Éditeur(s) : Wiley / Blackwell
Résumé : P>New seismic reflection data from the Grand Banks of Newfoundland and the Newfoundland Basin add to the growing knowledge of the composition, structure and history of this non-volcanic margin. Geophysical imaging is now approaching the extent of that done previously on the conjugate margin along Iberia, providing a valuable database for the development of rifting models. Two parallel profiles over the shelf platform image deep crustal fabric representing Precambrian or possibly Appalachian deformation as well as Mesozoic extension. Progressively more intense extension of continental crust is imaged oceanwards without the highly reflective detachments frequently seen on profiles off Galicia. A landward-dipping event 'L' is imaged sporadically and appears to be analogous to a similar event on the Iberian IAM9 profile. The transition zone is probably exposed serpentinized mantle as interpreted off the Iberian margin although there appears to be a difference in the character of ridge development and reflectivity. The distinctive 'U' reflection identified previously at the base of the Newfoundland Basin deep water sedimentary section and recently identified as one or more thin basalt sills is imaged on newly presented profiles that connect previously published profiles SCR3 and SCR2 showing that 'U' is highly regular and continuous except where interrupted by basement highs. 'U' is also seen to have a major impact on the ability to image underlying basement. A full transect beginning over completely unextended continental crust through to oceanic crust has provided a data set from which estimates of extension and the pre-rifting location of the present continental edge can be made. Two estimates were obtained; 85 km based on faulting and 120 km based on crustal thickness.
Geophysical Journal International (0956-540X) (Wiley / Blackwell), 2009-08 , Vol. 178 , N. 2 , P. 1004-1020

Droits : 2009 Wiley / Blackwell
http://archimer.ifremer.fr/doc/2009/publication-6919.pdf
DOI:10.1111/j.1365-246X.2009.04162.x
http://archimer.ifremer.fr/doc/00000/6919/

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 American Geophysical Union (AGU)
Résumé : International audience
The nucleation, propagation, and associated folding of ramp-flat-ramp normal faults were analyzed from field examples developed in a brittle/ductile multilayer sequence of the Huércal-Overa Basin (SE Spain). Gently dipping sandy silt layers, which display a low cohesive strength (C0 = 7 kPa, μ = 34°), favor the development of extensional detachments. A tectonic origin instead of a possible gravitational origin is supported by the perpendicularity between the paleoslope direction of the fluvial-deltaic environment inferred from imbricated pebbles, and the senses of movement deduced from fault slicken-lines. The link between high-angle normal faults (HANFs) --formed at different levels in the layered sequence-- with horizontal fault segments comes to develop ramp-flat-ramp normal faults with associated roll-over in the hanging wall. Observed extensional duplexes are formed by parallel detachments connected through synthetic Riedel faults. These Riedel faults would produce the back-rotation of the individual blocks (horses), i.e., extensional folding of the originally subhorizontal layers. There is no correlation between the analyzed ramp-flat-ramp normal faults, accommodating south-southeastward extension during Serravallian-lower Tortonian, and either the regional Alpujarride/Nevado-Filabride west-directed extensional shear zone or the top-to-the-north detachments within Alpujarride units, which are clearly sealed by Serravallian-lower Tortonian sediments. Therefore, the studied normal faults are restricted to the brittle/ductile multilayer fluvio/deltaic sequence and accommodate moderate late extension instead of belonging to a large crustal extensional system connected with a regional detachment at depth. Therefore, the basin formed in a moderate crustal thickness context where small and medium-scale extensional systems were subordinate structures. These natural examples support the development of low-angle normal faults at very shallow crustal levels in multilayer sequences with suitable rheological conditions.
ISSN: 0278-7407

hal-00750352
https://hal.archives-ouvertes.fr/hal-00750352
DOI : 10.1029/2012TC003130

