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Emmanuel John M Carranza - One of the best experts on this subject based on the ideXlab platform.
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the ore genesis of the jebel mecella and sidi taya f ba zn pb mississippi valley type deposits fluorite zaghouan province ne tunisia in relation to Alpine Orogeny constraints from geological sulfur and lead isotope studies
Comptes Rendus Geoscience, 2019Co-Authors: Nejib Jemmali, Larbi Rddad, Fouad Souissi, Emmanuel John M CarranzaAbstract:Abstract Jebel Mecella and Sidi Taya F–(Ba Pb Zn) deposits are located within the Fluorite Zaghouan Province (NE Tunisia). The mineralization occurs along the unconformity surface between the Jurassic limestones and Upper Cretaceous rocks. The mineralization consists mainly of fluorite, barite, sphalerite, and galena. The δ34S values of barite at Jebel Mecella (14.8–15.4‰) and at Sidi Taya (21.6–22.2‰) closely match those of the Triassic evaporites and Messinian seawater, respectively. The range of δ34S values of galena and sphalerite in both deposits (−6.9 to +2.4‰) suggests the involvement of thermochemical sulfate reduction and possibly organically-bound sulfur in the generation of sulfur. Lead isotope data with 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios of 18.893–18.903, 15.684–15.699, and 38.850–38.880, respectively suggests a single homogeneous source reservoir of Paleozoic age and/or the homogenization of the Paleozoic–Cretaceous multireservoir-derived fluids along their long migration paths to the loci of deposition during the Alpine Orogeny.
Jose Maria Tubia - One of the best experts on this subject based on the ideXlab platform.
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post variscan basin evolution in the central pyrenees insights from the stephanian permian anayet basin
Comptes Rendus Geoscience, 2016Co-Authors: Lidia Rodriguezmendez, Julia Cuevas, Jose Maria TubiaAbstract:Abstract The Anayet Basin, in the central Pyrenees, records a Stephanian–Permian continental succession including three Permian volcanic episodes. The absolute chronology of these rocks has allowed us to better constrain the early post-Variscan evolution of the Pyrenees. The transtensional regime responsible for the formation of the pull-apart Anayet Basin began at least in Stephanian times, the age of the first post-Variscan deposits in the area, and lasted until Late Permian. During Middle Eocene times, the Alpine Orogeny inverted the Anayet Basin and led to the formation of south-vergent chevron folds and axial plane penetrative cleavage.
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Post-Variscan basin evolution in the central Pyrenees: Insights from the Stephanian–Permian Anayet Basin
Comptes Rendus Geoscience, 2016Co-Authors: Lidia Rodríguez-méndez, Julia Cuevas, Jose Maria TubiaAbstract:Abstract The Anayet Basin, in the central Pyrenees, records a Stephanian–Permian continental succession including three Permian volcanic episodes. The absolute chronology of these rocks has allowed us to better constrain the early post-Variscan evolution of the Pyrenees. The transtensional regime responsible for the formation of the pull-apart Anayet Basin began at least in Stephanian times, the age of the first post-Variscan deposits in the area, and lasted until Late Permian. During Middle Eocene times, the Alpine Orogeny inverted the Anayet Basin and led to the formation of south-vergent chevron folds and axial plane penetrative cleavage.
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Post-Variscan basin evolution in the central Pyrenees: Insights from the Stephanian–Permian Anayet Basin
Comptes Rendus Geoscience, 2016Co-Authors: Lidia Rodríguez-méndez, Julia Cuevas, Jose Maria TubiaAbstract:Abstract The Anayet Basin, in the central Pyrenees, records a Stephanian–Permian continental succession including three Permian volcanic episodes. The absolute chronology of these rocks has allowed us to better constrain the early post-Variscan evolution of the Pyrenees. The transtensional regime responsible for the formation of the pull-apart Anayet Basin began at least in Stephanian times, the age of the first post-Variscan deposits in the area, and lasted until Late Permian. During Middle Eocene times, the Alpine Orogeny inverted the Anayet Basin and led to the formation of south-vergent chevron folds and axial plane penetrative cleavage.
Othmar Müntener - One of the best experts on this subject based on the ideXlab platform.
