Geochemical study of the Solchiaro (Procida Island, Campi Flegrei) eruptive products by microthermometry and microanalysis of fluid and melt inclusions

In this study is presented the work I have done during the 4 years of a PhD program that was part of the internationalization programme of the Italian research system approved by the Ministero della Ricerca e dell’Università (MIUR) between the Università degli Studi di Napoli “Federico II”, (Dipartimento di Scinze della Terra) and the Virginia Polytechnic Institute and State University (Department of Geosciences). 107 selected MI, 77 open glasses, 80 olivines and 7 bulk rocks (from 4 representative samples of Solchiaro eruption) were analyzed for major/trace element and volatiles. Mostly, olivine compositions vary from Fo82 to Fo88 with one maximum value of Fo90. 2 group of MI were recognized based on major element composition: 1) K2O-rich MI with composition that is the same of bulk rock in the literature and 2) K2O-poor MI that instead have been never reported from previous study of the PVD (Phlegrean Volcanic District). The first group consists of 95% of the melt and relates mostly to within plate setting whereas the second group consists of around 5% of the melt and relates to subduction setting. Magma associated with Solchiaro eruption evolved under open system processes as suggested by petrographic evidence and glass compositions. H2O-CO2 concentrations dissolved in glass suggest that magma was saturated in volatiles at least at 12.5 km depth and continuously degassed during the Solchiaro eruption. Maximum depths are in agreement with other studies based on different approaches. Volatile correlations suggest that during closed system degassing, as the Solchiaro eruption progressed, maximum S contents decreased and minimum Cl and F contents increased. The major, trace and volatile evolution of crystals, glass, and MI is consistent with a model that involves either continuous or episodic recharge of the magma chamber ponded at least at 12.5 km depth