Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Polygonal faulting is a widespread phenomenon in sedimentary basins worldwide. It changes basin-scale fluid flow patterns and alters the physical properties of the sediments making it important for hydrocarbon exploration and geohazard analysis. It is generally accepted that polygonal fault patterns derive from dewatering and compaction of the host sediments, but there is debate regarding the processes that control polygonal faulting. New multibeam-bathymetry data from the Hatton Basin, NE Atlantic, show up to 10 m deep and 200-600 m wide troughs at the seabed. They connect to each other forming polygons that are several hundred metres across, i.e. of similar size as buried polygonal fault systems observed in 3D seismic data. The troughs are symmetrical and resemble elongated pockmarks. Previously unpublished high-resolution 2D seismic data from the same area show seismic disturbance zones similar to pipes observed under pockmarks elsewhere as well as faults that have all the characteristics of polygonal fault systems. The observation of the wide disturbance zones is enigmatic, as they appear to follow the polygonal seafloor pattern. The observed extent of the polygonal sediment contraction system is substantial covering almost 37,000 km2. We calculate that some 2600 km3 of possibly carbon-bearing fluids have been expelled from this system and we expect that this will affect the benthic ecosystems, although so far there is only limited evidence for chemosynthetic habitats.
ISSN: 0025-3227

hal-00772468
https://hal.archives-ouvertes.fr/hal-00772468
DOI : 10.1016/j.margeo.2012.09.013

Éditeur(s) : HAL CCSD IGI Global
Résumé : International audience
Standard data mining techniques have been applied and adapted for eliciting knowledge from social networks, by achieving classical tasks such as classification, search for frequent patterns or link prediction. Most works have exploited only the network topological structure, and therefore cannot be used to answer questions involving nodes features. For instance, the frequent pattern discovery task generally refers to the search for sub-networks frequently found in a single network or in a set of networks. In the same area, this paper focuses on the concept of frequent link that stands as a regularity found in a network on links between node groups that share common characteristics. The extraction of such links from a social network is a particularly challenging and computationally intensive problem, since it is much dependent on the number of links and attributes. In this study, we propose a solution for reducing the search space of frequent links, by filtering the nodes features on a criterion of frequency. We make the assumption that frequent links occur between sets of features that are themselves frequent. This property is used to reduce the search space and speed up the extraction process. We empirically show that it is well founded. We discuss the efficiency of the solution in terms of computation time and number of frequent patterns found depending on several frequency thresholds.
ISSN: 1947-8186

hal-00786166
https://hal.archives-ouvertes.fr/hal-00786166

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
The variation of elastic- wave velocities as a function of the direction of propagation through the Earth's interior is a widely documented phenomenon called seismic anisotropy. The geometry and amount of seismic anisotropy is generally estimated by measuring shearwave splitting, which consists of determining the polarization direction of the fast shear- wave component and the time delay between the fast and slow, orthogonally polarized, waves. In subduction zones, the teleseismic fast shear- wave component is oriented generally parallel to the strike of the trench(1), although a few exceptions have been reported (Cascadia(2) and restricted areas of South America(3,4)). The interpretation of shear- wave splitting above subduction zones has been controversial and none of the inferred models seems to be sufficiently complete to explain the entire range of anisotropic patterns registered worldwide(1). Here we show that the amount and the geometry of seismic anisotropies measured in the forearc regions of subduction zones strongly depend on the preferred orientation of hydrated faults in the subducting oceanic plate. The anisotropy originates from the crystallographic preferred orientation of highly anisotropic hydrous minerals (serpentine and talc) formed along steeply dipping faults and from the larger- scale vertical layering consisting of dry and hydrated crust - mantle sections whose spacing is several times smaller than teleseismic wavelengths. Fault orientations and estimated delay times are consistent with the observed shear- wave splitting patterns in most subduction zones.
ISSN: 0028-0836

hal-00412016
https://hal.archives-ouvertes.fr/hal-00412016
DOI : 10.1038/nature07376

