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Marc Poujol - One of the best experts on this subject based on the ideXlab platform.
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Origin and duration of late orogenic Magmatism in the foreland of the Variscan belt (Lesponne — Chiroulet — Neouvielle area, french Pyrenees)
Lithos, 2019Co-Authors: Baptiste Lemirre, Bryan Cochelin, Stéphanie Duchêne, Michel De Saint Blanquat, Marc PoujolAbstract:During the late stage of the Variscan orogeny, the pyrenean segment underwent intense Magmatism and regional high temperature – low pressure metamorphism. In the Lesponne – Chiroulet – Neouvielle area, a granodioritic pluton was emplaced in the upper crust while dioritic to granitic magmas were emplaced in metamorphic domes. Magmatism was contemporaneous with the regional crustal partial melting recorded in the core of the domes. The area is therefore a key target in the Pyrenees to discuss potential magmatic sources as well as the age and duration of the late Variscan Magmatism. Geochemical data on representative magmatic rocks highlight two distinct sources of magma: a mantle source and a metasedimentary crustal source that produced respectively metaluminous and peraluminous magmas. Geochronological results show that Magmatism took place over a period of about 10 My from ca. 303 to ca. 290 Ma. During this period, the middle to lower crust was composed of partially molten metasediments intruded by mantle and crustal magmas that crystallized in a final pulse at ca. 290 Ma. Late Variscan metamorphism and Magmatism recorded in the Pyrenees have to be related to a significant and rapid heating from the underlying mantle rather than to crustal processes such as the maturation of a thickened continental crust. We propose that the initiation of metamorphism and bimodal Magmatism at ca. 305 Ma in the Pyrenees is the expression of the delamination of the Gondwanan lithospheric mantle at a global scale in the Variscan belt.
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Periodic Paleoproterozoic calc-alkaline Magmatism at the south eastern margin of the Yilgarn Craton; implications for Nuna configuration
Precambrian Research, 2019Co-Authors: M.i.h. Hartnady, Marc Poujol, C.l. Kirkand, R.h. Smithies, C. ClarkAbstract:The age and composition of magmas provide fundamental information to chart the tectonic setting of crustal development through time and hence refine paleogeographic reconstructions. The Biranup Zone of the Albany-Fraser Orogen in southwestern Australia preserves a protracted record of Magmatism associated with the formation and subsequent break-up of the Paleoproterozoic supercontinent Nuna. Yet, the configuration of Proterozoic Australia within Nuna is not well constrained. New U-Pb zircon geochronology on four samples of mafic intrusions in the north eastern Biranup Zone yield U-Pb crystallisation ages of 1809 ± 17 Ma, 1798 ± 12 Ma, 1796 ± 12 Ma, and 1755 ± 12 Ma coeval with known pulses of felsic Magmatism elsewhere in the orogen. The Lu-Hf isotope composition of zircon crystals from these mafic intrusions, and the metasedimentary rocks they intrude, reveal juvenile magmatic input into the Archean Yilgarn Craton with this Magmatism commencing as early as c. 1.90 Ga. Following this juvenile Magmatism, the margin of the craton was affected by at least three pulses of calcic to calc-alkaline Magmatism between 1.81 and 1.65 Ga. Secular changes in zircon Hf isotope composition are comparable in both duration and periodicity to 50–100 Ma changes in magma composition and zircon chemistry observed in modern volcanic arcs of the American Cordillera and in Cambrian to Carboniferous accretionary complexes of eastern Australia. Isotopic patterns and whole-rock chemistry are apparently consistent with the 1.81–1.70 Ga Paleoproterozoic igneous rocks of the Albany-Fraser Orogen forming in a magmatic arc above a Pacific-type subduction zone which extended along the south eastern margin of the Yilgarn Craton. This interpretation is consistent with paleomagnetic data which places the Yilgarn Craton on the periphery of the supercontinent Nuna at 1.90–1.60 Ga.
