CRYSTALLOGRAPHIC CONTROLS ON THE FRICTIONAL STRENGTHS OF LAYER-STRUCTURED MINERALS

摘要

Phyllosilicates are common constituents of fault gouge, and their presence in faults is significant because they are weaker than most other rock-forming minerals whose coefficients of friction (shear stress/effective normal stress), μ≈ 0.8 (Byerlee's law). We are investigating the frictional strengths of phyllosilicate and other layer-structured minerals, to identify the factors that limit their strengths and ultimately to use this knowledge to determine fault-zone properties at depth. As part of a preliminary study (Morrow et al., 2000, Geophys. Res. Lett. 27: 815-818), we tested mineral separates of talc, muscovite, chlorite, lizardite, kaolinite, brucite, and graphite. Here, we report new data for margarite, pyrophyllite, a biotite and two phlogopites, a second muscovite and a paragonite/muscovite mixture.