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)
The result's identifiers
Result code in IS VaVaI
<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00025798%3A_____%2F22%3A00000039" target="_blank" >RIV/00025798:_____/22:00000039 - isvavai.cz</a>
Alternative codes found
RIV/00216224:14310/22:00126791
Result on the web
<a href="https://www.sciencedirect.com/science/article/pii/S0024493722002997" target="_blank" >https://www.sciencedirect.com/science/article/pii/S0024493722002997</a>
DOI - Digital Object Identifier
<a href="http://dx.doi.org/10.1016/j.lithos.2022.106890" target="_blank" >10.1016/j.lithos.2022.106890</a>
Alternative languages
Result language
angličtina
Original language name
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)
Original language description
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 wtpercent; K2O/Na2O 6.8–7.5), crust-like isotopic signatures (87Sr/86Sr335 ∼ 0.7116; epsilonNd335 ≤ −7.8), and significant trace element enrichment (Th, U, Zr, Hf, LILE, LREE). They host an extraordinary amount of zircon (0.5–5 volpercent) 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.
Czech name
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Czech description
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Classification
Type
J<sub>imp</sub> - Article in a specialist periodical, which is included in the Web of Science database
CEP classification
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OECD FORD branch
10505 - Geology
Result continuities
Project
<a href="/en/project/EF16_026%2F0008459" target="_blank" >EF16_026/0008459: Long-term research of geochemical barriers for nuclear waste disposal</a><br>
Continuities
I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace
Others
Publication year
2022
Confidentiality
S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů
Data specific for result type
Name of the periodical
Lithos
ISSN
0024-4937
e-ISSN
—
Volume of the periodical
432–433
Issue of the periodical within the volume
December : 106890
Country of publishing house
NL - THE KINGDOM OF THE NETHERLANDS
Number of pages
23
Pages from-to
nestránkováno
UT code for WoS article
000870985300004
EID of the result in the Scopus database
2-s2.0-85139027674