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1. Uppermost Mantle Velocity beneath the Mid-Atlantic Ridge and Transform Faults in the Equatorial Atlantic Ocean

Author: Jean-Yves Royer, Guilherme W. S. de Melo, Aderson F. do Nascimento, Ross Parnell-Turner, Marcia Maia, D. K. Smith, and Robert P. Dziak
Subjects: Seismometer, 010504 meteorology & atmospheric sciences, Transform fault, Mid-Atlantic Ridge, 010502 geochemistry & geophysics, 01 natural sciences, Mantle (geology), Azimuth, Geophysics, Shear (geology), Geochemistry and Petrology, Lithosphere, Upwelling, Seismology, Geology, 0105 earth and related environmental sciences
Abstract: Seismic rays traveling just below the Moho provide insights into the thermal and compositional properties of the upper mantle and can be detected as Pn phases from regional earthquakes. Such phases are routinely identified in the continents, but in the oceans, detection of Pn phases is limited by a lack of long-term instrument deployments. We present estimates of upper-mantle velocity in the equatorial Atlantic Ocean from Pn arrivals beneath, and flanking, the Mid-Atlantic Ridge and across several transform faults. We analyzed waveforms from 50 earthquakes with magnitude Mw>3.5, recorded over 12 months in 2012–2013 by five autonomous hydrophones and a broadband seismograph located on the St. Peter and St. Paul archipelago. The resulting catalog of 152 ray paths allows us to resolve spatial variations in upper-mantle velocities, which are consistent with estimates from nearby wide-angle seismic experiments. We find relatively high velocities near the St. Paul transform system (∼8.4 km s−1), compared with lower ridge-parallel velocities (∼7.7 km s−1). Hence, this method is able to resolve ridge-transform scale velocity variations. Ray paths in the lithosphere younger than 10 Ma have mean velocities of 7.9±0.5 km s−1, which is slightly lower than those sampled in the lithosphere older than 20 Ma (8.1 km±0.3 s−1). There is no apparent systematic relationship between velocity and ray azimuth, which could be due to a thickened lithosphere or complex mantle upwelling, although uncertainties in our velocity estimates may obscure such patterns. We also do not find any correlation between Pn velocity and shear-wave speeds from the global SL2013sv model at depths
Published: 2020
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2. Occurrence of Omura’s whale, Balaenoptera omurai (Cetacea: Balaenopteridae), in the Equatorial Atlantic Ocean based on Passive Acoustic Monitoring

Author: Alexey Sukhovich, Marcia Maia, Jean-Yves Royer, Sérgio C. Moreira, Renata S. Sousa-Lima, Marcelo Weksler, Milton C C Marcondes, Salvatore Cerchio, Museu Nacional de Historia Natural, <span class='valid'>Universidade Federal do Rio Grande do Norte [Natal] <span class='acronym'>UFRN</span></span> (UFRN), Laboratoire Géosciences Océan (LGO), Université de Bretagne Sud (UBS)-Université de Brest (UBO)-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)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Instituto Baleia Jubarte (IBJ), Instituto Owaldo Cruz (FIOCRUZ), Maia, Marcia, Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), and Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, vocalization, Cetacea, 010603 evolutionary biology, 01 natural sciences, biology.animal, Genetics, medicine, song, 14. Life underwater, Atlantic Ocean, ComputingMilieux_MISCELLANEOUS, Ecology, Evolution, Behavior and Systematics, Nature and Landscape Conservation, geography.geographical_feature_category, Ecology, Balaenoptera, biology, seasonality, Whale, 010604 marine biology & hydrobiology, Balaenopteridae, Balaenoptera omurai, Seasonality, acoustic detection, medicine.disease, biology.organism_classification, Omura's whale, [SDE.BE] Environmental Sciences/Biodiversity and Ecology, Oceanography, Geography, Habitat, Ridge, Archipelago, Animal Science and Zoology, [SDE.BE]Environmental Sciences/Biodiversity and Ecology
Abstract: The current known distribution of Omura’s whale includes the tropical and warm temperate waters of the western Pacific, Indian, and Atlantic Oceans. Evidence of their presence in the Atlantic Ocean is based on beach cast specimens found on the coasts of Mauritania (North Atlantic) and Northeastern Brazil (South Atlantic). The present study characterizes the occurrence of this species in the São Pedro and São Paulo Archipelago (SPSPA), on the mid-Atlantic ridge between South America and Africa, based on autonomous recording systems. Acoustic signals were similar, but not identical, to B. omurai vocalizations recorded off the coast of Madagascar. Although these signals were recorded for only 11 months, there are peaks in vocal activity between May and June in the vicinities of SPSPA, suggesting either a shift in distribution within the Atlantic equatorial waters or seasonality in the species’ vocal behavior in this region. The first acoustic records of Omura’s whales in the Equatorial Atlantic suggest that these animals may also use deep-water habitats, in addition to the shallow-water habitat use observed in other regions., A atual distribuição conhecida da baleia-de-Omura (Balaenoptera omurai) inclui as águas tropicais e temperadas quentes dos oceanos Pacífico ocidental, Índico e Atlântico. A evidência de sua presença no oceano Atlântico baseia-se em espécimes encalhados encontrados em praias da Mauritânia (Atlântico Norte) e do Nordeste do Brasil (Atlântico Sul). O presente estudo caracteriza a ocorrência dessa espécie no Arquipélago de São Pedro e São Paulo (ASPSP), localizado sobre a Dorsal Mesoatlântica entre a América do Sul e a África, com base em sistemas de monitoramento acústico passivo. Os sinais acústicos detectados foram similares, mas não idênticos, às vocalizações de B. omurai gravadas na costa de Madagascar. Embora esses sinais tenham sido registrados por apenas 11 meses, há picos na atividade vocal entre maio e junho nas proximidades do ASPSP, sugerindo uma mudança na distribuição da espécie nas águas equatoriais do Atlântico ou uma sazonalidade no comportamento vocal nessa região. Os primeiros registros acústicos das baleias-de-Omura no Atlântico Equatorial sugerem que esses animais também podem utilizar habitats de águas profundas, além de habitats de águas rasas como observado em outras regiões.
Published: 2020
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3. Semibrittle seismic deformation in high-temperature mantle mylonite shear zone along the Romanche transform fault

Author: Emma P. M. Gregory, Marcia Maia, Zhikai Wang, Zhiteng Yu, Daniele Brunelli, Satish C. Singh, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Laboratoire Géosciences Océan (LGO), Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), 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), Dipartimento di Scienzedella Terra, Università di Modena e Reggio Emilia largo, Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), and 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)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 010504 meteorology & atmospheric sciences, mantle mylonite shear, Induced seismicity, 010502 geochemistry & geophysics, 01 natural sciences, Mantle (geology), Lithosphere, Romanche transform fault, Research Articles, 0105 earth and related environmental sciences, Multidisciplinary, Semibrittle, Supershear earthquake, Transform fault, SciAdv r-articles, Geology, seismic deformation, Plate tectonics, Geophysics, 13. Climate action, [SDU]Sciences of the Universe [physics], Shear zone, Seismology, Mylonite, Research Article
Abstract: Deep microseismicity occurs in high-temperature ductile mantle mylonite shear zones resulting from semibrittle fracturing., Oceanic transform faults, a key element of plate tectonics, represent the first-order discontinuities along mid-ocean ridges, host large earthquakes, and induce extreme thermal gradients in lithosphere. However, the thermal structure along transform faults and its effects on earthquake generation are poorly understood. Here we report the presence of a 10- to 15-kilometer-thick in-depth band of microseismicity in 10 to 34 kilometer depth range associated with a high-temperature (700° to 900°C) mantle below the brittle lithosphere along the Romanche mega transform fault in the equatorial Atlantic Ocean. The occurrence of the shallow 2016 moment magnitude 7.1 supershear rupture earthquake and these deep microearthquakes indicate that although large earthquakes occur in the upper brittle lithosphere, a substantial amount of deformation is accommodated in the semibrittle mylonitic mantle that resides at depths below the 600°C isotherm. We also observe a rapid westward deepening of this band of seismicity indicating a strong lateral heterogeneity.
Published: 2021
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4. Variable Crustal Production Originating From Mantle Source Heterogeneity Beneath the South East Indian Ridge and Amsterdam‐St. Paul Plateau

