Microstructures

First Previous Section 12 Next Last

Grain Boundary Migration
In-situ deformation of Octachloropropane, C3Cl8

Click image to enlarge

The experiment was performed in the laboratory of Prof. Win Means, SUNY at Albany, using his specially designed deformation rig. A thin film (ca. 60 µm thick) of analogue material (octachloropropane) is sandwiched between two glass slides and then deformed and examined in-situ under a polarizing microscope. Although exact mechanisms of deformation of octachloropropane are unknown, it's microstructures are very similar to those of naturally deformed quartz in thin section.

40. Octachloropropane starting material - Crystallized film of octachloropropane between two glass slides shows equant polygonal grains with straight or slightly curved grain boundaries that meet at 120° triple points. Grains show random extinction.

FOV 0.8mm, Nicols Crossed.

41. 1st. stage of dextral simple shear - Individual grains are still recognizable from image # 40, but now several show undulatory extinction (grain beneath bright yellow grain at left is a good example of this - note that this yellow grain will move to center of next image). Grain to right of central yellow grain has developed a vertical deformation band. Grains also show a very slight sub-vertical elongation.

FOV 0.8mm, Nicols Crossed.

42. 2nd. stage of dextral simple shear - Grains show more undulatory extinction and deformation bands than in previous stage; they are also more elongate and original 120° triple point grain boundaries are severely distorted. Grain beneath central yellow grain (this grain was at left of previous image) has developed a distinct deformation band. Grain boundaries are sutured, especially in lower part of image where strain is locally higher, indicative of grain boundary migration, which occurs where adjacent grains of the same mineral phase have different internal lattice strain. The grain boundary migrates toward the more highly strained region, sweeping lattice imperfections into itself as it moves, and leaves behind a region of strain-free grain.

FOV 0.8mm, Nicols Crossed.

43. 3rd. and final stage of dextral simple shear - Grains are elongate at an oblique angle to the vertical, consistent with dextral shear. Grain beneath central yellow grain has divided into two distinct grains along the previous deformation band boundary. Grain boundaries are very sutured, especially in lower, highly strained part of specimen, indicating that grain boundary migration is occurring.

FOV 0.8mm, Nicols Crossed.

Grain Boundary Migration In-situ deformation of Octachloropropane, C3Cl8	Click image to enlarge
The experiment was performed in the laboratory of Prof. Win Means, SUNY at Albany, using his specially designed deformation rig. A thin film (ca. 60 µm thick) of analogue material (octachloropropane) is sandwiched between two glass slides and then deformed and examined in-situ under a polarizing microscope. Although exact mechanisms of deformation of octachloropropane are unknown, it's microstructures are very similar to those of naturally deformed quartz in thin section.
40. Octachloropropane starting material - Crystallized film of octachloropropane between two glass slides shows equant polygonal grains with straight or slightly curved grain boundaries that meet at 120° triple points. Grains show random extinction. FOV 0.8mm, Nicols Crossed.
41. 1st. stage of dextral simple shear - Individual grains are still recognizable from image # 40, but now several show undulatory extinction (grain beneath bright yellow grain at left is a good example of this - note that this yellow grain will move to center of next image). Grain to right of central yellow grain has developed a vertical deformation band. Grains also show a very slight sub-vertical elongation. FOV 0.8mm, Nicols Crossed.
42. 2nd. stage of dextral simple shear - Grains show more undulatory extinction and deformation bands than in previous stage; they are also more elongate and original 120° triple point grain boundaries are severely distorted. Grain beneath central yellow grain (this grain was at left of previous image) has developed a distinct deformation band. Grain boundaries are sutured, especially in lower part of image where strain is locally higher, indicative of grain boundary migration, which occurs where adjacent grains of the same mineral phase have different internal lattice strain. The grain boundary migrates toward the more highly strained region, sweeping lattice imperfections into itself as it moves, and leaves behind a region of strain-free grain. FOV 0.8mm, Nicols Crossed.
43. 3rd. and final stage of dextral simple shear - Grains are elongate at an oblique angle to the vertical, consistent with dextral shear. Grain beneath central yellow grain has divided into two distinct grains along the previous deformation band boundary. Grain boundaries are very sutured, especially in lower, highly strained part of specimen, indicating that grain boundary migration is occurring. FOV 0.8mm, Nicols Crossed.