1456 articles – 350 Notices  [english version]
Fiche détaillée Articles dans des revues avec comité de lecture
European Journal of Mineralogy 21, 1 (2009) 107-116
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Estimation of pre-eruptive magmatic water fugacity in the Phlegrean Fields, Naples, Italy
Alessandro Fabbrizio1, Bruno Scaillet2, Michael R. Carroll3

We estimated the water fugacity (fH(2)O) in the trachytic magma of Phlegrean Fields using the biotite-magnetite-sanidine equilibrium. We confirm that the partly ionic model is the most appropriate to estimate annite activity (a(annite)) for the experimental biotite. Crystallization experiments were carried out on a representative sample of trachytic Breccia Museo eruption, Naples, Italy. Experiments were performed in the temperature and pressure range or 725-870 degrees C and 50-200 MPa, and redox conditions ranging from NNO (nickel- nickel oxide) + 1 (+/- 0.2) to FMQ (fayalite + magnetite + quartz). Most experiments were done under conditions of H2O saturation (P-water = P-total). Few experiments were done using a mixed H2O-CO2 fluid phase. The pre-eruptive fH(2)O of the Phlegrean Fields magma is estimated at 735 bars, which compares well with available melt inclusion constraints. Our results confirm that this geohygrometer can be used in any magmatic systems bearing the worked assemblage.
1 :  ETH - Departement Erdwissenschaften, ETH-and University Zürich
2 :  ISTO - Institut des Sciences de la Terre d'Orléans
3 :  Dipartimento di Scienze della Terra
crystallization experiments – geohygrometer – trachytic magmas – water fugacity