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| Maia, Marcia; Pessanha, Ivo; Courreges, Esther; Patriat, Martin; Gente, Pascal; Hemond, Christophe; Janin, Myriam; Johnson, Kevin; Roest, Walter; Royer, Jean-yves; Vatteville, Judith. |
| The Amsterdam-Saint Paul plateau results from a 10 Myr interaction between the South East Indian Ridge and the Amsterdam-Saint Paul hot spot. During this period of time, the structure of the plateau changed as a consequence of changes in both the ridge-hot spot relative distance and in the strength of the hot spot source. The joint analysis of gravity-derived crust thickness and bathymetry reveals that the plateau started to form at similar to 10 Ma by an increase of the crustal production at the ridge axis, due to the nearby hot spot. This phase, which lasted 3-4 Myr, corresponds to a period of a strong hot spot source, maybe due to a high temperature or material flux, and decreasing ridge-hot spot distance. A second phase, between similar to 6 and... |
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| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00047/15865/13284.pdf |
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| Boulart, Cedric; Briais, Anne; Chavagnac, Valerie; Revillon, Sidonie; Ceuleneer, Georges; Donval, Jean-pierre; Guyader, Vivien; Barrere, Fabienne; Ferreira, Nicolas; Hanan, Barry; Hemond, Christophe; Macleod, Sarah; Maia, Marcia; Maillard, Agnes; Merkuryev, Sergey; Park, Sung-hyun; Ruellan, Etienne; Schohn, Alexandre; Watson, Sally; Yang, Yun-seok. |
| Using a combined approach of seafloor mapping, MAPR and CTD survey, we report evidence for active hydrothermal venting along the 130°-140°E section of the poorly-known South-East Indian Ridge (SEIR) from the Australia-Antarctic Discordance (AAD) to the George V Fracture Zone (FZ). Along the latter, we report Eh and CH4 anomalies in the water column above a serpentinite massif, which unambiguously testify for ultramafic-related fluid flow. This is the first time that such circulation is observed on an intermediate-spreading ridge. The ridge axis itself is characterized by numerous off-axis volcanoes, suggesting a high magma supply. The water column survey indicates the presence of at least ten distinct hydrothermal plumes along the axis. The CH4:Mn ratios... |
| Tipo: Text |
Palavras-chave: Hydrothermal plumes; Mid-ocean ridges; South-East Indian Ridge. |
| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00387/49821/50400.pdf |
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| Maia, Marcia; Sichel, Susanna; Briais, Anne; Brunelli, Daniele; Ligi, Marco; Ferreira, Nicolas; Campos, Thomas; Mougel, Berengere; Brehme, Isa; Hemond, Christophe; Motoki, Akihisa; Moura, Denise; Scalabrin, Carla; Pessanha, Ivo; Alves, Eliane; Ayres, Arthur; Oliveira, Pedro. |
| Mantle exhumation at slow-spreading ridges is favoured by extensional tectonics through low-angle detachment faults1, 2, 3, 4, and, along transforms, by transtension due to changes in ridge/transform geometry5, 6. Less common, exhumation by compressive stresses has been proposed for the large-offset transforms of the equatorial Atlantic7, 8. Here we show, using high-resolution bathymetry, seismic and gravity data, that the northern transform fault of the St Paul system has been controlled by compressive deformation since ~10 million years ago. The long-lived transpression resulted from ridge overlap due to the propagation of the northern Mid-Atlantic Ridge segment into the transform domain, which induced the migration and segmentation of the transform... |
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| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00345/45603/49042.pdf |
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| Graham, David W.; Hanan, Barry B.; Hemond, Christophe; Blichert-toft, Janne; Albarede, Francis. |
