水岩作用是黑色页岩化学风化的重要途径,并与岩体矿物组分、工程性质及地质环境有着密切的联系。利用自制的流通实验装置对取自三江县团结电站附近的寒武系清溪组黑色页岩与富含溶解氧去离子水的化学反应进行试验模拟研究,并利用离子分析仪、电感耦合等离子体质谱仪对反应后溶液离子浓度进行分析,使用扫描电子显微镜观察反应前后岩样微观特征,结合岩样渗透系数的变化监测,对岩样中黄铁矿氧化动力学速率以及受黄铁矿氧化影响形成的酸性环境下硅元素释放速率进行计算分析。结果表明,黄铁矿氧化行为使得岩体渗透率降低约70%,在黑色页岩自身矿物化学组分和岩石物理性质的共同影响下,所含黄铁矿氧化速率与纯黄铁矿颗粒的氧化速率非常接近,同时黄铁矿氧化形成的酸性溶液可溶蚀岩体中石英和伊利石,由于两者含量未能精确测定,因此所测得硅元素释放速率仅表示两者溶解的总反应速率。
Being an important form of chemical weathering of black shales,the water-rock interaction is closely related to the mineral compositions,engineering properties and geological environments. A China-designed flow-through experiment was used to study the oxidation kinetic behavior of pyrite contained in black shale during the water-rock interaction. The ion concentrations of outflow solutions were measured by the ion analyzer and inductively coupled plasma mass spectrometry. The micro-features of the rock sample before and after the experiment were observed with a scanning electron microscope. Combined with the changes of rock permeability,the kinetic rate of pyrite oxidation and Si release in acid water were examined. The results obtained by the authors indicated that the behavior of pyrite oxidation caused the decrease of the rock permeability by 70%,and the oxidizing reaction coefficient of pyrite embedded in rocks under the effects of mineralogical and chemical compositions and petrophysical properties of the black shale was consistent with that of free pyrite grains reported by previous researchers. Besides,the quartz and illite were dissolved in the acidic solution produced by pyrite oxidation. Due to their uncertain content,the release rate of Si only represented their total dissolution rate.