, Morgan; Sibuet, Myriam.
A giant, 800-m wide pockmark, called Regab, was discovered along the Equatorial African margin at 3160-m water depth and was explored by remote operated vehicle (ROV) as part of the Zaiango (1998-2000) and Biozaire (2001-2003) projects carried out conjointly by TOTAL and a number of French research institutes. A microbathymetric map obtained using the ROV sensors shows that the pockmark actually consists of a cluster of smaller pockmarks aligned N70 along a 15-m deep depression. Methane was recorded all over the pockmark, the highest values along the axis of the depression where massive carbonate crusts and dense seep communities were also found. Several faunal species belong to the Vesicomyidae and Mytilidae bivalve families, as well as to Siboglinidae...
Tipo: Text
Palavras-chave: Gabon; Microbathymetric map; ROV; Exploration; Pockmark; Equatorial African margin.
Ano: 2005
URL: http://archimer.ifremer.fr/doc/2005/publication-1239.pdf

Multi-disciplinary investigation of fluid seepage on an unstable margin: The case of the Central Nile deep sea fan
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Bayon, Germain; Loncke, L.; Dupre, Stephanie; Caprais, Jean-claude; Ducassou, E.; Duperron, Sebastien; Etoubleau, Joel; Foucher, Jean-paul; Fouquet, Yves; Gontharet, S.; Henderson, G. M.; Huguen, Caroline; Klaucke, I.; Mascle, J.; Migeon, S.; Olu-le-roy, Karine; Ondreas, Helene; Pierre, C.; Sibuet, Myriam; Stadnitskaia, A.; Woodside, J.
We report on a multidisciplinary study of cold seeps explored in the Central Nile deep-sea fan of the Egyptian margin. Our approach combines in situ seafloor observation, geophysics, sedimentological data, measurement of bottom-water methane anomalies, pore-water and sediment geochemistry, and Th-230/U dating of authigenic carbonates. Two areas were investigated, which correspond to different sedimentary provinces. The lower slope, at similar to 2100 m water depth, indicates deformation of sediments by gravitational processes, exhibiting slope-parallel elongated ridges and seafloor depressions. In contrast, the middle slope, at similar to 1650 m water depth, exhibits a series of debris-flow deposits not remobilized by post-depositional gravity processes....
Tipo: Text
Palavras-chave: Authigenic carbonate; U Th; Cold seep; Continental margin; Nile.
Ano: 2009
URL: http://archimer.ifremer.fr/doc/2009/publication-6586.pdf

Dynamics of gas hydrate: case of the Congo continental slope
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Sultan, Nabil; Foucher, Jean-paul; Cochonat, Pierre; Tonnerre, T; Bourillet, Jean-francois; Ondreas, Helene; Cauquil, E; Grauls, D.
A numerical model is developed to study the temperature effect on stability and phase transformation of gas-hydrate. The model uses a mathematical formulation based on the enthalpy form of the conservation law of energy. The use of the enthalpy form instead of the temperature form as often done in the literature has made the problem numerically simpler. The model is then applied to describe the effect of sea bottom temperature variations on the stability of gas hydrate occurrences and on the seafloor reflectivity in sediments of the Congo continental slope. Indeed, a migrating seafloor reflectivity front is observed on 3D seimic images from two surveys performed 6 months apart and interpreted as a migrating gas hydrate stability zone. Seawater temperature...
Tipo: Text
Palavras-chave: Temperature; Stefan problem; Seafloor reflectivity; Gas hydrate; Heat flow; Finite difference; Continental margins.
Ano: 2004
URL: http://archimer.ifremer.fr/doc/2004/publication-702.pdf

