Zoned clinopyroxenes in alkalic basalt: clues to fractionation and magma-mixing histories for seemingly primitive magmas

R. V. Fodor, G. Dobosi, A. N. Sial

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

Tertiary alkalic basalts in northeastern Brazil have >12 wt.% MgO, ultramafic xenoliths, olivine xenocrysts, and zoned clinopyroxene phenocrysts. Clinopyroxene compositions are used to assess whether these basalts represent mantle-equilibrium melts, as MgO suggests, or fractionated magmas with evolved compositions obscured by contributions to MgO from xenocrystic peridotitic olivine. The study shows that detailed documentation of clinopyroxene zonations can disclose magma pre-eruption histories, such as mixing of melts and multiple storage and crystallization regimes, otherwise masked by artificially high MgO. It is also observed that some clinopyroxene phenocrysts have cores of xenocrystic Cr-diopside that represent mantle peridotite, and cores of green, Fe-rich diopside that are probably fragments of metasomatized mantle. -from Authors

Original languageEnglish
Pages (from-to)133-148
Number of pages16
JournalChemie der Erde - Geochemistry
Volume55
Issue number2
Publication statusPublished - 1995

Fingerprint

Fractionation
fractionation
basalt
clinopyroxene
magma
Earth mantle
histories
olivine
diopside
history
Crystallization
mantle
Chemical analysis
documentation
peridotite
melt
Brazil
volcanic eruptions
fragments
crystallization

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

Cite this

Zoned clinopyroxenes in alkalic basalt : clues to fractionation and magma-mixing histories for seemingly primitive magmas. / Fodor, R. V.; Dobosi, G.; Sial, A. N.

In: Chemie der Erde - Geochemistry, Vol. 55, No. 2, 1995, p. 133-148.

Research output: Contribution to journalArticle

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