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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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| Hamelin, Cedric; Dosso, Laure; Hanan, Barry B.; Moreira, Manuel; Kositsky, Andrew P.; Thomas, Marion Y.. |
| Samples collected during the PACANTARCTIC 2 cruise fill a sampling gap from 53 degrees to 41 degrees S along the Pacific Antarctic Ridge (PAR). Analysis of Sr, Nd, Pb, Hf, and He isotope compositions of these new samples is shown together with published data from 66 degrees S to 53 degrees S and from the EPR. The recent advance in analytical mass spectrometry techniques generates a spectacular increase in the number of multidimensional isotopic data for oceanic basalts. Working with such multidimensional datasets generates a new approach for the data interpretation, preferably based on statistical analysis techniques. Principal Component Analysis (PCA) is a powerful mathematical tool to study this type of datasets. The purpose of PCA is to reduce the... |
| Tipo: Text |
Palavras-chave: Oceanic basalts; Pacific-Antarctic Ridge; Mantle heterogeneity; Principal Component Analysis; Sr Nd Pb Hf isotopes. |
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00031/14197/11508.pdf |
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| Escartin, Javier; Leclerc, Frederique; Olive, Jean-arthur; Mevel, Catherine; Cannat, Mathilde; Petersen, Sven; Augustin, Nico; Feuillet, Nathalie; Deplus, Christine; Bezos, Antoine; Bonnemains, Diane; Chavagnac, Valerie; Choi, Yujin; Godard, Marguerite; Haaga, Kristian A.; Hamelin, Cedric; Ildefonse, Benoit; Jamieson, John W.; John, Barbara E.; Leleu, Thomas; Macleod, Christopher J.; Massot-campos, Miguel; Nomikou, Paraskevi; Paquet, Marine; Rommevaux-jestin, Celine; Rothenbeck, Marcel; Steinfuehrer, Anja; Tominaga, Masako; Triebe, Lars; Campos, Ricard; Gracias, Nuno; Garcia, Rafael; Andreani, Muriel; Vilaseca, Geraud. |
| Properly assessing the extent and magnitude of fault ruptures associated with large earthquakes is critical for understanding fault behavior and associated hazard. Submarine faults can trigger tsunamis, whose characteristics are defined by the geometry of seafloor displacement, studied primarily through indirect observations (e.g., seismic event parameters, seismic profiles, shipboard bathymetry, coring) rather than direct ones. Using deep-sea vehicles, we identify for the first time a marker of coseismic slip on a submarine fault plane along the Roseau Fault (Lesser Antilles), and measure its vertical displacement of ∼0.9 m in situ. We also map recent fissuring and faulting of sediments on the hangingwall, along ∼3 km of rupture in close proximity to the... |
| Tipo: Text |
Palavras-chave: Submarine fault; Surface rupture; Earthquake; Fault slip; Neotectonics; Microbathymetry. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00344/45500/45051.pdf |
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| 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 |
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| Hamelin, Cedric; Bezos, Antoine; Dosso, Laure; Escartin, Javier; Cannat, Mathilde; Mevel, Catherine. |
| The Earth's upper mantle is commonly depicted as a “marble cake” assemblage of a refractory component mingled with varying amounts of geochemically diverse enriched components. This depleted component controls the major element composition of Mid-Oceanic Ridge Basalts (MORBs). It has long been considered a fairly uniform reservoir, depleted by early melting and well homogenized by subsequent convective stirring. We present new Hf, Nd, Pb and Sr isotopes and trace element data for basalts from the center of the Lucky Strike segment of the Mid-Atlantic Ridge (MAR). Despite the limited size of our sampling area (1.6 km along-axis by 5 km across), these data show a large range of isotopic compositions (similar to that of the whole MAR). It has recently been... |
| Tipo: Text |
Palavras-chave: Oceanic basalts; Mid-Atlantic Ridge; Lucky Strike; Mantle heterogeneity; Hf isotopes. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00129/24047/23572.pdf |
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