Time scales of deformation and fluid-mediated interactions along the plate interface

PhD position on time scales of deformation and fluid-mediated interactions along subduction zone plate interfaces

Main host institution: Freie Universität Berlin (FUB)
Secondment Institution: Université Pierre et Marie Curie (UPMC) – Paris 6

The Institute of Geological Sciences at Freie Universität Berlin seeks a PhD student to study links between fluid flow patterns and chemical-petrophysical characteristics in subduction zones. The successful applicant will join the Petrology group and work in a multi-disciplinary environment in close collaboration with Timm John in Berlin and Philippe Agard in Paris.

Tasks and Methodology:
A) Constraining the evolution of deformation patterns associated with fluid pathways along exhumed portions of the subduction interface in selected field laboratories (Alps and Tianshan);
B) Constraining the absolute timing of deformation via recrystallized accessory minerals and modeling the duration of fluid circulation(s) through Li-chronometry (i.e. Li-diffusion).
Deformation within dry slabs is often highly localized along the subduction interface, where narrow shear zones preserve a record of enhanced fluid flow with respect to surrounding rocks. Fluids potentially change mineral assemblages and speed up reaction rates, leading to strain-dependent feedbacks between fluid flow and rock rheology. The detailed study of such shear zones will form the basis for reconstructing the sequence of tectonometamorphic events in selected field areas at or near exhumed subduction interfaces in mountain belts. A key to understanding the localization process will be to improve the spatial and temporal resolution of transient, grain-scale processes that control the dynamics of shear zone evolution. Growth zones in datable accessory minerals will be used to obtain information on the age of microstructures as well as on the timing of shear zone formation. The analysis of chemical gradients across strain gradients in shear zones will enable Li-chronometric diffusion modeling to estimate the duration of fluid-rock-deformation processes. Overall, this project will generate a better understanding of how localized deformation and fluid flow along the subduction interface are linked in space and time.

Methods: Tectonics, field mapping, petrology, diffusion modelling, geochronology.

Candidates for the job must hold an MSc in Earth Sciences or a related discipline. Experience in mineralogy, petrology, geochemistry, structural geology and geodynamics is highly advantageous.
Berlin is one of the most dynamic and liveable cities in Europe with very active scientific and cultural scenes. The Geoscience Dept. of the FU-Berlin is a member of Geo-X, a consortium of closely knit Earth Science institutions in the Berlin-Potsdam area that pool their resources to offer a world-class laboratory infrastructure. The PhD candidate will also spend ~6 months in Paris at the second mentor institution with Philippe Agard (UPMC), and will also collaborate with Mark Handy (FU Berlin), Sonia Tonarini (IGG Pisa) and Martin Engi (UB, Bern).

For further information, please contact Timm John (timm.john@fu-berlin.de) or Philippe Agard (philippe.agard@upmc.fr)

Starting date is expected between December 2013 and February 2014.
Deadline for application is 13th November 2013.