1. College of Earth Sciences, Jilin University, Changchun 130061, China;
2. Key Laboratory of Mineral Resources Evaluation in Northeast Asia, Ministry of Natural Resources of China, Changchun 130061, China

The temperature, pH, fO₂ and Cl^- activity have been considered to be significant physicochemical parameters which controlled sulphide mineralization. Especially, the change of pH is considered to play one of the key roles in skarn deposit because of the involvement of marble. But few scholars have evaluated the impact of each parameter on mineralization. In this study, the authors have constructed thermodynamic model, calculated the important aqueous species activities in Baiyinnuo'er deposit, and evaluated the influence of these parameters on the solubility of Pb and Zn. The results show that the logfO₂ decreased from -33.834 to -39.256, pH decreased from 4.0 to 3.7 and the Cl^- activity increased from 0.25 to 0.30 in the main mineralization stage. The effect of fO₂ was readily ruled out because the reaction of Pb and Zn precipitation did not involve changes in the valence of the element. The decreased pH was impossible to be a mineralization factor, which was confirmed by metal solubility evaluation. The Cl^- activity was also considered to be a negative factor. In fact, the dominant factor of mineralization was temperature, not the combination of various parameters as previously thought. Even in the skarn stage, the main factor to make the metal solubility >10% was also the high temperature. A significant increase in pH only occurred in the post-ore stage in response to the production of large amount of calcite.