Argonne National Laboratory

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Isotope Geochemistry via Sn Isotope Fractionation Using Inelastic X-Ray Scattering of Synchrotron Radiation

LDRD Seminar
Esen Ercan Alp (XSD)
March 13, 2018 12:30PM to 1:30PM
Building 203

Abstract: Stable isotope fractionation is a consequence of geological processes and it has important applications in geochemistry. While the effect is easier to observe in light elements, the heavier elements may also show natural stable isotope fractionation and give valuable petrogenetic information. Iron isotope fractionation has been quite popular, particularly with the possibility of obtaining reliable results with multiple methods. Among them our group has advanced the application for isotope fractionation using a relatively new technique of measuring force constant via nuclear resonant scattering. Based on the success of iron-based measurements, we have expanded this method to tin geochemistry. Tin possesses the largest number of stable isotopes and the greatest mass range of any element, ranging in atomic weight from 112 to 124, largely due to the "magic number" closed proton shell for Z = 50. However, established methods of mass spectroscopy requires spiking with isotopes that may not be available due to scarcity.

We developed a synchrotron-based method to circumvent difficulties related to determination of Sn isotope fractionation. It is important to develop a new proxy for isotope geochemistry studies that will indicate redox conditions at the time of earth’s formation. We have measured Sn and iron phonon density of states in several Fe-Ni-Sn alloys, and in several glasses under pressure to determine force constant and isotope fractionation