Author: Marcia Maia, Eric Mittelstaedt, A.L.R. Sibrant, David W. Graham, Laboratoire Géosciences Océan (LGO), Université de Bretagne Sud (UBS)-Université de Brest (UBO)-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)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Department of Geological Sciences [Idaho], University of Idaho [Moscow, USA], Department of Civil Environmental and Architectural Engineering, University of Kansas [Lawrence] (KU), ISBlue - Interdisciplinary Graduate School for the Blue planet (2017), ANR-17-EURE-0015,ISBlue,Interdisciplinary Graduate School for the Blue planet(2017), Idaho State University, Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), and Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, 010504 meteorology & atmospheric sciences, Paul Plateau, ywords, 010502 geochemistry & geophysics, South East Indian Ridge, 01 natural sciences, Mantle (geology), Paleontology, Geophysics, oceanic plateaus, plume-ridge interaction, 13. Climate action, Geochemistry and Petrology, [SDU]Sciences of the Universe [physics], South east, [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology, Amsterdam-St, [SDU.STU.PG]Sciences of the Universe [physics]/Earth Sciences/Paleontology, geophysical and geochemical evidence, Geology, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, 0105 earth and related environmental sciences
Abstract: International audience; The Amsterdam-St. Paul (ASP) Plateau formed by interaction between the South East Indian Ridge (SEIR) and the ASP mantle plume during the last 10 Myr. The combined bathymetry and gravity-derived crustal thickness anomalies along the present and paleoaxes of the SEIR atop the plateau indicate: (1) a thicker crust and shallower water depth along the southern part of segment I2 during much of the last 10 Myr; (2) an earlier decrease (~1.4 Ma) in crustal thickness along the southern part of I2 compared to the northern part (~0.9 Ma) during the most recent period of reduced magmatism; (3) a topographic transition at ~0.7 Ma and during the last 0.1 Myr; and (4) an approximately uniform crustal thickness (8 km) along the entire I2 segment today. These observations require spatial and temporal variations in magma production during construction of the ASP Plateau over the last 3 Myr. We propose that during periods of weaker plume magma flux, spatial variations in upper mantle temperature and composition are small, and lead to small variations in crustal thickness along-axis. In contrast, during periods of stronger plume magma flux, spatial contrasts in upper mantle temperature and composition (fertility) are large, leading to significant variations in crustal thickness. Along-axis variations of 3 He/ 4 He, Δ8/4Pb, K/Ti, and Na 8 in "zero-age" basalts indicate that there is a gradient in the underlying mantle material, from a "common" mantle plume component (Δ8/4Pb~60) stronger in the north to a DUPAL component (Δ8/4Pb~110) dominating in the south. keywords: oceanic plateaus, plume-ridge interaction, Amsterdam St. Paul Plateau, South East Indian Ridge, geophysical and geochemical evidence key points:-Crustal architecture of the Amsterdam St. Paul Plateau records high and low plume flux stages during mantle plume-spreading ridge interaction-Plume magma flux decreased earlier in the south than in the north along a single spreading segment.-Along-axis differences in crustal thickness and Pb and He isotopes suggest both shallow mantle and plume heterogeneities.
Published: 2019
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5. Joint inversion of gravity and surface wave data constrained by magnetotelluric: Application to deep geothermal exploration of crustal fault zone in felsic basement

Author: Sophie Hautot, Pascal Tarits, jean-michel ars, Mathieu Bellanger, Olivier Coutant, Marcia Maia, Laboratoire Géosciences Océan (LGO), Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), TLS-Geothermics, Laboratoire de Géophysique Interne et Tectonophysique (LGIT), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Laboratoire Central des Ponts et Chaussées (LCPC)-Institut des Sciences de la Terre (ISTerre), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR), Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Institut des Sciences de la Terre (ISTerre), and Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])
Subjects: Inversion (geology), 0211 other engineering and technologies, 02 engineering and technology, 010502 geochemistry & geophysics, 01 natural sciences, Geothermal exploration, Magnetotellurics, Transition zone, [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology, 021108 energy, Geothermal gradient, ComputingMilieux_MISCELLANEOUS, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, 0105 earth and related environmental sciences, [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, geography, geography.geographical_feature_category, Exploration geophysics, Renewable Energy, Sustainability and the Environment, Geology, Massif, Geophysics, Geotechnical Engineering and Engineering Geology, 13. Climate action, Surface wave, [SDU.STU.PG]Sciences of the Universe [physics]/Earth Sciences/Paleontology
Abstract: Geophysical exploration in unconventional geothermal reservoir is challenging because of the lack of structures with specific geophysical signature such as a clay cap above volcanic geothermal reservoirs. The combination of several geophysical methods such as magnetotelluric (MT), gravity and seismic methods provides complementary insight into the geothermal reservoir. We present a joint inversion approach of ambient noise surface wave and gravity constrained by the 3D distribution of electrical resistivity. The method is applied to analyze the potential of unconventional deep geothermal resources in the French Massif Central (FMC). We coupled the resistivity, density and shear wave velocity with a linear correlation. We characterized the common properties in relation to the geological domains down to about 10–15 km. We validated the proposed approach on a synthetic model derived from models obtained from each independent geophysical method. The joint inversion limited the non-uniqueness of the gravity and the ambient noise tomography inversion and allow to recover the features of the synthetic models. We applied the method to real field data acquired in the Sioule Valley, Massif Central, France. The joint features observed in the geophysical models suggest a deep heat source associated with a possible shallow (∼6–8 km) brittle–ductile transition. A large fault zone, the Pongibaud Fault zone, seems to become listric and connect the surface to this transition zone to possibly constitute a permeable path for water circulation.
Published: 2019
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6. Antarctic blue whales ( Balaenoptera musculus intermedia ) recorded at the Equator in the Atlantic Ocean

Author: Flore Samaran, Sérgio C. Moreira, Marcia Maia, Emmanuelle C. Leroy, Jean-Yves Royer, Adrien Berne, Kathleen M. Stafford, Lab-STICC_ENSTAB_CID_TOMS, Laboratoire des sciences et techniques de l'information, de la communication et de la connaissance (Lab-STICC), École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-Université Bretagne Loire (UBL)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-Université Bretagne Loire (UBL)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT), Laboratoire Géosciences Océan (LGO), Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Universidade Federal Fluminense [Rio de Janeiro] (UFF), Applied Physics Laboratory [Seattle] (APL-UW), University of Washington [Seattle], 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), Institut Mines-Télécom [Paris] (IMT)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-École Nationale d'Ingénieurs de Brest (ENIB)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Université Bretagne Loire (UBL)-Institut Mines-Télécom [Paris] (IMT)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-École Nationale d'Ingénieurs de Brest (ENIB)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Université Bretagne Loire (UBL), Université de Bretagne Sud (UBS)-Université de Brest (UBO)-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)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and Centre National de la Recherche Scientifique (CNRS)-Institut d'écologie et environnement-Observatoire des Sciences de l'Univers-Université de Brest (UBO)-Institut national des sciences de l'Univers (INSU - CNRS)
Subjects: 0106 biological sciences, Balaenoptera musculus, biology, 010604 marine biology & hydrobiology, [SDV]Life Sciences [q-bio], Equator, Aquatic Science, biology.organism_classification, 01 natural sciences, Blue Whales, Oceanography, Geography, 0103 physical sciences, 14. Life underwater, Intermedia, 010301 acoustics, Ecology, Evolution, Behavior and Systematics, ComputingMilieux_MISCELLANEOUS
Abstract: International audience
Published: 2019
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7. Seafloor evidence for pre-shield volcanism above the Tristan da Cunha mantle plume

Author: Anne Strack, Wilfried Jokat, Wolfram Geissler, Graeme Eagles, Janina Kammann, Marion Jegen, Paul Wintersteller, Marcia Maia, Antje Schloemer, Alfred Wegener Institute for Polar and Marine Research (AWI), Faculty of Geosciences, University of Bremen, Center for Marine Environmental Sciences [Bremen] (MARUM), Universität Bremen, Laboratoire Géosciences Océan (LGO), Université de Bretagne Sud (UBS)-Université de Brest (UBO)-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)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Department of Geoscience and Natural Resource Management, København Universitet, Danmark, Helmholtz Centre for Ocean Research [Kiel] (GEOMAR), Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität, Ludwig-Maximilians-Universität München (LMU), Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), and Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 010504 meteorology & atmospheric sciences, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], Science, Seamount, General Physics and Astronomy, Volcanology, 010502 geochemistry & geophysics, 01 natural sciences, General Biochemistry, Genetics and Molecular Biology, Mantle plume, Article, Paleontology, 14. Life underwater, lcsh:Science, Submarine volcano, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, geography, Multidisciplinary, geography.geographical_feature_category, Tectonics, Fracture zone, Geology, General Chemistry, Seafloor spreading, Oceanic core complex, Submarine eruption, Geophysics, Volcano, 13. Climate action, lcsh:Q
Abstract: Tristan da Cunha is assumed to be the youngest subaerial expression of the Walvis Ridge hot spot. Based on new hydroacoustic data, we propose that the most recent hot spot volcanic activity occurs west of the island. We surveyed relatively young intraplate volcanic fields and scattered, probably monogenetic, submarine volcanoes with multibeam echosounders and sub-bottom profilers. Structural and zonal GIS analysis of bathymetric and backscatter results, based on habitat mapping algorithms to discriminate seafloor features, revealed numerous previously-unknown volcanic structures. South of Tristan da Cunha, we discovered two large seamounts. One of them, Isolde Seamount, is most likely the source of a 2004 submarine eruption known from a pumice stranding event and seismological analysis. An oceanic core complex, identified at the intersection of the Tristan da Cunha Transform and Fracture Zone System with the Mid-Atlantic Ridge, might indicate reduced magma supply and, therefore, weak plume-ridge interaction at present times., Here, the authors combine bathymetry and sediment echosound data to present a submarine, volcanic map of the Tristan de la Cunha region. They find that the youngest volcanic expression of the Tristan de la Cunha mantle plume is currently located to the (south-) west of the island.
Published: 2019
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8. Topographic and Morphologic Evidences of Deformation at Oceanic Transform Faults: Far-Field and Local-Field Stresses

