Chlorine isotopes in hydrothermal systems and the global Cl cycle

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The total value of all mining and mineral processing industries was $31.9 billion in 2009 (Natural Resources Canada 2011). Therefore, the mining industry is a significant contributor to the Canadian economy and their exploration and development of mineral deposits can have a significant economic and societal impact in remote areas with no other significant industry such as in Canada's North. This proposal is concerned with studying a range of hydrothermal mineral deposit types that form from large volumes of hot saline fluids at different temperatures and pressures in the Earth's crust. A common feature of these deposits is that all the mineralizing fluids contained significant amounts of dissolved chlorine, which forms chemical complexes with the metal ions and allows higher concentrations of metals to be transported by the water from the metal source regions to the area where the ore deposit formed. As such the chlorine in these fluids is a major component of the ore forming system. In ore deposits, droplets of the mineralizing solution can be trapped in minerals as fluid inclusions and retain evidence of the chemistry of the mineralizing fluids and the environment in which they formed. The research proposed here is concerned with the analyses of these ancient fluids for the bromine and chlorine isotopic composition of the fluids. These techniques have been successfully used to recognise the source of chlorine in mineralizing systems and, in some cases, also the source of the fluid itself, which allows us to constrain models of how a particular deposit was formed. Furthermore, we seek to use a new analytical technique, secondary ionisation mass spectrometry, to measure chlorine, bromine and chlorine isotopes in chlorine bearing minerals. Having the ability to measure chlorine isotopes in liquids and minerals in hydrothermal systems will enable us to understand the role that hydrothermal systems play in the global chlorine cycle (e.g. in transporting chlorine from the mantle to the surface of the Earth), will improve our understanding of the origin of mineral deposits and, will have a direct impact on exploration strategies for hydrothermal deposits in Northern Canada.