LPO Development in Lineated Peridotites

Abstract

Lattice preferred orientation (LPO) in olivine-rich rocks reflects deformation conditions and kinematics in the Earth’s mantle. Harzburgites with a strong lineation and weak foliation have recently been identified in the eastern part of the Red Hills massif in the Dun Mountain Ophiolite Belt in New Zealand. While studies have characterized the LPO in lineated rocks for minerals such as pyroxene and quartz subjected to constrictional strain, little work has focused on characterizing the crystallographic-preferred orientation of olivine in lineated peridotites. Microstructural data and fabric geometry suggest that spinel does not reflect the strain experienced by the rock as a whole, in spite of being used as an indicator for the average foliation and lineation. Additionally, this study supports existing work involving the relationship between the development of LPO and rotation of crystallographic axes in response to the principal stretches of the finite strain ellipsoid. The data suggest the pencil glide system can be activated not only in response to experimentally determined strain rates and temperatures, but also in response to the rotation of the principal stretches of the finite strain ellipsoid.