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Registros recuperados: 22
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A low delta7 Li lower crustal component: Evidence from an alkalic intraplate volcanic series (Chaine des Puys, French Massif Central) 5
Hamelin, Cedric; Seitz, Hans-michael; Barrat, Jean-alix; Dosso, Laure; Maury, Rene; Chaussidon, Marc.
The intraplate volcanic suite of the Chaine des Puys (French Massif Central) shows a complete petrologic range, from alkali basalts to trachytes. The significant variations of trace elements and radiogenic isotopes along the series strongly support the occurrence of crustal assimilation associated with fractional crystallization (AFC). The least contaminated basalts are clearly related to a HIMU-type reservoir (Pb-206/Pb-204>19.6; Sr-87/Sr-86<0.7037; epsilon(Nd)>+4). The behavior of radiogenic isotopes suggests that the most likely crustal contaminants are meta-sediments located in the lower crust. The Li isotopic compositions of the lavas range from high delta Li-7 (> + 7 parts per thousand) in basalts to lighter values in more evolved lavas...
Tipo: Text Palavras-chave: Trachytes Basalts HIMU Assimilation and fractional crystallization (AFC) Lower crust Li; Sr; Nd and Pb isotopes.
Ano: 2009 URL: http://archimer.ifremer.fr/doc/2009/publication-6853.pdf
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Age précambrien de dolérites de la dorsale réguibat (Mauritanie) 5
Dosso, Laure; Vidal, Philippe; Sichler, Bertrand; Bonifay, Alain.
Rb-Sr age determination on ten doleritic samples from the basement of Mauritania yield on average of 1 609 45 M.A. ( ?87 Rb = 1,42.10- an- ). Four among the specimens have been dated by the K-Ar method with ages of 1.750, 1.610, 832 and 1.46 x M.Y. The radiometric data are interpreted as evidence for emplacement of the dolerites at the end of the Eburnean orogeny. [NOT CONTROLLED OCR]
Tipo: Text Palavras-chave: Histoire Ifremer.
Ano: 1979 URL: http://archimer.ifremer.fr/doc/1979/publication-5251.pdf
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An isotopically distinct hydrogen reservoir in the South Pacific mantle 5
Clog, M.; Cartigny, P.; Aubaud, C.; Dosso, Laure.
Tipo: Text
Ano: 2010 URL: http://archimer.ifremer.fr/doc/00023/13409/10482.pdf
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Atypically depleted upper mantle component revealed by Hf isotopes at Lucky Strike segment 5
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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Campagne RIDELENTE: Structure de la dorsale Atlantique - Hétérogénéité du manteau et hydrothermalisme 5
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
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Chemical systematics of an intermediate spreading ridge: The Pacific-Antarctic Ridge between 56 degrees S and 66 degrees S 5
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
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Dorsale médio-océaniques : des fenêtres sur le manteau terrestre… 5
Bougault, Henri; Dosso, Laure; Joron, Jean-louis.
Ce dossier retrace une enquête chimique passionnante qui révèle comment la connaissance de l’évolution de notre planète passe par une descente dans les dorsales médio-océanique, au cœur même des laves basaltiques qui s’y créent, à la recherche d’indices infimes mais révélateurs.
Tipo: Text
Ano: 1993 URL: http://archimer.ifremer.fr/doc/00001/11242/7771.pdf
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From intracratonic extension to mature spreading in back arc basins: Examples from the Okinawa, Lau, North Fiji basins 5
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
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From intracratonic extension to nature spreading in back arc basins: Examples from the Okinawa, Lau and, North Fiji basins 5
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
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Geochemical evidence of mantle reservoir evolution during progressive rifting along the western Afar margin 5
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
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Geochemical portray of the Pacific Ridge: New isotopic data and statistical techniques 5
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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Geochemical portray of the Pacific ridge using statistical techniques 5
Hamelin, Cedric; Dosso, Laure; Moreira, Manuel; Hanan, Barry B.; Kositsky, Andrew P..
Tipo: Text
Ano: 2010 URL: http://archimer.ifremer.fr/doc/00023/13412/10488.pdf
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Helium isotopes on the Pacific-Antarctic ridge (52.5°–41.5°S) 5
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
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New structural and geochemical observations from the Pacific-Antarctic Ridge between 52°45'S and 41°15'S 5
Klingelhoefer, Frauke; Ondreas, Helene; Briais, A; Hamelin, C; Dosso, Laure.
We investigated the morphology and structure of the Pacific-Antarctic Ridge between 52 degrees 45'S and 41 degrees 15'S during the Pacantarctic2 cruise using multibeam echosounder together with gravity measurements and dredges. Analysis of the bathymetric, gravity and geochemical data reveal three ridge segments separated by overlapping spreading centers south of the Menard transform fault (MTF) and five segments north of it. Calculation of the cross-sectional area allows quantification of the variation in size of the axial bathymetric high. Together with the calculation of the mantle Bouguer anomaly, these data provide information about variations in the temperature of the underlying mantle or in crustal thickness. Areas with hotter mantle are found north...
Tipo: Text Palavras-chave: Mantle Bouguer anomaly; Temperature variations; Geochemistry; Gravity; Bathymetry; Ridge segment.
Ano: 2006 URL: http://archimer.ifremer.fr/doc/2006/publication-2108.pdf
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Origin of volcanism on the flanks of the Pacific-Antarctic ridge between 41°30'S and 52°S 5
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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Sr‐Nd‐Hf isotopes along the Pacific Antarctic Ridge from 41 to 53°S 5
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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Sulfur isotope budget (32S, 33S, 34S and 36S) in Pacific-Antarctic ridge basalts: A record of mantle source heterogeneity and hydrothermal sulfide assimilation 5
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
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Temporal evolution and geochemical variability of the South Pacific superplume activity 5
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
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Temporal magma source changes at Gaua volcano, Vanuatu island arc 5
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
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Temporal source evolution and crustal contamination at Lopevi Volcano, Vanuatu Island Arc 5
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
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