Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
During compressive events, deformation in sedimentary basins is mainly accommodated by thrust faulting and related fold growth. Thrust faults are generally rooted in the basement and may act as conduits or barriers for crustal fluid flow. Most of recent studies suggest that fluid flow through such discontinuities is not apparent and depends on the structural levels of the thrust within the fold-and-thrust belt. In order to constrain the paleofluid flow through the Jaca thrust-sheet-top basin (Paleogene southwest-Pyrenean fold-and-thrust belt) this study compares on different thrust faults located at different structural levels. The microstructures in the different fault zones studied are similar and consist of pervasive cleavage, calcite shear veins (SV1), extension veins (EV1) and late dilatation veins (EV3). In order to constrain the nature and the source of fluids involved in fluid-rock interactions within fault zones, a geochemical approach, based on oxygen and carbon stable isotope and trace element compositions of calcite from different vein generations and host rocks was adopted. The results suggest a high complexity in the paleohydrological behaviors of thrust faults providing evidence for a fluid-flow compartmentalization within the basin. Previous studies in the southern part of the Axial Zone (North of the Jaca basin) indicates a circulation of deep metamorphic water, probably derived from the Paleozoic basement, along fault zones related to the major basement Gavarnie thrust. In contrast, in northern part of the Jaca basin, the Monte Perdido thrust fault is affected by a closed hydrological fluid system involving formation water during its activity. The Jaca and Cotiella thrust faults, in turn, both located more to the south in the basin, are characterized by a composite fluid flow system. Indeed, stable isotope and trace element compositions of the first generations of calcite veins suggest a relatively closed paleohydrological system, whereas the late calcite vein generations, which are probably associated with the late tectonic activity of the basin, support a contribution of both meteoric and marine waters. Based on these results, a schematic fluid-flow model is presented. This model allows visualization of three main fluid flow compartments along a N-S transect.
ISSN: 0264-8172

hal-00963606
https://hal.archives-ouvertes.fr/hal-00963606
DOI : 10.1016/j.marpetgeo.2013.09.005

Éditeur(s) : HAL CCSD
Résumé : The present study addresses the question of increasing need in water supply. One line of research consists in investigating karst aquifers that represent significant water supplies for the areas around the Mediterranean. This work aims at developing a methodology of predictive evaluation of karst distribution and karst thickness within the carbonate massifs. It is based on the study of the Tethysian carbonate platform from the area of Montpellier, South of France. This area underwent a polyphased, complex, tectonic evolution, involving successive karst forming events. The approach is based on the relationships between eustacy and geodynamics, on one hand, and base-level variation recorded within palaeokarsts, on the other hand. Sedimentary fill of palaeokarsts allows to identify distinct karstification phases and sometimes to date them. It is a marker of base-level variations, which we attempt to quantify, that is responsible for karst formation and karst filling and sealing. For three palaeokarsts of regional extent, we analyze : karst sedimentary-fill, the distribution along upstream-downstream profile, the vertical extension of palaeokarsts, indicative of the base-level lowering. - The " Bauxite palaeokarst " results from the two-stage evolution of the " Isthme Durancien " : i) Bauxitic weathering of the Neocomian cover over the southern Massif Central , related to an inversion during Barremian ; ii) ≥1600 m uplift and exhumation during Aptian-Albian, inducing erosion of alterites, upstream, and deposition of detrital bauxites, downstream. - The " Early Paleocene palaeokarsts with marine sedimentary-fill " indicate base level variations of more than 350m in the upstream area. It is suggested here that such base-level variations, exceeding eustacy and recorded in tabular undeformed series, result from desiccation-flooding events in an endoreic silled basin. - The " Miocene palaeokarst with Cevennes-sourced sediment-fill " records a Serravalian-Tortonian base-level drop, depicted by canyon incision in the hinterland of the Gulf of Lion Margin. Uplift values of ≥ 400m upstream, about 250m in an intermediate area and 10's of m downstream, are measured. The present 3D geometry and distribution of carbonate massifs (exposed and covered) are modeled in the study area, from the Cevennes to the Mediterranean. The 3D geological model integrates seismic reflection, borehole and gravimetric data. Tectonic restoration of a N-S section, extracted from the 3D model, allows to reconstruct paleo-base-levels with respect with the carbonate massifs, at different stages of deformation and successive phases of karstification. The 3D paleo-flows through carbonates across the study area, are thus constrained, especially during the Messinian desiccation stage. Application of the results to hydrogeology leads to the following : - Uplift of upstream hinterland (Cretaceous, Miocene) produces large amplitude karsts, but they do not make significant reservoirs. - Karstification responsible for the development of important and deep karst reservoirs is related to desiccation of endoreic basins (early Paleocene and Messinian). - Theses two events have produced two main deep karst reservoirs, with a gravimetric signature : (1) Upstream of Montpellier Thrust, between Pic St Loup, Les Matelles Fault and Hérault Basin, a deep karsts developed over 900m thickness in the Malm limestone, during Paleocene. (2) Downstream (south) of Montpellier Thrust, the coastal karsts extend offshore over more than 10km, they are sealed by a thick Miocene to Quaternary cover, and they result from the Messinian event.
Cette étude s'inscrit dans un contexte de demande croissante en ressources en eau, conduisant à mieux contraindre et estimer la distribution des aquifères karstifiés qui représentent une ressource importante, notamment sur le pourtour méditerranéen. Le but de ce travail est d'élaborer une méthode prédictive de la distribution de la karstification et de l'épaisseur de massifs carbonatés karstifiés, notamment pour les karsts profonds. La méthodologie est développée à partir de l'étude des karsts de la plateforme carbonatée téthysienne du Languedoc montpelliérain; région qui a subi une histoire tectonique complexe et polyphasée, entrainant des phases de karstification successives. Elle est basée sur la compréhension des relations entre eustatisme, géodynamique et niveau de base, enregistrées par les paléokarsts de la région. Le remplissage sédimentaire des paléokarsts permet d'identifier les épisodes de karstification et de les dater ; c'est un marqueur des variations -que l'on cherche à quantifier- du niveau de base local responsable de la formation et du comblement des karsts. On analyse 3 paléokarsts d'extension régionale dont on peut étudier : le remplissage karstique, la distribution le long de profils amont-aval et l'extension verticale indicatrice de l'amplitude de l'abaissement du niveau de base dont il est issu. On en déduit les causes géodynamiques à l'origine de leur formation: - Le " paléokarst des bauxites " à remplissage caractéristique, résulte de l'évolution en 2 phases de " l'Isthme Durancien " : altération bauxitique de la couverture néocomienne sur le sud du Massif Central, liée à une inversion au Barrémien, suivi d'une surrection ≥ 1600m à l'Aptien-Albien, causant l'érosion des altérites en amont et le dépôt des bauxites détritiques en aval. - Le " paléokarst à remplissage marin paléocène inférieur " indique des variations du niveau de base local ≥350m dans la zone amont sud-cévenole. On propose que ces variations de niveau de base d'amplitude très supérieures aux variations eustatiques et dans une zone faiblement déformée, résultent d'assèchements et d'ennoiements d'un bassin endoréique à seuil. - Le " paléokarst à remplissage détritique d'origine cévenole ", enregistre la chute du niveau de base au Serravalien-Tortonien, qui se traduit par l'incision de canyons dans l'arrière-pays de la marge du Golfe du Lion. On détermine une surrection de plus de 400 mètres à l'amont, près de 250m dans les blocs faillés intermédiaires et quelques dizaines de mètres dans la zone avale. En parallèle, on établit la géométrie et la distribution actuelles des massifs carbonatés dans la zone d'étude (y compris sous couverture), en construisant un modèle géologique 3D, des Cévennes à la Méditerranée. On intègre les données de sismique réflexion, de forages et les données gravimétriques. La restauration tectonique séquentielle d'une coupe Nord-Sud extraite du modèle géologique permet d'appréhender la position des paléo-niveaux de base par rapport aux massifs carbonatés, pour chaque époque de karstification. On déduit l'organisation 3D des paléo-écoulements à travers la géométrie complexe des massifs carbonatés languedociens, notamment pendant l'évènement messinien. En terme d'évaluation de la ressource en eau, on déduit que: - Les surrections de l'arrière-pays (Crétacé " moyen ", Miocène) produisent des karsts de grande amplitude, mais ne constituent pas de réservoirs significatifs. - La karstification à l'origine de réservoirs exploitables importants et profonds est créée par l'assèchement de bassins endoréiques, qui ont affecté la région au Paléocène inférieur et au Messinien . - Ces deux évènements sont à l'origine de deux principaux réservoirs karstiques profonds qui ont une signature gravimétrique : (1) En amont du chevauchement de Montpellier, entre le Pic Saint Loup, la faille des Matelles et le bassin de l'Hérault, le karst profond se développe sur une épaisseur atteignant 900m, et est attribuée à l'événement du Paléocène. (2) Au Sud du chevauchement de Montpellier les karsts côtiers s'étendent jusqu'à plus de 10 km au large, scellés par une épaisse couverture Miocène et Plio-Quaternaire, et résultent de l'événement Messinien.
https://tel.archives-ouvertes.fr/tel-00936257

