Temporal variation in primary magma compositions in the northeast Japan Arc

Shigeru Yamashita, Yoshiyuki Tatsumi, Susumu Nohda

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


A remarkable temporal variation in primary magma compositions has been found in the Northeast Japan arc. The trench-side magmas have become more enriched in FeO* and the backarc-side magmas have become more depleted in FeO* while retaining almost constant SiO2 levels for the last ∼20 million years. In order to understand the origin of the temporal variation, FeO* and SiO2 contents in partial melts are modeled for an adiabatically-rising mantle as a function of potential temperature and original composition of the mantle material. The result demonstrates that the primary magmas that are more depleted in FeO* were derived from the mantle materials either at lower potential temperatures or with compositions more depleted in basaltic components. A possible mechanism for the inferred primary magma variability is the change in depth intervals with time of magma production in a compositionally-layered mantle wedge; greater degrees of depletion at a greater depth is reconciled with a probable thermal regime in the mantle wedge.

Original languageEnglish
Pages (from-to)276-288
Number of pages13
JournalIsland Arc
Issue number3
Publication statusPublished - Sept 1996


  • Northeast Japan arc
  • Primary magma
  • Temporal variation

ASJC Scopus subject areas

  • Geology


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