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M Chichorro - One of the best experts on this subject based on the ideXlab platform.
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new late middle to early late ordovician u pb zircon ages of extension related felsic volcanic rocks in the eastern pyrenees ne iberia tectonic implications
Geological Magazine, 2019Co-Authors: Joan Marti, Luigi Augusto Solari, J M Casas, M ChichorroAbstract:Pre-Variscan basement rocks from the Pyrenees provide evidence of several magmatic episodes with complex geodynamic histories from late Neoproterozoic to Palaeozoic times. One of the most significant episodes, consisting of several granitic and granodioritic bodies and volcanic rocks, mostly pyroclastic in nature, dates from the Late Ordovician period. In the Eastern Pyrenees, this magmatism is well represented in the Ribes de Freser and Nuria areas; here, the Nuria orthogneiss and the Ribes Granophyre, both dated at c . 457–460 Ma, seem to form a calc-alkaline plutonic suite emplaced at different crustal levels. The presence of numerous pyroclastic deposits and lavas interbedded with Upper Ordovician (Sandbian–lower Katian, formerly Caradoc) sediments, intruded by the Ribes Granophyre, suggests that this magmatic episode also generated significant volcanism. Moreover, the area hosts an important volume of rhyolitic ignimbrites and andesitic lavas affected by Alpine deformation. These volcanic rocks were previously attributed to late Variscan volcanism, extensively represented in other areas of the Pyrenees. Here we present the first five laser-ablation U–Pb zircon dates for this ignimbritic succession and two new ages for the Ribes Granophyre. The ages of the ignimbrites, overlapping within error, are all 460 Ma, suggesting a genetic relationship between the plutonic and volcanic rocks and indicating that the Sandbian–Katian magmatism is much more voluminous than reported in previous studies, and possibly includes mega-eruptions linked to the formation of collapse calderas.
Mary R. Reid - One of the best experts on this subject based on the ideXlab platform.
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Accessory mineral U–Th–Pb ages and ^40Ar/^39Ar eruption chronology, and their bearing on rhyolitic magma evolution in the Pleistocene Coso volcanic field, California
Contributions to Mineralogy and Petrology, 2009Co-Authors: Justin I. Simon, Charles R Bacon, Jorge A Vazquez, Axel K Schmitt, Paul R. Renne, Mary R. ReidAbstract:We determined Ar/Ar eruption ages of eight extrusions from the Pleistocene Coso volcanic field, a long-lived series of small volume rhyolitic domes in eastern California. Combined with ion-microprobe dating of crystal ages of zircon and allanite from these lavas and from Granophyre geothermal well cuttings, we were able to track the range of magma-production rates over the past 650 ka at Coso. In ≤230 ka rhyolites we find no evidence of protracted magma residence or recycled zircon (or allanite) from Pleistocene predecessors. A significant subset of zircon in the ~85 ka rhyolites yielded ages between ~100 and 200 Ma, requiring that generation of at least some rhyolites involves material from Mesozoic basement. Similar zircon xenocrysts are found in an ~200 ka Granophyre. The new age constraints imply that magma evolution at Coso can occur rapidly as demonstrated by significant changes in rhyolite composition over short time intervals (≤10’s to 100’s ka). In conjunction with radioisotopic age constraints from other young silicic volcanic fields, dating of Coso rhyolites highlights the fact that at least some (and often the more voluminous) rhyolites are produced relatively rapidly, but that many small-volume rhyolites likely represent separation from long-lived mushy magma bodies.
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accessory mineral u th pb ages and 40ar 39ar eruption chronology and their bearing on rhyolitic magma evolution in the pleistocene coso volcanic field california
Contributions to Mineralogy and Petrology, 2009Co-Authors: Justin I. Simon, Charles R Bacon, Jorge A Vazquez, Axel K Schmitt, Paul R. Renne, Mary R. ReidAbstract:We determined Ar/Ar eruption ages of eight extrusions from the Pleistocene Coso volcanic field, a long-lived series of small volume rhyolitic domes in eastern California. Combined with ion-microprobe dating of crystal ages of zircon and allanite from these lavas and from Granophyre geothermal well cuttings, we were able to track the range of magma-production rates over the past 650 ka at Coso. In ≤230 ka rhyolites we find no evidence of protracted magma residence or recycled zircon (or allanite) from Pleistocene predecessors. A significant subset of zircon in the ~85 ka rhyolites yielded ages between ~100 and 200 Ma, requiring that generation of at least some rhyolites involves material from Mesozoic basement. Similar zircon xenocrysts are found in an ~200 ka Granophyre. The new age constraints imply that magma evolution at Coso can occur rapidly as demonstrated by significant changes in rhyolite composition over short time intervals (≤10’s to 100’s ka). In conjunction with radioisotopic age constraints from other young silicic volcanic fields, dating of Coso rhyolites highlights the fact that at least some (and often the more voluminous) rhyolites are produced relatively rapidly, but that many small-volume rhyolites likely represent separation from long-lived mushy magma bodies.
