The compositions of Fluids in and on the Earth

地球上和地球上的水促进了板块构造，控制了元素的重新分配，形成了矿藏，并决定了生命所必需的(痕量)元素的可用性。因此，了解这些流体的组成是至关重要的。不幸的是，直接采样和量化流体的机会很少，特别是在地球深处及其最早的历史上。然而，保存完好的矿物成分随处可见，取样环境为&GT；200公里深，可追溯到42亿年前。矿物存储着它们生长的流体的化学指纹，如果知道元素在矿物和流体之间的分布，这个指纹可以用来重建流体的成分。因此，矿物记录是一个有吸引力的信息来源，在这个研究计划中，我将建立一种从矿物组成重建流体组成的方法。这项研究将使用晶格应变理论，该理论将矿物结构中元素的大小和电荷错配与其分配系数联系起来，其中较大的错配限制了矿物对元素的吸收，导致分配系数较低。这一理论允许对分配的趋势进行建模，并开发元素分布的预测模型。在不同温度和压力下的分配实验将与计算机模拟相结合，以研究分配对变化条件的响应，以及这如何与矿物晶格的几何和弹性/电学性质的变化联系在一起。所产生的模型将应用于自然样品，以确定与金矿形成有关的流体的组成，了解元素在地球上的循环，并重建早期地球海洋的组成，生命是在其中发育的。事实上，这种方法适用于任何从流体中生长矿物的环境，因此也可以用于研究从废水处理到矿石选矿的工业过程。很少有其他技术能够提供关于地球深处和时间倒流的流体成分的信息，而且没有一项技术适用于这种方法可以覆盖的环境范围。

Water in and on the Earth facilitates plate tectonics, controls the redistribution of elements to make ore deposits and determines the availability of (trace) elements essential for life. Knowledge of the compositions of these fluids is therefore crucial. Unfortunately, opportunities to sample and quantify fluids directly are rare, espe- cially for sites deep in the Earth and for its earliest history. However, minerals with preserved compositions are readily available, sampling environments >200 km in depth and back to 4.2 billion years ago. Minerals store a chemical fingerprint of the fluid from which they grow, and if the distribution of elements between mineral and fluid is known, this fingerprint can be used to reconstruct the composition of the fluid. The mineral record is therefore an attractive source of information and in this research program I will establish a methodology to reconstruct fluid compositions from the composition of minerals. The research will use Lattice Strain Theory, which relates the misfit in size and charge of an element in the structure of a mineral to its partition coefficient, where a large misfit limits mineral uptake of the element resulting in a low partition coefficient. This theory allows for trends in partitioning to be modeled and for a predictive model of element distribution to be developed. Partitioning experiments at varying temperature and pressure will be combined with computer simulations to investigate the response of partitioning to changing conditions, and how this links to changes in the geometry and elastic/electric properties of the mineral lattice. The resulting model will be applied to natural samples to determine the compositions of fluids involved in formation of gold deposits, to understand the cycling of elements through the Earth, and to reconstruct the compositions of the Early Earth oceans in which life developed. In fact, this approach is applicable to any environment where minerals grow from a fluid and can therefore also be used to study industrial processes from wastewater treatment to ore mineral processing. Few other techniques are able to provide information on fluid compositions deep within the Earth and back in time, and none are applicable to the range of environments that can be covered by this approach.