The formation and eruption of magma from the world's only carbonatite volcano, Ol Doinyo Lengai in Tanzania, continues to amaze and perplex earth scientists. The magma originates as mantle derived but the processes leading to its unique, low temperature lava remain undefined. What is the process that forms it? This project will undertake experiments and analyses of lavas from this volcano to gain fundamental insight into the general processes by which Earth's magmas change composition and ultimately erupt.
Previous workers have hypothesized that these magmas reflect an immiscibility reaction that occurs to ultimately form two magmas, one silicate and one carbonatite. These researchers will perform the new technique of Fe isotope ratio analyses along with laboratory experiments at high pressure and temperature to assess this hypothesis. Specifically, they will perform experiments to measure the Fe isotopic fractionation factor between 2 coexisting immiscible melts. Furthermore, they will perform thermal gradient experiments to assess the possible role of this process on forming the compositional evolution sequence observed in erupted rocks. The team will use new tomographic X-ray imaging techniques to assess the melt distribution in these experiments to help constrain observed electromagnetic signatures around Ol'doinyo Lengai. Use of U-series disequilibria techniques will allow us to constrain the timing and processes of magma formation with the thermal gradient experiment results used to assess a new model for disequilibria generation. The information obtained will help to understand the hazards associated with continental rift volcanism.
