Greisen Systems

Abstract

The term greisen refers to an assemblage of quartz + muscovite, accompanied by varying amounts of other distinctive minerals such as fluorite, topaz and tourmaline. Greisenisation is defined by Shcherba (1970) as the high temperature, post-magmatic alteration of rocks by volatile-rich solutions associated with the cooling of granitic intrusives. Burt (1981, p. 832) defines greisenisation as a “hydrothermally altered granitic rock consisting of a mixture of quartz and mica (normally lithian), with variable topaz, tourmaline, fluorite or other F- or B-rich minerals”. More specifically, Burt (1981) distinguishes “quartz-topaz, quartz-muscovite or mica-fluorite greisen”, defined in terms of the activities of HF and alkalies in alumino-silicate systems.