Floor-fractured impact craters on Venus: Implications for igneous crater modification and local magmatism

Regional tectonism and volcanism affect crater modification and crater loss on Venus, but a comparison of Venusian craters to lunar floor-fractured craters uggests that a third style of more localized, crater-controlled magmatism also may occur on Venus. Based on lunar models for such magmatism, Venusian crustal conditions hould generally favor crater-filling volcanism over crater-centered floor fracturing. Nevertheless, three craters on Venus strongly resemble xtensively modified craters on the Moon where deformation can be attributed to failure over large crater-centered intrusions. Models for crater modification over igneous intrusions indicate typical magmatic pressures beneath these three craters of--200-300 bars and intrusion depths of the order of 1-6 km. All three craters also share common settings and low elevations, whereas craters embayed by regional volcanism preferentially occur at much higher elevations on Venus. We suggest that the style of igneous crater modification on Venus thus may be elevation dependent, with crater-centered intrusions primarily occurring at low elevations on Venus. This interpretation is consistent with theoretically predicted variations in magmatic neutral buoyancy depth as a function of atmospheric pressure suggested by other authors.