A set of Moessbauer spectroscopy experiments are proposed, designed to enable true quantification of Fe3+ and Fe2+ contents in minerals. Valence state- and site-specific recoil-free fraction "correction" factors for relating peak areas to species abundance will be determined, four commercially-available software packages for processing of Moessbauer data will be tested on a set of petrologically-important minerals, and the capabilities of modern instrumentation and modeling will be highlighted through a set of three, two-year student projects designed to demonstrate the abilities of the new technique. The intellectual merit of this project of this project has four aspects: (1) improvement of Moessbauer analyses of wide range of minerals, (2) understanding iron distribution in pyroxene, which is a common rock-forming mineral on all terrestrial planets, (3) enabling for the first time analyses of the redox state of iron in feldspars, and (4) study of an important metamorphic mineral, chlorite, within the necessary, well-constrained petrologic framework. The broader impact of this research will be worldwide improvements in interpreting Moessbauer spectroscopic results from mineralogical studies. The error bars on future studies of iron in minerals using Moessbauer spectroscopy will be effectively reduced, and it will be demonstrated that this technique has new capabilities that can be used to study geologic materials even in tiny samples or those with a low percentage of iron. This project will have great educational impact on the six women undergraduates (two each year) who will make these projects the topics of senior theses.
