|
|
|
| Registros recuperados: 22 | |
|
| |
|
| |
|
| |
|
|
| 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 |
| |
|
|
| Bougault, Henri; Appriou, P; Bienvenu, P; Cambon, Pierre; Charlou, Jean-luc; Collette, B; Donval, Jean-pierre; Dosso, Laure; Floch, G; Fouquet, Yves. |
| Tipo: Text |
|
| Ano: 1990 |
URL: http://archimer.ifremer.fr/doc/00070/18105/15653.pdf |
| |
|
|
| Vlastelic, Ivan; Dosso, Laure; Bougault, Henri; Aslanian, Daniel; Geli, Louis; Etoubleau, Joel; Bohn, Marcel; Joron, Jl; Bollinger, C. |
| Axial bathymetry, major/trace elements, and isotopes suggest:that the Pacific-Antarctic Ridge (PAR) between 56 degrees S and 66 degrees S is devoid of any hotspot influence. PAR (56-66 degrees 5) samples have in-average lower Sr-87/Sr-86 and Nd-143/Nd-144 and higher Pb-206/(204)pb than northern Pacific midocean ridge basalts (MORB), and also than MORE from the other oceans. The high variability of Pb isotopic ratios (compared to Sr and Nd) can be due to either a;general high mu (HIMU) (high U/Pb) affinity of the southern Pacific upper mantle or to a mantle event first recorded in time by Pb isotopes. Compiling the results of this study with those from the PAR between 53 degrees S and 57 degrees S gives a continuous view of mantle characteristics from south... |
| Tipo: Text |
|
| Ano: 2000 |
URL: https://archimer.ifremer.fr/doc/00000/10578/9396.pdf |
| |
|
| |
|
|
| Auzende, Jean-marie; Boespflug, Xavier; Bougault, Henri; Dosso, Laure; Foucher, Jean-paul; Joron, Jean-louis; Ruellan, Etienne; Sibuet, Jean-claude. |
| Three cruises (POP 1, SEAPSO 3 and SEAPSO 4) carried out during the "Tour du Monde" of the R.V. Jean Charcot allow us to obtain new structural and geochemical data for the Okinawa, North Fiji and Lau basins. Taken together, the structural and geochemical data illustrate a difference in evolution stages of these sites. The less evolved stage is represented by the Okinawa basin, where accretion is evidenced only by volcanic intrusion into a thinned continental crust. The most evolved stage is illustrated in the North Fiji basin, where the present-day accretion can be directly compm·ed to the East Pacific Ridge. The Lau basin displays an intem1ediate stage with a complex system of accretionary ridges. This difference in the evolution stage is translated in... |
| Tipo: Text |
Palavras-chave: Ouest Pacifique; Bassins arriere arc; Structure; Accretion; Geochimie; West Pacific; Back arc basins; Structure; Accretion; Geochemistry. |
| Ano: 1990 |
URL: http://archimer.ifremer.fr/doc/00119/23058/20893.pdf |
| |
|
|
| Auzende, Jean Marie; Boespflug, X; Bougault, Henri; Dosso, Laure; Foucher, Jean-paul; Joron, J-l; Ruellan, Etienne; Sibuet, Jean-claude. |
| Three cruises (POP 1, SEAPSO 3 and SEAPSO 4) carried out during the "Tour du Monde" of the R.V. Jean Charcot allow us to obtain new structural and geochemical data for the Okinawa, North Fiji and Lau basins. Taken together, the structural and geochemical data illustrate a difference in evolution stages of these sites. The less evolved stage is represented by the Okinawa basin, where accretion is evidence only by volcanic intrusion into a thinned continental crust. The most evolved stage is illustrated in the North Fiji basin, where the present-day accretion can be directly compared to the East Pacific Ridge. The Lau basin displays an intermediate stage with a complex system of accretionary ridges. This difference in the evolution stage is translated in the... |
| Tipo: Text |
|
| Ano: 1990 |
URL: http://archimer.ifremer.fr/doc/00268/37893/35974.pdf |
| |
|
|
| Rooney, Tyrone O.; Mohr, Paul; Dosso, Laure; Hall, Chris. |
| The Afar triple junction, where the Red Sea, Gulf of Aden and African Rift System extension zones converge, is a pivotal domain for the study of continental-to-oceanic rift evolution. The western margin of Afar forms the southernmost sector of the western margin of the Red Sea rift where that margin enters the Ethiopian flood basalt province. Tectonism and volcanism at the triple junction had commenced by similar to 31 Ma with crustal fissuring, diking and voluminous eruption of the Ethiopian-Yemen flood basalt pile. The dikes which fed the Oligocene-Quaternary lava sequence covering the western Afar rift margin provide an opportunity to probe the geochemical reservoirs associated with the evolution of a still active continental margin. Ar-40/Ar-39... |
| Tipo: Text |
|