Pereira, Ronaldo Mello - One of the best experts on this subject based on the ideXlab platform.
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Rhyacian (2.23-2.20 Ga) juvenile accretion in the southern Sao Francisco craton, Brazil: Geochemical and isotopic evidence from the Serrinha magmatic suite, Mineiro belt
PERGAMON-ELSEVIER SCIENCE LTD, 2010Co-Authors: Avila, Ciro Alexandre, Teixeira Wilson, Cordani, Umberto Giuseppe, Moura, Candido Augusto Veloso, Pereira, Ronaldo MelloAbstract:The Serrinha magmatic suite (Mineiro belt) crops out in the southern edge of the Sao Francisco craton, comprising the Brito quartz-diorite, Brumado de Cima and Brumado de Baixo granodiorites, Granophyres and felsic sub-volcanic and volcanic rocks, part of which intruded into the Nazareno greenstone belt. The suite rocks have petrographic features that are consistent with magma supercooling due to the low water content combined with volatile loss, leading to crystallization of quartz and alkaline feldspar at the rims of plagioclase phenocrysts (granophyric intergrowth). The investigated rocks are sub-alkaline, calc-alkaline and show low content in rare earth elements. The U-Pb zircon crystallization ages for the Brumado de Cima granodiorite [2227 +/- 22 (23) Ma] and a coeval Granophyre [2211 +/- 22 (23) Ma], coupled with available single-zircon Pb evaporation ages for the Brito and Brumado de Baixo plutons, are significantly older than the ""Minas orogeny"" (ca. 2100-2050 Ga) of Quadrilatero Ferrifero area, eastward from the Serrinha suite. Our data establish an early Rhyacian event tectonically linked with the evolution of the Mineiro belt. The bulk Nd isotopic signature [low negative to positive epsilon(Nd(t)) values] of the Serrinha samples are consistent with the important role of Paleoproterozoic mantle components in the magma genesis. The integrated geologic, geochemical and isotopic information suggests that Paleoproterozoic evolution of the Mineiro belt initiated in a passive continental margin basin with deposition of the Minas Supergroup at ca. 2500 Ma. This stage was succeeded by outboard rupture of the oceanic lithosphere with development and coalescence of progressively younger magmatic arcs during Rhyacian time. One of the earliest arcs formed the Serrinha suite. The tectonic collage of the Serrinha and Ritapolis (2190-2120 Ma) arcs produced the NE-SW Lenheiro shear zone, resulting in mylonitization and recrystallization of both the granitoid intrusions and host rocks. As a matter of fact juxtaposition of distinct magmatic units in age and origin took place along the Lenheiros structure in this sector of the Mineiro belt. (C) 2009 Elsevier Ltd. All rights reserved
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Rhyacian (2.23-2.20 Ga) juvenile accretion in the southern Sao Francisco craton, Brazil: Geochemical and isotopic evidence from the Serrinha magmatic suite, Mineiro belt
PERGAMON-ELSEVIER SCIENCE LTD, 2010Co-Authors: Avila, Ciro Alexandre, Teixeira Wilson, Cordani, Umberto Giuseppe, Moura, Candido Augusto Veloso, Pereira, Ronaldo MelloAbstract:The Serrinha magmatic suite (Mineiro belt) crops out in the southern edge of the Sao Francisco craton, comprising the Brito quartz-diorite, Brumado de Cima and Brumado de Baixo granodiorites, Granophyres and felsic sub-volcanic and volcanic rocks, part of which intruded into the Nazareno greenstone belt. The suite rocks have petrographic features that are consistent with magma supercooling due to the low water content combined with volatile loss, leading to crystallization of quartz and alkaline feldspar at the rims of plagioclase phenocrysts (granophyric intergrowth). The investigated rocks are sub-alkaline, calc-alkaline and show low content in rare earth elements. The U-Pb zircon crystallization ages for the Brumado de Cima granodiorite [2227 +/- 22 (23) Ma] and a coeval Granophyre [2211 +/- 22 (23) Ma], coupled with available single-zircon Pb evaporation ages for the Brito and Brumado de Baixo plutons, are significantly older than the ""Minas orogeny"" (ca. 2100-2050 Ga) of Quadrilatero Ferrifero area, eastward