| Project Detail |
Deeply rooted mantle melts forming in adiabatic upwellings are key to Earth’ differentiation, but the very first step of melt generation remains largely obscure. The reason for this knowledge gap lies in the complexity of the problem: Redox processes involving volatiles (C, H, S), phosphorus and Fe-Ni-metal combine with compositional heterogeneities and variable mantle fertility into a panoply of possible melt contributions that is hard to disentangle. This project is to experimentally simulate the incipient melting process, with an emphasis on the role of carbon. A cornerstone of deep melting is the oxidation of C(0) (in the form of diamonds, carbides or in metal alloys) to CO2 at depths of 180-270 km (6-9 GPa). The consequent sudden appearance of CO2 lowers melting temperatures by 300-500 deg C, i.e. from above to below adiabatic mantle temperatures. I postulate that the resulting redox melts are highly Si-undersaturated kimberlitic silicate melts in all types of upwellings, which then develop into the various surface melts in function of the truncation depth of the melting column, as resulting from the overlying lithosphere.Several novel strategies will be used to experimentally investigate this process. The results should enable the development of a universal framework for deep mantle melts forming at near-adiabatic conditions (~ 1440 deg C, 6-9 GPa). Project A investigates the redox transformation of deep mantle metal melts including C, S and P into silicate melts at source conditions, in order to understand the process leading to the CO2-propelled deep magmas. Project B takes a new approach on the origin of the resulting alkaline magmas by following them from the surface to their roots (and not as conventional vice versa), hence constraining the asthenospheric melting column from the opposite direction. Project C experimentally investigates true carbonatite melt compositions and isotope and element fractionation between alkaline magmas, carbonatites and their fluids. The goal is to isolate the information such magmas contain on deep mantle processes by disentangling magmatic from (the often dominant) secondary fluid-mediated signatures.The fundaments for these projects are high-pressure high-temperature experiments (0-12 GPa, 800-1800 deg C), in static multi anvil and piston cylinder apparatus and in the unique centrifuging piston cylinder to be used to max. 1000-fold Earth acceleration. This four-year project asks for four years of salary for one post-doc and two PhDs as well as the required supplies for laboratory experiments and related analytical costs. |
