Possible giant metamorphic core complex at the center of Artemis Corona, Venus

Hundreds of circular features on Venus known as coronae are characterized b y annular fractures and commonly associated radial fractures and lava flows . Coronae are thought to have been produced by buoyant mantle diapirs that flatten and spread at the base of the lithosphere and cause fracturing, upl ift, and magmatism, The interior of Artemis Corona, by far the largest coro na at 2100 km diameter, is divided in half by a northeast-trending deformat ion belt that contains numerous rounded ridges resembling antiforms, The la rgest of these ridges, located at the center of Artemis Corona, is similar to5 km high on its steep northwest Rank where it is adjacent to a flat-bott omed, 10-km-wide trough interpreted as a rift valley, The 280-km-long antif ormal ridge is marked by perpendicular grooves that cross the similar to 50 -km-wide ridge and extend southeastward as far as 120 km across adjacent pl ains. The grooves abruptly terminate northwestward at the rift trough. The large antiformal ridge terminates southwestward at a transform shear zone t hat parallels the grooves. These features-rift valley, antiformal uplift, g rooves, and transform shear zone-are morphologically and geometrically simi lar to grooved, elevated, submarine metamorphic core complexes on the insid e corners of ridge-transform intersections of slow-spreading ridges on Eart h. As with submarine core complexes, the grooved surface on Venus is interp reted as the footwall of a large-displacement normal fault, and the grooves are inferred to be the product of plastic molding of the footwall to irreg ularities on the underside of the hanging wall followed by tectonic exhumat ion of the molded grooves and conveyer-belt-like transport up and over the large antiform and across the southeastern plains. According to this interp retation, the trend of the grooves records the direction of extension, whic h is perpendicular to the thrusts at the leading edge of the annular thrust belt 1000 km to the southeast, Both may have formed at the same time as a result of uniform southeastward displacement of the southeastern half of th e interior of Artemis Corona, The location of this grooved core complex at the center of Artemis Corona may reflect genesis above the buoyant, ascendi ng tail of the corona-producing mantle diapir.