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00118/22884/20944.pdf |
| |
|
|
| 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 |
| |
|
| |
|
|
| 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 |
| |
|
| |
|
|
| 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 |
| |
|
|
| 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 |
| |
|
|
| Labidi, J.; Cartigny, P.; Hamelin, C.; Moreira, M.; Dosso, Laure. |
| To better address how Mid-Ocean Ridge Basalt (MORB) sulfur isotope composition can be modified by assimilation and/or by immiscible sulfide fractionation, we report sulfur (S), chlorine (Cl) and copper (Cu) abundances together with multiple sulfur isotope composition for 38 fresh basaltic glasses collected on the Pacific-Antarctic ridge. All the studied glasses -with the exception of 8 off-axis samples- exhibit relatively high Cl/K, as the result of pervasive Cl-rich fluid assimilation. This sample set hence offers an opportunity to document both the upper mantle S isotope composition and the effect of hydrothermal fluids assimilation on the S isotope composition of erupted basalts along segments that are devoid of plume influence. Δ33S and Δ36S yield... |
| Tipo: Text |
|
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00179/29013/27441.pdf |
| |
|
|
| Bonneville, Alain; Dosso, Laure; Hildenbrand, Anthony. |
| We are presenting a new set of K/Ar ages and geochemical analyses obtained on deep-sea samples dredged in 1999 on several seamounts of the Cook-Austral volcanic chains in the Pacific Ocean. The new geochemical results, together with published data on island samples, allow us to reveal a time evolution of the mantle source composition as well as an increase in geochemical variability of the superplume responsible for the regional South Pacific Superswell. Three identified volcanic stages of 58-40, 33-20 and 20-0 Ma are identified with signatures of mantle reservoir composition varying from close to C to N-MORB-types and C/HFMU-type, respectively. Using a geodynamic reconstruction for the most recent volcanic period, from 20 Ma to present, three hotspot... |
| Tipo: Text |
Palavras-chave: Hotspot; Cook Austral; Seamount ages; Geochemical sources; South Pacific Superswell; Mantle plume. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/publication-1559.pdf |
| |
|
|
| Beaumais, Aurelien; Bertrand, Herve; Chazot, Gilles; Dosso, Laure; Robin, Claude. |
| Gaua Island (also called Santa Maria), from the central part of the Vanuatu arc, consists of a large volcano marked by a caldera that hosts the active Mount Garet summit cone. In this paper, a geochemical study including Sr, Nd, Pb and Hf isotopic compositions of 25 lavas emitted since 1.8 Ma is presented, with a focus on the volcanic products that preceded (old volcanics, main cone and pyroclastic series) and followed (Mount Garet) the caldera forming event. All lavas show an island arc signature with enrichment in LILE and depletion in HFSE. Post-caldera lavas define a medium-K calc-alkaline trend, whereas lavas from the former main cone have high-K calc-alkaline compositions. Compared to the pre-caldera volcanic suite, the Mount Garet lavas have... |
| Tipo: Text |
Palavras-chave: Gaua; Vanuatu; Geochemistry; Isotopes; Subduction; Mantle source. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00319/43052/42557.pdf |
| |
|
|
| Beaumais, Aurelien; Chazot, Gilles; Dosso, Laure; Bertrand, Herve. |
| Here we present a new geochemical study of Lopevi volcano, one the most active volcanoes in the Vanuatu island arc. We focus on the temporally well-defined sequence of lava flows emitted since 1960, and for the first time, on pre-1960 volcanic products, including high-MgO basalts and felsic andesites, the most evolved lavas sampled so far on this island. This work reports the first Pb and Hf isotopic study of lavas from Lopevi island. These lavas display correlations between differentiation indexes such as SiO2 content and isotopic ratios. The felsic andesites extend the known correlations with both the least (Sr-Pb) and the most (Nd-Hf) radiogenic isotopic compositions on the island. Our results confirm that the rising magma interacted with the sub-arc... |
| Tipo: Text |
Palavras-chave: Lopevi; Vanuatu; Geochemistry; Isotopes; Subduction; Mantle source. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00167/27801/26223.pdf |
| |
| Registros recuperados: 22 | |
|
|
|
