Regios as a manifestation of upper-mantle dynamics

Venus’ regios are large surface structures characterized by both elevated topography and geoid, as well as presence of extensive lava flows that overlie the surrounding terrains. These regios are the youngest surface features observed on Venus, and are interpreted as the manifestations of mantle plumes and related melting. Our goal is to infer the subsurface structure of Venus that is consistent with the observation of these structures. Using the finite-element open-source code ASPECT, we set up a 3D thermochemical incompressible model with melting to calculate the convection in the upper mantle and related lithospheric evolution. The assumed material rheology includes thermal and melt-induced chemical buoyancy, as well as diffusion creep with water-dependent stiffening. We perform a parametric study independently varying rheological properties, plume size, and plume temperature. For each set of parameters, we analyze the melting distribution, surface topography, and the generated geoid, and compare these predictions with available observations of Venus’ regios. Our results demonstrate that the plume models are mostly consistent with the geophysical signature of Venus’ regios. Additionally, we provide constraints on the upper-mantle structure beneath the regios, and show the diversity of the melting patterns that may explain various systems of tectonic features observed on Venus.