Distributions of Y plus REE and Sc in tourmaline and their implications for the melt evolution; examples from NYF pegmatites of the Trebic Pluton, Moldanubian Zone, Czech Republic

Investor logo
Investor logo

Warning

This publication doesn't include Faculty of Economics and Administration. It includes Faculty of Science. Official publication website can be found on muni.cz.
Authors

ČOPJAKOVÁ Renata ŠKODA Radek VAŠINOVÁ GALIOVÁ Michaela NOVÁK Milan

Year of publication 2013
Type Article in Periodical
Magazine / Source Journal of Geosciences
MU Faculty or unit

Faculty of Science

Citation
Doi http://dx.doi.org/10.3190/jgeosci.138
Field Geology and mineralogy
Keywords Y plus REE and Sc; tourmaline composition; melt evolution; LA-ICP-MS; NYF pegmatites; Trebic Pluton
Description Tourmalines from NYF and mixed (NYF + LCT) pegmatites of the Trebic Pluton (Moldanubian Zone, Czech Republic) are generally characterized by variable and relatively high concentrations of Y + REE (4-457 ppm) and Sc (18-765 ppm). They show enrichment in LREE (Ce > La); the chondrite-normalized REE patterns decrease uniformly from La to Tb; Tb to Tm are mostly below the detection limits (<0.01-0.08 ppm) and are followed by an upturn to Yb and Lu. Our textural and paragenetic observations indicate that growth of magmatic tourmaline reflects Y + REE contents in the melt. Tourmaline is highly compatible with Sc and shows exceptionally high contents of Sc compared to the analyzed host pegmatite units (less than 1 ppm Sc). The contents of Sc positively correlate with Sigma Y + REE. Two distinct evolutionary trends of trace-elements in tourmaline were distinguished. (i) A conspicuous increase in Y + REE and Sc in tourmaline (dravite, Ca-rich dravite) from primitive euxenite-type pegmatites reflects their enrichment in the melt with the progressive crystallization and fractionation. It also was enhanced by low P (<0.02 wt. % P2O5) and Ca contents (<0.8 wt. % CaO) in host pegmatite unit preventing precipitation of Y + REE phosphates and allanite, respectively. (ii) Tourmaline (schorl, fluor-schorl, fluor-elbaite) from more evolved pegmatites (evolved euxenite-type and mixed (NYF + LCT) pegmatite) show a depletion in REE and Sc with progressive crystallization reflecting most likely the coeval precipitation of REE-rich minerals, especially monazite-(Ce), xenotime-(Y), samarskite- and aeschynite-group minerals. The Eu anomalies in tourmaline vary significantly from positive (up to Eu/Eu* similar to 16) to substantially negative ones and are related to the Eu contents in the melt and degree of its fractionation.
Related projects:

You are running an old browser version. We recommend updating your browser to its latest version.