TY - JOUR A1 - Jolivet, Laurent A1 - Faccenna, Claudio A1 - Huet, Benjamin A1 - Labrousse, Loic A1 - Le Pourhiet, Laetitia A1 - Lacombe, Olivier A1 - Lecomte, Emmanuel A1 - Burov, Evguenii A1 - Denele, Yoann A1 - Brun, Jean-Pierre A1 - Philippon, Melody A1 - Paul, Anne A1 - Salaue, Gwenaelle A1 - Karabulut, Hayrullah A1 - Piromallo, Claudia A1 - Monie, Patrick A1 - Gueydan, Frederic A1 - Okay, Aral I. A1 - Oberhänsli, Roland A1 - Pourteau, Amaury A1 - Augier, Romain A1 - Gadenne, Leslie A1 - Driussi, Olivier T1 - Aegean tectonics strain localisation, slab tearing and trench retreat JF - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth N2 - We review the geodynamic evolution of the Aegean-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 (I) 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 strip 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). KW - Backarc extension KW - Slab retreat KW - Asthenospheric flow KW - Strain localisation KW - Aegean Sea KW - Metamorphic core complex Y1 - 2013 U6 - https://doi.org/10.1016/j.tecto.2012.06.011 SN - 0040-1951 VL - 597 SP - 1 EP - 33 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Pourteau, Amaury A1 - Sudo, Masafumi A1 - Candan, Osman A1 - Lanari, P. A1 - Vidal, O. A1 - Oberhänsli, Roland T1 - Neotethys closure history of Anatolia - insights from Ar-40-Ar-39 geochronology and P-T estimation in high-pressure metasedimentary rocks JF - Journal of metamorphic geology N2 - The multiple high-pressure (HP), low-temperature (LT) metamorphic units of Western and Central Anatolia offer a great opportunity to investigate the subduction-and continental accretion-related evolution of the eastern limb of the long-lived Aegean subduction system. Recent reports of the HP-LT index mineral Fe-Mg-carpholite in three metasedimentary units of the Gondwana-derived Anatolide-Tauride continental block (namely the Afyon Zone, the Oren Unit and the southern Menderes Massif) suggest a more complicated scenario than the single-continental accretion model generally put forward in previous studies. This study presents the first isotopic dates (white mica Ar-40-Ar-39 geochronology), and where possible are combined with P-T estimates (chlorite thermometry, phengite barometry, multi-equilibrium thermobarometry), on carpholite-bearing rocks from these three HP-LT metasedimentary units. It is shown that, in the Afyon Zone, carpholite-bearing assemblages were retrogressed through greenschist-facies conditions at c. 67-62 Ma. Early retrograde stages in the Oren Unit are dated to 63-59 Ma. In the Kurudere-Nebiler Unit (HP Mesozoic cover of the southern Menderes Massif), HP retrograde stages are dated to c. 45 Ma, and post-collisional cooling to c. 26 Ma. These new results support that the Oren Unit represents the westernmost continuation of the Afyon Zone, whereas the Kurudere-Nebiler Unit correlates with the Cycladic Blueschist Unit of the Aegean Domain. In Western Anatolia, three successive HP-LT metamorphic belts thus formed: the northernmost Tavsanli Zone (c. 88-82 Ma), the Oren-Afyon Zone (between 70 and 65 Ma), and the Kurudere-Nebiler Unit (c. 52-45 Ma). The southward younging trend of the HP-LT metamorphism from the upper and internal to the deeper and more external structural units, as in the Aegean Domain, points to the persistence of subduction in Western Anatolia between 93-90 and c. 35 Ma. After the accretion of the Menderes-Tauride terrane, in Eocene times, subduction stopped, leading to continental collision and associated Barrovian-type metamorphism. Because, by contrast, the Aegean subduction did remain active due to slab roll-back and trench migration, the eastern limb (below Southwestern Anatolia) of the Hellenic slab was dramatically curved and consequently teared. It therefore is suggested that the possibility for subduction to continue after the accretion of buoyant (e.g. continental) terranes probably depends much on palaeogeography. KW - Ar-40-Ar-39 geochronology KW - Anatolia KW - chlorite-phengite thermobarometry KW - high-pressure metasedimentary rocks Y1 - 2013 U6 - https://doi.org/10.1111/jmg.12034 SN - 0263-4929 SN - 1525-1314 VL - 31 IS - 6 SP - 585 EP - 606 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Omrani, H. A1 - Moazzen, Mohssen A1 - Oberhänsli, Roland A1 - Tsujimori, T. A1 - Bousquet, Romain A1 - Moayyed, M. T1 - Metamorphic history of glaucophane-paragonite-zoisite eclogites from the Shanderman area, northern Iran JF - Journal of metamorphic geology N2 - The Shanderman eclogites and related metamorphosed oceanic rocks mark the site of closure of the Palaeotethys ocean in northern Iran. The protolith of the eclogites was an oceanic tholeiitic basalt with MORB composition. Eclogite occurs within a serpentinite matrix, accompanied by mafic rocks resembling a dismembered ophiolite. The eclogitic mafic rocks record different stages of metamorphism during subduction and exhumation. Minerals formed during the prograde stages are preserved as inclusions in peak metamorphic garnet and omphacite. The rocks experienced blueschist facies metamorphism on their prograde path and were metamorphosed in eclogite facies at the peak of metamorphism. The peak metamorphic mineral paragenesis of the rocks is omphacite, garnet (pyrope-rich), glaucophane, paragonite, zoisite and rutile. Based on textural relations, post-peak stages can be divided into