Further development and application of the ReOs isotope system in crustal geochronology

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Geochronology is the science of determining absolute geological time using radioactive decay of unstable isotopes in Earth materials (rocks, minerals, ores). Geochronology requires integration of Physics, Chemistry and Mathematics with the Geosciences to understand the processes that have shaped our planet over a 4.6 billion year history. The rhenium-osmium (187Re-187Os) radioactive isotope system is one of the last to be implemented in the Geosciences, due mainly to analytical difficulties. Although the Re-Os system is only applicable to selected crustal rocks and minerals, these happen to be the rock and mineral types for which the more commonly used radioactive dating system such as U-Pb, Ar-Ar and Rb-Sr cannot generally be used to provide age dates. The proposed research will focus on three projects in which accurate and precise crustal geochronology will provide a major scientific advancement of knowledge relating to regional and global-scale crustal processes. Research in Re-Os geochronology will applied to the evolution of the Proterozoic Earth by dating of organic-bearing shales from a variety of basins worldwide. The aims of the research are to: 1/ provide absolute age control for key Proterozoic strata associated with global glaciations and 2/ To provide precise age control for the biologically-critical Ediacaran System in Earth history (635-542 Ma) with which to evaluate and test models of cause-effect between changes in the Earth's surface conditions (glaciations) and biological evolution. The second project will use common sulfide minerals like pyrite to constrain the timing of fluid flow events in sedimentary basins using the Re-Os method. Similarly, the generation and flow of hydrocarbons (oil) in sedimentary basins can be directly dated using Re-Os. Coupling both these methods to study aqueous and hydrocarbon fluid flow in the same basin will provide critical timing information with which to test the various models of the driving geological force(s) behind basinal fluid flow. Lastly, a study of the fundamental nature of Re and Os in oil will be undertaken to provide a sound basis for the implementation of the Re-Os isotope system in petroleum exploration.