Redox Conditions During Coseismic Rupture - A Mossbauer Study of Frictional Melts

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9814851O'Hara There is considerable interest in the role of water in the earthquake rupture process, but modern example are very difficult to study. Pseudotachylytes (friction melts) represent one of the few paleoseismic indicators in the rock record that may record aspects of the role of water during the rupture event that caused the partial melt. This study will use Mossbauer spectroscopy to assess the oxidation state of iron in opaque minerals found in several well characterized pseudotachylytes which serves as a proxy for oxygen fugacity in the corresponding paleoseismic zones. If is anticipated that Fe +2/ Fe +3 ratios at individual localities will reveal local variations of oxygen partial pressure and permit the role of fluid compartmentalization in active fault zones to be evaluated.