Trace defects and radiation damage in minerals and other Earth materials: structural studies and applications

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Trace defects, including radiation-induced varieties representing incipient radiation damage, exert important influence on all types of physical-chemical properties of minerals (e.g., color, electrical conductivity, magnetism and reactivity) and have a broad range of applications in Earth sciences from geochemical modeling to dosimetry, geochronology, immobilization of heavy metals, nuclear waste disposal, and mineral exploration. Quantitative understanding and applications of trace defects in minerals require accurate information about their speciation and local structural environments. Accordingly, this research program is directed towards the study of structures and applications of trace defects in minerals and related materials. Scientific approach includes field-based investigations to identify trace defects in minerals of important geological applications and/or of direct environmental relevance. Laboratory experiments on the synthesis of these minerals under controlled conditions are designed to complement field-based investigations and to provide synthetic materials for spectroscopic studies. Trace defects in minerals and synthetic analogs are characterized quantitatively by use of multiple spectroscopic techniques, particularly electron paramagnetic resonance (EPR) spectroscopy. First-principles calculations on the electronic structures of defects in minerals are used to aid quantitative interpretation of results from spectroscopic studies. Specific research objectives for the next five years are: 1) crystal-chemical controls on the uptake of REE and U in apatites and other accessory minerals, 2) discovery and characterization of radiation-induced defects in apatites, fluorite and feldspars by use of multi-frequency EPR spectroscopy, 3) first-principles modeling of selected defects in apatites and fluorite, and 4) applications to field-based geochemical and environmental studies and to exploration of mineral deposits. This research program on the discovery and quantitative study of new defects in minerals and related materials is unique in the Canadian Earth science community and is innovative, as evidenced by its multidisciplinary approach and by the continuing development of new experimental techniques.