Diversity of origin and geodynamic evolution of the mantle
beneath the Variscan Orogen indicating rapid exhumation within
subduction-related mélange (Moldanubian Zone, Bohemian Massif)

J 2022

Diversity of origin and geodynamic evolution of the mantle beneath the Variscan Orogen indicating rapid exhumation within subduction-related mélange (Moldanubian Zone, Bohemian Massif)

KUBEŠ, Martin, Jaromír LEICHMANN, Jana KOTKOVÁ, Renata ČOPJAKOVÁ, Markéta HOLÁ et. al.

Základní údaje

Originální název

Diversity of origin and geodynamic evolution of the mantle beneath the Variscan Orogen indicating rapid exhumation within subduction-related mélange (Moldanubian Zone, Bohemian Massif)

Autoři

KUBEŠ, Martin (203 Česká republika, garant, domácí), Jaromír LEICHMANN (203 Česká republika, domácí), Jana KOTKOVÁ (203 Česká republika, domácí), Renata ČOPJAKOVÁ (203 Česká republika, domácí), Markéta HOLÁ (203 Česká republika, domácí) a Jiří SLÁMA (203 Česká republika)

Vydání

Lithos, Elsevier, 2022, 0024-4937

Další údaje

Jazyk

angličtina

Typ výsledku

Článek v odborném periodiku

Obor

10505 Geology

Stát vydavatele

Nizozemské království

Utajení

není předmětem státního či obchodního tajemství

Odkazy

URL

Impakt faktor

Impact factor: 3.500

Kód RIV

RIV/00216224:14310/22:00125796

Organizační jednotka

Přírodovědecká fakulta

DOI

http://dx.doi.org/10.1016/j.lithos.2022.106726

UT WoS

000800346800005

Klíčová slova anglicky

Ultrabasic rocks; Subduction zone; Melt-peridotite interaction; Mantle refertilization; Cryptic metasomatism; Bohemian Massif

Štítky

rivok

Příznaky

Mezinárodní význam, Recenzováno

Změněno: 8. 3. 2023 10:42, Mgr. Martin Kubeš, Ph.D.

Anotace

V originále

A variable assemblage of ultrabasic rocks along with minor eclogites investigated on a small area of a few km2 (Gföhl unit, Moldanubian Zone of the Bohemian Massif) reflects incorporation of contrasting mantle domains within a subduction-related tectonic mélange during the Variscan orogeny. Based on mineral composition, whole-rock chemistry, isotopic signatures, and pressure-temperature (P–T) estimates, four principal lithological types have been distinguished (1) spinel harzburgite (2) garnet lherzolite (3) spinel websterite and (4) eclogite. Spinel harzburgite, exclusively associated with HT migmatized gneisses, corresponds to the refractory oceanic lithosphere, as demonstrated by whole-rock composition (low Al2O3, CaO), chemistry of spinel (Cr# <0.4) and Al-rich pyroxene (Al2O3 up to 9 wt%). By contrast, garnet lherzolite, predominantly enclosed in HP felsic granulite, represents a fragment of the subcontinental mantle wedge, considering the strong fertile character (high Al2O3, TiO2, Yb) and spinel chemistry (Cr# >0.5). Websterites likely represent products of decompression partial melting of the asthenospheric mantle with a variable input of crustal component, whereas eclogites correspond to HP crystal cumulates from partial melts migrating through the Variscan mantle wedge. Both peridotite protoliths experienced various degrees of secondary refertilization, recorded as a cryptic metasomatic overprint, due to interaction with subduction-related silicate melts, from which numerous websterite and rare eclogite layers crystallized. The secondary mantle refertilization via melt-peridotite reaction is well-documented by decreasing bulk Mg# along with MgO/SiO2, elevated Al2O3/SiO2, TiO2 and FeOtot contents, and isotopic composition (87Sr/86Sr338 ~ 0.7051). Moreover, the positive correlation between highly fluid-immobile incompatible trace elements (e.g. Ti, Sc, V, Zr, Yb) and distribution of REE and Li is consistent with the melt refertilization trend. During the Variscan subduction, lherzolite experienced UHP conditions (42 kbar, 1100 °C). The presence of Cr-spinel relics preserved in garnet suggests that lherzolite was dragged from the shallow mantle wedge to deeper levels of the subduction zone, probably along with the underlying subducting oceanic plate involving refractory harzburgite. This deep burial during the Variscan subduction was closely followed by rapid exhumation dated by the Lu-Hf age of 338.4 ± 6.3 Ma, corresponding to re-equilibration at lower crustal levels or possibly at greater depths, closer to peak P conditions. Decompression-induced partial melting of upwelling asthenosphere with a contribution of crustal material resulted in derivation of primitive to mildly evolved transient melts (87Sr/86Sr338 ~ 0.7049–0.7062) represented by websterites, percolating through and metasomatizing wall-rock peridotites. The rapid exhumation and following juxtaposition of genetically diverse yet closely associated ultrabasic rocks provide a unique insight into the history of Earth mantle, evolving during the formation of the Variscan orogenic belt in Central Europe within contrasting geological settings, from ocean ridge environment to great depths of subduction zone.

Návaznosti

EF16_026/0008459, projekt VaV

Název: Dlouhodobý výzkum geochemických bariér pro ukládání jaderného odpadu

Citovat

KUBEŠ, Martin, Jaromír LEICHMANN, Jana KOTKOVÁ, Renata ČOPJAKOVÁ, Markéta HOLÁ a Jiří SLÁMA. Diversity of origin and geodynamic evolution of the mantle beneath the Variscan Orogen indicating rapid exhumation within subduction-related mélange (Moldanubian Zone, Bohemian Massif). Lithos. Elsevier, 2022, roč. 422-423, August, s. 1-22. ISSN 0024-4937. Dostupné z: https://dx.doi.org/10.1016/j.lithos.2022.106726.

