Crustal Structure of the Ischia-Phlegrean Geothermal Fields, Near Naples, Italy, From Gravity and Aeromagnetic Datat

The crustal structure and thermal regime of the Ischia-Phlegrean Fields volcanic area (Naples, Italy) have been intensively studied using gravity and aeromagnetic data. Analysis and interpretation of the data indicate that there often exists a complicated relation between density, magnetization and temperature. In particular, thermal effects, such as thermal demagnetization and thermal mineral alteration, may play an important role locally and could be the possible sources of the observed magnetic anomalies. Taking into account the poor correlation between the magnetic and gravity fields, the different magnetic and gravimetric responses have been used to provide a basic structural and thermal description of the area. Two interpretations are proposed. In the first the anomalies are related to compositional discontinuities in the intermediate-deep crust; in the second they are related to deep thermal sources, such as partially melted trachybasalts (gravity field) and a local rise of the Curie point surface (magnetic field).