Geochemical characteristics of the high- and low-Ti basaltic rocks from the uplifted shoulder of the Ohře (Eger) Rift, Western Bohemia

Jaromír Ulrych, Emil Jelínek, Zdeněk Řanda, Felicity E. Lloyd, K. Balogh, Ernst Hegner, Jiří K. Novák

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

High-Ti melanephelinite (3.8-5.9wt% TiO2), medium-Ti (phono)tephrite (2.7-3.1wt% TiO2), and low-Ti olivine melanephelinite/basanite (1.9-2.3wt.% TiO2) are subordinate rock types in the central European Cenozoic Volcanic Province. A contrasting melanephelinite to (phono)tephrite series occurs in the Loučná-Oberwiesenthal Volcanic Centre (37-28Ma) and also as satellite volcanic bodies (26-12Ma) together with olivine melanephelinite/basanite (17-20Ma) on the southwestern periphery of the Krušné hory mountains (Erzgebirge). The volcanic rocks intrude the Variscan basement of the uplifted shoulder of the Ohře/Eger Rift in the Krušné hory mountains of the Bohemian Massif. Low Mg# (44-59) and Cr, Ni contents and enrichment of LILE, Zr, Hf, Nb, Ta, U, Th and LREE in the high-Ti melanephelinites contrast with the composition of primitive low-Ti olivine melanephelinites/basanites displaying high Mg# (63-74) and high contents of compatible elements. The high-Ti melanephelinites reveal a wide range in initial 87Sr/86Sr of ca. 0.7034-0.7038 and εNd of 2.4-4.9. The low-Ti melanephelinites show an overlapping range of initial 87Sr/86Sr of ca. 0.7035-0.7036 and εNd of 4.3-5.5. The large variation in initial 87Sr/86Sr ratios at similar εNd values in those rock types is interpreted as evidence for melting of metasomatized lithospheric mantle sources comprising K-bearing phases with radiogenic Sr. Modification of the olivine-free alkali basaltic magmas by differentiation or crustal contamination could give rise to the medium-Ti (phono) tephrites. The initial isotope ratios of all samples are consistent with HIMU-mantle sources and contributions from lithospheric mantle. The olivine-free melanephelinitic rocks often contain alkali pyroxenite-ijolite xenoliths with initial 87Sr/86Sr ratios of ca. 0.7036 and εNd of 3.0. We interpret these xenoliths as samples of an intra-crustal alkali complex derived from similar mantle sources as those for the basaltic volcanic rocks.

Original languageEnglish
Pages (from-to)319-333
Number of pages15
JournalChemie der Erde - Geochemistry
Volume70
Issue number4
DOIs
Publication statusPublished - 2010

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shoulders
olivine
volcanology
Rocks
rocks
Earth mantle
Alkalies
mantle source
Volcanic rocks
basanite
alkalies
rock
mountains
volcanic rock
Bearings (structural)
mountain
pyroxenite
crustal contamination
isotope ratios
basements

Keywords

  • Bohemian Massif
  • Cenozoic volcanism
  • Eger Rift
  • Erzgebirge
  • Geochemistry
  • High-Ti basaltic rocks
  • Krušné hory Mts.
  • Ohře Rift

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

Cite this

Geochemical characteristics of the high- and low-Ti basaltic rocks from the uplifted shoulder of the Ohře (Eger) Rift, Western Bohemia. / Ulrych, Jaromír; Jelínek, Emil; Řanda, Zdeněk; Lloyd, Felicity E.; Balogh, K.; Hegner, Ernst; Novák, Jiří K.

In: Chemie der Erde - Geochemistry, Vol. 70, No. 4, 2010, p. 319-333.

Research output: Contribution to journalArticle

Ulrych, Jaromír ; Jelínek, Emil ; Řanda, Zdeněk ; Lloyd, Felicity E. ; Balogh, K. ; Hegner, Ernst ; Novák, Jiří K. / Geochemical characteristics of the high- and low-Ti basaltic rocks from the uplifted shoulder of the Ohře (Eger) Rift, Western Bohemia. In: Chemie der Erde - Geochemistry. 2010 ; Vol. 70, No. 4. pp. 319-333.
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T1 - Geochemical characteristics of the high- and low-Ti basaltic rocks from the uplifted shoulder of the Ohře (Eger) Rift, Western Bohemia

AU - Ulrych, Jaromír

AU - Jelínek, Emil

AU - Řanda, Zdeněk

AU - Lloyd, Felicity E.

AU - Balogh, K.

AU - Hegner, Ernst

AU - Novák, Jiří K.