Éditeur(s) : HAL CCSD
Résumé : International audience
The extraction of knowledge from social networks is an area that has experienced significant growth in recent years. Indeed, thanks to the improvement of storage and calculation capacities, and the heterogeneity of data that can currently be extracted, much effort has been made to go beyond traditional knowledge, by proposing new kinds of patterns that take into account the context. However, while many works were interested in designing new patterns of knowledge or in optimizing existing approaches, few studies have been focused in merging patterns and on the useful knowledge emerging from such fusions. In this work, we focus on two network clustering approaches, able to extract two distinct kinds of patterns, and we seek to understand both the intersections that can exist between them and the knowledge that emerges from their fusion. The first is the classical nodes clustering approach that consists in searching for communities into a network. The second is the search for frequent conceptual links, a new link clustering approach that aims identifying frequent links between groups of nodes sharing common attributes. We propose a set of original measures that aim to evaluate the amount of shared information between these patterns when they are extracted from a same network. These measures are applied to three datasets and demonstrate the interest in simultaneously considering several sources of knowledge.
Advances in Knowledge Discovery and Management (AKDM)

hal-01514227
https://hal.archives-ouvertes.fr/hal-01514227
DOI : 10.1007/978-3-319-45763-5_13

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Constraining mantle deformation beneath plate boundaries where plates interact with each other, such as beneath active or halted mountain belts, is a particularly important objective of "mantle tectonics" that may bring a depth extent to the Earth's surface observation. Such mantle deformation can be mapped at scale lengths of several tens of kilometers through the analysis of seismological data and particularly by mapping seismic anisotropy from the splitting analysis of vertically-propagating SKS waves that largely reflect the strain-induced crystal preferred orientations of the rock-forming minerals within the upper mantle. In the present study, we analyse data from approximately 50 broadband seismic stations covering the Western Alps and we provide a coherent picture of upper mantle anisotropy beneath the belt. The large-scale anisotropy pattern is characterized by fast split directions that closely follow the trend of the belt. Moreover, the maximum anisotropy magnitude is not located beneath the internal zones of the belt but instead beneath external units. All suggests that the anisotropy is likely dominated by sublithospheric mantle deformation. We propose that the observed anisotropy pattern can be explained by recent or active mantle flow around the Eurasian slab presently plunging beneath the inner parts of the Alps.
ISSN: 0012-821X

hal-00617828
https://hal.archives-ouvertes.fr/hal-00617828
https://hal.archives-ouvertes.fr/hal-00617828/document
https://hal.archives-ouvertes.fr/hal-00617828/file/Barruol_SKS_Alpes_EPSL2011_hal.pdf
DOI : 10.1016/j.epsl.2010.12.040

Éditeur(s) : HAL CCSD
Résumé : International audience
Occupational exposure constitutes a common risk factor for lung cancer. We observed molecular alterations in 73% of never-smokers, 35% of men and 8% of women were exposed to at least one occupational carcinogen. We report herein associations between molecular patterns and occupational exposure.BioCAST was a cohort study of lung cancer in never-smokers that reported risk factor exposure and molecular patterns. Occupational exposure was assessed via a validated 71-item questionnaire. Patients were categorised into groups that were unexposed and exposed to polycyclic aromatic hydrocarbons (PAH), asbestos, silica, diesel exhaust fumes (DEF), chrome and paints. Test results were recorded for EGFR, KRAS, HER2, BRAF and PIK3 mutations, and ALK alterations.Overall, 313 out of 384 patients included in BioCAST were analysed. Asbestos-exposed patients displayed a significantly lower rate of EGFR mutations (20% versus 44%, p=0.033), and a higher rate of HER2 mutations (18% versus 4%, p=0.084). ALK alterations were not associated with any occupational carcinogens. The DEF-exposed patients were diagnosed with a BRAF mutation in 25% of all cases. Chrome-exposed patients exhibited enhanced HER2 and PIK3 mutation frequency.Given its minimal effects in the subgroups, we conclude that occupational exposure slightly affects the molecular pattern of lung cancers in never-smokers. In particular, asbestos-exposed patients have a lower chance of EGFR mutations.
European Respiratory Journal

hal-01647080
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01647080
DOI : 10.1183/13993003.00716-2017
PUBMED : 29074543