| We report He-3/He-4 for 150 mid-ocean ridge basalt (MORB) glasses from the Southeast Indian Ridge (SEIR). Between 81 degrees E and 101 degrees E He-3/He-4 varies from 7.5 to 10.2 R-A, encompassing more than half the MORB range away from ocean island hot spots. Abrupt transitions are present and in one case the full range occurs over similar to 10 km. Melting of lithologically heterogeneous mantle containing a few percent garnet pyroxenite or eclogite leads to lower He-3/He-4, while He-3/He-4 above similar to 9 R-A likely indicates melting of pyroxenite-free or eclogite-free mantle. Patterns in the length scales of variability represent a description of helium isotopic texture. We utilize four complementary methods of spectral analysis to evaluate this... |
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| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00217/32839/31308.pdf |
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| Hekinian, Roger; Stoffers, Peter; Devey, Colin; Ackerman, Dietrich; Hemond, Christophe; O'Connor, John; Binard, Nicolas; Maia, Marcia. |
| Exploration of the Foundation Volcanic Chain (33 degrees S-131 degrees W; 37 degrees S-111 degrees W) revealed the existence of different magmatic provinces with relation to their geological settings. (1) The Pacific-Antarctic Ridge (PAR) is made up of several en echelon segments where both glassy midocean ridge basalts (MORBs) with low incompatible elements (K2O<200 ppm, Zr<120 ppm and Ce <20 ppm) as well as andesites and dacites have erupted, (2) Oblique Ridges located up to 300 lan from the PAR axis are topped with seamounts made up essentially of transitional (T) and enriched (E) MORBs with intermediate incompatible elements (K2O=0.11-0.40 %, Zr=70-140 ppm and Ce=15-30 ppm), (3) the Foundation Seamounts (FS) consisting essentially of isolated... |
| Tipo: Text |
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| Ano: 1997 |
URL: http://archimer.ifremer.fr/doc/00336/44707/44913.pdf |
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| Ponce, Alexis D.; Bertotto, Gustavo W.; Zanetti, Alberto; Brunelli, Daniele; Giovanardi, Tommaso; Aragon, Eugenio; Bernardi, Mauro I.; Hemond, Christophe; Mazzucchelli, Maurizio. |
| Cenozoic basalts carrying ultramafic mantle xenoliths occur in the Matilde, Leon and Chenque hills in the Paso de Indios region, Argentina. The mantle xenoliths from the Chenque and Leon hills mainly present porphyroclastic textures, whereas the Matilde hill xenoliths have coarse-grained to porphyroclastic textures. The equilibrium temperatures are in the range of 780 to 940 degrees C, indicating a provenance from shallow sectors of the lithospheric mantle column that were subjected to a relatively low heat flux at Cenozoic Era. According to the modal compositions of xenoliths, the mantle beneath Matilde and Leon hills was affected by greater than 22% partial melting, while less depleted peridotites occur in the Chenque suite (starting from 10% partial... |
| Tipo: Text |
Palavras-chave: Mantle xenoliths; Alkaline basalts; Paso de Indios; Patagonia. |
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00639/75150/75503.pdf |
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| Revillon, Sidonie; Jouet, Gwenael; Bayon, Germain; Rabineau, Marina; Dennielou, Bernard; Hemond, Christophe; Berne, Serge. |
| In this study, we undertook a reconnaissance study of sediments provenance in the Gulf of Lions focusing over the last 16 ka. We used geochemical and isotopic tracers to determine the source of sediments and give insight into the weathering conditions prevailing. Sediments samples were selected both onshore and offshore from the western, eastern, and central part of the Gulf of Lions. We analyzed bulk sediments, coarse and fine silt, and clay fractions. Elemental and Nd isotope compositions appeared to differ from one grain size fraction to another one. These are interpreted in terms of zircon addition in the coarse silt fraction for the elemental concentrations and variable sources influences for the Nd isotope compositions. Our results indicate that... |
| Tipo: Text |
Palavras-chave: Geochemistry; Provenance; Sediment; Weathering. |
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00043/15376/12734.pdf |
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