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Sébastien Castelltort - One of the best experts on this subject based on the ideXlab platform.
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dynamic constraints on the crustal scale rheology of the zagros Fold Belt iran
Geology, 2011Co-Authors: Philippe Yamato, Boris Kaus, Frédéric Mouthereau, Sébastien CastelltortAbstract:Thin-skinned Fold-and-thrust Belts are generally considered as the result of contractional deformation of a sedimentary succession over a weak decollement layer. The resulting surface expression frequently consists of anticlines and synclines spaced in a fairly regular manner. It is thus tempting to use this spacing along with other geological constraints to obtain insights into the dynamics and rheology of the crust on geological time scales. Here we use the Zagros Mountains of Iran as a case study, as it is one of the most spectacular, well-studied thin-skinned Fold-and- thrust Belts in the world. Both analytical and numerical models are employed to study what con- trols Fold spacing and under what conditions Folding dominates over thrusting. The models show that if only a single basal decollement layer is present underneath a brittle sedimentary cover, deformation is dominated by thrusting, which is inconsistent with the data of the Zagros Fold Belt. If we instead take into account additional decollement layers that have been documented in the fi eld, a switch in deformation mode occurs and crustal-scale Folding is obtained with the correct spacing and time scales. We show that Fold spacing can be used to constrain the friction angle of the crust, which is ~5° the Zagros Fold Belt. This implies that on geological time scales, the upper crust is signifi cantly weaker than previously thought, possibly due to the effect of fl
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Dynamic constraints on the crustal-scale rheology of the Zagros Fold Belt, Iran
Geology, 2011Co-Authors: Philippe Yamato, Boris Kaus, Frédéric Mouthereau, Sébastien CastelltortAbstract:Thin-skinned Fold-and-thrust Belts are generally considered as the result of contractional deformation of a sedimentary succession over a weak décollement layer. The resulting surface expression frequently consists of anticlines and synclines spaced in a fairly regular manner. It is thus tempting to use this spacing along with other geological constraints to obtain insights into the dynamics and rheology of the crust on geological time scales. Here we use the Zagros Mountains of Iran as a case study, as it is one of the most spectacular, well-studied thin-skinned Fold-andthrust Belts in the world. Both analytical and numerical models are employed to study what controls Fold spacing and under what conditions Folding dominates over thrusting. The models show that if only a single basal décollement layer is present underneath a brittle sedimentary cover, deformation is dominated by thrusting, which is inconsistent with the data of the Zagros Fold Belt. If we instead take into account additional décollement layers that have been documented in the fi eld, a switch in deformation mode occurs and crustal-scale Folding is obtained with the correct spacing and time scales. We show that Fold spacing can be used to constrain the friction angle of the crust, which is ~5° in the Zagros Fold Belt. This implies that on geological time scales, the upper crust is signifi cantly weaker than previously thought, possibly due to the effect of fl uids.
David Phillips - One of the best experts on this subject based on the ideXlab platform.
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The Palaeozoic tectono-metallogenic evolution of the northern Tasman Fold Belt System, Australia: Interplay of subduction rollback and accretion
Ore Geology Reviews, 2006Co-Authors: I.m.a. Vos, Frank P. Bierlein, David PhillipsAbstract:Abstract The Tasman Fold Belt System in eastern Australia provides a record of the Palaeozoic geological history and growth of the Australian continent along the proto-Pacific margin of Gondwana inboard of an extensive and long-lived subduction system. The Hodgkinson and Broken River provinces represent prominent geological elements of this system and together form the northern Tasman Fold Belt System. Geochronological age dating of the timing of gold formation in the Amanda Bel Goldfield in the Broken River Province and the Hodgkinson Goldfield in the Hodgkinson Province provides constraints on the occurrence of a deformation and mineralisation episode in the Late Devonian–Early Carboniferous. Integration of these newly-obtained data with petrogenetic constraints and a time–space evaluation of the geological evolution of the Hodgkinson and Broken River provinces, as well as other terranes in the northern Tasman Fold Belt System, allows for the development of a geodynamic model for the Palaeozoic evolution of the northern Tasman Fold Belt System. Our model indicates that three cycles of extension–contraction occurred during the Palaeozoic evolution of the northern Tasman Fold Belt System. Episodes of extension were controlled by rollback of the subduction system along the proto-Pacific margin of Gondwana, whereas episodes of contraction resulted from accretion following the arrival of positively buoyant segments (i.e., micro-continental blocks/oceanic plateaus) at the subducting trench. Our composite interpretative model on the geodynamic evolution of the northern Tasman Fold Belt System integrates the timing of the development of mineral deposits throughout this part of the system and provides a significant advancement in the understanding of Palaeozoic geodynamics along the margin of Gondwana in northeast Australia and allows comparison with the southern part of the Tasman Fold Belt System.
