Experimental Study of Mineral Solubility in Fluids of the Deep Crust and Upper Mantle

地球深部地壳和上地幔中的流体在广泛的地质过程中起着重要作用。它们改变了岩石成分，参与了地壳和地幔的融化，并调节了岩石的变形。它们改变岩石组成的能力在地球上表现突出？长期的成分演化导致了我们赖以生存的大陆地壳的形成。深层环境中流体的作用是导致大型火山融化的一个基本方面，火山的挥发性成分决定了火山的爆炸性，因此也决定了火山的危险性。通过控制岩石的变形，深层环境中的流体在深层缓慢滑动地震中也起着鲜为人知的作用，我们现在才开始了解这些地震的成因。该项目旨在通过实验表征水如何与深部地壳和上地幔中的矿物质相互作用和溶解的基本物理化学。建议在三个方面进行实验。第一种方法将为含水二氧化硅（在大多数地壳条件下最丰富的中性物质）的形成提供强有力的热力学约束。这项工作的第二个组成部分集中在碱性条件下的溶解硅。这是因为模型表明地壳和地幔流体的pH值在很大的P和t范围内是碱性的。该团队将扩展之前关于石英和长石在水盐溶液中的溶解度的实验，包括CaCl2和钙长石，这些之前没有研究过，但它们是了解深层流体的关键成分。所有实验都将涉及热液活塞-气缸方法，在必要条件下提供精确和准确的溶解度约束。这项工作将提供约束条件，有助于改进高压和高温下流体-岩石相互作用的新化学模型。

Fluids in Earth's deep crust and upper mantle play an important role in a wide range of geological processes. They change rock compositions, participate in crustal and mantle melting, and mediate how rocks deform. Their ability to change rock composition figures prominently in Earth?s long term compositional evolution that resulted in formation of the continental crust on which we live. The action of fluids in deep environments is a fundamental aspect of melting that leads to large volcanoes whose volatile content governs explosivity and therefore the hazards they pose. By controlling how rocks deform, fluids in deep settings also play a poorly understood role in deep, slow-slip earthquakes whose generation we are only now beginning to understand.This project aims to experimentally characterize the basic physical chemistry of how water interacts with and dissolves minerals in the deep crust and upper mantle. It is proposed to conduct experiments in three areas. The first will provide robust thermodynamic constraints on the speciation of aqueous silica, the most abundant neutral species at most crustal conditions. A second component of the work focuses on dissolved Si at alkaline conditions. This is because models suggest that the pH crustal and mantle fluids is alkaline over a wide range of P and T. Finally. the team will extend previous experiments on quartz and feldspar solubility in H2O-salt solutions to include CaCl2 and anorthite, which have not previously been studied but which are key ingredients to any understanding of deep fluids. All experiments will involve hydrothermal piston-cylinder methods which provide precise and accurate solubility constraints at the requisite conditions. The work will provide constraints that will help improve new models of the chemistry of fluid-rock interaction at high pressure and temperature.