REDOX RATIOS WITH RELEVANT RESOLUTION - SOLVING AN OLD PROBLEM BY USING THE SYNCHROTRON MICROXANES PROBE

In situ measurements of the oxidation state of iron in common minerals have been made by using the synchrotron microXANES (SmX) technique, T he results compare very well with wet-chemical and Mossbauer spectrosc opic analyses of the same samples, Areas of 10 x 20 mu m have been mea sured successfully, and the results demonstrate that both zoning of Fe 3+ and the effect of oxide inclusions on bulk analyses can be quantifi ed. Such sample heterogeneity cannot be detected by conventional bulk analytical techniques, The ability to measure Fe3+/Sigma Fe with spati al resolution comparable to that of the electron probe further enhance s the importance of microbeam techniques in the earth and planetary sc iences, Direct measurements of elemental oxidation states that can con strain oxidation-reduction processes are now possible with close to th e spatial resolution of traditional compositional analyses derived fro m electron, or ion, beam and optical microscopic techniques. New, more intense, synchrotron sources such as the Advanced Photon Source at Ar gonne National Laboratory, are becoming available for analyses of 1-10 mu m areas.