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
This article documents several cases of widespread species, which usually mimic other widespread species throughout the Indo–Pacific, using endemic Marquesan species as a model and displaying endemic mimicry patterns. This discovery adds a new line of evidence to the uniqueness of the Marquesas Islands, which not only host a high number of endemic reef–fish species, but also endemic mimicry patterns.
ISSN: 0022-1112

hal-01338324
http://hal.upmc.fr/hal-01338324
http://hal.upmc.fr/hal-01338324/document
http://hal.upmc.fr/hal-01338324/file/2016_Delrieu%E2%80%90Trottin%20et%20al_When%20endemic.pdf
DOI : 10.1111/jfb.13050

Éditeur(s) : HAL CCSD American Geophysical Union (AGU)
Résumé : International audience
The lateral variation of the mechanical properties of continental lithosphere is an important factor controlling the localization of deformation and thus the deformation history and geometry of intraplate mountain belts. A series of three-layer lithospheric-scale analog models, with a strong domain (SD) embedded at various depths, are presented to investigate the development of topography and deformation patterns by having lateral heterogeneities within a weak continental lithosphere. The experiments, performed at a constant velocity and under normal gravity, indicate that the presence or absence of the SD controls whether deformation is localized or distributed at a lithospheric scale. Deformation and topography localize above the edges of the SD, while the SD region itself is characterized by minor amounts of surficial deformation and topography. The depth of the SD (within the ductile crust, ductile mantle lithosphere, or both) controls the pattern of deformation and thus the topography. The presence of a SD in the ductile crust or in the mantle results in limited surficial topographic effects but large variations in the Moho topography. Strong Moho deflection occurs when the SD is in the ductile crust, while the Moho remains almost flat when the SD is in the mantle. When the SD occupies the ductile lithosphere, the SD is tilted. These analog experiments provide insights into intraplate strain localization and could in particular explain the topography around the Tarim Basin, a lithospheric-scale heterogeneity north of the India-Asia collision zone.
ISSN: 0278-7407

hal-01172472
https://hal.archives-ouvertes.fr/hal-01172472
DOI : 10.1002/2014TC003756

Éditeur(s) : Springer
Résumé : We present the global general circulation model IPSL-CM5 developed to study the long-term response of the climate system to natural and anthropogenic forcings as part of the 5th Phase of the Coupled Model Intercomparison Project (CMIP5). This model includes an interactive carbon cycle, a representation of tropospheric and stratospheric chemistry, and a comprehensive representation of aerosols. As it represents the principal dynamical, physical, and bio-geochemical processes relevant to the climate system, it may be referred to as an Earth System Model. However, the IPSL-CM5 model may be used in a multitude of configurations associated with different boundary conditions and with a range of complexities in terms of processes and interactions. This paper presents an overview of the different model components and explains how they were coupled and used to simulate historical climate changes over the past 150 years and different scenarios of future climate change. A single version of the IPSL-CM5 model (IPSL-CM5A-LR) was used to provide climate projections associated with different socio-economic scenarios, including the different Representative Concentration Pathways considered by CMIP5 and several scenarios from the Special Report on Emission Scenarios considered by CMIP3. Results suggest that the magnitude of global warming projections primarily depends on the socio-economic scenario considered, that there is potential for an aggressive mitigation policy to limit global warming to about two degrees, and that the behavior of some components of the climate system such as the Arctic sea ice and the Atlantic Meridional Overturning Circulation may change drastically by the end of the twenty-first century in the case of a no climate policy scenario. Although the magnitude of regional temperature and precipitation changes depends fairly linearly on the magnitude of the projected global warming (and thus on the scenario considered), the geographical pattern of these changes is strikingly similar for the different scenarios. The representation of atmospheric physical processes in the model is shown to strongly influence the simulated climate variability and both the magnitude and pattern of the projected climate changes.
Climate Dynamics (0930-7575) (Springer), 2013-05 , Vol. 40 , N. 9-10 , P. 2123-2165

