Publication: The heat flow during the formation of ribbon terrains on Venus
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2007
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Elsevier Science B.V.
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Abstract
Ribbons are regularly spaced, between 2 and 6 km, troughs that exist on venusian tesserae, which are mainly located in, and
characterize to, venusian crustal plateaus. Independent of the geological or temporal relations with other features, regularly and similarly
spaced ribbons on several tesserae strongly suggest a thermal control on the thickness of the deformed layer. This can be used to
constraint the heat flow at the time of ribbon formation, which holds important implications for the viability of the hypotheses that
address the origin and evolution of crustal plateaus. For a brittle–ductile transition 1–3km deep (as proposed from ribbon spacing),
realistic strain rates, and a present-day surface temperature of 740 K, the implied heat flow is very high, 130–780mWm2. If Venus has
experienced higher surface temperatures due to climate forcing by massive volcanism, then the heat flow could be greatly reduced. For
surface temperatures of 850–900K the heat flow is 190–560, 60–230 and 20–130mWm2 for brittle–ductile transition depths of 1, 2 and
3 km, respectively. Heat flow values around 80–100mWm2 are reasonable for venusian hotspots, based on terrestrial analogs, but
hardly consistent with coldspot settings. High surface temperatures are also required to maintain the crustal solidus deeper than a few
kilometers during the formation of ribbon terrains. For the obtained heat flows, a solidus deeper than 30km (the likely mean value for
the crustal thickness) is difficult to achieve. This suggests that a substantial proportion of the crust beneath crustal plateaus was emplaced
subsequently to the time when ribbon terrains were formed. Alternatively, at that time a magma reservoir inside the crust could have
existed.