Compositional variation of tourmaline at high- and ultrahigh pressure

Tourmaline has been widely used as a petrogenetical indicator. There is, however, no general agreement if and how the compositional variability of tourmaline could be potentially used as a geobarometer. We want to test the hypothesis of enhanced potassium incorporation as well as increased incorporation of tetrahedral B into the tourmaline structure by a series of tourmaline-fluid (Ca,Na,K)-exchange experiments at ultrahigh pressure. If so, significant tetrahedral B must have a significant effect on the B isotope fractionation between fluid and tourmaline, which will be calibrated. The experimental part of the project will be accompanied by crystal-chemical and B isotopic analyses of tourmaline from high- and ultrahigh pressure rocks using well-known, previously characterized samples. We expect a better understanding of the large-scale, long-term B cycle during subduction processes.

Fig.: SEM-picture of synthetic K-rich tourmaline (with talc)

Contact

Dr. Bernd Wunder

Prof. Dr. Wilhelm Heinrich

Partner

 

Dr. Birgit Plessen, GFZ, Sektion 5.2

Dr. Alexander Rocholl, GFZ, Sektion 3.1

Dr. Robert Trumbull, GFZ, Sektion 3.1

Dr. Eleanor Berryman, Department of Geosciences, Princeton University

Dr. Andreas Ertl, Institut für Mineralogie und Kristallographie, Universität Wien

Prof. Dr. Gerhard Franz, Angewandte Geowissenschaften, Technische Universität Berlin

Dr. Piotr Kowalski, Institute of Energy and Climate Research, Forschungszentrum Jülich

Dr. Martin Kutzschbach, Angewandte Geowissenschaften, Technische Universität Berlin