tel-00936257
https://tel.archives-ouvertes.fr/tel-00936257
https://tel.archives-ouvertes.fr/tel-00936257/document
https://tel.archives-ouvertes.fr/tel-00936257/file/thA_se_husson_couleurs.pdf

Éditeur(s) : Amer Geophysical Union
Résumé : The Algerian margin has originated from the opening of the Algerian basin about 25-30 Ma ago. The central margin provides evidence for large-scale normal faults of Oligo-Miocene age, whereas transcurrent tectonics characterizes the western margin. A set of NW-SE oriented dextral transform faults was active during basin opening and divided the 600 km long central margin into segments of similar to 120-150 km. The upper Miocene, Plio-Quaternary, and present-day tectonic setting is, however, compressional and supports the occurrence of a margin inversion, a process still poorly documented worldwide. We show that the central Algerian margin represents a rare example of inverted margin, where the process of subduction inception is particularly well expressed and helps understand how extensional and transtensive structures are involved in margin shortening. Using multibeam bathymetry and multichannel seismic reflection sections from the MAR-ADJA 2003 and 2005 cruises, we evidence Pliocene-Pleistocene shortening with contrasting styles along the margin between west (Khayr Al Din bank) and east (Boumerdes-Dellys margin) of Algiers. Pre-Miocene structures such as basement highs and transform faults appear to control changes of the deformation pattern along this part of the margin, resulting in different widths, geometries, and relative positions of folds and faults. Plio-Quaternary and active blind thrust faults do not reuse Oligo-Miocene normal and transform faults during inversion, but instead grow within the continental margin (as testified for instance by the 21 May 2003 M-w 6.8 Boumerdes-Zemmouri earthquake), at the foot of the continental slope and at the northern sides of basement highs interpreted as stretched continental blocks of the rifted margin. The inherited structures of the margin appear, therefore, to determine this deformation pattern and ultimately the earthquake and tsunami sizes offshore. The complex geometry of the fault system along the Algerian margin suggests a process of initiation of subduction in its central and eastern parts.
Tectonics (0278-7407) (Amer Geophysical Union), 2010-03 , Vol. 29 , N. TC2008 , P. 1-22

