On the occurrence and boron isotopic composition of tourmaline in (ultra)high-pressure metamorphic rocks
Horst R. Marschall
Andrey V. Korsakov
George L. Luvizotto
Lutz Nasdala
Thomas Ludwig
10.6084/m9.figshare.3454664.v1
https://geolsoc.figshare.com/articles/dataset/On_the_occurrence_and_boron_isotopic_composition_of_tourmaline_in_ultra_high-pressure_metamorphic_rocks/3454664
<p>The extensive <em>P–T</em> 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 K<sub>2</sub>O contents in Tur are probably not related to UHP growth or equilibration. The B isotopic composition of (U)HPM Tur ranges
in δ<sup>11</sup>B 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 δ<sup>11</sup>B 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.
</p>
2016-06-21 12:16:28
δ 11 B values
UHP stability
Coesite inclusions
UHPM
Kokchetav Massif
occurrence
element chemistry
Tur
Raman spectroscopy
chemical variability
paper reviews
High K 2 O contents
element composition
fluid influx
UHP growth
geochemical studies
Geology