New insights into the formation of the Monte Viso jadeitite, Italy

The Monte Viso Ophiolite complex, situated in the penninic of the Italian Alps, is one of the well studied examples of a subducted oceanic core complex. The serpentinized peridotites comprises enclaves of a wide variety of low temperature, high pressure rocks including eclogites and exceptional rok types such as omphacitite and jadeitites. The occurrence of the jadeitite is particularly intriguing, because the Monte Viso jadeites is one of the only two known examples classified as r-type jadeitites, i.e., formed by metamorphism of a fluid altered protolith.This is a contrast to the jadeitites from China and Myanmar, which formed directly by precipitation from a fluid. This work investigates the formation of these r-type jadeites. Our samples show evidence for the presence of jadeitites in new geological subunit, with significantly different textures. A detailed investigation of the textures and pyroxene composition suggests that original jadeite rich pyroxene can be distinguished from the fluid derived diopside rich crystals. Additionally, a study of the zircons in the jadeitties gives insight into the magmatic protolith, and the degree of fluid alteration in the jadeitites.