ORTHOPYROXENE plus SILLIMANITE PREDATING SAPPHIRINE plus QUARTZ: A RARE CASE OF ULTRAHIGH-TEMPERATURE METAMORPHISM FROM THE CENTRAL ZONE, LIMPOPO COMPLEX, SOUTH AFRICA

Journal article

Authors/Editors

Rajesh, Hariharan

Research Areas

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Publication Details

Author list: Belyanin GA, Rajesh HM, Sajeev K, Van Reenen DD

Publisher: Mineralogical Association of Canada

Place: QUEBEC

Publication year: 2012

Journal: The Canadian Journal of Mineralogy and Petrology (0008-4476)

Journal acronym: CAN MINERAL

Volume number: 50

Issue number: 5

Start page: 1153

End page: 1163

Number of pages: 11

ISSN: 0008-4476

eISSN: 1499-1276

Languages: English-Great Britain (EN-GB)

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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 (similar to 1050 degrees C at similar to 8.5 kbars), whereas orthopyroxene (low-Al) + sillimanite represents the prograde stage (at ca. 900 degrees C at similar to 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.

Keywords

high-Al orthopyroxene, Limpopo Complex, Mg-Al granulite, orthopyroxene plus sillimanite, Sapphirine plus quartz, ultrahigh-temperature metamorphism

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