9628260 Valley This research is a continuation of work to develop and apply new techniques for micro-analysis of stable isotope ratios. The PI will analyze oxygen isotope ratios in zircons from metamorphosed igneous rocks of the Grenville and Superior Provinces of N. America. In the Grenville, one goal of the zircon research will be to map the limits of a domain of high igneous (18O values for anorthosite-suite magmatism, believed to represent anomalous conditions in the deep crust. In the Superior Province, preliminary analysis of zircons show significant differences in (18O that appear to correlate to the amounts of crustal contamination. Limited field work in key areas and analysis of co-existing mineral will test the uniqueness or generality of the data. Individual zircons will be analyzed by ion probe for zonation or inheritance of (18O and by electron probe for zonation and alteration. Preliminary studies suggest that distinct domains and (18O differences will be found and that the analysis of zircons will have broad significance for the magnetic evolution of critical portions of the Canadian Shield. This may lead to new criteria for assessing the tectonic assembly of the Grenville, or various accretionary plate tectonic processes that are now proposed for crust formation in the Superior Province.
