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8. An innovative isotopic method to identify the volcanic source of distal tephra

Author

Bablon, Mathilde, primary, Nauret, François, additional, Saillard, Marianne, additional, Samaniego, Pablo, additional, Vlastélic, Ivan, additional, Hidalgo, Silvana, additional, Le Pennec, Jean-Luc, additional, Ratzov, Gueorgui, additional, Michaud, François, additional, Mothes, Patricia, additional, Liorzou, Céline, additional, and Gannoun, Abdelmouhcine, additional

Published
2023
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9. An innovative isotopic method to identify the volcanic source of distal tephra

Author

Bablon, Mathilde, Nauret, François, Saillard, Marianne, Samaniego, Pablo, Vlastélic, Ivan, Hidalgo, Silvana, Le Pennec, Jean-luc, Ratzov, Gueorgui, Michaud, François, Mothes, Patricia, Liorzou, Celine, Gannoun, Abdelmouhcine, Bablon, Mathilde, Nauret, François, Saillard, Marianne, Samaniego, Pablo, Vlastélic, Ivan, Hidalgo, Silvana, Le Pennec, Jean-luc, Ratzov, Gueorgui, Michaud, François, Mothes, Patricia, Liorzou, Celine, and Gannoun, Abdelmouhcine

Abstract

Identifying the sources of distal tephra in marine sediments or polar ice provides clues on the dynamic and large-scale impact of major volcanic eruptions. However, determination of the volcanic source of distal tephra is challenging due to size-dependent fractionation during atmospheric transport that modifies the mineral, chemical and even isotope composition of the transported and settled tephra. The composition of distal fine ash may thus be different from the coarser proximal products of the same eruption. Identifying the volcanic source of distal ash using the compositional data may therefore prove difficult. To get around this modification of distal composition, we propose here a new isotopic method to identify the source of distal tephra that is not based on raw transport-dependent isotope ratios but on two-dimension Pb isotope mixing lines, which account for atmospheric fractionation processes. To demonstrate the robustness of our method, we used the extensive database of Pb isotope compositions of volcanic products from the Northern Andean arc, to which we append 68 new Pb isotopic analyses obtained on proximal and distal eruptive tephra. We show for the first time that proximal products define a straight line in the 208Pb/206Pb-207Pb/206Pb space, whose equation is specific to each volcanic source. We then show that distal co-genetic tephra plot on the same line as proximal products, implying that the isotopic lines are robust fingerprints of volcanic sources that do not depend on the age, mineral assemblage, and nature of the emitted products. This new method uses bulk rock analyses and therefore provides a new perspective on distal tephra correlation and source identification in the Andes and probably other volcanic arcs with significant Pb isotopic variations.

Published
2023
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10. Marine tephra offshore Ecuador and Southern Colombia: first trench-to-arc correlations and implication for the magnitude of major eruptions

Author

Bablon, Mathilde, Saillard, Marianne, Quidelleur, Xavier, Samaniego, Pablo, Ratzov, Gueorgui, Michaud, François, Le Pennec, Jean-Luc, Nauret, François, Siani, Giuseppe, Santamaria, Santiago, Collot, Jean Yves, Proust, Jean-Noël, Devidal, Jean-Luc, Orange, François, Liorzou, Céline, Vallejo, Silvia, Hidalgo, Silvana, Migeon, Sébastien, Mothes, Patricia, Géoazur (GEOAZUR 7329), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), Géosciences Paris Saclay (GEOPS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Laboratoire Magmas et Volcans (LMV), Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement et la société-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne (UCA)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne (UCA), Sorbonne Université (SU), Geo-Ocean (GEO-OCEAN), Université de Bretagne Sud (UBS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), IRD, Jakarta, Wisma Anugraha Jalan Taman Kemang, b IRD, Jakarta, Wisma Anugraha Jalan Taman Kemang 32B, Jakarta selatan, Instituto de Investigación Geológico y Energético (IIGE), Géosciences Rennes (GR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), CCMA - Centre Commun de Microscopie Appliquée, Université Côte d'Azur (UCA), and Instituto Geofisico - Escuela Politecnica Nacional (IGEPN)

Subjects
[SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology, [SDU.STU.PE]Sciences of the Universe [physics]/Earth Sciences/Petrography, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences
Abstract

