High Temperature Creep of Single Crystal Galena (Pbs)

  1. B.E. Hobbs and
  2. H.C. Heard
  1. S. F. Cox

Published Online: 18 MAR 2013

DOI: 10.1029/GM036p0073

Mineral and Rock Deformation: Laboratory Studies: The Paterson Volume

Mineral and Rock Deformation: Laboratory Studies: The Paterson Volume

How to Cite

Cox, S. F. (2013) High Temperature Creep of Single Crystal Galena (Pbs), in Mineral and Rock Deformation: Laboratory Studies: The Paterson Volume (eds B.E. Hobbs and H.C. Heard), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM036p0073

Author Information

  1. Research School of Earth Sciences, The Australian National University, P.O. Box 4, Canberra, A.C.T. 2601, Australia

Publication History

  1. Published Online: 18 MAR 2013
  2. Published Print: 1 JAN 1986

ISBN Information

Print ISBN: 9780875900629

Online ISBN: 9781118664353

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Keywords:

  • Rocks—Testing—Addresses, essays, lectures;
  • Rock deformation—Addresses, essays, lectures

Summary

The creep behavior of several types of natural and synthetic galena single crystals has been tested during <100> compression at stress differences from 3 MPa to 125 MPa, in the temperature range 265°C to 650°C, and at strain-rates ranging from 10−2 s−1 to 10−8 s−1 . There are significant differences in flow laws between the various natural and synthetic crystals tested. The observed variations in creep rate between the crystals examined may be due largely to the influence of stoichiometric defects and dopant additions in controlling both the energy of formation of kinks and jogs, as well as the concentrations and mobilities of rate limiting defects.

At applied stresses greater than 60 MPa and at temperatures between 265°C and 375°C, creep of natural galena from Broken Hill (New South Wales) may be described by a power law in which the stress exponent has values around nine and the creep activation energy is approximately 145 kJ mol−1. Deformation occurs dominantly by $$\{ 110\} < 1\bar 10 >$$ dislocation glide. At lower applied stresses and higher temperatures the power law stress exponent decreases to values around six and the creep activation energy increases to between 170 kJ mol−1 and 200 kJ mol−1 . Dislocation climb becomes active and leads to the development of a subgrain structure at low strains. At 540°C natural galena from Que River (Tasmania) has a power law stress exponent similar to that of the Broken Hill galena. However the Que River galena creeps at a rate twenty-five times slower than the Broken Hill galena, and has a significantly higher creep activation energy than the latter.

With decreasing applied stress below about 40 MPa, and at temperatures greater than 450°C, melt-grown synthetic galena has an increase in power law exponent from values around six to values around nine. There is a corresponding increase in creep activation energy from approximately 200 kJ mol−1 to values higher than 300 kJ mol−1 in one of the synthetic galenas.

Comparison of a point defect analysis for pure and doped galena with previously published data on the dependence of creep rate on sulfur vapor pressure and foreign atom additions suggests that in pure PbS high temperature dislocation creep may be rate-controlled by the migration of charged jogs along dislocations, coupled with diffusion by vacancy mechanisms. In Ag− and Bi-doped PbS high temperature creep may be similarly rate-controlled by jog migration and vacancy-diffusion. However under some circumstances deformation may be rate-limited by drift of kinks along dislocations.