Droits : 2010 American Geophysical Union
http://archimer.ifremer.fr/doc/00008/11883/9286.pdf
http://archimer.ifremer.fr/doc/00008/11883/9287.pdf
DOI:10.1029/2009TC002547
http://archimer.ifremer.fr/doc/00008/11883/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
This study provides new Ar-40/Ar-39 geochronological constraints on the age of the Alpine tectonics in the Aspromonte Massif (southern part of the Calabrian-Peloritan belt). This massif exposes the upper units of the Calabride Complex which originated from the European continental margin. The Calabride Complex was incorporated in the Alpine orogenic wedge and then integrated into the Apennines and Maghrebides fold- and-thrust belts. Throughout the Calabride Complex there is evidence for a two stage tectonic history, which remains however rather poorly dated: Alpine nappe stacking is followed by extensional reworking along the former thrust contacts or along new detachment surfaces. Our new ages suggest that exhumation of the uppermost units, which accompanied nappe stacking, probably started at 45 Ma and that the deepest units were almost completely exhumed at 33 Ma. This kinematics probably corresponds to syn-orogenic extension while the end of exhumation is clearly related to the extensional tectonics dated at 28.6 Ma along detachment structures.;Our geochronological data reveal a very short lag time between accretional and extensional processes in this part of the Mediterranean Alpine orogenic belt. The direction of extension, when the units are restored to their initial position (i.e. before the opening of the Western Mediterranean basins and the bending of the arc) is NNE-SSW. Such a direction does not fit with the eastward slab-retreat model generally put forward to explain extension in the Western Mediterranean. In contrast, we provide evidence for roughly N-S middle Oligocene extension in the accretionary prism, not previously described in this part of the Mediterranean domain.
ISSN: 0024-4937

hal-00475649
https://hal.archives-ouvertes.fr/hal-00475649
DOI : 10.1016/j.lithos.2009.10.011

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We review the geodynamic evolution of the Aegea-Anatolia region and discuss strain localisation there over geological times. From Late Eocene to Present, crustal deformation in the Aegean backarc has localised progressively during slab retreat. Extension started with the formation of the Rhodope Metamorphic Core Complex (Eocene) and migrated to the Cyclades and the northern Menderes massif (Oligocene and Miocene), accommodated by crustal-scale detachments and a first series of core complexes (MCCs). Extension then localised in Western Turkey, the Corinth Rift and the external Hellenic arc after Messinian times, while the North Anatolian Fault penetrated the Aegean Sea. Through time the direction and style of extension have not changed significantly except in terms of localisation. The contributions of progressive slab retreat and tearing, basal drag, extrusion tectonics and tectonic inheritance are discussed and we favour a model (1) where slab retreat is the main driving engine, (2) successive slab tearing episodes are the main causes of this stepwise strain localisation and (3) the inherited heterogeneity of the crust is a major factor for localising detachments. The continental crust has an inherited strong heterogeneity and crustal-scale contacts such as major thrust planes act as weak zones or as zones of contrast of resistance and viscosity that can localise later deformation. The dynamics of slabs at depth and the asthenospheric flow due to slab retreat also have influence strain localisation in the upper plate. Successive slab ruptures from the Middle Miocene to the Late Miocene have isolated a narrow stripe of lithosphere, still attached to the African lithosphere below Crete. The formation of the North Anatolian Fault is partly a consequence of this evolution. The extrusion of Anatolia and the Aegean extension are partly driven from below (asthenospheric flow) and from above (extrusion of a lid of rigid crust).
ISSN: 0040-1951

insu-00715950
https://hal-insu.archives-ouvertes.fr/insu-00715950
https://hal-insu.archives-ouvertes.fr/insu-00715950/document
https://hal-insu.archives-ouvertes.fr/insu-00715950/file/Jolivet-Aegean_Tectonophysics-2012.pdf
DOI : 10.1016/j.tecto.2012.06.011

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
In Western Mediterranean, the Rif belt in Morocco is part of the Gibraltar Arc built during the Tertiary in the framework of Eurasia-Africa convergence. The structural and metamorphic evolution of the internal units of this belt as well as their timing, crucial to constrain the geodynamic evolution of the Alboran Sea, is still largely debated.Our study on the Ceuta Peninsula (Northern Rif) provides new structural, petrological and geochronological data (U-Th-Pb, Ar-Ar), which allow to precise the tectono-metamorphic evolution of the Lower Sebtides metamorphic units with:(1) a syn-metamorphic thrusting event developed under granulite facies conditions (7–10 kbar and 780–820 °C). A major thrust zone, the Ceuta Shear Zone, drove the emplacement of metapelites and peridotitic lenses from the Ceuta Upper Unit over the orthogneisses of the Monte Hacho Lower Unit. This compressional event ended during the Upper Oligocene.(2) an extensional event developed at the boundary between amphibolite and greenschist facies conditions (400–550 °C and 1–3 kbar). During this event, the Ceuta Shear Zone has been reactivated as a normal fault. Normal ductile shear zones contributed to the final exhumation of the metamorphic units during the Early Miocene.We propose that the compressional event is related to the formation of an orogenic wedge located in the upper plate, in a backward position, of the subduction zone driving the geodynamic evolution of the Alboran domain. In this context, the episode of lithospheric thinning could be related to the opening of the Alboran basin in a back-arc position.Furthermore, unlike the previous models proposed for the Rif belt, the tectonic coupling between mantle peridotites and crustal metamorphic rocks occurred in Ceuta Peninsula at a depth of 20–30 km under high temperature conditions, before the extensional event, and thus cannot be related to the back-arc extension.
ISSN: 0040-1951

insu-01682810
https://hal-insu.archives-ouvertes.fr/insu-01682810
DOI : 10.1016/j.tecto.2017.11.028