Seafloor facies related to upward methane flux within a Giant Pockmark of the Lower Congo Basin
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Gay, Aurelien; Lopez, M; Ondreas, Helene; Charlou, Jean-luc; Sermondadaz, G; Cochonat, Pierre.
The origin of the cold fluid venting from a Giant Pockmark within the Lower Congo Basin has been elucidated based upon results of precise mapping, submersible dives, gravity coring and isotopic analyses realized under a TOTAL-IFREMER cooperative project (ZAIANGO and BIOZAIRE projects). During four dives of the IFREMER ROV-Victor 6000, the bottom was filmed, hard and soft samples were lifted from the sediment, and water samples were collected with a CTD-rosette system. The detailed dip map shows that the 800 in wide Giant Pockmark is a composite feature due to the coalescence of multiple 100 in wide depressions that displays a broad range of biological, mineralogical and chemical features on the seafloor, leading to a seafloor anomaly recorded on the...
Tipo: Text
Palavras-chave: BIOZAIRE; ZAIANGO; Palaeochannel; Hydrates; Chemosynthesis; Seafloor facies; Fluid migration; Pockmark.
Ano: 2006
URL: http://archimer.ifremer.fr/doc/2006/publication-1114.pdf

Victor 6000: New high resolution tools for deep sea research. « Module de Mesures en Route »
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Simeoni, Patrick; Sarrazin, Jozee; Nouze, Herve; Sarradin, Pierre-marie; Ondreas, Helene; Scalabrin, Carla; Sinquin, Jean-marc.
This paper describes the new survey module (called "Module de Mesures en Route"), of the Remotely Operated Vehicle (ROV) Victor 6000 and presents the first results obtained during two scientific cruises held during the summer of 2006 (Viking and Momareto).
Tipo: Text
Ano: 2007
URL: http://archimer.ifremer.fr/doc/2007/publication-3596.pdf

Geological and biological diversity of seeps in the Sea of Marmara
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Ondreas, Helene; Olu, Karine; Dupre, Stephanie; Scalabrin, Carla; Alix, Anne-sophie; Garrocq, Clément; Ruffine, Livio.
The Sea of Marmara hosts part of the North Anatolian Fault as an active submarine strike-slip fault. This area has suffered numerous earthquakes and presents a major seismic risk. Although the Sea of Marmara has been studied for many years, the link between geological morphostructures, the nature of fluids and biological communities is still rarely described. During the Marsite cruise (November 2014), dives with Remotely Operated Vehicle (ROV) VICTOR 6000 focused on detailed seafloor explorations of four different areas: the Central and Western highs and the Tekirdağ and Çinarcik basins. Based on 130 h of in situ videos, high-resolution seafloor mapping of seeps was conducted, emphasizing their significant geological and biological diversity from one...
Tipo: Text
Palavras-chave: Sea of Marmara; Cold seeps; Fluids; Seismogenic faults; Chemosynthetic fauna; Methane.
Ano: 2020
URL: https://archimer.ifremer.fr/doc/00624/73623/73040.pdf

Variabilité morphostructurale à l'échelle kilométrique de la dorsale du Bassin Nord-Fidjien : exploration in situ du segment compris entre 18°50S et 19°S
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Ondreas, Helene; Ruellan, Etienne; Auzende, Jean-marie; Bendel, V; De Alteriis, G; Gracia Mont, Eulalia; Tanahashi, M.
During the STARMER programme the submersibles Nautile and Shinkai-6500 carried out 14 dives on the NS segment of the North Fiji Basin Ridge (Station 14 at 18-degrees-50 S). From structural point of view, two types of morphology appear: in the northern part, the axis is not tectonically well expressed hut the hydrothermal activity is important. in the southern part, a graben structure 150 m wide exists, with both a.fossil and a present-day hydrothermal activity. The station 14 shows a morphostructural variability of the spreading axis which can be related to the different stages of the volcanic and tectonic cycles. Another station explored at 19-degrees-S, a few kilometres to the south, confirms the fact that different stages of tectonic and magmatic...
Tipo: Text
Ano: 1993
URL: http://archimer.ifremer.fr/doc/00184/29476/27855.pdf

