Deformation and Fluid-Rock Interaction in the Supra-subduction Mantle: Microstructures and Water Contents in Peridotite Xenoliths from the Avacha Volcano, Kamchatka

Research on peridotite xenoliths from the Avacha Volcano, Kamchatka, reveals that the supra-subduction mantle experiences complex interactions between deformation and fluid-rock processes. The study found that olivine in these xenoliths deforms under low deviatoric stress (≤13 MPa) via dislocation creep, with a significant contribution from diffusional processes. Crystal preferred orientations indicate dominant activation of high-temperature, low-stress slip systems in olivine and orthopyroxene. Additionally, the study observed reactive percolation of Si-rich fluids, leading to secondary crystallization of orthopyroxene at the expense of olivine. Low water contents (1–8.6 ppm) in olivine suggest limited solubility and dehydration during exhumation, while variable water contents (25–506 ppm) in orthopyroxene indicate heterogeneous fluid interaction. The findings imply that percolation of Si-rich fluids or hydrous melts enhanced diffusion and lowered deviatoric stresses during ductile deformation without altering the dominant slip direction in olivine.

Soustelle, V., Tommasi, A., Demouchy, S., & Ionov, D. A. (2010). Deformation and Fluid-Rock Interaction in the Supra-subduction Mantle: Microstructures and Water Contents in Peridotite Xenoliths from the Avacha Volcano, Kamchatka. Journal of Petrology, 51(1-2), 363–394. https://doi.org/10.1093/petrology/egp085