Plastic flow of oriented single crystals of olivine: 2. Observations and interpretations of the dislocation structures


  • W. B. Durham,

  • C. Goetze,

  • B. Blake


In a companion paper we have reported on high-temperature creep data from 41 selectively oriented single crystals of olivine. We report here on a study of the dislocation structures in these specimens by a decoration technique. Forty-two additional specimens were deformed to explore the dislocation multiplication process and glide mobility in the temperature range 1080°–1575°C and differential stress range 80 bars to 2.4 kbars. We report here on these tests as well. All specimens achieved what appeared to be steady state dislocation structures after only a few percent strain. These structures were distinct, repeatable, and diagnostic of particular orientations and slip systems. Under steady state conditions, statistical data for dislocation density, dislocation curvature, and subboundary spacing correlated strongly with differential stress and provided the basis for paleostress estimates of natural specimens. In the range of temperature and stress studied here, climb and glide mobilities were found to be comparable, and creep appeared to be under glide, or joint glide and climb control.