Éditeur(s) : HAL CCSD American Geophysical Union (AGU)
Résumé : Tectonics, v. 27, p. TC5011, 2008. http://dx.doi.org/10.1029/2007TC002232
International audience
The seismic activity of the Ligurian Basin, the northeastern termination of the western Mediterranean basin, is larger than in surrounding regions, even though recent geodetic studies attest that this area is subject to very low levels of deformation. This basin is an example of a type of passive margins that cannot be considered solely as inert sites of sedimentation and of progressive subsidence and that are reactivated in a compressive pattern; other examples include the Kwanza basin (Angola) and the Brazil margin. We investigated, by means of 2-D thermomechanical modeling, the structural and rheological heterogeneities that can lead to concentration of strain in this marginal basin. We deduced that the deformation of the basin is due to its particular geometric features, narrow and with a thick surrounding continental crust, related to its position at the southern termination of the Alps. This sharp transition, in terms of both geometry and rheological contrast, is a main factor in explaining the weakness of the margin. We discuss the importance of buoyancy forces versus tectonic forces, as well as thermal effects, on the observed reactivation. Influence of contrast in rheology between an oceanic-type crust and continental crust is also studied. Geodynamical implications are proposed for the region. The good agreement between the predicted localized deformation and the observed seismicity distribution should help improve seismic hazard assessment in the region.
ISSN: 0278-7407

hal-00407859
https://hal.archives-ouvertes.fr/hal-00407859
DOI : 10.1029/2007TC002232

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Microstructures, U-Pb SHRIMP zircon ages and temperature estimates were used to constrain the fabric evolution and timing of mylonitisation in the Patos shear zone (NE Brazil). Melt-bearing HT-mylonitic orthogneiss displays solid-state fabrics with coarse quartz ribbons and sutured grain boundaries. K-feldspar is often fractured and shows peripheral myrmekite. The textures typically become magmatic at the contacts with the Espinho Branco anatexite. Zircon crystals from two samples of the leucosome show Paleoproterozoic (ca. 2.2 Ga) inherited cores that are enveloped by recrystallised Neoproterozoic rims. These zircon grains define a discordia with lower intercept ages of 558 and 562 Ma but with large analytical errors. A leucogranite with transitional contacts with host diatexites provides a well-constrained zircon mean age of 566 ± 6 Ma (n = 15, 95% conf.), which is considered the best estimate for the peak metamorphic conditions. The transition from HT-mylonites to fine-grained mylonites and ultramylonites is marked by a progressive grain size reduction assisted by recrystallisation. Quartz crystallographic fabrics display [0 0 0 1] concentrations between Z and Y. K-feldspar and plagioclase fabrics record the activity of the (0 1 0)[0 0 1] and (0 1 0)[1 0 0] slip systems and, in the lower-temperature tectonites, the (1 0 0)[0 1 0] slip system. These results suggest a diachronic evolution in which an initial HT northern domain was deformed by intracrystalline slip and melt-assisted granular flow, followed by medium- to low-temperature solid-state creep in the southern shear zone domain. The mylonites therefore record the rheological heterogeneities responsible for the formation of a late continental shear zone that nucleated under partially molten conditions and was later reactivated through melt-absent strain localization following exhumation.
ISSN: 0301-9268

hal-01053497
https://hal.archives-ouvertes.fr/hal-01053497
DOI : 10.1016/j.precamres.2013.12.020

