Metasomatic phase relations in dolomites of the Adamello Alps.

Abstract

Lateral changes in mineral chemistry, relative mineral abundances, and fluid compositions in veins adjoining wall-rocks in the contact zone of Tertiary quartz diorite intrusives with these Triassic dolomites of northern Italy, were studied. The extent to which chemical components have been introduced, removed, and/or redistributed during metasomatism was calculated. Formation of metasomatic veins associated with the intrusive contacts is attributed to lateral mass transfer by diffusion to and from a flowing CO2-poor fluid in a fissure system at the contacts. The process occurred with little volume change at relatively low-T and fluid pressure.-M.S.