Pressure shadow
A pressure shadow (also called strain shadow) is a term used in metamorphic geology to describe a microstructure in deformed rocks that occurs adjacent to a relatively large, undeformed particle, such as a porphyroclast. Pressure shadows often appear in thin sections as pairs of roughly triangular regions that are elongated parallel to the foliation around a clast of a different mineral.[1]. Pressure shadows that contain fibrous mineral textures are also termed pressure fringes or strain fringes.
Pressure shadows regions (indicated by dashed lines) around porphyroclasts in a deformed granodiorite.
Formation
During deformation, minerals can migrate by plastic flow or may grow by diffusive mass transport into the lower-stress regions created by a rigid porphyroclast or porphyroblast.[2]
gollark: Unless it doesn't.
gollark: Anyway, many of the bugs in potatOS come from stuff like the SPUDNET daemon not being subject to sandboxing, so people can fake events and stuff going to that in increasingly convoluted ways to make it execute code when it shouldn't.
gollark: It was used to provide sandboxed copies of potatOS for testing and stuff.
gollark: Or crane, my really, *really* broken sandboxingish thing.
gollark: Well, it sort of is, in that it complains lots if you try and delete SYSTEM32.
References
- Passchier and Trouw (2005). Microtectonics (2nd ed.). Springer. ISBN 9783540293590.
- Blenkinsop, T.G. (2007). Deformation Microstructures and Mechanisms in Minerals and Rocks. Kluwer Academic Publishers. p. 150. ISBN 030647543X.
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