Author: Marcia Maia, Laboratoire Géosciences Océan (LGO), Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), and Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, 010504 meteorology & atmospheric sciences, Transtension, Transform fault, Fracture zone, Kinematics, 010502 geochemistry & geophysics, 01 natural sciences, Mantle (geology), Transpression, Tectonics, 13. Climate action, Lithosphere, [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology, [SDU.STU.PG]Sciences of the Universe [physics]/Earth Sciences/Paleontology, Seismology, Geology, ComputingMilieux_MISCELLANEOUS, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, 0105 earth and related environmental sciences
Abstract: Oceanic transform faults are fundamental features of the spreading processes and record changes in both the local-field and the far-field stresses, due to either local factors or plate motion changes. The study of the morphologic evidences of deformation they undergo due to these changes is key to understand the thermal and the mechanical structure of the oceanic lithosphere. Different features result from transform deformation. The large transverse ridges observed at several transforms form as a flexural response to extension at the transform or the fracture zone. The thermal heating of the lithosphere as well as the serpentinization of mantle rocks play a minor role in this uplift. Median ridges are also tectonic features formed due to compressive or extensional stresses inside the transform domain and serpentinization does not appear to play a major role in their uplift. At fast spreading ridges, extension inside the transform domain often results in the formation of “leaky transforms.” These morphologies are rare at slow spreading ridges, because the colder lithosphere does not favor the inception of intra-transform segments. However, large offset transforms, under severe changes in plate motions, may develop this geometry. Several factors will control the response of transform faults to changes in plate motion. A major one is the length of the offset, but the magnitude of the change in plate motion is also important. Minor changes will be easily accommodated by both small and large offset transforms, often through small deformations inside the transform valley. Conversely, larger changes may have small impact on small offset transforms but result in strong deformation at larger ones. Large offset transforms are slower to respond to kinematic changes than small offset ones. Mega-transforms may readjust even more slowly, thus forming a multifault complex boundary. At even larger offsets, the transform is no longer able to adjust to severe changes and will be abandoned. Local stresses such as mantle flow and thermal contraction of the lithosphere may induce significant topography at transform faults through small bends of the principal transform displacement zone (PTDZ) inside the transform domain, thus resulting in localized transpression and transtension.
Published: 2019
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9. The August 2010 earthquake swarm at North FAMOUS–FAMOUS segments, Mid-Atlantic Ridge: geophysical evidence of dike intrusion

Author: Marion Giusti, Robert P. Dziak, Alexey Sukhovich, Julie Perrot, Marcia Maia, Laboratoire Géosciences Océan (LGO), Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), Domaines Océaniques (LDO), Centre National de la Recherche Scientifique (CNRS)-Institut d'écologie et environnement-Observatoire des Sciences de l'Univers-Université de Brest (UBO)-Institut national des sciences de l'Univers (INSU - CNRS), Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), 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), and 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)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, Dike, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Mid-Atlantic Ridge, 010502 geochemistry & geophysics, Earthquake swarm, 01 natural sciences, Intrusion, Geophysics, Geochemistry and Petrology, [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology, [SDU.STU.PG]Sciences of the Universe [physics]/Earth Sciences/Paleontology, Geology, Seismology, ComputingMilieux_MISCELLANEOUS, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, 0105 earth and related environmental sciences
Abstract: International audience
Published: 2018
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10. Geophysical fingerprints of hyper-extended, exhumed and embryonic oceanic domains: the example from the Iberia–Newfoundland rifted margins

Author: Gianreto Manatschal, Daniel Sauter, Julia Autin, Marcia Maia, Natasha Stanton, Adriano R. Viana, Dynamique de la lithosphère et des bassins sédimentaires (IPGS) (IPGS-Dylbas), Institut de physique du globe de Strasbourg (IPGS), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Domaines Océaniques (LDO), and 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)
Subjects: 010504 meteorology & atmospheric sciences, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], A domain, Geophysics, Geodynamics, 010502 geochemistry & geophysics, Oceanography, Breakup, 01 natural sciences, Mantle (geology), 13. Climate action, Geochemistry and Petrology, Lithosphere, Proximal margin, Magmatism, 14. Life underwater, Magnetic anomaly, Geology, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract: This study investigates the magnetic and gravity signatures and associated seismic character of hyper-extended, exhumed and embryonic oceanic domains along the conjugate Iberia–Newfoundland rifted margins. As these margins have been drilled down to basement along their distal parts, it is possible to explore and test different geophysical techniques and interpretations. The aims of this work are twofold: (1) to investigate the location and nature of the two main marginal boundaries—the necking zone and the J Anomaly, which define the limits of major domains; and (2) to map the lateral variations of gravity and magnetic signatures and their detailed correlation with seismic data, from the proximal margin until the first unequivocal oceanic magnetic anomaly (e.g. C34 Anomaly). The results point out that the J Anomaly corresponds to a first-order tectono-magmatic boundary, with a basement formed by polyphase magmatism. It marks the boundary between the exhumed mantle domain, with little magmatic additions, from a domain oceanwards that reveals comparable trends, frequencies and a general magnetic pattern at both sides of the Atlantic, suggesting a coeval evolution. We propose that the domain between the J and the C34 Anomalies was formed by an embryonic spreading system, with intermittent budgets of magma, similar to those observed at very slow spreading systems. The J Anomaly may thus correspond to the location of lithospheric breakup though its origin and the nature of the domain oceanwards remains to be constrained.
Published: 2016
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11. Extreme mantle uplift and exhumation along a transpressive transform fault

Author: Marcia Maia, Ivo Pessanha, Anne Briais, Pedro Lima Emmerich Oliveira, Akihisa Motoki, Nicolas Ferreira, Eliane da Costa Alves, Susanna Eleonora Sichel, Thomas Ferreira da Costa Campos, Bérengère Mougel, Daniele Brunelli, Arthur Ayres, Christophe Hémond, Isa Brehme, Denise Aparecida Soares de Moura, Marco Ligi, Carla Scalabrin, Laboratoire Géosciences Océan (LGO), Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Géosciences Environnement Toulouse (GET), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Dipartimento di scienze chimiche e geologiche, Institut de Physique du Globe de Paris (IPGP), 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), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), 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), Mackenzie Presbyterian University [São Paulo] (UPM), 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)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS), Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Centre National d'Études Spatiales [Toulouse] (CNES), and Centre National de la Recherche Scientifique (CNRS)-Université de La Réunion (UR)-Université Paris Diderot - Paris 7 (UPD7)-IPG PARIS-Institut national des sciences de l'Univers (INSU - CNRS)
Subjects: 010504 meteorology & atmospheric sciences, 010502 geochemistry & geophysics, 01 natural sciences, Mantle (geology), Physics::Geophysics, [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology, Physics::Atmospheric and Oceanic Physics, ComputingMilieux_MISCELLANEOUS, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, 0105 earth and related environmental sciences, [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, geography, geography.geographical_feature_category, MID-ATLANTIC RIDGE, ST-PAUL ROCKS, EQUATORIAL ATLANTIC, FRACTURE-ZONE, OCEAN-RIDGE, HEAT-FLOW, BENEATH, LITHOSPHERE, BATHYMETRY, MECHANISMS, Transform fault, Crust, Geodynamics, Tectonics, Ridge, General Earth and Planetary Sciences, Astrophysics::Earth and Planetary Astrophysics, Structural geology, [SDU.STU.PG]Sciences of the Universe [physics]/Earth Sciences/Paleontology, Earth and Planetary Sciences (all), Seismology, Geology
Abstract: Mantle exhumation at slow-spreading ridges is favoured by extensional tectonics through low-angle detachment faults(1-4), and, along transforms, by transtension due to changes in ridge/transform geometry(5,6). Less common, exhumation by compressive stresses has been proposed for the large-offset transforms of the equatorial Atlantic(7,8). Here we show, using high-resolution bathymetry, seismic and gravity data, that the northern transform fault of the St Paul system has been controlled by compressive deformation since similar to 10 million years ago. The long-lived transpression resulted from ridge overlap due to the propagation of the northern Mid-Atlantic Ridge segment into the transform domain, which induced the migration and segmentation of the transform fault creating restraining stepovers. An anticlockwise change in plate motion at similar to 11 million years ago(5) initially favoured extension in the left-stepping transform, triggering the formation of a transverse ridge, later uplifted through transpression, forming the St Peter and St Paul islets. Enhanced melt supply at the ridge axis due to the nearby Sierra Leone thermo chemical anomaly(9) is responsible for the robust response of the northern Mid-Atlantic Ridge segment to the kinematic change. The long-lived process at the origin of the compressive stresses is directly linked to the nature of the underlying mantle and not to a change in the far-field stress regime.
Published: 2016
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12. Subsurface structure and stratigraphy of the northwest end of the Turkana Basin, Northern Kenya Rift, as revealed by magnetotellurics and gravity joint inversion

