The effect of volatiles on the properties of magmatic melts
Persikov, Edward S.; Zharikov, Vilen A.; Bukhtiyarov, Pavel G.
European Journal of Mineralogy Volume 2 Number 5 (1990), p. 621 - 642
published: Oct 4, 1990
manuscript accepted: May 3, 1990
manuscript received: Oct 18, 1989
ArtNo. ESP147050205007, Price: 29.00 €
Abstract Systematic experimental studies have been undertaken to study the effect of volatiles (H2O, H2O + HCl, H2O + NaCl, H2O + HF, H2, Ar) on the rheological properties (η - the viscosity ; E - the activation energy of viscous flow) of acid-base magmatic and model melts. Also studied were the H2 diffusive mobility, H2 and H2O solubility in the melts and the effect of PH2O on albite melting. Experimental conditions were: Pfl= 1 atm - 7 kbar, T = 750-1400°C. The H2 solubility in the albite melt (T = 1300°C) is two orders of magnitude lower than the H2O solubility, and about twice as high as that of CO2. These findings are thermodynamically consistent with the fact that the albite melting temperature decreases considerably under H2 pressure (at PH2 = 5 kbar ΔT = - 80°C). The H2 diffusive mobility in magmatic melts is about two orders of magnitude higher than DH2O and about six orders of magnitude higher than that of SiO2. The results obtained have been used to derive the general viscosity patterns in magmatic melts and to study new facets of the interaction of volatiles (H2O, H2, F, Cl) and melts. A new model for calculation of η and E in the complete series of magmas, from acid to ultrabasic, is discussed.