One of the many relationships between mantle petrology and atmospheric chemistry: The case of nitrogen.

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• Sami Mikhail, University of St Andrews
• Tuesday 09 February 2016, 16:00-17:00
• Harker 1 seminar room, Department of Earth Sciences.

If you have a question about this talk, please contact John Maclennan.

Understanding the chemical evolution of Earth’s atmosphere and hydrosphere is important, especially with regard to the history of the buzzword-elements (e.g. COHNS ). Of these elements, nitrogen is of particular importance because it is an element that is fundamental to life, a potential hydrogen reservoir in the solid Earth, and it also makes up most of the air we breath (Bebout et al., 2013). A major process in forming planetary atmospheres is mantle degassing via volcanism and the primary control on what volatile elements are degassed by this process is their compatibility in mantle minerals relative to melts and fluids. However, because subduction happens on Earth, it is also necessary to trace the partitioning of volatiles through subduction systems over geological time to understand the long-term co-evolution of the dynamic interior and habitable exterior. In the present, the physiochemical conditions across different tectonic settings cause speciation of nitrogen to vary from one tectonic setting to another, which means the behaviour of nitrogen during magmatism and metasomatism in the mantle is not uniform (Mikhail & Sverjensky, 2014; Li & Keppler, 2014). By combining what is known about the speciation of nitrogen with data for the primordial noble gas abundances in the Earth’s atmosphere, and comparing these data with Earth’s tectonically challenged relatives (Mars and Venus), I have developed a dynamic model which outlines how subduction zones have directly altered the composition of Earth’s atmosphere through time.

References cited (and further reading for those who want more): Bebout et al. 2013. Nitrogen: Highly volatile yet surprisingly compatible. Elements Magazine. 9, 333-338 Li & Keppler. 2014. Nitrogen speciation in mantle and crustal fluids. Geochimica Cosmochimica et Acta, 129, 13–32 Mikhail & Sverjensky. 2014. Nitrogen speciation in upper mantle fluids and the origin of Earth’s nitrogen-rich atmosphere. Nature Geoscience, 7, 816–819

This talk is part of the Department of Earth Sciences Seminars (downtown) series.

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• Department of Earth Sciences Seminars (downtown)
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