Ancient oceanic crust in island arc lower crust

Evidence from oxygen isotopes in zircons from the Tanzawa Tonalitic Pluton

Kazue Suzuki, Kouki Kitajima, Yusuke Sawaki, Kentaro Hattori, Takafumi Hirata, Shigenori Maruyama

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Knowledge of the lithological variability and genesis of island arc crust is important for understanding continental growth. Although the volcanic architecture of island arcs is comparatively well known, the nature of island arc middle- and lower-crust remains uncertain owing to limited exposure. One of the best targets for deciphering the evolution of an island arc system is the Tanzawa Tonalites (4-9Ma), in the intra-oceanic Izu-Bonin-Mariana arc. These tonalities which occupied a mid-crustal position were generated by partial melting of lower crust. To constrain protoliths of the plutonic rocks in the island arc lower crust, in-situ O-isotopic analysis using an IMS-1280 Secondary Ion Mass Spectrometer was carried out on 202 zircon grains separated from 4 plutons in the Tanzawa Tonalite. δ18O value of the zircons ranges from 4.1‰ to 5.5‰ and some zircons have δ18O slightly lower than the mantle range. The low zircon δ18O values from the Tanzawa Tonalite suggest that their protoliths involved materials with lower δ18O values than those of the mantle. Hydrothermally altered gabbros in the lower oceanic crust often have lower δ18O values than mantle and can be primary components of arc lower crust. The Tanzawa Tonalite is interpreted to have been formed by partial melting of island arc lower crust. Thus the low δ18O values in zircons from the Tanzawa Tonalites may originate by melting of the hydrothermally altered gabbro. Ancient oceanic crustal material was likely present in the Izu-Bonin-Mariana arc lower crust, at the time of formation of the Tanzawa Tonalites.

Original languageEnglish
Pages (from-to)43-54
Number of pages12
JournalLithos
Volume228-229
DOIs
Publication statusPublished - Jul 1 2015
Externally publishedYes

Fingerprint

Oxygen Isotopes
oceanic crust
lower crust
pluton
island arc
oxygen isotope
zircon
Melting
tonalite
mantle
protolith
partial melting
Mass spectrometers
isotopic analysis
plutonic rock
Rocks
gabbro
Ions
spectrometer
melting

Keywords

  • Arc lower-crust
  • IBM arc
  • Oceanic crust
  • Tanzawa Tonalitic Pluton
  • Zircon oxygen isotope

ASJC Scopus subject areas

  • Geochemistry and Petrology

Cite this

Ancient oceanic crust in island arc lower crust : Evidence from oxygen isotopes in zircons from the Tanzawa Tonalitic Pluton. / Suzuki, Kazue; Kitajima, Kouki; Sawaki, Yusuke; Hattori, Kentaro; Hirata, Takafumi; Maruyama, Shigenori.

In: Lithos, Vol. 228-229, 01.07.2015, p. 43-54.

Research output: Contribution to journalArticle

Suzuki, Kazue ; Kitajima, Kouki ; Sawaki, Yusuke ; Hattori, Kentaro ; Hirata, Takafumi ; Maruyama, Shigenori. / Ancient oceanic crust in island arc lower crust : Evidence from oxygen isotopes in zircons from the Tanzawa Tonalitic Pluton. In: Lithos. 2015 ; Vol. 228-229. pp. 43-54.
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