FALCON has been used to study how rifting structures observed on Venus could have been formed. In particular, the evolution of rifting has been investigated under the Venusian surface conditions (very high temperature and high pressure) and the proposed lithospheric structure. Model results show that a strong crustal rheology such as diabase is needed to localize strain and to develop a rift under the high surface temperature and pressure of Venus. The evolution of the rift formation is predominantly controlled by the crustal thickness, with a 25 km-thick diabase crust required to produce mantle upwelling and melting. The surface topography predicted by the models fits well with the topography profiles of the Ganis and Devana Chasmata for different crustal thicknesses, indicating that the difference in these rift features on Venus could be due to different crustal thicknesses. Based on the estimated heat flux of Venus, the models indicate that a crust with a global average lower than 35 km is the most likely crustal thickness on Venus.
Microcontinents
Microcontinents are fragments of continents partially or entirely surrounded by an ocean that, due to the relative motion of tectonic plates, can either be accreted to or subducted below the continental plate. FALCON has been used to investigate the conditions favoring subduction or accretion and how the presence of microcontinents can impact the termal state in the subduction system. Model results reveal that the presence of a microcontinent can lead to different styles of subduction: 1) uninterrupted subduction; 2) relocation of the subduction from the front to the back of the microcontinent without interruption; 3) interruption and restart of the subduction; and 4) no subduction. Models predicted that higher convergence velocities and a greater initial distance between the microcontinent and the continent favor uninterrupted subduction (style 1), while larger microcontinents and higher velocities of the ocean favor the relocation or momentary interruption of the subduction (styles 2-4). In addition, introduction of microcontinents induce noticeable changes of termal state within the subduction system.
FALCON has been used to study how rifting structures observed on Venus could have been formed. In particular, the evolution of rifting has been investigated under the Venusian surface conditions (very high temperature and high pressure) and the proposed lithospheric structure. Model results show that a strong crustal rheology such as diabase is needed to localize strain and to develop a rift under the high surface temperature and pressure of Venus. The evolution of the rift formation is predominantly controlled by the crustal thickness, with a 25 km-thick diabase crust required to produce mantle upwelling and melting. The surface topography predicted by the models fits well with the topography profiles of the Ganis and Devana Chasmata for different crustal thicknesses, indicating that the difference in these rift features on Venus could be due to different crustal thicknesses. Based on the estimated heat flux of Venus, the models indicate that a crust with a global average lower than 35 km is the most likely crustal thickness on Venus.
Microcontinents are fragments of continents partially or entirely surrounded by an ocean that, due to the relative motion of tectonic plates, can either be accreted to or subducted below the continental plate. FALCON has been used to investigate the conditions favoring subduction or accretion and how the presence of microcontinents can impact the termal state in the subduction system. Model results reveal that the presence of a microcontinent can lead to different styles of subduction: 1) uninterrupted subduction; 2) relocation of the subduction from the front to the back of the microcontinent without interruption; 3) interruption and restart of the subduction; and 4) no subduction. Models predicted that higher convergence velocities and a greater initial distance between the microcontinent and the continent favor uninterrupted subduction (style 1), while larger microcontinents and higher velocities of the ocean favor the relocation or momentary interruption of the subduction (styles 2-4). In addition, introduction of microcontinents induce noticeable changes of termal state within the subduction system.