Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The Chile Triple junction is a natural laboratory to study the interactions between magmatism and tectonics during the subduction of an active spreading ridge beneath a continent. The MLBA plateau (Meseta del Lago Buenos Aires) is one of the Neogene alkali basaltic plateaus located in the back-arc region of the Andean Cordillera at the latitude of the current Chile Triple junction. The genesis of MLBA can be related with successive opening of slabs windows beneath Patagonia: within the subducting Nazca Plate itself and between the Nazca and Antarctic plates. Detailed Ar-40/Ar-39 dating and geochemical analysis of bimodal magmatism from the western flank of the MLBA show major changes in the back-arc magmatism. which occurred between 14.5 Ma and 12.5 Ma with the transition from calc-alkaline lavas (Cerro Plomo) to alkaline lavas (MLBA) in relation with slab window opening. In a second step, at 4-3 Ma, alkaline felsic intrusions were emplaced in the western flank of the MLBA coevally with the MLBA basalts with which they are genetically related. These late OIB-like alkaline to transitional basalts were generated by partial melting of the subslab asthenosphere of the subducting Nazca plate during the opening of the South Chile spreading ridge-related slab window. These basalts differentiated with small amounts of assimilation in shallow magma chambers emplaced along transtensional to extensional zones. The close association of bimodal magmatism with extensional tectonic features in the western MLBA is a strong support to the model of Patagonian collapse event proposed to have taken place between 5 and 3 Ma as a consequence of the presence of the asthenospheric window (SCR-1 segment of South Chile Ridge) below the MLBA area.
ISSN: 0377-0273

hal-00475648
https://hal.archives-ouvertes.fr/hal-00475648
DOI : 10.1016/j.jvolgeores.2009.11.022

Éditeur(s) : HAL CCSD American Geophysical Union (AGU)
Résumé : International audience
In this paper, a combined approach of geomorphic analyses, detailed geological mapping on SPOT 5 satellite images and field surveys, complemented by radiometric dating (Ar-40/Ar-39) allows proposing a new and consistent tectonic configuration for the northeastern Arabia-Eurasia collision zone. It favors a simple strike-slip faulting mechanism in NE Iran accommodating the northward motion of central Iran with respect to Eurasia between the Binalud and Kopeh Dagh mountains. Our results demonstrate that similar to 2 mm/a (similar to 25%) of this northward motion has been transferred from the Binalud to the Kopeh Dagh through the Meshkan Transfer Zone since similar to 5 Ma. The modern state of stress deduced from fault kinematics analyses shows N30 degrees E trending maximum stress axis and confirms a dominant strike-slip faulting mechanism. Combining our geological data with other available data, we conclude that kinematics of deformation can be appropriately described by rigid block faulting in NE Iran; instead, the continuous deformation as it has been thought during the last 3 decades.
ISSN: 0278-7407

hal-00420909
https://hal.archives-ouvertes.fr/hal-00420909
DOI : 10.1029/2008TC002444

Éditeur(s) : HAL CCSD
Résumé : International audience
The Cenozoic weathering of peninsular India has been advocated as a major driver of globalcooling, however, its timing remains virtually unconstrained such that proposed links betweentropical weathering of the Deccan Traps, regional monsoonal intensity and global climate remainsspeculative. To solve this conundrum we present here a revised weathering chronologybased on the identification of lateritic paleosurfaces and their dating using 40Ar/39Ar on supergeneK-rich manganese oxides. We focus on the Indian western passive margin where theWestern Ghats Escarpment (WGE) – a ~1000 m high topographic barrier resulting from thecontinental break up of Greater India – exposes exceptionally preserved weathering profilesfrom the western coastal lowlands to the eastern highland plateaus above the WGE. Four mainlateritic paleosurfaces have been identified: Three in the highland; a high landsurface (Al-Femostly bauxite) at elevation 1200-1000 m asl, an intermediate landsurface covered by a Feduricrustat 1000-900 m asl and a lower pediment landsurface at 850-600 m asl; and one inthe coastal lowland underneath a pediment landsurface at 150-50 m asl. The 40Ar/39Ar agesdocument three major weathering periods over the Cenozoic. The oldest weathering period(W1) is recorded between 53 Ma to 45 Ma both in the highland and the lowland. This correlatesto the Global Eocene climatic Optimum, and allows defining a bauxitic paleolandsurface acrossthe escarpment. Intense bauxitic weathering between ~ 45 and 47 Ma in the lowland indicatethat the WGE was stabilized before ~ 47 Ma on its margin and also implies low denudation rateat the foot of the WGE (<5 m Ma-1) since that time. The second weathering period between37 Ma to 19 Ma (W2) occurred in two distinctive stages (W2a and W2b). From 37 to 26 (W2a),weathering is only recorded in the highland and affect intermediate surfaces. The intensityof chemical weathering decreased sensibly between 32 and 29 Ma – potentially linked to theEarly Oligocene cooling – and resulted in the formation of the lower pediment surface. From~26 Ma to 19 Ma (W2b), only the western coastal lowland weathered while the highland surfacesare mostly dissected. This change and the highland/lowland weathering mitigation after~26 Ma documents a change in climatic patterns over peninsular India that signs the onset ofmodern-like monsoon regime. These results are being interpolated to the Deccan Traps basaltsto quantify their weathering and ultimately estimate of the contribution to CO2 fluxes of thesethree weathering periods and their potential link to Asian Monsoons and global cooling.
Source to Sink: a long term perspective of sediment budgets and sources characterization, Abstracts
Rennes, France

