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Earth Sciences at the University of Fribourg

Bern-Fribourg Master in Earth Sciences

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Details of Master Thesis Topic (Module D):
Pressure dependence for the compositions of accessory phases in the Bergell tonalite?

Master Thesis title: Pressure dependence for the compositions of accessory phases in the Bergell tonalite?
Description:The Bergell tonalite intruded the Alpine nappe stack at 32 Ma just north of the Insubric line. The tonalite has a peculiar geometry with a tail close to Bellinzona and a roof in Val Malenco, Italy. The pressure estimates range from 7-8 kbar in the tail to 3.5 kbar in the roof, showing that the tonalite magma crystallized at different depth. Titanite, zircon, allanite and apatite are common accessory phases in the tonalite. The Ti-in-zircon and the Zr-in-titanite thermometers are widely used in the literature. These thermometers were mainly calibrated at 10 kbar.

In this project the tonalite is used as a natural laboratory to investigate the response of accessory phases to different pressures. In a sample suite from the tail to the roof of the pluton, the composition of the accessory phase titanite, zircon and apatite will be measured for major and trace elements. Based on this data we will evaluate the effect of pressure on the Ti-in-zircon, Ti-in quartz and the Zr-in-titanite thermometers and we will investigate if there is a systematic distribution of Zr and Ti in allanite and apatite. Additionally the REE partitioning between all these phases will be investigated. Apatite, allanite and titanite can host also volatiles such as H2O, F, Cl, S and CO2 and thus might provide information on the evolution of volatiles in the magma.

The project will include fieldwork, mineral separation, petrographic characterization of thin sections, electron microprobe and laser ablation mass spectrometry analyses and SIMS analyses.
Advisors:Prof. Jörg Hermann, Prof. Daniela Rubatto, Prof. Alfons Berger
Specialities:EM, GEOL
University: BE

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