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Philippe Agard - One of the best experts on this subject based on the ideXlab platform.
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zagros orogeny a subduction dominated process
Geological Magazine, 2011Co-Authors: Philippe Agard, Jafar Omrani, Laurent Jolivet, Hubert Whitechurch, Bruno Vrielynck, Wim Spakman, Patrick Monie, Bertrand Meyer, Rinus WortelAbstract:This paper presents a synthetic view of the geodynamic evolution of the Zagros orogen within the frame of the Arabia–Eurasia collision. The Zagros orogen and the Iranian plateau preserve a record of the long-standing Convergence History between Eurasia and Arabia across the Neo-Tethys, from subduction/obduction processes to present-day collision (from ~ 150 to 0 Ma). We herein combine the results obtained on several geodynamic issues, namely the location of the oceanic suture zone, the age of oceanic closure and collision, the magmatic and geochemical evolution of the Eurasian upper plate during Convergence (as testified by the successive Sanandaj–Sirjan, Kermanshah and Urumieh–Dokhtar magmatic arcs), the P–T–t History of the few Zagros blueschists, the Convergence characteristics across the Neo-Tethys (kinematic velocities, tomographic constraints, subduction zones and obduction processes), together with a survey of recent results gathered by others. We provide lithospheric-scale reconstructions of the Zagros orogen from ~ 150 to 0 Ma across two SW–NE transects. The evolution of the Zagros orogen is also compared to those of the nearby Turkish and Himalayan orogens. In our geotectonic scenario for the Zagros Convergence, we outline three main periods/regimes: (1) the Mid to Late Cretaceous (115–85 Ma) corresponds to a distinctive period of perturbation of subduction processes and interplate mechanical coupling marked by blueschist exhumation and upper-plate fragmentation, (2) the Paleocene–Eocene (60–40 Ma) witnesses slab break-off, major shifts in arc magmatism and distributed extension within the upper plate, and (3) from the Oligocene onwards (~ 30–0 Ma), collision develops with a progressive SW migration of deformation and topographic build-up (Sanandaj–Sirjan Zone: 20–15 Ma, High Zagros: ~12–8 Ma; Simply Folded Belt: 5–0 Ma) and with partial slab tear at depths (~10 Ma to present). Our reconstructions underline the key role played by subduction throughout the whole Convergence History. We finally stress that such a long-lasting subduction system with changing boundary conditions also makes the Zagros orogen an ideal natural laboratory for subduction processes.
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Convergence History across Zagros (Iran): constraints from collisional and earlier deformation
International Journal of Earth Sciences, 2005Co-Authors: Philippe Agard, Jafar Omrani, Laurent Jolivet, Frederic MouthereauAbstract:The Zagros orogen provides a unique opportunity within the Alpine system to evaluate the interplay between a young Tertiary collision and earlier subduction/obduction processes. Within the Crush zone and the Sanandaj–Sirjan (internal) zone separating the Zagros Fold belt from Central Iran, we document several major tectonic events taking place at the end of the Cretaceous, of the Eocene and from the Mio–Pliocene onwards (ca.
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Convergence History across zagros iran constraints from collisional and earlier deformation
International Journal of Earth Sciences, 2005Co-Authors: Philippe Agard, Jafar Omrani, Laurent Jolivet, Frederic MouthereauAbstract:The Zagros orogen provides a unique opportunity within the Alpine system to evaluate the interplay between a young Tertiary collision and earlier subduction/obduction processes. Within the Crush zone and the Sanandaj–Sirjan (internal) zone separating the Zagros Fold belt from Central Iran, we document several major tectonic events taking place at the end of the Cretaceous, of the Eocene and from the Mio–Pliocene onwards (ca. <20–15 Ma). Contrary to recent interpretations, our data (cross-sections and description of the overall deformation style) strongly suggest that the Main Zagros Thrust (MZT) is deeply rooted, possibly to Moho depths, and that the suture zone effectively runs along the MZT. Field observations show that the final resorption of the oceanic domain took place slightly after 35 Ma and that collision must have started before ca. 23–25 Ma in northern Zagros. The shortening rate across the Crush zone since the Mid-Miocene (20–15 Ma) is estimated at a minimum 3–4 mm/year. Shear movements in the Crush zone during the Eocene–Oligocene period and extensional/strike-slip movements in the internal zones during the late Cretaceous point to an oblique setting early in the Convergence History. A geotectonic scenario for Convergence from the time of obduction to the present is finally proposed.