New structural and geochemical observations from the Pacific-Antarctic Ridge between 52°45'S and 41°15'S
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Klingelhoefer, Frauke; Ondreas, Helene; Briais, A; Hamelin, C; Dosso, Laure.
We investigated the morphology and structure of the Pacific-Antarctic Ridge between 52 degrees 45'S and 41 degrees 15'S during the Pacantarctic2 cruise using multibeam echosounder together with gravity measurements and dredges. Analysis of the bathymetric, gravity and geochemical data reveal three ridge segments separated by overlapping spreading centers south of the Menard transform fault (MTF) and five segments north of it. Calculation of the cross-sectional area allows quantification of the variation in size of the axial bathymetric high. Together with the calculation of the mantle Bouguer anomaly, these data provide information about variations in the temperature of the underlying mantle or in crustal thickness. Areas with hotter mantle are found north...
Tipo: Text
Palavras-chave: Mantle Bouguer anomaly; Temperature variations; Geochemistry; Gravity; Bathymetry; Ridge segment.
Ano: 2006
URL: http://archimer.ifremer.fr/doc/2006/publication-2108.pdf

Fluid flow regimes and growth of a giant pockmark
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Marcon, Yann; Ondreas, Helene; Sahling, Heiko; Bohrmann, Gerhard; Olu, Karine.
Pockmarks are seafloor depressions commonly associated with fluid escape from the seabed and are believed to contribute noticeably to the transfer of methane into the ocean and ultimately into the atmosphere. They occur in many different areas and geological contexts, and vary greatly in size and shape. Nevertheless, the mechanisms of pockmark growth are still largely unclear. Still, seabed methane emissions contribute to the global carbon budget, and understanding such processes is critical to constrain future quantifications of seabed methane release at local and global scales. The giant Regab pockmark (9 degrees 42.6' E, 5 degrees 47.8' S), located at 3160 m water depth near the Congo deep-sea channel (offshore southwestern Africa), was investigated...
Tipo: Text
Ano: 2014
URL: http://archimer.ifremer.fr/doc/00186/29731/28293.pdf

Cold-seep assemblages on a giant pockmark off West Africa: spatial patterns and environmental control
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Olu, Karine; Caprais, Jean-claude; Fifis, Alexis; Fabri, Marie-claire; Galeron, Joelle; Budzinsky, H; Le Menach, K; Khripounoff, Alexis; Ondreas, Helene; Sibuet, Myriam.
A giant pockmark colonised by dense cold-seep assemblages near 3160 m depth along the Congo-Angola margin has been surveyed by the ROV Victor 6000. The quantitative distribution of chemosynthetic communities was mapped along the dive tracks from a video study using GIS and image mosaicking. Several types of faunal assemblages, either dominated by bivalves of the families Mytilidae (Bathmodiolus sp.) Vesicom idae (Calyptogena sp., 'Vesicomya' aff. chuni), or by Siboglinidae polychaetes (Escarpia southwardae) were mapped over the 800-m diameter pockmark area and sampled for fauna, water and sediment. The isotopic analyses (delta C-13) of tissues from symbiont-bearing species were within the range typical of nutrition via symbiosis using methane for mussels...
Tipo: Text
Palavras-chave: Symbiont bearing species; Spatial distribution; Methane; Megafauna; Cold seeps.
Ano: 2007
URL: http://archimer.ifremer.fr/doc/2007/publication-2681.pdf

Variations in axial morphology, segmentation, and seafloor roughness along the Pacific-Antarctic Ridge between 56 degrees S and 66 degrees S
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Ondreas, Helene; Aslanian, Daniel; Geli, Louis; Olivet, Jean-louis; Briais, Anne.
The spreading rate at the Pacific-Antarctic Ridge (PAR) increases rapidly from 54 mm/yr near Pitman Fracture Zone (FZ) up to 76 mm/yr near Udintsev FZ, resulting in three domains of axial morphology: an axial valley south of Pitman FZ, an axial high north of Saint Exupery FZ, and in between, the transitional domain extends over 650 km. It comprises sections of ridge with an axial valley or an axial high and generally displays a very low cross-sectional relief. It is also characterized by two propagating rifts. Two domains of different seafloor roughness appear south of Udintsev FZ: east of 157 degreesW these two domains are separated by a 1000-km V-shaped boundary. West of 157 degreesW, the boundary approximately coincides with Chron 3a or Chron 4. The...
Tipo: Text
Palavras-chave: Spreading; Segmentation; Geomorphology; Seafloor; Ridge.
Ano: 2001
URL: https://archimer.ifremer.fr/doc/2001/publication-438.pdf

