The compositions of Fluids in and on the Earth

地球内部和表面的水促进板块构造，控制元素的重新分布以形成矿床，并决定生命所必需的（微量）元素的可用性。因此，了解这些流体的成分至关重要。不幸的是，直接对流体进行采样和定量的机会很少，特别是对于地球深处的遗址及其最早的历史。然而，具有保存成分的矿物很容易获得，采样环境深度>200公里，可追溯到42亿年前。矿物存储了它们生长的流体的化学指纹，如果已知矿物和流体之间的元素分布，则该指纹可用于重建流体的组成。因此，矿物记录是一个有吸引力的信息来源，在这项研究计划中，我将建立一种方法来重建流体成分的矿物组成。该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与其分配系数相关联，其中大的失配限制了元素的矿物吸收，导致分配系数低。这一理论允许在分区的趋势进行建模，并为元素分布的预测模型开发。在不同温度和压力下的分区实验将与计算机模拟相结合，以研究分区对变化条件的响应，以及这如何与矿物晶格的几何形状和弹性/电特性的变化联系起来。由此产生的模型将应用于自然样本，以确定金矿形成中所涉及的流体成分，了解地球上元素的循环，并重建生命发展的早期地球海洋的成分。事实上，这种方法适用于矿物从流体中生长的任何环境，因此也可用于研究从废水处理到矿石矿物加工的工业过程。很少有其他技术能够提供有关地球深处和过去的流体成分的信息，而且没有一种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.