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
In orogenic systems, thrust faults play a major role in stacking different tectonic units and may act as conduits for the expulsion of large amounts of fluid of different origins (metamorphic, diagenetic, meteoric). This study focuses on the Monte Perdido thrust unit emplaced in the Paleogene Jaca thrust-sheet-top basin, in the SW-central Pyrenees. We aim to decipher the mechanisms and P-T conditions of deformation in fault zones and characterize the related fluid involvement, through combined microstructural, geochemical and microthermometry analyses. Two thrust faults cutting platform limestones, marls and siliciclastic turbidites of the lower part of the basin-fill (Paleocene-lower Eocene) have been studied. The fault zones are characterized by metre-thick shear zones with highly deformed, foliated clay-rich sediments. Foliation is underlined by preferentially oriented phyllosilicates. Several generations of shear and extension calcite, quartz and chlorite-bearing veins attest to fluid-rock interactions during a multi-stage deformation. Microstructural observations and stable isotope analyses on calcite from veins and host sediments suggest that deformation was aseismic and dominated by diffusive mass transfer from pressure solution sites along cleavage and stylolites to the precipitation sites in veins, with mineralizing fluids in equilibrium with the host sediments. Our results suggest an essentially closed hydrologic system, and imply the absence of significant fluid flow along the studied fault zones. Microthermometric study on fluid inclusions present in calcite and quartz veins, and calcite-quartz oxygen isotopic fractionation determined for the first generation shear veins, allow a geothermal gradient of 34 degrees C/km to be estimated. Analytical results demonstrate an evolution of the fault zones in three stages. The first stage was related to the emplacement of the Monte Perdido thrust unit during the middle Eocene at a temperature of similar to 208 degrees C and a burial depth of similar to 5.7 km. The second stage corresponds to a fault reactivation at a temperature of similar to 240 degrees C and a burial depth of similar to 6.5 km. The latter deformation may have been related to folding of the Monte Perdido thrust unit during the emplacement of the underlying Gavarnie thrust unit during the late Eocene-early Oligocene, with deeper burial resulting from aggradation of the thrust-sheet-top basin-fill. The last event corresponds to the formation of a dilatant vein system likely related to the exhumation of the massif.
ISSN: 0191-8141

hal-00644828
https://hal.archives-ouvertes.fr/hal-00644828
DOI : 10.1016/j.jsg.2011.06.006

Éditeur(s) : HAL CCSD Geological Society of London
Résumé : International audience
In Eastern China, the North China Block (NCB) has experienced a complex tectonic evolution during Late Palaeozoic to Mesozoic times. The unconformable sedimentary cover, which ranges in age from Neoproterozoic to Permian, underwent two tectonic episodes in Early Triassic and Cretaceous times. An early north–south compressional phase, D1, characterized by north-verging recumbent folds with east–west-trending axes and top-to-the-north ductile shear zones can be observed in a gabbroic pluton and the Neoproterozoic sedimentary host rocks. The available radiometric ages allow us to interpret this event as an Early Triassic back-thrusting related to the final stage of the collision between the North China and South China Blocks. During the LateMesozoic, an extensional event characterized by (1) half-grabens filled by continental terrigeneous red beds and lava flows, (2) low-angle detachment faults, (3) synkinematic granitic plutons, and (4) metamorphic core complexes is widespread in the Eastern Liaoning Peninsula. This extensional D2 event can be subdivided into a ductile deformation and a brittle deformation, corresponding to different expressions of crustal deformation. In every area studied in the Eastern Liaoning Peninsula, the ductile D2 deformation is characterized by a NW–SE-trending stretching lineation with a top-to-the-NWsense of shear.Mica and amphibole fromthe metamorphic country rocks, granodioritic or monzogranitic plutons and their mylonitized margins yield 40Ar/39Ar ages ranging from 130 to 120 Ma. These dates support fast cooling and exhumation rates coeval with the extensional tectonics. The brittle D2 deformation is responsible for the formation of high-angle normal faults marked by low-temperature cataclasites bounding half-grabens. During the Mesozoic, the tectonic regime of Eastern China experienced a significant inversion from compression to extension. The Eastern Liaoning Peninsula massif provides an example of this geodynamic transition.
ISSN: 2041-4927

hal-00134055
https://hal-insu.archives-ouvertes.fr/hal-00134055
DOI : 10.1144/SP280.7

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We investigate the timing of end of motion along the South Tibet Detachment System (STDS), a major normal fault system that runs parallel to the Himalayan range for more than 1500 km. Near Dinggye (similar to 28 degrees 10'N, 87 degrees 40'E), the STD dips similar to 10 +/- 5 degrees to the North and separates Paleozoic Tethyan series from Upper Himalayan Crystalline Series (UHCS). Immediately below the STD, the UHCS is highly deformed in the STD shear zone, lineations trend NNE and the shear senses are top to the NE. In micaschist, the P-T path constrained by pseudosection and garnet chemistry, shows successive metamorphic conditions of similar to 0.6 GPa and similar to 550 degrees C and 0.5 GPa and 625 degrees C. U/Pb dating of monazites and zircons in deformed and undeformed leucogranites suggests that ductile deformation lasted until at least similar to 16 Ma but ended prior to similar to 15 Ma in the STD shear zone similar to 100 m below the detachment. Ar/Ar micas ages in the footwall span between similar to 14.6 and 13.6 Ma, indicating rapid cooling down to similar to 320 degrees C, and suggesting persistence of normal faulting, at that time. The STDS is cut and offset by the N-S trending Dinggye active normal fault which initiated prior to 11 Ma thus providing a minimum bound for the end of STDS motion. These data are interpreted as reflecting 0.3 GPa (11 km) to 0.6 GPa (22 km) of exhumation along the STDS starting prior to similar to 16 Ma, ending between 13.6 and 11 Ma. The 1000 km long stretch of the STDS east of the Gurla Mandata probably stopped almost synchronously between 13 and 11 Ma ago, coevally with a sudden switch from NNE-SSW to E-W extension at the top of the accretionary prism, with a jump of the major thrust from the lower Main Central Thrust (MCTI) to the Main Boundary Thrust (MBT), and with a change in the India and Asia convergence direction. This synchronism is probably better explained in the frame of a thrust wedge or thrust system model than a lower channel flow model. West of the Gurla Mandata the STDS appears to stop 5 to 3 Ma earlier, possibly related to local interactions with the Karakorum fault in a way that needs to be understood.
ISSN: 0012-821X

hal-00475652
https://hal.archives-ouvertes.fr/hal-00475652
DOI : 10.1016/j.epsl.2009.12.035

