Skarn association from pegmatite/marble contact in NW Rila: occurrence and composition of F-enriched vesuvianite

Calcic skarns are formed on the pegmatite/marble contact in the region of Dzhendemski Ezera, NW Rila, Bulgaria. The garnet/vesuvianite-dominated association is formed in the marbles of the Malyovitsa Lithotectonic Unit as a result of emplacement of crosscutting pegmatite injections. Large (up to 3 cm) prismatic vesuvianite crystals and their radiating aggregates are associated with garnet masses, diopside, scapolite, and zoisite. Representative samples were selected for mineralogical and geochemical study, focused on the vesuvianite composition and its associated minerals. Significant incorporation of fluorine is an important compositional characteristic in vesuvianite and garnet evidencing for the fluid/rock interaction and diffusion-involved bimetasomatic processes due to pegmatite intrusion. Trace-element signatures of the skarn minerals reveal constant isomorphic incorporation of large set of elements including V, Zn, Ga, Ge, Sn, Ni, Bi, REE, HFSE, U.