Dyke swarm history of Eastern Eistla Regio, Venus and implications for its plume origin

Eistla Regio on Venus comprises three east–west–aligned regional topographic highs interpreted as products of mantle plume activity. This study reconstructs the geological evolution of Eastern Eistla Regio using 1:500,000-scale geological mapping based on NASA Magellan SAR imagery, with emphasis on four principal coronae: Isong, Ninmah, Pavlova, and Didilia. A fifth corona, Calakomana, predates and is unrelated to Eastern Eistla. We document extensive graben–fissure–fracture systems interpreted as surface expressions of mafic dyke swarms. Radiating and circumferential swarms are closely associated with the four coronae and their underlying plumes or diapirs. Twenty radial systems are identified, including eight with radii >400 km and four >1000 km. Ninmah, Pavlova, and Didilia each host multiple radiating centers, whereas Isong exhibits a single center. Circumferential swarms occur at Ninmah and Isong. Seven linear dyke swarms are also recognized of which at least three likely originated from magmatic centers outside the study area. Relative chronology based on cross-cutting relationships and dyke trend changes indicates overlapping magmatic activity among the coronae, with principal radiating swarm development progressing from Isong to Ninmah, Pavlova, and Didilia. Pavlova also records late-stage activity. Deviations in dyke swarm radiality constrain plume head dimensions, indicating that the four plume heads occupy a ~ 1300 km-radius region interpreted as the Eastern Eistla mantle plume, partly bounded by Metelitsa Dorsa. Swings in dyke swarm trends into an orientation orthogonal to the Eastern Eistla plume boundary suggest lateral stresses from the plume-induced uplift. Bouguer gravity and crustal thickness anomalies reveal two roughly parallel lithospheric weakness zones, separated by ~800 km, that focused plume-related uplift and magmatism.