from the Serrinha suite. Our data establish an early Rhyacian event tectonically linked with the evolution of the Mineiro belt. The bulk Nd isotopic signature [low negative to positive epsilon(Nd(t)) values] of the Serrinha samples are consistent with the important role of Paleoproterozoic mantle components in the magma genesis. The integrated geologic, geochemical and isotopic information suggests that Paleoproterozoic evolution of the Mineiro belt initiated in a passive continental margin basin with deposition of the Minas Supergroup at ca. 2500 Ma. This stage was succeeded by outboard rupture of the oceanic lithosphere with development and coalescence of progressively younger magmatic arcs during Rhyacian time. One of the earliest arcs formed the Serrinha suite. The tectonic collage of the Serrinha and Ritapolis (2190-2120 Ma) arcs produced the NE-SW Lenheiro shear zone, resulting in mylonitization and recrystallization of both the granitoid intrusions and host rocks. As a matter of fact juxtaposition of distinct magmatic units in age and origin took place along the Lenheiros structure in this sector of the Mineiro belt. (C) 2009 Elsevier Ltd. All rights reserved.Fundacao Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro (FAPERJ)Fundacao Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro (FAPERJ)[170.023/2003]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundacao de Amparo e Apoio a Pesquisa do Estado de Sao Paulo (FAPESP)[2003/12204-8]Fundacao de Amparo e Apoio a Pesquisa do Estado de Sao Paulo (FAPESP)[2004/11059-7]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Brazilian Research Council for Science and Technology (CNPq)[304300/03-9]Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Brazilian Research Council for Science and Technology (CNPq)[475673/04-2]Brazilian Research Council for Science and Technology (CNPq)[308707/2006-0]Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Paleoproterozoic Supercontinents and Global Evolution[IGCP-509]Paleoproterozoic Supercontinents and Global Evolutio
Joan Marti - One of the best experts on this subject based on the ideXlab platform.
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new late middle to early late ordovician u pb zircon ages of extension related felsic volcanic rocks in the eastern pyrenees ne iberia tectonic implications
Geological Magazine, 2019Co-Authors: Joan Marti, Luigi Augusto Solari, J M Casas, M ChichorroAbstract:Pre-Variscan basement rocks from the Pyrenees provide evidence of several magmatic episodes with complex geodynamic histories from late Neoproterozoic to Palaeozoic times. One of the most significant episodes, consisting of several granitic and granodioritic bodies and volcanic rocks, mostly pyroclastic in nature, dates from the Late Ordovician period. In the Eastern Pyrenees, this magmatism is well represented in the Ribes de Freser and Nuria areas; here, the Nuria orthogneiss and the Ribes Granophyre, both dated at c . 457–460 Ma, seem to form a calc-alkaline plutonic suite emplaced at different crustal levels. The presence of numerous pyroclastic deposits and lavas interbedded with Upper Ordovician (Sandbian–lower Katian, formerly Caradoc) sediments, intruded by the Ribes Granophyre, suggests that this magmatic episode also generated significant volcanism. Moreover, the area hosts an important volume of rhyolitic ignimbrites and andesitic lavas affected by Alpine deformation. These volcanic rocks were previously attributed to late Variscan volcanism, extensively represented in other areas of the Pyrenees. Here we present the first five laser-ablation U–Pb zircon dates for this ignimbritic succession and two new ages for the Ribes Granophyre. The ages of the ignimbrites, overlapping within error, are all 460 Ma, suggesting a genetic relationship between the plutonic and volcanic rocks and indicating that the Sandbian–Katian magmatism is much more voluminous than reported in previous studies, and possibly includes mega-eruptions linked to the formation of collapse calderas.
Jorge A Vazquez - One of the best experts on this subject based on the ideXlab platform.
