Linking Lithospheric Structure, Mantle Flow and Intra-Plate Volcanism
Abstract
Several of Earth's intra-plate volcanic provinces cannot be explained solely through the mantle plume hypothesis. Instead, they are believed to be generated by shallower processes that involve the interplay between uppermost mantle flow and the base of Earth's heterogeneous lithosphere. The mechanisms most commonly invoked are edge-driven convection (EDC) and shear-driven upwelling (SDU), both of which act to focus upwelling flow, and the associated decompression melting, adjacent to steps in lithospheric thickness. In this study, we undertake a systematic numerical investigation, in both 2-D and 3-D, to quantify the sensitivity of EDC, SDU and their associated melting to several key controlling parameters. Our simulations demonstrate that the spatial and temporal characteristics of EDC are sensitive to the geometry and material properties of the lithospheric step, in addition to the depth-dependence of upper mantle viscosity. These simulations also indicate that asthenospheric shear can either enhance or reduce upwelling velocities and predicted melt volumes, depending upon the magnitude and orientation of flow relative to the lithospheric step. When combined, such sensitivities explain why step changes in lithospheric thickness, which are common along cratonic edges and passive margins, only produce volcanism at isolated points in space and time. Our predicted trends of melt production suggest that, in the absence of potential interactions with mantle plumes, EDC and SDU are viable mechanisms only for Earth's shorter-lived, low-volume intra-plate volcanic provinces. To complement our study and put our results into perspective, we will also briefly discuss additional preliminary modelling of weak plumes interacting with highly heterogeneous continental structure, from which we expect different expressions of melting.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMV038.0008D
- Keywords:
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- 1033 Intra-plate processes;
- GEOCHEMISTRY;
- 8408 Volcano/climate interactions;
- VOLCANOLOGY;
- 8413 Subduction zone processes;
- VOLCANOLOGY;
- 8416 Mid-oceanic ridge processes;
- VOLCANOLOGY