Droits : The Author(s) 2013. This article is published with open access at Springerlink.com
http://archimer.ifremer.fr/doc/00138/24966/23079.pdf
DOI:10.1007/s00382-012-1636-1
http://archimer.ifremer.fr/doc/00138/24966/

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : This study explores weather perceptions, evaluations and behavior of holiday-tourists to the French Caribbean island of La Martinique. Herein, the importance of selected weather parameters for a ‘typical’ summer holiday, for the choice that was made in coming to Martinique and for planned activities is examined. 32 snapshot interviews were held in two brief time periods within a month. Results illustrated slight differences in climate preferences for respondents depending whether they come from a cold or from a warm climate country, that activity patterns seemed overall little influenced by changing weather conditions and that the experienced weather, which was marked by heavy rains in the first data collection period and by changeable weather in the second, appeared to take only a limited impact on return intentions. Albeit the limited possibility of a pilot study to produce valid and reliable findings, variables and factors which are critical to consider when examining weather perceptions and behaviors have been pointed out and presented in a conceptual model for further research.
Cette étude explore les perceptions et les évaluations des conditions météorologiques et les comportements des vacanciers sur l'île de la Martinique. A ce sujet, l´étude examine l'influence de certains paramètres météorologiques sélectionnés sur des vacances d'été «typiques», sur le choix de la destination Martinique et sur les activités envisagées sur lieu. 32 interviews instantanées ont eu lieu en deux courtes périodes de temps pendant un mois. Les résultats illustraient qu´il y avait de légères différences concernant les préférences climatiques selon que les répondants venaient d'un pays au climat froid ou chaud, que les schémas d'activité semblaient généralement peu influencés par les changements météorologiques et que le temps - marquées par de fortes pluies dans la première période de la collecte de données et par un temps variable dans la seconde période - semblait n´avoir qu´un impact limité sur les intentions à revenir à la Martinique. Bien que l´étude pilote n´ait que des possibilités limitées de fournir des résultats valides et fiables, elle identifie les variables et les facteurs qui sont essentiels à considérer lors d´un projet de recherche qui examine la perception des conditions météorologiques par les touristes et les comportements qui en résultent. Ces facteurs sont présentés dans un modèle conceptuel.
Martinique

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.5323
http://journals.openedition.org/etudescaribeennes/5323

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Tropical cyclone (TC) waves can severely damage coral reefs. Models that predict where to find such damage (the 'damage zone') enable reef managers to: 1) target management responses after major TCs in near-real time to promote recovery at severely damaged sites; and 2) identify spatial patterns in historic TC exposure to explain habitat condition trajectories. For damage models to meet these needs, they must be valid for TCs of varying intensity, circulation size and duration. Here, we map damage zones for 46 TCs that crossed Australia's Great Barrier Reef from 1985–2015 using three models – including one we develop which extends the capability of the others. We ground truth model performance with field data of wave damage from seven TCs of varying characteristics. The model we develop (4MW) out-performed the other models at capturing all incidences of known damage. The next best performing model (AHF) both under-predicted and over-predicted damage for TCs of various types. 4MW and AHF produce strikingly different spatial and temporal patterns of damage potential when used to reconstruct past TCs from 1985–2015. The 4MW model greatly enhances both of the main capabilities TC damage models provide to managers, and is useful wherever TCs and coral reefs co-occur.
ISSN: 2045-2322

Droits : http://creativecommons.org/licenses/by/
hal-01330362
https://hal-univ-perp.archives-ouvertes.fr/hal-01330362
https://hal-univ-perp.archives-ouvertes.fr/hal-01330362/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01330362/file/srep26009.pdf
DOI : 10.1038/srep26009

