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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, 2017, roč.~111, č.~4, s.~625-641. ISSN~0930-0708. Dostupné z: https://dx.doi.org/10.1007/s00710-017-0512-4.
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