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@article{2221505,
author = {Kubeš, Martin and Leichmann, Jaromír and Buriánek, David and Holá, Markéta and Navrátil, Petr and Scaillet, Stéphane and O'Sullivan, Paul},
article_number = {December},
doi = {http://dx.doi.org/10.1016/j.lithos.2022.106890},
keywords = {(ultra)potassic magmatism; mantle metasomatism; phlogopite-rich source; low-degree melting; Bohemian Massif},
language = {eng},
issn = {0024-4937},
journal = {Lithos},
title = {Highly evolved miaskitic syenites deciphering the origin and nature of enriched mantle source of ultrapotassic magmatism in the Variscan orogenic root (Bohemian Massif, Moldanubian Zone)},
url = {https://hal-insu.archives-ouvertes.fr/insu-03795335},
volume = {432-433},
year = {2022}
}
TY - JOUR
ID - 2221505
AU - Kubeš, Martin - Leichmann, Jaromír - Buriánek, David - Holá, Markéta - Navrátil, Petr - Scaillet, Stéphane - O'Sullivan, Paul
PY - 2022
TI - Highly evolved miaskitic syenites deciphering the origin and nature of enriched mantle source of ultrapotassic magmatism in the Variscan orogenic root (Bohemian Massif, Moldanubian Zone)
JF - Lithos
VL - 432-433
IS - December
SP - 1-23
EP - 1-23
PB - ELSEVIER
SN - 00244937
KW - (ultra)potassic magmatism
KW - mantle metasomatism
KW - phlogopite-rich source
KW - low-degree melting
KW - Bohemian Massif
UR - https://hal-insu.archives-ouvertes.fr/insu-03795335
N2 - A detailed study of alkali-rich syenites from the Gföhl unit of the Moldanubian Zone in the Bohemian Massif provides constraints on the exact origin and character of mantle source of ultrapotassic magmatism in the Variscan orogenic root in Central Europe. The syenites are characterized by highly alkaline composition (K2O 11.3–12.7 wt%; K2O/Na2O 6.8–7.5), crust-like isotopic signatures (87Sr/86Sr335 ~0.7116; εNd335 ≤ –7.8), and significant trace element enrichment (Th, U, Zr, Hf, LILE, LREE). They host an extraordinary amount of zircon (0.5–5 vol%) along with subordinate titanite and apatite, reflecting their miaskitic affinity. Mineral chemistry suggests that syenites formed through fractional crystallization and accumulation from highly reduced, metaluminous to slightly peraluminous mantle-derived alkaline magmas. Whole-rock geochemistry and Sr-Nd isotopes provide direct evidence that they were produced by partial melting of metasomatic phlogopite-bearing vein network (glimmerites) in the lithospheric mantle, generated by the interaction of (U)HP fluids/melts derived from deeply subducted crustal material (Moldanubian granulites) with wall-rock peridotites. Low-degree partial melting of pure vein component produced unusual geochemical signatures of miaskitic syenites, compared to the composition of common ultrapotassic rocks in the Bohemian Massif, reflecting relatively higher degrees of partial melting of mixed glimmerite-peridotite mantle source. The emplacement of alkali-rich syenites was almost contemporaneous with the mantle source enrichment and closely followed by initial fast cooling dated by 40Ar/39Ar amphibole-biotite ages ranging between 329.8 ± 1.6 and 331.4 ± 0.7 Ma, corresponding to rapid exhumation of the Variscan orogenic root in Central Europe. The U-Pb apatite age of 305.9 ± 5.3 Ma likely reflects further cooling to lower temperatures. The syenite emplacement was linked to the early impulse of ultrapotassic magmatism associated with the Andean-type subduction of the Saxothuringian domain beneath the Moldanubian block. The close temporal association of K-rich magmatism in the Saxothuringian and Moldanubian Zone is indicated by identical cooling ages of miaskitic syenites and other Saxonian ultrapotassic rocks, as revealed by 40Ar/39Ar dates around 330 Ma.
ER -
KUBEŠ, Martin, Jaromír LEICHMANN, David BURIÁNEK, Markéta HOLÁ, Petr NAVRÁTIL, Stéphane SCAILLET and Paul O'SULLIVAN. Highly evolved miaskitic syenites deciphering the origin and nature of enriched mantle source of ultrapotassic magmatism in the Variscan orogenic root (Bohemian Massif, Moldanubian Zone). \textit{Lithos}. ELSEVIER, 2022, 432-433, December, p.~1-23. ISSN~0024-4937. Available from: https://dx.doi.org/10.1016/j.lithos.2022.106890.
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