On the occurrence and boron isotopic composition of tourmaline in (ultra)high-pressure metamorphic rocks

Autor(en)

Horst R. Marschall, Andrey V. Korsakov, George L. Luvizotto, Lutz Nasdala, Thomas Ludwig

Abstrakt

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(en)

Institut für Mineralogie und Kristallographie

Externe Organisation(en)

University of Bristol, Universität Heidelberg, Russian Academy of Sciences

Journal

Journal of the Geological Society

Band

166

Seiten

811-823

Anzahl der Seiten

13

ISSN

0016-7649

DOI

https://doi.org/10.1144/0016-76492008-042

Publikationsdatum

2009

Peer-reviewed

Ja

ÖFOS 2012

1030 Physik, Astronomie, 105116 Mineralogie

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/cdb2276b-d96a-4500-a933-e270743b71c8