The role of harzburgite layers in the morphology of subducting plates and the behavior of oceanic crustal layers

Abstract

Numerical simulations of mantle convection with semidynamic plate subduction in 3-D geometry is performed to investigate the role of harzburgite layers in the morphology of subducting plates and the behavior of oceanic crustal layers. The results show that a "buckled" crustal layer is observed under the "heel" of the stagnant slab that begins to penetrate into the lower mantle, regardless of the magnitude of the viscosity of the harzburgite layer, δηhrz, when the factor of viscosity increase at the boundary of the upper and lower mantle, δη lm, is larger than 60-100. As δηhrz increases, the curvature of buckling is larger. When δηlm and δηhrz are larger, the volumes of crustal and harzburgite materials trapped in the mantle transition zone (MTZ) are also larger, although almost all of the materials penetrate into the lower mantle. These materials are trapped in the MTZ for over tens of millions of years. Key Points The role of harzburgite layers in the behavior of plates is numerically studied The buckled crustal layer is found under the stagnant slab in this numerical model A factor of viscosity increase at the upper and lower mantle boundary is ∼100 ©2013. American Geophysical Union. All Rights Reserved.