insu-01406455
https://hal-insu.archives-ouvertes.fr/insu-01406455

Éditeur(s) : HAL CCSD
Résumé : International audience
9th International Conference on Sensor Technologies and Applications
Venise, Italy

lirmm-01381091
https://hal-lirmm.ccsd.cnrs.fr/lirmm-01381091

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Investigation of an eclogite xenolith, discovered in a Cretaceous granite from the Central Domain of the Dabieshan massif in eastern China, yields new petrological insights into the high to ultrahigh-pressure metamorphism, experienced by the Qinling-Dabie orogen. Prior to inclusion as a xenolith in the granite during the Early Cretaceous, this eclogite xenolith had recorded a complex metamorphic evolution that complies with subduction and exhumation processes experienced by the continental crust of the South China Block. Well-preserved mineral parageneses substantiate the prograde and retrograde stages revealed by inclusions in porphyroblastic garnet and zoned minerals such as garnet, comphacite and amphibole in the matrix. The relatively low P/T re-equilibration during a latemetamorphic stage was textually inferred by the presence of aluminous and calcic-subcalcic amphiboles such as katophorite, edenite, taramite and pargasite as main matrix phases. According to our U/Pb, Rb/Sr and new 40Ar/39Ar geochronological results, namely 109 ± 1 and 112 ± 2 Ma plateau ages for muscovite and amphiboles, respectively, two successive but distinct cooling stages account for the thermal history of the granite–migmatite gneiss dome that forms the Central Dabieshan Domain. We argue that prior to the Cretaceous doming, the Central Dabieshan Domain experienced a tectono-metamorphic evolution similar to that observed in the high-pressure to ultra high-pressure units developed in the Southern Dabieshan Domain and Hong'an massif.
ISSN: 1437-3254

hal-00104224
https://hal-insu.archives-ouvertes.fr/hal-00104224
https://hal-insu.archives-ouvertes.fr/hal-00104224/document
https://hal-insu.archives-ouvertes.fr/hal-00104224/file/Lin-IntJEarthSciences-2007.pdf
DOI : 10.1007/s00531-006-0129-z

Éditeur(s) : HAL CCSD Le Cherche-Midi
Résumé : Le temps géologique n'est pas le temps des hommes. Notre histoire se raconte en années, siècles, millénaires, celle de la Terre en millions et milliards d'années. Mais quelle horloge utiliser pour dater les évènements géologiques ? L'évolution a d'abord servi d'échelle de temps relative. Il a fallu attendre les découvertes sur l'atome et la radioactivité pour enfin disposer de chronomètres absolus
Terre, planète mystérieuse