Author: Jean-Jacques Tiercelin, Pascal Tarits, Sophie Hautot, Peter Thuo, Marcia Maia, Yassine Abdelfettah, Institut de physique du globe de Strasbourg (IPGS), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), 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), Géosciences Rennes (GR), Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES), Université de Brest (UBO), IMAGIR, Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), and 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)
Subjects: Regional geology, Kachoda Basin, 010504 meteorology & atmospheric sciences, Inversion (geology), Turkana Basin, joint inversion, Structural basin, 010502 geochemistry & geophysics, 01 natural sciences, Sub-basalt imaging, Paleontology, Precambrian, Northern Kenya Rift, Magnetotellurics, Lapur Sandstone, Geomorphology, 0105 earth and related environmental sciences, Earth-Surface Processes, Rift, Geology, gravity, Source rock, [SDU.STU.ST]Sciences of the Universe [physics]/Earth Sciences/Stratigraphy, magnetotelluric, Sedimentary rock, “Turkana Volcanics”
Abstract: International audience; In order to understand the subsurface stratigraphy and structure of the northwest end of the Turkana Basin, Northern Kenya Rift, we used 2-D joint inversion of magnetotelluric (MT) and gravity data acquired along 3 profiles perpendicular to the main Murua Rith-Lapur Rift Border Fault. The regional geology is characterized by a basement of Precambrian age overlain by a ≤500-m thick sandstone formation named the Lapur Sandstone of upper Cretaceous-lower Eocene in age, covered by thick rhyolitic and basaltic lavas of late Eocene-middle Miocene age, known as the “Turkana Volcanics”. Final interpretation of the resistivity and density models, until 5 km depth, obtained by the joint inversion approach confirms the previous general knowledge about the half-graben geometry of the northern part of the Turkana Basin. The main Murua Rith-Lapur Rift Border Fault is well identified by both gravity and MT. At least, two other important secondary faults without surface expression are also identified. A new small half-graben basin, named the Kachoda Basin, parallel to the main Turkana Basin and filled by 1.5 km of sediments, has been also characterized. This study also highlights strong thickness variations of the three main geological units that could be expected in the subsurface of the Turkana Basin. For example, the sedimentary Nachukui and Kibish Formations reach up to >3 km in thickness at the eastern end of the north and central profiles. Lateral variations of the topography of the Precambrian basement are also evidenced. Conceptual geological models, which result from the combination of the obtained density and resistivity models as well as from geological and reflection seismic data, are proposed. In such an area of intensive and promising oil exploration, these models are essential in terms of identification of reservoirs, source rocks and trapping mechanisms.
Published: 2016
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13. Constraints on age and construction process of the Foundation chain submarine volcanoes from magnetic modeling

Author: David Jouannetaud, Marcia Maia, J. Dyment, Laboratoire Géosciences Océan (LGO), Université de Bretagne Sud (UBS)-Université de Brest (UBO)-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)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), 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), Institut de Physique du Globe de Paris (IPGP), and 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)
Subjects: 010504 meteorology & atmospheric sciences, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], 010502 geochemistry & geophysics, 01 natural sciences, Geochemistry and Petrology, Lithosphere, Hotspot (geology), seamount magnetism, Earth and Planetary Sciences (miscellaneous), Magnetic anomaly, Submarine volcano, 0105 earth and related environmental sciences, ridge–hotspot interactions, geography, seamount ages, geography.geographical_feature_category, Pacific Plate, ridge-hotspot interactions, Geophysics, Earth's magnetic field, Volcano, [SDU]Sciences of the Universe [physics], 13. Climate action, Space and Planetary Science, Radiometric dating, hotspot, intraplate volcanism, Geology, Seismology
Abstract: International audience; The interaction between the Foundation hotspot and the Pacific-Antarctic Ridge (South Pacific) is one of the two known cases where a ridge is approaching a hotspot. This ridge-hotspot relative movement results in a change in the morphology of the volcanoes along the chain as the age of the lithosphere at the time of edifice formation progressively diminishes. Four hundred kilometers west of the Pacific-Antarctic Ridge axis, volcanism is distributed along two sub-parallel lines of volcanoes, separated by distances diminishing from~100 km at the west to~50 km near the axis of the ridge. The magnetic anomalies mapped on this part of the chain show a pattern clearly dominated by the magnetic signature of the seamounts. The anomalies were forward modeled using a remanent magnetization of normal or reversed polarity within the volcano topography. The resulting pattern of normal and reversed magnetization is consistent with the intervals of the geomagnetic polarity time scale for the last 5 Ma, the age of the oldest studied volcano. These magnetic anomalies therefore represent an independent means of dating the volcanic edifices. The ages deduced from the modeling are consistent with the hypothesis of volcanoes built by a hotspot on the fast moving Pacific plate and are in good agreement with the published radiometric dates, although these dates tend to correspond to the late constructional stages of the edifices. The differences between magnetic and radiometric ages suggest that the average time span to build a volcano of the Foundation chain is about 1 million years, in agreement with other intraplate edifices. The difference between the magnetic ages of the seamounts and of the underlying crust, both deduced from the magnetic anomaly analysis, show that the ridge has approached the hotspot at a rate of 40 km/Ma.
Published: 2005
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14. From rifting to spreading in the eastern Gulf of Aden: a geophysical survey of a young oceanic basin from margin to margin

Author: Sylvie Leroy, Pascal Gente, Marcia Maia, Julie Perrot, Philippe Huchon, Philippe Patriat, Angelina Blais, Ali Al-Kathiri, Claude Lepvrier, Jean Marc Fleury, Elia d'Acremont, Pierre Yves Ruellan, Serge Merkouriev, Marc Fournier, Nicolas Bellahsen, Marie Odile Beslier, Laboratoire de tectonique (LT), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), 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), Géoazur (GEOAZUR 6526), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-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)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Nice Sophia Antipolis (... - 2019) (UNS), and COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, geography, geography.geographical_feature_category, Rift, 010504 meteorology & atmospheric sciences, Transform fault, Geology, Deep basin, 010502 geochemistry & geophysics, 01 natural sciences, Seafloor spreading, Horst and graben, Discontinuity (geotechnical engineering), 14. Life underwater, Oceanic basin, ComputingMilieux_MISCELLANEOUS, Seismology, 0105 earth and related environmental sciences
Abstract: A geophysical survey in the eastern Gulf of Aden, between the Alula–Fartak (52°E) and the Socotra (55°E) transform faults, was carried out during the Encens–Sheba cruise. The conjugate margins of the Gulf are steep, narrow and asymmetric. Asymmetry of the rifting process is highlighted by the conjugate margins (horst and graben in the north and deep basin in the south). Two transfer fault zones separate the margins into three segments, whereas the present-day Sheba Ridge is divided into two segments by a transform discontinuity. Therefore segmentation of the Sheba Ridge and that of the conjugate margins did coincide during the early stages of oceanic spreading. Extensive magma production is evidenced in the central part of the western segment. Anomaly 5d was identified in the northern and southern parts of the oceanic basin, thus confirming that seafloor spreading in this part of Gulf of Aden started at least 17.6 Ma ago.
Published: 2004
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15. 40 Ar/ 39 Ar geochronology and structural data from the giant Okavango and related mafic dyke swarms, Karoo igneous province, northern Botswana

Author: Ali B Kampunzu, M. Modisi, Marcia Maia, Jérôme Dyment, Fred Jourdan, G. Tshoso, Gilbert Féraud, B. Le Gall, Jean-Jacques Tiercelin, Hélène Bertrand, Géoazur (GEOAZUR 6526), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, 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)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (1965 - 2019) (UNS), and COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 010504 meteorology & atmospheric sciences, Earth science, Geochemistry, Diachronous, 010502 geochemistry & geophysics, 01 natural sciences, Mantle plume, Igneous rock, Precambrian, Geophysics, Space and Planetary Science, Geochemistry and Petrology, Geochronology, Earth and Planetary Sciences (miscellaneous), Flood basalt, Extensional tectonics, Mafic, Geology, 0105 earth and related environmental sciences
Abstract: In NE Botswana, the Karoo dykes include a major N110° dyke swarm known as the Okavango giant dyke swarm (ODS/N110°) and a second smaller set of N70° dykes belonging to the Sabi-Limpopo dyke swarm (SLDS/N70°). New 40Ar/39Ar plagioclase dating of Karoo dolerites of the giant ODS/N110° and the SLDS/N70° in NE Botswana yield plateau ages between 179.6±1.2 and 178.4±1.1 Ma. Our data are concordant with previous 40Ar/39Ar ages for Northern Karoo dykes and lava flows exposed in western Zimbabwe. The data are tightly clustered, indicating a short-lived (179–181 Ma) flood basalt magmatism in this region. The new radiometric dates allow the definition of a diachronous Jurassic flood basalt activity in southern Africa. A significant south to north younging at the scale of the Karoo igneous province correlates with a chemical zonation from low-Ti (south) to high-Ti (north) mafic rocks. Structural measurements on the ODS/N110° and SLDS/N70° Karoo dykes of NE Botswana suggest that: (1) most of the host fractures are inherited Precambrian structures; (2) dyke emplacement occurred under unidirectional tensional stresses; (3) significant syn- and post-volcanic extensional tectonics are lacking. Combined with regional geology, these geochronological and structural data do not confirm unambiguously the triple-junction hypothesis usually put forward to support a mantle plume model for the evolution of the Karoo igneous province, prior to Gondwana breakup.
Published: 2002
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16. Correlated patterns in hydrothermal plume distribution and apparent magmatic budget along 2500 km of the Southeast Indian Ridge

