Cratons on Venus in global thermochemical convection models
Abstract
Numerical convection simulations indicate that episodic lithospheric overturn model is favoured over a stagnant lid model in matching Venus' surface observations regarding resurfacing, topography and geoid (Armann & Tackley, 2012). More recent work by Rolf et al. (2018) suggests a lower frequency of overturns, with the last global event of tectonic recycling ceased a rather long time ago, possibly since the last 1Gy. On the other hand, while continent-like composition is observed on Venus' tessera terrains (Hashimoto et al., 2008, Helbert et al.,2008), mantle convection models show that a rheologically strong continent introduces lithospheric heterogeneity and increases convective stresses at continental margins, thus affecting the global convective regime (Rolf & Tackley, 2011). However, their study focusses on the plate tectonics on earth, featuring a mobile lid convection regime, instead of an episodic regime. Moreover, Romeo & Turcotte (2008) proposed an analytical model on the evolution of continent on Venus, but they mainly aim to explain the structural patterns observed on tesserae, rather than exploring the role of craton in whole mantle convection pattern.
In order to narrow this gap, several sets of numerical simulations are performed using the convection code StagYY (Tackley, 2008), with a 2D spherical annulus geometry. First, we vary the yield stress to observe different convection regimes under Venus conditions. Then we impose a craton at the beginning of an identical set of cases to compare the resultant outcomes. In addition, we run separate lists of cases to examine the effect of craton parameters and the style of volcanism (i.e. eruption and intrusion) on both the convection regime and the survival of craton. The following questions are investigated: (1) How well are cratons preserved during an overturn event on a Venusian setting? (2) Is the condition for an overturn to occur affected by the presence of a craton? Finally, we present results including topography, gravity, crustal and lithospheric thickness to give insight into scenarios on Venus.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMDI32A..06C
- Keywords:
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- 5430 Interiors;
- PLANETARY SCIENCES: SOLID SURFACE PLANETSDE: 8103 Continental cratons;
- TECTONOPHYSICSDE: 8149 Planetary tectonics;
- TECTONOPHYSICSDE: 8170 Subduction zone processes;
- TECTONOPHYSICS