Sodicgedrite in ultrahigh-temperature Mg-Al-rich rocks from the Palghat-Cauvery Shear Zone system, southern India

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著者

    • TSUNOGAE Toshiaki
    • Graduate School of Life and Environmental Sciences (Earth Evolution Sciences), University of Tsukuba
    • SANTOSH M.
    • Department of Natural Environmental Science, Faculty of Science, Kochi University

抄録

We report high-Na gedrite (sodicgedrite) with up to 3.1 wt% Na<sub>2</sub>O (∼ 0.81 Na<sup>A</sup> pfu) in ultrahigh-temperature (UHT) Mg-Al-rich rocks from the northern margin of the Pan-African Madurai Block along the Palghat-Cauvery Shear Zone system, southern India. An amount of Na<sup>A</sup> of the gedrite increases with increasing Al<sup>IV</sup>. The sum of Na<sup>A</sup> and Al<sup>IV</sup> also increases linearly with decreasing Si suggesting the substitution of Na<sup>A</sup>Al<sup>IV</sup> ↔ Si. The negative correlation between Fe + Mg + Si and Al is probably due to the tschermak substitution ((Fe,Mg)<sup>VI</sup>Si<sup>IV</sup> ↔ Al<sup>VI</sup>Al<sup>IV</sup>). The relatively coarse-grained nature and porphyroblastic occurrence of the sodicgedrite suggest that the mineral recrystallized at the peak UHT metamorphism. In contrast, retrograde gedrite with cordierite is less sodic with 1.1-1.6 wt% Na<sub>2</sub>O (Na<sup>A</sup> = 0.24-0.35 pfu). Our data suggest that high-Na content in gedrite is a possible indicator of UHT metamorphism.

収録刊行物

  • Journal of mineralogical and petrological sciences  

    Journal of mineralogical and petrological sciences 102(1), 39-43, 2007-02-01 

    日本鉱物科学会

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各種コード

  • NII論文ID(NAID)
    10018411510
  • NII書誌ID(NCID)
    AA11460926
  • 本文言語コード
    ENG
  • 資料種別
    SHO
  • ISSN
    13456296
  • データ提供元
    CJP書誌  CJP引用  J-STAGE 
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