Three separate tasks are planned. The first is an isotopic investigation of separated mineral phases from "ultradeep" ultramafic xenoliths from kimberlites. The second task is a geochemical and isotopic study of ultramafic xenoliths from several oceanic islands. The third task will be the major focus of our work. It entails development of laboratory capabilities for measuring 238U and 232Th isotopes by mass spectrometry, and will concentrate on the measurement of 226Ra in both whole-rock and separated phenocryst phases. The goal of his work is to gain a better understanding of the timescales and nature of magmatic fractionation processes, magma transport, and the origin of the ubiquitous 226Ra excesses in volcanic rocks from a variety of tectonic settings.
