Microcracking and Healing in Granites: New Evidence from Cathodoluminescence

Quartz grains in granitic rocks usually have blue cathodoluminescence (CL). Within the blue-luminescing grains, there are often red-luminescing domains which are frequently impossible to detect without CL contrast. This finding suggests that the red-luminescing quartz is sealing preexisting microcracks. The presence of these now-healed microcracks has important implications with respect to the role of pore fluid pressure and fluid transfer in metamorphism, the origin of granites, long-period crustal deformation, earthquake mechanics, physical properties of rocks, and deep-seated geothermal energy.