Author: Edward T. Baker, Sharon L. Walker, Tingting Wang, Marcia Maia, Yongshun John Chen, Christophe Hémond, Anne Briais, Daniel S. Scheirer, NOAA Pacific Marine Environmental Laboratory [Seattle] (PMEL), National Oceanic and Atmospheric Administration (NOAA), 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), University of Massachusetts [Lowell] (UMass Lowell), University of Massachusetts System (UMASS), Dynamique terrestre et planétaire (DTP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), United States Geological Survey [Reston] (USGS), School of Earth and Space Sciences, Peking University [Beijing], School of Ocean and Earth Science, Tongji University, Joint Institute for the Study of the Atmosphere and Ocean (JISAO) under NOAA NA10OAR4320148 NSF OCE-9505667, Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), and Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 010504 meteorology & atmospheric sciences, mid-ocean ridge, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], Hot spot (veterinary medicine), Southeast Indian Ridge, 010502 geochemistry & geophysics, 01 natural sciences, Hydrothermal circulation, Geochemistry and Petrology, mantle hot spot, hydrothermal activity, Petrology, 0105 earth and related environmental sciences, Spatial density, geography, Plateau, geography.geographical_feature_category, magmatic budget, Hydrothermal plume, Mid-ocean ridge, Geophysics, plume incidence, Plume, Ridge, Geology
Abstract: International audience; Multiple geological processes affect the distribution of hydrothermal venting along a mid-ocean ridge. Deciphering the role of a specific process is often frustrated by simultaneous changes in other influences. Here we take advantage of the almost constant spreading rate (65–71 mm/yr) along 2500 km of the Southeast Indian Ridge (SEIR) between 77 E and 99 E to examine the spatial density of hydrothermal venting relative to regional and segment-scale changes in the apparent magmatic budget. We use 227 vertical profiles of light backscatter and (on 41 profiles) oxidation-reduction potential along 27 first and second-order ridge segments on and adjacent to the Amsterdam-St. Paul (ASP) Plateau to map p h , the fraction of casts detecting a plume. At the regional scale, venting on the five segments cross-ing the magma-thickened hot spot plateau is almost entirely suppressed (p h 5 0.02). Conversely, the com-bined p h (0.34) from all other segments follows the global trend of p h versus spreading rate. Off the ASP Plateau, multisegment trends in p h track trends in the regional axial depth, high where regional depth increases and low where it decreases. At the individual segment scale, a robust correlation between p h and cross-axis inflation for first-order segments shows that different magmatic budgets among first-order segments are expressed as different levels of hydrothermal spatial density. This correlation is absent among second-order segments. Eighty-five percent of the plumes occur in eight clusters totaling 350 km. We hypothesize that these clusters are a minimum estimate of the length of axial melt lenses underlying this section of the SEIR.
Published: 2014
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17. The Amsterdam-St. Paul Plateau: A complex hot spot/DUPAL-flavored MORB interaction

Author: Kevin T. M. Johnson, Marcia Maia, Christophe Hémond, Philippe Nonnotte, Myriam Janin, and Emmanuel Ponzevera
Subjects: geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Subduction, Continental crust, Geochemistry, Oceanic plateau, Pelagic sediment, 010502 geochemistry & geophysics, 01 natural sciences, Mantle (geology), Plume, Geophysics, Volcano, Geochemistry and Petrology, Oceanic crust, Geology, 0105 earth and related environmental sciences
Abstract: The Amsterdam-St Paul (ASP) oceanic plateau results from the interaction between the ASP hot spot and the Southeast Indian ridge. A volcanic chain, named the Chain of the Dead Poets (CDP), lies to its northward tip and is related to the hot spot intraplate activity. The ASP plateau and CDP study reveals that ASP plume composition is inherited from oceanic crust and pelagic sediments recycled in the mantle through a 1.5 Ga subduction process. The ASP plateau lavas have a composition (major and trace elements and Sr-Nd-Pb-Hf isotopes) reflecting the interaction between ASP plume and the Indian MORB mantle, including some clear DUPAL input. The Indian upper mantle below ASP plateau is heterogeneous and made of a depleted mantle with lower continental crust (LCC) fragments probably delaminated during the Gondwana break-up. The lower continental crust is one of the possible reservoirs for the DUPAL anomaly origin that our data support. The range of magnitude of each end-member required in ASP plateau samples is (1) 45% to 75% of ASP plume and (2) 25% to 55% of Indian DM within 0% to a maximum of 6% of LCC layers included within. The three end-members involved (plume, upper mantle and lower continental crust) and their mixing in different proportions enhances the geochemical variability in the plateau lavas. Consequently, the apparent composition homogeneity of Amsterdam Island, an aerial summit of the plateau, may result from the presence of intermediate magmatic chambers into the plateau structure.
Published: 2012
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18. Building of the Amsterdam-Saint Paul plateau: A 10 Myr history of a ridge-hot spot interaction and variations in the strength of the hot spot source

Author: Kevin T. M. Johnson, Marcia Maia, Christophe Hémond, J. Vatteville, Ivo Pessanha, Esther Courrèges, Pascal Gente, Myriam Janin, Martin Patriat, Walter R. Roest, Jean-Yves Royer, 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), LAGEMAR, Universidade Federal Fluminense [Rio de Janeiro] (UFF), Unité de recherche Géosciences Marines (Ifremer) (GM), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), CEA, Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Department of Geology and Geophysics, University of Hawai‘i [Mānoa] (UHM), 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), programme EXTRAPLAC CNRS-INSU programme SEDIT, Géosciences Marines (GM), and Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], [SDE.MCG]Environmental Sciences/Global Changes, Soil Science, Hot spot (veterinary medicine), [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], Aquatic Science, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Flux (metallurgy), ridge processes, oceanic plateaus, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), South east, Bathymetry, Petrology, Indian Ocean, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, ridge-hot spot interactions, geography, Plateau, geography.geographical_feature_category, Ecology, Paleontology, myr, plume pulses, Forestry, Crust, Geophysics, 13. Climate action, Space and Planetary Science, Ridge (meteorology), SEIR, Seismology, Geology
Abstract: The Amsterdam-Saint Paul plateau results from a 10 Myr interaction between the South East Indian Ridge and the Amsterdam-Saint Paul hot spot. During this period of time, the structure of the plateau changed as a consequence of changes in both the ridge-hot spot relative distance and in the strength of the hot spot source. The joint analysis of gravity-derived crust thickness and bathymetry reveals that the plateau started to form at similar to 10 Ma by an increase of the crustal production at the ridge axis, due to the nearby hot spot. This phase, which lasted 3-4 Myr, corresponds to a period of a strong hot spot source, maybe due to a high temperature or material flux, and decreasing ridge-hot spot distance. A second phase, between similar to 6 and similar to 3 Ma, corresponds to a decrease in the ridge crustal production. During this period, the hot spot center was close to the ridge axis and this reduced magmatic activity suggests a weak hot spot source. At similar to 3 Ma, the ridge was located approximately above the hot spot center. An increase in the hot spot source strength then resulted in the building of the shallower part of the plateau. The variations of the melt production at the ridge axis through time resulted in variations in crustal thickness but also in changes in the ridge morphology. The two periods of increased melt production correspond to smooth ridge morphology, characterized by axial highs, while the intermediate period corresponds to a rougher, rift-valley morphology. These variations reveal changes in axial thermal structure due to higher melting production rates and temperatures.
Published: 2011
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19. Crustal structure of the propagating TAMMAR ridge segment on the Mid-Atlantic Ridge, 21.5°N

Author: G. Klein, César R. Ranero, Anke Dannowski, Ingo Grevemeyer, Marcia Maia, and J. Phipps Morgan
Subjects: Basalt, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Mid-ocean ridge, Crust, Mid-Atlantic Ridge, 010502 geochemistry & geophysics, 01 natural sciences, Mantle (geology), Geophysics, Ridge push, Geochemistry and Petrology, Ridge, Seismic refraction, Seismology, Geology, 0105 earth and related environmental sciences
Abstract: Active ridge propagation frequently occurs along spreading ridges and profoundly affects ridge crest segmentation over time. The mechanisms controlling ridge propagation, however, are poorly understood. At the slow spreading Mid-Atlantic Ridge at 21.5°N a seismic refraction and wide-angle reflection profile surveyed the crustal structure along a segment controlled by rapid ridge propagation. Tomographic traveltime inversion of seismic data suggests that the crustal structure along the ridge axis is controlled by melt supply; thus, crust is thickest, 8 km, at the domed segment center and decreases in thickness toward both segment ends. However, thicker crust is formed in the direction of ridge propagation, suggesting that melt is preferentially transferred toward the propagating ridge tip. Further, while seismic layer 2 remains constant along axis, seismic layer 3 shows profound changes in thickness, governing variations in total crustal thickness. This feature supports mantle upwelling at the segment center. Thus, fluid basaltic melt is redistributed easily laterally, while more viscose gabbroic melt tends to crystallize and accrete nearer to the locus of melt supply. The onset of propagation seems to have coincided with the formation of thicker crust, suggesting that propagation initiation might be due to changes in the melt supply. After a rapid initiation a continuous process of propagation was established. The propagation rate seems to be controlled by the amount of magma that reaches the segment ends. The strength of upwelling may govern the evolution of ridge segments and hence ultimately controls the propagation length.
Published: 2011
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20. Hot spot activity and tectonic settings near Amsterdam–St. Paul plateau (Indian Ocean)

