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    Deep explosive volcanism on the Gakkel Ridge and seismological constraints on shallow recharge at TAG active mound

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    Pontbriand_thesis.pdf (49.99Mb)
    Date
    2013-02
    Author
    Pontbriand, Claire W.  Concept link
    Metadata
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    Citable URI
    https://hdl.handle.net/1912/5761
    Location
    Gakkel Ridge
    85°E
    DOI
    10.1575/1912/5761
    Keyword
     Volcanic eruptions; Volcanology 
    Abstract
    Seafloor digital imagery and bathymetric data are used to evaluate the volcanic characteristics of the 85°E segment of the ultraslow spreading Gakkel Ridge (9 mm yr-1). Imagery reveals that ridges and volcanic cones in the axial valley are covered by numerous, small-volume lava flows, including a few flows fresh enough to have potentially erupted during the 1999 seismic swarm at the site. The morphology and distribution of volcaniclastic deposits observed on the seafloor at depths of ~3800 m, greater than the critical point for steam generation, are consistent with having formed by explosive discharge of magma and CO2 from source vents. Microearthquakes recorded on a 200 m aperture seismometer network deployed on the Trans-Atlantic Geotraverse active mound, a seafloor massive sulfide on the Mid-Atlantic Ridge at 26°N, are used to image subsurface processes at the hydrothermal system. Over nine-months, 32,078 local microearthquakes (ML = -1) with single-phase arrivals cluster on the southwest flank of the deposit at depths <125 m. Microearthquakes characteristics are consistent with reaction-driven cracking driven by anhydrite deposition in the shallow secondary circulation system. Exit fluid temperatures recorded at diffuse vents on the mound during the microearthquake study are used to explore linkages between seismicity and venting.
    Description
    Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2013
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    • WHOI Theses
    • Geology and Geophysics (G&G)
    Suggested Citation
    Thesis: Pontbriand, Claire W., "Deep explosive volcanism on the Gakkel Ridge and seismological constraints on shallow recharge at TAG active mound", 2013-02, DOI:10.1575/1912/5761, https://hdl.handle.net/1912/5761
     

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