How Do Variations In Mantle Viscosity And The Presence Of Hydrous Minerals In The Subducting Slab Influence The Formation Of Serpentinite Mud Volcanoes And The Associated Geochemical Signatures In The Forearc Regions Of Subduction Zones?

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The formation of serpentinite mud volcanoes in subduction zone forearcs is significantly influenced by two key factors: mantle viscosity and the presence of hydrous minerals in the subducting slab. Here's a structured summary of their effects:

Influence of Mantle Viscosity:

  1. Viscosity and Fluid Flow:

    • Lower mantle viscosity facilitates easier fluid flow, allowing serpentinized mantle and associated fluids to rise more readily, potentially leading to more frequent or widespread mud volcanoes.
    • Higher viscosity hinders fluid movement, resulting in more localized or slower mud volcano activity.

  2. Buoyancy and Serpentinization:

    • Serpentinization reduces mantle density, enhancing buoyancy. Lower viscosity allows this buoyant mantle to rise more easily, creating pathways for fluid escape.
    • Higher viscosity may impede this rise, affecting the distribution and intensity of mud volcanoes.

Role of Hydrous Minerals in the Subducting Slab:

  1. Water Release and Serpentinization:

    • Hydrous minerals release water during subduction, promoting serpentinization in the overlying mantle. This process softens the mantle, aiding fluid flow and mud volcano formation.

  2. Geochemical Signatures:

    • The dehydration of hydrous minerals introduces specific geochemical tracers, such as oxygen and hydrogen isotopes, into the fluids, influencing the mud's geochemical composition.

Geochemical Signatures:

  • The interaction of fluids with serpentinized mantle and subducting slab materials results in distinct geochemical signals, reflecting the mantle's contribution (e.g., high serpentinite-derived elements) and slab-derived components.
  • The form of water (e.g., supercritical fluids) at depth can further influence geochemical behaviors, affecting the emitted mud's characteristics.

Conclusion:

Mantle viscosity regulates the dynamics of fluid and serpentinized mantle movement, while hydrous minerals enhance water release and serpentinization, contributing to mud volcano formation and their geochemical traits. Together, these factors shape the distribution, frequency, and geochemical signatures of serpentinite mud volcanoes in subduction zones.