High-temperature fluid–rock interactions in a layered syenite pluton

Abstract

Variation in mineral composition with stratigraphie height in layered igneous intrusions is generally taken to indicate progressive fractional crystallization, and, following pioneering work on the Skaergaard complex1, petrologists have used this variation in modelling the evolution of magma bodies. In cooling plutons, however, major chemical changes may occur in circulating deuteric fluids2,3. In the Klokken (South Greenland) layered syenite we have discovered that mineral compositions vary both along and normal to the strike of individual layers, and we argue that major chemical changes have occurred in a circulating aqueous fluid constrained to move along relatively permeable high-temperature aquifers in the layered series.