Petrogenesis of alkali pyroxenite and ijolite xenoliths from the Tertiary Loučná-Oberwiesenthal Volcanic Centre, Bohemian Massif in the light of new mineralogical, geochemical, and isotopic data

J. Ulrych, F. E. Lloyd, K. Balogh, E. Hegner, A. Langrová, M. Lang, J. K. Novák, Z. Řanda

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

Alkali pyroxenite and ijolite xenoliths occur in ca. 37-30 Ma old nephelinite of the Loučná-Oberwiesenthal Volcanic Centre. The latter is located on the uplifted shoulder of the Ohře/Eger Rift within the Variscan basement of central Europe. The alkali pyroxenites and transitional xenoliths are abundant whereas ijolite xenoliths are rare. The host nephelinite is chemically evolved (Mg# 47-46), and the entrained alkali clinopyroxenite xenoliths (Mg# 64-47) and transitional to ijolite xenoliths (Mg# 69-25) show a range of compositions from little to highly evolved. The alkali pyroxenite xenoliths probably represent fragments of an intracrustal, possibly layered alkaline complex, overprinted by a late-magmatic pegmatoid phase of ijolite composition. This late stage metasomatic process may account for a spectrum of rocks ranging from alkali pyroxenite to ijolite. Initial ε Nd values of +2.3 in clinopyroxene samples from the host nephelinite and +3.1 to +3.0 in clinopyroxene from the xenoliths indicate similar, yet different sources. The initial 87Sr/86Sr ratios of 0.70361 to 0.70365 and inital εNd values of +3.0 and +3.1 for the alkali pyroxenite xenoliths are consistent with mantle sources of HIMU-affinity. A similar source may be inferred from the isotopic composition of the host nephelinite yielding an initial 87Sr/86Sr of 0.70368 and initial εNd value of +2.3.

Original languageEnglish
Pages (from-to)57-79
Number of pages23
JournalNeues Jahrbuch fur Mineralogie, Abhandlungen
Volume182
Issue number1
DOIs
Publication statusPublished - 2005

Fingerprint

nephelinite
pyroxenite
Alkalies
petrogenesis
clinopyroxene
Chemical analysis
Hercynian orogeny
mantle source
isotopic composition
Rocks
rock

Keywords

  • Alkali pyroxenite
  • Bohemian Massif
  • Ijolite
  • Krušné hory/Erzgebirge Mts.
  • Ohře/Eger Rift
  • Tertiary European volcanism
  • Xenoliths

ASJC Scopus subject areas

  • Geochemistry and Petrology

Cite this

Petrogenesis of alkali pyroxenite and ijolite xenoliths from the Tertiary Loučná-Oberwiesenthal Volcanic Centre, Bohemian Massif in the light of new mineralogical, geochemical, and isotopic data. / Ulrych, J.; Lloyd, F. E.; Balogh, K.; Hegner, E.; Langrová, A.; Lang, M.; Novák, J. K.; Řanda, Z.

In: Neues Jahrbuch fur Mineralogie, Abhandlungen, Vol. 182, No. 1, 2005, p. 57-79.

Research output: Contribution to journalArticle

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abstract = "Alkali pyroxenite and ijolite xenoliths occur in ca. 37-30 Ma old nephelinite of the Loučn{\'a}-Oberwiesenthal Volcanic Centre. The latter is located on the uplifted shoulder of the Ohře/Eger Rift within the Variscan basement of central Europe. The alkali pyroxenites and transitional xenoliths are abundant whereas ijolite xenoliths are rare. The host nephelinite is chemically evolved (Mg# 47-46), and the entrained alkali clinopyroxenite xenoliths (Mg# 64-47) and transitional to ijolite xenoliths (Mg# 69-25) show a range of compositions from little to highly evolved. The alkali pyroxenite xenoliths probably represent fragments of an intracrustal, possibly layered alkaline complex, overprinted by a late-magmatic pegmatoid phase of ijolite composition. This late stage metasomatic process may account for a spectrum of rocks ranging from alkali pyroxenite to ijolite. Initial ε Nd values of +2.3 in clinopyroxene samples from the host nephelinite and +3.1 to +3.0 in clinopyroxene from the xenoliths indicate similar, yet different sources. The initial 87Sr/86Sr ratios of 0.70361 to 0.70365 and inital εNd values of +3.0 and +3.1 for the alkali pyroxenite xenoliths are consistent with mantle sources of HIMU-affinity. A similar source may be inferred from the isotopic composition of the host nephelinite yielding an initial 87Sr/86Sr of 0.70368 and initial εNd value of +2.3.",
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AU - Ulrych, J.

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AB - Alkali pyroxenite and ijolite xenoliths occur in ca. 37-30 Ma old nephelinite of the Loučná-Oberwiesenthal Volcanic Centre. The latter is located on the uplifted shoulder of the Ohře/Eger Rift within the Variscan basement of central Europe. The alkali pyroxenites and transitional xenoliths are abundant whereas ijolite xenoliths are rare. The host nephelinite is chemically evolved (Mg# 47-46), and the entrained alkali clinopyroxenite xenoliths (Mg# 64-47) and transitional to ijolite xenoliths (Mg# 69-25) show a range of compositions from little to highly evolved. The alkali pyroxenite xenoliths probably represent fragments of an intracrustal, possibly layered alkaline complex, overprinted by a late-magmatic pegmatoid phase of ijolite composition. This late stage metasomatic process may account for a spectrum of rocks ranging from alkali pyroxenite to ijolite. Initial ε Nd values of +2.3 in clinopyroxene samples from the host nephelinite and +3.1 to +3.0 in clinopyroxene from the xenoliths indicate similar, yet different sources. The initial 87Sr/86Sr ratios of 0.70361 to 0.70365 and inital εNd values of +3.0 and +3.1 for the alkali pyroxenite xenoliths are consistent with mantle sources of HIMU-affinity. A similar source may be inferred from the isotopic composition of the host nephelinite yielding an initial 87Sr/86Sr of 0.70368 and initial εNd value of +2.3.

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