Seismic anisotropies of the Yugu peridotites (Gyeonggi Massif, South Korea) and their seismic implications in mantle shear zones

Abstract

This study investigates the relationship between olivine fabric transitions and seismic anisotropy in mantle shear zones, focusing on the Yugu peridotite body in the Korean Peninsula. Olivine, a key mineral in the upper mantle, influences seismic anisotropy through deformation fabrics. The Yugu peridotite body provides insights into these processes within mantle shear zones. Based on microstructures and olivine fabric transitions, this study categorizes peridotites into three groups (PM: proto-mylonite, M: mylonite, and UM: ultra-mylonite) and explores their seismic properties. The findings highlight a direct correlation between olivine fabric strength and seismic anisotropy. Group PM peridotites exhibited higher seismic anisotropy compared to those in Group M and UM peridotites. This study emphasizes that variations in seismic anisotropy within mantle shear zones are primarily driven by the strength of olivine fabric, with additional influences from fabric type and rock composition. The calculated anisotropic layer thickness supports the observation that seismic anisotropy is significantly larger away from the UM peridotites. These insights contribute to understanding of the complex interplay among olivine fabric, seismic anisotropy, and geological processes within mantle shear zones. The implications of this study extend to the improved interpretation of seismic data related to shear localization during peridotite exhumation.