Crack-seal Veins
When the confining pressure is too great, or when brittle-ductile rheological conditions predominate, vein formation occurs via crack-seal mechanisms.
Crack-seal veins are thought to form quite quickly during deformation by precipitation of minerals within incipient fractures. This happens swiftly by geologic standards, because pressures and deformation mean that large open spaces cannot be maintained; generally the space is in the order of millimetres or micrometres. Veins grow in thickness by reopening of the vein fracture and progressive deposition of minerals on the growth surface.
Read more about this topic: Vein (geology)
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