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
Little is known of how linkage patterns between species change along environmental gradients. The small, spatially discrete food webs inhabiting tank-bromeliads provide an excellent opportunity to analyse patterns of community diversity and food-web topology (connectance, linkage density, nestedness) in relation to key environmental variables (habitat size, detrital resource, incident radiation) and predators: prey ratios. We sampled 365 bromeliads in a wide range of understorey environments in French Guiana and used gut contents of invertebrates to draw the corresponding 365 connectance webs. At the bromeliad scale, habitat size (water volume) determined the number of species that constitute food-web nodes, the proportion of predators, and food-web topology. The number of species as well as the proportion of predators within bromeliads declined from open to forested habitats, where the volume of water collected by bromeliads was generally lower because of rainfall interception by the canopy. A core group of microorganisms and generalist detritivores remained relatively constant across environments. This suggests that (i) a highly-connected core ensures food-web stability and key ecosystem functions across environments, and (ii) larger deviations in food-web structures can be expected following disturbance if detritivores share traits that determine responses to environmental changes. While linkage density and nestedness were lower in bromeliads in the forest than in open areas, experiments are needed to confirm a trend for lower food-web stability in the understorey of primary forests.
PLoS ONE

hal-00913931
https://hal.archives-ouvertes.fr/hal-00913931
https://hal.archives-ouvertes.fr/hal-00913931/document
DOI : 10.1371/journal.pone.0071735
OATAO : 10204

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : Cette étude s’attache à rendre compte des difficultés auxquelles l’île de La Réunion est confrontée de longue date et qui ne trouvent, jusqu’à présent, aucune issue satisfaisante en termes de développement. De crises en conflits, récurrents dans leurs formes comme dans leurs schémas spatiaux, La Réunion demeure enfermée dans des impasses multiples, économiques et sociétales. Aucune issue réelle ne se dessine : la confusion des responsabilités perdure et permet à des schémas éculés, présentés comme des innovations, de se reproduire sans fin.
This study aims to realize the difficulties that the island of Reunion is facing a long time and without satisfactory outcome in terms of development. Crises to conflicts, recurring forms, as in their spatial patterns, Reunion remains locked in an impasse multiple, economic and societal. No actual outcome does is emerging: the responsibilities confusion continues and allows worn patterns, presented as innovations, reproduced endlessly.
Réunion

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.4930
http://journals.openedition.org/etudescaribeennes/4930

Éditeur(s) : HAL CCSD American Geophysical Union (AGU) AGU and the Geochemical Society
Résumé : International audience
To study how an impacting plume modifies the mantle lithosphere, we analyzed the microstructures and crystal preferred orientations (CPO) of 29 peridotites and 37 pyroxenites that sample the mantle root of the Ontong Java Plateau (OJP) from 60 to 120 km depth. The peridotites show a strong compositional variability, but homogeneous coarse granular to tabular microstructures, except for those equilibrated at the shallowest and deepest depths, which are porphyroclastic. All peridotites have clear olivine CPO, with dominant fiber-[010] patterns. Low intragranular misorientations and straight grain boundaries in olivine suggest that, above 100 km depth, annealing often followed deformation. Calculated density and P wave velocities of the peridotites decrease weakly with depth. S wave velocities decrease faster, resulting in increasing Vp/Vs ratio with depth. Calculated densities and seismic velocity profiles are consistent with those estimated for normal mantle compositions under a cold oceanic geotherm. Enrichment in pyroxenites may further increase seismic velocities. The calculated seismic properties cannot therefore explain the low S waves velocities predicted by Rayleigh wave tomography and ScS data in the mantle beneath the OJP. Calculated P and S waves anisotropy is variable (2–12%). It is higher on average in the deeper section of the lithosphere. Because olivine has dominantly [010]-fiber CPO patterns, if foliations are horizontal, vertically propagating S waves and Rayleigh waves will sample very weak anisotropy in the OJP mantle lithosphere. Moreover, if the orientation of the lineation changes with depth, the anisotropy-induced contrast in seismic properties might produce an intralithospheric reflector marking the stratification of the OJP mantle root.
ISSN: 1525-2027

hal-01116428
https://hal.archives-ouvertes.fr/hal-01116428
DOI : 10.1002/2014GC005452

