Experimental constraints on the serpentinization rate of fore-arc peridotites: Implications for the upwelling condition of the slab-derived fluid

T. Nakatani, M. Nakamura

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)

Abstract

To constrain the water circulation in subduction zones, the hydration rates of peridotites were investigated experimentally in fore-arc mantle conditions. Experiments were conducted at 400–580°C and 1.3 and 1.8 GPa, where antigorite is expected to form as a stable serpentine phase. Crushed powders of olivine ± orthopyroxene and orthopyroxene + clinopyroxene were reacted with 15 wt % distilled water for 4–19 days. The synthesized serpentine varieties were lizardite and aluminous lizardite (Al-lizardite) in all experimental conditions except those of 1.8 GPa and 580°C in the olivine + orthopyroxene system, in which antigorite was formed. In the olivine + orthopyroxene system, the reactions were interface-controlled except for the reaction at 400°C, which was transport-controlled. The corresponding reaction rates were 7.0 × 10−12 to 1.5 × 10−11 m s−1 at 500–580°C and 7.5 × 10−16 m2 s−1 at 400°C for the interface and transport-controlled reactions, respectively. Based on a simple reaction-transport model including these hydration rates, we infer that penetration of the slab-derived fluid all the way through a water-unsaturated fore-arc mantle is allowed only when focused flow occurs with a spacing larger than 77–229 km in hot subduction zones such as Nankai and Cascadia. However, the necessary spacing is only 2.3–4.6 m in intermediate-temperature subduction zones such as Kyushu and Costa Rica. These calculations imply that fluid leakage in hot subduction zones may occur after the fore-arc mantle is totally hydrated, whereas in intermediate-temperature subduction zones, leakage through a water-unsaturated fore-arc mantle may be facilitated.

Original languageEnglish
Pages (from-to)3393-3419
Number of pages27
JournalGeochemistry, Geophysics, Geosystems
Volume17
Issue number8
DOIs
Publication statusPublished - 2016 Aug 1

Keywords

  • Arima-type fluid
  • fore-arc
  • hydration reaction
  • serpentine
  • slab fluid

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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