Éditeur(s) : HAL CCSD
Résumé : The northern Mirdita ophiolite massifs in Albanian Dinarides formed at a slow-spreading ridge, active during the Jurassic (160–165 Ma). They share a common horizontal Jurassic–Lower Cretaceous sedimentary cover showing that they were not deeply and intrinsically affected by later Alpine thrusting. The western massifs of Mirdita, first oceanic core complex (OCC) and detachment shear zone described in ophiolites, compare with OCCs in slow-spreading ridges and provide continuous exposure of the deep internal structure of this system, revealing its kinematics, thanks to detailed structural mapping in peridotites and gabbros. The Mirdita detachments root in the Moho transition zone (MTZ), a weak zone at the top of asthenospheric mantle, where basaltic melts impregnate dunites. The OCC domes are plagioclase-amphibole–bearing mylonitic peridotites, ∼400 m thick, grading downward within 200 m to harzburgitic mantle. The mylonitic detachments crossed Moho beneath a NNE-SSW–trending ridge. On the western side of OCC domes, the hanging wall of the ridge, crustal gabbros, and basalts are still preserved, despite being deeply affected by hydrothermal alteration. From there, the partially molten MTZ was detached as a shear zone, mixing with lower gabbros. The OCC emerged, migrating upsection and eastward over 5 km. Finally, the OCC front is observed in hornblende-rich syntectonic mylonites derived from upper gabbros and from the overlying former lid. Serpentinization is static within these mylonites. A low-temperature detachment fault is expressed as a sheared antigoritic mélange at the margin of the mylonitic shear zone. Asthenospheric flow in the harzburgitic mantle beneath the ridge of origin has been preserved below the OCC rooting. The dominant asthenospheric flow direction trends parallel to the ridge axis. This mantle flow rotates over 200 m into the low-temperature mylonitic detachments, where OCC motion turns transversal to the ridge. Crystal preferred orientation measurements on six samples point to brown hornblende crystal growth during mylonitic flow and illustrate the change of olivine intra-crystalline slip system in mylonites compared to porphyroclastic harzburgite.
ISSN: 1553-040X

hal-01504440
https://hal.archives-ouvertes.fr/hal-01504440
DOI : 10.1130/GES01383.1

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The identification of the structures and deformation patterns in magma-poor continental rifted margins is essential to characterize the processes of continental lithosphere necking. Brittle faults, often termed mantle detachments, are believed to play an essential role in the rifting processes that lead to mantle exhumation. However, ductile shear zones in the deep crust and mantle are rarely identified and their mechanical role remains to be established. The western Betics (Southern Spain) provides an exceptional exposure of a strongly thinned continental lithosphere, formed in a supra-subduction setting during Oligocene-Lower Miocene. A full section of the entire crust and the upper part of the mantle is investigated. Variations in crustal thickness are used to quantify crustal stretching that may reach values larger than 2000% where the ductile crust almost disappear, defining a stage of hyper-stretching. Opposite senses of shear top-to-W and top-to-E are observed in two extensional shear zones located close to the crust-mantle boundary and along the brittle-ductile transition in the crust, respectively. At locations where the ductile crust almost disappears, concordant top-to-E-NE senses of shear are observed in both upper crust and serpentinized mantle. Late high-angle normal faults with ages of ca. 21 Ma or older (40Ar/39Ar on white mica) crosscut the previously hyper-stretched domain, involving both crust and mantle in tilted blocks. The western Betics exemplifies, probably better than any previous field example, the changes in deformation processes that accommodate the progressive necking of a continental lithosphere. Three successive steps can be identified: i/a mid-crustal shear zone and a crust-mantle shear zone, acting synchronously but with opposite senses of shear, accommodate ductile crust thinning and ascent of subcontinental mantle; ii/hyper-stretching localizes in the neck, leading to an almost disappearance of the ductile crust and bringing the upper crust in contact with the subcontinental mantle, each of them with their already acquired opposite senses of shear; and iii/high-angle normal faulting, cutting through the Moho, with related block tilting, ends the full exhumation of the mantle in the zone of localized stretching. The presence of a high strength sub-Moho mantle is responsible for the change in sense of shear with depth. Whereas mantle exhumation in the western Betics occurred in a backarc setting, this deformation pattern controlled by a high-strength layer at the top of the lithosphere mantle makes it directly comparable to most passive margins whose formation lead to mantle exhumation. This unique field analogue has therefore a strong potential for the seismic interpretation of the so-called “hyper-extended margins”.
ISSN: 0264-8172

insu-01310895
https://hal-insu.archives-ouvertes.fr/insu-01310895
https://hal-insu.archives-ouvertes.fr/insu-01310895/document
https://hal-insu.archives-ouvertes.fr/insu-01310895/file/Frasca-MarPetGeol-2016.pdf
DOI : 10.1016/j.marpetgeo.2016.04.020