Author: Hervé Guillou, Kevin T. M. Johnson, Marcia Maia, A. Mudholkar, Céline Liorzou, Christophe Hémond, Myriam Janin, Claire Bollinger, Laboratoire Géosciences Océan (LGO), Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-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)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS), University of Hawai‘i [Mānoa] (UHM), 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), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Paléocéanographie (PALEOCEAN), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), School of ocean and earth science and technology, CSIR National Institute of Oceanography [India] (NIO), programmes SEDIT et EXTRAPLAC, Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), and Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], [SDE.MCG]Environmental Sciences/Global Changes, Seamount, Soil Science, [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], Volcanism, Aquatic Science, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Divergent boundary, Paleontology, Geochemistry and Petrology, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, hot spot, Earth and Planetary Sciences (miscellaneous), 14. Life underwater, Suture (geology), Indian Ocean, K‐Ar geochronology, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, geography, ridge-hot spot interaction, geography.geographical_feature_category, ridge–hot spot interaction, Ecology, Forestry, Plume, Indian ocean, Tectonics, K-Ar geochronology, Geophysics, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Magmatism, SEIR, Geology, Seismology, Capricorn plate
Abstract: International audience; [1] The Amsterdam-St. Paul (ASP) plateau is located in the central part of the Indian Ocean and results from the interaction between the ASP hot spot and the Southeast Indian Ridge (SEIR). It is located near the diffuse boundary between the Capricorn and Australian plates. The seamount chain of the Dead Poets (CDP) is northeast of the ASP plateau and may represent older volcanism related to the ASP hot spot; this chain consists of two groups of seamounts: (1) large flat-topped seamounts formed 8-10 Ma and (2) smaller conical seamounts formed during the last 2 Myr. The ASP hot spot has produced two pulses of magmatism that have been ponded under the ASP plateau and erupted along the divergent boundary between the Capricorn and Australian plates. The N65°orientation of the CDP as well as the seamount's elongated shapes support an opening motion between the Capricorn and Australian plates along a suture oriented in the N155°direction. This motion compared to the Antarctic plate amounts to an apparent velocity of 7.7 cm/yr northeastward for the Capricorn-Australian block. This motion does not fit with a fixed plume model. We suggest, therefore, that the ASP plume experienced a motion of about 1-2 cm/yr to the SW, which is opposite to the asthenospheric flow in this region and suggests a deep-seated plume.
Published: 2011
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21. Crustal structure of the southeastern Brazilian margin, Campos Basin, from aeromagnetic data: New kinematic constraints

Author: M. Mane, Marcia Maia, N. Stanton, Renata da Silva Schmitt, Armand Galdeano, Departamento de Geotectonica (UERJ), Universidade do Estado do Rio de Janeiro [Rio de Janeiro] (UERJ), 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), 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), Brazilian Petroleum National Agency, and Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 010504 meteorology & atmospheric sciences, Lineament, Basement inheritance, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], [SDE.MCG]Environmental Sciences/Global Changes, [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], 010502 geochemistry & geophysics, 01 natural sciences, Paleontology, Continental breakup, Passive margin, Onshore–offshore correlation, South American Plate, Suture (geology), Magnetic anomaly, 0105 earth and related environmental sciences, Earth-Surface Processes, Rift, Continental crust, 15. Life on land, Tectonics, Geophysics, Rifting deformation, Aeromagnetic data, Geology, Seismology
Abstract: International audience; The continental and adjacent marginal features along southeast Brazil were investigated, focusing on the basement structural relationships between onshore and offshore provinces. Lateral and vertical variations in the magnetic anomalies provided a good correlation with the regional tectonic features. The sin-rift dykes and faults are associated with the magnetic lineaments and lie sub parallel to the Precambrian N45E–S45W basement structure of the Ribeira Belt, but orthogonally to the Cabo Frio Tectonic Domain (CFTD) basement, implying that: (1) the upper portion of the continental crust was widely affected by Mesozoic extensional deformation; and (2) tectonic features related to the process of break up of the Gondwana at the CFTD were form regardless of the preexisting structural basement orientation being controlled by the stress orientation during the rift phase. The deep crustal structure (5 km depth) is characterized by NE–SW magnetic “provinces” related to the Ribeira Belt tectonic units, while deep suture zones are defined by magnetic lows. The offshore Campos structural framework is N30E–S30W oriented and resulted from a main WNW–ESE direction of extension in Early Cretaceous. Transfer zones are represented by NW–SE and E–W oriented discontinuities. A slight difference in orientation between onshore (N45E) and offshore (N30E) structural systems seems to reflect a re-orientation of stress during rifting. We proposed a kinematical model to explain the structural evolution of this portion of the margin, characterized by polyphase rifting, associated with the rotation of the South American plate. The Campos Magnetic High (CMH), an important tectonic feature of the Campos Basin corresponds to a wide area of high crustal magnetization. The CMH wass interpreted as a magmatic feature, mafic to ultramafic in composition that extends down to 14 km depth and constitutes an evidence of intense crustal extension at 60 km from the coast.
Published: 2010
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22. Volcanism, jump and propagation on the Sheba ridge, eastern Gulf of Aden: segmentation evolution and implications for oceanic accretion processes

Author: Sylvie Leroy, Marcia Maia, Pascal Gente, Elia d'Acremont, Julia Autin, Institut des Sciences de la Terre de Paris (iSTeP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), 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), Université européenne de Bretagne - European University of Brittany (UEB), Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), and Centre National de la Recherche Scientifique (CNRS)-Institut d'écologie et environnement-Observatoire des Sciences de l'Univers-Université de Brest (UBO)-Institut national des sciences de l'Univers (INSU - CNRS)
Subjects: 010504 meteorology & atmospheric sciences, Magnetic anomalies: modelling and interpretation, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], [SDE.MCG]Environmental Sciences/Global Changes, [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], Crustal structure, 010502 geochemistry & geophysics, 01 natural sciences, Continental margin, Geochemistry and Petrology, Oceanic crust, Mid-ocean ridge processes, 14. Life underwater, 0105 earth and related environmental sciences, Oceanic hotspots and intraplate volcanism, Gravity anomalies and Earth structure, geography, geography.geographical_feature_category, Rift, Oceanic transform and fracture zone processes, Transform fault, Mid-ocean ridge, Seafloor spreading, Geophysics, Ridge, Oceanic basin, Geology, Seismology
Abstract: International audience; The rifting between Arabia and Somalia, which started around 35 Ma, was followed by oceanic accretion from at least 17.6 Ma leading to the formation of the present-day Gulf of Aden. Bathymetric, gravity and magnetic data from the Encens-Sheba cruise are used to constrain the structure and segmentation of the oceanic basin separating the conjugate continental margins in the eastern part of the Gulf of Aden between 51 degrees E and 55.5 degrees E. Data analysis reveals that the oceanic domain along this ridge section is divided into two distinct areas. The Eastern area is characterized by a shorter wavelength variation of the axial segmentation and an extremely thin oceanic crust. In the western segment, a thicker oceanic crust suggests a high melt supply. This supply is probably due to an off-axis melting anomaly located below the southern flank of the Sheba ridge, 75 km east of the major Alula-Fartak transform fault. This suggests that the axial morphology is produced by a combination of factors, including spreading rate, melt supply and the edge effect of the Alula-Fartak transform fault, as well as the proximity of the continental margin. The oceanic domains have undergone two distinct phases of accretion since the onset of seafloor spreading, with a shift around 11 Ma. At that time, the ridge jumped southwards, in response to the melting anomaly. Propagating ridges were triggered by the melting activity, and propagated both eastward and westward. The influence of the melting anomaly on the ridges decreased, stopping their propagation since less than 9 Ma. From that time up to the present, the N025 degrees E-trending Socotra transform fault developed in association with the formation of the N115 degrees E-trending segment #2. In recent times, a counter-clockwise rotation of the stress field associated with kinematic changes could explain the structural morphology of the Alula-Fartak and Socotra-Hadbeen fracture zones.
Published: 2010
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23. Ocean gravity models from future satellite missions

Author: Didier Rouxel, Marcia Maia, Gilles Louis, Marie-Françoise Lequentrec-Lalancette, Mathilde Faillot, Jean-Yves Royer, Louis Géli, 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), Université européenne de Bretagne - European University of Brittany (UEB), Service Hydrographique et Océanographique de la Marine (SHOM), Ministère de la Défense, Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), and Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)
Subjects: 010504 meteorology & atmospheric sciences, Meteorology, high resolution, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], [SDE.MCG]Environmental Sciences/Global Changes, European Combined Geodetic Network, Geodetic datum, [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], Sea-surface height, 010502 geochemistry & geophysics, Geodesy, 01 natural sciences, European Remote-Sensing Satellite, Ocean surface topography, SWAT soil and water assessment tool, altimetry, Geoid, General Earth and Planetary Sciences, Satellite, 14. Life underwater, Altimeter, Geology, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract: Over the past 3 decades, satellite altimetry has been a key tool for dynamic ocean studies and for accurately estimating sea surface heights. The geodetic reference surface—the “geoid”—can be approximated as the mean sea surface height of an ocean corrected for dynamic terms such as tides and currents. It is an equipotential surface of the gravity field; and variations of this field are quantified as free-air anomalies, from which density heterogeneities of the oceanic basement can be inferred. Using such data in combination with other geophysical data, scientists have improved their knowledge of the nature of submarine relief and underlying structures. In solid Earth geophysics, major breakthroughs came from the development of high-resolution marine gravity models based on closely spaced altimetry profiles collected during the U.S. Navy's Geosat satellite geodetic mission (launched in 1985) and the first version of the European Remote Sensing satellite geodetic mission (ERS 1, launched in 1991). These were combined with other repetitive profiles from the international TOPEX/ POSEIDON satellite (launched in 1992); ERS 1; TOPEX/POSEIDON's successor, Jason (launched in 2001); and the European Space Agency's (ESA) Envisat missions (ERS's successors [see, e.g., Sandwell and Smith, 1997; Andersen and Knudsen, 1998]).
Published: 2010
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24. Seismic structure of an oceanic core complex at the Mid-Atlantic Ridge, 22°19′N