hal-00412327
https://hal.archives-ouvertes.fr/hal-00412327

Éditeur(s) : HAL CCSD Inter Research
Résumé : International audience
The main objective of the VULSACO (VULnerability of SAndy COasts to climate change and anthropic pressure) project was to investigate present day and potential future vulnerability of sandy coasts at the 2030 horizon, i.e. on a time scale related to climate variability. The method, based on a multidisciplinary approach bringing together geologists, geographers, physicists, social psychologists, engineers and stakeholders, was structured around 4 axes: field data analysis; numerical modelling; analysis of governance and stakeholder perceptions; and development of vulnerability indexes. This approach was designed to investigate vulnerability at a local scale and was applied to 4 contrasting beaches located in France: Sète Lido (Mediterranean Sea), Truc Vert and La Tresson beaches (Atlantic Ocean), and Dewulf (English Channel). The results focus on decadal and multi-annual beach trends at the Truc Vert beach site. There is almost no trend in beach volume at Truc Vert beach, although there is a variation in this parameter on a cycle of 2 to 3 yr, with variations related to wave energy and probably to indexes of climate variability. Numerical modelling identified the sensitivity of beach responses to changes in wave height and direction, especially in terms of subtidal morphology and the potential development of shoreline instability. Together with the observed offshore wave angle at the Biscay Buoy, these model results suggest that a potential change in wave angle due to climate variability could significantly modify the bars' morphology. The combination of data analysis and numerical modelling contributed to the development of vulnerability indexes designed for sandy coasts, which take into account climate-dependant variables such as waves. This allowed the differentiation of the sites in terms of vulnerability to erosion: Sète Lido and Truc Vert beach were the most and least vulnerable sites, respectively. These indexes help in identifying the dominant components of beach vulnerability, and provide potential for the study of how anthropogenic factors affect vulnerability. The study of stakeholder perceptions and decision-making with regard to climate-related risk also highlighted potential anthropogenic effects on beach vulnerability, and identified possible site-specific outcomes.
ISSN: 0936-577X

hal-00843946
https://hal-brgm.archives-ouvertes.fr/hal-00843946
DOI : 10.3354/cr01153

Éditeur(s) : HAL CCSD American Geophysical Union (AGU)
ISSN: 0278-7407

hal-00406419
https://hal.archives-ouvertes.fr/hal-00406419
DOI : 10.1029/2006TC002022

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
The age of Ultra-high pressure metamorphism and early cooling remains controversial in the Alps. In a new approach to the problem, samples from the undeformed Hercynian metagranite, Brossasco, were studied using an ultra-violet laser ablation microprobe technique for 40Ar-39Ar dating. The results demonstrate the frequent occurence of excess argon with high 40Ar/36Ar ratios (1000-10000) and a strong relationship between apparent ages and metamorphic textures. The highest excess argon ratios are always associated with high closure temperature minerals or large diffusion domains within single mineral phases. The best interpretation of this relationship seems to be that excess argon was incorporated in all phases during the high pressure event, then mixed with an atmospheric component during rapid cooling and retrogression, producing a wide range of argon concentrations and 40Ar/36Ar ratios. In the present case, some ages in the range 60-110 Ma could be explained by the presence of excess argon incorporated around 40-50 Ma ago. Similar results found in other high-pressure terrains in the Alps may reconcile the argon geochronometer with other systems such as Rb/Sr, U/Pb or Sm/Nd. This study therefore calls for an increasing use of high resolution in-situ sampling techniques to clarify the meaning of 40Ar/39Ar ages in many high pressure terrains.
ISSN: 0010-7999

hal-00197563
https://hal.archives-ouvertes.fr/hal-00197563
https://hal.archives-ouvertes.fr/hal-00197563/document
https://hal.archives-ouvertes.fr/hal-00197563/file/Excess_UV_Arnaud_and_Kelley_GCA_Pub_preprint.pdf

Éditeur(s) : HAL CCSD American Geophysical Union (AGU)
Résumé : International audience
The Ama Drime range located at the transition between the high Himalayan range and south Tibet is a N-S active horst that offsets the South Tibetan Detachment System (STDS). Within the horst, a paragneissic unit, possibly attributed to the upper Himalayan crystalline series, overly the lower Himalayan crystalline series Ama Drime orthogneissic unit containing large metabasite layers and pods that have experienced pressure >= 1.4 GPa. Combining structural analysis with new and published pressure-temperature (P-T) estimates as well as U-Th/Pb, Ar-39/Ar-40 and (U-Th)/He ages, the P-T-deformation-time (P-T-D-t) paths of the main units within and on both sides of the horst are reconstructed. They imply that N-S normal faults initiated prior to 11 Ma and have accounted for a total exhumation <= 0.6 GPa (22 km) that probably occurred in two phases: the first one until similar to 9 Ma and the second one since 6 to 4 Ma at a rate of similar to 1 mm/yr. In the Ama Drime unit, 1 to 1.3 GPa (37 to 48 km) of exhumation occurred after partial melting since similar to 30 Ma until similar to 13 Ma, above the Main Central Trust (MCT) and below the STDS when these two fault systems were active together. The switch from E-W (STDS) to N-S (Ama Drime horst) normal faulting between 13 and 12 Ma occurs at the time of propagation of thrusting from the MCT to the Main Boundary Thrust. These data are in favor of a wedge extrusion or thrust system rather than a crustal flow model for the building of the Himalaya. We propose that the kinematics of south Tibet Cenozoic extension phases is fundamentally driven by the direction and rate of India underthrusting.
ISSN: 0278-7407

hal-00486405
https://hal.archives-ouvertes.fr/hal-00486405
DOI : 10.1029/2009TC002551

