Melt-mineral-fluid interaction in peralkaline silicic intrusions in the Oslo Rift, Southeast Norway. IV. Fluid inclusions in the Sande nordmarkite.
Abstract
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.