The campi flegrei (Italy) geothermal system: A fluid inclusion study of the mofete and San Vito fields

Abstract

A fluid inclusion study of core from the Mofete 1, Mofete 2, Mofete 5, San Vito 1, and San Vito 3 geothermal wells (Campi Flegrei, Campania, Italy) indicates that the hydrothermal minerals were precipitated from aqueous fluids ($\text{±CO}{}_2$) that were moderately saline (3–4 wt.% NaCl equiv.) to hypersaline (> 26 wt.% NaCl equiv.) and at least in part, boiling. Three types of primary fluid inclusions were found in authigenic K-feldspar, quartz, calcite, and epidote: (A) two-phase [$\text{liquid (L) + vapor (V)}$], liquid-rich inclusions with a range of salinity; (B) two-phase ($\text{L + V}$), vaporrich inclusions with low salinity; and (C) three-phase [$\text{L + V + crystals (NaCL)}$], liquid-rich inclusions with hypersalinity. Results of microthermometric and crushing studies are reported for twenty drill core samples taken from the lower portions of the five vertical wells.