Experimental and Theoretical Determination of Solubilities of Rock-Forming Minerals

本项目将继续进行铝硅酸盐矿物在地壳条件下平衡溶解度的测定。 在最近的实验测量纯H2O，H2O-NaCl和H2O-CaCl 2溶液中的溶解度的基础上，将研究H2O-HCl和H2O-NaCl-HCl溶液中铝的形态。将在高温（400 o至650 o C）和高压（高达3 kbar）下，在酸溶液和盐水流体（0.05、0.1、0.5、1.0摩尔浓度的盐酸和氯化钠）中测量和解释刚玉和红柱石加石英。 该奖项支持的实验将涉及在高压和高温下用独特设计的热液装置提取流体样品，然后确定所有挥发性和非挥发性物质的浓度。通过一组现代分析技术，包括直流等离子体发射分光光度计，测量流体的挥发性成分。测量的理论分析的一个重要部分是活度系数在确定平衡时，必须考虑这些溶液中常见的中性物质。 在Al_2 O-SiO_2-H_2 O-NaCl-HCl体系中，建立了超临界温度和压力下Al形态与pH和离子强度的函数关系模型，并确定了Na+Al和可能的Na+Al+Si复合物在溶液中的含量。 拟议的实验应限制在地壳变质过程中铝可从中迁移和含铝相沉淀的可能的溶液成分。该项目将培训1至2名研究生，使他们能够在现代湿化学和热液实验室中操作仪器。PI将在研究生课程中使用本项目中开发的概念，并将其纳入他正在开发的本科/研究生教科书中。

Abstract This project will continue an experimental program of determining the equilibrium solubilities of Al-silicate minerals at crustal conditions. Aluminum speciation in H2O-HCl and H2O-NaCl-HCl solutions will be investigated building on recent experiments measuring corundum solubilities in pure H2O, H2O-NaCl and H2O-CaCl2 solutions. Corundum and andalusite plus quartz, at elevated temperatures (400o to 650o C) and pressures (up to 3 kbar) in acid solutions and aqueous salt fluids (0.05, 0.1, 0.5, 1.0 molal HCl and NaCl) will be measured and interpreted. The experiments supported by this award will involve extracting fluid samples while they are at high pressure and temperature with a uniquely designed hydrothermal apparatus and then determining the concentration of all volatile and non-volatile constituents of the fluid through a battery of modern analytical techniques including a direct current plasma emission spectrophotometer.An important part of the theoretical analysis of the measurements is that activity coefficients of neutral species, which are common in these solutions, must be considered when determining the equilibrium. Hopefully a better model of Al speciation as a function of pH and ionic strength at supercritical pressure and temperature can be constructed in the Al2O-SiO2-H2O-NaCl-HCl system and the extent of Na+Al and possible Na+Al+Si complexes in solution determined. The proposed experiments should put limits on the possible solution compositions from which aluminum can be transported and aluminum bearing phases precipitate during metamorphism of the earth's crust.The project will undertake the training of 1 to 2 graduate students giving them the ability to run the instruments in a modern wet-chemical and hydrothermal laboratory. The PI will use concepts developed in this project in a graduate level course and include them in an undergraduate/graduate textbook he is developing.