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Accessory mineral U–Th–Pb ages and ^40Ar/^39Ar eruption chronology, and their bearing on rhyolitic magma evolution in the Pleistocene Coso volcanic field, California
Contributions to Mineralogy and Petrology, 2009Co-Authors: Justin I. Simon, Charles R Bacon, Jorge A Vazquez, Axel K Schmitt, Paul R. Renne, Mary R. ReidAbstract:We determined Ar/Ar eruption ages of eight extrusions from the Pleistocene Coso volcanic field, a long-lived series of small volume rhyolitic domes in eastern California. Combined with ion-microprobe dating of crystal ages of zircon and allanite from these lavas and from Granophyre geothermal well cuttings, we were able to track the range of magma-production rates over the past 650 ka at Coso. In ≤230 ka rhyolites we find no evidence of protracted magma residence or recycled zircon (or allanite) from Pleistocene predecessors. A significant subset of zircon in the ~85 ka rhyolites yielded ages between ~100 and 200 Ma, requiring that generation of at least some rhyolites involves material from Mesozoic basement. Similar zircon xenocrysts are found in an ~200 ka Granophyre. The new age constraints imply that magma evolution at Coso can occur rapidly as demonstrated by significant changes in rhyolite composition over short time intervals (≤10’s to 100’s ka). In conjunction with radioisotopic age constraints from other young silicic volcanic fields, dating of Coso rhyolites highlights the fact that at least some (and often the more voluminous) rhyolites are produced relatively rapidly, but that many small-volume rhyolites likely represent separation from long-lived mushy magma bodies.
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accessory mineral u th pb ages and 40ar 39ar eruption chronology and their bearing on rhyolitic magma evolution in the pleistocene coso volcanic field california
Contributions to Mineralogy and Petrology, 2009Co-Authors: Justin I. Simon, Charles R Bacon, Jorge A Vazquez, Axel K Schmitt, Paul R. Renne, Mary R. ReidAbstract:We determined Ar/Ar eruption ages of eight extrusions from the Pleistocene Coso volcanic field, a long-lived series of small volume rhyolitic domes in eastern California. Combined with ion-microprobe dating of crystal ages of zircon and allanite from these lavas and from Granophyre geothermal well cuttings, we were able to track the range of magma-production rates over the past 650 ka at Coso. In ≤230 ka rhyolites we find no evidence of protracted magma residence or recycled zircon (or allanite) from Pleistocene predecessors. A significant subset of zircon in the ~85 ka rhyolites yielded ages between ~100 and 200 Ma, requiring that generation of at least some rhyolites involves material from Mesozoic basement. Similar zircon xenocrysts are found in an ~200 ka Granophyre. The new age constraints imply that magma evolution at Coso can occur rapidly as demonstrated by significant changes in rhyolite composition over short time intervals (≤10’s to 100’s ka). In conjunction with radioisotopic age constraints from other young silicic volcanic fields, dating of Coso rhyolites highlights the fact that at least some (and often the more voluminous) rhyolites are produced relatively rapidly, but that many small-volume rhyolites likely represent separation from long-lived mushy magma bodies.
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alteration and remelting of nascent oceanic crust during continental rupture evidence from zircon geochemistry of rhyolites and xenoliths from the salton trough california
Earth and Planetary Science Letters, 2006Co-Authors: Axel K Schmitt, Jorge A VazquezAbstract:Abstract Rhyolite lavas and xenoliths from the Salton Sea geothermal field (Southern California) provide insights into crustal compositions and processes during continental rupture and incipient formation of oceanic crust. Salton Buttes rhyolite lavas contain xenoliths that include Granophyres, fine-grained altered rhyolites (“felsite”), and amphibole-bearing basalts. Zircon is present in lavas and xenoliths, surprisingly even in the basaltic xenoliths, where it occurs in plagioclase-rich regions interpreted as pockets of crystallized partial melt. Zircons in the xenoliths are exclusively Late Pleistocene–Holocene in age and lack evidence for inheritance. U–Th isochron ages are: 20.5− 1.2+ 1.2 ka (Granophyres), 18.3− 3.5+ 3.6 ka (felsite), 30.1− 12.4+ 14.1 ka and 9.2− 6.6+ 7.0 ka (basalts; all errors 1σ). The dominant zircon population in the rhyolite lavas yielded U–Th ages between ∼ 18 and 10 ka, with few pre-Quaternary xenocrysts present. δ18Ozircon values are lower than typical crustal basement values, thus ruling out rhyolite genesis by melting of continental crust. Moreover, δ18Ozircon values are ∼ 0.5–1.0‰ lower than compositions achievable by zircon crystallization from residual melt in equilibrium with unaltered mid-ocean ridge basalt, suggesting that basaltic crust and silicic plutons in the subsurface of the Salton Sea geothermal field isotopically exchanged with meteoric waters. This is evidence for deep-reaching hydrothermal circulation and indicates rhyolite genesis by episodic remelting of altered basalts instead of fractional crystallization of unaltered basaltic magma.
