CORONA ELONGATION IN RELATION TO RIFT ZONES ON VENUS

Coronae and chasmata, two of the most common tectonic features observed on the surface of Venus, are often found in close proximity to each other. The first is likely the surface manifestation of a mantle plume and subsequent lithosphere delamination, while the second forms when the lithosphere stretches. As observed on Earth, there may be a geodynamical link between the two: plumes can help initiate lithosphere extension, as in the case of the East African rift, and well-developed rift zones can attract plumes, as in the case of Iceland. To better understand the link between coronae et chasmata, we compare the elongation direction of coronae with chasma orientation, with an initial focus on the V-53 quadrant. This quadrant covers the prominent Parga Chasmata and features 22 named coronae. We collected elongation and orientation data for a global dataset of more than 500 coronae using new techniques implemented in ArcGIS. In the V-53 quadrangle, the coronae are elongated with a mean ratio between their semi-minor and semi-major axes of 0.72. Coronae along Parga Chasmata are systematically more elongated. The long axis of the coronae strikes N96°E on average, close to the orientation of the chasmata (~ N109°E). The low circular variance of corona orientation, 0.3, indicates a somewhat tight distribution of orientation. The coincidence between corona and chasmata orientation implies that the coronae are not passively stretched by the rifts but are influenced by it. At least two mechanisms can explain this relation: a rising plume may become elongated as it follows relief at the base of the lithosphere, or the stress field may guide magmatic intrusions in the direction of the rift zone. We will examine other regions of Venus to determine if the relationships observed in the V-53 quadrant are generally valid.