Forming Intermediate to Felsic Crustal Plateaus on Venus by Remelting the Crust

Abstract

The observation of low viscosity lava flows and shield volcanoes on radar maps, combined with in-situ X-ray fluorescence analyses performed by three Soviet landers, strongly suggests that Venus’ crust is primarily basaltic [1]. Still, some of the most intriguing features of Venus, the so-called crustal plateaus, are characterized by heavily-deformed and stratigraphically old terrains, and associated with a thickened crust that can reach over 50 km [2]. Moreover, Infra-red emissivity spectra from the Galileo and Venus Express missions tend to support the presence of a larger fraction of felsic minerals in the plateaus compared to the surrounding basaltic plains [e.g.,3]. These unique characteristics have led to the interpretation that crustal plateaus may represent analogues to continents on Earth. On Earth, flux melting of the mantle wedge at subduction zones, followed by fractional crystallization or partial melting of hydrous basalts, are believed to be the two primary mechanisms generating the large volumes of intermediate to felsic rocks that make up the continental crust. By contrast, igneous differentiation of water-poor basaltic melts typically yields negligible amounts of felsic melts. To better understand the nature of the plateaus, the upcoming EnVision and VERITAS missions will provide new measurements of surface emissivity for the entire surface of Venus, allowing to determine if the highland plateaus are dominated by intermediate to felsic rocks in the hope of providing evidence for the presence of water oceans and, therefore, habitable conditions in Venus’ distant past. In this work we investigate possible scenarios of generating large amounts of intermediate to felsic melt compositions on Venus. In particular, we evaluate the melts generated by remelting crustal materials at depth and the impact of water on these compositions.