Orthopyroxene + sillimanite predating sapphirine + quartz: A rare case of ultrahigh-temperature metamorphism from the central zone, limpopo complex, South Africa

Georgy A. Belyanin, H. M. Rajesh, Krishnan Sajeev, Dirk D. Van Reenen

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Sapphirine + quartz and orthopyroxene + sillimanite occur in garnet from an Mg-Al granulite from the Central Zone of the Limpopo Complex in South Africa. Textural evidence and a chemical gradient in garnet between the zones preserving the inclusions argue for the formation of sapphirine + quartz after orthopyroxene + sillimanite. Petrological observations, pressure-temperature phase diagrams, and compositional and model proportion results on isopleths indicate the sapphirine + quartz + garnet + orthopyroxene (high-Al) assemblage as the peak metamorphic assemblage (~1050 °C at ~8.5 kbars), whereas orthopyroxene (low-Al) + sillimanite represents the prograde stage (at ca. 900 °C at ~8.5 kbars). Our report of these two diagnostic ultrahigh-temperature mineral assemblages in garnet from an Mg-Al granulite is unique, given the rare occurrence of sapphirine + quartz postdating orthopyroxene + sillimanite assemblage in granulites.

Original languageEnglish
Pages (from-to)1153-1163
Number of pages11
JournalCanadian Mineralogist
Volume50
Issue number5
DOIs
Publication statusPublished - Oct 2012

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ultrahigh temperature metamorphism
sapphirine
Quartz
Garnets
sillimanite
orthopyroxene
quartz
garnet
granulite
Temperature
Phase diagrams
Minerals
temperature
diagram
Africa
mineral

All Science Journal Classification (ASJC) codes

  • Geochemistry and Petrology

Cite this

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abstract = "Sapphirine + quartz and orthopyroxene + sillimanite occur in garnet from an Mg-Al granulite from the Central Zone of the Limpopo Complex in South Africa. Textural evidence and a chemical gradient in garnet between the zones preserving the inclusions argue for the formation of sapphirine + quartz after orthopyroxene + sillimanite. Petrological observations, pressure-temperature phase diagrams, and compositional and model proportion results on isopleths indicate the sapphirine + quartz + garnet + orthopyroxene (high-Al) assemblage as the peak metamorphic assemblage (~1050 °C at ~8.5 kbars), whereas orthopyroxene (low-Al) + sillimanite represents the prograde stage (at ca. 900 °C at ~8.5 kbars). Our report of these two diagnostic ultrahigh-temperature mineral assemblages in garnet from an Mg-Al granulite is unique, given the rare occurrence of sapphirine + quartz postdating orthopyroxene + sillimanite assemblage in granulites.",
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Orthopyroxene + sillimanite predating sapphirine + quartz : A rare case of ultrahigh-temperature metamorphism from the central zone, limpopo complex, South Africa. / Belyanin, Georgy A.; Rajesh, H. M.; Sajeev, Krishnan; Van Reenen, Dirk D.

In: Canadian Mineralogist, Vol. 50, No. 5, 10.2012, p. 1153-1163.

Research output: Contribution to journalArticle

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