New advances in Ar-Ar geochronology and applications to geoscience

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One of the most useful methods of dating rocks ("geochronology") is based on the radioactive decay of potassium (40K) to argon (40Ar), which serves as a long-lived clock over the vast span of geologic and astronomic time. The 40Ar/39Ar dating technique - a variant of the K-Ar dating method - is considered to be one of the most powerful tools currently used in research laboratories worldwide. Understanding the significance of the ages we obtain from such clocks requires a detailed understanding of how the elemental atoms and ions can move through the rocks and crystals in which they accumulate, in a fundamental process known as diffusion. Many factors such as crystal structure, mineral chemistry, Ar solubility, and the presence of defects or flaws in the crystal structure control diffusional behaviour and the effect of these factors will be studied in laboratory experiments and through numerical modelling in two of the most common rock-forming and commonly dated minerals - mica and feldspar. Improved knowledge of these effects may explain enigmatic age discrepancies between different minerals using different geochronological clocks, where rocks in southeastern BC will serve as an ideal field experiment.  Knowledge of all of these fundamental controls will be applied to significant geological problems in Latin and South America, in order to determine the timing of the motions of lithospheric plates around Mexico around 450 million years ago, test models for the formation of large gold deposits in the central Andes, and improve exploration strategies for these deposits in the region, which is a major area of investment for the Canadian mining industry. Thus, the proposed research addresses several fundamental but related questions in geochronology, ore-deposit formation, and plate tectonics.