Abundance and water signification in primary magmas. Micro-Raman and micro-Ftir spectroscopies.

The objective of this work was to study the dissolve water behaviour in olivine-hosted melt inclusions. This kind of work requires an analytical method with high spatial resolution which allows fast and accurate large data base acquiring on melt inclusions. In this way, this work was firstly dedicated on micro-Raman spectroscopy development. Thus we finally propose a method which allows to control and to predict the matrix effects that affect the water content determination (GCA, 2009 and Chemical Geology, 2009). Then, this method has been tested on a large range of natural (melt inclusions) mafic compositions (from trachy-basalt to basanite) and validated with an FTIR comparison (GCA, submitted). The new molar absorptivity coefficients determined for mafic composition and literature data allow us to identify the evolution of this coefficient with composition. The final part of this work is about the H2O behaviour in primary silicate melts through the olivine-hosted melt inclusions from La Sommata (Vulcano, Aeolian Arc). After a sampling field work, an accurate study of melt inclusions and their hosted mineral compositions (major and volatiles elements) have been performed in natural state or after heating experimentation (1200-1250°C). The chemical and isotopic results (äD) show the melt inclusions reliability to trace the primary and hydrated nature of magmas in subduction zone.