Li isotope fractionation in magmatic systems: Constraints from in-situ delta7Li determinations on magmatic minerals by femtosecond-laser ablation-MC-ICP-MS

Beteiligte Institutionen der FZ:GEO:

• Institut für Mineralogie

In the course of two projects we will investigate the fractionation of non-traditional stable isotopes (Li, Mg, Fe) for phenocrysts in basalts and andesites in order to obtain time information on magmatic processes. Since previous studies indicate that stable isotope fractionation in magmas is largely driven by kinetic effects due to diffusive processes, one can expect large isotope variations, i.e. isotopic zoning, on the mineral scale. Hence, isotope analyses are performed in-situ (by laser ablation-MC-ICP-MS) with high precision and high spatial resolution. The investigated samples comprise intra-plate volcanic rocks, mid-ocean ridge basalts (MORBs), and andesites from volcanoes above subduction zones. The following questions will be addressed:

• Is chemical zoning in magmatic minerals commonly coupled with isotopic zoning?

• Which mechanisms generate the isotopic (and chemical) zoning and which (magmatic) processes are recorded by such zoning?
• Can we obtain time information (durations) on these processes by using the observed intra-mineral zoning for diffusion modeling?