Seafloor geological studies above active gas chimneys off Egypt (Central nile deep sea fan)
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Dupre, Stephanie; Woodside, J; Foucher, Jean-paul; De Lange, G; Mascle, J; Boetius, A; Mastalerz, V; Stadnitskaia, A; Ondreas, Helene; Huguen, C; Harmegnies, Francois; Gontharet, Swanne; Loncke, L; Deville, E; Niemann, H; Omoregie, E; Olu, Karine; Fiala Medioni, A; Dahlmann, A; Caprais, Jean-claude; Prinzhofer, A; Sibuet, Myriam; Pierre, C; Damste, J.
Four mud volcanoes of several kilometres diameter named Amon, Osiris, Isis, and North Alex and located above gas chimneys on the Central Nile Deep Sea Fan, were investigated for the first time with the submersible Nautile. One of the objectives was to characterize the seafloor morphology and the seepage activity across the mud volcanoes. The seepage activity was dominated by emissions of methane and heavier hydrocarbons associated with a major thermal contribution. The most active parts of the mud volcanoes were highly gas-saturated (methane concentrations in the water and in the sediments, respectively, of several hundreds of nmol/L and several mmol/L of wet sediment) and associated with significantly high thermal gradients (at 10 m below the seafloor,...
Tipo: Text
Palavras-chave: Seafloor morphology; Methane; Authigenic carbonate precipitation; Gas chimneys; Mud breccia; Mud volcanoes; Fluid seepage; Nile fan.
Ano: 2007
URL: http://archimer.ifremer.fr/doc/2007/publication-4455.pdf

Cartographie haute résolution des champs hydrothermaux de la ride sud du bassin de Guaymas
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Ondreas, Helene; Scalabrin, Carla; Fouquet, Yves; Godfroy, Anne.
Insights into the factors controlling fluid circulation through the crust and the nature of fluid venting at the seafloor are first steps in understanding their effect on ocean properties and climate change. New data on the seafloor morphology, sub-surface sedimentary stratification, and water column of the sedimented Southern Trough hydrothermal field (Guaymas basin) were acquired during the BIG cruise in 2010. These data provide accurate and high-resolution information on the geological context of the vents, on the distribution of acoustic anomalies in the water column, and on the possible nature of the fluid generating these echoes. More than 40 hydrothermal edifices were observed. The southern zone of the study area hosts hydrothermal sites that differ...
Tipo: Text
Palavras-chave: Mid-ocean ridges; Sedimented ridge; Hydrothermal systems; Fluid migration; Water-column acoustic images; Guaymas basin.
Ano: 2018
URL: https://archimer.ifremer.fr/doc/00436/54775/56229.pdf

Recent volcanic events and the distribution of hydrothermal venting at the Lucky Strike hydrothermal field, Mid-Atlantic Ridge
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Ondreas, Helene; Cannat, M.; Fouquet, Yves; Normand, Alain; Sarradin, Pierre-marie; Sarrazin, Jozee.
We present new high-resolution bathymetry and backscatter data acquired in 2006 with the ROV Victor 6000 over the Lucky Strike hydrothermal field, Mid-Atlantic Ridge. As long-term monitoring of the Lucky Strike area (MoMAR project) is being implemented, these new high-resolution data offer an unprecedented view of the distribution of hydrothermal edifices, eruptive facies, and small-scale tectonic features in the Lucky Strike vent field. We show that vents located in the NW and NE correspond with wide expanses of lumpy seafloor which we interpret as primarily made of broken chimneys and sulfide edifices. They are found above scarps with relief &gt; 50 m or on associated mass wasting deposits. By contrast, the SE and SW vents correspond with small expanses...
Tipo: Text
Palavras-chave: Hydrothermalism; Lava lake; Lucky Strike; Mid Atlantic Ridge.
Ano: 2009
URL: http://archimer.ifremer.fr/doc/2009/publication-6161.pdf

