Dynamics of Venusian rifts and their interactions with plumes and intrusions

The surface of Venus features extensive rift zones, known as chasmata, up to10,000 km in length. Many of Venus’ rifts exhibit intersecting branches, multi-ple troughs, and associations with coronae, which are often interpreted as small-scale upwellings. In the absence of Earth-like plate tectonics, the driving forcesand rates of extension and lithospheric structure are poorly constrained. Here,we present the first 3D numerical models of rift tectonics under Venus-like con-ditions. We investigate the impact of crustal rheology (wet vs. dry diabase)and the thickness of the crust and lithosphere on rift geometry, topography, andsurface fracturing. We further explore interactions between evolving rift struc-tures and thermal upwellings (plumes) and magmatic intrusions – key compo-nents of Venus’ global geodynamics. We find that rift morphology is highlysensitive to crustal rheology and lithospheric properties, with five modes of riftmorphologies predicted: (1) narrow, (2) wide-valley, (3) wide-troughs, (4) mul-tiple, and (5) branching; the latter three align most closely with Venus obser-vations. Underplated thermal plumes induce lower-crustal intrusions and causelocalized lithospheric weakening, narrowing the rift regionally. Many coronaelocated within chasmata display arcuate trenches, and may require alternativemechanisms or conditions to explain their rift morphology. Lateral offsets ofrift valleys, branching from a single rift into multiple, and multiple parallel riftvalleys are promoted by a relatively weak crust (wet diabase) or a strong crust(dry diabase) combined with a thin, warm lithosphere. If Venus’ crust followsa dry diabase rheology, a significantly warm and thin lithosphere is required toreproduce observed rift characteristics. Some first-order differences in rift mor-phology across Venus may result from spatial or temporal variations in crustal and lithospheric properties.