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  • 1
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    Lucky Strike seamount : implications for the emplacement and rifting of segment-centered volcanoes at slow spreading mid-ocean ridges (2015)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 15 (2014): 4157–4179, doi:10.1002/2014GC005477.
    Description: The history of emplacement, tectonic evolution, and dismemberment of a central volcano within the rift valley of the slow spreading Mid-Atlantic Ridge at the Lucky Strike Segment is deduced using near-bottom sidescan sonar imagery and visual observations. Volcano emplacement is rapid (〈1 Myr), associated with focused eruptions, and with effusion rates feeding lava flows that bury tectonic features developed prior to and during volcano construction. This volcanic phase likely requires efficient melt pooling and a long-lived crustal magma chamber as a melt source. A reduction in melt supply triggers formation of an axial graben rifting the central volcano, and the onset of seafloor spreading may eventually split it. At Lucky Strike, this results in two modes of crustal construction. Eruptions and tectonic activity focus at a narrow graben that bisects the central volcano and contains the youngest lava flows, accumulating a thick layer of extrusives. Away from the volcano summit, deformation and volcanic emplacement is distributed throughout the rift valley floor, lacking a clear locus of accretion and deformation. Volcanic emplacement on the rift floor is characterized by axial volcanic ridges fed by dikes that propagate from the central axial magma chamber. The mode of rapid volcano construction and subsequent rifting observed at the Lucky Strike seamount is common at other central volcanoes along the global mid-ocean ridge system.
    Description: he TowCam delployment for seafloor imaging during the Graviluck'06 cruise was supported by NSF grant OCE-0623744 to A.S. and D.J.F., and by WHOI Deep Ocean Exploration Institute funding (AS & DF). D.J.F. also benefitted from a visiting position at IPGP to carry out this work. The field data acquisition for the Lustre'96 cruise was supported by NSF grant OCE-9505579. The Flores, Sudaçores, and SISMOMAR cruises where funded by CNRS/IFREMER (France).
    Description: 2015-05-07
    Keywords: Mid-ocean ridges ; Volcanism ; Tectonics ; Rifting ; Sonar ; Faulting
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
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    Hydrothermal activity along the slow-spreading Lucky Strike ridge segment (Mid-Atlantic Ridge) : distribution, heatflux, and geological controls (2015)
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    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Earth and Planetary Science Letters 431 (2015): 1730185, doi:10.1016/j.epsl.2015.09.025.
    Description: We have reviewed available visual information from the seafloor, and recently acquired microbathymetry for several traverses across the Lucky Strike segment, to evaluate the distribution of hydrothermal activity. We have identified a new on-axis site with diffuse flow, Ewan, and anactive vent structure ~1.2 km from the axis, Capelinhos. These sites are minor relative to the Main field, and our total heatflux estimate for all active sites (200-1200 MW) is only slightly higher than previously published estimates. We also identify fossil sites W of the main Lucky Strike field. A circular feature ~200 m in diameter located on the flanks of a rifted off-axis central volcano, is likely a large and inactive hydrothermal edifice, named Grunnus. We find no indicator of focused hydrothermal activity elsewhere along the segment, suggesting that the enhanced melt supply and the associated melt lenses, required to form central volcanoes, also sustain hydrothermal circulation to form and maintain large and long-lived hydrothermal fields. Hydrothermal discharge to the seafloor occurs along fault traces, suggesting focusing of hydrothermal circulation in the shallow crust along permeable fault zones.
    Description: This work has been partly financed by ANR (France) Mothseim Project NT05-3 42213 toJE, and by EU-RTN-MOMARNET to MC. The French Ministry of Research financed ship, ROV and AUV time (Graviluck’06, MOMAR’08, Bathyluck’09, MOMARSAT cruises in 2010-2015)
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 3
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    Magmatic plumbing at Lucky Strike volcano based on olivine-hosted melt inclusion compositions (2015)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 16 (2015): 126–147, doi:10.1002/2014GC005517.
