Physics
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufm.p51a1414s&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #P51A-1414
Physics
[5475] Planetary Sciences: Solid Surface Planets / Tectonics, [8120] Tectonophysics / Dynamics Of Lithosphere And Mantle: General, [8121] Tectonophysics / Dynamics: Convection Currents, And Mantle Plumes
Scientific paper
The hemispheric crustal dichotomy and the Tharsis volcanic province are major global physiographic features on Mars, whose origin has not yet been satisfactorily explained. Hypotheses for the dichotomy origin invoke both external causes (i.e., a giant impact) and mechanisms of internal dynamics (e.g., long-wavelength mantle convection, or a large-scale overturn of unstable post-magma ocean cumulates). Recently, Zhong (2009) proposed a link between the preexisting dichotomy, and the formation and early evolution of Tharsis. He considered lithospheric thickness with a strong hemispheric asymmetry, where thicker lithosphere below the thicker crust in the southern highlands represents devolatilized residue after more extensive partial melting assumed to be responsible for the dichotomy formation. The thermal upwellings of long-wavelength convection then first form below the thickest lithosphere. Subsequently, the strong lateral viscosity variations result in a relative motion between the one-plate lithosphere and the upwelling, such that the upwelling migrates toward regions of smaller lithospheric thickness. This model is capable of explaining the apparent early migration of the Tharsis volcanic centers and their stabilization near the dichotomy boundary (Sramek & Zhong, 2010). However, our previous models did not consider melting, which prevented us from addressing the question of how the large lithospheric thickness variation is produced. Recent modeling results of Keller & Tackley (2009) suggest that dichotomy may have been formed by partial melting of the mantle showing a spherical harmonic degree 1 convection pattern. However, they did not consider devolatilization effects of partial melting and the modulation of the flow by the stiff melt residue. We present a series of numerical experiments of long-wavelength convection in Martial mantle, where we consider the effect of partial melt residue stiffening on the plume-lithosphere dynamics, in order to asses the plausibility of a self-consistent endogenic model of dichotomy formation by partial melting and Tharsis evolution.
Šrámek Ondřej
Zhong Sijia
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