amphibolite and greenschist facies. Pressure and temperature estimates for eclogite facies minerals (peak of metamorphism) indicate 15-20kbar at similar to 600 degrees C. The pre-peak blueschist facies assemblage yields <11kbar and 400-460 degrees C. The average pressure and temperature of the post-peak amphibolite stage was 5-6kbar, similar to 470 degrees C. The Shanderman eclogites were formed by subduction of Palaeotethys oceanic crust to a depth of no more than 75km. Subduction was followed by collision between the Central Iran and Turan blocks, and then exhumation of the high pressure rocks in northern Iran. KW - eclogite KW - late Palaeozoic KW - North Iran KW - Palaeotethys KW - P-T path KW - Shanderman Y1 - 2013 U6 - https://doi.org/10.1111/jmg.12045 SN - 0263-4929 VL - 31 IS - 8 SP - 791 EP - 812 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Sodoudi, Forough A1 - Yuan, Xiaohui A1 - Kind, Rainer A1 - Lebedev, Sergei A1 - Adam, Joanne M-C. A1 - Kästle, Emanuel A1 - Tilmann, Frederik T1 - Seismic evidence for stratification in composition and anisotropic fabric within the thick lithosphere of Kalahari Craton JF - Geochemistry, geophysics, geosystems N2 - Based on joint consideration of S receiver functions and surface-wave anisotropy we present evidence for the existence of a thick and layered lithosphere beneath the Kalahari Craton. Our results show that frozen-in anisotropy and compositional changes can generate sharp Mid-Lithospheric Discontinuities (MLD) at depths of 85 and 150-200 km, respectively. We found that a 50 km thick anisotropic layer, containing 3% S wave anisotropy and with a fast-velocity axis different from that in the layer beneath, can account for the first MLD at about 85 km depth. Significant correlation between the depths of an apparent boundary separating the depleted and metasomatised lithosphere, as inferred from chemical tomography, and those of our second MLD led us to characterize it as a compositional boundary, most likely due to the modification of the cratonic mantle lithosphere by magma infiltration. The deepening of this boundary from 150 to 200 km is spatially correlated with the surficial expression of the Thabazimbi-Murchison Lineament (TML), implying that the TML isolates the lithosphere of the Limpopo terrane from that of the ancient Kaapvaal terrane. The largest velocity contrast (3.6-4.7%) is observed at a boundary located at depths of 260-280 km beneath the Archean domains and the older Proterozoic belt. This boundary most likely represents the lithosphere-asthenosphere boundary, which shallows to about 200 km beneath the younger Proterozoic belt. Thus, the Kalahari lithosphere may have survived multiple episodes of intense magmatism and collisional rifting during the billions of years of its history, which left their imprint in its internal layering. KW - lithospheric layering KW - S receiver functions Y1 - 2013 U6 - https://doi.org/10.1002/2013GC004955 SN - 1525-2027 VL - 14 IS - 12 SP - 5393 EP - 5412 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Mechie, James A1 - Ben-Avraham, Zvi A1 - Weber, Michael H. A1 - Götze, Hans-Jürgen A1 - Koulakov, Ivan A1 - Mohsen, A. A1 - Stiller, M. T1 - The distribution of Moho depths beneath the Arabian plate and margins JF - TECTONOPHYSICS N2 - In this study three new maps of Moho depths beneath the Arabian plate and margins are presented. The first map is based on the combined gravity model, EIGEN 06C, which includes data from satellite missions and ground-based studies, and thus covers the whole region between 31 degrees E and 60 inverted perpendicular E and between 12 degrees N and 36 degrees N. The second map is based on seismological and ground-based gravity data while the third map is based only on seismological data. Both these maps show gaps due to lack of data coverage especially in the interior of the Arabian plate. Beneath the interior of the Arabian plate the Moho lies between 32 and 45 km depth below sea level. There is a tendency for higher Pn and Sn velocities beneath the northeastern parts of the plate interior with respect to the southwestern parts of the plate interior. Across the northern, destructive margin with the Eurasian plate, the Moho depths increase to over 50 km beneath the Zagros mountains. Across the conservative western margin, the Dead Sea Transform (DST). Moho depths decrease from almost 40 km beneath the highlands east of the DST to about 21-23 km under the southeastern Mediterranean Sea. This decrease seems to be modulated by a slight depression in the Moho beneath the southern DST. The constructive southwestern and southeastern margins of the Arabian plate also show the Moho shallowing from the plate interior towards the plate boundaries. A comparison of the abruptness of the Moho shallowing between the margins of the Arabian plate, the conjugate African margin at 26 degrees N and several Atlantic margins shows a complex picture and suggests that the abruptness of the Moho shallowing may reflect fundamental differences in the original structure of the margins. (C) 2012 Elsevier B.V. All rights reserved. KW - Moho depths KW - Arabian plate KW - Red Sea KW - Velocity models KW - Receiver functions KW - Satellite gravity data Y1 - 2013 U6 - https://doi.org/10.1016/j.tecto.2012.11.015 SN - 0040-1951 SN - 1879-3266 VL - 609 SP - 234 EP - 249 PB - ELSEVIER SCIENCE BV CY - AMSTERDAM ER -