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Modelling sea floor spreading initiation and rifted continental margin
formation
V Tymms (1) & iSIMM Team
(1) Department of Earth Sciences, Liverpool University, 4 Brownlow Street,
Liverpool L69 3GP, UK
[email protected]
Recent observations of depth dependent (heterogeneous) stretching where upper
crustal extension is much less than that of the lower crust and lithospheric mantle at
both non-volcanic and volcanic margins plus the discovery of broad domains of
exhumed continental mantle at non-volcanic rifted margins are not predicted by
existing quantitative models of rifted margin formation which are usually based on
intra-continental rift models subjected to very large stretching factors. New
conceptual and quantitative models of rifted margin formation are required.
Observations and continuum mechanics suggest that the dominant process
responsible for rifted continental margin formation is sea-floor spreading of the
young ocean ridge, rather than pre-breakup intra-continental rifting. Simple fluid
flow models of ocean ridge processes using analytical iso-viscous corner-flow
demonstrate that the divergent motion of the upwelling mantle beneath the ocean
ridge, when viewed in the reference frame of the young continental margin, shows
oceanward flow of the lower continental crust and lithospheric mantle of the young
rifted margin giving rise to depth dependent stretching as observed. Single-phase
fluid-models have been developed to model the initiation of sea-floor spreading and
the thermal, stretching and thinning evolution of the young rifted continental margin.
Finite element fluid-flow modelling incorporating the evolving temperature
dependent viscosity field on the fluid flow also show depth dependent stretching of
the young continental margin. Two-phase flow models of ocean ridges incorporating
the transport of both solid matrix and melt fluid (Spiegelman & Reynolds 1999)
predict the divergent motion of the asthenosphere and lithosphere matrix, and the
focusing of basaltic melt into the narrow axial zone spreading centre at ocean ridges.
We are adapting two-phase flow models for application to the initiation of sea-floor
spreading and rifted continental margin formation.
iSIMM investigators are V Tymms, NJ Kusznir, RS White, AM Roberts, PAF
Christie, N Hurst, Z Lunnon, CJ Parkin, AW Roberts, LK Smith, R Spitzer, A.
Davies and A. Surendra, with funding from NERC, DTI, Agip UK, BP, Amerada
Hess Ltd., Anadarko, Conoco, Phillips, Shell, Statoil, and WesternGeco.
V Tymms1, NJ Kusznir1, RS White2, AM Roberts3, PAF Christie4, N Hurst1, Z
Lunnon2, CJ Parkin2, AW Roberts2, LK Smith2, R Spitzer2
1
Department of Earth Sciences, Liverpool University, 4 Brownlow Street, Liverpool
L69 3GP
2
Bullard Laboratories, Cambridge University, Madingley Rd, Cambridge CB3 0EZ
3
Badleys,,North Beck House, Hundleby, Spilsby, Lincs. PE23 5NB.
4
Schlumberger Cambridge Research, High Cross, Madingley Road, Cambridge CB3
0EL