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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... |
| Tipo: Text |
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| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00047/15865/13284.pdf |
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| Di Giuseppe, Dario; Perchiazzi, Natale; Brunelli, Daniele; Giovanardi, Tommaso; Nodari, Luca; Della Ventura, Giancarlo; Malferrari, Daniele; Maia, Marcia; Gualtieri, Alessandro F.. |
| Tremolite is one of the most common amphibole species and, in the fibrous form (i.e., characterized by crystals/particles consisting of fibres with length > 5 µm, width < 3 µm and aspect ratio > 3), one of the six asbestos minerals. Until now the attention of crystallographers has focused only on samples from continental environment. Here we report the first chemical and structural data of a tremolite asbestos found along the Mid Atlantic Ridge (MAR) at the eastern intersection of the Romanche Transform Fault (Equatorial MAR). Tremolite is associated with chlorite and lizardite and was formed through the green shale facies lower than zeolite in a predominantly fluid system. MAR tremolite asbestos shows very slight deviations from the ideal crystal... |
| Tipo: Text |
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| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00685/79703/82492.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... |
| Tipo: Text |
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| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00345/45603/49042.pdf |
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| Yu, Zhiteng; Singh, Satish C.; Gregory, Emma P. M.; Maia, Marcia; Wang, Zhikai; Brunelli, Daniele. |
| Oceanic transform faults, a key element of plate tectonics, represent the first-order discontinuities along mid-ocean ridges, host large earthquakes, and induce extreme thermal gradients in lithosphere. However, the thermal structure along transform faults and its effects on earthquake generation are poorly understood. Here we report the presence of a 10- to 15-kilometer-thick in-depth band of microseismicity in 10 to 34 kilometer depth range associated with a high-temperature (700° to 900°C) mantle below the brittle lithosphere along the Romanche mega transform fault in the equatorial Atlantic Ocean. The occurrence of the shallow 2016 moment magnitude 7.1 supershear rupture earthquake and these deep microearthquakes indicate that although large... |
| Tipo: Text |
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| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00689/80070/83089.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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| D'Acremont, Elia; Leroy, Sylvie; Maia, Marcia; Patriat, Philippe; Beslier, Marie-odile; Bellahsen, Nicolas; Fournier, Marc; Gente, Pascal. |
| Magnetic and gravity data gathered during the Encens-Sheba cruise (2000 June) in the eastern Gulf of Aden provide insights on the structural evolution of segmentation from rifted margins to incipient seafloor spreading. In this study, we document the conjugate margins asymmetry, confirm the location of the ocean-continent transition (OCT) previously proposed by seismic data, and describe its deep structure and segmentation. In the OCT, gravity models indicate highly thinned crust while magnetic data indicate presence of non-oceanic high-amplitude magnetic anomalies where syn-rift sediments are not observed. Thus, the OCT could be made of ultra-stretched continental crust intruded by magmatic bodies. However, locally in the north, the nature of the OCT... |
| Tipo: Text |
Palavras-chave: Gulf of Aden; Kinematic evolution; Ocean-continent transition; Passive continental margin; Seafloor spreading; Segmentation. |
| Ano: 2006 |
URL: https://archimer.ifremer.fr/doc/00234/34561/33314.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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