Résumé : Ce travail de thèse intitulé «Evaluation de marqueurs génétiques du complexe Mycobacterium tuberculosis combinée à l'utilisation d'outils bioinformatiques: apport en épidémiologie et phylogénie de la tuberculose» a consisté en la sélection et l'évaluation de marqueurs minisatellites dans le cadre d'études épidémiologiques et phylogénétiques du bacille tuberculeux, Une première partie a ainsi porté sur l'épidémie de tuberculose en Guadeloupe, Martinique, et Guyane française ainsi que dans un pays continental à faible incidence de tuberculose, la Suède, Les résultats montrent les disparités existant entre les populations de patients tuberculeux des 3 départements français d'Amérique (DFA) ainsi que les similitudes génotypiques existant entre les bacilles tuberculeux. Par ailleurs le rôle majeur joué par les cas d'importation dans l'épidémie de tuberculose a été montré aussi bien dans les DFA qu'en Suède. Nous nous sommes ensuite intéressés à une utilisation optimale des minisatellites pour une meilleure discrimination de la famille génotypique émergeante « Beijing» circulant au Japon (Osaka, Kobe et Okinawa), ainsi qu'en Russie. Nous avons constaté le faible pouvoir discriminant du format classique 12-locus MIRU (Mycobacterial lnterspersed Repetitive Units) et proposons plusieurs nouvelles stratégies de typage basées plusieurs marqueurs minisatellites incluant certains locus hypervariables. Enfin, dans un troisième volet, nous avons étudié la diversité génétique des bacilles tuberculeux circulant actuellement dans la Caraïbe. laquelle semble refléter le passé historique très particulier de cette zone géographique au croisement d'une multitude de peuplements.
This thesis entitled "Evaluation of genetic markers of Mycobacterium tuberculosis combined with the use of bioinformatics tools: input for epidemiology and phylogeny of tuberculosis" deals with the selection and evaluation of minisatellite markers in the context of epidemiological and phylogenetic studies of the tubercle bacillus M. tuberculosis. The first part of the present work has focused on the epidemic of tuberculosis in Guadeloupe, Martinique and French Guiana as well as in a low incidence continental country, i.e Sweden. The results show differences between populations of TB patients in the three French Departments of America and similarities between the genotypes of the circulating tubercle bacilli Moreover, results highlight the important role played by imported cases for TB epidemic the three French departments of America and Sweden. ln a second part, minisatellite markers have been evaluated for a better discrimination of strains of the emerging genotype "Beijing" circulating in Japan (Osaka, Kobe and Okinawa), and Russia. A low discriminatory power of classical format 12-locus MIRU (Mycobacterial lnterspersed Repetitive Units) was observed and new combinations of minisatellites have also been proposed including hypervariable locus. Finally, the genetic diversity of tubercle bacilli circulating in the Caribbean was investigated which currently seem to reflect historical past of this very special region at the intersection of a multitude of cultures and peoples.

http://www.theses.fr/2011AGUY0427/document

Éditeur(s) : HAL CCSD AGU and the Geochemical Society
Résumé : International audience
How reliable are shear wave splitting measurements as a means of determining mantle flow direction? This remains a topic of debate, especially in the context of subduction. The answer hinges on whether our current understanding of mineral physics provides enough to accurately translate between seismic observations and mantle deformation. Here, we present an integrated model to simulate strain-history-dependent texture development and estimate resulting shear wave splitting in subduction environments. We do this for a mantle flow model that, in its geometry, approximates the double-sided Molucca Sea subduction system in Eastern Indonesia. We test a single-sided and a double-sided subduction case. Results are compared to recent splitting measurements of this region by Di Leo et al. (2012a). The setting lends itself as a case study, because it is fairly young and, therefore, early textures from the slab's descent from the near surface to the bottom of the mantle transition zone--which we simulate in our models--have not yet been overprinted by subsequent continuous steady state flow. Second, it allows us to test the significance of the double-sided geometry, i.e., the need for a rear barrier to achieve trench-parallel subslab mantle flow. We demonstrate that although a barrier amplifies trench-parallel subslab anisotropy due to mantle flow, it is not necessary to produce trench-parallel fast directions per se. In a simple model of A-type olivine lattice-preferred orientation and one-sided subduction, trench-parallel fast directions are produced by a combination of simple shear and extension through compression and pure shear in the subslab mantle.
ISSN: 1525-2027

hal-01053506
https://hal.archives-ouvertes.fr/hal-01053506
DOI : 10.1002/2013GC005032

