Modelling plume-related uplift, gravity and melting on Venus
F. Nimmo and D. McKenzie, Earth Planet. Sci. Lett. 145, 109-123, 1996
Three roughly circular regions on Venus about 1000 km across
are identified as potential Hawaii-scale plume sites on the
basis of their gravity (70-90 mgal) and topography (1.6-2.0 km)
anomalies, and signs of melt generation and rifting.
Axisymmetric isoviscous convection models are used to reproduce
gravity profiles across these plumes and the line-of-sight
acceleration of the Magellan spacecraft as it passes over them.
The best fitting models have a conductive lid thickness of less
than 150 km, mantle viscosity of 8.9 x 10(19) to 9.6 x 10(20)
Pa s and a basal heat flux of 15-25 m W m(-2). The lid
thickness is constrained by requiring a modest amount of melt
generation and a potential temperature of about 1300 degrees C.
The high mantle viscosity relative to that of Earth is probably
a consequence of the absence of water in the mantle, and may
help to explain the current absence of plate tectonics on
Venus. The low heat flux suggests that the thermal evolution of
Venus has differed from that of the Earth.
Francis' Page
Department of Earth Sciences
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nimmo@esc.cam.ac.uk
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