Abstract
Dehydration and fluid circulation are integral parts of subduction tectonics that govern the dynamics of the wedge mantle. The knowledge of the elastic behavior of aqueous fluid is crucial to understand the fluid–rock interactions in the mantle through velocity profiles. In this study, we investigated the elastic wave velocities of chlorite at high pressure beyond its dehydrating temperature, simulating the progressive dehydration of hydrous minerals in subduction zones. The dehydration resulted in an 8% increase in compressional (Vp) and a 5% decrease in shear wave (Vs) velocities at 950 K. The increase in Vp can be attributed to the stiffening of the sample due to the formation of secondary mineral phases followed by the dehydration of chlorite. The fluid-bearing samples exhibited Vp/Vs of 2.45 at 950 K. These seismic parameters are notably different from the major mantle minerals or hydrous silicate melts and provide unique seismic criteria for detecting mantle fluids through seismic tomography.
Highlights
Chlorite in Subduction Zones.The dehydration of subducted hydrous minerals releases a flux of fluid into the wedge mantle [1]
The attenuation is often described by the seismic attenuation factor (Q−1 ), which depends on the temperature, composition, fluid/melt fraction, fluid/melt geometry, and grain size [12,13], and provides robust constraints on subduction zone components [14]
The present study investigated the elastic properties of the dehydration-induced fluid occurring in subduction zones
Summary
Chlorite in Subduction Zones.The dehydration of subducted hydrous minerals releases a flux of fluid into the wedge mantle [1]. Detection and differentiation of aqueous fluid and silicate melt and how they migrate and interact with the overlying mantle are fundamental to the understanding of the subduction zone system [8]. The low velocity and high attenuation (low-Q) in subduction zones have often been interpreted as an indication of the presence of a liquid phase [8]. This interpretation comes from the notion that the shearing motion cannot be transmitted through a liquid, as it may slow down the compressional (P) waves and hinder the propagation of shear (S) waves and attenuate [9,10,11]. The attenuation is often described by the seismic attenuation factor (Q−1 ), which depends on the temperature, composition, fluid/melt fraction, fluid/melt geometry, and grain size [12,13], and provides robust constraints on subduction zone components [14]
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