Regionalized Formation and Recycling of New Venusian Crust at Chasmata

Abstract Venus and Earth are geologically active in ways distinct from each other. Earth exhibits plate tectonics, where the primary resurfacing mechanism is crust formation along a globe-girdling, extensional tectonic setting in mafic crust, the mid-ocean ridge (MOR). While Venus does not exhibit the key characteristics of plate tectonics, it also possesses a globe-girdling, extensional tectonic setting in mafic crust referred to here as the global rift network (GRN). Despite the macroscale similarities, the two rift systems feature disparate characteristics. Using numerical modeling compared against topographic models from Magellan, we test whether seafloor-spreading-like tectonics under Venusian conditions can reproduce the morphology of individual chasmata along the GRN. The results indicate that the MOR-like seafloor spreading does not occur along most of the GRN, only in unique tectonic environments like that within Artemis Corona. On the other hand, we find that rift-embedded coronae along the GRN have morphologies best explained by excess crustal formation and subsequent densification leading to lithospheric delamination like ephemeral subduction postulated for coronae in previous studies. This suggests that secondary hot spots form between the major plumes under Beta, Atla, Themis, and Phoebe Regios. These minor plumes follow the flow of the upwelling mantle to initiate the formation of rift-embedded coronae along the GRN before becoming inactive when the hot spot dies. Such regionalized formation and recycling of the crust under the influence of mantle plumes is consistent with active geodynamics with limited plate mobility, such as predicted by plutonic-squishy lid, deformable lid, and globally fragmented lid tectonic hypotheses.