Éditeur(s) : HAL CCSD MAIK Nauka/Interperiodica
Résumé : International audience
The paper is concerned with the kinematics of the major faults, their pattern, and the time of occurrence of compression and extension deformations in the southeast of the Eastern Sayan. The geometry of the mountain ranges and the kinematics of the major faults exhibit northeast-oriented compression responsible for the current processes of relief formation, which corresponds to the direction of the vector of deformations associated with the Indo-Asian collision. The results obtained thus far may be indicative of the remote influence of collision on the orogenic activity and transpressional deformations in the Eastern Sayan since the end of the Miocene. Morphotectonic analysis has shown that the areas of Quaternary extension- related deformations in the Eastern Sayan are not a response to active rifting in the Baikal Rift Zone. The position and geometry of the subsided blocks and magma ruptures point to the fact that they form locally as extension structural elements near the strike-slip faults. The strike-slip and thrust faults are widespread and play the leading role in the development of the southeastern part of the Eastern Sayan.
ISSN: 0016-8521

insu-00667345
https://hal-insu.archives-ouvertes.fr/insu-00667345
DOI : 10.1134/S001685211101002X

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 Elsevier
Résumé : International audience
Lithospheric-scale faults related to oblique subduction are responsible for some of the most hazardous earthquakes reported worldwide. The mega-thrust in the Sunda sector of the Sumatran oblique subduction has been intensively studied, especially after the infamous 2004 Mw 9.1 earthquake, but its onshore kinematic complement within the Sumatran subduction, the transform Sumatran Fault System, has received considerably less attention. In this paper, we apply a combination of analysis of Digital Elevation Models (ASTER GDEM) and field evidence to resolve the kinematics of the leading edge of deformation of the northern sector of the Sumatran Fault System. To this end, we mapped the northernmost tip of Sumatra, including the islands to the northwest, between 4.5°N and 6°N. Here, major topographic highs are related to different faults. Using field evidence and our GDEM structural mapping, we can show that in the area where the fault bifurcates into two fault strands, two independent kinematic regimes evolve, both consistent with the large-scale framework of the Sumatran Fault System. Whereas the eastern branch is a classic Riedel system, the western branch features a fold-and-thrust belt. The latter contractional feature accommodated significant amounts (c. 20%) of shortening of the system in the study area. Our field observations of the tip of the NSFS match a strain pattern with a western contractional domain (Pulau Weh thrust splay) and an eastern extensional domain (Pulau Aceh Riedel system), which are together characteristic of the tip of a propagating strike-slip fault, from a mechanical viewpoint. For the first time, we describe the strain partitioning resulting from the propagation of the NSFS in Sumatra mainland. Our study helps understanding complex kinematics of an evolving strike-slip system, and stresses the importance of field studies in addition to remote sensing and geophysical studies.
ISSN: 0040-1951

hal-01467196
https://hal.archives-ouvertes.fr/hal-01467196
DOI : 10.1016/j.tecto.2016.04.050

Éditeur(s) : HAL CCSD Springer
Résumé : The analysis of three different regions of the South- Pyrenean fold-and-thrust belt reveals that during the Tertiary compression the hydrological system was compartmentalised in time and space. During the early-middle Eocene, when the thrust front affected marine soft-sediments in the Ainsa basin, the thrust fault zones were dominated by formation fluids derived from Eocene marine waters trapped in the underlying Eocene marls, although influences of meteoric waters were also present. During the middle-late Eocene, when the thrust front emplaced marine rocks over continental redbeds in the eastern Catalan basin (L'Escala thrust), the thrust fault zones were dominated by meteoric fluids. These fluids flowed preferentially along these faults, draining laterally the meteoric fluids and acting as barriers hindering their flowing towards more external parts of the belt. During the Oligocene, the most external part of the fold-and-thrust belt in the eastern Catalan basin developed on top of a salt detachment horizon. The thrust front affected continental materials of late Eocene-Oligocene age. At this moment, the thrusts were conduits for meteoric fluids arriving from the surface and also for evolved meteoric fluids migrating over short distance upwards after being in contact with the underlying evaporitic beds. Most of the fractures show a similar sequence of microfractures. Microfractures of stage 1 formed when the sediment was poorly lithified. Microfractures of stage 2 represent the main episode of vein formation which developed when a progressive induration of the host sediment occurred. During microfracture stage 3, formed in an extensional regime, the host sediment was more indurated. The repetition of this sequence of microfractures in different fracture generations of the same outcrop indicates that the sediment induration was restricted to the vicinity of the vein. Away from the veins, the sediment remained poorly lithified during the entire deformation cycle. Calcite cement within the host rock precipitated later than the syn-compressive veins, when the sediment was more indurated. Elemental geochemistry and stable isotopes of the calcite veins indicates that early generation of microfractures is infilled by local fluids (either marine or meteoric), whereas external fluids (meteoric or evolved meteoric) infilled the main compressive stage of microfractures. The hot temperature of these fluids (157°C to 183°C in the Atiart-Arro example) indicates their circulation through deep parts of the thrust belt. The progressive increase of the 87Sr/86Sr ratio through time is due to the progressive uplift, exposure and erosion of the internal Pyrenean Axial Zone.
Thrust belts and foreland basins, from fold kinematics to hydrocarbon systems

hal-00408001
https://hal.archives-ouvertes.fr/hal-00408001
DOI : 10.1007/978-3-540-69426-7_5

