FEM modelling of concentric and radial structures on Ascraeus Mons

Ascraeus Mons is the northernmost of the three large shield volcanoes on the Tharsis Rise on Mars. In this work we test the hypothesis that the latest volcanotectonic evolution of the Ascraeus Mons could have been driven by an oblate magma chamber inducing injection of sheeted and radial dikes with distribution that recall the ones of the Cuillins cone sheet complex on the isle of Skye (Scotland). Indeed in this latter case Finite Element Modelling (FEM) has demonstrated that the distribution of dykes predict an oblate shallow magma chamber. On the basis of an accurate mapping of the Ascraeus Mons structures on high resolution stereo camera (HRSC) image mosaic, we were able to recognize concentric and radial structures, and to assess their interactions and attitudes. These remote sensing observations, combined with other physical parameters such as crustal thickness, critical distance of transition between concentric and radial fracture systems, gravitational load of the volcanic body, allow to infer, trough a FEM analysis, the possible presence of an oblate magma chamber at the time of the youngest volcano-tectonic event, its dimensions, depth and the tensional state of the system within particular overpressure/inflation conditions within the magma chamber itself. In addition the age of the deformational event that formed the fracture patterns was calculated through crater counting.