Author: Marcia Maia, Ingo Grevemeyer, Georges Ceuleneer, Anke Dannowski, Pascal Gente, César R. Ranero, Jason Phipps Morgan, Leibniz-Institut für Meereswissenschaften (IFM-GEOMAR), Institució Catalana de Recerca i Estudis Avançats (ICREA), Dynamique terrestre et planétaire (DTP), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), 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), Université européenne de Bretagne - European University of Brittany (UEB), EAS Department, Cornell University [New York], Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, mid-ocean ridge, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], [SDE.MCG]Environmental Sciences/Global Changes, oceanic core complex, seismic tomography, Soil Science, [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], Mid-Atlantic Ridge, Aquatic Science, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Geochemistry and Petrology, Lithosphere, Oceanic crust, Earth and Planetary Sciences (miscellaneous), 14. Life underwater, Seismic refraction, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, geography, geography.geographical_feature_category, Ecology, Paleontology, Forestry, Crust, Mid-ocean ridge, Oceanic core complex, Geophysics, Space and Planetary Science, Seismic tomography, Seismology, Geology
Abstract: 15 pages, 9 figures, We present results from a seismic refraction and wide-angle experiment surveying an oceanic core complex on the Mid-Atlantic Ridge at 2219N. Oceanic core complexes are settings where petrological sampling found exposed lower crustal and upper mantle rocks, exhumed by asymmetric crustal accretion involving detachment faulting at magmatically starved ridge sections. Tomographic inversion of our seismic data yielded lateral variations of P wave velocity within the upper 3 to 4 km of the lithosphere across the median valley. A joint modeling procedure of seismic P wave travel times and marine gravity field data was used to constrain crustal thickness variations and the structure of the uppermost mantle. A gradual increase of seismic velocities from the median valley to the east is connected to aging of the oceanic crust, while a rapid change of seismic velocities at the western ridge flank indicates profound differences in lithology between conjugated ridge flanks, caused by un-roofing lower crust rocks. Under the core complex crust is approximately 40% thinner than in the median valley and under the conjugated eastern flank. Clear PmP reflections turning under the western ridge flank suggest the creation of a Moho boundary and hence continuous magmatic accretion during core complex formation, The research was funded by the German Science Foundation (DFG) (grants Mo 961‐5/1 Ra 925‐5/1 Gr 1964‐8/2+8/3)
Published: 2010
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25. A seafloor experiment to monitor vertical deformation at the Lucky Strike volcano, Mid-Atlantic Ridge

Author: Valérie Ballu, Michel Diament, Mathilde Cannat, Gilles Reverdin, Marie-Noëlle Bouin, Olivier de Viron, Sébastien Deroussi, Marcia Maia, Christine Deplus, Olivier Pot, Glenn S. Sasagawa, Jérôme Ammann, 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), IRD, Géoazur (GEOAZUR 6526), Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Université européenne de Bretagne - European University of Brittany (UEB), 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), Institute of Geophysics and Planetary Physics [San Diego] (IGPP), Scripps Institution of Oceanography (SIO), University of California [San Diego] (UC San Diego), University of California-University of California-University of California [San Diego] (UC San Diego), University of California-University of California, Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), LAboratoire de Recherche en Géodésie (LAREG), Ecole nationale des sciences géographiques (ENSG), Institut géographique national [IGN] (IGN)-Institut géographique national [IGN] (IGN), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-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)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Scripps Institution of Oceanography (SIO - UC San Diego), University of California (UC)-University of California (UC)-University of California [San Diego] (UC San Diego), University of California (UC)-University of California (UC), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL)
Subjects: 010504 meteorology & atmospheric sciences, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], [SDE.MCG]Environmental Sciences/Global Changes, [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], Mid-Atlantic Ridge, Deformation (meteorology), 010502 geochemistry & geophysics, 01 natural sciences, MoMAR, Geochemistry and Petrology, Observatory, Pressure, Seafloor, Computers in Earth Sciences, Volcano, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, Geodesy, Seafloor spreading, Deformation, Geophysics, Ridge, Accretion (geology), Seismology, Geology, Hydrothermal vent
Abstract: International audience; Decades of cruise-based exploration have provided excellent snapshots of the structure of mid-ocean ridges and have revealed that accretion is a mixture of steady-state and quantum events. Observatory-type studies are now needed to quantify the temporal evolution of these systems. A multi-disciplinary seafloor observatory site is currently being set up at the Lucky Strike volcano, in the axial valley of the slow spreading Mid-Atlantic ridge as a part of the MoMAR (monitoring of the Mid-Atlantic Ridge) initiative. The aim of this observatory is to better understand the dynamics of the volcano and the hydrothermal vents hosted at its summit as well as their plumbing systems. In August 2006, the GRAVILUCK cruise initiated an experiment to monitor the deformation of Lucky Strike volcano. A geodetic network was installed, and seafloor pressure, gravity and magnetic data were collected. In this paper, we present the method used to monitor volcanic deformation, which involves measuring relative depth difference between points within a seafloor geodesy network. We show that, taking into account oceanographic variability and measurement noise, the network should be able to detect vertical deformations of the order of 1 cm.
Published: 2009
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26. Evolution of the accretion processes along the Mid-Atlantic Ridge north of the Azores since 5.5 Ma: An insight into the interactions between the ridge and the plume

Author: Marcia Maia, Jean Goslin, and Pascal Gente
Subjects: geography, Plateau, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Mid-ocean ridge, Mid-Atlantic Ridge, 010502 geochemistry & geophysics, 01 natural sciences, Plume, Paleontology, Geophysics, Ridge push, Geochemistry and Petrology, Magmatism, Ridge (meteorology), 14. Life underwater, Accretion (geology), Geomorphology, Geology, 0105 earth and related environmental sciences
Abstract: [1] High-resolution bathymetry and gravity data north of the Azores Plateau show that this part of the North Mid-Atlantic Ridge is presently undergoing a phase of weak crustal production and magmatism. Most of the ridge segments are small and short-lived, suggesting a disrupted and highly variable accretion regime since anomaly 3A. The influence of the nearby plume appears to be relatively minor and corresponds more to a weak thermal signal than to any major input of plume material and increased crustal production at the axis. A period of increased magmatism was identified at the southern limit of the study area (near 40°N) around anomaly 5. This magmatic “pulse” caused the emplacement of a topographic high, probably underlain by a thickened crust. This pulse probably marks the northernmost and last significant arrival of material from the Azores plume to the MAR axis.
Published: 2007
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27. Structure and evolution of the eastern Gulf of Aden: insights from magnetic and gravity data (Encens-Sheba MD117 cruise)

Author: Elia d'Acremont, Nicolas Bellahsen, Marcia Maia, Marc Fournier, Pascal Gente, Sylvie Leroy, Marie-Odile Beslier, Philippe Patriat, Domaines Océaniques (LDO), Centre National de la Recherche Scientifique (CNRS)-Institut d'écologie et environnement-Observatoire des Sciences de l'Univers-Université de Brest (UBO)-Institut national des sciences de l'Univers (INSU - CNRS), Géoazur (GEOAZUR 6526), Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Institut des Sciences de la Terre de Paris (iSTeP), Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS), 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), Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, and COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Gulf of Aden, passive continental margin, 010504 meteorology & atmospheric sciences, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], [SDE.MCG]Environmental Sciences/Global Changes, [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], 010502 geochemistry & geophysics, 01 natural sciences, Continental margin, Geochemistry and Petrology, Passive margin, Oceanic crust, 14. Life underwater, seafloor spreading, Magnetic anomaly, 0105 earth and related environmental sciences, kinematic evolution, geography, geography.geographical_feature_category, Continental crust, segmentation, Mid-ocean ridge, Crust, Seafloor spreading, Geophysics, ocean-continent transition, Seismology, Geology
Abstract: International audience; Magnetic and gravity data gathered during the Encens-Sheba cruise (2000 June) in the eastern Gulf of Aden provide insights on the structural evolution of segmentation from rifted margins to incipient seafloor spreading. In this study, we document the conjugate margins asymmetry, confirm the location of the ocean–continent transition (OCT) previously proposed by seismic data, and describe its deep structure and segmentation. In the OCT, gravity models indicate highly thinned crust while magnetic data indicate presence of non-oceanic high-amplitude magnetic anomalies where syn-rift sediments are not observed. Thus, the OCT could be made of ultra-stretched continental crust intruded by magmatic bodies. However, locally in the north, the nature of the OCT could be either an area of ultra-slow spreading oceanic crust or exhumed serpentinized mantle. Between the Alula-Fartak and Socotra fracture zones, the non-volcanic margins and the OCT are segmented by two N027°E-trending transfer fault zones. These transfer zones define three N110°E-trending segments that evolve through time. The first evidence of oceanic spreading corresponds to the magnetic anomaly A5d and is thus dated back to 17.6 Ma at least. Reconstruction of the spreading process suggests a complex non-uniform opening by an arc-like initiation of seafloor spreading in the OCT. The early segmentation appears to be directly related to the continental margin segmentation. The spreading axis segmentation evolved from three segments (17.6 to 10.95 Ma) to two segments (10.95 Ma to present). At the onset of the spreading process, the western segment propagated eastwards, thus reducing the size of the central segment. The presence of a propagator could explain the observed spreading asymmetry with the northern flank of the Sheba ridge being wider than the southern one.
Published: 2006
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28. Structure and evolution of the eastern Gulf of Aden conjugate margins from seismic reflection data

