Deformation Mechanisms
I have been interested to identify the grain–scale deformation mechanisms operative over a broad range of P,T conditions in monomineralic aggregates of quartz and of feldspar, and to relate these to the microstructures they produce and their mechanical behavior. Some studies have illustrated the grain–scale deformation mechanism transitions responsible for the macroscopic brittle–ductile transitions; others have identified processes which involve strain–weakening and thus lead to ductile shear zone formation. The identification in feldspar aggregates of ductile deformation by distributed cracking (cataclastic flow) and the strain weakening associated with low temperature grain boundary migration recrystallization are results that have important geologic implications.
Related Publications:
Tullis, J., Christie, J.M., and Griggs, D.T., 1973, Microstructures and preferred orientations in experimentally deformed quartzites: Geol. Soc. Amer. Bull., 84, 297-314.
Mitra, S. and Tullis, J., 1979, A comparison of intracrystalline deformation in naturally and experimentally deformed quartzites: Tectonophysics, 53, T21-T27.
Shelton , G.L., Tullis, J., and Tullis, T.E, 1980, Experimental faults at high temperature and pressure: Geophys. Res. Lett., 8, 55-58.
Tullis, J. and Yund, R.A., 1985, Dynamic recrystallization of feldspar: a mechanism for ductile shear zone formation: Geology, 13, 238-241.
Tullis, J. and Yund, R.A., 1987, Transition from cataclastic flow to dislocation creep of feldspar: mechanisms and microstructures: Geology, 15, 606-609.
Hirth, J.G. and Tullis, J., 1989, Roles of porosity and pressure in the cataclastic flow of quartz aggregates: J. Geophys. Res., 94, 17,825–17,838.
Tullis, J., and Yund, R.A., 1991, Experimental evidence for diffusion creep in feldspar aggregates: J. Struc. Geol., 13, 987–1000.
Hirth, G., and Tullis, J., 1992, Dislocation creep regimes in quartz aggregates: J. Struc. Geol., 14, 145-160.
Tullis, J., and Yund, R.A., 1992, The brittle-ductile transition in feldspar aggregates: An experimental study: in, B. Evans & T.–f. Wong (eds.) Fault Mechanics and Transport Properties of Rocks, Academic Press, NY, 89-118.
Hirth, G. and Tullis, J., 1994, The nature of the brittle to plastic transition in quartz aggregates. J. Geophys. Res., 99, 11731-11748.
Gleason, G. and Tullis, J., 1995. A flow law for dislocation creep of quartz aggregates determined with the molten salt cell. Tectonophysics, 247, 1-24.
Post, A.D. and Tullis, J., 1999, A recrystallized grain size piezometer for experimentally deformed feldspar aggregates. Tectonophysic, 303, 159-173.
Stipp, M. and Tullis, J., 2003. The recrystallized grain size piezometer for quartz. Geophys. Rres. Lett., 30, no. 21, 2088, doi:10.1029/2003 GL018444.
Stunitz, H., Fitz Gerald, J.D. and Tullis, J. 2003. Dislocation generation, slip systems and dynamic recrystallization in experimentally deformed plagioclase single crystals. Tectonophys. 372, 215-233.
Brown faculty collaborators:
Greg Hirth
Other project collaborators:
See publications list. |
Optical photomicrographs (in circularly polarized light) of Black Hills quartzite starting material, and samples experimentally sheared and recrystallized in dislocation creep regimes 1, 2 and 3. Back to Jan Tullis's Brown Research Profile |
