Tourmaline, an indicator of external Mg-contamination of
granitic pegmatites from host serpentinite; examples from the
Moldanubian Zone, Czech Republic

J 2017

Tourmaline, an indicator of external Mg-contamination of granitic pegmatites from host serpentinite; examples from the Moldanubian Zone, Czech Republic

NOVÁK, Milan, Jiří PROKOP, Zdeněk LOSOS and Ivo MACEK

Basic information

Original name

Tourmaline, an indicator of external Mg-contamination of granitic pegmatites from host serpentinite; examples from the Moldanubian Zone, Czech Republic

Authors

NOVÁK, Milan (203 Czech Republic, belonging to the institution), Jiří PROKOP (203 Czech Republic, belonging to the institution), Zdeněk LOSOS (203 Czech Republic, guarantor, belonging to the institution) and Ivo MACEK (203 Czech Republic, belonging to the institution)

Edition

Mineralogy and Petrology, Wien, Springer Wien, 2017, 0930-0708

Other information

Language

English

Type of outcome

Článek v odborném periodiku

Field of Study

10504 Mineralogy

Country of publisher

Austria

Confidentiality degree

není předmětem státního či obchodního tajemství

Impact factor

Impact factor: 1.664

RIV identification code

RIV/00216224:14310/17:00095537

Organization unit

Faculty of Science

DOI

http://dx.doi.org/10.1007/s00710-017-0512-4

UT WoS

000407743900013

Keywords in English

Tourmalines; granitic pegmatites; serpentinite; external contamination; solidus; subsolidus; Moldanubian Zone

Abstract

V originále

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.

Links

GA14-13347S, research and development project

Name: Variabilita lehkých prvků (Li, Be, B) ve vybraných horninotvorných a akcesorických minerálech z felsických magmatických a metamorfovaných hornin

Investor: Czech Science Foundation

GA17-17276S, research and development project

Name: Turmalín - indikátor geologických procesů

Investor: Czech Science Foundation

Citovat

NOVÁK, Milan, Jiří PROKOP, Zdeněk LOSOS and Ivo MACEK. Tourmaline, an indicator of external Mg-contamination of granitic pegmatites from host serpentinite; examples from the Moldanubian Zone, Czech Republic. Mineralogy and Petrology. Wien: Springer Wien, 2017, vol. 111, No 4, p. 625-641. ISSN 0930-0708. Available from: https://dx.doi.org/10.1007/s00710-017-0512-4.

@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 and 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, vol.~111, No~4, p.~625-641. ISSN~0930-0708. Available from: https://dx.doi.org/10.1007/s00710-017-0512-4.

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