Fluid inclusion studies on Mt. Capanne pegmatites Isola d'Elba, Tuscany, Italy

Swarms of aplitic-pegmatitic dykes are associated with the peripheral parts of the Tertiary monzogranitic stock of Mt. Capanne. Fluid inclusions in quartz, beryl, and tourmaline crystals from miarolitic cavities and in quartz crystals from massive pegmatites, aplites and monzogranites were examined. By textural and microthermometric criteria, four main types of fluid inclusions were recognized. Inclusion populations I and II are interpreted to represent essentially the same fluid, which is suggested to be dominantly magmatic. By assuming a pressure of 1.5 kbar the calculated trapping temperatures are >=500°C. Crystal-rich inclusions might suggest the presence of a coexisting aluminosilicate hydrous melt. Populations III and IV record later stages of fluid evolution toward lower salinities and temperatures (about 400° and eventually about 300°C assuming a pressure of 1.5 kbar), and possibly indicate an increasing contribution of meteoric fluids.