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| Hekinian, Roger; Bideau, Daniel; Francheteau, Jean; Cheminee, Jean-louis; Armijo, Rolando; Lonsdale, Peter; Blum, Norbert. |
| The Hess Deep, a rifted oval-shaped depression located east of the Galapagos Triple Junction at the tip of the Cocos-Nazca ridge (about 101-degrees-W, 2-degrees-N), was explored in 1988 during 21 submersible dives. A total of 11 dives were devoted to the exploration of the E-W trending Intrarift ridge (15 km in length, 3000-5400 m in depth) north of the Hess Deep depression. The Intrarift ridge represents, an outcrop of recent (1 m.y.) crustal and subcrustal material created at the axis of the East Pacific Rise (EPR), and emplaced during the lithospheric extention responsible for the westward propagation of the Cocos-Nazca rift (Francheteau et al., 1990). The lithospheric block has undergone cataclastic deformation and was dislocated by tectonic activity... |
| Tipo: Text |
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| Ano: 1993 |
URL: http://archimer.ifremer.fr/doc/00193/30391/29225.pdf |
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| Auzende, Jean-marie; Ballu, Valerie; Batiza, R; Bideau, Daniel; Cormier, Mh; Fouquet, Yves; Geistdoerfer, Patrick; Lagabrielle, Yves; Sinton, J; Spadea, P. |
| The submersible-study of four segments of the East Pacific Rise between 17 degrees and 18 degrees 40'S, where the spreading rate is greater than 150 mm/a, allows us to confirm the variability of the accretion processes. The segment between 17 degrees and 17 degrees 30'S shows an intense present-day magmatic activity. The one between 18 degrees 10' and 18 degrees 22'S shows a mainly tectonic activity. The segment between 18 degrees 22' and 18 degrees 37'S is an intermediate stage with an axial graben in which fresh lavas were emplaced by an extremely young eruption. On all the segments the hydrothermal activity exists ranging from shimmering water up to black smokers, It is associated with different stages of animal colonization. |
| Tipo: Text |
Palavras-chave: Océan Pacifique; Dorsale ultra-rapide; Magmatisme; Tectonique; Hydrothermalisme.; PACIFIC OCEAN; ULTRA-FAST SPREADING RIDGE; MAGMATISM; TECTONICS; HYDROTHERMALISM. |
| Ano: 1994 |
URL: http://archimer.ifremer.fr/doc/00183/29458/27840.pdf |
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| Geistdoerfer, P; Auzende, Jean-marie; Batiza, R; Bideau, Daniel; Cormier, Mh; Fouquet, Yves; Lagabrielle, Yves; Sinton, J; Spadea, P. |
| 70 hydrothermal sites were observed during the 23 dives of the French submersible Nautile (''Naudur'' cruise, December 1993), at 17-degrees-19-degrees-S on the East Pacific Rise. Large vent-animal communities are present around these sites. The zoological composition of these communities is the same as that of the communities at 11-degrees-13-degrees-N and 21-degrees-N on the East Pacific Rise. However, the distribution of the species on the sites is different from all the other hydrothermal communities; large anemone fields of several hundred square metres, associated with colonies of Bathymodiolus and Calyptogena, have been observed. Fresh lava areas seem to bear the most important biological activity. |
| Tipo: Text |
Palavras-chave: Hydrothermalisme; Dorsale Est Pacifique; Communautés animales.; HYDROTHERMAL VENTS; EAST PACIFIC RISE; ANIMAL COMMUNITIES. |
| Ano: 1995 |
URL: http://archimer.ifremer.fr/doc/00183/29454/27856.pdf |
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| Fouquet, Yves; Auzende, Jean-marie; Ballu, V; Batiza, R; Bideau, Daniel; Cormier, Mh; Geistdoerfer, P; Lagabrielle, Yves; Sinton, J; Spadea, P. |
| 69 new hydrothermal sites were discovered during the Naudur diving cruise. Dives were conducted between 17 degrees 5 and 18 degrees 40'5 on four segments showing marked contrast in morphology, volcanic, tectonic and hydrothermal activity. At 17 degrees 10'5, 17 degrees 25'5 and 18 degrees 37'5 the ridge has a dome shaped cross-section and is dominated by very active volcanic activity. Early widespread low temperature (<50 degrees C) diffuse hydrothermal discharge is followed by focused high temperature black smokers. At 18 degrees 15'S tectonic activity is dominant, no recent lava was observed, and only two of the 20 hydrothermal sites are active. At 18 degrees 32'5 recent lava representing a new volcanic episode partly covers the bottom of the graben.... |
| Tipo: Text |
Palavras-chave: Hydrothermalisme; Océan; Dorsales rapides; Min6ralisations sulfurées.; HYDROTHERMAL ACTIVITY; OCEAN; FAST SPREADING RIDGES; SULFIDES. |
| Ano: 1994 |
URL: http://archimer.ifremer.fr/doc/00183/29455/27889.pdf |
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| Bideau, Daniel; Hekinian, Roger. |
| Small-scale distribution of basaltic compositions along the mid-ocean ridge crests suggests that the magmatic processes are sensitive to spatial and temporal fluctuations related to proximity of ridge hot spots, changes in spreading rate, thermal boundary effects associated with ridge offsets, off-axis volcanoes and ridge propagators, and variations in magma supply through time. A detailed sampling of the East Pacific Rise (EPR) axis, near 13 degrees N, revealed that complex basalt compositional variations unrelated to morphology and structure occur both on the ridge axis and on nearby off-axis seamounts. This small-scale heterogeneity is attributed to successive magmatic cycles separated by periods of quiescence (amagmatic phases) where each cycle... |
| Tipo: Text |
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| Ano: 1995 |
URL: http://archimer.ifremer.fr/doc/00258/36974/35516.pdf |
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| Bideau, Daniel. |
| Lorsque les roches de la croûte océanique se sont mises en place dans la zone axiale des dorsales, elles ont acquis une aimantation dans la direction du champ magnétique terrestre. Ce champ a subi des inversions temporaires pendant certaines périodes géologiques. Par conséquent, la connaissance de la polarité magnétique des roches est un argument clé dans le développement de la théorie de l'expansion océanique. |
| Tipo: Text |
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| Ano: 1980 |
URL: http://archimer.ifremer.fr/doc/00034/14534/11820.pdf |
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| Hekinian, Roger; Bideau, Daniel; Hebert, Réjean; Niu, Yaoling. |
| The Garrett transform is characterized by recent (zero age) volcanic activity located within the active tectonic domain of the transform valley at depths greater than the 3500 m. This intratransform volcanic activity contributed to the formation of constructional edifices forming ridges (>300 m in height) and small mounds (<20 m in height) built near slivers of serpentinized peridotites. The erupted lavas are depleted mid ocean ridge basalts (MORBs) with low ratios of K/Ti (0.02-0.11), Zr (30-100 ppm), Y (18-50 ppm), and (La/Sm)(N) (0.25-0.60). Their more depleted nature and smaller range of variability for the compatible elements (Ni=70-180 ppm, Mg#=0.58-0.71, where Mg# is the magnesium number (=Mg+2/Mg+2+Fe+2)) are the main points of difference... |
| Tipo: Text |
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| Ano: 1995 |
URL: http://archimer.ifremer.fr/doc/00259/36975/35515.pdf |
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