skip to primary navigationskip to content
 

E404: Carbon and sulfur cycling in the Earth’s mantle over the last 4 Ga: new clues from novel stable isotopes (Lead Supervisor: Helen Williams, Earth Sciences)

Supervisors: Helen Williams (Earth Sciences), Oliver Shorttle (Earth Sciences/Institute of Astronomy), Frances Jenner (Department of Earth and Environmental Sciences, The Open University) and Dr Heye Freymuth (Earth Sciences)

Importance of the area of research:

The tectonic recycling of surface material by subduction is widely considered to contribute to the mineralogical and chemical enrichment of ocean island basalt (OIB) source regions (e.g. Jackson et al., 2007 and references therein).  However, the impact of tectonic recycling on the spatial and temporal distribution of volatile elements such as carbon and sulfur within the mantle is poorly known.  A major contributor to this uncertainty is because these elements are lost during magmatic degassing, making the reconstruction of their concentrations in primary mantle-derived melts challenging.  While recent studies have demonstrated the potential of chalcophile trace elements (e.g. Jenner et al., 2012), melt inclusions and novel stable isotopes (e.g. Andersen et al., 2015) to unravelling this complexity, no study has as yet combined these different approaches, and secular variations in volatile recycling remain almost completely unexplored.

Project summary:

This project will explore carbon and sulfur cycling and mantle source region heterogeneity using a combination of novel stable isotope and geochemical tracers. Through this it will be possible to explore the interplay between partial melting processes, mantle chemical and mineralogical heterogeneity and volatile element cycling.  Key ocean island localities will be targeted, which possess abundant evidence for recycled components in their source regions. The study will also extend its reach back over Earth history by considering komatiites, with this project's analyses contributing important new results to the debate about the origin (thermal vs. compositional) of these enigmatic high-degree melts.

What the student will do:

This project presents an exciting chance for a student to combine multiple state-of-the-art microanalytical, trace element and isotopic techniques and apply these to a fundamental problem in Earth Sciences: that of volatile cycling between the Earth's surface and deep interior. The student will focus on well-characterised archive oceanic basalt samples from a range of localities including the main geochemical domains of the Iceland plume as well as larger volume mantle melts as represented by picrites and komatiites.  The student will use then use their trace element, isotopic and volatile element data to explore the links between tectonic recycling and mantle source region heterogeneity, longevity and volatile contents.

Please contact the lead supervisor directly for further information relating to what the successful applicant will be expected to do, training to be provided, and any specific educational background requirements.

References:

Andersen et al., (2015) The terrestrial uranium isotope cycle. Nature 517 p 356-359

Jackson et al., (2007) The return of subducted continental crust in Samoan lavas. Nature 448, 684-687

Jenner et al., (2012) Chalcophile element systematics in volcanic glasses from the northwestern Lau Basin. Geophysics, Geochemistry, Geosystems 13, 6

Follow this link to find out about applying for this project.

Other projects available from the Lead Supervisor can be viewed here.

Filed under: