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Mineralogy and Petrology

, Volume 43, Issue 4, pp 275–292 | Cite as

Pyroxene chemistry and evolution of alkali basaltic rocks from Burgenland and Styria, Austria

  • G. Dobosi
  • R. Schultz-Güttler
  • G. Kurat
  • A. Kracher
Article

Summary

The mineral chemistry of several Pliocene alkali basaltic rocks from Burgenland and Styria (Eastern Austria) have been investigated in order to determine the evolution path of the basalt magmas prior to eruption. With their wide range of substitutions, clinopyroxenes provide the best records of the evolution history of rocks. Pyroxene phenocrysts of the investigated basalts show both concentric and sector zoning. The investigation of sector zoned crystals shows, that not only Ti, Al and Fe contents are different in different sectors but there can be significant differences also in their Cr content. This fact apparently suggests that the distribution of Cr between clinopyroxene and melt could be influenced by crystallization kinetics.

The depth of crystallization and differentiation of the basalts can be estimated from Ti and Al contents of clinopyroxene phenocrysts. From a combination of data on clinopyroxene composition, compatible trace element contents and mg-values of the rocks, it is concluded, that the alkali basalts of Pauliberg and Steinberg underwent slight olivine and clinopyroxene fractionation in shallow magma chambers prior to eruption, while the nephelinite of Stradnerkogel evolved mainly through clinopyroxene fractionation under high pressure conditions, probably in the upper mantle.

Keywords

Olivine Pliocene Magma Chamber Basalt Magma Trace Element Content 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Chemie der Pyroxene und Entwicklung von Alkalibasalten aus dem Burgenland und der Steiermark, Österreich

Zusammenfassung

Einige pliozäne alkalibasaltische Gesteine aus dem Burgenland und der Steiermark wurden mineral-chemisch untersucht, um Aufschluß über ihre Evolution vor der Eruption zu erhalten. Klinopyroxene mit ihren vielfältigen Subtitutionsmöglichkeiten erlauben am besten eine Abschätzung der Evolution der Basalte. Pyroxen-Einsprenglinge der Basalte zeigen sowohl konzentrischen als auch sektoralen Zonarbau. Die von uns untersuchten Einsprenglinge zeigen in den verschiedenen Sektoren nicht nur unterschiedliche Gehalte an Ti, Al und Fe, sondern vielfach auch unterschiedliche Cr-Gehalte. Dies macht es wahrscheinlich, daß die Verteilung von Cr zwischen Klinopyroxen und Schmelze von der Kristallisations-Kinetik beeinflußt wird.

Die Tiefe in der die Basalte kristallisierten und differenzierten kann von den Ti- und Al-Gehalten der Klinopyroxen- Einsprenglinge abgeschätzt werden. Die Zusammensetzung der Klinopyroxene im Verein mit den Gehalten an kompatiblen Spurenelementen und denmg-Werten der Gesteine erlauben den Schluß, daß die Alkalibasalte von Pauliberg und Steinberg vor ihrer Eruption eine geringfügige Olivinund Klinopyroxen-Fraktionierung in einer seichten Magmakammer erlebten. Der Nephelinit vorn Stradnerkogel hingegen erfuhr hauptsächlich eine Klinopyroxen Fraktionierung unter Hochdruck-Bedingungen, möglicherweise im oberen Erdmantel.

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Copyright information

© Springer-Verlag 1991

Authors and Affiliations

  • G. Dobosi
    • 1
  • R. Schultz-Güttler
    • 2
  • G. Kurat
    • 3
  • A. Kracher
    • 4
  1. 1.Hungarian Academy of SciencesLaboratory for Geochemical ResearchBudapestHungary
  2. 2.Instituto de GeocienciasUniversidade de Sao PauloSao PauloBrazil
  3. 3.Naturhistorisches MuseumViennaAustria
  4. 4.Department of Earth SciencesIowa State UniversityAmesUSA

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