Exoskarns represent the alteration zone outside the intrusive and endoskarns are formed within the intrusive body. Fluids for exoskarns are derived from the intrusive. Fluid inclusions in ore or gangue minerals often contain solid salt crystals, indicating that the mineralizing fluids were highly saline.
In Petrographic Reports on skarns it is important to distinguish between endo and exoskarns, to characterize mineral zonation and to estimate the temperature gradient from the alteration assemblages. A series of detailed studies on skarns by GeoConsult includes the Nuestra Senora Zn-Ag mine in Mexico and the Rosemont Cu-Mo-Ag deposit in Arizona, US.
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(x-axis of photos: 1.6mm)