The effect of compression on noble gas solubility in silicate melts and consequences for degassing at mid-ocean ridges

A new view of the He–Ar–CO2 degassing at mid-ocean ridges: Homogeneous composition of magmas from the upper mantle

“…The signature of the Rayleigh process is actually a straight line whose slope depends on the He/Ar and Ar/CO 2 solubility ratios (k He /k Ar and k Ar =k CO 2 , where k i is expressed in moles i kg À1 Pa À1 ). In basaltic melts, the solubilities of both He and CO 2 are much higher than that of Ar, being the values of k He /k Ar and k Ar =k CO 2 usually considered around 10 and 0.2, respectively (see the review by Paonita, 2005;Guillot and Sarda, 2006). Whilst the slope computed with these solubility ratios matches the data trends (see Fig.…”

“…Single-stage, closed-system equilibrium approaches have needed to use He, Ne and Ar solubilities very different from those measured experimentally (Sarda and Graham, 1990;Moreira and Sarda, 2000;Sarda and Moreira, 2002). Explanations of the abundances of C, N and noble gases and their isotopes have included two-or three-stage degassing process, characterized by closed-system behaviour during magma migration to intracrustal magma chambers, followed by open-system conditions in the chamber (Bottinga and Javoy, 1989;Gerlach, 1989;Pineau and Javoy, 1994;Cartigny et al, 2001;Burnard et al, 2003;Sarda and Guillot, 2005;Guillot and Sarda, 2006). Other authors have included only Rayleightype degassing (Marty, 1995;Marty and Tolstikhin, 1998;Marty and Zimmermann, 1999;Nishio et al, 1999;Burnard, 2001;Burnard et al, 2002Burnard et al, , 2004Yamamoto and Burnard, 2005).…”

A computer simulation study of natural silicate melts. Part I: Low pressure properties

“…An interesting consequence of the above trend is that the solubility of a chemically inert volatile (e.g. rare gases) in these silicates is primarily governed by the free volume accessible to the solute into the melt (Guillot and Sarda, 2006) i.e., the smaller the molar volume of the melt the smaller the solubility of the volatile. Consequently, one expects that the solubility of a weakly interacting solute (e.g.…”

Coordinated Hard Sphere Mixture (CHaSM): A simplified model for oxide and silicate melts at mantle pressures and temperatures

“…Despite the limitations of the empirical procedure employed by both Jing and Karato (2011) and Guillot and Sarda (2006), these studies demonstrated the potential power of the hard sphere model for describing pressure-, temperature-, and composition-dependent trends for oxide and silicate melt properties. These investigators used the HS model as a physically-motivated averaging kernel, allowing them to interpolate within the fitted dataset.…”

“…The first notable application to geologic systems was presented by Guillot and Sarda (2006), where the compression of MORB, silica, and olivine composition liquids up to 10 GPa were modeled to investigate high-pressure noble gas solubility. The effective hard sphere sizes were determined empirically by fitting 1 bar melt density measurements.…”