Magmatic diversity on Venus: Constraints from terrestrial analog crystallization experiments

Igneous diversity is common on terrestrial planets and has been experimentally investigated for the Earth and Mars, but only suggested for Venus. Since Venus and Earth are sister planets and have similar bulk chemistry, experiments on terrestrial basalts can place constraints on the formation of the Venera and Vega basalts. Furthermore, experimental results can suggest the types of magmas that should be present on Venus if processes of differentiation similar to those taking place within the Earth are occurring on Venus, as suggested by the Venera and Vega analyses. The interpretation of the Venera 13 analysis as an alkali basalt suggests deep partial melting of a carbonated source region; while the identification of Venera 14 and Vega 2 as tholeiites suggest relatively shallow melting of a hydrous lherzolitic or peridotite source region. The residual liquids produced by differentiation of a Venus tholeiite, based on experiments on analog compositions, range from rhyolites to phonolites, depending on pressure of crystallization and bulk water content. Results from these crystallization experiments on tholeiitic terrestrial compositions can constrain the type and quality of data needed from future missions to determine the petrologic history of surface igneous rocks.