Applications of U isotope fractionation in nature
Event details
| Date | 08.04.2014 |
| Hour | 16:15 › 17:15 |
| Speaker | Dr Stefan Weyer, Mineralogy Institute, Leibniz University, Hannover DE |
| Location | |
| Category | Conferences - Seminars |
Abstract:
Recent studies revealed that the two long-lived isotopes of uranium (238U and 235U) fractionation during physiochemical reactions, similarly as classical stable isotope systems (e.g. C, O, S) or other metal isotopes (e.g. Cr, Fe or Cu). For very heavy elements, such as U, a nuclear volume-dependent mechanism, so-called nuclear field shift, is the driving mechanism for the observed isotope fractionation in nature, rather than mass dependent isotope fractionation. We developed a technique of high precision U isotope analyses with a double spike on multi collector ICP-MS. With this technique, we could resolve significant 238U/235U isotope variations on Earth (≈ 1.4‰) and in meteorites (> 3‰). In my talk, I will show several examples and potential applications. On Earth, the most significant process that generates U isotope fractionation appears to be redox reactions, in particular during U reduction. Such redox-induced U isotope signatures may be used to characterize redox conditions in ancient periods of Earth’s history. However, yet the driving mechanism of U isotope fractionation during U reduction is unknown. In ongoing studies we investigate the effect of abiotic and biotically induced U reduction on U isotope signatures and which other factors need to be considered for a proper interpretation of geological reservoirs.
Short biography:
Stefan Weyer is an experienced isotope geochemist with a focus on non-traditional stable isotope systematics (i.e. Fe, Li, Cu, Zn, Mo and U). He developed new methods for high precision Fe and U isotope analyses and characterized major reservoirs on Earth (Weyer and Schwieters 2003; Weyer et al., 2008). He applied U isotope signatures as paleoredox tracer (Montoya Pino et al., 2010) and he investigated U isotope fractionation during adsorption (Brennecka et al., 2011), weathering and transport and in anoxic water columns, as well as U isotope variations in meteorites (Brennecka et al., 2010).
Recent studies revealed that the two long-lived isotopes of uranium (238U and 235U) fractionation during physiochemical reactions, similarly as classical stable isotope systems (e.g. C, O, S) or other metal isotopes (e.g. Cr, Fe or Cu). For very heavy elements, such as U, a nuclear volume-dependent mechanism, so-called nuclear field shift, is the driving mechanism for the observed isotope fractionation in nature, rather than mass dependent isotope fractionation. We developed a technique of high precision U isotope analyses with a double spike on multi collector ICP-MS. With this technique, we could resolve significant 238U/235U isotope variations on Earth (≈ 1.4‰) and in meteorites (> 3‰). In my talk, I will show several examples and potential applications. On Earth, the most significant process that generates U isotope fractionation appears to be redox reactions, in particular during U reduction. Such redox-induced U isotope signatures may be used to characterize redox conditions in ancient periods of Earth’s history. However, yet the driving mechanism of U isotope fractionation during U reduction is unknown. In ongoing studies we investigate the effect of abiotic and biotically induced U reduction on U isotope signatures and which other factors need to be considered for a proper interpretation of geological reservoirs.
Short biography:
Stefan Weyer is an experienced isotope geochemist with a focus on non-traditional stable isotope systematics (i.e. Fe, Li, Cu, Zn, Mo and U). He developed new methods for high precision Fe and U isotope analyses and characterized major reservoirs on Earth (Weyer and Schwieters 2003; Weyer et al., 2008). He applied U isotope signatures as paleoredox tracer (Montoya Pino et al., 2010) and he investigated U isotope fractionation during adsorption (Brennecka et al., 2011), weathering and transport and in anoxic water columns, as well as U isotope variations in meteorites (Brennecka et al., 2010).
Practical information
- General public
- Free
- This event is internal
Organizer
- EESS - IIE
Contact
- Prof. Rizlan Bernier-Latmani, EML