    Description: Here we present volatile, major, and trace element concentrations of 64 olivine-hosted melt inclusions from the Lucky Strike segment on the mid-Atlantic ridge. Lucky Strike is one of two locations where a crustal melt lens has been seismically imaged on a slow-spreading ridge. Vapor-saturation pressures, calculated from CO2 and H2O contents of Lucky Strike melt inclusions, range from approximately 300–3000 bars, corresponding to depths of 0.5–9.9 km below the seafloor. Approximately 50% of the melt inclusions record crystallization depths of 3–4 km, corresponding to the seismically imaged melt lens depth, while an additional ∼35% crystallize at depths 〉 4 km. This indicates that while crystallization is focused within the melt lens, significant crystallization also occurs in the lower crust and/or upper mantle. The melt inclusions span a range of major and trace element concentrations from normal to enriched basalts. Trace element ratios at all depths are heterogeneous, suggesting that melts are not efficiently homogenized in the mantle or crust, despite the presence of a melt lens. This is consistent with the transient nature of magma chambers proposed for slower-spreading ridges. To investigate the petrogenesis of the melt inclusion compositions, we compare the measured trace element compositions to theoretical melting calculations that consider variations in the melting geometry and heterogeneities in the mantle source. The full range of compositions can be produced by slight variations in the proportion of an Azores plume and depleted upper mantle components and changes in the total extent of melting.
    Description: thanked for his help with sample preparation. The GRAVILUCK'06 and Bathyluck'08 cruises where financed by the French Ministry of Research. This work was supported by NSF grant OCE-0926422 to A.M.S., OCE-PRF-1226130 to V.D.W., OCE-1333492 to S.A.S., and EAR-09-48666 to M.D.B., and by ANR (France) Mothseim Project NT05-342213 to J.E.
    Description: 2015-07-20
    Keywords: Slow-spreading ridge ; Lucky Strike ; Melt inclusions ; Volatiles ; Melt lens
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 4
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    The Kallisti Limnes, carbon dioxide-accumulating subsea pools (2015)
    Nature Publishing Group
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 5 (2015): 12152, doi:10.1038/srep12152.
    Description: Natural CO2 releases from shallow marine hydrothermal vents are assumed to mix into the water column, and not accumulate into stratified seafloor pools. We present newly discovered shallow subsea pools located within the Santorini volcanic caldera of the Southern Aegean Sea, Greece, that accumulate CO2 emissions from geologic reservoirs. This type of hydrothermal seafloor pool, containing highly concentrated CO2, provides direct evidence of shallow benthic CO2 accumulations originating from sub-seafloor releases. Samples taken from within these acidic pools are devoid of calcifying organisms, and channel structures among the pools indicate gravity driven flow, suggesting that seafloor release of CO2 at this site may preferentially impact benthic ecosystems. These naturally occurring seafloor pools may provide a diagnostic indicator of incipient volcanic activity and can serve as an analog for studying CO2 leakage and benthic accumulations from subsea carbon capture and storage sites.
    Description: This research was supported by the Eurofleets Caldera 2012 Project (EU), a NASA Astrobiology Science & Technology for Exploring Planets grant #NNX09AB76G (USA), a CAREER Award grant #OCE-0955674 to R. Camilli from the National Science Foundation (USA), and IPGP (France).
    Repository Name: Woods Hole Open Access Server
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  • 5
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    Tectonic evolution of 200 km of Mid-Atlantic Ridge over 10 million years : interplay of volcanism and faulting (2015)
    John Wiley & Sons
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    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 16 (2015): 2303-2321, doi:10.1002/2015GC005797.
