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@article{1705156,
author = {Zachař, Adam and Novák, Milan and Škoda, Radek},
article_location = {Praha},
article_number = {3},
doi = {http://dx.doi.org/10.3190/jgeosci.307},
keywords = {beryl; phenakite; helvite-danalite; milarite- and gadolinite-group minerals; bohseite-bavenite; NYF pegmatites; Trebic Pluton},
language = {eng},
issn = {1802-6222},
journal = {Journal of Geosciences},
title = {Beryllium minerals as monitors of geochemical evolution from magmatic to hydrothermal stage; examples from NYF pegmatites of the Třebíč Pluton, Czech Republic},
url = {http://dx.doi.org/10.3190/jgeosci.307},
volume = {65},
year = {2020}
}
TY - JOUR
ID - 1705156
AU - Zachař, Adam - Novák, Milan - Škoda, Radek
PY - 2020
TI - Beryllium minerals as monitors of geochemical evolution from magmatic to hydrothermal stage; examples from NYF pegmatites of the Třebíč Pluton, Czech Republic
JF - Journal of Geosciences
VL - 65
IS - 3
SP - 153-172
EP - 153-172
PB - Czech Geological Survey
SN - 18026222
KW - beryl
KW - phenakite
KW - helvite-danalite
KW - milarite- and gadolinite-group minerals
KW - bohseite-bavenite
KW - NYF pegmatites
KW - Trebic Pluton
UR - http://dx.doi.org/10.3190/jgeosci.307
L2 - http://dx.doi.org/10.3190/jgeosci.307
N2 - Mineral assemblages of primary and secondary Be-minerals were examined in intraplutonic euxenite-type NYF pegmatites of the Trebic Pluton, Moldanubian Zone occurring between Trebic and Vladislav south of the Trebic fault. Primary magmatic Be-minerals crystallized mainly in massive pegmatite (paragenetic type I) including common beryl I, helvite-danalite I, and a rare phenakite I. Rare primary hydrothermal beryl II and phenakite II occur in miarolitic pockets (paragenetic type II). Secondary hydrothermal Be-minerals replaced primary precursors or filled fractures and secondary cavities, or they are associated with "adularia" and quart. (paragenetic type III). They include minerals of bohseite-bavenite series, less abundant beryl III, bazzite III, helvite-danalite III , milarite-agalchanovite-(Y) III, phenakite III, and datolite-hingganite-(Y) III. Chemical composition of the individual minerals is characterized by elevated contents of Na, Cs, Mg, Fe, Sc in beryl I and II; Na, Ca, Mg, Fe, Al in bazzite III; REE in milarite-agakhanovite-(Y) III; variations in Fe/Mn in helvite-danalite and high variation of Al in bohseite-bavenite series. Replacement reactions of primary Be-minerals are commonly complex and the sequence of crystallization of secondary Be-minerals is not defined; minerals of bohseite-bavenite series are mostly the latest. Beryl usually occurs in pegmatites with rare tourmaline, whereas helvite-danalite bearing pegmatites are tourmaline-rich. Abundant tourmaline in pegmatites with helvite-danalite and its scarcity in beryl-bearing pegmatites indicate that early tourmaline crystallization affected activity of Al in the parental medium and thus may have controlled formation of primary Be-minerals (beryl - higher Al, helvite-danalite - lower Al) which crystallized later. Secondary Be-minerals with dominant minerals of bohseite-bavenite series and milarite suggest high activity of Ca in fluids. Variations in chemical composition (Al contents) of bohseite-bavenite series were controlled by the chemical composition of the precursor. High variability of primary magmatic Be-minerals within a single pegmatite district is exceptional and it is constrained by variable activities of Si and mainly Al, divalent cations - Ca, Mn, Fe, Zn and Mg, trivalent cations - REEs, Sc, and B, S and f(O2) in the individual pegmatites.
ER -
ZACHAŘ, Adam, Milan NOVÁK a Radek ŠKODA. Beryllium minerals as monitors of geochemical evolution from magmatic to hydrothermal stage; examples from NYF pegmatites of the Třebíč Pluton, Czech Republic. \textit{Journal of Geosciences}. Praha: Czech Geological Survey, roč.~65, č.~3, s.~153-172. ISSN~1802-6222. doi:10.3190/jgeosci.307. 2020.
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