@article{1852501,
   author = {Kubeš, Martin and Leichmann, Jaromír and Kotková, Jana and Čopjaková, Renata and Holá, Markéta and Sláma, Jiří},
   article_number = {August},
   doi = {http://dx.doi.org/10.1016/j.lithos.2022.106726},
   keywords = {Ultrabasic rocks; Subduction zone; Melt-peridotite interaction; Mantle refertilization; Cryptic metasomatism; Bohemian Massif},
   language = {eng},
   issn = {0024-4937},
   journal = {Lithos},
   title = {Diversity of origin and geodynamic evolution of the mantle beneath the Variscan Orogen indicating rapid exhumation within subduction-related mélange (Moldanubian Zone, Bohemian Massif)},
   url = {https://www.sciencedirect.com/science/article/pii/S0024493722001359},
   volume = {422-423},
   year = {2022}
}

TY  - JOUR
ID  - 1852501
AU  - Kubeš, Martin - Leichmann, Jaromír - Kotková, Jana - Čopjaková, Renata - Holá, Markéta - Sláma, Jiří
PY  - 2022
TI  - Diversity of origin and geodynamic evolution of the mantle beneath the Variscan Orogen indicating rapid exhumation within subduction-related mélange (Moldanubian Zone, Bohemian Massif)
JF  - Lithos
VL  - 422-423
IS  - August
SP  - 1-22
EP  - 1-22
PB  - Elsevier
SN  - 00244937
KW  - Ultrabasic rocks
KW  - Subduction zone
KW  - Melt-peridotite interaction
KW  - Mantle refertilization
KW  - Cryptic metasomatism
KW  - Bohemian Massif
UR  - https://www.sciencedirect.com/science/article/pii/S0024493722001359
N2  - A variable assemblage of ultrabasic rocks along with minor eclogites investigated on a small area of a few km2 (Gföhl unit, Moldanubian Zone of the Bohemian Massif) reflects incorporation of contrasting mantle domains within a subduction-related tectonic mélange during the Variscan orogeny. Based on mineral composition, whole-rock chemistry, isotopic signatures, and pressure-temperature (P–T) estimates, four principal lithological types have been distinguished (1) spinel harzburgite (2) garnet lherzolite (3) spinel websterite and (4) eclogite. Spinel harzburgite, exclusively associated with HT migmatized gneisses, corresponds to the refractory oceanic lithosphere, as demonstrated by whole-rock composition (low Al2O3, CaO), chemistry of spinel (Cr# <0.4) and Al-rich pyroxene (Al2O3 up to 9 wt%). By contrast, garnet lherzolite, predominantly enclosed in HP felsic granulite, represents a fragment of the subcontinental mantle wedge, considering the strong fertile character (high Al2O3, TiO2, Yb) and spinel chemistry (Cr# >0.5). Websterites likely represent products of decompression partial melting of the asthenospheric mantle with a variable input of crustal component, whereas eclogites correspond to HP crystal cumulates from partial melts migrating through the Variscan mantle wedge. Both peridotite protoliths experienced various degrees of secondary refertilization, recorded as a cryptic metasomatic overprint, due to interaction with subduction-related silicate melts, from which numerous websterite and rare eclogite layers crystallized. The secondary mantle refertilization via melt-peridotite reaction is well-documented by decreasing bulk Mg# along with MgO/SiO2, elevated Al2O3/SiO2, TiO2 and FeOtot contents, and isotopic composition (87Sr/86Sr338 ~ 0.7051). Moreover, the positive correlation between highly fluid-immobile incompatible trace elements (e.g. Ti, Sc, V, Zr, Yb) and distribution of REE and Li is consistent with the melt refertilization trend. During the Variscan subduction, lherzolite experienced UHP conditions (42 kbar, 1100 °C). The presence of Cr-spinel relics preserved in garnet suggests that lherzolite was dragged from the shallow mantle wedge to deeper levels of the subduction zone, probably along with the underlying subducting oceanic plate involving refractory harzburgite. This deep burial during the Variscan subduction was closely followed by rapid exhumation dated by the Lu-Hf age of 338.4 ± 6.3 Ma, corresponding to re-equilibration at lower crustal levels or possibly at greater depths, closer to peak P conditions. Decompression-induced partial melting of upwelling asthenosphere with a contribution of crustal material resulted in derivation of primitive to mildly evolved transient melts (87Sr/86Sr338 ~ 0.7049–0.7062) represented by websterites, percolating through and metasomatizing wall-rock peridotites. The rapid exhumation and following juxtaposition of genetically diverse yet closely associated ultrabasic rocks provide a unique insight into the history of Earth mantle, evolving during the formation of the Variscan orogenic belt in Central Europe within contrasting geological settings, from ocean ridge environment to great depths of subduction zone.
ER  -

KUBEŠ, Martin, Jaromír LEICHMANN, Jana KOTKOVÁ, Renata ČOPJAKOVÁ, Markéta HOLÁ a Jiří SLÁMA. Diversity of origin and geodynamic evolution of the mantle beneath the Variscan Orogen indicating rapid exhumation within subduction-related mélange (Moldanubian Zone, Bohemian Massif). \textit{Lithos}. Elsevier, 2022, roč.~422-423, August, s.~1-22. ISSN~0024-4937. Dostupné z: https://dx.doi.org/10.1016/j.lithos.2022.106726.

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