Éditeur(s) : HAL CCSD BioMed Central
Résumé : International audience
An important objective on diagnosis of patients with Langerhans cell histiocytosis (LCH) is to determine the extent of disease. However, whether systematic extrathoracic investigation is needed in adult patients with clinically isolated pulmonary LCH (PLCH) has not been evaluated
ISSN: 1750-1172

hal-01269910
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01269910
DOI : 10.1186/s13023-016-0387-1
PUBMED : 26833097

Éditeur(s) : HAL CCSD Société géologique de France
Résumé : Upper Carboniferous heating and melting of the middle orogenic crust associated with the emplacement of syntectonic granitoids are documented in the Upper Gneissic Unit of the Livradois area (central part of the French Massif Central). Crustal melting post-dates peak metamorphism conditions (800-625 degrees C, 10-8 kb) dated at 360 +/- 4 Ma (U-Th-Pb on monazite). The P-T evolution of the metamorphic series indicates that Barrovian metamorphism was followed by a decompression (from 10 +/- 1 kbar to 6 +/- 1 kbar) associated with either a decrease in temperature in the southern part of the series or with an increase in temperature (of about 150 degrees C) in the northern part of the series. This evolution records the first step of the exhumation of the series coeval with granitoids intrusion, of which the emplacements were dated at 315 +/- 4 and 311 +/- 18 Ma (U-Pb on zircon). The final stage of the exhumation is associated with an isobaric cooling of the whole series. Similarity of Ar-40/Ar-39 ages for biotite in the paragneisses (307-300 Ma) and K-feldspar in the granitoids (306-300 Ma) document rapid cooling for this stage. Moreover dextral reverse mylonites, at the border and the northern part of the metamorphic series indicate north-south compression coeval with the unroofing of the series. Youngest Ar-40-Ar-39 ages on K-feldspar (274.6 +/- 5 Ma) combined with normal shearing in mylonites limiting the Carboniferous Brassac-les-Mines basin document the late Carboniferous-early Permian stage of extension coeval with the upwelling of the Velay granitic dome.
EISSN: 1777-5817

hal-00617429
https://hal.archives-ouvertes.fr/hal-00617429
DOI : 10.2113/gssgfbull.182.1.5

Éditeur(s) : HAL CCSD
Résumé : Rapport préliminaire journée d'étude du 29 janvier 2011
Exploration pétrolière des gaz de schistes dans le sud de la France.
https://hal.archives-ouvertes.fr/hal-00856278

hal-00856278
https://hal.archives-ouvertes.fr/hal-00856278
https://hal.archives-ouvertes.fr/hal-00856278/document
https://hal.archives-ouvertes.fr/hal-00856278/file/rapport_preliminaire_hydrocarbures_LR_par_UM2_29_janvier_2011.pdf

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
We aimed to assess the impact of a postoperative drainage after RPN. A retrospective multicentric study included RPN performed at eight centers between 2010 and 2014. Three centers stopped using postoperative drainage early in their RPN experience, whereas other institutions systematically left a drain. Preoperative characteristics, complication rates, need for postoperative imaging or procedure (surgical or radiological) and length of hospital stay were compared between the two groups [drainage (D) and no drainage (ND)]. Among 636 RPNs, 140 were done without drainage (22 %). In the ND group, surgeons were more experienced (> 50 cases: 55.7 vs. 15.1 %; p < 0.0001), and tumors were more complex (RENAL score: 7.6 vs. 6.5; p < 0.0001). Complication rates were similar in both groups (21.9 vs. 20.2 %; p = 0.67). The omission of postoperative drainage did not increase requirement of CT scan (RR = 1.03; 95 % CI 0.64-1.67). Length of hospital stay was shorter in the ND group (4.5 vs. 5.5 days; p = 0.007). There were six urinary fistulas: four in the D group (0.8 %) and two in the ND group (1.4 %; p = 0.49). A CT scan was done to confirm the diagnosis of fistula in every case. In multivariate analysis, the omission of drainage was not associated with increased need of postoperative CT scan or major complications but was a predictor of decreased length of stay. The omission of postoperative drainage does not seem to increase the risk of postoperative complications and could safely be omitted after RPN.
ISSN: 0724-4983

hal-01361502
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01361502
DOI : 10.1007/s00345-015-1721-2
PUBMED : 26511751