Isotope Ratio and Trace Elemental Imaging of Minerals by Secondary Ion Mass Spectometry

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This is a proposal to develop secondary ion mass spectrometry (SIMS) based imaging isotope ratio techniques for isotopic microanalysis of mineral deposits. This capability will be combined with SIMS based trace element microanalysis. The petrogenesis of ore deposits often involves an aqueous solution by which the ore-bearing components are transported. These hydrothermal solutions also transport sulfur. Different aqueous processes give rise to different 34S/32S isotope fractionations. The 34S/32S ratios can provide important indications of the sulfur origin, and by extension, the origin of economically important metals. Isotope ratio and trace element imaging show the interrelationships of different mineral generations. These generations often coexist within a single mineral grain. The PIs have demonstrated that imaging SIMS can successfully identify the location of trace gold levels ("invisible" gold) in pyrite rims, and that isotope ratio imaging of meteoritic materials highly enriched in deuterium is possible. However, extension to 34S/32S isotope ratio imaging requires further innovation and many careful measurements. In Phase II, these imaging techniques will be extended to microanalytical age dating and microanalytical trace element petrogenesis.