Geoff Manby - One of the best experts on this subject based on the ideXlab platform.
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The West Spitsbergen Fold Belt: The result of Late Cretaceous-Palaeocene Greenland-Svalbard convergence?
Geological Journal, 1993Co-Authors: Nikos Lyberis, Geoff ManbyAbstract:The West Spitsbergen Fold Belt, together with the Eurekan structures of northern Greenland and Ellesmere Island, are suggested to be the result of Late Cretaceous-Palaeocene intracontinental compressional tectonics. The Late Palaeozoic –Mesozoic rocks of western Spitsbergen are characterized by near-foreland deformation with ramp-flat, top-to-the east thrust trajectories, whereas structurally higher nappes involving Caledonian complexes are typified by more listric thrusts and mylonite zones. A minimum of 40 km of shortening is estimated for the northern part of the West Spitsbergen Fold Belt. The axial trends in the West Spitsbergen and the North Greenland Eurekan Fold Belts parallel the principal fault zones which accommodated the separation of Greenland and Svalbard after Chron 25/24. In northern Greenland, north directed Eurekan thrusts associated with mylonites and cleavage formation represent at least 10 km of shortening. Between 50 and 100 km of shortening is estimated for the markedly arcuate Eurekan Fold Belt of Ellesmere Island, but the principal tectonic transport is eastwards. Kinematic reconstructions suggest that Svalbard was linked to North America before the opening of the Eurasian Basin and Norwegian — Greenland Sea. In the Late Cretaceous — Palaeocene interval, the relative motion between Greenland and North America was convergent across the Greenland — Svalbard margin, giving rise to the West Spitsbergen Fold Belt and the Eurekan structures of North Greenland.
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The origin of the West Spitsbergen Fold Belt from geological constraints and plate kinematics: implications for the Arctic
Tectonophysics, 1993Co-Authors: Nikos Lyberis, Geoff ManbyAbstract:Abstract The West Spitsbergen Fold Belt, which extends for 300 km along the western margin of Svalbard and is up to 80 km wide, has much in common with foreland Fold and thrust Belts. The near-foreland segment of the Fold Belt exhibits ramp-flat thrust trajectories whilst structurally higher nappes are typified by more listric thrusts. Higher nappes to the west contain imbricated Carboniferous and basement rocks showing that the latter were actively involved in the Fold Belt deformation and a minimum of 80 km total shortening perpendicular to the western margin of Svalbard is estimated. The early stages of the Eurekan deformation in North Greenland can be linked to that of the West Spitsbergen Fold Belt and the combined shortening across the two Fold Belts may exceed 80 km. In Ellesmere Island Eurekan structures are distributed in an arc-like Belt which records between 50 to 100 km of shortening since the Late Cretaceous. Kinematic reconstructions suggest that before the opening of the Eurasian Basin and Norwegian-Greenland Sea (Chron 25), Svalbard was linked to North America. In the Late Cretaceous-Palaeocene interval the motion across the Greenland-Svalbard margin, was mainly convergent giving rise to the West Spitsbergen Fold Belt and the Eurekan structures of North Greenland. The dextral separation of Greenland and Svalbard in post-Chron 24 time was accompanied by extension followed by pure extension in post-Chron 13 time.
I.m.a. Vos - One of the best experts on this subject based on the ideXlab platform.