Frederic Mouthereau - One of the best experts on this subject based on the ideXlab platform.
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Convergence History across Zagros (Iran): constraints from collisional and earlier deformation
International Journal of Earth Sciences, 2005Co-Authors: Philippe Agard, Jafar Omrani, Laurent Jolivet, Frederic MouthereauAbstract:The Zagros orogen provides a unique opportunity within the Alpine system to evaluate the interplay between a young Tertiary collision and earlier subduction/obduction processes. Within the Crush zone and the Sanandaj–Sirjan (internal) zone separating the Zagros Fold belt from Central Iran, we document several major tectonic events taking place at the end of the Cretaceous, of the Eocene and from the Mio–Pliocene onwards (ca.
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Convergence History across zagros iran constraints from collisional and earlier deformation
International Journal of Earth Sciences, 2005Co-Authors: Philippe Agard, Jafar Omrani, Laurent Jolivet, Frederic MouthereauAbstract:The Zagros orogen provides a unique opportunity within the Alpine system to evaluate the interplay between a young Tertiary collision and earlier subduction/obduction processes. Within the Crush zone and the Sanandaj–Sirjan (internal) zone separating the Zagros Fold belt from Central Iran, we document several major tectonic events taking place at the end of the Cretaceous, of the Eocene and from the Mio–Pliocene onwards (ca. <20–15 Ma). Contrary to recent interpretations, our data (cross-sections and description of the overall deformation style) strongly suggest that the Main Zagros Thrust (MZT) is deeply rooted, possibly to Moho depths, and that the suture zone effectively runs along the MZT. Field observations show that the final resorption of the oceanic domain took place slightly after 35 Ma and that collision must have started before ca. 23–25 Ma in northern Zagros. The shortening rate across the Crush zone since the Mid-Miocene (20–15 Ma) is estimated at a minimum 3–4 mm/year. Shear movements in the Crush zone during the Eocene–Oligocene period and extensional/strike-slip movements in the internal zones during the late Cretaceous point to an oblique setting early in the Convergence History. A geotectonic scenario for Convergence from the time of obduction to the present is finally proposed.
Jafar Omrani - One of the best experts on this subject based on the ideXlab platform.
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zagros orogeny a subduction dominated process
Geological Magazine, 2011Co-Authors: Philippe Agard, Jafar Omrani, Laurent Jolivet, Hubert Whitechurch, Bruno Vrielynck, Wim Spakman, Patrick Monie, Bertrand Meyer, Rinus WortelAbstract:This paper presents a synthetic view of the geodynamic evolution of the Zagros orogen within the frame of the Arabia–Eurasia collision. The Zagros orogen and the Iranian plateau preserve a record of the long-standing Convergence History between Eurasia and Arabia across the Neo-Tethys, from subduction/obduction processes to present-day collision (from ~ 150 to 0 Ma). We herein combine the results obtained on several geodynamic issues, namely the location of the oceanic suture zone, the age of oceanic closure and collision, the magmatic and geochemical evolution of the Eurasian upper plate during Convergence (as testified by the successive Sanandaj–Sirjan, Kermanshah and Urumieh–Dokhtar magmatic arcs), the P–T–t History of the few Zagros blueschists, the Convergence characteristics across the Neo-Tethys (kinematic velocities, tomographic constraints, subduction zones and obduction processes), together with a survey of recent results gathered by others. We provide lithospheric-scale reconstructions of the Zagros orogen from ~ 150 to 0 Ma across two SW–NE transects. The evolution of the Zagros orogen is also compared to those of the nearby Turkish and Himalayan orogens. In our geotectonic scenario for the Zagros Convergence, we outline three main periods/regimes: (1) the Mid to Late Cretaceous (115–85 Ma) corresponds to a distinctive period of perturbation of subduction processes and interplate mechanical coupling marked by blueschist exhumation and upper-plate fragmentation, (2) the Paleocene–Eocene (60–40 Ma) witnesses slab break-off, major shifts in arc magmatism and distributed extension within the upper plate, and (3) from the Oligocene onwards (~ 30–0 Ma), collision develops with a progressive SW migration of deformation and topographic build-up (Sanandaj–Sirjan Zone: 20–15 Ma, High Zagros: ~12–8 Ma; Simply Folded Belt: 5–0 Ma) and with partial slab tear at depths (~10 Ma to present). Our reconstructions underline the key role played by subduction throughout the whole Convergence History. We finally stress that such a long-lasting subduction system with changing boundary conditions also makes the Zagros orogen an ideal natural laboratory for subduction processes.
