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- Title
Lithospheric structure of the Rio Grande rift.
- Authors
Wilson, David; Aster, Richard; West, Michael; Ni, James; Grand, Steve; Gao, Wei; Baldridge, W. Scott; Semken, Steve; Patel, Paresh
- Abstract
A high-resolution, regional passive seismic experiment in the Rio Grande rift region of the southwestern United States has produced new images of upper-mantle velocity structure and crust-mantle topography. Synthesizing these results with geochemical and other geophysical evidence reveals highly symmetric lower-crustal and upper-mantle lithosphere extensional deformation, suggesting a pure-shear rifting mechanism for the Rio Grande rift. Extension in the lower crust is distributed over a region four times the width of the rift's surface expression. Here we propose that the laterally distributed, pure shear extension is a combined effect of low strain rate and a regionally elevated geotherm, possibly abetted by pre-existing lithospheric structures, at the time of rift initiation. Distributed extension in the lower crust and mantle has induced less concentrated vertical mantle upwelling and less vigorous small-scale convection than would have arisen from more localized deformation. This lack of highly focused mantle upwelling may explain a deficit of rift-related volcanics in the Rio Grande rift compared to other major rift systems such as the Kenya rift.
- Subjects
UNITED States; RIFTS (Geology); STRAINS &; stresses (Mechanics); CONVECTION (Meteorology); GEOLOGY; RIO Grande Rift
- Publication
Nature, 2005, Vol 433, Issue 7028, p851
- ISSN
0028-0836
- Publication type
Article
- DOI
10.1038/nature03297