Éditeur(s) : HAL CCSD
Résumé : This study is designed to improve the understanding of structural, mechanical and petrophysical characteristics of deformation bands in porous sandstone such as their potential influence on fluid storage or migration in reservoir setting. Structural and petrophysical analysis of band networks from Provence show that permeability of band is mainly controlled by the degree of cataclasis and diagenetic processes at depth. Map-scale analysis of band networks underlines the major influence of tectonic regime on band distribution, organization and permeability. Band associated to normal-fault regime (cataclasis and low-permeability) are located around map-sclae-fault whereas band associated to thurst-fault regime (moderate cataclasis and permeability) are pervasively distributed in all the area. Reverse-sense band are cataclastic and low-permeabiilty around the Roquemaure thrust, which show the potential role of large-scale fault on structural and petrophysical characteristics of bands. This analysis also shows the influence of fault propagation on formation of low permeability catacastic bands. This analysis suggests also granulometry as factor controlling organization of band networks.A mechanical analysis of deformation bands is realized based on results from Provence. Yield envelopes of these materials are calculated from analytical solution. Triaxial tests done on sandstone (L'Etang quarry, Orange) confirm the shape of yield envelope theoretically calculated. Triaxial tests done on the poorly-lithified sands (Boncavaï quarry, Uchaux) show grain size, sorting and packing influencing yield envelope and cataclastic band localization at shallow burial depth. Stress paths are calculated for burial and tectonic event (extension and contraction) using the relationship between main stress and secondary stresses (K0) calibrated from well data. These different results are integrated into a model which allows to estimate type and structural characteristics of bands susceptible to form for a known geological setting.A structural, mechanical and petrophysical model is established form these results. This model is calibrated by permeability data from deformation bands of Provence and results from the mechanical model of strain localization. This model is also confronted to a synthesis of permeability data from literature, which confirms the influence of the different controlling parameters integrated to the model. This model is applied for two sites of uranium exploration/exploitation in porous sandstone reservoirs and validated by field observations.
Cette étude est destinée à améliorer la compréhension des caractéristiques structurales, pétrophysiques et mécaniques des bandes de déformation dans les grès poreux ainsi que de leur rôle potentiel sur la migration ou le piégeage des fluides en milieu réservoir. L'analyse structurale et pétrophysique des réseaux de bandes de Provence montre que leur perméabilité découle principalement de l'intensité de la cataclase dans leur microstructure et des processus diagénétiques qui peuvent s'y localiser avec la profondeur. L'analyse régionale de ces réseaux de bandes souligne l'influence majeure du régime tectonique sur leur distribution, leur organisation et leur perméabilité. Les bandes associées au régime normal (cataclactiques et peu perméables) sont localisées autour des failles cartographiques, tandis que les bandes associées au régime inverse (modérement cataclastiques et perméables) sont distribuées dans toute la région. Les bandes inverses sont fortement cataclastiques et imperméables uniquement autour du chevauchement de Roquemaure ce qui montre le rôle potentiel de la présence de grande faille sur les caractéristiques structurales et pétrophysiques de ces bandes. D'autre part, cette analyse suggère que la granulométrie de l'encaissant peut influencer l'initiation et l'organisation des réseaux. L'analyse mécanique des bandes de déformation a ensuite été réalisée à partir des résultats obtenus en Provence. L'enveloppe de plasticité de ces matériaux est calculée à l'aide d'une solution analytique. Les essais triaxiaux menés sur le grès de la carrière de l'Etang (orange) confirment la forme de ces enveloppes estimées théoriquement. Les essais réalisés sur les sables de Boncavaï (Uchaux) montrent que la taille des grains, le tri et de la compaction dans ces matériaux peu lithifiés influent sur leurs enveloppes de plasticité et la localisation des bandes cataclastiques à faibles profondeurs. Les trajets de contraintes sont estimés pour les phases d'enfouissement et de chargement tectonique (extension et compression) à partir de la relation entre contrainte principale et contraintes secondaires (K0), calibrée à partir de données de forage. Ces résultats sont intégrés à un modèle permettant d'estimer la nature et les caractéristiques structurales des bandes susceptibles de se former dans un contexte géologique donné. Un modèle structural, mécanique et pétrophysique a été établir à partir de ces différents résultats. Ce modèle est calibré à partir des données de perméabilité mesurées sur les bandes de Provence et des résultats du modèle mécanique de localisation cité précédemment. Ce modèle a ensuite été confronté à une synthèse des données de perméabilité disponibles dans la littérature et confirme l'influence des différents paramètres de contrôle pris en compte dans le modèle. Ce modèle a enfin pu être appliqué sur deux sites d'explorations/exploitations d'uranium en réservoir gréseux poreux et validé par les résultats obtenus, en concordance avec les observations de terrain.
https://tel.archives-ouvertes.fr/tel-01001389

NNT : 2013MON20067
tel-01001389
https://tel.archives-ouvertes.fr/tel-01001389
https://tel.archives-ouvertes.fr/tel-01001389/document
https://tel.archives-ouvertes.fr/tel-01001389/file/36072_BALLAS_2013_archivage-1_cor.pdf

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
The anisotropic single crystal seismic properties are reviewed in the light of recent experimental and theoretical determinations. Although considerable progress has been made on the determination of single crystal properties, data are still lacking, particularly for the temperature derivatives of transition zone and lower mantle phases. The common types of LPO of olivine, opx and cpx are presented together with their associated seismic properties. It is emphasized that simple seismic symmetry pattern of upper mantle rocks are a direct result of the interaction of olivine, opx and cpx. Using the standard structural frame (X lineation, Z pole to foliation) for typical LPOs of olivine, opx and cpx have the maximum Vp parallel to X, in the XZ plane and parallel to Y respectively. Destructive interference occurs between these minerals and hence P-wave anisotropy should be sensitive to the aggregate composition. For shear wave splitting (dVs) typical olivine and opx LPOs result in similar patterns with the maximum dVs in the YZ plane and the fast split shear wave (Vs1) polarized parallel to the foliation. A typical cpx LPO on the other hand produces destructive interference as the max dVs is close to X. By comparison with experiments and numerical simulations, it is estimated that upper mantle samples have an olivine LPO strength which recorded shear strain gamma of between 0.25 and 2.0. Pyrolite and piclogite models are compared with global transverse isotropic models. The slowly reducing P-wave anisotropy in the first 200 km can be explained by a model with constant composition and LPO strength. The sharp decrease in the observed anisotropy in the global models cannot be explained by the transformation of opx to cpx at 300 km, it is proposed that this decrease is due to a reduction in LPO strength from 200 to 350 km at the base of the lithosphere.
Earth's Deep Interior: Mineral Physics and Tomography From the Atomic Scale to the Global Scale

