Noble gases: Hide and seek from volcanoes to ice | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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  Noble gases: Hide and seek from volcanoes to ice

Mardi 15 Mai 2018
Séminaires Géochimie
Julien Amalberti
(University of Michigan)
Extrait: 

Influence of volatile species on the operation of the mantle, which controls the storage and release of volatiles to the surface, is a critical component of our understanding of the Earth system on a grand scale. Our current knowledge of the volatile exchange between the mantle and the atmosphere shows a strong connection between the continuous degassing at the oceanic ridges and the recycling through the subduction zone. This exchange between internal and external layers of the Earth control and shape the evolution of the continental crust, oceans, atmosphere and the habitability of the planet. In the study of volatile exchange between internal and external layers, the magma degassing is a fundamental process of modern volcanology, with far-reaching implications for eruption dynamics, the environmental impact of volcanism, and the global cycle of volatile elements. Products of volcanic eruptions (i.e., fluid inclusions, vesicle-bearing glasses) are precious indicators of the geological history of Earth degassing. Knowing the pre-degassed content of the volatile is critical for characterizing a mantle signature and its evolution through time. However, several physical processes can affect the volatile content within a vesicle (i.e., magma reinjection, rapid decompression, fast quenching, different degassing paths (closed or open) and atmospheric contamination). Despite intensive studies of degassing-induced fractionation, the interpretations are currently limited by the lack of experimental constraints. Thus, I present the use of key volatile trace elements that are markers of magma degassing: the noble gases. I use a combination of experimental petrology, geochemistry of noble gas and numerical modelling to investigate the complex processes responsible for the observed noble gases concentration in eruption products. Quantification of the noble gas budget within the mantle brings critical information on the global cycle of mantle geodynamics.