The Iceland Plume rising from beneath Greenland imaged by waveform tomography
Abstract
The mantle structure of the Iceland Plume and its effects on the topography and geology of the North Atlantic region are still debated. We obtain a new image of the North Atlantic region's upper mantle by computing an azimuthally anisotropic, S-wave tomographic model, using waveform inversion. Our new model is constrained by a very large global dataset, including a significant amount of new regional data. The resolution of the model varies in concert with data sampling, which is implemented using regularisation coefficients that vary in 3D with the variations of data sensitivity. The regularisation scaling avoids over-damping of the less sampled regions and over-smoothing of the best sampled ones. We parameterise our model with a triangular grid with nearly uniform, ~120 km lateral knot spacing and with vertical spacing increasing with depth, from 13-16 km in the crust and upper mantle to 125-150 km in the mantle transition zone and the uppermost lower mantle. In the asthenosphere, under the Reykjanes- and west of the Kolbeinsey and Mohns Ridges, low velocities are much stronger than under Mid-Ocean Ridges on the rest the globe. Both in the oceanic lithosphere and underlying asthenosphere, velocities are lower under the Greenland than on the European plate, with minima located west of the ridge. In the transition zone, low-velocities locate under central-eastern Greenland and connect to the ones imaged close to Iceland in the shallow mantle. These images are consistent with a large upwelling of hot mantle, rooted under Greenland in the transition zone and deflected towards Iceland by the keel of the Greenland Craton. While they differ from the classic view of a narrow, vertical mantle plume under Iceland, the anomalously low velocities and their agreement with the complex distribution of past and present-day volcanism suggest that they are representative of the Iceland Plume. Our observations suggests an interplay between the plume, the cratonic and oceanic lithosphere and spreading ridge. While the Greenland craton may have driven the plume flow patterns mostly during the Cenozoic---when it was located on top of the plume root--- the spreading MOR seems to channel and confine the plume under the Greenland plate at present-day, in agreement with evidences of recent, intraplate volcanism.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.T14B..06C
- Keywords:
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- 8120 Dynamics of lithosphere and mantle: general;
- TECTONOPHYSICS;
- 8121 Dynamics: convection currents;
- and mantle plumes;
- TECTONOPHYSICS;
- 8170 Subduction zone processes;
- TECTONOPHYSICS;
- 8180 Tomography;
- TECTONOPHYSICS