Formation of triple-layer coronas between corundum and hornblende from the Lützow-Holm Complex at Akarui Point, East Antarctica

Yuki Mori, Takeshi Ikeda

研究成果: ジャーナルへの寄稿記事

抄録

Triple-layer coronas around corundum occur in the Lützow-Holm Complex at Akarui Point, East Antarctica. The monomineralic layers of green spinel, sapphirine, and plagioclase are arranged in this order from corundum to the matrix hornblende, indicative of the reaction corundum + hornblende = green spinel + sapphirine + plagioclase + H2O-fluid. Singular value decomposition analysis in the simplified Na2O-CaO-MgO-Al2O3-SiO2-H2O system implies that either Na2O and CaO, Na2O and MgO, or CaO and SiO2 were open during the corona formation. The position of the initial boundary between corundum and hornblende coincided with the present sapphirine-plagioclase boundary, as judged from the spatial position of the brownish-green spinel in the coronas which is also present in the matrix and hornblende. The flow of Al2O3 decreased outward and completely ceased at the plagioclase- hornblende boundary. This feature together with the monotonic decrease in Al content from corundum to hornblende as well as within sapphirine and plagioclase suggests that diffusion of Al2O3 controlled the corona formation. The net reaction showed an increase in volume, indicating that the products were stable at lower pressures. Therefore, the corona-forming reaction took place during the decompression stage of the Lützow- Holm Complex.

元の言語英語
ページ(範囲)68-81
ページ数14
ジャーナルJournal of Mineralogical and Petrological Sciences
113
発行部数2
DOI
出版物ステータス出版済み - 1 1 2018

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corundum
Antarctic regions
plagioclase
hornblende
coronas
corona
sapphirine
aluminum oxides
spinel
pressure reduction
decomposition analysis
matrices
matrix
decompression
low pressure
Antarctica
decomposition
fluids
products
fluid

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geology

これを引用

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abstract = "Triple-layer coronas around corundum occur in the L{\"u}tzow-Holm Complex at Akarui Point, East Antarctica. The monomineralic layers of green spinel, sapphirine, and plagioclase are arranged in this order from corundum to the matrix hornblende, indicative of the reaction corundum + hornblende = green spinel + sapphirine + plagioclase + H2O-fluid. Singular value decomposition analysis in the simplified Na2O-CaO-MgO-Al2O3-SiO2-H2O system implies that either Na2O and CaO, Na2O and MgO, or CaO and SiO2 were open during the corona formation. The position of the initial boundary between corundum and hornblende coincided with the present sapphirine-plagioclase boundary, as judged from the spatial position of the brownish-green spinel in the coronas which is also present in the matrix and hornblende. The flow of Al2O3 decreased outward and completely ceased at the plagioclase- hornblende boundary. This feature together with the monotonic decrease in Al content from corundum to hornblende as well as within sapphirine and plagioclase suggests that diffusion of Al2O3 controlled the corona formation. The net reaction showed an increase in volume, indicating that the products were stable at lower pressures. Therefore, the corona-forming reaction took place during the decompression stage of the L{\"u}tzow- Holm Complex.",
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