International audience; Major eruptions in the Andes are mainly characterized by the emission of large volumes of gas and volcanic ash. The plume may reach the stratosphere and be transported by winds. In Ecuador, the prevailing winds are westward, and the volcanic ash, also called tephra, is transported towards the Pacific Ocean. Vallejo (2011) studied tephra layers present in marine terraces and proposed a first draft of the identification of their source in the Cordillera. However tephras deposited onshore may have been remobilized, eroded or covered by younger deposits. There are therefore several interests in studying tephras recorded in marine sediments : it allows to (1) know the age and source of major eruptions whose products reached the coast, (2) know the distribution of fallout from each major eruption, (3) estimate the volume of largest events, (4) participate to better assess the current volcanic hazard, and (5) provide temporal constraints on continental or marine sediments that cannot be dated by radiocarbon. To study the tephra layers recorded in marine sediments I have described the glass morphology and the mineralogy of tephra beds. To determine the source of the eruptions, I have used data published onshore (e.g., Hidalgo et al., 2008; Hall et Mothes, 2008; Robin et al., 2010). As each volcano has its own geochemical signature when we combine major, trace and isotope data, I compared them with geochemical analyses performed on distal tephra recorded in marine sediments. To determine the age of distal tephra beds, we have performed 14C ages on foraminifera present above and below the bed for tephra emitted during the past 50 ka, and d18O and biostratigraphy for the older deposits. In this presentation, I first presented our results obtained on cores collected during Amadeus (2005) and Atacames (2012) oceanic campaigns along the Ecuadorian margin, and recently published (Bablon et al., 2022). We have sampled 28 tephra layers, from coring sites that cover 5 degrees of latitude, from the southern half of Ecuador to southern Colombia. We observed four main lithofacies: isolated lenses that typical of bioturbation, layers with sharp and sometimes diffuse contacts in the upper part that correspond to primary deposits of tephra fallout, and successions of thin laminated layers that correspond to tephra layers reworked by turbidity currents, and that have not been sampled. Volcanic glass shards have various morphologies depending on the density of vesicles and their deformation, such as block-shaped glass without bubbles, pumice-shaped glass, or glass with completely elongated bubbles. The glass morphology of each tephra allows us to propose a first correlation of layers between each marine core. Concerning the geochemistry, glasses are mostly rhyolitic and belong to the low potassic series typical of the volcanic front, and to high potassic series typical of the eastern cordillera. This distinction between the eastern and western cordillera is also found in their trace element signature. To identify the source volcano, we used Sr and Pb isotopes. On The compositional fields of the volcanoes products overlap little and thus allows us to refine the correlations. We show that distal marine tephra come from the Cerro Machin in Colombia, and from Pichincha, Atacazo, and Cotopaxi volcanoes in Ecuador. Together with the determination of the sources, the radiocarbon dating of sediments allowed us to show that the oldest tephras belonged to the about 8 ka eruption of Cotopaxi, and the youngest correspond to the 10th century eruption of Pichincha. Using the spatial distribution of tephra, we made isopach maps of the fourth major eruptions of Pichincha, Atacazo and Cotopaxi, and we estimated their volumes. They vary between 1.3 and 6 km3, which corresponds to volcanic explosivity indexes of 5, thus eruptions which would be particularly destructive today. A perspective for our work is to study of turbidite beds present in the Holocene cores along the coast. As such deposits are emplaced during major earthquakes, and we can therefore use their correlation to identify past seiscally active areas.Unfortunately, some major Holocene eruptions described in the Cordillera and constitute stratigraphic markers have not been recorded in marine sediments. Tephra layers may have been destructed during drilling such as the very young 700 BP eruption of Quilotoa, they may have been dispersed by ocean currents, or tephra were not present in the cores du to a restricted distribution of deposits, for example for the 3000 BP eruption of Cuicocha (Vallejo, 2011).In the second part of my presentation, I focused on another case study, performed at ODP site 1239, above the Carnegie Ridge. This core is much deeper as it reaches 500 m, and sediments deposited about 10 Myr ago. It contains 24 tephra layers, and we focused on the thickest, 18 cm-thick at 7 m deep (Schipboard Scientific Party, 2003; Bablon et al., 2020). The main volcanic structure that could be the source of such a thick deposit is the Chalupas caldera, located in the Eastern Cordillera, near Cotopaxi volcano. About 50 km southwest of the caldera, we sampled the ignimbrite and dated the glass shards at 216 +/- 5 ka using the K-Ar dating method applied on glass shards. In order to verify if the ignimbrite and marine tephra of ODP Site 1239 belong to the same eruption, we have compared their geochemistry, and we have shown that their major and trace element contents are very close. To check the reliability of this land-sea correlation, we have also compared their ages. Variations of d18O are related to climate changes linked to the Earth's orbital forcing. We then used d18O data available to know the age of sediments as a function of depth. The stratigraphic position of the tephra layer corresponds to the 7d isotopic stage that occured at 220 ka, in agreement with our K-Ar age obtained onland. We then have shown that the 216 +/- 5 ka eruption of Chalupas is the largest of the Quaternary in northern Andes, with products that reached more than 1000 km from their source. Our land-sea correlation also allow to provide an independant temporal constraint to the regional d18O records.

Published
2022

11. Identification d’évènements extrêmes passés à partir de l’analyse et de corrélations terre-mer de téphras déposés au large de l'Équateur et du sud de la Colombie

Author

Bablon, Mathilde, Michaud, François, Saillard, Marianne, Ratzov, Gueorgui, Le Pennec, Jean-Luc, Nauret, François, Samaniego, Pablo, Collot, Jean Yves, Proust, Jean-Noël, Devidal, Jean-Luc, Orange, François, Liorzou, Céline, Vallejo Vargas, Silvia, Hidalgo, Silvana, Migeon, S., Géoazur (GEOAZUR 7329), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), Sorbonne Université (SU), Geo-Ocean (GEO-OCEAN), Université de Bretagne Sud (UBS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD Indonésie), Institut de Recherche pour le Développement (IRD), Laboratoire Magmas et Volcans (LMV), Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement et la société-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne (UCA)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne (UCA), Géosciences Rennes (GR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), Centre Commun de Microscopie Appliquée (CCMA), Université de Nice Sophia-Antipolis (UNSA), Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), and Instituto Geofisico - Escuela Politecnica Nacional (IGEPN)

