黑龙江乌拉嘎金矿成矿热力学参数研究

A study of thermodynamic parameters of the Wulaga gold deposit,Heilongjiang Province

本文通过对前人工作的总结,在研究矿物共生关系的基础上将乌拉嘎金矿床的成矿作用过程划分为3个成矿阶段,然后利用热力学数据计算出了各个阶段的成矿热力学参数。第1阶段:黄铁矿-早期白色玉髓状石英阶段,Eh范围在-0.5^+0.3 V之间,处于弱还原环境,硫逸度应大于10^(-23);第2阶段:烟灰色玉髓状石英-多金属硫化物阶段,在低温时成矿环境为中酸性(pH=4),弱还原环境(Eh值为-1.0^-0.3 V),硫逸度范围应大于10^(-40),但不会超过10~0。同前一阶段相比,硫逸度下限降低;第3阶段:碳酸盐-石英阶段,碳酸盐矿物的出现预示着成矿已接近尾声,成矿介质的pH值逐步从酸性(pH=3)向中酸性(pH=5)转变,成矿Eh值也从弱还原(-0.5 V)向弱氧化(+0.3 V)过渡,硫逸度下限范围大约在10^(-23)左右,不超过10~0,而氧逸度范围在10^(-20)加左右。这对于深入探讨热液成矿作用过程具有重要参考价值。

Based on a study of mineral paragenetic relationship in combination with results obtained by previous researchers, the authors divided the metallogenic process of the Wulaga gold deposit into three ore-forming stages and figured out the ore-forming thermodynamic parameters of each stage according to thermodynamic data. The first stage was the pyrite-early white chalcedony-like quartz stage, during which Eh values varied in the range of -0.5～＋ 0.3 V, implying a weak reduction environment, and sulfur fugacity should be higher than 10-23 ; the second stage was the ashgray chalcedony-like quartzpolymetallic sulfide stage, during which the ore-forming environment at low temperature was an intermediateacid （pH = 4） weakly reducing environment, the sulfur fugacity should be higher than 10-40 but not in excess of 10^0, and the lower limit of the sulfur fugacity decreased as compared with that of the first stage; the third stage was the carbonatequartz stage, during which the formation of the carbonate minerals foreboded the ending of the mineralization, the pH values of the metallogenic media changed gradually from acid （pH = 3） to intermediateacid （pH = 5）, ore-forming Eh values also showed transition from weak reduction （ - 0.5 V） to weak oxidation （ ＋ 0.3 V）, the lower limit of the sulfur fugacity varied around 10-23 and was not in excess of 10^0, and the oxygen fugacity varied around 10^-20. The data obtained bythe authors are of important reference value for the in-depth investigation of the hydrothermal ore-fomaing process.