Deep Controls on the Geometry of Volcanic Hotspot Tracks
Abstract
Large igneous provinces (LIPs) erupting since 200 Ma may have originated from plumes that emerged from the edges of the large low shear velocity provinces (LLSVPs) in the deep lower mantle. We present global convection models constrained by plume motions and subduction history over the last 230 Myr, where plumes emerge preferentially from the edges of thermochemical structures that resemble present-day LLSVPs beneath Africa and the Pacific Ocean. We show that plume eruption locations in models with a chemically anomalous lower mantle are highly correlated to reconstructed LIP eruption sites. A network of embayments separated by steep ridges forms in the deep lower mantle in these models. Plumes originate at and become anchored to the peaks of the chemical ridges. The network of ridges adjusts their position in response to subduction-induced deep mantle flow through time. Our results suggest that LLSVP regions can be mobile, in contrast to being stable over hundreds of millions of years, as has been suggested based on the correlation of the present-day edges of the African LLSVP with reconstructed volcanic features. We show that fast moving oceanic plates bounded by a set of dynamic subduction zones can lead to a sustained and coherent flow in the deep lower mantle. LLSVP regions in the vicinity of such coherent lower mantle flows can undergo rapid deformation. Consequently, lateral motion of mantle plumes anchored to rapidly deforming LLSVP regions can result in sharp geometric features in their surface hotspot tracks. This illustrates why the Pacific LLSVP may have been more mobile than its African counterpart. Asymmetric deformation of the Pacific LLSVP over the last 140 Myr may explain the morphological diversity of surface hotspot tracks associated with deep mantle plumes in the Pacific.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMDI51C..02H
- Keywords:
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- 5430 Interiors;
- PLANETARY SCIENCES: SOLID SURFACE PLANETSDE: 8121 Dynamics: convection currents;
- and mantle plumes;
- TECTONOPHYSICSDE: 8124 Earth's interior: composition and state;
- TECTONOPHYSICSDE: 8147 Planetary interiors;
- TECTONOPHYSICS