Kinematic analysis of radial structures around Irnini Mons, Venus

Abstract

Radial structures to the north-east of Irnini Mons are discernable as ridges at the full Magellan image resolution of 75 m/pixel using FMAP tiles. While a magma source modeled as a pressurized hole in an elastic plate usually allows for only extensional radial structures, the perturbation of regional stresses around the hole can explain the presence of radial ridges. Sixteen numerical models were run to see what effect changes in magma pressure and regional stresses had on the magnitude of the maximum principal stresses and the orientation of potential features around a hole in a plate. These models were arranged into four groups based on model input and setup: 1) uniaxial compressive stress; 2) uniaxial tensile stress; 3) biaxial stress; and 4) multiple holes. Nine of the sixteen models result in radial ridges in the orientation observed around Irnini Mons; all of these models incorporate a regional N-S compression. Flows from Irnini Mons are superimposed on an older, regional plains material deformed by a regional set of east-west trending wrinkle ridges, implying a regional north-south compression affected the area. The existence of radial ridges on the Irnini flows implies that the regional N-S compression that caused the E-W trending wrinkle ridges was still active during the formation of Irnini Mons. However, the magnitude of the regional compressive stress required for radial ridge formation could be 1–5 MPa less than the compressive strength of the material, indicating that radial ridges could form after wrinkle ridge formation has ceased.