Accrétion océanique et déformation dans la partie méridionale du bassin Nord-Fidjien: résultats préliminaires de la campagne océanographique SEAPSO III du N.O. Jean-Charcot (décembre 1985)
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Auzende, Jean-marie; Eissen, Jean-philippe; Caprais, Marie-paule; Gente, Pascal; Gueneley, S; Harmegnies, Francois; Lagabrielle, Yves; Lapouille, A; Lefevre, C; Maillet, P; Maze, Jean-pierre; Ondreas, Helene; Schaaf, A; Singh, R.
Seismic, Seabeam, magnetic and gravimetrie surveys in the southern part of the N-Fiji basin were conducted during the SEAPSO LEG III Cruise. The active spreading axis was recognized between 17°30'S and 21°S. It consists of a continuous N-S Ridge cross-cut by transverse directions oriented N25 and N45. North of 17°30'S, the spreading System is more complex due to the existence of a possible triple junction located around 15° S. The eastern part of the N-Fiji basin, west of Viti Levu is mostly characterized by alternating highs and deeps (&lt;4,000 m). This area must be regarded no more as a spreading center, but as complex boundary suffering transverse tectonics.
Tipo: Text
Ano: 1986
URL: http://archimer.ifremer.fr/doc/00184/29492/27835.pdf

FLORES diving cruise with Nautile near the Azores - First dives on the Rainbow field: hydrothermal seawater/mantle interaction
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Fouquet, Yves; Barriga, F; Charlou, Jean-luc; Elderfield, H; German, C.r; Ondreas, Helene; Parson, L; Radford-knoery, Joel; Relvas, J; Ribeiro, A; Schultz, A; Apprioual, R; Cambon, P; Costa, I; Donval, Jean-pierre; Douville, E; Landure, Jy; Normand, A; Pelle, H; Ponsevera, E.
Tipo: Text
Ano: 1998
URL: http://archimer.ifremer.fr/doc/00070/18133/15681.pdf

Origin of volcanism on the flanks of the Pacific-Antarctic ridge between 41°30'S and 52°S
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Briais, Anne; Ondreas, Helene; Klingelhoefer, Frauke; Dosso, Laure; Hamelin, Cedric; Guillou, Herve.
Non-hot spot, intraplate volcanism is a common feature near the East Pacific Rise or Pacific-Antarctic ridge. Volcanic ridges and seamount chains, tens to hundreds of kilometers long, are asymmetrically distributed about the ridge axis, with most volcanic features occurring on the Pacific plate. Their origins remain controversial. We have analyzed off-axis volcanic ridges near the Pacific-Antarctic ridge from bathymetry, backscatter, gravity, and geochemistry data of the Pacantarctic 2 cruise. K/Ar dating of samples dredged on these structures reveals a contrast of up to 3 Ma between the volcanoes and the underlying crust. The volcanic activity, as suggested by the strong backscatter in sonar images, appears to be limited to areas of seafloor younger than...
Tipo: Text
Palavras-chave: Mid ocean ridges; Off axis volcanism; Mantle convection; Plate kinematics; Transform fault.
Ano: 2009
URL: http://archimer.ifremer.fr/doc/00000/11106/7968.pdf