Subjects
[SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology, [SDU.STU.PE]Sciences of the Universe [physics]/Earth Sciences/Petrography, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences
Abstract

National audience; L’arc volcanique nord andin, induit par le plongement de la plaque océanique Nazca sous le continent sud-américain, s’étend de la zone centrale de l’Équateur à la zone centrale de la cordillère colombienne. En Équateur, l’arc est composé de plus de 80 édifices volcaniques actifs durant le Quaternaire, ce qui correspond à la plus forte densité volcanique de la Cordillère des Andes. Le risque volcanique est donc particulièrement élevé pour les populations et les infrastructures, et il est nécessaire de documenter les éruptions passées pour mieux anticiper les crises volcaniques futures.Les carottes marines collectées lors des campagnes océanographiques Amadeus (2005) et Atacames (2012) ont mis en évidence la présence de niveaux de cendres volcaniques (téphras) enregistrés dans les séquences sédimentaires marines au large de l’Équateur et du sud de la Colombie. Ces téphras, émis lors d’éruptions volcaniques majeures et transportés par les courants atmosphériques, se sont déposés au cours de l’Holocène (depuis moins de 12 000 ans). Leur préservation dans les sédiments marins constitue une archive unique des éruptions majeures récentes de l’arc volcanique des Andes du nord dont les produits ont atteint l’Océan Pacifique. Afin de déterminer la source volcanique de ces téphras, nous avons estimé leur âge (datations 14C sur des coquilles de foraminifères planctoniques situées au-dessus et/ou en dessous des cendres), caractérisé l’assemblage minéralogique des niveaux de cendres, la morphologie des échardes de verre (Microscope Electronique à Balayage), leur teneur en éléments majeurs et traces (microsonde électronique, LA-ICP-MS, ICP-AES), ainsi que leurs rapports isotopiques du Sr et du Pb (MC-ICP-MS), que nous avons ensuite comparé aux produits volcaniques des éruptions documentées dans la Cordillère. Cette étude a permis d’établir une première corrélation terre-mer des dépôts volcaniques, ce qui n’avait jamais été fait dans cette région. Elle permet de montrer que (1) malgré une densité de volcan exceptionnelle en Équateur, il est possible de retrouver la source de retombées distales à partir de leur signature géochimique, (2) au moins 12 éruptions majeures d’Indice d’Explosivité Volcanique ≥5 se sont produites au cours des derniers 8 ka, et ont été associées à l’activité des volcans Guagua Pichincha, Atacazo-Ninahuilca, Cotopaxi et Cerro Machín, et (3) les épaisseurs des retombées distales, bien que probablement biaisées par les courants marins, la compaction, la bioturbation et les déstabilisations gravitaires, améliorent les modèles de distribution spatiale des dépôts et les estimations des volumes de produits émis. Nous obtenons des volumes de téphras variant entre 1,3 et 6,0 km3. Ces données permettent une meilleure évaluation des VEI et de l’impact des éruptions majeures passées, et participent ainsi à une meilleure connaissance des risques volcaniques actuels en Équateur. Par ailleurs, les niveaux de téphras les plus épais sont associés à des réflecteurs sur les enregistrements sismiques, et de nombreux téphras sont intercalés avec des séquences turbiditiques mises en place lors de séismes anciens. Le travail que nous avons réalisé sur les téphras constitue donc une étude prometteuse qui pourrait permettre à terme d’établir précisément l’âge et la récurrence des séismes majeurs qui ont affecté la côte équatorienne au cours de l’Holocène, ainsi que la distribution spatiale des dépôts turbiditiques associés.

Published
2022

12. Holocene Marine Tephra Offshore Ecuador and Southern Colombia: First Trench‐to‐Arc Correlations and Implication for Magnitude of Major Eruptions

Author

Bablon, Mathilde, primary, Ratzov, Gueorgui, additional, Nauret, François, additional, Samaniego, Pablo, additional, Michaud, François, additional, Saillard, Marianne, additional, Proust, Jean‐Noël, additional, Le Pennec, Jean‐Luc, additional, Collot, Jean‐Yves, additional, Devidal, Jean‐Luc, additional, Orange, François, additional, Liorzou, Céline, additional, Migeon, Sébastien, additional, Vallejo, Silvia, additional, Hidalgo, Silvana, additional, Mothes, Patricia, additional, and Gonzalez, Miguel, additional

Published
2022
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13. Holocene marine tephra offshore Ecuador and Southern Colombia: First trench‐to‐arc correlations and implication for magnitude of major eruptions

