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A thin mantle transition zone beneath the equatorial Mid-Atlantic Ridge. | LitMetric

AI Article Synopsis

  • * Using ocean bottom seismic data, the research identifies notable uplift and depression of seismic discontinuities at 660 km and 410 km depths, suggesting a thinning of the mantle transition zone.
  • * The findings indicate that this material transfer at the Mid-Atlantic Ridge may demonstrate a significant influence of whole-mantle convection, where rises of magma (upwellings) help balance the sinking of tectonic plates (slab downwellings).

Article Abstract

The location and degree of material transfer between the upper and lower mantle are key to the Earth's thermal and chemical evolution. Sinking slabs and rising plumes are generally accepted as locations of transfer, whereas mid-ocean ridges are not typically assumed to have a role. However, tight constraints from in situ measurements at ridges have proved to be challenging. Here we use receiver functions that reveal the conversion of primary to secondary seismic waves to image the discontinuities that bound the mantle transition zone, using ocean bottom seismic data from the equatorial Mid-Atlantic Ridge. Our images show that the seismic discontinuity at depths of about 660 kilometres is broadly uplifted by 10 ± 4 kilometres over a swath about 600 kilometres wide and that the 410-kilometre discontinuity is depressed by 5 ± 4 kilometres. This thinning of the mantle transition zone is coincident with slow shear-wave velocities in the mantle, from global seismic tomography. In addition, seismic velocities in the mantle transition zone beneath the Mid-Atlantic Ridge are on average slower than those beneath older Atlantic Ocean seafloor. The observations imply material transfer from the lower to the upper mantle-either continuous or punctuated-that is linked to the Mid-Atlantic Ridge. Given the length and longevity of the mid-ocean ridge system, this implies that whole-mantle convection may be more prevalent than previously thought, with ridge upwellings having a role in counterbalancing slab downwellings.

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Source
http://dx.doi.org/10.1038/s41586-020-03139-xDOI Listing

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