中高盐度NaCl-H_2O包裹体的密度式和等容式及其应用

Density and Isochoric Formulae for NaCl-H_2O Inclusions with Medium and High Salinity and Their Applications

由于现有的盐水溶液热力学状态方程比较复杂,对于盐水包裹体使用很不方便。笔者在已推导的低盐水包裹体热力学公式基础上,根据实验数值,采用数学拟合法,得到中高盐度(≥23.3％)NaCl-H_2O溶液包裹体较精确的流体密度计算式:ρ(g/cm^3)=A+B·t_h+C·t_h^2(A=A_0+A_1·w+A_2·w^2;B=B_0+B_1·w+B_2·w^2;C=C_0+C_1·w+C_2·w^2)和包裹体等容式:p(×10~5Pa)=a+b·t+c·t^2。当测定出包裹体的均一温度(t_h,℃)和含盐度(w,％),代入密度式即可计算包裹体的流体密度。再找出此密度、盐度的等容式中参数(a、b、c),将这一等容式和其他公式联立,可求得包裹体的形成温度和压力。本文还列举了利用密度式和等容式计算的3个实例。

Considering that the existing thermodynamics state equations of salt solutions are very complex and inconvenient to be applied to salt-bearing fluid inclusions, the author has established more accurate density formulae: p(g/cm3)=A+B. th+C th2, where A=A0+A1 w+A2 w2;B = B0 + B1 w + B2 w2;C=C0+C1 w + C2 w2, and isochoric formulae : p( × 105 Pa) -a + bt + c t2 for NaCl-H2O-bearing fluid inclusions with medium and high salinity ( salinity > 2 3. 3%)by using the mathematical fitting method in conjunction with the experimental data in view of the established thermodynamics formulae for fluid inclusions with low salinity. Only by substituting the measured homogenization temperatures (th,℃) and salinities (w, wt%) into the density formula can one calculate the fluid density (p). The formation temperature and pressure for trapping the fluid inclusions can be worked out by uniting other formulae and using the isochoric formula given the parameters (a, b and c) for this density (p) and salinity (w). Last of all, three typical calculating examples are given based on those density and isochoric formulae in this paper.