Author

Bablon, Mathilde, Ratzov, Gueorgui, Nauret, François, Samaniego, Pablo, Michaud, François, Saillard, Marianne, Proust, Jean‐noël, Le Pennec, Jean‐luc, Collot, Jean‐yves, Devidal, Jean‐luc, Orange, François, Liorzou, Celine, Migeon, Sebastien, Vallejo, Silvia, Hidalgo, Silvana, Mothes, Patricia, Gonzalez, Miguel, Bablon, Mathilde, Ratzov, Gueorgui, Nauret, François, Samaniego, Pablo, Michaud, François, Saillard, Marianne, Proust, Jean‐noël, Le Pennec, Jean‐luc, Collot, Jean‐yves, Devidal, Jean‐luc, Orange, François, Liorzou, Celine, Migeon, Sebastien, Vallejo, Silvia, Hidalgo, Silvana, Mothes, Patricia, and Gonzalez, Miguel

Abstract

Tephra layers preserved in marine sediments are strong tools to study the frequency, magnitude and source of past major explosive eruptions. Thirty-seven volcanoes from the Ecuadorian and Colombian arc, in the northern Andes, experienced at least one eruption during the Holocene. The volcanic hazard is therefore particularly high for the populated areas of the Andes and in particular cases for the coastal region, and it is crucial to document such events to improve hazard assessment. The age and distribution of deposits from major Holocene eruptions have been studied in the Cordillera, but no descriptions of distal fallouts have been published. In this study we focused on 28 Holocene tephra layers recorded in marine sediment cores collected along the northern Ecuador - southern Colombia margin. New lithological, geochemical and isotope data together with 14C datings on foraminifers allow us to determine the age and volcanic source of marine tephra, and to propose a first land-sea correlation of distal tephra fallouts. We show that at least seven explosive eruptions from Guagua Pichincha, Atacazo-Ninahuilca, Cotopaxi, and Cerro Machín volcanoes left tephra deposits recorded in marine cores over 250 km away from their source. Volume estimates of emitted tephra range between 1.3 and 6.0 km3 for the 10th century Guagua Pichincha, ∼5 ka Atacazo-Ninahuilca, ∼6.7 and ∼7.9 ka Cotopaxi events, suggesting that they were eruptions of Volcanic Explosivity Index of 5. The distribution of these deposits also brings new constraints for a better evaluation of the volcanic hazard in Ecuador. Key Points We propose a first land-sea correlation of distal Holocene tephra off Ecuador based on 14C age and geochemical data Products from at least seven explosive Holocene eruptions in Ecuador and south Colombia reached the Pacific Ocean Volumes of tephra emitted by largest eruptions vary between 1.3 and 6.0 km3, suggesting they were VEI-5 eruptions Plain Language Summary During major explosi

Published
2022
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16. ANR COYOTES project (Comoros & maYotte: vOlcanism, TEctonics and Seismicity)

Author

Thinon, Isabelle, Lemoine, Anne, Feuillet, Nathalie, Michon, Laurent, Leroy, Sylvie, Autin, Julia, Bachèlery, Patrick, Battaglia, Jean, Bernard, Julien, Bernard, Pascal, Bertil, Didier, Lemarchand, Arnaud, Briole, Pierre, Chamot-Rooke, Nicolas, Clouard, Valérie, Crawford, Wayne, De Michele, Marcello, Deplus, Christine, Di Muro, Andrea, Doubre, Cécile, Famin, Vincent, Grunberg, Marc, Gurioli, Lucia, Jacques, Eric, Jorry, Stéphan, Maggi, Alesia, Le Maire, Pauline, Martelet, Guillaume, Mercury, Nicolas, Moreira, Manuel, Nauret, François, Paquet, Fabien, Peyrefitte, Aurelie, Poort, Jeffrey, Quidelleur, Xavier, Satriano, Claudio, Saurel, Jean-Marie, Sauter, Daniel, Van Der Woerd, Jerome, Zaragosi, Sébastien, Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Laboratoire GéoSciences Réunion (LGSR), Université de La Réunion (UR)-Institut de Physique du Globe de Paris, Institut des Sciences de la Terre de Paris (iSTeP), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Ecole et Observatoire des Sciences de la Terre (EOST), Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Dynamique globale (IPGS) (IPGS-DG), Institut de physique du globe de Strasbourg (IPGS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA), Laboratoire Magmas et Volcans (LMV), Centre National de la Recherche Scientifique (CNRS)-Université Jean Monnet [Saint-Étienne] (UJM)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement et la société-Institut national des sciences de l'Univers (INSU - CNRS), Laboratoire de géologie de l'ENS (LGE), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA), Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Institut Galien Paris-Saclay (IGPS), Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut des Sciences de la Terre d'Orléans - UMR7327 (ISTO), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Magma - UMR7327, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Géosciences Paris Saclay (GEOPS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Strasbourg (UNISTRA), Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), ANR, BRGM, ANR: COYOTES,COYOTES (Comoros & maYotte: vOlcanism, TEctonics and Seismicity), Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet [Saint-Étienne] (UJM)-Institut de Recherche pour le Développement et la société-Université Clermont Auvergne (UCA)-Centre National de la Recherche Scientifique (CNRS)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC), and Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Comoros archipelago, Volcanism, [SDU]Sciences of the Universe [physics], Seismo-volcanic crisis, [SDE]Environmental Sciences, Mayotte, Active deformation, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Mozambique Channel, Tectonic, [SDU.STU.AG]Sciences of the Universe [physics]/Earth Sciences/Applied geology
Abstract

