Program > Browse abstracts by speaker > Condamine Pierre

The study of magmas that reach the surface, lavas and pyroclastic products, reveals that magmas consist mainly (excluding carbonatitic magmas) of partially crystallized silicate liquids containing few volatile elements (primarily H₂O). These volatiles are often partially or completely exsolved as gases by the time the magma reaches the surface. Consequently, volcanic glasses are typically highly degassed, making it challenging to quantify the original volatile content dissolved in the magma. This is critical because volatiles play a key role in controlling magma properties, such as viscosity, ascent rate, and explosivity. A notable exception is volcanic glasses preserved as primary melt inclusions within crystals, which remain largely undegassed. These inclusions are naturally trapped samples of magma before degassing, making them valuable for determining the original volatile content and true composition of magmas.

However, the use of melt inclusions as proxies for primary magma compositions is complicated by post-entrapment processes that can alter their volatile and chemical signatures. These processes raise questions about the reliability of melt inclusions for determining (i) the role of volatiles in ascending magmas and (ii) the evolution of Earth's mantle. This study aims to investigate the evolution of water within a melt inclusion trapped in an olivine crystal throughout its entire lifespan, from entrapment to analysis.

For this purpose, dynamic forsterite crystallization experiments were conducted in the CaO–MgO–Al₂O₃–SiO₂–H₂O system using a piston-cylinder apparatus at 1 GPa. Starting above the liquidus, the experiments employed a slow cooling rate to ensure the entrapment of primary melt inclusions during the growth of polyhedral olivine crystals. These carefully controlled experimental conditions provide critical insights into the formation of melt inclusions and the significance of their volatile and chemical compositions, advancing our understanding of how primary volatile contents influence magmatic behavior and Earth's mantle evolution.