Volcanic rifts and volcanic passive margins : 3D geometry and gruyere-type rheology
Abstract
A large review of converging geological, geophysical and modelling data suggest that the continental break-up over plumes is similar to the high-rate extension of a rheological "gruyère-type" lithosphere. The 3D geometry of volcanic rifts and volcanic passive margins seems indeed to reflect a fundamentally inhomogeneous process of plate break-up. Plate splitting initiate and propagate from apart numerous lithospheric soft-points (the gruyère's voids). It looks like that these low- or no-strength soft-points are topologically and genetically linked to melting zone areas in the mantle. I proposed that these soft-points represent small-scale Rayleigh-Taylor instabilities developed from the low-density plume asthenosphere. With time, this former hypothesis seems to gain more and more favourable arguments and should probably not been ruled out. It conflicts with previous models of lithosphere break-up but presents some analogy with the Courtillot's rift initiation and propagation model. It could provide some keys to active research fields such as the possible rule of inherited lithospheric-scale discontinuities in localizing extension. I discuss the important theoretical points which remain to be solved to fully adopt this model.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA....11543G