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<p>Serpentine stability dictates deep water cycling in subduction zones. We investigated pure serpentinites (≈ 13 wt.% H<sub>2</sub>O) using in-situ synchrotron X-ray diffraction and ultrasonic velocity measurements under two cold-slab P–T paths, varying excess water (0.9–31.5 wt.%). Here we report that under a cold core (or ultracold Moho) geotherm with &gt;6.9 wt.% excess water, serpentinites undergo deep hydration to form the 3.65-Å phase and phase E above 9.3 GPa and 420 °C (ca. 280 km depth), increasing total water to ≈ 19.3 wt.%. With &lt;6.9 wt.% excess water, serpentine transforms to phase E without water loss. Conversely, under a cold Moho geotherm, serpentinites dehydrate into phase E and clinoenstatite above 7.4 GPa and 585 °C (ca. 220 km depth), releasing ≈ 5.3 wt.% water. These divergent reactions highlight an underestimated water transport capacity of subducting slabs, generating lateral contrasts in hydration, density, and seismic velocity.</p>

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Serpentine’s wet breakdown path and enhanced water flux in cold subduction zones

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月24日

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  • Heehyeon Sim,
  • Yoonah Bang,
  • Huijeong Hwang,
  • Nico Giordano,
  • Dongzhou Zhang,
  • Hyun Hwi Lee,
  • Taeyeol Jeon,
  • Robert Farla,
  • Hanns-Peter Liermann,
  • Yongjae Lee

摘要

Serpentine stability dictates deep water cycling in subduction zones. We investigated pure serpentinites (≈ 13 wt.% H2O) using in-situ synchrotron X-ray diffraction and ultrasonic velocity measurements under two cold-slab P–T paths, varying excess water (0.9–31.5 wt.%). Here we report that under a cold core (or ultracold Moho) geotherm with >6.9 wt.% excess water, serpentinites undergo deep hydration to form the 3.65-Å phase and phase E above 9.3 GPa and 420 °C (ca. 280 km depth), increasing total water to ≈ 19.3 wt.%. With <6.9 wt.% excess water, serpentine transforms to phase E without water loss. Conversely, under a cold Moho geotherm, serpentinites dehydrate into phase E and clinoenstatite above 7.4 GPa and 585 °C (ca. 220 km depth), releasing ≈ 5.3 wt.% water. These divergent reactions highlight an underestimated water transport capacity of subducting slabs, generating lateral contrasts in hydration, density, and seismic velocity.