G. Giuli, R. Alonso-Mori, E. Paris, P. Glatzel, S. Eeckhout, M. Carroll, School of Science and Technology, Geology Division, University of Camerino, Via G. III da Varano, 62032 Camerino; e-mail:
The solubility behaviour of S and Cl in silicate magmas is a key to understand the processes affecting S and Cl volcanic emissions in the atmosphere. The geochemical behaviour of these elements in silicate melts and glasses is also of major importance for problems ranging from volcano-climate interactions to the genesis of ore deposits of great economic importance to industrial glass-forming processes and vitreous waste material from refuse incineration. As a consequence, many authors studied the solubility of these elements in silicate melts as a function of composition, temperature, pressure and redox conditions. However, little is known on the extent to which the structure of silicate melts and interaction between S and Cl with metal cations affect their solubility behaviour. Evaluation of such problems requires new data on the structural and chemical environments around S, Cl dissolved in silicate melts and potential interactions with metal cations like Fe.
As silicate glasses can be considered good structural analogue of the melts near the glass transition temperature, we can study the structural environment of S, Fe and Cl in synthetic silicate glasses to infer their behaviour in natural magmas of the same composition and to draw relationships between their structural environment in the glass and their solubility.
This project involve the synthesis of silicate glasses with different bulk compositions pressures, temperatures and at controlled redox conditions in the aim of determining how these variables affect both the Fe oxidation state and structural environment and volatiles solubility. X-ray Absorption Spectroscopy (XAS) and X-ray Emission Spectroscopy (XES) are element selective techniques that allow to determine the oxidation state and structural environment1,2 and can provide the information we need to rationalise the solubility data of volatiles in magmas. Recent data3 allowed us to ascertain that the solubility of S2- in magmas is greatly affected by the concentration of Fe2+.
References
1) Paris E.; Giuli G.; Carroll M.; Davoli I. Canadian Mineralogist, 2001, 39, 331-339.
2) Mori R.; Paris E.; Giuli G.; Eeckhout S.; Kavcic M.; Zitnik M.; Bucar K.; Pettersson L.; Glatzel P. Analytical Chemistry, 2009, 81, 6516-6525.
3) Giuli G.; Mori R.; Cicconi R.; Paris E.; Glatzel P.; Eeckhout S.; Scaillet B. American Mineralogist 2011 subm.
