The formation of metasomatic reaction veins in dolomitic marble roof pendants in the Bergell intrusion (Province Sondrio, northern Italy).

Abstract

The most abundant of the various vein types found among these symmetrically-zoned reaction veins consists of amphibole + calcite zones whose internal banding is due to discontinuous changes in amphibole composition. The discontinuous composition profile supports the conclusion that the transport process responsible for formation of many of the zones was infiltration metasomatism. Both deposition of material along an opening central fracture, and reaction of a SiO2-rich aqueous fluid with adjacent dolomitic marble, were probably involved in the process. -M.S.