Trace element behaviour at cold seeps and the potential export of dissolved iron to the ocean
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Lemaitre, Nolwenn; Bayon, Germain; Ondreas, Helene; Caprais, Jean-claude; Freslon, Nicolas; Bollinger, Claire; Rouget, Marie-laure; De Prunele, Alexis; Ruffine, Livio; Olu-le Roy, Karine; Sarthou, Geraldine.
Seawater samples were collected by submersible above methane seeps in the Gulf of Guinea (Regab and Baboon pockmarks) in order to investigate the behaviour of iron (Fe), manganese (Mn) and rare earth elements (REE) during fluid seepage. Our aim was to determine whether cold seeps may represent potential sources of dissolved chemical species to the ocean. Dissolved (&lt;0.45 μm filtered samples) and total dissolvable (unfiltered samples) concentrations were determined over ∼50 m long vertical transects above the seafloor and at various discrete locations within the pockmarks. We show that substantial amounts of Fe and Mn are released into seawater during seepage of methane-rich fluids. Mn is exported almost quantitatively in the dissolved form (more than...
Tipo: Text
Palavras-chave: Iron; Rare earth elements; Cold seeps; Seawater; Organic ligands; Iron-sulfide nanoparticles.
Ano: 2014
URL: http://archimer.ifremer.fr/doc/00211/32190/30704.pdf

High-resolution bathymetry reveals contrasting landslide activity shaping the walls of the Mid-Atlantic Ridge axial valley
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Cannat, Mathilde; Mangeney, Anne; Ondreas, Helene; Fouquet, Yves; Normand, Alain.
Axial valleys are found along most slow-spreading mid-ocean ridges and are one of the most prominent topographic features on Earth. In this paper, we present the first deep-tow swath bathymetry for the axial valley walls of the Mid-Atlantic Ridge. These data allow us to analyze axial valley wall morphology with a very high resolution (0.5 to 1 m compared to 50 m for shipboard multibeam bathymetry), revealing the role played by landslides. Slow-spreading ridge axial valleys also commonly expose mantle-derived serpentinized peridotites in the footwalls of large offset normal faults (detachments). In our map of the Ashadze area (lat. 13 degrees N), ultramafic outcrops have an average slope of 18 degrees and behave as sliding deformable rock masses, with...
Tipo: Text
Palavras-chave: Landslides; Detachment faults; Basalts; Mid-ocean ridges; Serpentinized peridotites.
Ano: 2013
URL: https://archimer.ifremer.fr/doc/00284/39516/38004.pdf

The use of multibeam backscatter and bathymetry as a means of identifying faunal assemblages in a deep-sea cold seep
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Sen, Arunima; Ondreas, Helene; Gaillot, Arnaud; Marcon, Yann; Augustin, Jean-marie; Olu, Karine.
Deep-sea ecosystems have attracted considerable commercial interest in recent years because of their potential to sustain a diverse range of mankind's industrial needs. If these systems are to be preserved or exploited in a sustainable manner, mapping habitats and species distributions is critical. As biodiversity at cold-seeps or other deep-sea ecosystems is driven by habitat heterogeneity, imagery is the obvious choice for characterizing these systems and has indeed proven extremely valuable towards mapping biogenic habitats formed by dense aggregations of large sized species, such as coral reefs, tubeworm bushes or bivalve beds. However, the acquisition of detailed images with resolution sufficient for reliable identification is extremely time...
Tipo: Text
Palavras-chave: Mapping; Cold seeps; Multibeam; Bathymetry; Backscatter; Biogenic habitats.
Ano: 2016
URL: http://archimer.ifremer.fr/doc/00312/42286/41612.pdf