ISBN : 9780875909752
hal-01391524
http://hal.univ-reunion.fr/hal-01391524
http://hal.univ-reunion.fr/hal-01391524/document
http://hal.univ-reunion.fr/hal-01391524/file/Mainprice_AGUmonog_DM_GB_WBI_2000.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Quartz is a common crustal mineral that deforms plastically in a wide range of temperatures and pressures, leading to the development of different types of crystallographic preferred orientation (CPO) patterns. In this contribution we present the results of an extensive modeling of quartz fabric transitions via a viscoplastic self-consistent (VPSC) approach. For that, we have performed systematic simulations using different sets of relative critical resolved shear stress of the main quartz slip systems. We have performed these simulations in axial compression and simple shear regimes under constant Von Mises equivalent strain of 100% (γ = 1.73), assuming that the aggregates deformed exclusively by dislocation glide. Some of the predicted CPOs patterns are similar to those observed in naturally and experimentally deformed quartz. Nevertheless, some classical CPO patterns usually interpreted as result from dislocation glide (e.g. Y-maxima due to prism < a > slip) are clearly not developed in the simulated conditions. In addition we reported new potential preferred orientation patterns that might happen in high temperature conditions, both in axial compression and simple shear. We have demonstrated that CPOs generated under axial compression are usually stronger that those predicted under simple shear, due to the continuous rotation observed in the later simulations. The fabric strength depends essentially on the dominant active slip system, and normally the stronger CPOs result from dominant basal slip in < a >, followed by rhomb < a > and prism [c] slip, whereas prism < a > slip does not produce strong fabrics. The opening angle of quartz [0001] fabric used as a proxy of temperature seems to be reliable for deformation temperatures of ~ 400 °C, when the main slip systems have similar behaviors.
ISSN: 0040-1951

hal-01115674
https://hal.archives-ouvertes.fr/hal-01115674
DOI : 10.1016/j.tecto.2014.08.011

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Deep crustal and mantle rocks are exhumed in core complex mode of extension in three types of structures: metamorphic core complexes, oceanic core complexes and magma poor passive margins. Using available analogue and numerical models and their comparison with natural examples, the present paper reviews the mechanical processes involved in these different types of extensional setting. Three main aspects are considered: i) the primary role of lithosphere rheology, ii) the lithosphere-scale patterns of progressive deformation that lead to the exhumation of deep metamorphic or mantle rocks and iii) the initiation and development of detachment zones. Crustal core complexes develop in continental lithospheres whose Moho temperature is higher than 750 °C with “upper crust-dominated” strength profiles. Contrary to what is commonly believed, it is argued from analogue and numerical models that detachments that accommodate exhumation of core complexes do not initiate at the onset of extension but in the course of progressive extension when the exhuming ductile crust reaches the surface. In models, convex upward detachments result from a rolling hinge process. Mantle core complexes develop in either the oceanic lithosphere, at slow and ultra-slow spreading ridges, or in continental lithospheres, whose initial Moho temperature is lower than 750 °C, with “sub-Moho mantle-dominated” strength profiles. It is argued that the mechanism of mantle exhumation at passive margins is a nearly symmetrical necking process at lithosphere scale without major and permanent detachment, except if strong strain localization could occur in the lithosphere mantle. Distributed crustal extension, by upper crust faulting above a décollement along the ductile crust increases toward the rift axis up to crustal breakup. Mantle rocks exhume in the zone of crustal breakup accommodated by conjugate mantle shear zones that migrate with the rift axis, during increasing extension.
ISSN: 0040-1951

insu-01610186
https://hal-insu.archives-ouvertes.fr/insu-01610186
https://hal-insu.archives-ouvertes.fr/insu-01610186/document
https://hal-insu.archives-ouvertes.fr/insu-01610186/file/brun-tect-2017.pdf
DOI : 10.1016/j.tecto.2017.09.017