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| Click on image to enlarge. Photo © Daniel R. Snyder |
This image illustrates the cataclastic texture described by Ragan (1963)*. The large subhedral olivine grain is inferred to have formed in the "primary"phase, during which the relatively intact igneous body was emplaced in the crust in the solid state. Subsequent strain resulted in the deformation banding seen in many of the grains, the strain lamellae in the large grain, and the fracturing that produced the mosaic of small grains. Later recrystallization of some small grains caused the strain features to be eliminated, as in the tight cluster at the lower right, where each of the grains shows a uniform interference color. Cascade Mountains, Whatcom County, northwestern Washington. XPL. Imaged area 2.7 mm x 4 mm. Link to Dan McShane's Twin Sisters page.
*D.M. Ragan (1963), Emplacement of the Twin Sisters Dunite, Washington, American Journal of Science, v. 261, p. 549-565.
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