International audience; In order to understand the unprecedented underwater telluric event of the Mayotte Seismo-Volcanic (MSV) crisis (2018-2020), it appears essential to reach a critical level of knowledge on the evolution of the seismicity, volcanic activity and geodetic deformation, but also on the geodynamic context. This includes the kinematics and the characterization of the lithospheric and crustal structures, on both short- and long-term and regional and local scales. Towards this goal, the COYOTES project aims to better understand the regional geodynamic and geological context of the northern Mozambique Channel. The objectives are to understand the distribution of active and recent deformations around the Comoros Archipelago, in particular the Mayotte Island, to image the crustal structuration and to study the recent tectono-sedimentary evolution. Both the link with the East African rift system and the role of Mesozoic inherited structures in the spatial distribution of present-day deformation associated to the MSV crisis will be investigated. This updated geodynamic and geological knowledge will be used to improve the assessment of the volcanic and seismic hazards of the Comoros archipelago and especially around Mayotte. The main work-packages are 1) Current seismic sequence, deformation and kinematics; 2) Recent and active volcanism and tectonics in the Comoros archipelago; 3) Long-term geodynamics: Regional structuration and inheritance. It will integrate new onshore and offshore acquisitions of geological and geophysical data, their interpretation as well as modelling.The COYOTES project (http://www.geocean.net/coyotes/doku.php?id=start) is funded by the ANR (French Agence Nationale de la Recherche) for the period 2020-2024, involving three thesis, one post-doc and more than 30 scientists from the BRGM, IPGS/EOST, IPGP, IsTep, ENS, La Réunion University, EPOC, Ifremer, SHOM, GEOPS, LMV, GET, ISTO, OVPF, .... The project is linked with the SISMAORE oceanographic campaign that will occur on the R/V Pourquoi Pas? from December 2020 to February 2021.

Published
2020

17. First identification, geochemical characterization, and land-sea correlations of Holocene marine distal tephra from the Ecuadorian arc

Author

Bablon, Mathilde, primary, Nauret, François, additional, Samaniego, Pablo, additional, Devidal, Jean-Luc, additional, Ratzov, Gueorgui, additional, Michaud, François, additional, Saillard, Marianne, additional, Orange, François, additional, Proust, Jean-Noel, additional, Le Pennec, Jean-Luc, additional, Liorzou, Céline, additional, Vallejo, Silvia, additional, Mothes, Patricia, additional, and Hidalgo, Silvana, additional

Published
2021
Full Text
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19. Pb-Sr isotope temporal variations on juvenile ash samples from the last eruptive period of Tungurahua volcano (1999-2016)

Author

Sainlot, N., Vlastélic, Ivan, Samaniego, Pablo, Bernard, B., Nauret, François, Hidalgo, S., Laboratoire Magmas et Volcans (LMV), Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet [Saint-Étienne] (UJM)-Institut de Recherche pour le Développement et la société-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Institut national des sciences de l'Univers (INSU - CNRS), Instituto de Microelectrònica de Barcelona (IMB-CNM), Centro Nacional de Microelectronica [Spain] (CNM)-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Institut de Recherche pour le Développement et la société-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS), and Jouhannel, Sylvaine

Subjects
[SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, [SDU.STU.GC] Sciences of the Universe [physics]/Earth Sciences/Geochemistry, [SDU.STU.VO] Sciences of the Universe [physics]/Earth Sciences/Volcanology, [SDU.STU.PE]Sciences of the Universe [physics]/Earth Sciences/Petrography, [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology, [SDU.STU.PE] Sciences of the Universe [physics]/Earth Sciences/Petrography, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2019

20. Insights in Ecuadorian magma sources: from whole-rock geographical trends to single mineral isotope compositions

Author

Ancellin, Marie-Anne, Vlastélic, Ivan, Samaniego, Pablo, Nauret, François, Gannoun, Abdelmouhcine, Hidalgo, Silvana, Laboratoire Magmas et Volcans (LMV), Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet [Saint-Étienne] (UJM)-Institut de Recherche pour le Développement et la société-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Institut national des sciences de l'Univers (INSU - CNRS), instituto Geofísico, Escuela Politécnica Nacional (EPN), Jouhannel, Sylvaine, Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Institut de Recherche pour le Développement et la société-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), and Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, [SDU.STU.GC] Sciences of the Universe [physics]/Earth Sciences/Geochemistry
Abstract

