Melt-mineral-fluid interaction in peralkaline silicic intrusions in the Oslo Rift, Southeast Norway. III. Alkali geothermometry based on bulk fluid inclusion content.
Abstract
Decrepitation-linked ICP analyses of bulk fluid inclusion in quartz in 14 samples from the Sande nordmarkite (quartz syenite) and the Eikeren Skrim ekerite (alkali granite) plutonic complexes yield Na\/K ratios which suggest equilibration between aqueous fluid and the host rock at temperatures in the range 240-340\u00B0C. This is far below the estimated solidus ( 700\u00B0C), but can be correlated with the trapping of late, secondary fluid conclusions. The data thus demonstrate the importance of low-temperature sub-solidus fluid interaction processes for the petrogenesis of the Oslo region felsic intrusive rocks.