Rare earth elements in zircon: a review of applications and case studies from the Outer Hebridean Lewisian Complex, NW Scotland
Martin J. Whitehouse, 2003. "Rare earth elements in zircon: a review of applications and case studies from the Outer Hebridean Lewisian Complex, NW Scotland", Geochronology: Linking the Isotopic Record with Petrology and Textures, D. Vance, W. Müller, I. M. Villa
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Rare earth element (REE) analysis of zircon coupled with high spatial resolution U-Pb geochronology and imaging is emerging as a useful petrogenetic tool capable of providing a link between dated zircon growth and contemporaneous magmatic conditions or metamorphic reactions. Notable amongst recent studies has been the link established between zircon growth in equilibrium with garnet and characteristic heavy REE depletion in zircon which has enabled the dating of specific pressure-temperature (P-T) evolution. Links to other REE-bearing minerals have yet to be established but have similar potential for dating P-T pathways. A brief review of recent applications in both igneous and metamorphic zircons is presented here to illustrate the range of investigations in this rapidly developing area. The method is then applied to two case studies from the late-Archaean Lewisian Composite Terrane of the Outer Hebrides, NW Scotland. In both cases, these new zircon REE analyses reveal previously unknown events in the early history of these samples, as well as clarifying the relationship of different zircon growth phases in relation to the geochronology.
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Isotope geochemistry has produced many technical developments in the past decade or so that have revolutionized the potential information available on the tectonics of metamorphic belts from geochronology. These include the ability to date minerals and rocks on small spatial scales, scales that at last approach those from which other types of information — structural and petrological — are obtained. However, interpreting the new data, and their integration with the other datasets available, is not straightforward and requires careful chemical and textural observations that go hand-inhand with the geochronology. The increasing realization of the importance of this approach has led to a number of symposia at international conferences devoted to this topic in recent years. The set of papers in this book emanates from one such symposium and describes recent progress in integrating this new information with other datasets from metamorphic petrology on a mineral and sub-mineral scale.