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Current challenges for explaining (ultra)high‐pressure tectonism in the Pennine domain of the Central and Western Alps
Journal of Metamorphic Geology, 2015Co-Authors: Filippo Schenker, Stefan M. Schmalholz, Evangelos Moulas, Jean Pleuger, Lukas P. Baumgartner, Yuri Y. Podladchikov, Johannes C. Vrijmoed, N. Buchs, Othmar MüntenerAbstract:The Pennine domain of the Central and Western (PCW) Alps, including the Dora-Maira, Monte Rosa, Gran Paradiso, Adula/Cima Lunga nappes and the Zermatt-Saas zone underwent ultrahigh- or high-pressure [(U)HP >1.5 GPa] metamorphism during the Alpine Orogeny. We review structural, petrological and geochronological data for the (U)HP units in the PCW Alps (i) to clarify the relationship between (U)HP metamorphism and deformation, (ii) to confront published exhumation models for the (U)HP units with the reviewed data and (iii) to evaluate consequences of different pre-Alpine paleogeographic settings (Penrose-type ocean v. hyperextended margins) on the Alpine Orogeny. The review indicates that (i) peak pressures are recorded only in minor volumes of the corresponding tectonic nappes; (ii) (U)HP rocks occur within coherent and imbricate thrust sheets which show substantial pressure jumps; (iii) peak pressures are mostly associated with a top-to-the-foreland kinematics; (iv) decompression from (U)HP (4 to >1.5 GPa) to greenschist or amphibolite facies (~1 GPa) metamorphic conditions was fast ( ~3180 kg m3) rocks is questionable, because there is no evidence of such rocks around the (U)HP units. An alternative model, which could explain the main characteristics of the (U)HP units in the PCW Alps, is an orogenic wedge model that (i) involves dynamic stresses deviating from lithostatic pressure and (ii) is formed during the convergence of hyperextended margins. Deviations of dynamic stresses from the lithostatic pressure and local pressure variations cannot be excluded during the Alpine Orogeny, but these deviations and variations have not been clearly identified until now.
Nicole Rayner - One of the best experts on this subject based on the ideXlab platform.
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Multiple subduction cycles in the Alpine Orogeny, as recorded in single zircon crystals (Rhodope zone, Greece)
Gondwana Research, 2016Co-Authors: Anthi Liati, Thomas Theye, C. Mark Fanning, Dieter Gebauer, Nicole RaynerAbstract:Abstract High- and ultrahigh-pressure metamorphic crustal rocks in orogenic belts provide evidence for subduction into the mantle and subsequent exhumation. The timing of metamorphism(s) of complex high- and ultrahigh-pressure rocks can be registered in the robust mineral zircon, able to preserve different growth generations. Here we present sensitive high resolution ion microprobe (SHRIMP) U–Pb age and REE compositional data from zircon in migmatitic gneisses from the ultrahigh-pressure Kimi unit of the Alpine Rhodope zone (Greece). Single zircon crystals preserve one to two magmatic (one inherited and one syn-magmatic) and two to three metamorphic generations. The 206Pb/238U ages, combined with REE zircon data, mineral inclusions in metamorphic zircon, petrological data from the matrix assemblages, as well as pseudosection calculations are interpreted to reflect Permian crystallization of the protolith of the studied gneisses and subsequent repeated subductions to high pressures over the course of the Alpine Orogeny (at ~ 158 Ma, suggested to be close to the time of ultrahigh-pressure metamorphism; at ~ 74 Ma, and possibly also at ~ 42 Ma). This inference stands in contrast to the general thinking about subduction/exhumation cycles during Alpine-type orogenesis along a single path and is in line with recent simulation results about repeated subductions. The recognition of two distinct high-pressure subduction cycles within the Alpine Orogeny in a time frame of ~ 80 Ma (and the indication of an additional subduction cycle ~ 30 Ma later) in the same zircon crystal is remarkable. It provides evidence for repeated deep subductions over longer (~ 80 Ma) and possibly also shorter (~ 30 Ma) frequencies and emphasizes the view that lithospheric plate collision/subduction during the Alpine Orogeny in the Rhodope zone does not have to be a continuous, protracted process. A regime of repeated subduction/exhumation events involving micro-continental fragments intervening between the European and Adriatic margins may be rather responsible for the different (U)HP age clusters in the Rhodope zone.
Ian Cartwright - One of the best experts on this subject based on the ideXlab platform.
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Textural implications of high-pressure fluid flow controlled by pre-subduction deformation and alteration patterns
Journal of Geochemical Exploration, 2000Co-Authors: Joanne A Miller, Ian S. Buick, Ian CartwrightAbstract:Abstract Pillow lavas from the Corsican ophiolite (France) were metamorphosed to eclogite-facies conditions during the Alpine Orogeny. The mineralogical and textural evolution of these pillows, the patterns of fluid infiltration around and through them, and their mechanical response to subduction zone metamorphism and subsequent exhumation were primarily controlled by the pattern of intrapillow fracturing that occurred during sub-seafloor alteration during much earlier crustal accretion. Primary rheological differences established on the seafloor between pillow clasts and intrapillow fracture zones played a fundamental role in controlling the extent of subduction-related fluid flow during Alpine Orogenesis in these units.
