Evolution of a Skarn Deposit

Evolutionary stages of pluton-associated skarn deposits: A) Initial intrusion causes metamorphism of sedimentary rocks. B) Metamorphic recrystallization and phase changes reflect protolith compositions with local bimetasomatism and fluid circulation forming diverse calc-silicate minerals (reaction skarns and skarnoid) in impure lithologies and along fluid boundaries. Note that metamorphism is more extensive and higher temperature at depth than adjacent to the small cupola near the top of the system. C) Crystallization and release of a separate aqueous phase result in fluid-controlled metasomatic skarn. Note that skarn at depth is small relative to the size of the metamrophic aureole. It is also vertically oriented compared to the laterally extensive skarn which locally extends beyond the metamorphic aureole near the top of the system. D) Cooling of the pluton and the possible circulation of cooler, oxygenated meteroic waters cause retrograde alteration of metamorphic and metasomatic calc-silicate assemblages. Note that retrograde alteration is more extensive in shallow zones.

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Last Updated: December 21, 1995