International audience; Ecuadorian magmas result from processing through a thick crust a heterogeneous range of primitive melts. This results in a complex geochemical signal at the surface, where source and processes footprints are intricate. We propose here to compare two approaches at different scales. The first one aims to understand the general trends in Ecuadorian magmatism looking at the geochemistry of whole-rocks at the scale of the arc to decipher continental crust and slab component imprints. The second approach is based on the idea that whole-rock compositions represent rough averages of all processes taking place from source to eruption, but that those processes could be sorted out studying different minerals present in the rocks. For the first approach, 71 samples were analysed for major and trace elements as well as Sr, Nd and Pb isotopes to complete the existing geochemical dataset. This study confirms the already identified across-arc geochemical trends described in the literature that reflect the decrease in mantle melting and the slab dehydration away from the trench. Along-arc geochemical trends were identified for the first time, especially marked in the front arc which encompasses 99% and 71% of the total variation in 206Pb/204Pb and 87Sr/86Sr ratios of Quaternary Ecuadorian volcanics. These trends suggest (1) more extensive crustal contamination of magma in the southern part (up to 14%); and (2) a changing nature of metasomatism in the subarc mantle wedge with the aqueous fluid/siliceous slab melt ratio decreasing away from 0.5°S. Subduction of a younger and warmer oceanic crust in the Northern part of the arc might promote slab melting. Conversely, the subduction of a colder oceanic crust south of the Grijalva Fracture Zone and higher crustal assimilation lead to the reduction of slab contribution in magmas erupted in the southern part of the arc. The second approach focuses on one volcanic edifice, the Guagua Pichincha. 42 minerals (amphibole, plagioclase, pyroxene) were picked from two dacite samples and analysed for major and trace elements, and Pb isotopes. Early crystallized, high-Al amphiboles with Al2O3>=9.8 wt.% and Eu/Eu*>0.7 have the lowest and most heterogeneous 206Pb/204Pb (18.816-18.999), whereas plagioclases have the highest and most homogeneous 206Pb/204Pb (19.003-19.023). Low-Al amphiboles and pyroxenes display intermediate compositions and variability (18.934-19.007). The large isotopic disequilibrium between mineral phases and whole-rocks show that a rock sample is a complex mix of minerals and melts recording different parts of the magmatic system. Trace element and isotopic data show that primitive melts feeding the young Guagua Pichincha are heterogeneous. These melts seem to be contaminated by the Western Cordillera basement comprised by accreted ocean terrains on their way to surface. Minerals are precious insights of magmas' history as mass balance calculation reveals that in the case of these 2 dacites, the whole-rock Pb isotope composition is completely buffered by the matrix composition. Combining these two scales allows us to better understand the scale of mantle heterogeneity under the Ecuadorian arc and the significance of whole-rock compositions in arc magmas.

Published
2019

21. The temporal evolution of the Ecuadorian volcanic arc during the last 1 Ma

Author

Samaniego, Pablo, Bablon, Mathilde, Ancellin, Marie-Anne, Hidalgo, Sylvana, Quidelleur, Xavier, Vlastélic, Ivan, Nauret, François, Le Pennec, Jean-Luc, Martin, Hervé, Narvaez, Diego, Rose-Koga, Estelle, Santamaria, Santiago, Liorzou, Céline, Gannoun, Abdelmouhcine, Laboratoire Magmas et Volcans (LMV), Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet [Saint-Étienne] (UJM)-Institut de Recherche pour le Développement et la société-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Institut national des sciences de l'Univers (INSU - CNRS), Géosciences Paris Sud (GEOPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Universidad Tecnologica Equinoccial [Quito, Ecuador] (UTE), ROSE-KOGA, Estelle F., Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Institut de Recherche pour le Développement et la société-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), and Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, [SDU.STU.GC] Sciences of the Universe [physics]/Earth Sciences/Geochemistry, [SDU.STU.VO] Sciences of the Universe [physics]/Earth Sciences/Volcanology, [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology, [SDU.STU.MI] Sciences of the Universe [physics]/Earth Sciences/Mineralogy, [SDU.STU.MI]Sciences of the Universe [physics]/Earth Sciences/Mineralogy
Abstract

International audience; When looking at the whole Andean arc, one of the most striking characteristics of the Ecuadorian segment of the Northern Volcanic Zone (NVZ) is the large number (up to 85) of Quaternary volcanic centres. This arc segment results from the subduction of the Nazca plate below the South-American lithosphere that also includes the aseismic Carnegie ridge and the Grijalva Fracture zone. The Ecuadorian volcanoes are distributed along the Western Cordillera, the Interandean Valley, the Eastern Cordillera and the subandean zone. As a result, the volcanic arc is up to 120 km-large and develops on a thick (up to 50 km) and heterogeneous crust consisting in oceanic-like terrains to the West and continental-like terrains to the East. The geochemical studies performed over the last 20 years allow us to constrain three main geochemical patterns. Firstly, an across-arc zonation of incompatible trace elements that reflects a progressive decrease of both the subduction component of magmas and the mantle melting away from the trench. Secondly, it exists a marked difference in Sr-Nd-Pb-O isotopic signature that correlates with the different crustal structures of both Cordilleras. Thirdly, an overall adakitic signature that has been interpreted either in terms of slab partial melting and the subsequent metasomatic reactions in the mantle wedge or as due to lower crustal processes associated with high-pressure fractionation and/or melting. More recently, Ancellin et al. (2017) and Narvaez et al. (2018) pointed out significant along-arc geochemical variations on whole-rocks and olivine-hosted melt inclusions, which they related to a change in the subduction component, specifically the ratio between the aqueous fluids vs. siliceous melts ascending through an interacting with the mantle wedge. However, one of the unresolved key questions is the timing of the Ecuadorian arc development. In order to overcome this lack of chronological data, we designed an ambitious project focusing on three main across-arc transects. More than 100 new, high-quality, K-Ar ages were obtained on groundmass samples. It appears that, if in northern part of the arc, some edifices emplaced at ca. 1-1.2 Ma, most volcanoes developed during the last 500 ka. These new data evidence that the Ecuadorian arc has acquired its current configuration in relatively recent times, as a result of the southern migration of the Grijalva Fracture Zone (Bablon et al., 2019). These chronological data help to better constrain the geochemical evolution described at several edifices of the arc and allow us to discriminate the role of both the subduction and crustal processes in continental arc magma genesis, highlighting the fact that these processes are not mutually exclusive.

