Hydrothermal properties of complex aqueous solutions, and applications to ore-forming systems

地质流体控制着地球内部的许多过程，推动化学反应，输送热量和物质，促进熔融和岩浆活动。现代分析方法表明，这些流体通常是含有高浓度各种溶质的复杂卤水。特别是在成矿环境中，复杂的卤水溶解和输送元素形成矿藏。然而，由于缺乏对这类流体性质的定量模型，涉及复杂的含盐流体的地球化学过程大多被定性地解释。因此，迫切需要开发模型来预测和定量模拟复杂卤水的物理和化学性质。 这项工作的目的首先是基于矿物中流体包裹体获得的数据，开发新的热力学模型来表征复杂地质卤水的成分和矿物溶解度。这项工作将涉及新的盐水热力学模型，这些模型将被内置到计算机程序中。这项工作还将涉及现场和实验室研究斑岩系统深层岩浆中脱气的流体，以及在贱金属矿床背景下海水蒸发产生的盐水。 这项工作将为研究人员提供工具，以探索不同环境下地质流体的组成，并将流体组成与热液蚀变和矿物降水联系起来。这项研究的实地部分将解决两个主要问题：岩浆结晶减弱阶段的流体如何演化，以及海水成分随时间的变化如何影响蒸发岩卤水的成分和成矿潜力。 这里描述的工作是新颖的，因为目前，流体性质仍然主要是用基于水-氯化钠的近似来解释的。这项工作将代表着在实现流体的稳健表征方面向前迈出的重要一步。实现这些模型的计算机程序将促进这些新方法的应用，以在许多环境中阐明真实流体的性质。应用这些新的方法来表征岩浆和盆地流体，将为了解在这些环境中起作用的物理和化学过程提供新的见解。这些结果将有利于加拿大，因为热液对经济矿藏的形成至关重要。这项研究将为了解这些流体的性质以及它们如何与岩石反应形成矿藏提供新的见解。因此，大体上，这项研究将提高我们对成矿基本控制因素的理解。

Geologic fluids control numerous processes within the Earth driving chemical reactions, transporting heat and material, and promoting melting and magmatism. Modern analytical methods reveal that these fluids are commonly complex brines with high concentrations of diverse solutes. In ore-forming settings in particular, complex brines dissolve and transport elements to form mineral deposits. However, geochemical processes involving complex, saline fluids are mostly interpreted qualitatively owing to the lack of quantitative models for the properties of such fluids. Thus, there is a critical need to develop models to predict and model quantitatively the physical and chemical properties of complex brines. The objective of this work is firstly to develop new thermodynamic models to characterize the compositions and mineral solubilities of complex, geologic brines based on data obtained from fluid inclusions in minerals tiny droplets of fluids trapped within minerals as they grow and secondly to apply these methods to analyze fluids from two major ore-forming settings. This work will involve new thermodynamic models for brines which will be built into computer programs. This work will also involve field- and laboratory-based studies of fluids degassed from magmas in the deep roots of porphyry systems, and of saline brines derived from seawater evaporation in the context of base-metal deposits. This work will provide researchers with the tools to explore the compositions of geologic fluids in diverse settings, and to relate fluid composition to hydrothermal alteration and mineral precipitation. The field-based portions of the study will address two major questions: How fluids evolve during the waning stages of magma crystallization, and how variations of seawater composition through time affect compositions and ore-forming potentials of evaporite-derived brines. The work described here is novel because at present, fluid properties are still mostly interpreted using approximations based on H2O-NaCl. This work will represent a major step forward in allowing robust characterization of fluids. Computer programs implementing these models will facilitate applications of these new methods to illuminating the properties of real fluids in many settings. The applications of these new approaches to characterizing magmatic and basinal fluids will provide new insights into the physical and chemical processes at work in these settings. These outcomes will be beneficial to Canada because hydrothermal fluids are crucial to the formation of economic mineral deposits. This research will provide new insights into the nature of these fluids and how they react with rocks to form mineral deposits. Thus, broadly, this research will improve our understanding of the fundamental controls on ore formation.