PhD positions for 2017 start

I am involved in three exciting projects at the University of Cambridge, each of which is part of the Cambridge Earth Systems Science DTP and will base the student in the Department of Earth Sciences.


Chemical geodynamics: Combining geochemical and geophysical constraints on mantle structure and processes

 

Degenerate mantle chemical structures obtained from limited surface sampling.

Degenerate mantle chemical structures obtained from limited sampling at Earth’s surface.  The development and application of novel statistical techniques will enable us to quantify the sptial information content of ocean island and MORB geochemistry.

Large geochemical datasets have been used to infer hemispherical compositional structure in Earth’s mantle, the presence of chemically isolated domains at the core mantle

boundary, and define an isotope ‘zoology‘ of domains tracing processes from lithospheric delamination to continental crustal recycling.  However, these observations have not been rigourously combined with complementary geohpysical datasets, which probe the mantle’s seismic, density, and phase structure.  In this project the student will combine field, analytical, and statistical work to bridge the gap between the geochemical and geophysical pictures of mantle structure and dynamics.

Lead supervisor: Oliver Shorttle
Co-supervisor: John Maclennan


Ice and fire: feedbacks between glaciation, volcanism and climate

Deglaciation has triggered dramatic increases in volcanism on Iceland and been linked to globally increased volcanic fluxes at arcs.  However, still relatively few datasets provide local geological and geochemical evidence for a causal link between deglaciation and volcanism.  This project will collect new geochemical data on an exceptional suite of samples from Mount Haddington, James Ross Island, on the northern Antarctic Peninsula. These data will probe the volcano’s response to multiple deglaciations over 6 Myr.

Lead supervisor: Marie Edmonds
Co-supervisors: Joanne Johnson (BAS), Oliver Shorttle


The redox structure of the Icelandic plume: new constraints from iron stable isotopes

The oxygen content of the mantle, as captured in its oxidation state (fO2), determines how the mantle melts, how magmas transport volatile elements, and ultimately buffers the redox evolution of Earth’s surface environment.  At present our understanding of mantle oxidation state is limited by the available geochemical proxies, none of which uniquely capture fO2 variability.  To overcome these challenges this project will make Fe isotope analyses on a suite of geochemically well characterised samples (e.g. Murton et al. 2002; Shorttle et al. 2015) from the Reykajnes Ridge.  Fe isotopes will be sensitive to the oxidation state of the mantle, as well as its lithology.  With independent constraints on mantle lithology, and fO2, the component of redox heterogeneity captured by Fe isotopes will be identified, establishing the utility of this proxy in magmatic rocks and opening the potential to map the redox structure of the Iceland plume.

Lead supervisor: Helen Williams
Co-supervisors: John Maclennen, Oliver Shorttle