Volatiles in the upper mantle: and experimental approach - Simone Tumiati

Simone Tumiati - University of Milan

Lundi 19 février 2018 à 10 h 30

IMPMC - Sorbonne Université - 4 place Jussieu, 75005 Paris, tour 23, 4e étage, couloir 22-23, salle 401

Abstract

Fluid-mediated processes occurring at the slab–mantle interface can be investigated experimentally. Several experimental studies investigated separately the effect of the volatiles H₂O and CO₂ on subsolidus and melting relations in peridotitic systems at upper-mantle conditions. Only few studies considered the effect of the simultaneous occurrence of H₂O and CO₂ or more generally, the influence of COH fluids on the peridotitic systems. The H₂O/CO₂ ratio in COH fluids is crucial because it affects the location of carbonation/decarbonation reactions and the position of the solidus. However, the H₂O/CO₂ ratio of the fluid in equilibrium with mantle minerals has mainly been estimated through thermodynamic modeling, using equations of state of simple H₂O–non-polar volatile species (e.g., H₂O–CO₂–CH₄), equations that do not consider the complexity related to dissolution processes.
In this seminar we will introduce some methods to produce and analyse fluid-saturated experiments in model systems approaching the slab–mantle interface. In particular we will focus on the measurement of the composition of experimental COH fluids in terms of volatiles and dissolved solutes, and the role of COH fluids in affecting the melting temperatures and the stability of hydrous and carbonate minerals. We will also discuss the role of selected minerals in changing the composition of COH fluids when compared to the simple C-O-H system. Experimental results will be compared to thermodynamic models.