Numerical modelling of CO2-water-basalt interaction

Abstract The effects of CO2 on water-basaltic glass interaction have been simulated at 25ºC. The calculations indicate that addition of CO2 (2–30 bar) to water significantly changes the reaction path. Initially, the pH is buffered between 4 and 6 by CO2 ionization, with dissolution of basaltic glass and the formation of secondary minerals with SiO2, Mg-Fe carbonates and dolomite predominating. Upon the dissolution of additional basaltic glass and mineral fixation of CO2, the pH increases to >8 and (Ca)-Fe-Mg smectites, SiO2, Ca-Na zeolites and calcite become the dominant secondary minerals forming. The overall reaction path depends on the initial water composition, reactive surface area, and the composition of the phyllosilicates and carbonates forming. The key factors are the mobility of Mg2+, Fe2+ and Ca2+ and the competing reactions for these solutes among secondary minerals.

[1]  D. Wesolowski,et al.  Aqueous high-temperature solubility studies. II. The solubility of boehmite at 0.03 m ionic strength as a function of temperature and pH as determined by in situ measurements , 2001 .

[2]  David J. Wesolowski,et al.  Aqueous high-temperature solubility studies. I. The solubility of boehmite as functions of ionic strength (to 5 molal, NaCl), temperature (100–290°C), and pH as determined by in situ measurements , 2001 .

[3]  S. Gíslason,et al.  The mechanism, rates and consequences of basaltic glass dissolution: I. An experimental study of the dissolution rates of basaltic glass as a function of aqueous Al, Si and oxalic acid concentration at 25°C and pH = 3 and 11 , 2001 .

[4]  S. Ariya,et al.  THERMODYNAMICS OF IRON OXIDES , 1963 .

[5]  K. Rogers,et al.  CO2 metasomatism in a basalt-hosted petroleum reservoir, Nuussuaq, West Greenland , 2006 .

[6]  S. Gíslason,et al.  CHEMICAL WEATHERING OF BASALTS, SOUTHWEST ICELAND: EFFECT OF ROCK CRYSTALLINITY AND SECONDARY MINERALS ON CHEMICAL FLUXES TO THE OCEAN , 2001 .

[7]  V B Parker,et al.  Thermodynamic Properties of the Aqueous Ions (2+ and 3+) of Iron and the Key Compounds of Iron , 1995 .

[8]  Y. Tardy,et al.  An ideal solid solution model for calculating solubility of clay minerals , 1981, Clay Minerals.

[9]  Udo Schwertmann,et al.  Thermodynamics of iron oxides: Part III. Enthalpies of formation and stability of ferrihydrite (~Fe( , 2004 .

[10]  S. Arnórsson,et al.  POROSITY EVOLUTION AND MINERAL PARAGENESIS DURING LOW-GRADE METAMORPHISM OF BASALTIC LAVAS AT TEIGARHORN, EASTERN ICELAND , 1999 .

[11]  S. Gíslason,et al.  Mechanism, rates, and consequences of basaltic glass dissolution: II. An experimental study of the dissolution rates of basaltic glass as a function of pH and temperature , 2003 .

[12]  Roger Powell,et al.  An internally consistent thermodynamic data set for phases of petrological interest , 1998 .

[13]  A. Stefánsson,et al.  Dissolution of primary minerals of basalt in natural waters , 2001 .

[14]  D. L. Parkhurst,et al.  User's guide to PHREEQC (Version 2)-a computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations , 1999 .

[15]  Ingvi Gunnarsson,et al.  Amorphous silica solubility and the thermodynamic properties of H4SiO°4 in the range of 0° to 350°C at Psat , 2000 .

[16]  V. A. Medvedev,et al.  CODATA key values for thermodynamics , 1989 .

[17]  P. G. Hill.  A UNIFIED FUNDAMENTAL EQUATION FOR THE THERMODYNAMIC PROPERTIES OF H2O , 1990 .