J 2022

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)

KUBEŠ, Martin, Jaromír LEICHMANN, David BURIÁNEK, Markéta HOLÁ, Petr NAVRÁTIL et. al.

Základní údaje

Originální název

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)

Autoři

KUBEŠ, Martin (203 Česká republika, garant, domácí), Jaromír LEICHMANN (203 Česká republika, domácí), David BURIÁNEK (203 Česká republika, domácí), Markéta HOLÁ (203 Česká republika, domácí), Petr NAVRÁTIL (203 Česká republika), Stéphane SCAILLET (250 Francie) a Paul O'SULLIVAN (840 Spojené státy)

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

Impakt faktor

Impact factor: 3.500

Kód RIV

RIV/00216224:14310/22:00126791

Organizační jednotka

Přírodovědecká fakulta

UT WoS

000870985300004

Klíčová slova anglicky

(ultra)potassic magmatism; mantle metasomatism; phlogopite-rich source; low-degree melting; Bohemian Massif

Štítky

Příznaky

Mezinárodní význam, Recenzováno
Změněno: 8. 3. 2023 10:41, Mgr. Martin Kubeš, Ph.D.

Anotace

V originále

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.

Návaznosti

EF16_026/0008459, projekt VaV
Název: Dlouhodobý výzkum geochemických bariér pro ukládání jaderného odpadu