Wollastonite solubility and free energy of supercritical aqueous CaCl2

✍ Scribed by W. D. Gunter; H. P. Eugster

• Book ID: 104746633
• Publisher: Springer
• Year: 1978
• Tongue: English
• Weight: 937 KB
• Volume: 66
• Category: Article
• ISSN: 0010-7999
• DOI: 10.1007/bf00373411

✦ Synopsis

The solubility of wollastonite in chloride solutions has been measured between 750~ and 850~ at 2kb pressure and at 800~ at 1 kb pressure. The fugacity of HC1 at P and T was controlled by combining Ag+AgC1 internally with magnetite +hematite+water as an external hydrogen buffer. Silica activity was fixed by the presence of quartz. The calcium and chloride contents of the solutions were measured after quench. CaC12 appears to be the major solute species.

Using these compositional data, the Gibbs Free Energy of formation for CaC1 a was calculated, assuming that the activity coefficient quotient is near unity. The results were combined with quartz solubility data and calculations made by Joesten (1974) to approximate the compositions of CO2--H20 rich fluids which prevailed during the metasomatic formation of monominerallic zones in calc-silicate nodules from a contact aureole in the Christmas Mountains, Texas. The largest predicted gradients in H4SiO ~ and CaC12 occur across the wollastonite zone.