Effects of mineral mode and textural variation on the seismic anisotropy in lithospheric mantle: an example from Horoman peridotites

Abstract

We performed a numerical analysis of seismic velocities in mantle peridotite using the elastic constants and crystallographic preferred orientations (CPOs) of olivine, orthopyroxene, and clinopyroxene. Proportions of olivine in the samples ranged from 50 to 100% mechanically, whereas the two pyroxenes ranged from 0 to 50%. We utilized three lherzolite samples from the Horoman peridotite complex for this study. As the quantity of pyroxene increased, the P-wave velocities in the X-direction (8.35–9.14 km/s) and P-wave anisotropies (5.51–14.50%) decreased in all samples. However, the S1-wave velocities remained relatively consistent, with Vs1 ranging from 4.79 to 5.15 km/s and Vs2 from 4.55 to 4.92 km/s. The maximum S-wave anisotropies decreased as orthopyroxene contents increased. As a consequence, non-negligible effects of pyroxenes resulted in the variation of seismic velocities, suggesting the orthopyroxene/clinopyroxene contents and their CPOs could be one of critical factors for evaluating seismic anisotropy within the upper mantle. Graphical abstract