Sc- and REE-rich tourmaline replaced by Sc-rich REE-bearing epidote-group mineral from the mixed (NYF plus LCT) Kracovice pegmatite (Moldanubian Zone, Czech Republic)

Investor logo
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 CEMPÍREK Jan

Year of publication 2015
Type Article in Periodical
Magazine / Source American Mineralogist
MU Faculty or unit

Faculty of Science

Citation
Field Geology and mineralogy
Keywords Schorl; fluor-elbaite; tourmaline replacement; Sc-rich REE-bearing epidote-group mineral; granitic pegmatite; Bohemian Massif
Description Primary black thick-prismatic Al-rich schorl to rare fluor-schorl (TurP1), locally overgrown by brownish-green Li-rich fluor-schorl to fluor-elbaite (TurP2) from the Kracovice pegmatite (mixed NYF+LCT signature), was partly replaced by secondary Li-rich fluor-schorl to fluor-elbaite (TurS) plus the assemblage REE-bearing epidote-group mineral + chamosite. Primary Al-rich schorl (TurP1) shows high and variable contents of Sc (33-364 ppm) and Y+REE (40-458 ppm) with steep, LREE-enriched REE pattern. Overgrowing (TurP2) and replacing (TurS) Li-rich fluor-schorl to fluor-elbaite is typically depleted in Sc (21-60 ppm) and Y+REE (3-47 ppm) with well-developed tetrad effect in the first (La-Nd) and the second (Sm-Gd) tetrads. Scandium- and REE-rich black tourmaline (TurP1) crystallized earlier from the melt, whereas crystallization of primary Li-rich fluor-schorl to fluor-elbaite (TurP2) most likely took place during late magmatic to early hydrothermal conditions. Both the secondary Li-rich fluor-schorl to fluor-elbaite (TurS) and the unusual assemblage of REE-bearing epidote-group mineral + chamosite are likely coeval products of subsolidus reactions of the magmatic Al-rich schorl (TurP1) with evolved REE-poor, Li,F-rich, alkaline pegmatite-derived fluids. Well-crystalline REE-bearing epidote-group mineral (Y+REE = 0.42-0.60 apfu) confirmed by Raman spectroscopy has a steep, LREE-rich chondrite-normalized REE pattern with significant negative Eu anomaly and shows variable and high contents of Sc (<= 3.3 wt% Sc2O3) and Sn (<= 1.0 wt% SnO2). Substitution ScAl-1, and minor vacancy in the octahedral sites are suggested in the REE-bearing epidote-group mineral.
Related projects:

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