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A Sb-Au mineralizing peak at 360 Ma in the Variscan Belt, an insight into Central Brittany (France)
2018Co-Authors: Anthony Pochon, Marc Poujol, Gloaguen Eric, Yannick Branquet, Gilles Ruffet, Philippe Boulvais, Charles Gumiaux, Florence Cagnard, Denis GapaisAbstract:Numerous Sb-Au deposits are known in the European Variscan belt and are often associated with the late Variscan hydrothermal events linked to postorogenic extension and strike-slip faults, through the whole belt. Central Brittany hosts several Sb-Au occurrences, such as the Le Semnon Sb-Au deposit or the Saint-Aubin-des-Châteaux base metal-Sb-Au occurrence. In order to provide new constraints on the Sb-Au mineralization framework of the Central Brittany, structural, geochronological and chemical analyses have been performed on the Le Semnon deposit and the Saint-Aubin-des-Châteaux occurrence. Main results show that Sb-Au trapping of these two occurrences occurred at ca. 360 Ma. This indicates an Early Carboniferous economic Sb-Au mineralizing peak in the eastern part of the Central Brittany. Moreover, a mafic Magmatism is widespread in the region and can acted as the plumbing system for Sb-Au mineralizing fluids, such as the dolerite dyke of the Semnon Sb-Au deposit. Absolute dating of this mafic Magmatism coupled with the early character of hydrothermal alteration associated with Sb-Au mineralizing fluids strongly suggest that the emplacement of Sb-Au mineralization and mafic Magmatism was coeval. It appears that the emplacement of mafic Magmatism represent a major trigger for this mineralizing system at shallow depths (less than 3 km). These new data and the ca. 360 Ma massive sulfides of south Iberia emphasize that the Early Carboniferous mafic Magmatism has to be taken into account for the understanding of the genesis of mineralizing systems and the redistribution of metals in the crust, at the scale of the whole Variscan belt.
Michael J Grubensky - One of the best experts on this subject based on the ideXlab platform.
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spatial and temporal relationships between mid tertiary Magmatism and extension in southwestern arizona
Journal of Geophysical Research, 1995Co-Authors: Jon E Spencer, Stephen M Richard, Stephen J Reynolds, Robert J Miller, Muhammad Shafiqullah, Wyatt Gilbert, Michael J GrubenskyAbstract:Cenozoic Magmatism in southwestern Arizona, which is within the Basin and Range tectonic province, occurred almost entirely between 15 and 25 Ma. Volcanic rocks typically consist, in ascending order, of (1) a thin sequence of mafic to intermediate lava flows, (2) voluminous felsic lava flows and pyroclastic rocks with minor to moderate amounts of intermediate to mafic lava flows, and (3) basalt and andesite. Volcanic rock sequences rest disconformably on pre-Tertiary bedrock in most areas but locally overlie substantial coarse clastic debris that was deposited immediately before and during earliest Magmatism. Prevolcanic clastic debris is interpreted as a consequence of local early normal faulting. In most regions, tilting related to extension began later and occurred during or after eruption of felsic volcanic rocks and before the end of younger mafic volcanism. Extension generally ended before about 17 Ma except in a northwest trending belt adjacent to the relatively unfaulted and topographically elevated Transition Zone tectonic province which is adjacent to the Colorado Plateau. Rapid cooling of metamorphic core complexes and tilting of young basalts and coarse clastic rocks continued in this belt until as recently as 11 Ma. Extension was extreme in this belt, whereas it was generally moderate to slight in other parts of southwestern Arizona. Large-magnitude extension was not associated with areas of greatest igneous activity, and rapid cooling and exhumation of core complexes postdated local Magmatism. These relationships are inconsistent with theories that relate genesis of metamorphic core complexes to magma intrusion in the upper crust. Except for young extension in this northwest trending belt, there are no apparent regional migration trends for either Magmatism or extension within southwestern Arizona. Lack of substantial extension before Magmatism and general lack of Magmatism during youngest extension are inconsistent with the hypothesis that Magmatism was the product of decompression melting during lithospheric extension. The long duration and large magnitude of extension adjacent to the Transition Zone tectonic province and within an area of earlier crustal thickening are consistent with the hypothesis that extension was driven by the gravitational potential energy of elevated land mass and crustal roots. Regional magmatic heating apparently weakened the lithosphere and triggered extension but did not control extension locally.
Osman Bektas - One of the best experts on this subject based on the ideXlab platform.
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the nature of transition from adakitic to non adakitic Magmatism in a slab window setting a synthesis from the eastern pontides ne turkey
Geoscience frontiers, 2013Co-Authors: Yener Eyuboglu, Sunlin Chung, M Santosh, Francis O Dudas, Enver Akaryali, Kemal Akdag, Osman BektasAbstract:Abstract The eastern Pontides orogenic belt provides a window into continental arc Magmatism in the Alpine–Himalayan belt. The late Mesozoic–Cenozoic geodynamic evolution of this belt remains controversial. Here we focus on the nature of the transition from the adakitic to non-adakitic Magmatism in the Kale area of Gumushane region in NE Turkey where this transition is best preserved. The adakitic lithologies comprise porphyries and hyaloclastites. The porphyries are represented by biotite-rich andesites, hornblende-rich andesite and dacite. The hayaloclastites represent the final stage of adakitic activity and they were generated by eruption/intrusion of adakitic andesitic magma into soft carbonate mud. The non-adakitic lithologies include basaltic-andesitic volcanic and associated pyroclastic rocks. Both rock groups are cutting by basaltic dikes representing the final stage of the Cenozoic Magmatism in the study area. We report zircon U-Pb ages of 48.71 ± 0.74 Ma for the adakitic rocks, and 44.68 ± 0.84 Ma for the non-adakitic type, suggesting that there is no significant time gap during the transition from adakitic to non-adakitic Magmatism. We evaluate the origin, magma processes and tectonic setting of the Magmatism in the southern part of the eastern Pontides orogenic belt. Our results have important bearing on the late Mesozoic–Cenozoic geodynamic evolution of the eastern Mediterranean region.
