Contact metamorphism of layered shale-carbonate sequences in the Oslo Rift: III. The nature of skarn-forming fluids

Intrusions of granitic to monzonitic batholiths caused extensive contact metamorphism of lower Paleozoic sediments in the Permian Oslo rift. The release of aqueous fluids during crystallization of the silicic intrusions resulted in widespread hydrothermal activity leading to skarn formation and locally to ore deposition in the contact aureoles. Stable isotope and fluid inclusion data have been used to constrain the composition and evolution of skarn-forming fluids at a roof pendant situated on the eastern margin of the large Nordmarkite (syenite) batholith at the eastern margin of the Oslo rift. Three different stages of skarn formation, one of them associated with sphalerite mineralization, and subsequent quartz-calcite vein formation have been recognized in the area. A model for the hydrothermal fluid evolution is presented. -from Authors