PY - 2010

Y1 - 2010

N2 - High-Ti melanephelinite (3.8-5.9wt% TiO2), medium-Ti (phono)tephrite (2.7-3.1wt% TiO2), and low-Ti olivine melanephelinite/basanite (1.9-2.3wt.% TiO2) are subordinate rock types in the central European Cenozoic Volcanic Province. A contrasting melanephelinite to (phono)tephrite series occurs in the Loučná-Oberwiesenthal Volcanic Centre (37-28Ma) and also as satellite volcanic bodies (26-12Ma) together with olivine melanephelinite/basanite (17-20Ma) on the southwestern periphery of the Krušné hory mountains (Erzgebirge). The volcanic rocks intrude the Variscan basement of the uplifted shoulder of the Ohře/Eger Rift in the Krušné hory mountains of the Bohemian Massif. Low Mg# (44-59) and Cr, Ni contents and enrichment of LILE, Zr, Hf, Nb, Ta, U, Th and LREE in the high-Ti melanephelinites contrast with the composition of primitive low-Ti olivine melanephelinites/basanites displaying high Mg# (63-74) and high contents of compatible elements. The high-Ti melanephelinites reveal a wide range in initial 87Sr/86Sr of ca. 0.7034-0.7038 and εNd of 2.4-4.9. The low-Ti melanephelinites show an overlapping range of initial 87Sr/86Sr of ca. 0.7035-0.7036 and εNd of 4.3-5.5. The large variation in initial 87Sr/86Sr ratios at similar εNd values in those rock types is interpreted as evidence for melting of metasomatized lithospheric mantle sources comprising K-bearing phases with radiogenic Sr. Modification of the olivine-free alkali basaltic magmas by differentiation or crustal contamination could give rise to the medium-Ti (phono) tephrites. The initial isotope ratios of all samples are consistent with HIMU-mantle sources and contributions from lithospheric mantle. The olivine-free melanephelinitic rocks often contain alkali pyroxenite-ijolite xenoliths with initial 87Sr/86Sr ratios of ca. 0.7036 and εNd of 3.0. We interpret these xenoliths as samples of an intra-crustal alkali complex derived from similar mantle sources as those for the basaltic volcanic rocks.

AB - High-Ti melanephelinite (3.8-5.9wt% TiO2), medium-Ti (phono)tephrite (2.7-3.1wt% TiO2), and low-Ti olivine melanephelinite/basanite (1.9-2.3wt.% TiO2) are subordinate rock types in the central European Cenozoic Volcanic Province. A contrasting melanephelinite to (phono)tephrite series occurs in the Loučná-Oberwiesenthal Volcanic Centre (37-28Ma) and also as satellite volcanic bodies (26-12Ma) together with olivine melanephelinite/basanite (17-20Ma) on the southwestern periphery of the Krušné hory mountains (Erzgebirge). The volcanic rocks intrude the Variscan basement of the uplifted shoulder of the Ohře/Eger Rift in the Krušné hory mountains of the Bohemian Massif. Low Mg# (44-59) and Cr, Ni contents and enrichment of LILE, Zr, Hf, Nb, Ta, U, Th and LREE in the high-Ti melanephelinites contrast with the composition of primitive low-Ti olivine melanephelinites/basanites displaying high Mg# (63-74) and high contents of compatible elements. The high-Ti melanephelinites reveal a wide range in initial 87Sr/86Sr of ca. 0.7034-0.7038 and εNd of 2.4-4.9. The low-Ti melanephelinites show an overlapping range of initial 87Sr/86Sr of ca. 0.7035-0.7036 and εNd of 4.3-5.5. The large variation in initial 87Sr/86Sr ratios at similar εNd values in those rock types is interpreted as evidence for melting of metasomatized lithospheric mantle sources comprising K-bearing phases with radiogenic Sr. Modification of the olivine-free alkali basaltic magmas by differentiation or crustal contamination could give rise to the medium-Ti (phono) tephrites. The initial isotope ratios of all samples are consistent with HIMU-mantle sources and contributions from lithospheric mantle. The olivine-free melanephelinitic rocks often contain alkali pyroxenite-ijolite xenoliths with initial 87Sr/86Sr ratios of ca. 0.7036 and εNd of 3.0. We interpret these xenoliths as samples of an intra-crustal alkali complex derived from similar mantle sources as those for the basaltic volcanic rocks.

KW - Bohemian Massif

KW - Cenozoic volcanism

KW - Eger Rift

KW - Erzgebirge

KW - Geochemistry

KW - High-Ti basaltic rocks

KW - Krušné hory Mts.

KW - Ohře Rift

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