Steady-state kinetics and equilibrium between ground water and granitic rock
Steady-state kinetics and equilibrium between ground water and granitic rock
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DOI：
10.1016/0016-7037(73)90270-6
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发表时间：
1973-12
影响因子：
5
通讯作者：
T. Pačes
中科院分区：
文献类型：
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作者：
T. Pačes
提出了钠长石溶蚀过程的假设，认为钠长石的溶蚀过程包括钠离子在钠长石表层与氢离子的交换以及钠长石表层残余阴离子晶格的结构崩塌。离子交换用扩散第一定律描述（D25°C= 3 × 10−22和1.5 × 10−20cm2sec−1atPCO2分别= 0和26.2 atm）。根据温度和pco2的变化，表面残余层的稳态厚度为n× 10 ~ 8ton× 10 ~ 5cm。连续地下水系统中钠水溶液随时间的增加用一个简单的指数方程来描述。该方程用于根据水样的化学成分数据估计地下水的渗透时间。各种地下水系统的可能时间从14天到3840天不等，并与地热和水力数据计算的渗透时间进行了比较。这两种估计大体上是一致的。花岗岩冷水中Al和Si的浓度受古老铝硅酸盐的化学平衡控制。铝硅酸盐作为无定形等电固体从地下水中析出。其化学组成由简化的化学计量公式[Al(OH)3](1−x)[SiO2]表示，并随溶液的pH值线性变化。Al、O和H原子在现场时效后趋于在三水铝石结构给出的固体中占据固定的位置。根据已发表的长石溶解实验和现场研究数据，估算出固体的溶解度积：logK=(1−x) ×log[Al3+] +xlog[H4SiO4]−(3−3x)log[H+] = 8.56−11.26x，其中为硅酸铝中二氧化硅的摩尔分数。
A hypothesis is presented that the dissolution of albite includes the exchange of sodium for hydrogen ion in a surface layer of the mineral and the structural collapse of the residual anionic lattice of the layer. The ion exchange is described by the first law of diffusion (D25°C= 3 × 10−22and 1.5 × 10−20cm2sec−1atPCO2= 0 and 26.2 atm, respectively). The surface residual layer reaches a steady-state thickness ranging fromn× 10−8ton× 10−5cm according to the temperature andPCO2. The increase in aqueous sodium with time in a continuous ground-water system is described by a simple exponential equation. The equation is used to estimate the percolation time of ground water from the data on the chemical composition of a water sample. The probable times range from 14 to 3840 days for various ground-water systems and are compared to the times of percolation calculated from the geothermal and hydraulic data. Both estimates are found to be in general agreement. The concentrations of Al and Si in cold water from granitic rocks are shown to be controlled by the chemical equilibrium with respect to an aged aluminosilicate. The aluminosilicate precipitates from ground water as an amorphous isoelectric solid. Its chemical composition is represented by a simplified stoichiometric formula [Al(OH)3](1−x)[SiO2]xand varies linearly with pH of the solution. The atoms of Al, O and H tend to occupy a fixed position in the solid given by the gibbsite structure upon aging in the field. The solubility product of the solid is estimated from the published data on experimental and field research into the dissolution of feldspars:logK= (1 −x) ×log[Al3+] +xlog[H4SiO4] − (3 − 3x)log[H+] = 8.56 − 11.26x, wherexis the molar fraction of silica in the aluminosilicate.