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
In the Chalkidiki Peninsula of northern Greece a thrust complex made of a basement (Vertiskos Unit), a cover (Circum–Rhodope belt) and arc/back-arc units (Chortiatis Magmatic Suite and eastern Vardar Ophiolites) is exposed in the Chalkidiki Peninsula of northern Greece. The complex forms the western part of the Rhodope Metamorphic Province and lies on the hanging-wall of the Kerdylion Detachment, the structure responsible for the exhumation of the Southern Rhodope Core Complex and the most prominent and visible ductile structure related to the Tertiary Aegean extension. The Chalkidiki thrust complex arguably preserves a complete record of Cretaceous deformation and related fabrics. In this contribution we describe the geometry of foliation, stretching lineation and shear sense(s) on a regional scale. The regional foliation strikes NW–SE and displays different patterns in the three studied units: (i) dominantly dipping at low angle in the Vertiskos Unit, (ii) affected by upright folding in the Circum–Rhodope belt and (iii) systematically steeply dipping to the NE in the Chortiatis Magmatic Suite. Stretching lineation trend dominantly SW–NE in the three mentioned units. On the basis of new mapping, neglecting local perturbations and deformation related to Tertiary extension, we infer the regional kinematics of Cretaceous syn-metamorphic thrusting and subsequent exhumation of the metamorphic units. Thrusting took place toward the SW (in present-day coordination) and the related fabrics are recorded throughout the metamorphic pile. On the contrary, exhumation-related fabrics are related to shear toward the NE and are preferentially recorded in the uppermost part of the metamorphic pile suggesting that extension was more localised and of less finite intensity compared to thrusting.
ISSN: 0040-1951

insu-01231485
https://hal-insu.archives-ouvertes.fr/insu-01231485
DOI : 10.1016/j.tecto.2015.09.034

