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| Registros recuperados: 28 | |
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| 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 |
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| 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 |
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| 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 |
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| 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 |
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| 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 |
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| 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 |
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| 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 |
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| 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 |
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| Ano: 1993 |
URL: http://archimer.ifremer.fr/doc/00184/29476/27855.pdf |
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| 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 |
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| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00186/29731/28293.pdf |
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| 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 |
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| 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 |
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| 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 |
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| 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 > 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 |
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| 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 (<4,000 m). This area must be regarded no more as a spreading center, but as complex boundary suffering transverse tectonics. |
| Tipo: Text |
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| Ano: 1986 |
URL: http://archimer.ifremer.fr/doc/00184/29492/27835.pdf |
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| Registros recuperados: 28 | |
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