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The Aegean domain is a key area for understanding the processes of back-arc extension. Observed deformation pattern and present day kinematics result from the interaction between the southward retreat of the Hellenic trench and the westward escape of Anatolia. Lithosphere-scale analogue models were employed to display that the overall pattern of Aegean extension requires not only the combination of trench retreat and Anatolia escape since middle Miocene but also the presence of an inherited lithosphere-scale mechanical discontinuity: the Vardar Suture Zone (VSZ). The reactivation in dextral shear of the eastern branch of the VSZ accommodates both the trench retreat (NS stretching) and the westward escape of Anatolia (EW shortening) in the Cyclades area since middle Miocene. Additionally, our model shows that the North Anatolian Fault (NAF) is a late structure in the evolution of the Aegean, initiated around 10 Ma after the onset of Anatolia escape. The displacement field at the surface of the model allows the identification of sub-domains, which result from strain partitioning instead of being "rigid microplates", directly comparable to the present-day displacement field (GPS) of the Aegean and western Anatolia. Our model provides a simple but powerful way to look at the dynamics of Aegean extension in two main stages. From middle Eocene to middle Miocene, extension was only driven by the southward retreat of the Hellenic trench at a rate lower than 1 cm*y− 1. Since middle Miocene, the combination of slab rollback with Anatolia westward escape resulted in a southwest direction of trench retreat, with an accelerating rate of up to 3 cm*y− 1.
ISSN: 0040-1951

insu-01066042
https://hal-insu.archives-ouvertes.fr/insu-01066042
https://hal-insu.archives-ouvertes.fr/insu-01066042/document
https://hal-insu.archives-ouvertes.fr/insu-01066042/file/Philippon-brun-tect-2014-HAL.pdf
DOI : 10.1016/j.tecto.2014.04.039

Éditeur(s) : Pêche thonière et dispositifs de concentration de poissons, Caribbean-Martinique, 15-19 Oct 1999
Résumé : For most fisheries, increasing the local production of pelagic fish is the main objective of Fish Aggregating Devices (fads). This does not rule out the existence of a larger-scale impact, especially on the migratory behaviour of fish. The analysis of data collected during 25 experimental fishing surveys around Martinique between 1995 and 1997 has led to the hypothesis that fads influence the migratory behaviour of young dolphinfish. Unlike recent studies of dolphinfish migration in the Caribbean, which tend to show an annual migration pattern with a seasonal passage through the French West Indies, the experimental fishing surveys done over more than a year on a monthly basis on a single cohort, show that the migratory pattern of part of the regional stock could be disrupted. This analysis has made it possible to estimate an average growth rate for this species during the first year of life.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00042/15321/12635.pdf
http://archimer.ifremer.fr/doc/00042/15321/

Éditeur(s) : HAL CCSD BioMed Central
Résumé : International audience
Background: Color polymorphism in the nacre of pteriomorphian bivalves is of great interest for the pearl culture industry. The nacreous layer of the Polynesian black-lipped pearl oyster Pinctada margaritifera exhibits a large array of color variation among individuals including reflections of blue, green, yellow and pink in all possible gradients. Although the heritability of nacre color variation patterns has been demonstrated by experimental crossing, little isknown about the genes involved in these patterns. In this study, we identify a set of genes differentially expressed among extreme color phenotypes of P. margaritifera using a suppressive and subtractive hybridization (SSH) method comparing black phenotypes with full and half albino individuals.Results: Out of the 358 and 346 expressed sequence tags (ESTs) obtained by conducting two SSH libraries respectively, the expression patterns of 37 genes were tested with a real-time quantitative PCR (RT-qPCR) approach by pooling five individuals of each phenotype. The expression of 11 genes was subsequently estimated for each individual in order to detect inter-individual variation. Our results suggest that the color of the nacre is partiallyunder the influence of genes involved in the biomineralization of the calcitic layer. A few genes involved in the formation of the aragonite tablets of the nacre layer and in the biosynthesis chain of melanin also showed differential expression patterns. Finally, high variability in gene expression levels were observed within the black phenotypes.Conclusions: Our results revealed that three main genetic processes were involved in color polymorphisms: the biomineralization of the nacreous and calcitic layers and the synthesis of pigments such as melanin, suggesting that color polymorphism takes place at different levels in the shell structure. The high variability of gene expression found within black phenotypes suggests that the present work should serve as a basis for future studies exploringmore thoroughly the expression patterns of candidate genes within black phenotypes with different dominant iridescent colors.
ISSN: 1471-2164

hal-01260141
https://hal.archives-ouvertes.fr/hal-01260141
https://hal.archives-ouvertes.fr/hal-01260141/document
https://hal.archives-ouvertes.fr/hal-01260141/file/Lemer-2015-BMCGenom-Identification.pdf
DOI : 10.1186/s12864-015-1776-x

