Early Career: Development of a New Rock Deformation Apparatus for Investigating Earth's Upper Mantle

Washington University, Saint Louis MO

Investigators

Abstract

This proposal outlines a plan for the continued development of the Large Volume Torsion apparatus (LVT), a new rock deformation apparatus designed to investigate microstructural phenomena at the pressures and temperatures of Earth's crust and uppermost mantle. The development of a new rock deformation apparatus will benefit the community in a number of ways. The apparatus will be optimized for a critical and under-investigated range of deformation conditions, which will open new avenues for exploration of Earth's upper mantle and the interiors of other terrestrial planets. This support will assist the development of an early career scientist and will also enhance the training and development of a research engineer in rock mechanics. Educational opportunities for students and postdoctoral researchers will be significant, as they will participate in all phases of the design, calibration, and implementation of the new apparatus. The design of the new apparatus will be made publically available, and the details of its construction will be disseminated via the Internet. Access to these designs will benefit other early career scientists and established researchers as they plan their first labs or expand existing labs. Rock deformation apparatus are not available commercially and efforts to design devices with unique capabilities are essential for the advancement of rock mechanics, and many active areas of study within structural geology and geophysics. One critical feature of the LVT is that it deforms materials in torsion. The benefit of this geometry is that samples can be deformed to extremely large strains. Research at lower pressures and temperatures has emphasized the importance of large strains for developing steady state deformation microstructures. Large strains are needed to generate microstructures that are viscously anisotropic and to reproduce microstructures observed in mantle shear zones; viscous anisotropy and localized deformation are key factors that control the dynamics of plates. Large strains are also needed to investigate the generation of crystallographic fabrics; the relationships between these fabrics and seismic anisotropy are essential for interpreting patterns of flow in the mantle, particularly in the vicinity of plate boundaries. Elevated pressures, which are possible with this apparatus design, expand the range of materials and planetary conditions that can be studied, by suppressing unwanted phase changes, melting, and brittle deformation.