A numerical study of a mantle plume beneath the Tharsis Rise: Reconciling dynamic uplift and lithospheric support models

The Tharsis Rise is an area of extensive volcanism containing the most significant long‐wavelength topographic and areoid anomalies on Mars. The mechanism for supporting this large topographic expression and correlating areoid remains controversial. The two main competing ideas are dynamic support by a deep, mantle plume and a volcanically constructed lithosphere followed by lithospheric flexure. While both of these models, separately, can account for specific features of Tharsis, neither explain its entirety. Most of the support of the Tharsis topographic anomaly is best explained by a volcanic structure modifying the lithosphere. However, this raises the important question of the origin of the heat source for volcanic construction, leading to possible small‐scale convection. This demonstrates that the remaining topography and areoid not accounted for in lower end‐members of volcanically constructed surface loads is consistent with a deeper, mantle plume source. Our results show we can produce about 15% and 18% of the total Tharsis long‐wavelength areoid and topography anomaly with a plume forming in a strong, temperature‐dependent rheology. Additionally, our plume model has a 165 km thick rheological lithosphere (within the range for present‐day estimates on Mars) and generates about 1% partial melting, more than sufficient to provide a heat source for recent volcanism. This implies both a model with dynamic support from a plume and a volcanically constructed lithosphere not only can coexist but offer an explanation for both the surface anomalies and heat needed for the minor amount of recent volcanic activity at Tharsis Rise.