論文

査読有り
2013年3月

Recycled crustal zircons from podiform chromitites in the Luobusa ophiolite, southern Tibet

ISLAND ARC
  • Shinji Yamamoto
  • Tsuyoshi Komiya
  • Hiroshi Yamamoto
  • Yoshiyuki Kaneko
  • Masaru Terabayashi
  • Ikuo Katayama
  • Tsuyoshi Iizuka
  • Shigenori Maruyama
  • Jingsui Yang
  • Yoshiaki Kon
  • Takafumi Hirata
  • 全て表示

22
1
開始ページ
89
終了ページ
103
記述言語
英語
掲載種別
研究論文(学術雑誌)
DOI
10.1111/iar.12011
出版者・発行元
WILEY-BLACKWELL

We have measured the UPb age of zircon grains separated from podiform chromitites from the Luobusa ophiolite, Southern Tibet, using laser ablation microprobe inductively coupled plasma mass spectrometer (LA-IC-PMS), to determine the age relationship between the podiform chromitites and the host mantle peridotite. Spot analyses with LA-IC-PMS, assisted by cathodoluminescence images gave a wide age range, from the Cretaceous to the Late Archean (ca 1002700Ma). The minimum ages of ca 100Ma, plotted on the concordia curve, were slightly lower than the metasomatic (magmatic) event in the supra-subduction zone (120 +/- 10Ma), suggesting that the zircons suffered some Pb loss. However, most of the ages found are much older than those of the chromitite and ophiolite formation. Laser Raman spectroscopy analyses revealed that the zircons recovered from the chromitites contain crustal mineral inclusions, such as quartz and K-feldspar, but lack mantle minerals (e.g., olivine, pyroxene, and chromite), suggesting that they had a crustal origin. The results indicate that crustal zircons in chromitites had a xenocrystic origin and resided in the mantle peridotite for a long period before being entrained into the chromitite during its formation. This indicates that the mantle peridotite under the Neo-Tethys Ocean was affected by the crustal material contamination. Our results are consistent with previous reports that mid-oceanic ridge basalts in the Indian Ocean have the isotopic signature of crustal material contamination. From these results, and previous isotopic studies on Gondwana geology, we conclude that ancient zircons from podiform chromitites could provide evidence of crustal material being recycled through the upper mantle.

リンク情報
DOI
https://doi.org/10.1111/iar.12011
Web of Science
https://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=JSTA_CEL&SrcApp=J_Gate_JST&DestLinkType=FullRecord&KeyUT=WOS:000315499700008&DestApp=WOS_CPL
ID情報
  • DOI : 10.1111/iar.12011
  • ISSN : 1038-4871
  • eISSN : 1440-1738
  • Web of Science ID : WOS:000315499700008

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