ISSN:
1432-0967
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
Notes:
Abstract A number of experimental CO2 solubility data for silicate and aluminosilicate melts at a variety of P- T conditions are consistent with solution of CO2 in the melt by polymer condensation reactions such as SiO 4(m 4− +CO2(v)+Si n O 3n+1(m) (2n+1) ⇌Si n+1O 3n+4(m) (2n+4)− +CO 3(m )2− . For various metalsilicate systems the relative solubility of CO2 should depend markedly on the relative Gibbs free change of reaction. Experimental solubility data for the systems Li2O-SiO2, Na2O-SiO2, K2O-SiO2, CaO-SiO2, MgO-SiO2 and other aluminosilicate melts are in complete accord with predictions based on Gibbs Free energies of model polycondesation reactions. A rigorous thermodynamic treatment of published P- T-wt.% CO2 solubility data for a number of mineral and natural melts suggests that for the reaction CO2(m) ⇌ CO2(v) (1) CO2-melt mixing may be considered ideal (i.e., { $$a_{{\text{CO}}_{\text{2}} }^m = X_{{\text{CO}}_{\text{2}} }^m $$ ); (2) $$\bar V_{{\text{CO}}_{\text{2}} }^m $$ , the partial molal volume of CO2 in the melt, is approximately equal to 30 cm3 mole−1 and independent of P and T; (3) Δ C p 0 is approximately equal to zero in the T range 1,400° to 1,650 °C and (4) enthalpies and entropies of the dissolution reaction depend on the ratio of network modifiers to network builders in the melt. Analytic expressions which relate the CO2 content of a melt to P, T, and $$f_{{\text{CO}}_{\text{2}} } $$ for andesite, tholeiite and olivine melilite melts of the form $$\ln X_{{\text{CO}}_{\text{2}} }^m = \ln f_{{\text{CO}}_{\text{2}} } - \frac{A}{T} - B - \frac{C}{T}(P - 1)$$ have been determined. Regression parameters are (A, B, C): andesite (3.419, 11.164, 0.408), tholeiite (14.040, 5.440,0.393), melilite (9.226, 7.860, 0.352). The solubility equations are believed to be accurate in the range 3〈P〈30 kbar and 1,100°〈T〈1,650 °C. A series of CO2 isopleth diagrams for a wide range of T and P are drawn for andesitic, tholeiitic and alkalic melts.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00375489
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