Pumpellyite veins in the metadolerite of the Frido Unit (Southern Apennines - Italy)

摘要

This study focuses on pumpellyite veins cross-cutting the metadolerites of the Frido Unit Ophiolites (Southern Apennines - Italy). Pumpellyite occurs in the metadolerites as feltradiated aggregates or prism filling veins; metadolerites show mineral assemblages of the prehnite-pumpellyite and lawsonite-glaucophane metamorphic facies. Texture and composition of minerals in these veins are heterogeneous as revealed by SEM and EMPA characterisations, respectively. Either in the host rocks and in the veins, mineral compositions indicate a polyphase metamorphic evolution; these metadolerites recorded both the oceanfloor metamorphism and their emplacement within the Liguride accretionary wedge (HP/LT). In particular, the Fe and Mg amounts in the pumpellyite crystallised in the veins ranges between 0.216-0.585 and 0.293-0.466 apfu, respectively, whereas Al ranges between 2.518-2.802 apfu. These compositional variations reflect a similar metamorphic evolution of the host rock and pumpellyite veins of the Frido Unit.