VKC talk by Kira Musiyachenko| 15 January 2026

Описание: Kira Musiyachenko: Lu-Hf garnet geochronometry: A unique clock for mantle metasomatism

Abstract:
Cratonic mantle xenoliths in kimberlites provide rare direct samples of Archean continental roots, yet interpreting their histories is challenging without reliable age constraints. While petrography, mineral chemistry, and P-T estimates allow us to group xenoliths into petrologically and chemically defined groups, it is far more difficult to determine when the supposed events of melt depletion, refertilization, or metasomatism occurred, or whether spatially scattered fragments record related processes.
Lu-Hf garnet geochronometry has proven highly effective in dating high-temperature crustal rocks, but its application to mantle xenoliths has long been limited by analytical challenges associated with small sample sizes and extremely depleted compositions. Recent advances in laboratory and analytical techniques now make it possible to obtain precise Lu-Hf ages from very small garnet aliquots, expanding the potential of this method for mantle studies. Interpreting these ages, however, requires an understanding of how the Lu-Hf system behaves under mantle conditions.
In this talk, I draw on garnet-bearing mantle xenoliths from three cratons spanning a range of lithologies, to explore what Lu-Hf ages in the mantle actually record. The data show that Lu-Hf ages primarily reflect garnet growth or re-equilibration during metasomatic events, preserving Archean signatures alongside ages associated with later mantle modification. These results highlight how Lu-Hf garnet chronometry can place new temporal constraints on the evolution of the cratonic mantle.