Feldspar in felsic orthogneiss as indicator for UHT crustal processes

  • HOKADA Tomokazu
    National Institute of Polar Research Department of Polar Science, The Graduate University for Advanced Studies
  • SUZUKI Satoko
    Center for Chronological Research, Nagoya University

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抄録

Felsic orthogneisses with tonalitic and granodioritic compositions are dominant in the ultrahigh-temperature (UHT) metamorphic terrane of the Archaean-early Proterozoic Napier Complex, East Antarctica. Antiperthitic or mesoperthitic ternary feldspar occurs in addition to Qtz, Opx with/without Cpx in these felsic orthogneisses. Such feldspar grains commonly display zonal structure with respect to the volume of exsolution lamella; lamellae-enriched core and lamellae-free rim. Pre-exsolution one-phase compositions have been recovered separately for the feldspar core (an:ab:or = 20-28:53-56:17-28 in tonalitic samples and an:ab:or = 15-17:37-48:36-48 in granodioritic samples) and for the whole feldspar grain (an:ab:or = 24-29:58-63:13 in tonalitic samples and an:ab:or = 18-20:45-56:24-37 in granodioritic samples). Application of feldspar thermometry for these recovered one-phase compositions and the feldspar cores yield a temperature range of 940-1100 °C, which is relatively higher temperatures than the whole feldspar grain giving > 850-1070 °C. These compositional differences between core and rim of single feldspar grains are probably due to either sub-solidus or melt-related processes. The compositional and textural information of ternary feldspars in felsic orthogneisses can be therefore potential tools for understanding UHT crustal processes.

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詳細情報

  • CRID
    1390282681522248704
  • NII論文ID
    10018106142
  • NII書誌ID
    AA11460926
  • DOI
    10.2465/jmps.101.260
  • ISSN
    13493825
    13456296
  • 本文言語コード
    en
  • データソース種別
    • JaLC
    • Crossref
    • CiNii Articles
  • 抄録ライセンスフラグ
    使用不可

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