ESR5

PhD position in Hydrothermal Cooling of the Lower Oceanic Crust

Marie-Curie Initial Training Network ABYSS (ESR5)

Training network on reactive geological systems from the mantle to the abyssal sub-seafloor

Host institution: Ocean & Earth Science, National Oceanography Centre Southampton, University of Southampton (UK)

Secondment institutions: CNRS-Geosciences Montpellier (FR); Leibnitz Universität Hannover (DE); University of Oslo (NO).

The Graduate School of the National Oceanography Centre Southampton seeks to appoint a PhD researcher to investigate the formation of the lower oceanic crust with Pr Damon Teagle and Dr Tim Henstock. This project will integrate fieldwork, petrological and isotope geochemical observations with experimental petrology and numerical modeling to quantify cooling rates and the vigour of deep hydrothermal circulation in the crystallization of the lower oceanic crust. It will involve fieldwork in the Samail ophiolite, Sultanate of Oman, and additional analytical (Benoit Ildefonse, CNRS), experimental (J. Koepke, LUH), and modeling (B. Jamtveit, Oslo) research.

Methods: Geological field mapping of hydrothermal alteration, including mapping and sampling of fault zones, in the lower oceanic crust. Samples will be subjected to detailed petrographic observation to identify hydrothermal fluid-rock interactions and the sequence of secondary mineral formation. Following micro-sampling of secondary phases for mineral composition, stable and Sr isotope measurements will be used to establish fluid evolution pathways and estimate time integrated fluid fluxes from the advection of seawater-derived isotopic tracers. Cooling rates will be determined by combining electron microprobe, electron back scatter (CNRS), and laser ablation ICP-MS analysis of olivine from partially altered rocks to establish crystal orientations and rates of cooling from trace element profiles (e.g., Ca). This information will be integrated with mineral-mineral sub-solidus trace element diffusion experiments (LUH) at appropriate conditions, to improve knowledge of olivine diffusion rates and closure temperatures.

Goals: The primary goal is to end-member test models of the accretion of fast spreading ocean crust. Fluid fluxes, based on tracer transport modeling of the advection of isotopic signals, combined with cooling rate estimates from trace element diffusion, will be integrated with thermal modeling to determine the role of deep hydrothermal fluid circulation in cooling the lower oceanic crust at the mid-ocean ridge axis.

Requirements: Candidates must hold a MSc in Earth Sciences or a closely related discipline. Rigorous numerical skills and a strong fieldwork background are encouraged.

This fellowship is for a period of 36 months starting on (no later than) 1st.Oct.2014.

For further information, contact: Pr Damon A.H Teagle (damon.teagle@southampton.ac.uk)

This position has been filled