Éditeur(s) : Université Nice Sophia Antipolis
Résumé : The Lesser Antilles is a case study of a very slow subduction (~2 cm/yr) of an old oceanic lithosphere (~84-100 Ma). The region presents a relatively low seismic activity, especially along the interplate contact, and the seismic hazard associated with a possible mega-thrust earthquake is still poorly known. This PhD thesis is a first step toward assessing the ability of the Lesser Antilles subduction zone to produce such a large subduction event. To do so, it aims at constraining the downdip width of the interplate's seismogenic zone. The lack of coverage of permanent seismological stations is a major limitation in the exploration of the Lesser Antilles subduction zone. It is due to the presence of only small aligned islands at far distances from the potentially seismogenic interplate area. Several oceanographic cruises were therefore planned that notably allowed the repeated deployment of ocean bottom seismometers; some of them being left for a few months of background seismicity recording. This thesis specifically focuses on two sets of wide-angle seismic data acquired offshore the Dominica and Martinique islands. From their analysis 3D and 2D tomographic models were produced respectively over the forearc region and across the whole subduction complex. These models constrain the plates' seismic structure as well as their geometry. They allow the discussion of how the imaged structures affect the subduction processes and give a first estimation of the downdip width of the seimogenic zone, defined as the segment of the interplate between the backstop and the upper plate's Moho. The joint interpretation of seismic models and earthquake localizations then refine this first assessment. Epicenter distribution from height months of seismic recording shows indeed that seismicity concentrates within the inner forearc region. The strong velocity gradient that characterize its basement suggests it is denser and more rigid than the more deformable outer forearc basement. The updip limit of the seismogenic zone could then lie arcward of the backstop at the contact of the interplate and the seaward end of the inner forearc crust. At depth, interplate earthquake mechanisms are observed between 35 and 45 km depth and interpreted to have occurred at the downdip limit of the seismogenic zone. The latter could reach a depth over 10,km deeper than the contact of the upper plate's Moho with the interplate, and therefore lie within the mantle wedge. All together, these results imply a large downdip width of the seismogenic zone (~70 km) offshore the Dominica and Martinique islands. Further work is, however, needed in order to fully comprehend the ability of the Lesser Antilles subduction zone to produce a possible mega-thrust earthquake. This would necessitate the evaluation of seismic coupling at the interplate contact and the possible segmentation of the seismogenic zone, for instance, due to the subduction of oceanic ridges.
Les Petites Antilles présentent un contexte géodynamique caractérisé par la subduction à très faible vitesse (~2 cm/an) d'une lithosphère océanique âgée (~84-100 Ma). L'activité sismique y est relativement faible, notamment à l'interplaque, où l'aléa sismique lié à un éventuel séisme de méga-chevauchement reste encore mal contraint. Cette thèse se veut être une première étape dans l'évaluation de la capacité de la zone de subduction des Petites Antilles à générer un tel évènement. Dans ce but, ces travaux tentent d'appréhender l'extension en profondeur du domaine sismogène de l'interplaque. Le manque de couverture des stations sismologiques permanentes est un inconvénient majeur dans l'exploration des Petites Antilles. Il s'explique en raison du peu de terres émergées et de leur éloignement de la zone potentiellement sismogène de l’interplaque. La région a donc fait l'objet de plusieurs campagnes océanographiques qui ont permis, notamment, le déploiement de sismomètres fond de mer (OBS); certains instruments étant restés immergés plusieurs mois afin de procéder à une écoute de la sismicité. Les travaux réalisés au cours de cette thèse se sont focalisés sur deux jeux de données de sismique grand-angle acquis au large des îles de la Dominique et de la Martinique. Leur analyse a permis la construction de modèles tomographiques 3D et 2D respectivement à l'échelle de l'avant-arc et de l'ensemble de la subduction. Ces modèles renseignent sur la structure sismique des plaques en convergence ainsi que sur leur géométrie. Ils permettent de discuter le rôle de la structure dans le fonctionnement de la subduction et d’obtenir une première estimation de l'extension en profondeur de la zone sismogène en considérant la portion de l'interplaque comprise entre le butoir et le Moho de la plaque supérieure. Dans un second temps, l'interprétation conjointe des modèles tomographiques et des localisations des séismes locaux a permis d'affiner cette estimation. Huit mois d'enregistrement de la sismicité montrent en effet une concentration des épicentres dans la région interne de l’avant-arc. Celle-ci présente un socle épais, à fort gradient de vitesse interprété comme plus dense et rigide que le socle de la région externe de l'avant-arc, plus déformable. La limite amont de la zone sismogène pourrait donc se situer en retrait de la position du butoir au contact de l'interplaque et de la limite entre ces deux zones de l'avant-arc. En profondeur, des mécanismes interplaques sont observés entre 35 et 45 km et interprétés comme des marqueurs de la limite aval de la zone sismogène. Cette dernière pourrait donc atteindre une profondeur jusqu'à 10 km supérieure à la limite précédemment évoquée et se trouver, par conséquent, au contact du manteau lithosphérique. L'ensemble de ces résultats suggèrent une extension en profondeur de la zone sismogène (i.e une largeur) de près de 70 km face aux îles de la Dominique et de la Martinique. Ces travaux doivent cependant être poursuivis afin d’évaluer pleinement la capacité de la zone de subduction des Petites Antilles à générer un éventuel séisme de méga-chevauchement. Le taux de couplage à l'interplaque doit être précisé ainsi que sa possible segmentation en lien, par exemple, avec à l'entrée en subduction des rides océaniques.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00172/28335/26628.pdf
http://archimer.ifremer.fr/doc/00172/28335/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The Mediterranean geodynamic system is an exceptional natural laboratory to study the complexities of back-arc extension during subduction rollback. Corsica is a key locality that recorded the Alpine subduction-collision history followed by 30 Ma of the Apennines slab rollback, responsible for the successive opening, from West to East, of the Liguro-Provençal basin and the Tyrrhenian Sea. The overall strain pattern of the Alpine metamorphic units of Alpine Corsica is studied through a synthesis of i) available geological maps, ii) geochronological data and iii) newly acquired structural data relative to successive events of ductile and brittle extension, Three main stages of extension are recorded: 1/ Syn-metamorphic Oligocene extension accommodated by N140° trending ductile shear zones, that correspond to the reactivation of a major Alpine thrust; 2/ Burdigalian ramp-flat extension with N60°-70° trending fault zones that controlled the deposition of onshore piggy-back basins (e.g. St Florent basin), and 3/ Serravalian N-S trending fault zones. From a geodynamical point of view, these successive extensional deformations in Alpine Corsica can be correlated to the history of the Apennines slab rollback. The two first stages are related to a southeastward rollback of the Appennines slab that successively triggered: 1/ Continental rifting in Oligocene leading to the opening of the Liguro-Provençal basin and 2/ Burdigalian extension with N60°-70° trending fault zone, oblique to the Alpine thrust that, after a counterclockwise rotation of the Corso-Sardinian block, became unable to accommodate extension. Finally, the third stage that gave NS-trending fault zones developed in Serravalian, at the onset of Tyrrhenian rifting, related to an eastward rollback of the Apennines slab, as a response of slab tearing in Sicily.
ISSN: 0040-1951

insu-01424859
https://hal-insu.archives-ouvertes.fr/insu-01424859
https://hal-insu.archives-ouvertes.fr/insu-01424859/document
https://hal-insu.archives-ouvertes.fr/insu-01424859/file/gueydan-tectonoph-2017.pdf
DOI : 10.1016/j.tecto.2016.12.028

Éditeur(s) : HAL CCSD
Résumé : National audience
Crustal-scale models for the Pyrenees based on ECORS reflection profileshave around 20 years now. In recent years, new understandingswere gained on the reconstruction to the preorogenic times, namelya scenario of extreme crustal attenuation and mantle exhumation ; inturn, this has implications on the interpretation of the present-day structure,as new models for the chain must consider feedbacks between themid-Cretaceous hyperextension and the Pyrenean inversion. On the WcentralPyrenean traverse, the southern part comprises 3 S-vergent basementthrust units, the Lakora, Gavarnie and Guarga units, flanked by thedetached cover of the Jaca piggyback basin and the Ebro basin, wherethe Mesozoic is thin and Late Cretaceous-Tertiary synorogenic carbonateand detrital sequences record a southward depocenter migration.To the N, the Chaînons Béarnais belt (CB) is a system of Jurassic to LowerCretaceous carbonate anticline ridges separated by synclines withthick Albian-Cenomanian flysch, covered to the north by Upper Cretaceousflysch sequences. The CB is thrust southwards together with theLakora thrust unit and northwards onto the Aquitaine basin. CB foldinglargely results from the rising and squeezing of diapirs initiated duringthe Jurassic-Early Cretaceous extension. Pieces of crust and mantle liftedin the diapirs attest that the CB derive from a Cretaceous domainof hyperextended continental crust and exhumed mantle. Moho reflectionsin the ECORS-Arzaq profile constrain the present deep structure.Restoration leads to a Mesozoic cover detachment over the N-Iberianand S-European margins. Inversion began by subduction of the exhumedmantle and folding and pop-up thrusting of the CB cover onto themargins. From the mid-late Eocene onwards, continental collision wasaccommodated by wedging and thrust stacking in the Iberian crust, involvingthe piggyback formation of S-vergent basement thrusts in theupper crust, and the northward subduction of the lower crust.
24 ème Réunion des sciences de la Terre 2014
Pau, France

