Supercritical fluids in rock–H2O systems have been proposed to be important agents of mass transfer in subduction zone environments. New experimental studies were conducted on the simple model granite system NaAlSi3O8 (Ab)–H2O in order to investigate phase relations and to develop the thermodynamic mixing properties between aqueous fluid (a.k.a. vapor, V) and silicate melt (a.k.a. liquid, L) at pressures (P) and temperatures (T) approaching those of critical mixing. We established liquidus and solvus phase relations by analyzing the quenched run products from piston–cylinder experiments over a range of P-T-XH2O\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$P - T - X_{{{\text{H}}_{2} {\text{O}}}}$$\end{document} conditions from 1.0 to 1.7 GPa, 630–1060 °C and 4–92 wt% H2O. Equations for the critical curve, solidus temperatures, albite solubility at the solidus, and vapor-saturated solidus H2O content were formulated as functions of P-T-XH2O\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$P - T - X_{{{\text{H}}_{2} {\text{O}}}}$$\end{document}. We constructed a subregular solution model to describe the solvus curves using P and T dependent Margules coefficients (WH2O\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$W_{{{\text{H}}_{2} {\text{O}}}}$$\end{document} and WAb\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$W_{\text{Ab}}$$\end{document}). Activities of H2O and Ab (aH2O\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$a_{{{\text{H}}_{2} {\text{O}}}}$$\end{document} and aAb\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$a_{\text{Ab}}$$\end{document}) could be formulated using only the input at the solidus and the critical point at each pressure because of the nearly linear dependence of the parameters on T. The solvus curves were confirmed independently by means of criteria established for classification of quenched products as L, L + V, or V and are in excellent agreement with the compositions that can be calculated using the Margules coefficients. At 1.6 GPa, the H2O content at the vapor-saturated solidus is 44.5 ± 5.5 wt% and the solubility of albite at the solidus is 42.95 ± 0.99 wt%, indicating the imminent intersection of the two curves and thus a stable critical endpoint at some slightly higher pressure. We constrain the critical endpoint at 1.63 ± 0.02 GPa, 659 ± 5 °C, and a composition of ~ 44.7 wt% H2O based on the intersections of the pressure dependent solidus curves with the critical curve, the pressure dependent albite solubility curve with the vapor-saturated solidus curve. The 1.7 GPa experiments showed no evidence for liquid–vapor immiscibility across a wide range of compositions and temperatures (4–80 wt% H2O and 630–1050 °C, and furthermore, that low albite is stable in the presence of the supercritical fluid near the breakdown of albite to jadeite and quartz. These results provide a comprehensive account of the solution properties of subcritical and supercritical fluids in this model granite system at temperatures and pressures corresponding to the deep-crust regions of granite magma generation.

中文翻译：

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高温高压下 NaAlSi3O8-H2O 体系中相关系的实验研究：液相线关系、液-汽混合以及深部地壳-上地幔条件下的临界现象

岩石-H2O 系统中的超临界流体被认为是俯冲带环境中传质的重要媒介。对简单模型花岗岩系统 NaAlSi3O8 (Ab)–H2O 进行了新的实验研究，以研究相关系并在压力下开发水性流体（又名蒸汽，V）和硅酸盐熔体（又名液体，L）之间的热力学混合特性(P) 和温度 (T) 接近临界混合。我们通过分析一系列 PT-XH2O\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage {amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$P - T - X_{{{\text{H}}}_ {2} {\text{O}}}}$$\end{document} 条件从 1.0 到 1.7 GPa，630–1060 °C 和 4–92 wt% H2O。临界曲线方程、固相线温度、固相线钠长石溶解度、溶解曲线通过为淬火产物分类为 L、L + V 或 V 建立的标准独立确认，并且与可以使用 Margules 系数计算的成分非常一致。在 1.6 GPa 时，蒸汽饱和固相线上的 H2O 含量为 44.5 ± 5.5 wt%，钠长石在固相线上的溶解度为 42.95 ± 0.99 wt%，表明两条曲线即将相交，因此在某些情况下是一个稳定的临界终点压力稍高。我们将临界终点限制在 1.63 ± 0.02 GPa、659 ± 5 °C 和 ~ 44.7 wt% H2O 的组成，基于压力相关固相线曲线与临界曲线、压力相关钠长石溶解度曲线与蒸汽的交点- 饱和固线曲线。1.