Small scale convection at the edge of the Colorado Plateau: Implications for topography, magmatism, and evolution of Proterozoic lithosphere
Abstract
The Colorado Plateau in the southwestern U.S. is characterized by a bowl-shaped high elevation, a large gradient in seismic wave velocity across its margins, and relatively low lithospheric seismic wave velocities in comparison to the lithosphere of the Great Plains. Late Neogene-Quaternary magmatism is found on the margins of the Plateau, which has migrated inward with a rate of several mm/yr. We explain these observations by edge-driven convection around the edges of the Plateau following rehydration of Colorado Plateau lithosphere. A step in lithosphere thickness was formed between the Colorado Plateau and its adjacent extended Rio Grande rift and Basin and Range Provinces during Cenozoic extension. Our numerical models show that a small scale convection cell developed around this step. Below the Plateau margin a lithospheric drip formed that removed lithosphere material from the edge that heated and metasomatized, resulting in magmatism. Edge-driven convection also drives margin uplift, giving the plateau its characteristic bowl shape, while uplift resulting from lithosphere dissociation contributes to the overall high elevation in addition to thermal uplift. The edge-driven convection model is in good agreement with features resolved by seismic tomography.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.T13B1862V
- Keywords:
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- 7270 SEISMOLOGY / Tomography;
- 8100 TECTONOPHYSICS;
- 8120 TECTONOPHYSICS / Dynamics of lithosphere and mantle: general;
- 8400 VOLCANOLOGY