Author: Pascal Gente, Marc Fournier, Nicolas Bellahsen, Cécile Robin, Sylvie Leroy, Elia d'Acremont, Marie-Odile Beslier, Marcia Maia, Laboratoire de tectonique (LT), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), Institut des Sciences de la Terre de Paris (iSTeP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Géoazur (GEOAZUR 6526), Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), IFP Energies nouvelles (IFPEN), Géosciences Rennes (GR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre Armoricain de Recherches en Environnement-Centre National de la Recherche Scientifique (CNRS), 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), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-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)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre Armoricain de Recherches en Environnement-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), and Centre National de la Recherche Scientifique (CNRS)-Institut d'écologie et environnement-Observatoire des Sciences de l'Univers-Université de Brest (UBO)-Institut national des sciences de l'Univers (INSU - CNRS)
Subjects: Gulf of Aden, Volcanic passive margin, 010504 meteorology & atmospheric sciences, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, 010502 geochemistry & geophysics, 01 natural sciences, Paleontology, Continental margin, Geochemistry and Petrology, Oceanic crust, Passive margin, plate divergence, 14. Life underwater, seafloor spreading, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, Rift, rifted margin, Continental shelf, Continental crust, Seafloor spreading, Geophysics, continental margins, ocean-continent transition, Geology, Seismology
Abstract: The Gulf of Aden is a young and narrow oceanic basin formed in Oligo-Miocene time between the rifted margins of the Arabian and Somalian plates. Its mean orientation, N75 degrees E, strikes obliquely (50 degrees) to the N25 degrees E opening direction. The western conjugate margins are masked by Oligo-Miocene lavas from the Afar Plume. This paper concerns the eastern margins, where the 19-35 Ma breakup structures are well exposed onshore and within the sediment-starved marine shelf. Those passive margins, about 200 km distant, are non-volcanic. Offshore, during the Encens-Sheba cruise we gathered swath bathymetry, single-channel seismic reflection, gravity and magnetism data, in order to compare the structure of the two conjugate margins and to reconstruct the evolution of the thinned continental crust from rifting to the onset of oceanic spreading. Between the Alula-Fartak and Socotra major fracture zones, two accommodation zones trending N25 degrees E separate the margins into three N110 degrees E-trending segments. The margins are asymmetric: offshore, the northern margin is narrower and steeper than the southern one. Including the onshore domain, the southern rifted margin is about twice the breadth of the northern one. We relate this asymmetry to inherited Jurassic/Cretaceous rifts. The rifting obliquity also influenced the syn-rift structural pattern responsible for the normal faults trending from N70 degrees E to N110 degrees E. The N110 degrees E fault pattern could be explained by the decrease of the influence of rift obliquity towards the central rift, and/or by structural inheritance. The transition between the thinned continental crust and the oceanic crust is characterized by a 40 km wide zone. Our data suggest that its basement is made up of thinned continental crust along the southern margin and of thinned continental crust or exhumed mantle, more or less intruded by magmatic rocks, along the northern margin.
Published: 2005
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29. Intraplate versus ridge volcanism on the Pacific-Antarctic Ridge near 37°S -111°W

Author: Marcia Maia, Roger Hekinian, Nicolas Binard, Christophe Hémond, Colin W. Devey, John O'Connor, Peter Stoffers, and Dietrich Ackerman
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, Seamount, Geochemistry, Soil Science, Mineralogy, Aquatic Science, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, Basalt, geography, geography.geographical_feature_category, Ecology, Pacific Plate, Paleontology, Forestry, Mid-ocean ridge, Volcanic rock, Geophysics, Volcano, Space and Planetary Science, Ridge, Magmatism, Geology
Abstract: Exploration of the Foundation Volcanic Chain (33 degrees S-131 degrees W; 37 degrees S-111 degrees W) revealed the existence of different magmatic provinces with relation to their geological settings. (1) The Pacific-Antarctic Ridge (PAR) is made up of several en echelon segments where both glassy midocean ridge basalts (MORBs) with low incompatible elements (K2O150 ppm) and Ce (>48 ppm)) at about 306-1300 km from the PAR axis, (4) The Old Pacific Seamounts built on a crust older than 23 m. y. located west of longitude 124 degrees W (> 1300 km from the PAR axis) consist of T and EMORB. On the PAR axis, extensive crystal fractionation (>65%) produced the silicic lavas. On the basis of Pacific plate reconstruction using a half spreading rate of about 50 mm/yr and integrating the observed compositional changes with respect to the structural settings, it is inferred that the last volcanic events giving rise to the FS took place at about 110 km from the PAR axis about 5 m. y. ago. The Oblique Ridges built between 5 m. y. and 23 m. y.) with MORB volcanics comparable to those of the the Oblique Ridge-PAR provinces, could also have been formed by an interaction between the Foundation Seamount (dredge site 28) hotspot magmatism and that of an ancient accreting ridge magmatism precursor of the PAR.

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29 results on '"Marcia Maia"'

1. Uppermost Mantle Velocity beneath the Mid-Atlantic Ridge and Transform Faults in the Equatorial Atlantic Ocean

2. Occurrence of Omura’s whale, Balaenoptera omurai (Cetacea: Balaenopteridae), in the Equatorial Atlantic Ocean based on Passive Acoustic Monitoring

3. Semibrittle seismic deformation in high-temperature mantle mylonite shear zone along the Romanche transform fault

4. Variable Crustal Production Originating From Mantle Source Heterogeneity Beneath the South East Indian Ridge and Amsterdam‐St. Paul Plateau

5. Joint inversion of gravity and surface wave data constrained by magnetotelluric: Application to deep geothermal exploration of crustal fault zone in felsic basement

6. Antarctic blue whales ( Balaenoptera musculus intermedia ) recorded at the Equator in the Atlantic Ocean

7. Seafloor evidence for pre-shield volcanism above the Tristan da Cunha mantle plume

8. Topographic and Morphologic Evidences of Deformation at Oceanic Transform Faults: Far-Field and Local-Field Stresses

9. The August 2010 earthquake swarm at North FAMOUS–FAMOUS segments, Mid-Atlantic Ridge: geophysical evidence of dike intrusion

10. Geophysical fingerprints of hyper-extended, exhumed and embryonic oceanic domains: the example from the Iberia–Newfoundland rifted margins

11. Extreme mantle uplift and exhumation along a transpressive transform fault

12. Subsurface structure and stratigraphy of the northwest end of the Turkana Basin, Northern Kenya Rift, as revealed by magnetotellurics and gravity joint inversion

13. Constraints on age and construction process of the Foundation chain submarine volcanoes from magnetic modeling

14. From rifting to spreading in the eastern Gulf of Aden: a geophysical survey of a young oceanic basin from margin to margin

15. 40 Ar/ 39 Ar geochronology and structural data from the giant Okavango and related mafic dyke swarms, Karoo igneous province, northern Botswana

16. Correlated patterns in hydrothermal plume distribution and apparent magmatic budget along 2500 km of the Southeast Indian Ridge

17. The Amsterdam-St. Paul Plateau: A complex hot spot/DUPAL-flavored MORB interaction

18. Building of the Amsterdam-Saint Paul plateau: A 10 Myr history of a ridge-hot spot interaction and variations in the strength of the hot spot source

19. Crustal structure of the propagating TAMMAR ridge segment on the Mid-Atlantic Ridge, 21.5°N

20. Hot spot activity and tectonic settings near Amsterdam–St. Paul plateau (Indian Ocean)

21. Crustal structure of the southeastern Brazilian margin, Campos Basin, from aeromagnetic data: New kinematic constraints

22. Volcanism, jump and propagation on the Sheba ridge, eastern Gulf of Aden: segmentation evolution and implications for oceanic accretion processes

23. Ocean gravity models from future satellite missions

24. Seismic structure of an oceanic core complex at the Mid-Atlantic Ridge, 22°19′N

25. A seafloor experiment to monitor vertical deformation at the Lucky Strike volcano, Mid-Atlantic Ridge

26. Evolution of the accretion processes along the Mid-Atlantic Ridge north of the Azores since 5.5 Ma: An insight into the interactions between the ridge and the plume

27. Structure and evolution of the eastern Gulf of Aden: insights from magnetic and gravity data (Encens-Sheba MD117 cruise)

28. Structure and evolution of the eastern Gulf of Aden conjugate margins from seismic reflection data

29. Intraplate versus ridge volcanism on the Pacific-Antarctic Ridge near 37°S -111°W

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