Published
2019

23. Explosive eruption, flank collapse and megatsunami at Tenerife ca. 170 ka

Author

Paris, Raphael, Bravo, Juan J. Coello, González, María E. Martín, Kelfoun, Karim, Nauret, François, Laboratoire Magmas et Volcans (LMV), Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet [Saint-Étienne] (UJM)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), ANR-10-LABX-0006,CLERVOLC,Clermont-Ferrand centre for research on volcanism(2010), ANR-16-IDEX-0001,CAP 20-25,CAP 20-25(2016), Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), and Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Science, [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology, Article
Abstract

Giant mass failures of oceanic shield volcanoes that generate tsunamis potentially represent a high-magnitude but low-frequency hazard, and it is actually difficult to infer the mechanisms and dynamics controlling them. Here we document tsunami deposits at high elevation (up to 132 m) on the north-western slopes of Tenerife, Canary Islands, as a new evidence of megatsunami generated by volcano flank failure. Analyses of the tsunami deposits demonstrate that two main tsunamis impacted the coasts of Tenerife 170 kyr ago. The first tsunami was generated during the submarine stage of a retrogressive failure of the northern flank of the island, whereas the second one followed the debris avalanche of the subaerial edifice and incorporated pumices from an on-going ignimbrite-forming eruption. Coupling between a massive retrogressive flank failure and a large explosive eruption represents a new type of volcano-tectonic event on oceanic shield volcanoes and a new hazard scenario., Oceanic shield volcanoes flank failures can generate large tsunamis. Here, the authors provide evidence that two tsunamis impacted the coast of Tenerife 170 Ma, the first generated by volcano flank failure and the second following a debris avalanche of the edifice during an on-going ignimbrite-forming eruption.

Published
2017

24. Across-arc versus along-arc Sr-Nd-Pb isotope variations in the Ecuadorian volcanic arc

Author

Ancellin, Marie-Anne, Samaniego, Pablo, Vlastélic, Ivan, Nauret, François, Gannoun, Adbelmouhcine, Hidalgo, Silvana, Laboratoire Magmas et Volcans (LMV), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement et la société-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Université Jean Monnet [Saint-Étienne] (UJM), instituto Geofísico, Escuela Politécnica Nacional (EPN), ANR-10-LABX-0006,CLERVOLC,Clermont-Ferrand centre for research on volcanism(2010), ANR-16-IDEX-0001,CAP 20-25,CAP 20-25(2016), Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Institut de Recherche pour le Développement et la société-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet [Saint-Étienne] (UJM)-Institut de Recherche pour le Développement et la société-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), and Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Institut national des sciences de l'Univers (INSU - CNRS)

Subjects
[SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology
Abstract

Previous studies of the Ecuadorian arc (1 degrees N-2 degrees S) have revealed across-arc geochemical trends that are consistent with a decrease in mantle melting and slab dehydration away from the trench. The aim of this work is to evaluate how these processes vary along the arc in response to small-scale changes in the age of the subducted plate, subduction angle, and continental crustal basement. We use an extensive database of 1437 samples containing 71 new analyses, of major and trace elements as well as Sr-Nd-Pb isotopes from Ecuadorian and South Colombian volcanic centers. Large geochemical variations are found to occur along the Ecuadorian arc, in particular along the front arc, which encompasses 99% and 71% of the total variations in Pb-206/Pb-204 and Sr-87/Sr-86 ratios of Quaternary Ecuadorian volcanics, respectively. The front arc volcanoes also show two major latitudinal trends: (1) the southward increase of Pb-207/Pb-204 and decrease of Nd-143/Nd-144 reflect more extensive crustal contamination of magma in the southern part (up to 14%); and (2) the increase of Pb-206/Pb-204 and decrease of Ba/Th away from similar to 0.5 degrees S result from the changing nature of metasomatism in the subarc mantle wedge with the aqueous fluid/siliceous slab melt ratio decreasing away from 0.5 degrees S. Subduction of a younger and warmer oceanic crust in the Northern part of the arc might promote slab melting. Conversely, the subduction of a colder oceanic crust south of the Grijalva Fracture Zone and higher crustal assimilation lead to the reduction of slab contribution in southern part of the arc.