Multidisciplinary investigation on cold seeps with vigorous gas emissions in the Sea of Marmara (MarsiteCruise): Strategy for site detection and sampling and first scientific outcome
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Ruffine, Livio; Ondreas, Helene; Blanc-valleron, Marie-madeleine; Teichert, Barbara M. A.; Scalabrin, Carla; Rinnert, Emmanuel; Birot, Dominique; Croguennec, Claire; Ponzevera, Emmanuel; Pierre, Catherine; Donval, Jean-pierre; Alix, Anne-sophie; Germain, Yoan; Bignon, Laurent; Etoubleau, Joel; Caprais, Jean-claude; Knoery, Joel; Lesongeur, Francoise; Thomas, Bastien; Roubi, Angelique; Legoix, Ludovic Nicolas; Burnard, Pete; Chevalier, Nicolas; Lu, Hailong; Dupre, Stephanie; Fontanier, Christophe; Dissard, Delphine; Olgun, Nazli; Yang, Hailin; Strauss, Harald; Ozaksoy, Volkan; Perchoc, Jonathan; Podeur, Christian; Tarditi, Corinne; Ozbeki, Eyyup; Guyader, Vivien; Marty, Bernard; Madre, David G; Pitel-roudaut, Mathilde; Grall, Celine; Embriaco, Davide; Polonia, Mina; Gasperini, Lucas; Cagatay, M. Namik; Henry, Pierre; Geli, Louis.
MarsiteCruise was undertaken in October/November 2014 in the Sea of Marmara to gain detailed insight into the fate of fluids migrating within the sedimentary column and partially released into the water column. The overall objective of the project was to achieve a more global understanding of cold-seep dynamics in the context of a major active strike-slip fault. Five remotely operated vehicle (ROV) dives were performed at selected areas along the North Anatolian Fault and inherited faults. To efficiently detect, select and sample the gas seeps, we applied an original procedure. It combines sequentially (1) the acquisition of ship-borne multibeam acoustic data from the water column prior to each dive to detect gas emission sites and to design the tracks of...
Tipo: Text
Palavras-chave: Acoustic survey; Authigenic carbonates; Biogeochemistry; Chemical analyses; Cold seeps; Dissolved major elements; Fluid seepage; Geology; In situ Raman analysis; Methane; ROV dives.
Ano: 2018
URL: https://archimer.ifremer.fr/doc/00433/54434/55783.pdf

Résultats préliminaires des plongées du Shinkai 6500 sur la dorsale du Bassin Nord-Fidjien (SW Pacifique) — Programme STARMER
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Auzende, Jean-marie; Tanahashi, M; Bendel, V; Fujikura, K; Geistdoerfer, P; Gracia Mont, Eulalia; Joshima, M; Kisimoto, K; Mitsuzawa, K; Murai, M; Nojiri, Y; Ondreas, Helene; Pratt, C; Ruellan, Etienne.
The aim of the YOKOSUKA 91 cruise (October 1991) of the Japanese submersible Shinkai 6500 was to come back on two hydrothermal sites of the axis of the North Fiji Basin ridge which had already been explored by the submersible Nautile in 1989. This cruise gave us the opportunity to show that the hydrothermal manifestations vary a lot in terms of geology, geochemistry or biology during a very short time. A new site which is located in a deep graben of the N 160 ridge axis showed only activity along a fault system marked by sulphide deposits.
Tipo: Text
Ano: 1992
URL: http://archimer.ifremer.fr/doc/00184/29486/27854.pdf

Geological context and vents morphology of the ultramafic-hosted Ashadze hydrothermal areas (Mid-Atlantic Ridge 13 degrees N)
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Ondreas, Helene; Cannat, Mathilde; Fouquet, Yves; Normand, Alain.
Recent ROV dives and high-resolution bathymetric data acquired over the Ashadze fields on the Mid-Atlantic Ridge (13 degrees N) allow us to derive constraints on the regional and local geological setting of ultramafic-hosted hydrothermal fields. The active vent fields of Ashadze hydrothermal fields are located in the western axial valley wall, downslope from the termination of a prominent corrugated surface and in a transitional domain with respect to ridge segmentation. The study of the shipboard and ROV bathymetry shows that decameter (100 m by 60 m) to kilometer-scaled rockslides shape the axial valley wall slopes in this region. The Ashadze 1 vent field occurs on a coherent granular landslide rock mass that is elongated in an E-W direction. The Ashadze...
Tipo: Text
Palavras-chave: Ashadze; Mid-Atlantic Ridge; Hydrothermal activity; Hydrothermal explosion crater; Ultramafic rocks.
Ano: 2012
URL: http://archimer.ifremer.fr/doc/00111/22223/19895.pdf