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PhD in Earth Sciences – Experimental petrology H/F

This offer is available in the following languages:
Français - Anglais

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General information

Reference : UMR7327-MARROU0-009
Workplace : ORLEANS
Date of publication : Wednesday, May 20, 2020
Scientific Responsible name : ARBARET Laurent
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 October 2020
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly

Description of the thesis topic

Title « Segregation and extraction of late magmatic melt and fluids in mushes: experimental approach at HP and HT »

Both the Earth's crust and atmosphere are the result of magmatic activity, expressed as volcanoes and great bodies of granite. Describing their dynamics is essential to understanding planetary growth, differentiation and the social impacts from volcanic activity. However, there is currently a paradigm shift in progress: instead of mostly liquid, magma bodies are now inferred to be bodies dominated by crystal-rich mush, a mix of crystals, and silicate liquid, that can be as large as 500,000 km3 (Ward et al., 2014; Delph et al., 2017). Furthermore, this model of a mush zone with limited pockets of mobile magmas (Bachmann and Bergantz, 2004, 2008) has been generalized as a possible continuum over the entire crust from the deep ductile hot crust to the shallower chambers opened to volcanic systems. This is conceptualized as the so-called Trans-Crustal Magmatic System (TCMS, Cashman et al., 2017; Fig. 1).
An obstacle to progress is that the physics of magma mush is very poorly understood, invoking ill-constrained processes such as separation of melts and fluids from low porosity source regions, mush destabilization, and segregation of magmatic fluids from underplated magmas (Christopher et al., 2015). It is nearly impossible to obtain examples of a 'living mush', or to make detailed real-time measurements in the field. The object of this proposal, MECAMUSH, is to describe and rationalize the behavior of magma mush by a combination of novel, linked experimental and numerical modeling techniques.
The experiments will be conducted at ISTO by using the Paterson and Griggs apparatus that are pressure vessels capable of measuring the rheology of magmas up to 12 Kbars in order to explore the entire TCMS. The starting products are synthetic hydrous haplotonalitic mushes of plagioclase crystals (Picard et al., 2013). The applicant will measure the rheology in situ and analyses after experiments the textures of the deformed mush : mineral shapes fabrics, strain localisation, crystal damage by using SEM, 3D tomographic imaging (Tomograph ISTO, 1 µm and synchroton TOMCAT, Paul Sherrer Institut, Villingen, switzerland), EBSD (ISTO) and Raman spectrometry (SEM TESCAN et 514, 632, and 785 nm lasers, ISTO).
The experimental results will be coupled to numerical simulations done at ISTerre and Seattle (force chains development) and at Montpellier (LMGC, shear strain localisation and crystal brakeage). This thesis is part of the ANR MECAMUCH project.

Work Context

This thesis will take place at the Institut des sciences de la Terre d'Orléans (ISTO, The ISTO laboratory is under the supervision of the CNRS (Délégation régionale Centre Limousin Poitou Charentes), the University of Orléans and the Bureau de Recherche Géologiques et Minières (BRGM). The thesis is administratively attached to the Ecole Doctorale ED 552 - Énergie - Matériaux - Sciences de la Terre et de l'Univers (EMSTU) of the university of Orleans.

All expenses related to this thesis will be paid by ARN MECAMUSH.

Constraints and risks

The student will be registered at the university of Orleans and administratively attached to l'Ecole Doctorale ED 552 - Énergie - Matériaux - Sciences de la Terre et de l'Univers (EMSTU).
Training in the risks inherent in high pressure and high temperature experiments as well as RAMAN and tomographic analyses must be followed at the beginning of the thesis.
Missions lasting one to three weeks are planned to France (Chambéry, Montpellier, among other) and to Seattle (USA) and Villingen (switzerland).

Additional Information

We seek excellent and highly motivated candidates interested in combining studies in experiments and numerical modelling in magmatology. The Institute of Geological Sciences of University of Orléans provides a stimulating research atmosphere with the possibility to interact between two research teams in geodynamics and magmatology, respectively. The ideal date for the start of the projects will be October 1st 2020. The project is funded for a maximum duration of three years. Required is a MSc in Earth Sciences or an equivalent degree. Applications should include a cover letter with a statement of research interests and motivation to undertake a PhD, a CV, transcripts of academic degrees as well as names and addresses of two references. English speaking students are welcome as the thesis, and the defense as well, could be in English.

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