insu-01080831
https://hal-insu.archives-ouvertes.fr/insu-01080831

Éditeur(s) : HAL CCSD Wiley-Blackwell
Résumé : International audience
The Alboran Domain, situated at the western end of the Mediterranean subductionsystem, is characterized by the Ronda Peridotites, one of the world largest exposures of subcontinental mantle. Using U-Pb (LA-ICP-MS) and Ar-Ar dating, we precisely dated twotectonic events associated with the Tertiary exhumation of the Ronda Peridotites. First,shearing along the Crust-Mantle Extensional Shear Zone caused, at ca. 22.5 Ma, mantleexhumation, local partial melting in the deep crust and coeval cooling in the upper crust.Second, the Ronda Peridotites Thrust triggered the final crustal emplacement of theperidotites onto the continental crust at ca. 21 Ma, as testified by granitic intrusions in thethrust hanging-wall. The tectonic evolution of the western Alboran Domain is thereforecharacterized by a fast switch from a continental lithosphere extension in a backarc setting,with sub-continental mantle exhumation, to a rift inversion by thrusting driven by shorteningof the subduction upper plate
ISSN: 0954-4879

insu-01441962
https://hal-insu.archives-ouvertes.fr/insu-01441962
https://hal-insu.archives-ouvertes.fr/insu-01441962/document
https://hal-insu.archives-ouvertes.fr/insu-01441962/file/Frasca-TerraNova-2017.pdf
DOI : 10.1111/ter.12255

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The Chalkidiki block is a major domain in the North Aegean that, contrary to other domains in the region, largely escaped thermal perturbations during Tertiary extension. As a result, the Chalkidiki block is an ideal candidate to glean information related to the timing of Mesozoic thermal events using appropriate geochronological techniques. We have undertaken a laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) study (U-Th-Pb on monazites and U-Pb on zircons) coupled with 40Ar/39Ar dating on nine samples from various structural levels within the thrust system of the Chalkidiki block. The eastern, and structurally lower part of the system revealed a complete isotopic reset of Carboniferous – Early Triassic monazites coeval with partial monazite destruction, REE-mobilisation and formation of apatite-allanite-epidote coronas at ~ 132 Ma, a reaction that is commonly observed in amphibolite-facies rocks. These coronas formed after crystallisation of garnet (i.e., at T > 580 °C) and, in all probability, either close to the peak-temperature conditions (~ 620 °C) on a prograde path or during retrogression between the peak-temperature and the low-temperature boundary of the amphibolite facies. Cooling of these rocks and arrival at mid-crustal levels occurred at 95–100 Ma. By contrast, the western, and structurally uppermost part of the system went through the same event by 120–125 Ma. Further structural considerations with respect to medium-temperature geochronology data imply that syn-metamorphic thrusting must have ceased by early Late Cretaceous. We emphasize that, with the sole exception of the Chalkidiki block, no pre-45 Ma medium-temperature geochronology data are preserved in other North Aegean domains, a feature that is clearly related to the extension-induced thermal perturbation of the region during the Tertiary.
ISSN: 0040-1951

insu-01329472
https://hal-insu.archives-ouvertes.fr/insu-01329472
https://hal-insu.archives-ouvertes.fr/insu-01329472/document
https://hal-insu.archives-ouvertes.fr/insu-01329472/file/kydonakis-tectono-2016.pdf
DOI : 10.1016/j.tecto.2016.06.006

Éditeur(s) : HAL CCSD
Résumé : International audience
High Pressure - Low Temperature (HP-LT) rocks testify for burying and exhumation of crustal material in subduction zones. The question of their exhumation is nevertheless still unclear. The Aegean domain offers several HP-LT belts. Especially, the Attic-Cycladic Blueschist unit (ACBU) is an example of a HP-LT unit exhumed in a convergent and then in a divergent context. It actually appears in metamorphic core complexes (MCCs) formed in the back-arc of the subduction. The syn-convergence "message" is however difficult to read because of the post-convergence structural and thermal overprint that accompanied the formation of the MCCs. Particularly, the geometry, the timing and the amount of the syn-orogenic exhumation remain unclear. We investigate theses questions with metamorphic petrology (Andros and Ios islands) and phengite population, single grain and in situ 40Ar-39Ar geochronology (Andros, Tinos, Syros and Ios islands). Based on these new constraints and a synthesis of published data, we are able to refine the geometry, the timing and the modes of the exhumation of the ACBU. Data from the whole Cyclades exhibit little differences in the age and P-T conditions at the successive stages of syn-orogenic exhumation. The peak of pressure (500±50 °C-18±1 kbar) has been reached at 50-55 Ma. The onset of the exhumation occurred at 40-45 Ma in blueschist facies conditions, between a basal thrust and a summital detachment. The following decompression was accompanied by cooling until 30-35 Ma (400±50 °C-8±1 kbar). At that time, the boundary conditions switched to extension. The change in boundary conditions is recorded by slowing of the exhumation and isobare heating. The conditions of post-orogenic exhumation differ from an island to another. The onset of post-orogenic exhumation is dated around 30 Ma in the northern Cyclades and 25 Ma in the southern Cyclades. It is related to top-to-the-North deformation in all the studied domain. The end of ductile deformation below the detachments is also diachronous (21 Ma in the North and 18 Ma in the South). Finally, we propose a model for the final steps of the exhumation related to the intrusion of granitic bodies around 14 Ma.
American Geophysical Union, Fall Meeting
San Francisco, United States

insu-00860510
https://hal-insu.archives-ouvertes.fr/insu-00860510
BIBCODE : 2010AGUFM.T23C2301L