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Convergence History across Zagros (Iran): constraints from collisional and earlier deformation
International Journal of Earth Sciences, 2005Co-Authors: Philippe Agard, Jafar Omrani, Laurent Jolivet, Frederic MouthereauAbstract:The Zagros orogen provides a unique opportunity within the Alpine system to evaluate the interplay between a young Tertiary collision and earlier subduction/obduction processes. Within the Crush zone and the Sanandaj–Sirjan (internal) zone separating the Zagros Fold belt from Central Iran, we document several major tectonic events taking place at the end of the Cretaceous, of the Eocene and from the Mio–Pliocene onwards (ca.
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Convergence History across zagros iran constraints from collisional and earlier deformation
International Journal of Earth Sciences, 2005Co-Authors: Philippe Agard, Jafar Omrani, Laurent Jolivet, Frederic MouthereauAbstract:The Zagros orogen provides a unique opportunity within the Alpine system to evaluate the interplay between a young Tertiary collision and earlier subduction/obduction processes. Within the Crush zone and the Sanandaj–Sirjan (internal) zone separating the Zagros Fold belt from Central Iran, we document several major tectonic events taking place at the end of the Cretaceous, of the Eocene and from the Mio–Pliocene onwards (ca. <20–15 Ma). Contrary to recent interpretations, our data (cross-sections and description of the overall deformation style) strongly suggest that the Main Zagros Thrust (MZT) is deeply rooted, possibly to Moho depths, and that the suture zone effectively runs along the MZT. Field observations show that the final resorption of the oceanic domain took place slightly after 35 Ma and that collision must have started before ca. 23–25 Ma in northern Zagros. The shortening rate across the Crush zone since the Mid-Miocene (20–15 Ma) is estimated at a minimum 3–4 mm/year. Shear movements in the Crush zone during the Eocene–Oligocene period and extensional/strike-slip movements in the internal zones during the late Cretaceous point to an oblique setting early in the Convergence History. A geotectonic scenario for Convergence from the time of obduction to the present is finally proposed.
Laurent Jolivet - One of the best experts on this subject based on the ideXlab platform.
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zagros orogeny a subduction dominated process
Geological Magazine, 2011Co-Authors: Philippe Agard, Jafar Omrani, Laurent Jolivet, Hubert Whitechurch, Bruno Vrielynck, Wim Spakman, Patrick Monie, Bertrand Meyer, Rinus WortelAbstract:This paper presents a synthetic view of the geodynamic evolution of the Zagros orogen within the frame of the Arabia–Eurasia collision. The Zagros orogen and the Iranian plateau preserve a record of the long-standing Convergence History between Eurasia and Arabia across the Neo-Tethys, from subduction/obduction processes to present-day collision (from ~ 150 to 0 Ma). We herein combine the results obtained on several geodynamic issues, namely the location of the oceanic suture zone, the age of oceanic closure and collision, the magmatic and geochemical evolution of the Eurasian upper plate during Convergence (as testified by the successive Sanandaj–Sirjan, Kermanshah and Urumieh–Dokhtar magmatic arcs), the P–T–t History of the few Zagros blueschists, the Convergence characteristics across the Neo-Tethys (kinematic velocities, tomographic constraints, subduction zones and obduction processes), together with a survey of recent results gathered by others. We provide lithospheric-scale reconstructions of the Zagros orogen from ~ 150 to 0 Ma across two SW–NE transects. The evolution of the Zagros orogen is also compared to those of the nearby Turkish and Himalayan orogens. In our geotectonic scenario for the Zagros Convergence, we outline three main periods/regimes: (1) the Mid to Late Cretaceous (115–85 Ma) corresponds to a distinctive period of perturbation of subduction processes and interplate mechanical coupling marked by blueschist exhumation and upper-plate fragmentation, (2) the Paleocene–Eocene (60–40 Ma) witnesses slab break-off, major shifts in arc magmatism and distributed extension within the upper plate, and (3) from the Oligocene onwards (~ 30–0 Ma), collision develops with a progressive SW migration of deformation and topographic build-up (Sanandaj–Sirjan Zone: 20–15 Ma, High Zagros: ~12–8 Ma; Simply Folded Belt: 5–0 Ma) and with partial slab tear at depths (~10 Ma to present). Our reconstructions underline the key role played by subduction throughout the whole Convergence History. We finally stress that such a long-lasting subduction system with changing boundary conditions also makes the Zagros orogen an ideal natural laboratory for subduction processes.