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The Palaeozoic tectono-metallogenic evolution of the northern Tasman Fold Belt System, Australia: Interplay of subduction rollback and accretion
Ore Geology Reviews, 2006Co-Authors: I.m.a. Vos, Frank P. Bierlein, David PhillipsAbstract:Abstract The Tasman Fold Belt System in eastern Australia provides a record of the Palaeozoic geological history and growth of the Australian continent along the proto-Pacific margin of Gondwana inboard of an extensive and long-lived subduction system. The Hodgkinson and Broken River provinces represent prominent geological elements of this system and together form the northern Tasman Fold Belt System. Geochronological age dating of the timing of gold formation in the Amanda Bel Goldfield in the Broken River Province and the Hodgkinson Goldfield in the Hodgkinson Province provides constraints on the occurrence of a deformation and mineralisation episode in the Late Devonian–Early Carboniferous. Integration of these newly-obtained data with petrogenetic constraints and a time–space evaluation of the geological evolution of the Hodgkinson and Broken River provinces, as well as other terranes in the northern Tasman Fold Belt System, allows for the development of a geodynamic model for the Palaeozoic evolution of the northern Tasman Fold Belt System. Our model indicates that three cycles of extension–contraction occurred during the Palaeozoic evolution of the northern Tasman Fold Belt System. Episodes of extension were controlled by rollback of the subduction system along the proto-Pacific margin of Gondwana, whereas episodes of contraction resulted from accretion following the arrival of positively buoyant segments (i.e., micro-continental blocks/oceanic plateaus) at the subducting trench. Our composite interpretative model on the geodynamic evolution of the northern Tasman Fold Belt System integrates the timing of the development of mineral deposits throughout this part of the system and provides a significant advancement in the understanding of Palaeozoic geodynamics along the margin of Gondwana in northeast Australia and allows comparison with the southern part of the Tasman Fold Belt System.
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Time-space evaluation of the tectono-metallogenic evolution of the northern Tasman Fold Belt System, northeast Queensland, Australia
ASEG Extended Abstracts, 2006Co-Authors: I.m.a. Vos, Frank P. BierleinAbstract:The Tasman Fold Belt System in eastern Australia provides a record of the Palaeozoic geological history and growth of the Australian continent along the proto-Pacific margin of Gondwana inboard of an extensive and long-lived subduction system. The Hodgkinson and Broken River provinces represent prominent geological elements of this system and together form the northern Tasman Fold Belt System. Integration of newly-obtained data with a time-space evaluation of the geological evolution of the Hodgkinson and Broken River provinces, as well as other terranes in the northern Tasman Fold Belt System, allows for the development of a geodynamic model for the Palaeozoic evolution of the northern Tasman Fold Belt System. Our model indicates that three cycles of extension ? contraction occurred during the Palaeozoic evolution of the northern Tasman Fold Belt System. Episodes of extension were controlled by roll-back of the subduction system along the Australian margin, whereas episodes of contraction resulted from accretion following the arrival of positively buoyant segments (i.e., micro-continental blocks / oceanic plateaux) at the subducting trench. Our composite interpretative model on the geodynamic evolution of the northern Tasman Fold Belt System integrates the timing of the development of mineral deposits throughout this part of the system and provides a significant advancement in the understanding of Palaeozoic geodynamics along the margin of Gondwana in northeast Australia.
Gregg W. Morrison - One of the best experts on this subject based on the ideXlab platform.
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Toward an understanding of the metallogeny of the Tasman Fold Belt system
Economic Geology, 1995Co-Authors: John L. Walshe, Paul S. Heithersay, Gregg W. MorrisonAbstract:The Tasman Fold Belt system which makes up the eastern third of the Australian continent is a composite of five Paleozoic orogenic Belts. The major mineral provinces of the Tasman Fold Belt system include provinces of volcanic-hosted massive sulfide deposits, porphyry-granitoid-associated Cu-Au and Au deposits, and granitoid- associated Sn and W deposits as well as provinces of structurally controlled Au and Cu-Pb-Zn deposits. The localization of these provinces is discussed in terms of the nature of the magmatism which is a source of heat and in many cases of fluids and metals, the fracture systems which facilitate the transfer of heat, magmas, and/or aqueous fluids through the crust, and the timing and nature of the stress regimes that permit these fracture systems to be open to fluid flow. The available data indicate that the magmatism of the Cu-Au province of Central-West New South Wales originated in the mantle. Magma systems linked with the deposits of the volcanic-hosted massive sulfide province of western Tasmania, the Sn-W provinces of the Tasman Fold Belt system, and the porphyry-associated Au deposits of north Queensland had their roots in crust mantle interactions. Crystal fractionation was an important process in the magma systems related to the development of these provinces. A feature of the Tasman Fold Belt system is the prevalence of major north-south-trending fault systems. More subtle west- northwest structural trends can be appreciated at the continent scale and these Proterozoic structural trends appear to have exerted a significant control on the distribution of major mineral provinces within the Tasman Fold Belt system. Extension reactivation of basement structures late in tectonic cycles was a major mechanism for creating permeable domains in the upper crust and focusing fluid flow and hydrothermal mineralization. It is suggested that the Permo-Carboniferous Au and Sn provinces of north Queensland developed.