Physics
Scientific paper
Aug 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993pepi...79..241s&link_type=abstract
Physics of the Earth and Planetary Interiors, Volume 79, Issue 1-2, p. 241-267.
Physics
13
Scientific paper
The evolution of the lithosphere is mainly controlled by time-dependent forces due to (1) plate tectonic processes and (2) sublithospheric mantle flow. Plate tectonic processes like continental collision may provide strong thermal disturbances and, after completion, may trigger secondary convection beneath the lithosphere. Without such mantle flows lateral variations of temperature (and associated variations of lithospheric thickness hL or seismic velocities) will equilibrate after time scales which are considerably shorter than the geologic ages of several provinces in Europe.
We will discuss the role of sublithospheric mantle flows on the evolution of the lithosphere and the asthenosphere and compare the results with observations from the European lithosphere. Steady-state convection models with a rheology based on laboratory data on lherzolite show, that there exists a simple relationship between mantle heat flow and hL. However, steady state may be reached only after transition times of the order of 1 Ga. During such times, hL shows strong lateral variations. If such variations were inherited from plate tectonic events, the role of sublithospheric convection would be to prolong their lifetime considerably. At higher heat flows, sublithospheric mantle convection becomes strongly time-dependent with a time scale of 25-50 Ma. On this time scale, variations of hL are small. Altogether, we observe no strong direct correlation between upwelling mantle flows and thin lithosphere. In some cases the correlation is even reversed. On the other hand, the presence or absence of a partially molten asthenosphere may be strongly affected by sublithospheric convection, and may show strong lateral variations as well. These variations in space and time can be correlated with the laterally heterogeneous LVZ, with seismic tomography data and with intraplate volcanism in Europe.
Mantle convection, mantle diapirs, and variations in thickness of the lithosphere may exert forces on the lithosphere and crust. They will lead to bending of the lithosphere, changes in surface topography and thinning or thickening of the crust, induced by lateral flows within the lower crust. Depending on the time scale of loading and unloading of the lithosphere and the relaxation time associated with lower crustal flows characteristic relations between Moho depth and surface topography are predicted. Comparison with observed correlations between Moho depth, surface topography and lithospheric thickness of European crustal age provinces show some trends in agreement with the proposed crustal deformation model.
Marquart Gabriele
Schmeling Harro
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