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

Éditeur(s) : HAL CCSD AGU and the Geochemical Society
Résumé : International audience
New magnetotelluric and receiver transfer function studies provide insights from the upper to the lower crust of the eastern Betic Cordillera, which is deformed by large folds, normal faults, and a major transcurrent left-lateral fault, the Carboneras Fault Zone (CFZ). Receiver function analysis determines a NNW dipping Moho reaching 20 degrees that increases in depth, from 20 km south of the CFZ up to 34 km in the Sierra de Los Filabres. In addition, seismic discontinuities determined in the upper crust are interpreted as major contacts between metamorphic complexes that are detached and folded. The MT inversion model reveals a conductive zone, also representing a crustal seismic discontinuity, associated with the Alpujarride/Nevado-Filabride contact and fitting the N vergent geometry of the Sierra Alhamilla antiform. A small flexure at Moho coincides with the CFZ, as revealed by the Bouguer anomaly trend, in agreement with the receiver function results. Moreover, the Bahr strike and tipper angle at the stations placed closest to the CFZ clearly reveal the continuity of the CFZ at least down to approximately 15 km in depth, crossing all the detected crustal discontinuities up to the Moho. The lack of a clear Moho offset associated with the Carboneras Fault supports the idea that some large strike-slip faults tend to accommodate the deformation by a broadening fault zone at lower crustal levels. Its nucleation could occur at the base of a thin crust, where melting processes critically reduced the lithospheric strength during the late Miocene, to then propagate upward, reaching the topographic surface. Northward, the lithosphere comprised moderately larger strength, and the crustal discontinuities favored the development of larger folds with kilometric amplitude instead of strike-slip faults since the late Miocene.
ISSN: 1525-2027

hal-00671024
https://hal.archives-ouvertes.fr/hal-00671024
DOI : 10.1029/2010GC003274

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

Éditeur(s) : HAL CCSD
Résumé : International audience
Two opposing visions of the Aegean backarc tectonics implicitly contain contrasting images of the rheological behaviour of the lihosphere, supported by different sets of observations. The propagation of the NAF and extension in the Corinth Rift suggest a strongly localising rheology whereas the formation of MCC in the Cyclades and the Rhodope suggests instead a more viscous behaviour. This paradox was the seminal question addressed by the ANR-EGEO programme (2007-2010) that leads to the following conclusions: (1) The exhumation of the Cycladic MCC's is accommodated by the N-dipping North Cycladic Detachment System (NCDS) that partly reworks the Vardar suture and at the base by a series of thrusts, including the basal contact of the Cycladic Blueschists (CBS) over the Cycladic Basement (CB). The activity of LANF is due to the reactivation of pre-existing discontinuities such as thrusts or earlier detachments and much less to the interaction with granitic plutons. (2) Exhumation in the Cyclades has proceeded in two stages: (a) Eocene syn-orogenic exhumation within the subduction lower/upperplate interface while the post-orogenic Rhodope MCC formed further north, (b) Oligo-Miocene post-orogenic extension in an MCC mode coeval with syn-orogenic exhumation in Crete and the Peloponnese. (3) Both stages were associated with slab retreat, as early as the Eocene with an acceleration at 30-35 Ma. (4) The localisation of the presently active steeply-dipping normal faults on the southern margin of the Corinth Rift may have been preceded by a partial reworking of thrusts and syn-orogenic detachments by shallow-dipping decollements. (5) The localisation of the NAF in the Marmara Sea region and the Northern Aegean Sea is now accurately dated between 5.3 and 5 Ma Ma using the erosion and deposition surfaces that mark the Messinian salinity Crisis and nannofossils ages. (6) The formation of MCCs in the Cyclades resulted in the draining of the low viscosity lower crust from the northern Aegean Sea and led to an easier coupling between upper mantle and upper crust, easing the localisation and propagation of the NAF. (7) A comparison between crustal and mantle finite strain suggests that mantle flow due to slab retreat controls the stretching of the crust. Our model involves progressive slab retreat and mantle flow below the overriding plate inducing the observed succession of tectonic episodes with a progressive localisation of extension due to several slab tearing events. There is no paradox in the tectonic history and rheological behaviour of the Aegean lithosphere but an evolution of the kinematic boundary conditions due to slab deformation at depth.
American Geophysical Union
San Francisco, United States

