Survival of pyropic garnet in subducting plates

Masayuki Nishi, Takumi Kato, Tomoaki Kubo, Takumi Kikegawa

研究成果: ジャーナルへの寄稿学術誌査読

31 被引用数 (Scopus)


An experimental study has been conducted to clarify the conditions and kinetic aspects of the pyroxene-garnet transformation by using synthetic polycrystals (two pyroxenes + garnet) in the CaO-MgO-Al2O3-SiO2 system. The run products recovered from the in situ X-ray diffraction experiments in a double-stage multi-anvil system at 15.5-20.4 GPa and 800-1600 °C were carefully analyzed by scanning electron microscopy. Our results show that the pyroxene-garnet transformation proceeds by overgrowth of garnet absorbing the surrounding pyroxene components above 1550 °C. At 18.4 GPa and 1320 °C, pyroxenes (enstatite + diopside) directly decomposed to the assemblages (wadsleyite + stishovite + Ca-perovskite) without dissolving in garnet. The pyroxene-garnet transformation requires much higher temperatures than those needed for transformation of olivine to wadsleyite (∼1000 °C) and of pyroxenes to their high-pressure phases (∼1300 °C) in laboratory time (∼103 s) and grain (∼10-5 m) scales. Therefore, the pyroxene-garnet transformation is likely to be kinetically inhibited at low temperatures in the subducting plate, and the pyropic garnet could survive in the transition zone instead of equilibrium majoritic garnet.

ジャーナルPhysics of the Earth and Planetary Interiors
出版ステータス出版済み - 11月 2008

!!!All Science Journal Classification (ASJC) codes

  • 天文学と天体物理学
  • 地球物理学
  • 物理学および天文学(その他)
  • 宇宙惑星科学


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