Éditeur(s) : HAL CCSD American Geophysical Union (AGU)
Résumé : Mantle xenoliths in Pliocene alkali basalts of the eastern Betics (SE Iberia, Spain) are spinel ± plagioclase lherzolite, with minor harzburgite and wehrlite, displaying porphyroclastic or equigranular textures. Equigranular peridotites have olivine crystal preferred orientation (CPO) patterns similar to those of porphyroclastic xenoliths but slightly more dispersed. Olivine CPO shows [100]-fiber patterns characterized by strong alignment of [100]-axes subparallel to the stretching lineation and a girdle distribution of [010]-axes normal to it. This pattern is consistent with simple shear or transtensional deformation accommodated by dislocation creep. One xenolith provides evidence for synkinematic reactive percolation of subduction-related Si-rich melts/fluids that resulted in oriented crystallization of orthopyroxene. Despite a seemingly undeformed microstructure, the CPO in orthopyroxenite veins in composite xenoliths is identical to those of pyroxenes in the host peridotite, suggesting late-kinematic crystallization. Based on these observations, we propose that the annealing producing the equigranular microstructures was triggered by melt percolation in the shallow subcontinental lithospheric mantle coeval to the late Neogene formation of veins in composite xenoliths. Calculated seismic properties are characterized by fast propagation of P waves and polarization of fast S waves parallel to olivine [100]-axis (stretching lineation). These data are compatible with present-day seismic anisotropy observations in SE Iberia if the foliations in the lithospheric mantle are steeply dipping and lineations are subhorizontal with ENE strike, implying dominantly horizontal mantle flow in the ENE-WSW direction within vertical planes, that is, subparallel to the paleo-Iberian margin. The measured anisotropy could thus reflect a lithospheric fabric due to strike-slip deformation in the late Miocene in the context of WSW tearing of the subducted south Iberian margin lithosphere.
ISSN: 0278-7407

Droits : info:eu-repo/semantics/OpenAccess
hal-01685809
https://hal.archives-ouvertes.fr/hal-01685809
https://hal.archives-ouvertes.fr/hal-01685809/document
https://hal.archives-ouvertes.fr/hal-01685809/file/Hidas_et_al-2016-Tectonics.pdf
DOI : 10.1002/2016TC004165

Éditeur(s) : HAL CCSD Springer Verlag (Germany) Springer Verlag
Résumé : International audience
We report here U-series and trace element data for an olivine-melilitite lava flow, erupted in 1957 in the Virunga volcanic field and known as the Mugogo eruption. Petrological and geochemical data show that the Mugogo magma represents a primary mantle melt, derived from a low degree of melting of a metasomatised mantle source. It is highly enriched in very incompatible trace elements (e.g. more than 300-fold compared to primitive mantle for Th), with a distinctly lower enrichment in Rb, Ba and Sr. The high Th/U and low (230Th/232Th) ratios (4.4 and 0.750, respectively, with a (230Th/238U) ratio of 1.09) are close to the values found for the Nyamuragira basanites. But the most striking feature is the very low (226Ra/230Th) ratio of 0.48, the lowest ever measured in a mafic volcanic rock. The most probable origin of this Ra deficit is the presence of phlogopite (having a high Ra partition coefficient) in the lithospheric mantle, either as a residual phase during low-degree isobaric melting (in batch-melting or a diffusion-controlled melting models), or in a phlogopite-bearing upper mantle through which the melt migrates and equilibrates (in an equilibrium porous flow model commonly used to describe adiabatic melting). The disequilibrium pattern (230Th) > (238U) > (210Pb) ≫ (226Ra), reversed compared to the pattern observed in the Oldoinyo Lengai natrocarbonatite, suggests that a carbonatite melt might have been involved to explain the Ra deficit. We thus discuss the possibility of an early separation of a Ra-enriched carbonate melt either from the olivine-melilitite melt or from a carbonated mantle source, followed by the production of a low-degree melt of olivine-melilitite composition, but the lack of available experimental, petrological and geochemical evidences makes this process somewhat speculative at present. Further studies of recent (<5 ky) olivine-melilitites are needed to check whether the large Ra deficit is a general characteristic of this type of magma that can be used to constrain models of its formation.
ISSN: 0010-7999

