On the occurrence and boron isotopic composition of tourmaline in (ultra)high-pressure metamorphic rocks
- Author(s)
- Horst R. Marschall, Andrey V. Korsakov, George L. Luvizotto, Lutz Nasdala, Thomas Ludwig
- Abstract
The extensive P-T stability and the high chemical variability of tourmaline (Tur) together with its common occurrence in metasediments proves its high potential for petrological and (isotope) geochemical studies on fluid-rock interaction in subduction- and collision-related rocks. This paper reviews the occurrence, major element chemistry and boron isotopic composition of Tur in high- and ultrahigh-pressure metamorphic (UHPM) rocks. In addition, it presents a new discovery of coesite-bearing Tur (schorl) from the Erzgebirge (Germany), as well as Tur (dravite) related to the retrograde history of coesite- and diamond-bearing rocks from the Erzgebirge and the Kokchetav Massif (Kazakhstan). The scarce data on worldwide occurrences of (U)HPM Tur reveal a high occupation of the crystallographic X-site (dominated by Na) and the possible presence of excess B, with little further distinctiveness in its major element composition when compared with Tur from medium-grade rocks. High K2O contents in Tur are probably not related to UHP growth or equilibration. The B isotopic composition of (U)HPM Tur ranges in 11B from -16 to +1, with many samples in or below the range of continental crust. In contrast, Tur formed during retrograde fluid influx typically shows high 11B values (up to +28), suggesting heavy-B fluids infiltrating the exhuming (U)HPM units. Coesite inclusions in Tur, characterized by Raman spectroscopy, are regarded as the best indicator for its UHP stability.
- Organisation(s)
- Department of Mineralogy and Crystallography
- External organisation(s)
- University of Bristol, Scientific Software Center, Russian Academy of Sciences
- Journal
- Journal of the Geological Society
- Volume
- 166
- Pages
- 811-823
- No. of pages
- 13
- ISSN
- 0016-7649
- DOI
- https://doi.org/10.1144/0016-76492008-042
- Publication date
- 2009
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 1030 Physics, Astronomy, 105116 Mineralogy
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/cdb2276b-d96a-4500-a933-e270743b71c8