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A PhD student position in high-pressure experimental geoscience at Bayerisches Geoinstitut, University of Bayreuth, Germany The Bayerisches Geoinstitut, University of Bayreuth, Germany, is seeking a talented and highly motivated PhD candidate to be working in the domain of high-pressure experimental geosciences in the frame of the research grant of Prof. Dr. Tomoo Katsura by German Research Foundation (DFG). In this project, Si self-diffusion coefficients of Fe-free and Fe-bearing single-crystal wadsleyite will be determined as a function of temperature and water content, as is described in the separate page. This position is for three years and available from October 2014. Applicants should have a master or equivalent degree, knowledge of solid earth science, and basic background of physics, chemistry and mathematics in the level of the first year of college. Experience of high pressure and temperature experiments is not required. The working language is English, and knowledge of German language is unnecessary. Review of applications and successive evaluation will continue until the position is filled. Applications should include a CV in the “europass” format, a concise but concrete summary of master thesis, copies of transcript and certificates, and a personal letter concisely describing yourself and your research interest, and be sent by email to the following address. Further information should be directed to Prof. Katsura directly. Prof. Dr. Tomoo Katsura Professor of Structure and Dynamics of Earth Materials Director of Bayerisches Geoinstitut, University of Bayreuth 95440 Bayreuth, GERMANY Tel: +49(0)921 553791, Fax: +49(0)921 553769 Email: Tomo.Katsura@unibayreuth.de Title: Measurement of Si self-diffusion coefficients of wadsleyite as a function of temperature and water content Project description: Dynamic motion in the mantle accounts for a wide variety of geological and geophysical phenomena. Understanding dynamic mantle flow is therefore essential for solid-state geophysics. Rock deformation experiments have shown a large decrease in the creep strength of mantle minerals by hydration. However, deformation experiments are technically difficult, and the inherent lack of control on key parameters makes interpretation of experimental results problematic. Measurements of Si self-diffusion coefficients have the potential to provide an essential and independent source of information about the high-temperature rheology of minerals, because the slow high-temperature creep of silicate minerals should be controlled by Si self-diffusion. We have studied the effect of water on the Si self-diffusion of forsterite [Fei et al., 2013]. This study suggests that the effect of water on mantle rheology is much smaller than previously considered; although the water content exponent on the olivine rheology was considered to be 1.2, it is actually only 0.3. This striking conclusion should be extended by examining other important mantle minerals. Wadsleyite is a dominant constituent mineral in the mantle transition zone. In this study, we will measure Si self-diffusion coefficient of both Fe-free and Fe-bearing wadsleyite with water contents from <1 to 1000 ppm at temperatures of 1400 and 1600 K, determining them as a function of temperature and water content. In this kind of study, use of single crystal samples is essential for reliable measurement. We will synthesize wadsleyite single crystals based on the techniques developed in our previous study [Shatskiy et al., 2009]. The measurement of Si self-diffusion coefficients of wadsleyite will be conducted by following those in our previous study for forsterite [Fei et al., 2012; 2013]. For the iron-bearing samples, pre-annealing and diffusion annealing will be conducted under constant oxygen fugacity buffered by Mo + MoO2. Based on the results of this project, we will examine and improve our understanding of the effects of water on mantle rheology. This work will provide important insights required to properly understand the dynamic behavior of the mantle. References Fei, H. Z., C. Hegoda, D. Yamazaki, M. Wiedenbeck, H. Yurimoto, S. Shcheka, and T. Katsura (2012), High silicon self-diffusion coefficient in dry forsterite, Earth Planet. Sci. Lett., 345, 95-103. Fei, H., M. Wiedenbeck, D. Yamazaki & T. Katsura (2013), Small effect of water on upper-mantle rheology based on silicon self-diffusion coefficients, Nature, 498(7453), 213-215. Shatskiy, A., K. D. Litasov, T. Matsuzaki, K. Shinoda, D. Yamazaki, A. Yoneda, E. Ito, and T. Katsura (2009), Single crystal growth of wadsleyite, Am. Miner., 94(8 |
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3楼2014-06-05 17:20:46
zhaoligood
专家顾问 (正式写手)
Chemical NMRer
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