关键词: 水-岩反应过程, 水-岩作用机理, 热力学模拟, 蚀变-矿化, 焦家金矿床

Abstract: On the basis of detailed analysis of the alteration-mineralization time series of the Jiaojia gold deposit, and the correlative
theory of chemical thermodynamics and chemical reaction, a solid phase titration model of water-rock interaction in Jiaojia gold deposit
is established. In addition, we discussed the precipitation order, existence form, migration behavior, and concentration change of
ore-forming fluid components by using numerical simulation of thermodynamics. we further discussed the relationship between
water-rock interaction and gold mineralization. The results show that the potash feldspathization occurred at the initial stage of the
reaction due to the K+ flow into the surrounding rocks from the fluid, the concentration of Fe2+ and Al3+ increased with the continuous
reduction of H+ concentration along with proceeding of the water-rock interaction. Sericite and quartz heavily precipitated with the
disappearance of potassium feldspar, followed by precipitation of the sulfide minerals. The content of SO42-, HS- and Fe2 + in the
ore-forming fluid has a great influence on the alteration mineral assemblage, the reduction of sulphate (SO42-) and the formation of the
same amount of HS-, which was accompanied by the precipitation of ferric minerals during the process of water-rock reaction. This may
be an important mechanism of sulfide precipitation in Jiaojia gold deposits. The continuous increase of pH value during the whole
reaction process is due to the exchange of Ca, K, Na and Mg in the original rock with H+ in the solution. Also, the increased pH value
reduces the solubility of gold, resulting in Au precipitation. These results provide a new basis for understanding the mineral
assemblage, sequence of formation, and the genetic mechanism of altered zonation

Key words: process of water-rock interaction, mechanism of water-rock interaction, thermodynamic simulation, alteration-mineralization;Jiaojia gold deposit