hal-01174173
https://hal.archives-ouvertes.fr/hal-01174173
DOI : 10.1007/s00410-015-1124-9

Éditeur(s) : Elsevier Science Bv
Résumé : The breakup of Pangea and onset of growth of the Pacific plate led to several paleoenvironmental feedbacks, which radically affected paleoclimate and ocean chemistry during the Jurassic. Overall, this period was characterized by intense volcanic degassing from large igneous provinces and circum-Panthalassan arcs, new oceanic circulation patterns, and changes in heat and humidity transports affecting continental weathering. Few studies, however, have attempted to unravel the global interactions linking these processes over the long-term. In this paper, we address this question by documenting the global changes in continental drainage and surface oceanic circulation for the whole Jurassic period. For this purpose, we present 53 new neodymium isotope values (εNd(t)) measured on well-dated fossil fish teeth, ichthyosaur bones, phosphatized nodules, phosphatized ooids, and clastic sediments from Europe, western Russia, and North America. Combined with an extensive compilation of published εNd(t) data, our results show that the continental sources of Nd were very heterogeneous across the world. Volcanic inputs from a Jurassic equivalent of the modern Pacific Ring of Fire contributed to radiogenic εNd(t) values (− 4 ε-units) in the Panthalassa Ocean. For the Tethyan Ocean, the average surface seawater signal was less radiogenic in the equatorial region (− 6.3), and gradually lower toward the epicontinental peri-Tethyan (− 7.4), western Russian (− 7.4) and Euro-Boreal seas (− 8.6). Different Nd sources contributed to this disparity, with radiogenic Nd influxes from westward Panthalassan currents or juvenile volcanic arcs in open oceanic domains, and substantial unradiogenic inputs from old Laurasian and Gondwanan shields for the NW Tethyan platforms. Overall, the εNd(t) values of Euro-Boreal, peri-Tethyan, and western Russian waters varied quite similarly through time, in response to regional changes in oceanic circulation, paleoclimate, continental drainage, and volcanism. Three positive shifts in εNd(t) values occurred successively in these epicontinental seas during the Pliensbachian, in the Aalenian-Bathonian interval, and in the mid-Oxfordian. The first and third events are interpreted as regional incursions of warm surface radiogenic currents from low latitudes. The Aalenian-Bathonian shift seems linked to volcanic outbursts in the NW Tethys and/or circulation of deep currents resulting from extensional events in the Hispanic Corridor and reduced influences of boreal currents crossing the Viking Corridor. In contrast, the εNd(t) signals decreased and remained very low (< − 8) during the global warming events of the Toarcian and Late Oxfordian - Early Tithonian intervals. In these greenhouse contexts, a latitudinal expansion of humid belts could have extended the drainage pathways toward boreal Nd sources of Precambrian age and increased the supply of very unradiogenic crustal-derived inputs to seawater. Finally, a brief negative εNd(t) excursion recorded in parallel with regional drops in seawater temperature suggests that southward circulation of cold unradiogenic Arctic waters occurred in the NW Tethys in the Callovian - Early Oxfordian. All these results show that changes in surface oceanic circulation resulting from the Pangean breakup could have regionally impacted the evolution of seawater temperatures in the NW Tethys.
Gondwana Research (1342-937X) (Elsevier Science Bv), 2015-06 , Vol. 27 , N. 4 , P. 1599-1615

Droits : 2014 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved
http://archimer.ifremer.fr/doc/00179/29015/27443.pdf
DOI:10.1016/j.gr.2014.02.006
http://archimer.ifremer.fr/doc/00179/29015/