insu-00860518
https://hal-insu.archives-ouvertes.fr/insu-00860518
BIBCODE : 2010AGUFM.T13G..04J

Éditeur(s) : HAL CCSD Cambridge University Press (CUP)
Résumé : International audience
Andros is a key island for understanding both the timing of high-pressure–low-temperature(HP-LT) metamorphism and the dynamics of crustal-scale detachment systems exhuming high-gradeunits in the Cyclades (Greece). Using phengite 40Ar–39Ar geochronology coupled with thermobarometry,as well as data from literature, we constrain the pressure–temperature–time (P-T-t) paths of theMakrotantalon and Attic–Cycladic Blueschist units on Andros. Peak conditions of the HP-LT episodein the Makrotantalon unit are 550 °C and 18.5 kbar, dated at 116 Ma. We correlate this episode withEarly Cretaceous blueschist facies metamorphism recognized in the Pelagonian zone of continentalGreece. This is a new argument favouring a Pelagonian origin for the Makrotantalon unit. In the Attic–Cycladic Blueschist unit, the P-T-t path is characterized by: (1) exhumation after peak conditions inHP-LT conditions between 55 and 35 Ma; (2) isobaric heating at 7 kbar until 30 Ma; and (3) isothermaldecompression until 21 Ma. This thermal evolution and timing are similar to those of the neighbouringTinos Island, emphasizing major thermal re-equilibration at the transition between stable and retreatingsubduction. Modifications of the crustal thermal state played a major role in the evolution of the NorthCycladic Detachment System, below which Andros HP-LT units were exhumed.
ISSN: 0016-7568

insu-01114909
https://hal-insu.archives-ouvertes.fr/insu-01114909
DOI : 10.1017/S0016756814000661

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
This paper provides a synthesis of current data and interpretations on the crustal structure of the Pyrenean-Cantabrian orogenic belt, and presents new tectonic models for representative transects. The Pyrenean orogeny lasted from Santonian (~84 Ma) to early Miocene times (~20 Ma), and consisted of a spatial and temporal succession of oceanic crust/exhumed mantle subduction, rift inversion and continental collision processes at the Iberia-Eurasia plate boundary. A good coverage by active-source (vertical-incidence and wide-angle reflection) and passive-source (receiver functions) seismic studies, coupled with surface data have led to a reasonable knowledge of the present-day crustal architecture of the Pyrenean-Cantabrian belt, although questions remain. Seismic imaging reveals a persistent structure, from the central Pyrenees to the central Cantabrian Mountains, consisting of a wedge of Eurasian lithosphere indented into the thicker Iberian plate, whose lower crust is detached and plunges northwards into the mantle. For the Pyrenees, a new scheme of relationships between the southern upper crustal thrust sheets and the Axial Zone is here proposed. For the Cantabrian belt, the depth reached by the N-dipping Iberian crust and the structure of the margin are also revised.The common occurrence of lherzolite bodies in the northern Pyrenees and the seismic velocity and potential field record of the Bay of Biscay indicate that the precursor of the Pyrenees was a hyperextended and strongly segmented rift system, where narrow domains of exhumed mantle separated the thinned Iberian and Eurasian continental margins since the Albian-Cenomanian. The exhumed mantle in the Pyrenean rift was largely covered by a Mesozoic sedimentary lid that had locally glided along detachments in Triassic evaporites. Continental margin collision in the Pyrenees was preceded by subduction of the exhumed mantle, accompanied by the pop-up thrust expulsion of the off-scraped sedimentary lid above. To the west, oceanic subduction of the Bay of Biscay under the North Iberian margin is supported by an upper plate thrust wedge, gravity and magnetic anomalies, and 3D inclined sub-crustal reflections. However, discrepancies remain for the location of continent-ocean transitions in the Bay of Biscay and for the extent of oceanic subduction. The plate-kinematic evolution during the Mesozoic, which involves issues as the timing and total amount of opening, as well as the role of strike-slip drift, is also under debate, discrepancies arising from first-order interpretations of the adjacent oceanic magnetic anomaly record.
ISSN: 0040-1951

