Smith Lecture: Earth's Upper Mantle Hybridization by Chemical Heterogeneity: Implications for Genesis of Ocean Island Basalts and Ultra-potassic Arc Lavas
Chemical heterogeneities are introduced in the Earth’s mantle via subduction and are also created within the mantle by differentiation (melting) processes. Such heterogeneities chemically interact with the surrounding (peridotitic) mantle either by solid-state diffusion processes or via melting/releasing fluids. Therefore, chemical processes within the Earth’s mantle must be affected by presence of these heterogeneities and as proof, several primary lava compositions across tectonic settings contain signatures of presence of some form of chemical heterogeneity in the source. Owing to their reactivity in silicate systems, volatiles such as H2O and CO2 interfere with mantle chemical processes, adding further complexity to heterogeneity-ambient mantle interaction. I have used ocean island basalts and arc lavas as proxies to understand how chemical heterogeneities interact with the ambient mantle both in the presence and absence of volatiles.