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Cathodoluminescent image of granite with minerals intergrown with each other
A cathodoluminescence image of ~1.12 to 1.07 billion-year-old granite with two minerals intergrown with each other. The granite came from Town Mountain Granite in Llano, Texas. The bluish cross-hatched area is occupied by a grain of potassium feldspar (microcline), and the purple red-rimmed mineral in the upper half of the image is a grain of sodium feldspar (albite). Both mineral grains grew as the granite slowly, then melted, cooled and crystallized. The black areas were altered by low temperature fluids that circulated through the granite after it had solidified and may also be late filled fractures and cavities (fluid inclusions). The reddish areas probably were altered and invaded by sodium feldspar at a later time, when younger granites intruded the already solidified Town Mountain Granite and led to circulation of hot water (hydrothermal fluids) along fractures and grain boundaries.
This research was supported by National Science Foundation grant EAR 0318769, awarded to Juergen Schieber, Department of Geological Sciences, Indiana University. (Date of Image: Aug. 17, 2005)
Credit: Image by Juergen Schieber, Department of Geological Sciences, Indiana University. Instrumentation: SEM FEI Quanta-FEG 400 with Gatan Chroma CL.
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