Lithospheric instability and the source of the Cameroon Volcanic Line: Evidence from Rayleigh wave phase velocity tomography
Journal Article
·
· Journal of Geophysical Research. Solid Earth
- Washington Univ., St. Louis, MO (United States). Dept. of Earth and Planetary Sciences
- Pennsylvania State Univ., University Park, PA (United States). Dept. of Geosciences
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
- Global Geophysical Services, Inc., Denver, CO (United States)
The Cameroon Volcanic Line (CVL) is a 1800 km long volcanic chain, extending SW-NE from the Gulf of Guinea into Central Africa, that lacks the typical age progression exhibited by hot spot-related volcanic tracks. Our study investigates the upper mantle seismic structure beneath the CVL and surrounding regions to constrain the origin of volcanic lines that are poorly described by the classic plume model. Rayleigh wave phase velocities are measured at periods from 20 to 182 s following the two-plane wave methodology, using data from the Cameroon Seismic Experiment, which consists of 32 broadband stations deployed between 2005 and 2007. These phase velocities are then inverted to build a model of shear wave velocity structure in the upper mantle beneath the CVL. Our results show that phase velocities beneath the CVL are reduced at all periods, with average velocities beneath the CVL deviating more than –2% from the regional average and +4% beneath the Congo Craton. This distinction is observed for all periods but is less pronounced for the longest periods measured. Inversion for shear wave velocity structure indicates a tabular low velocity anomaly directly beneath the CVL at depths of 50 to at least 200 km and a sharp vertical boundary with faster velocities beneath the Congo Craton. Finally, these observations demonstrate widespread infiltration or erosion of the continental lithosphere beneath the CVL, most likely caused by mantle upwelling associated with edge-flow convection driven by the Congo Craton or by lithospheric instabilities that develop due to the nearby edge of the African continent.
- Research Organization:
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE
- Grant/Contract Number:
- AC52-06NA25396
- OSTI ID:
- 1329571
- Report Number(s):
- LA-UR-15-21130
- Journal Information:
- Journal of Geophysical Research. Solid Earth, Journal Name: Journal of Geophysical Research. Solid Earth Journal Issue: 3 Vol. 120; ISSN 2169-9313
- Publisher:
- American Geophysical UnionCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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