This project will use both conventional microsampling techniques, together with new in situ laser ablation techniques to obtain high precision and resolution isotope data on mineral phases, and to thereby significantly improve our understanding of magmatic differentiation. The simple principle of crystal isotope stratigraphy (CIS) is that crystals growing in a differentiating open magma system record secular changes in the isotope composition of the liquid from which they crystallize. When combined with textural and mineral composition data a detailed history of differentiation can be reconstructed. This philosophy will be developed in two closely related investigations; 1) an examination of the layered cumulate sequence from a contaminated and recharged magma chamber at Rhum, Scotland, and 2) detailed studies of the dated eruption products of open system differentiation at Ngauruhoe volcano, New Zealand. The first study will allow examination of a far more protracted and complete differentiation history than is represented by volcanic rock suites, while the second, by virtue of the excellent time constraints, may enable calibration of open system differentiation through time.
