Stereographic projection of the electrical conductivity of undeformed and deformed Carrara marble

Permeability of rocks

Stereographic projection of the electrical conductivity of undeformed and deformed Carrara marble

An experimental study of water permeability of mudstones has been carried out to evaluate some of the complexities of fluid flow through clay-bearing rocks (David Hawthorn, PhD graduate, with Ernie Rutter and Joe MacQuaker). We have also investigated the formation of faulting during compaction of muddy rocks, to help understand the formation of polygonal fault arrays in nature (Alex McDougall (MSc graduate) and Ernie Rutter).

We have collected oriented samples of clay-bearing fault gouge and measured its anisotropic permeability to water and inert gas, as a function of pore pressure, confining pressure, temperature and differential stress. The pore pressure oscillation techniques has been extensively employed for this. Permeability evolution has also been studied during progressive shearing of synthetic clay-bearing gouges of different clay content (Brian Crawford (now with Exxon-Mobil), Dan Faulkner (now at Liverpool) and Ernie Rutter).

  • Faulkner, D. R. & Rutter, E. H. 1998. The gas permeability of clay-bearing fault gouge at 20 degrees C. In: Faulting, fault sealing and fluid flow in hydrocarbon reservoirs (edited by Jones, G., Fisher, Q. J. & Knipe, R. J.). Geological Society of London, London.
  • Faulkner, D. R. & Rutter, E. H. 2000. Comparisons of water and argon permeability in natural clay- bearing fault gouge under high pressure at 20 degrees C. Journal of Geophysical Research-Solid Earth 105(B7), 16415-16426.
  • Faulkner, D. R. & Rutter, E. H. 2001. Can the maintenance of overpressured fluids in large strike-slip fault zones explain their apparent weakness? Geology 29(6), 503-506.
  • Faulkner, D. R. & Rutter, E. H. 2003. The effect of temperature, the nature of the pore fluid, and subyield differential stress on the permeability of phyllosilicate-rich fault gouge. Journal of Geophysical Research-Solid Earth 108(B5), art. no.-2227.

For more information contact: Ernie Rutter

 

Seismic velocity measurements

As part of our ongoing studies of lower crustal rocks, we have taken a full range of oriented cores from the Ivrea-Verbano lower crustal section (see below) of N. Italy and measured ultrasonic velocities as a function of pressure and temperature to 700 C and 500 MPa. These data have been combined with a reconstructed cross section through the region as it was when it was in the lower crust to produce a synthetic seismic reflection model of the section, for comparison with contemporary lower crustal reflection profiles (collaboration with Dave Waltham and Derek Blundell, Royal Holloway college, London). A new pressure vessel exclusively dedicated to high pressure velocity measurements is currently being used (Steve Covey-Crump, Ernie Rutter and Chidi Chukwunweike) to characterize velocities in a range of reservoir rocks at elevated confining and pore pressure.

  • Wendt, A. S., Bayuk, I. O., Covey-Crump, S. J., Wirth, R. & Lloyd, G. E. 2003. An experimental and numerical study of the microstructural parameters contributing to the seismic anisotropy of rocks. Journal of Geophysical Research-Solid Earth 108(B8), art. no.-2365.
  • Khazanehdari, J., Rutter, E. H. & Brodie, K. H. 2000. High-pressure-high-temperature seismic velocity structure of the midcrustal and lower crustal rocks of the Ivrea-Verbano zone and Serie dei Laghi, NW Italy. Journal of Geophysical Research 105(B6), 13843-13858.

For more information contact: Ernie RutterJulian Mecklenburgh or Steve Covey-Crump

 

Electrical conductivity of deforming rocks

Electrical conductivity can be sensitive probe of the microstructure of a material therefore by measuring the conductivity of a sample during deformation one can probe the microstructure of the deforming material. We are presently undertaking two projects one looking at electrical conductivity of marbles during high-temperature plastic flow and the second looking at melt segregation during deformation.

  • Caricchi, L., F. Gaillard, J. Mecklenburgh, and E. Le Trong (2011), Experimental determination of electrical conductivity during deformation of melt-bearing olivine aggregates: Implications for electrical anisotropy in the oceanic low velocity zone, Earth Planet. Sci. Lett., 302(1-2), 81-94.

For more information contact: Julian Mecklenburgh

 

Neutron diffraction studies

This approach allows structural changes during either elastic or permanent rock deformation to be tracked in-situ in substantial rock samples (Steve Covey-Crump, Rob Holloway, Paul Scofield and Iona Stretton (Natural History Museum)).

  • Covey-Crump, S. J., Schofield, P. F. & Stretton, I. C. 2001. Strain partitioning during the elastic deformation of an olivine plus magnesiowustite aggregate. Geophysical Research Letters 28(24), 4647-4650.
  • Covey-Crump, S. J., Schofield, P. F., Stretton, I. C., Knight, K. S. & Ben Ismail, W. 2003. Using neutron diffraction to investigate the elastic properties of anisotropic rocks: Results from an olivine plus orthopyroxene mylonite. Journal of Geophysical Research-Solid Earth 108(B2), art. no.-2092.
  • Dobson, D. P., Mecklenburgh, J., Alfe, D., Wood, I. G. & Daymond, M. R. 2005. A new belt-type apparatus for neutron-based rheological measurements at gigapascal pressures. High Pressure Research 25(2), 107-118.

For more information contact: Steve Covey-Crump or Julian Mecklenburgh

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