insu-01683989
https://hal-insu.archives-ouvertes.fr/insu-01683989
https://hal-insu.archives-ouvertes.fr/insu-01683989/document
https://hal-insu.archives-ouvertes.fr/insu-01683989/file/teixell-tectono-2018.pdf
DOI : 10.1016/j.tecto.2018.01.009

Éditeur(s) : HAL CCSD AGU and the Geochemical Society
Résumé : International audience
A NE-SW magnetotelluric 110 km-long profile including 18 sites was acquired across the western Rif Cordillera along the Eurasian-African plate boundary, allowing to constrain its poorly known deep structure. It extends from the Internal Zones, close to the Alboran coast, crossing the External Zones and up to the Gharb foreland basin. The periods recorded range from 0.001 s to 1000 s. The combination of magnetotelluric data with available geological data provides new insight regarding the relationship between deep and shallow crustal structures of the Rif Cordillera. Analyses of structural dimensionality suggest a preferential NW-SE direction, and a 2D joint inversion was performed. A 3D inversion extending the 2D model along the strike confirmed the reliability of this approach. The magnetotelluric model shows a heterogeneous upper crust in agreement with the geological structures observed at surface. The Internal Zones correspond to resistive (metamorphic rocks) and conductive (peridotites) bodies, while the External Zones and the foreland basin are characterized by large conductive bodies of variable thickness. A crustal detachment level separating shallow geological units from a probable variscan basement was inferred. At depth, the most relevant feature consists of large resistive bodies with a shallow irregular top, located below the frontal part of the Rif. The outcrops of exotic metapelitic, granitic and gneissic blocks in the frontal part of the Cordillera suggest that these large resistive bodies may correspond to a gneissic or granitic basement surrounded by metapelitic rocks. Late contractive thrust and diapiric processes were responsible for their uplift and shallow emplacement. The Rif constitutes an active southwestward vergent orogenic wedge, oblique to the present-day NW-SE convergent Eurasian-African plate boundary.
ISSN: 1525-2027

hal-00670999
https://hal.archives-ouvertes.fr/hal-00670999
DOI : 10.1029/2011GC003783

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : This study focuses on the petrology, geochronology and thermochronology of metamorphic rocks within the northern Menderes Massif in western Turkey. Metasediments belonging to the cover series of the Massif record pervasive amphibolite-facies metamorphism culminating at ca. 625–670 °C and 7–9 kbars. U–Th–Pb in situ ages on monazite and allanite from these metapelites record crustal thickening and nappe stacking associated with the internal imbrication of the Anatolide–Taurides platform during the Eocene. In addition, new 39Ar/40Ar single muscovite grain analyses on deformed rocks were performed in three localities within the northern Menderes Massif and ages range from 19.8 to 25.5 Ma. These mylonites may be related to both well-known detachments, Simav to the north and Alaşehir to the south, which accommodate Oligo–Miocene exhumation of the Menderes core complex. U–Th–Pb data on monazite grains (22.2 ± 0.2 Ma) from migmatites emplaced within the Simav detachment confirm these ages.
ISSN: 1437-3254

hal-01355967
https://hal.archives-ouvertes.fr/hal-01355967
DOI : 10.1007/s00531-015-1271-2