Halogen Heterogeneity in the Lithosphere and Evolution of Mantle Halogen Abundances Inferred From Intraplate Mantle Xenoliths

Masahiro Kobayashi, Hirochika Sumino, Ray Burgess, Shun'ichi Nakai, Tsuyoshi Iizuka, Jun Nagao, Hiroyuki Kagi, Michihiko Nakamura, Eiichi Takahashi, Tetsu Kogiso, Chris J. Ballentine

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

We present halogen, noble gas, and major and trace element compositions of mantle xenoliths from intraplate settings (Eifel, Kilbourne Hole, San Carlos, and Hawaii). The xenoliths show a wide range of halogen elemental ratios, which form two arrays centered on the halogen composition of mid-ocean ridge basalts. The samples on the array toward high I/Cl value have relatively low Cl concentration and low ratios of highly incompatible elements relative to heavy rare earth elements, whereas the samples on the array toward low Br/Cl value have higher Cl concentration and trace elements ratios. The detailed mechanisms to account for these signatures are equivocal at present. However, they are most likely to be related to secondary processes of volatile loss during partial melting and secondary phase formation during interaction with melts. The common primary mid-ocean ridge basalt-like halogen ratios in mantle xenoliths from different parts of the globe indicate that the mantle itself must have a relatively uniform composition over a wide scale. The mantle has maintained its halogen composition over billion year timescales without being affected by I-rich halogens being transported into the mantle. Mass balance calculations suggest that, in order to maintain the I/Cl ratio of the convecting mantle over 2 Gyr, the I/Cl ratio of the subducted halogens must be no more than several times higher than the present-day mantle value.

Original languageEnglish
Pages (from-to)952-973
Number of pages22
JournalGeochemistry, Geophysics, Geosystems
Volume20
Issue number2
DOIs
Publication statusPublished - 2019 Feb

Keywords

  • Halogen
  • Intraplate setting
  • Lithospheric mantle
  • Mantle xenolith
  • Subcontinental lithospheric mantle

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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