    Description: We reconstruct the history of the mode of accretion of an area of the Mid-Atlantic Ridge south of the Kane fracture zone using bathymetric morphology. The area includes 200 km of the spreading axis and reaches to 10 Ma on either side. We distinguish three tectonic styles: (1) volcanic construction with eruption and intrusion of magma coupled with minor faulting, (2) extended terrain with abundant large-offset faults, (3) detachment faulting marked by extension on single long-lived faults. Over 40% of the seafloor is made of extended terrain and detachment faults. The area includes products of seven spreading segments. The spreading axis has had detachment faulting or extended terrain on one or both sides for 70% of the last 10 Ma. In some parts of the area, regions of detachment faulting and extended terrain lie close to segment boundaries. Regions of detachment faulting initiated at 10 Ma close to the adjacent fracture zones to the north and south, and then expanded away from them. We discuss the complex evidence from gravity, seismic surveys, and bathymetry for the role of magma supply in generating tectonic style. Overall, we conclude that input of magma at the spreading axis has a general control on the development of detachment faulting, but the relationship is not strong. Other factors may include a positive feedback that stabilizes detachment faulting at the expense of volcanic extension, perhaps through the lubrication of active detachment faults by the formation of low friction materials (talc, serpentine) on detachment fault surfaces.
    Description: 2016-01-22
    Keywords: Slow spreading ridges ; Mid-Atlantic Ridge ; Detachment faults
    Repository Name: Woods Hole Open Access Server
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  • 6
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    Sensitivity of seafloor bathymetry to climate-driven fluctuations in mid-ocean ridge magma supply (2015)
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of American Association for the Advancement of Science for personal use, not for redistribution. The definitive version was published in Science 350 (2015): 6258, doi:10.1126/science.aad0715.
    Description: Recent studies have proposed that the bathymetric fabric of the seafloor formed at mid-ocean ridges records rapid (23–100 kyr) fluctuations in ridge magma supply caused by sea level changes that modulate melt production in the underlying mantle. Using quantitative models of faulting and magma emplacement, we demonstrate that, in fact, seafloor-shaping processes act as a low-pass filter on variations in magma supply, strongly damping fluctuations shorter than ~100 kyr. We show that the systematic decrease in dominant seafloor wavelengths with increasing spreading rate is best explained by a model of fault growth and abandonment under a steady magma input. This provides a robust framework for deciphering the footprint of mantle melting in the fabric of abyssal hills, the most common topographic feature on Earth.
    Description: Funding was provided by NSF grants OCE-1154238 (J.-A.O., M.D.B), OCE-1155098 (G.I., S.H.), EAR-1009839 (W.R.B), CNRS support to JE, and an LDEO Postdoctoral Fellowship for J.-A.O.
    Description: 2016-04-16
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 7
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    Magmatic and tectonic extension at the Chile Ridge : evidence for mantle controls on ridge segmentation (2016)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 17 (2016): 2354–2373, doi:10.1002/2016GC006380.
    Description: We use data from an extensive multibeam bathymetry survey of the Chile Ridge to study tectonomagmatic processes at the ridge axis. Specifically, we investigate how abyssal hills evolve from axial faults, how variations in magmatic extension influence morphology and faulting along the spreading axis, and how these variations correlate with ridge segmentation. The bathymetry data are used to estimate the fraction of plate separation accommodated by normal faulting, and the remaining fraction of extension, M, is attributed primarily to magmatic accretion. Results show that M ranges from 0.85 to 0.96, systematically increasing from first-order and second-order ridge segment offsets toward segment centers as the depth of ridge axis shoals relative to the flanking highs of the axial valley. Fault spacing, however, does not correlate with ridge geometry, morphology, or M along the Chile Ridge, which suggests the observed increase in tectonic strain toward segment ends is achieved through increased slip on approximately equally spaced faults. Variations in M along the segments follow variations in petrologic indicators of mantle melt fraction, both showing a preferred length scale of 50 ± 20 km that persists even along much longer ridge segments. In comparison, mean M and axial relief fail to show significant correlations with distance offsetting the segments. These two findings suggest a form of magmatic segmentation that is partially decoupled from the geometry of the plate boundary. We hypothesize this magmatic segmentation arises from cells of buoyantly upwelling mantle that influence tectonic segmentation from the mantle, up.
    Description: NSF grants Grant Number: OCE-11-55098; (S.M.H. and G.I.) and OCE-11-54238
    Description: 2016-12-24
    Keywords: Chile Ridge ; Active upwelling ; Abyssal hill evolution ; Faulting and magmatism ; Ridge morphology
    Repository Name: Woods Hole Open Access Server
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