H C Larsen - One of the best experts on this subject based on the ideXlab platform.
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rapid transition from continental breakup to igneous oceanic crust in the south china sea
Nature Geoscience, 2018Co-Authors: H C Larsen, G Mohn, M Nirrengarten, Joann M Stock, Z Jian, A Klaus, C A Alvarezzarikian, Jacopo Boaga, S A BowdenAbstract:Continental breakup represents the successful process of rifting and thinning of the continental lithosphere, leading to plate rupture and initiation of oceanic crust formation. Magmatism during breakup seems to follow a path of either excessive, transient Magmatism (magma-rich margins) or of igneous starvation (magma-poor margins). The latter type is characterized by extreme continental lithospheric extension and mantle exhumation prior to igneous oceanic crust formation. Discovery of magma-poor margins has raised fundamental questions about the onset of ocean-floor type Magmatism, and has guided interpretation of seismic data across many rifted margins, including the highly extended northern South China Sea margin. Here we report International Ocean Discovery Program drilling data from the northern South China Sea margin, testing the magma-poor margin model outside the North Atlantic. Contrary to expectations, results show initiation of Mid-Ocean Ridge basalt type Magmatism during breakup, with a narrow and rapid transition into igneous oceanic crust. Coring and seismic data suggest that fast lithospheric extension without mantle exhumation generated a margin structure between the two endmembers. Asthenospheric upwelling yielding Mid-Ocean Ridge basalt-type Magmatism from normal-temperature mantle during final breakup is interpreted to reflect rapid rifting within thin pre-rift lithosphere.
Jon E Spencer - One of the best experts on this subject based on the ideXlab platform.
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spatial and temporal relationships between mid tertiary Magmatism and extension in southwestern arizona
Journal of Geophysical Research, 1995Co-Authors: Jon E Spencer, Stephen M Richard, Stephen J Reynolds, Robert J Miller, Muhammad Shafiqullah, Wyatt Gilbert, Michael J GrubenskyAbstract:Cenozoic Magmatism in southwestern Arizona, which is within the Basin and Range tectonic province, occurred almost entirely between 15 and 25 Ma. Volcanic rocks typically consist, in ascending order, of (1) a thin sequence of mafic to intermediate lava flows, (2) voluminous felsic lava flows and pyroclastic rocks with minor to moderate amounts of intermediate to mafic lava flows, and (3) basalt and andesite. Volcanic rock sequences rest disconformably on pre-Tertiary bedrock in most areas but locally overlie substantial coarse clastic debris that was deposited immediately before and during earliest Magmatism. Prevolcanic clastic debris is interpreted as a consequence of local early normal faulting. In most regions, tilting related to extension began later and occurred during or after eruption of felsic volcanic rocks and before the end of younger mafic volcanism. Extension generally ended before about 17 Ma except in a northwest trending belt adjacent to the relatively unfaulted and topographically elevated Transition Zone tectonic province which is adjacent to the Colorado Plateau. Rapid cooling of metamorphic core complexes and tilting of young basalts and coarse clastic rocks continued in this belt until as recently as 11 Ma. Extension was extreme in this belt, whereas it was generally moderate to slight in other parts of southwestern Arizona. Large-magnitude extension was not associated with areas of greatest igneous activity, and rapid cooling and exhumation of core complexes postdated local Magmatism. These relationships are inconsistent with theories that relate genesis of metamorphic core complexes to magma intrusion in the upper crust. Except for young extension in this northwest trending belt, there are no apparent regional migration trends for either Magmatism or extension within southwestern Arizona. Lack of substantial extension before Magmatism and general lack of Magmatism during youngest extension are inconsistent with the hypothesis that Magmatism was the product of decompression melting during lithospheric extension. The long duration and large magnitude of extension adjacent to the Transition Zone tectonic province and within an area of earlier crustal thickening are consistent with the hypothesis that extension was driven by the gravitational potential energy of elevated land mass and crustal roots. Regional magmatic heating apparently weakened the lithosphere and triggered extension but did not control extension locally.
