• 'Mantle wind' blows through slab window

    From ScienceDaily@1337:3/111 to All on Mon Nov 22 21:30:28 2021
    'Mantle wind' blows through slab window beneath Panama
    A Woods Hole Oceanographic Institution-led team unravels the existence of
    a 900-mile-long mantle conduit between the Galapagos and Central America

    November 22, 2021
    Woods Hole Oceanographic Institution
    Volcanic gases are helping researchers track large-scale movements
    in Earth's deep interior. Scientists have discovered anomalous
    geochemical compositions beneath Panama.

    FULL STORY ========================================================================== Volcanic gases are helping researchers track large-scale movements
    in Earth's deep interior.Woods Hole Oceanographic Institution (WHOI) scientists, together with a group of international collaborators, have discovered anomalous geochemical compositions beneath Panama.

    This interdisciplinary team used helium isotopes and other geochemical
    data from fluids and rocks to show that volcanic material is sourced from
    the Galapagos plume, over 900 miles (1500 km) away. The findings of this
    study, "High 3He/4He in central Panama reveals a distal connection to
    the Gala'pagos plume," were published today in the journal Proceedings
    of the National Academy of Sciences.

    "The lateral transport of plume material represents an understudied
    mechanism that scatters enriched geochemical signatures in mantle domains
    far from plumes," said David Bekaert, postdoctoral scholar at WHOI,
    and lead author of the paper.

    "We can compare volcanic systems to the body of a living organism;
    when the organism bleeds, it's kind of like magma bleeding out of the
    Earth. And you can measure the composition of that magma, just like you
    can measure a blood type.

    In this study, we measured an unexpected volcanic gas composition, sort
    of like when a human has a rare blood type. In the case of the Earth,
    we then try to explain where it came from in terms of deep geological processes." The team showed that relatively hot material originating
    from Earth's deep interior travels laterally through the shallow mantle, similar to wind blowing at Earth's surface. Chemical observations were
    combined with geophysical imaging of Earth's deep interior to pinpoint
    the source and direction of this so-called "mantle wind." Typically,
    material cannot easily pass through a subduction zone, where the edge
    of a tectonic plate, called a "slab," acts as a barrier. However,
    the region beneath Panama is unusual in that there appears to be a
    "slab window" that allows this mantle wind to blow through. Overall,
    this study tells us that, even after billions of years of evolution,
    our planet remains a dynamic system marked by large-scale movements of
    solid material, miles beneath our feet.

    "Exotic volcanic chemical features have previously been documented in
    Central America. We use these chemical characteristics as indicators for
    large geological processes. In this case, our findings help explain why plume-derived volcanic material shows up in central Panama, even though
    there are no active volcanoes there," added Bekaert.

    "Our work suggests that small bits of deep mantle material were carried by 'mantle wind' blowing through the window in the subduction zone. Broadly speaking, this informs us about the nature and extent of large-scale
    mixing processes that contribute to the heterogeneous, or diversified,
    nature of the solid Earth" said Peter Barry, assistant scientist at WHOI
    and senior author of the paper.

    Many of the study's samples were collected over the past 15 years, but
    only in light of the insights from other disciplines of geoscience --
    such as geophysics and lava studies -- did the message from helium
    isotopes become clear.

    The geochemical composition of Earth's interior is highly diverse. It
    has been well established that rising plumes of superheated rock in
    Earth's mantle are the main channels for transporting geochemically
    enriched material deep underground, but the extent to which lateral flow processes disperse mantle material far from vertical plumes, remains
    widely unknown. The finding of lateral transport of deep, exotic material across the Earth's interior could have far-reaching implications for scientist's understanding of the chemical evolution of our planet over geological time.

    ========================================================================== Story Source: Materials provided by
    Woods_Hole_Oceanographic_Institution. Note: Content may be edited for
    style and length.

    ========================================================================== Journal Reference:
    1. David V. Bekaert, Esteban Gazel, Stephen Turner, Mark D. Behn,
    J. Marten
    de Moor, Sabin Zahirovic, Vlad C. Manea, Kaj Hoernle, Tobias
    P. Fischer, Alexander Hammerstrom, Alan M. Seltzer, Justin
    T. Kulongoski, Bina S.

    Patel, Matthew O. Schrenk, Saemundur A. Halldo'rsson, Mayuko
    Nakagawa, Carlos J. Rami'rez, John A. Krantz, Mustafa Yu"cel,
    Christopher J.

    Ballentine, Donato Giovannelli, Karen G. Lloyd, Peter H. Barry. High
    3He/ 4He in central Panama reveals a distal connection to the
    Gala'pagos plume. Proceedings of the National Academy of Sciences,
    2021; 118 (47): e2110997118 DOI: 10.1073/pnas.2110997118 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2021/11/211122135425.htm

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