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@article{1409741,
author = {Novák, Milan and Prokop, Jiří and Losos, Zdeněk and Macek, Ivo},
article_location = {Wien},
article_number = {4},
doi = {http://dx.doi.org/10.1007/s00710-017-0512-4},
keywords = {Tourmalines; granitic pegmatites; serpentinite; external contamination; solidus; subsolidus; Moldanubian Zone},
language = {eng},
issn = {0930-0708},
journal = {Mineralogy and Petrology},
title = {Tourmaline, an indicator of external Mg-contamination of granitic pegmatites from host serpentinite; examples from the Moldanubian Zone, Czech Republic},
volume = {111},
year = {2017}
}
TY - JOUR
ID - 1409741
AU - Novák, Milan - Prokop, Jiří - Losos, Zdeněk - Macek, Ivo
PY - 2017
TI - Tourmaline, an indicator of external Mg-contamination of granitic pegmatites from host serpentinite; examples from the Moldanubian Zone, Czech Republic
JF - Mineralogy and Petrology
VL - 111
IS - 4
SP - 625-641
EP - 625-641
PB - Springer Wien
SN - 09300708
KW - Tourmalines
KW - granitic pegmatites
KW - serpentinite
KW - external contamination
KW - solidus
KW - subsolidus
KW - Moldanubian Zone
N2 - Dominant primary solidus and minor subsolidus tourmalines from a variety of granitic pegmatites enclosed in serpentinites of the Moldanubian Zone, Czech Republic were examined, mainly by electron probe micro-analyser, to reveal the degree of external Mg(Ca)-contamination from their host rocks. The rocks include: (i) homogeneous to slightly heterogeneous nests of plagioclase-tourmaline rocks (group A) of anatectic or metasomatic origin, (ii) subhomogeneous to simply zoned barren pegmatite dikes (group B), and (iii) Li-bearing zoned pegmatite dikes of rare-element class (group C). The plagioclase-tourmaline rocks (group A) show spatial relation to pegmatites of the group B. Mostly black primary tourmalines (dravite, oxy-dravite, uvite, schorl, oxy-schorl, fluor-schorl) show extensive Mg- and Ca-contamination (group A), moderate Mg- and locally minor Ca-contamination (group B plus the locality Věžná I of the group C) and weak Mg-contamination of the tourmaline solely from outermost pegmatite units (group C); tourmalines from internal units of the pegmatites are typically Mg-free. Both Mg- and Ca-contamination events were very likely contemporaneous. The extent of contamination is higher in small and texturally simple plagioclase-tourmaline rocks (group A). Larger and more highly evolved Li-bearing pegmatites (group C) with zoned internal structure show a high degree of undercooling; consequently, rapid crystallization of outer zones with biotite and/or tourmaline depleted melt in almost all Mg and isolated the pegmatite body from further external contamination during solidus crystallisation. The granitic pegmatites (group B and group C) were open to the host serpentinite during early solidus crystallization immediately after emplacement of melt and then in early and/or late subsolidus crystallization (hydrothermal stage); in plagioclase-tourmaline rocks (group A) the system was likely continuously open to host serpentinite. This study affirms tourmaline as a very useful indicator of external contamination and elevated contents of Mg in tourmaline or in other minerals are the most reliable sign of external contamination in granitic rocks.
ER -
NOVÁK, Milan, Jiří PROKOP, Zdeněk LOSOS a Ivo MACEK. Tourmaline, an indicator of external Mg-contamination of granitic pegmatites from host serpentinite; examples from the Moldanubian Zone, Czech Republic. \textit{Mineralogy and Petrology}. Wien: Springer Wien, roč.~111, č.~4, s.~625-641. ISSN~0930-0708. doi:10.1007/s00710-017-0512-4. 2017.
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