Published
2017

26. Oblique nonvolcanic seafloor spreading in Lena Trough, Arctic Ocean

Author

Snow, J. E., Hellebrand, Eric, von Der Handt, Annette, Nauret, François, Gao, Yongjun, Schenke, Hans-Werner, Department of Geosciences [Houston], University of Houston, Max-Planck-Institut für Chemie (MPIC), Max-Planck-Gesellschaft, Department of Geology and Geophysics, University of Hawai‘i [Mānoa] (UHM), Institute of Geoscience, Albert-Ludwigs-Universität Freiburg, Laboratoire Magmas et Volcans (LMV), Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet [Saint-Étienne] (UJM)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Department of Bentho-pelagic processes, Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung (AWI), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), and Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS)

Subjects
mid-ocean ridge, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, [SDE.MCG]Environmental Sciences/Global Changes, continental rift, seafloor spreading, mantle exposure, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2011

28. Origin of MORB enrichment and relative trace element compatibilities along the Mid-Atlantic Ridge between 10° and 24°N

Author

Hémond, Christophe, Hofmann, Albrecht W., Vlastélic, Ivan, Nauret, François, Domaines Océaniques (LDO), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Observatoire des Sciences de l'Univers-Institut d'écologie et environnement-Centre National de la Recherche Scientifique (CNRS), Max-Planck-Institut für Chemie (MPIC), Max-Planck-Gesellschaft, Institut de Physique du Globe de Paris (IPGP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Magmas et Volcans (LMV), Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet [Saint-Étienne] (UJM)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), and Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Mid-Atlantic Ridge, enrichment, mantle isochron, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, [SDE.MCG]Environmental Sciences/Global Changes, trace elements, compatibility, MORB, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography
Abstract

International audience; The origin of chemically and isotopically enriched basalts along mid-ocean ridges (E-MORB) has been the subject of recent interest, particularly in cases where they are not related to a specific mantle plume. We present new isotope dilution analyses for Th, U, La, Ce, and Pb in 26 mostly glassy tholeiite samples dredged from the Mid-Atlantic Ridge (MAR) between 10° and 24°N. We interpret these data in combination with other previously published trace element data and isotope ratios for the same samples. We focus on the region at 14°–15°N, where incompatible trace element abundances are enriched by as much as factors of 40, relative to the depleted basalts found to the north and the south of this region. We invoke simple recycling of alkali basalts found on oceanic islands and seamounts as an alternative E-MORB origin to a recently published metasomatic enrichment model. A small amount of recycled alkali basalt is added to the local depleted mantle peridotite. Melting of such mixed sources can produce the observed E-MORB at 14°–15°N MAR and elsewhere. The bulk partition coefficients of Nb, Ta, K, and Pb (relative to other trace elements) are geochemically important because these elements are widely used as tracers of source chemistry. We evaluate their partitioning using simple log-log plots, and we compare the 10°–24° MAR basalts with a similar suite from the CIR 18°–20°S. In both suites, Nb (bulk) partitioning is close to Th, and Pb is close to Pr. Tantalum partitioning is also very close to Nb in the MAR setting but between U and K in the CIR setting. Potassium is slightly more compatible than U in the MAR suite but less compatible in the CIR setting. Thus, although the bulk partition coefficients of these elements do vary slightly in different regions, their overall consistency is remarkable considering that the partitioning of the individual elements is governed by different mineral phases.

Published
2006

29. Extreme 230Th excesses in magnesian andesites from Baja California

Author

Nauret, François, Hémond, Christophe, Maury, René C., Aguillon-Robles, Alfredo, Guillou, Hervé, and Le Faouder, Antoine

Subjects
*MAGNETES, *ANDESITE, *PLEISTOCENE Epoch, *ISOTOPE geology, *TRACE elements
Abstract

Abstract: Four Late Pleistocene magnesian andesites (locally called “bajaites”) from Baja California have been dated by the unspiked K–Ar method and analyzed for major, trace elements and Sr, Nd, Pb, Th and U isotopes. They display very large 230Th excesses (50% to 120%) relative to 238U. They also have very high Ba and Sr contents and Sr/Y and La/Yb ratios, together with suprachondritic Nb/Ta ratios (22 to 26). From correlations between 230Th excess and major elements, trace element and isotopic ratios, we show that the unusual geochemical signature of these lavas can be ascribed to very low partial melting degrees of a mantle source containing residual rutile. This mantle source derived from interactions between the Baja California lithospheric mantle and older magnesian andesite melts carrying a sedimentary component, which were formed during the Late Miocene opening of the Baja California asthenospheric window. During the Quaternary, this metasomatized source experienced dehydration melting triggered by the hot thermal regime due to the uprise of the subslab Pacific asthenosphere beneath Baja California and the Gulf of California. [Copyright &y& Elsevier]

Published
2012
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30. Explosive eruption, flank collapse and megatsunami at Tenerife ca. 170 ka.

Author

Paris R, Bravo JJC, González MEM, Kelfoun K, and Nauret F

Abstract

Giant mass failures of oceanic shield volcanoes that generate tsunamis potentially represent a high-magnitude but low-frequency hazard, and it is actually difficult to infer the mechanisms and dynamics controlling them. Here we document tsunami deposits at high elevation (up to 132 m) on the north-western slopes of Tenerife, Canary Islands, as a new evidence of megatsunami generated by volcano flank failure. Analyses of the tsunami deposits demonstrate that two main tsunamis impacted the coasts of Tenerife 170 kyr ago. The first tsunami was generated during the submarine stage of a retrogressive failure of the northern flank of the island, whereas the second one followed the debris avalanche of the subaerial edifice and incorporated pumices from an on-going ignimbrite-forming eruption. Coupling between a massive retrogressive flank failure and a large explosive eruption represents a new type of volcano-tectonic event on oceanic shield volcanoes and a new hazard scenario.

Published
2017
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