Details

Autor(en) / Beteiligte

• Liu, W. L.
• Qi, H. W.
• Zhang, J. F.
• Wu, X.
• Li, J. F.
• Zhao, R.
• Wang, Y. F.
• Jin, Z. M.

Titel

Hydrostatic Dehydration Fabrics of Antigorite at High Pressure and High Temperature: Implications for Trench Parallel Seismic Anisotropy at Convergent Plate Boundaries

Ist Teil von

• Journal of geophysical research. Solid earth, 2021-09, Vol.126 (9), p.n/a

Ort / Verlag

Washington: Blackwell Publishing Ltd

Erscheinungsjahr

2021

Quelle

Wiley-Blackwell Journals

Beschreibungen/Notizen

• Antigorite dehydration is well known as a key process at convergent boundaries for the genesis of mantle wedge partial melting and intermediate‐depth earthquakes. However, the crystallographic preferred orientations (CPOs) of prograde minerals from antigorite dehydration and their effects on the seismic anisotropy of subducting slabs remain ambiguous and controversial. Here we report antigorite dehydration experiments on a foliated serpentinized peridotite at pressures of 0.3–6 GPa and temperatures of 700–900°C. Our results show that olivine CPO evolves from a fiber‐[100] type in fine grains to a type‐C like in coarse grains. We propose that the fiber‐[100] olivine CPO is developed by topotactic growth during incipient hydrostatic dehydration, while the orthorhombic type‐C like olivine CPO is developed by anisotropic growth resulting from an anisotropic fluid flow during later dehydration. The type‐C like olivine CPO in the antigorite‐rich layers after antigorite dehydration could contribute to the trench parallel fast shear wave seismic anisotropy at convergent plate boundaries. Plain Language Summary We study the crystallographic preferred orientations and seismic anisotropies of dehydrated antigorite samples. Our results show that the CPOs of prograde mineral, olivine, evolve from the fiber‐[100] CPO in fine grains to the type‐C like CPO in coarse grains. The type‐C like olivine CPO after antigorite dehydration could cause trench‐parallel fast shear wave seismic anisotropy observed at convergent plate boundaries. Key Points Olivine crystallographic preferred orientations (CPO) evolves from the fiber‐[100] CPO to the type‐C like CPO with increasing grain size during hydrostatic dehydration of antigorite The fiber‐[100] and type‐C like olivine CPOs are developed by topotactic growth and anisotropic growth, respectively The prograde olivine with type‐C like CPO could contribute to trench parallel seismic anisotropy at convergent boundaries