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Convergence History across Zagros (Iran): constraints from collisional and earlier deformation
International Journal of Earth Sciences, 2005Co-Authors: Philippe Agard, Jafar Omrani, Laurent Jolivet, Frederic MouthereauAbstract:The Zagros orogen provides a unique opportunity within the Alpine system to evaluate the interplay between a young Tertiary collision and earlier subduction/obduction processes. Within the Crush zone and the Sanandaj–Sirjan (internal) zone separating the Zagros Fold belt from Central Iran, we document several major tectonic events taking place at the end of the Cretaceous, of the Eocene and from the Mio–Pliocene onwards (ca.
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Convergence History across zagros iran constraints from collisional and earlier deformation
International Journal of Earth Sciences, 2005Co-Authors: Philippe Agard, Jafar Omrani, Laurent Jolivet, Frederic MouthereauAbstract:The Zagros orogen provides a unique opportunity within the Alpine system to evaluate the interplay between a young Tertiary collision and earlier subduction/obduction processes. Within the Crush zone and the Sanandaj–Sirjan (internal) zone separating the Zagros Fold belt from Central Iran, we document several major tectonic events taking place at the end of the Cretaceous, of the Eocene and from the Mio–Pliocene onwards (ca. <20–15 Ma). Contrary to recent interpretations, our data (cross-sections and description of the overall deformation style) strongly suggest that the Main Zagros Thrust (MZT) is deeply rooted, possibly to Moho depths, and that the suture zone effectively runs along the MZT. Field observations show that the final resorption of the oceanic domain took place slightly after 35 Ma and that collision must have started before ca. 23–25 Ma in northern Zagros. The shortening rate across the Crush zone since the Mid-Miocene (20–15 Ma) is estimated at a minimum 3–4 mm/year. Shear movements in the Crush zone during the Eocene–Oligocene period and extensional/strike-slip movements in the internal zones during the late Cretaceous point to an oblique setting early in the Convergence History. A geotectonic scenario for Convergence from the time of obduction to the present is finally proposed.
Matěj Machek - One of the best experts on this subject based on the ideXlab platform.
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garnet exsolution in pyroxene from clinopyroxenites in the moldanubian zone constraining the early pre Convergence History of ultramafic rocks in the variscan orogen
Journal of Metamorphic Geology, 2009Co-Authors: Shah Wali Faryad, David Dolejs, Matěj MachekAbstract:Exsolution lamellae of garnet in clinopyroxene and orthopyroxene porphyroclasts from garnet pyroxenites in the Moldanubian zone were studied to elucidate the pressure–temperature conditions of the exsolution process and to reconstruct the burial and exhumation path of ultramafic rocks in the Variscan orogen. The porphyroclasts occur in a fine-grained matrix with metamorphic fabrics, which consists of clinopyroxene and small amounts of garnet, orthopyroxene and amphibole. The clinopyroxene porphyroclasts contain garnet + orthopyroxene lamellae as well as ilmenite rods that have orientation parallel to (100) planes of the porphyroclasts. Orthopyroxene porphyroclasts host garnet and clinopyroxene lamellae, which show the same lattice preferred orientation. In both cases, lamellar orthopyroxene, clinopyroxene and garnet were partially replaced by secondary amphibole. Composition of exsolution phases and that of host pyroxene were reintegrated according to measured modal proportions and demonstrate that the primary pyroxene was enriched in Al and contained 8–11 mol.% Tschermak components. Conventional thermobarometry and thermodynamic modelling on the reintegrated pyroxene indicate that primary clinopyroxene and orthopyroxene megacrysts crystallized at 1300–1400 °C and 2.2–2.5 GPa. Unmixing and exsolution of garnet and a second pyroxene phase occurred in response to cooling and pressure increase before the peak pressure of 4.5–5.0 GPa was reached at ∼1100 °C. This scenario is consistent with a burial of hot upper-mantle ultramafics into a cold subcratonic environment and subsequent exhumation through 900 °C and 2.2–3.3 GPa, when the pyroxenites would have partially recrystallized during tectonic incorporation into eclogites and felsic granulites.