Melt-mineral-fluid interaction in peralkaline silicic intrusions in the Oslo Rift, Southeast Norway. IV. Fluid inclusions in the Sande nordmarkite.
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The mildly peralkaline Sande nordmarkite (quartz syenite) intrusion contains interstitial quartz and mafic minerals (alkali amphibloe, ilmenite, titanomagnetite, zirkon, sphene + calcite). Three generations of fluid inclusions have been recognized in the interstitial quartz: primary inclusions (population), early secondary inclusions (population 2) and late secondary inclusions (population 3). Population 1 and 2 inclusions contain fluids which can be approximated by the H2O-NaCl system, and were probably derived from the magma. The salinity of these fluids is ca. 40 wt% NaCl, but the fluidsd show a considerable variation in density (d = 0.9 to > 1.1 g\/cm3), increasing with time and decreasing temperature. Population 3 fluids show complex immiscibility relationships involving vapour, highly saline liquids and solid salts. Also, low-salinity, high-density fluids of external origin become important at this stage.